WO2024203857A1 - Control device, discharge device, refrigeration cycle device, control method, and program - Google Patents

Abstract

Provided are a control device, a discharge device, a refrigeration cycle device, a control method, and a program with which it is possible to reduce the possibility of occurrence of an abnormal phenomenon caused by energy remaining when a compressor is stopped and to improve the suppression of disproportionation reaction. A control device (3) controls the compressor (4) of a refrigeration cycle circuit in which a working medium circulates. The control device (3) comprises: a drive circuit (31) that drives the compressor (4); and a discharge device (36) that is connected between the drive circuit (31) and the compressor (4) and is capable of switching between a first state in which connection lines (Lu, Lv, Lw) are separated from a reference potential and a second state in which the connection lines (Lu, Lv, Lw) are connected to the reference potential.

Description

CONTROL DEVICE, DISINFECTION DEVICE, REFRIGERATION CYCLE DEVICE, CONTROL METHOD, AND PROGRAM

This disclosure relates to a control device, a discharge device, a refrigeration cycle device, a control method, and a program.

Traditionally, R410A has been widely used as a working fluid (heat medium, refrigerant) for refrigeration cycle equipment. However, the global warming potential (GWP) of R410A is high at 2090. Therefore, from the perspective of preventing global warming, research and development is being conducted on working fluids with lower GWP. Patent Document 1 discloses 1,1,2-trifluoroethylene (HFO1123) as a working fluid with a lower GWP than R410A. Patent Document 2 discloses 1,2-difluoroethylene (HFO1132) as a working fluid with a lower GWP than R410A.

HFO1123 and HFO1132 have a smaller GWP than R410A, but this makes them less stable than R410A. For example, the generation of radicals can cause disproportionation reactions of HFO1123 or HFO1132, which can cause HFO1123 and HFO1132 to change into different compounds.

Patent document 3 states that "disproportionation reactions occur when high energy is added to the refrigerant in an environment where the refrigerant is excessively high temperature and pressure (particularly inside a compressor), or when excessive collisions between the refrigerant molecules and electrons occur due to discharges such as layer shorts."

Patent document 3 states, "This disclosure prevents high energy from being added to the refrigerant in the compressor, or prevents excessive collisions between refrigerant molecules and electrons in the discharge space, thereby suppressing the occurrence of disproportionation reactions. This provides a highly reliable refrigeration cycle device that uses a working medium containing an ethylene-based fluorohydrocarbon having a double bond."

The refrigeration cycle apparatus described in Patent Document 3 has a protection device that at least one of stops the supply of power to the compressor and reduces the rotation speed of the compressor in at least one of the following cases: when the current value of the input current to the compressor motor exceeds a first predetermined value that is set to be three times or more the maximum current value during normal operation other than at the start of the compressor; when the current value of the input current to the compressor motor exceeds a ^second predetermined value that is set to be twice or more the current value at the start of the compressor; and when the number of discharge electrons in the discharge space, calculated based on the amount of change in the current value of the input current to the compressor motor, exceeds a third predetermined value that is set to be 1.0 x 1019 electrons/second or more.

International Publication No. 2012/157764 International Publication No. 2012/157765 International Publication No. 2019/172008

The refrigeration cycle device disclosed in Patent Document 1 detects signs of a disproportionation reaction using the current value of the input current to the compressor motor, and suppresses the disproportionation reaction by using a protective device to either stop the power supply to the compressor or reduce the compressor rotation speed.

The present disclosure provides a control device, discharge device, refrigeration cycle device, control method, and program that can reduce the possibility of abnormal phenomena occurring due to residual energy when the compressor is stopped, and enable improved suppression of disproportionation reactions.

A control device according to one aspect of the present disclosure controls a compressor of a refrigeration cycle circuit in which a working medium circulates. The control device includes a drive circuit that drives the compressor, and a discharge device that can switch between a first state in which a connection line between the drive circuit and the compressor is separated from a reference potential, and a second state in which the connection line is connected to the reference potential.

The discharge device according to one aspect of the present disclosure is connected to a connection line between a compressor of a refrigeration cycle circuit in which a working medium circulates and a drive circuit that drives the compressor, and is configured to be switchable between a first state in which the connection line is isolated from a reference potential and a second state in which the connection line is connected to the reference potential.

The refrigeration cycle device according to one aspect of the present disclosure includes the above-mentioned control device and the above-mentioned refrigeration cycle circuit.

The control method according to one aspect of the present disclosure is a control method executed by a control device that controls a compressor of a refrigeration cycle circuit in which a working medium circulates. The control device includes a drive circuit that drives the compressor, and a discharge device that can switch between a first state in which a connection line between the drive circuit and the compressor is separated from a reference potential, and a second state in which the connection line is connected to the reference potential. The control method stops the operation of the drive circuit and switches the discharge device to the second state in response to detection of an abnormality in at least one of the compressor and the drive circuit.

The program according to one aspect of the present disclosure is a program executed by a computer system provided in a control device that controls a compressor of a refrigeration cycle circuit in which a working medium circulates. The control device includes a drive circuit that drives the compressor, and a discharge device that can switch between a first state in which a connection line between the drive circuit and the compressor is separated from a reference potential, and a second state in which the connection line is connected to the reference potential. The program causes the computer system to stop operation of the drive circuit and switch the discharge device to the second state in response to detection of an abnormality in at least one of the compressor and the drive circuit.

The aspects of the present disclosure can reduce the possibility of abnormal phenomena occurring due to residual energy when the compressor is stopped, and enable improved suppression of disproportionation reactions.

Block diagram of a refrigeration cycle device according to an embodiment. 1 is a schematic diagram of a compressor and a control device of a refrigeration cycle device according to an embodiment; Schematic circuit diagram of a discharge device of a refrigeration cycle device according to an embodiment. 1 is a waveform diagram of a voltage of a smoothing circuit of a drive circuit of a control device according to an embodiment of the present invention; 1 is a part of a flowchart of the operation of a control device according to an embodiment. 1 is a part of a flowchart of the operation of a control device according to an embodiment. 1 is a part of a flowchart of the operation of a control device according to an embodiment. 1 is a part of a flowchart of the operation of a control device according to an embodiment. 1 is a part of a flowchart of the operation of a control device according to an embodiment. 1 is a part of a flowchart of the operation of a control device according to an embodiment. Schematic diagram of a control device according to a modified example.

1. Embodiment
Hereinafter, embodiments of the present disclosure will be described with reference to the drawings in some cases. However, the following embodiments are examples for explaining the present disclosure, and are not intended to limit the present disclosure to the following contents (e.g., the shape, dimensions, arrangement, etc. of each component). Positional relationships such as up, down, left, and right are based on the positional relationships shown in the drawings unless otherwise specified. Each figure described in the following embodiments is a schematic diagram, and the size and thickness ratios of each component in each figure do not necessarily reflect the actual dimensional ratio. In addition, the dimensional ratios of each element are not limited to the ratios shown in the drawings.

In the following description, when it is necessary to distinguish between multiple components, prefixes such as "first" and "second" are added to the names of the components. However, when the components can be distinguished from one another by the reference symbols attached to them, the prefixes such as "first" and "second" may be omitted in consideration of readability of the text.

1.1 Configuration
1 is a block diagram of a refrigeration cycle apparatus 1 according to the present embodiment. The refrigeration cycle apparatus 1 constitutes, for example, an air conditioner capable of cooling operation and heating operation. The refrigeration cycle apparatus 1 includes a refrigeration cycle circuit 2 and a control device 3.

The refrigeration cycle circuit 2 constitutes a flow path through which the working medium circulates. In this embodiment, the working medium contains an ethylene-based fluoroolefin as a refrigerant component. The ethylene-based fluoroolefin may be an ethylene-based fluoroolefin that undergoes a disproportionation reaction. Examples of the ethylene-based fluoroolefin that undergoes a disproportionation reaction include 1,1,2-trifluoroethylene (HFO1123), trans-1,2-difluoroethylene (HFO1132(E)), cis-1,2-difluoroethylene (HFO-1132(Z)), 1,1-difluoroethylene (HFO-1132a), tetrafluoroethylene (CF ₂ ═CF ₂ , FO1114), and monofluoroethylene (HFO-1141).

The working medium may contain multiple types of refrigerant components. The working medium may contain an ethylene-based fluoroolefin as a main refrigerant component and a compound other than an ethylene-based fluoroolefin as a secondary refrigerant component. Examples of secondary refrigerant components include hydrofluorocarbons (HFCs), hydrofluoroolefins (HFOs), saturated hydrocarbons, carbon dioxide, etc. Examples of hydrofluorocarbons (HFCs) include difluoromethane, difluoroethane, trifluoroethane, tetrafluoroethane, pentafluoroethane, pentafluorobutane, heptafluorocyclopentane, etc. Examples of hydrofluoroolefins (HFOs) include monofluoropropene, trifluoropropene, tetrafluoropropene, pentafluoropropene, hexafluorobutene, etc. Examples of saturated hydrocarbons include ethane, n-propane, cyclopropane, n-butane, cyclobutane, isobutane (2-methylpropane), methylcyclopropane, n-pentane, isopentane (2-methylbutane), neopentane (2,2-dimethylpropane), methylcyclobutane, etc.

The working fluid may further contain a disproportionation inhibitor that suppresses the disproportionation reaction of the ethylene-based fluoroolefin. Examples of the disproportionation inhibitor include saturated hydrocarbons or haloalkanes. Examples of saturated hydrocarbons include ethane, n-propane, cyclopropane, n-butane, cyclobutane, isobutane (2-methylpropane), methylcyclopropane, n-pentane, isopentane (2-methylbutane), neopentane (2,2-dimethylpropane), methylcyclobutane, and the like. In the above examples, n-propane is preferred. Examples of the haloalkane include haloalkanes having 1 or 2 carbon atoms. Examples of haloalkanes having _one carbon atom (i.e., halomethanes) include (mono)iodomethane ( _CH3I ), diiodomethane ( _CH2I2 ), dibromomethane ( _CH2Br2 ), bromomethane (CH3Br), dichloromethane ( _CH2Cl2 ) _, chloroiodomethane ( _CH2ClI ), _{dibromochloromethane} (CHBr2Cl), tetraiodomethane ( _CI4 ), carbon tetrabromide ( _CBr4 ), bromotrichloromethane ( _{CBrCl3 )} , _{dibromodichloromethane} (CBr2Cl2), tribromofluoromethane ( _CBr3F ), _{fluorodiiodomethane} (CHFI2) _{, difluorodiiodomethane} ( _CF2I2 ), dibromodifluoromethane ( _{CBr2F2 ) .} ), trifluoroiodomethane (CF ₃ I), difluoroiodomethane (CHF ₂ I), etc. Examples of haloalkanes having 2 carbon atoms (i.e., haloethanes) include 1,1,1-trifluoro-2-iodoethane (CF ₃ CH 2 I), monoiodoethane (CH ₃ CH ₂ I), monobromoethane (CH ₃ CH _{2 Br} ), 1,1,1-triiodoethane (CH ₃ CI ₃ ), etc. The working fluid may contain one or more types of haloalkanes having 1 or 2 carbon atoms. In other words, only one type of haloalkane having 1 or 2 carbon atoms may be used, or two or more types may be used in appropriate combination.

Here, an experiment was conducted to verify whether or not a disproportionation reaction occurs using a working fluid containing 1,1,2-trifluoroethylene (HFO1123). In the disproportionation reaction experiment, a pressure sensor (GC61 manufactured by Nagano Keiki Co., Ltd.) was attached to a sealed pressure vessel (stainless steel sealed vessel, internal volume 50 mL) to measure the internal pressure in the pressure vessel, a thermocouple (PL thermocouple ground PL-18-K-A 4-T manufactured by Conax Technologies) to measure the internal temperature in the pressure vessel, and a discharge device to generate a discharge in the pressure vessel. In addition, a gas cylinder of 1,1,2-trifluoroethylene was connected so that the pressure could be adjusted. A mantle heater was installed to heat the entire pressure vessel, and a ribbon heater (flexible ribbon heater 1 m, 200 W manufactured by Tokyo Institute of Technology Co., Ltd.) was installed to heat the piping as well. This constructed an experimental system for the disproportionation reaction.

Table 1 below shows whether or not a disproportionation reaction occurs when the working medium is 1,1,2-trifluoroethylene alone, a mixed gas adjusted to have a 1,1,2-trifluoroethylene content of 80 mass% and an n-propane content of 20 mass%, a mixed gas adjusted to have a 1,1,2-trifluoroethylene content of 91.5 mass%, an n-propane content of 7.5 mass%, and a difluoroiodomethane content of 1.0 mass%, and a mixed gas adjusted to have a 1,1,2-trifluoroethylene content of 69.5 mass%, a difluoromethane content of 22 mass%, an n-propane content of 7.5 mass%, and a difluoroiodomethane content of 1.0 mass%. The pressure was adjusted to 2 MPa in Examples 1 and 2, and 6 MPa in Examples 3 to 5. The stored energy in Table 1 is electrostatic energy stored in a capacitor section installed inside the discharge device. The number of discharges is the number of times discharged at regular intervals under the conditions in question, and if a disproportionation reaction was observed after that number of discharges, the disproportionation reaction was recorded as "Yes," and if no disproportionation reaction was observed, it was recorded as "No."

As can be seen from Table 1, no disproportionation reaction was observed in Example 1. Therefore, disproportionation reactions do not occur due to minor discharges with small stored energy. When the stored energy was large, as shown in Example 2 in Table 1, a disproportionation reaction was observed after two consecutive discharges. Therefore, the presence or absence of a disproportionation reaction depends on the amount of stored energy, i.e., the amount of energy consumed for discharge. This shows that in order to suppress disproportionation reactions, it is preferable to reduce the energy of the discharge that flows instantaneously for periods of microseconds to sub-milliseconds, which are generally seen in discharge phenomena.

From Table 1, in Example 3, no disproportionation reaction was observed in the working medium of a mixed gas containing n-propane as a disproportionation inhibitor. Example 3 uses a larger stored energy than Example 2, in which disproportionation was observed in 1,1,2-trifluoroethylene alone. Therefore, it was confirmed that in a working medium containing n-propane as a disproportionation inhibitor, that is, even when the stored energy is increased by the disproportionation inhibitor, the possibility of a disproportionation reaction occurring in a small, minor discharge is extremely low. This shows that in order to suppress disproportionation reactions in a working medium of a mixed gas containing a disproportionation inhibitor, it is preferable to keep the discharge in a minor state, that is, to detect it early and suppress the disproportionation reaction.

From Table 1, in Example 4, no disproportionation reaction was observed in the working medium of a mixed gas containing n-propane and difluoroiodomethane as disproportionation inhibitors. Example 4 uses a larger stored energy than Example 2, in which disproportionation was observed in 1,1,2-trifluoroethylene alone. Therefore, it was confirmed that in a working medium containing difluoroiodomethane as a disproportionation inhibitor other than n-propane, that is, in the case where the stored energy is increased by two or more disproportionation inhibitors, the possibility of a disproportionation reaction occurring in a small, minor discharge is extremely low. This shows that in order to suppress a disproportionation reaction in a working medium of a mixed gas containing two or more disproportionation inhibitors, it is preferable to keep the discharge in a minor state, that is, to detect it early and suppress the disproportionation reaction.

From Table 1, in Example 5, no disproportionation reaction was confirmed in the working medium of a mixed gas containing difluoromethane as a disproportionation inhibitor different from n-propane and difluoroiodomethane as a secondary refrigerant component. Example 5 uses a larger stored energy than Example 2, in which disproportionation was confirmed in 1,1,2-trifluoroethylene alone. Therefore, it was confirmed that the stored energy is increased by two or more disproportionation inhibitors, and that even in a working medium containing a secondary refrigerant component that does not cause disproportionation, the possibility of a disproportionation reaction occurring in a small, minor discharge is extremely low. This shows that in order to suppress a disproportionation reaction in a working medium of a mixed gas containing two or more disproportionation inhibitors and one or more secondary refrigerants, it is preferable to keep the discharge in a minor state, that is, to detect it early and suppress the disproportionation reaction.

After extensive research into the mechanism of disproportionation reactions, the inventors have found that the decomposition of ethylene-based fluoroolefins proceeds along an almost common reaction pathway, that the radical species generated are the same, with only the composition changing, and that the thermal decomposition temperatures are almost the same. In other words, even with ethylene-based fluoroolefins other than 1,1,2-trifluoroethylene, a disproportionation reaction does not occur if a small amount of radicals are generated by a slight discharge and this occurs intermittently multiple times, but the disproportionation reaction proceeds only when a large amount of radicals are generated by a large-energy discharge.

The refrigeration cycle circuit 2 includes a compressor 4, a first heat exchanger 5, an expansion valve 6, a second heat exchanger 7, and a four-way valve 8.

The refrigeration cycle device 1 includes an outdoor unit 1a and an indoor unit 1b. The outdoor unit 1a includes a control device 3, a compressor 4, a first heat exchanger 5, an expansion valve 6, and a four-way valve 8. The outdoor unit 1a further includes a first blower 5a for promoting heat exchange in the first heat exchanger 5. The indoor unit 1b includes a second heat exchanger 7. The indoor unit 1b further includes a second blower 7a for promoting heat exchange in the second heat exchanger 7.

In the refrigeration cycle circuit 2, the compressor 4 compresses the working medium to increase the pressure of the working medium. The compressor 4 will be described in detail later. The first heat exchanger 5 and the second heat exchanger 7 exchange heat between the working medium circulating through the refrigeration cycle circuit 2 and external air (e.g., outside air or room air). The expansion valve 6 adjusts the pressure (evaporation pressure) of the working medium and the flow rate of the working medium. The four-way valve 8 switches the direction of the working medium circulating through the refrigeration cycle circuit 2 between a first direction corresponding to cooling operation and a second direction corresponding to heating operation.

In this embodiment, the first direction is the direction in which the working medium circulates through the refrigeration cycle circuit 2, in the order of the compressor 4, the first heat exchanger 5, the expansion valve 6, and the second heat exchanger 7, as shown by the solid arrow A1 in Figure 1.

In cooling operation, the compressor 4 compresses and discharges the gaseous working medium, which is then sent to the first heat exchanger 5 via the four-way valve 8. The first heat exchanger 5 exchanges heat between the outside air and the gaseous working medium, causing the gaseous working medium to condense and become liquefied. The liquid working medium is decompressed by the expansion valve 6 and sent to the second heat exchanger 7. In the second heat exchanger 7, heat exchange occurs between the liquid working medium and the indoor air, causing the gaseous working medium to evaporate and become a gaseous working medium. The gaseous working medium returns to the compressor 4 via the four-way valve 8. In cooling operation, the first heat exchanger 5 functions as a condenser, and the second heat exchanger 7 functions as an evaporator. Therefore, during cooling, the indoor unit 1b blows air cooled by heat exchange in the second heat exchanger 7 into the room.

In this embodiment, the second direction is the direction in which the working medium circulates through the refrigeration cycle circuit 2, in the order of the compressor 4, the second heat exchanger 7, the expansion valve 6, and the first heat exchanger 5, as shown by the dashed arrow A2 in Figure 1.

In heating operation, the compressor 4 compresses and discharges the gaseous working medium, which is then sent to the second heat exchanger 7 via the four-way valve 8. The second heat exchanger 7 exchanges heat between the indoor air and the gaseous working medium, causing the gaseous working medium to condense and become liquefied. The liquid working medium is decompressed by the expansion valve 6 and sent to the first heat exchanger 5. In the first heat exchanger 5, heat exchange occurs between the liquid working medium and the outside air, causing the gaseous working medium to evaporate and become a gaseous working medium. The gaseous working medium returns to the compressor 4 via the four-way valve 8. In heating operation, the first heat exchanger 5 functions as an evaporator, and the second heat exchanger 7 functions as a condenser. Therefore, during heating, the indoor unit 1b blows air warmed by heat exchange in the second heat exchanger 7 into the room.

The control device 3 controls the compressor 4 of the refrigeration cycle circuit 2. Figure 2 is a schematic diagram of the compressor 4 and the control device 3.

The compressor 4 is, for example, a hermetic compressor. The compressor 4 may be of a rotary type, a scroll type, or any other known type. The compressor 4 includes a hermetic container 40, a compression mechanism 41, and an electric motor 42.

The sealed container 40 forms a flow path for the working medium 20. The sealed container 40 has a suction pipe 401 and a discharge pipe 402. The working medium 20 is sucked into the sealed container 40 from the suction pipe 401, compressed by the compression mechanism 41, and then discharged from the discharge pipe 402 to the outside of the sealed container 40. The inside of the sealed container 40 is filled with high-temperature, high-pressure working medium 20 and lubricating oil. The bottom of the sealed container 40 forms an oil storage section that stores a mixture of the working medium 20 and lubricating oil.

The compression mechanism 41 is located inside the sealed container 40 and compresses the working medium. The compression mechanism 41 may have a conventionally known configuration. The compression mechanism 41 has, for example, a cylinder that forms a compression chamber, a rolling piston that is disposed in the compression chamber inside the cylinder, and a crankshaft that is connected to the rolling piston.

The electric motor 42 is located inside the sealed container 40 and operates the compression mechanism 41. The electric motor 42 is, for example, a brushless motor (three-phase brushless motor). The electric motor 42 includes, for example, a rotor fixed to the crankshaft of the compression mechanism 41 and a stator provided around the rotor. The stator is, for example, configured by concentrating or dispersing a stator winding (magnet wire, etc.) around a stator core (electromagnetic steel plate, etc.) with an insulating material such as insulating paper interposed between the stator winding. The stator winding is covered with an insulating material. Examples of insulating materials include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), aramid polymer, polyphenylene sulfide (PPS), polytetrafluoroethylene (PTFE), etc.

The compressor 4 may be equipped with an accumulator to prevent liquid compression in the compression chamber of the compression mechanism 41. The accumulator separates the working medium into a gaseous working medium and a liquid working medium, and guides only the gaseous working medium from the suction pipe 401 into the inside of the sealed container 40.

The control device 3 includes a drive circuit 31, a state detection circuit 32, a first protection device 33, a second protection device 34, a control circuit 35, and a discharge device 36.

The drive circuit 31 drives the electric motor 42 based on the input power from the power source 10. In this embodiment, the power source 10 is an AC power source, and the input power is AC power. The drive circuit 31 includes a converter circuit 311 and an inverter circuit 312.

The converter circuit 311 outputs DC output power based on the input power from the power source 10 so that the voltage becomes a first voltage. In other words, the converter circuit 311 converts the input power into DC output power so that the voltage of the DC output power becomes the first voltage. The first voltage corresponds to the rated voltage of the drive circuit 31.

The converter circuit 311 includes a rectifier circuit 311a and a smoothing circuit 311b.

The rectifier circuit 311a is a diode bridge composed of multiple diodes D1 to D4. The power source 10 is connected between the input terminals of the rectifier circuit 311a (the connection point of diodes D1, D2, and the connection point of diodes D3, D4), and the smoothing circuit 311b is connected between the output terminals of the rectifier circuit 311a (the connection point of diodes D1, D3, and the connection point of diodes D2, D4).

The smoothing circuit 311b smoothes and outputs the voltage between the output terminals of the rectifier circuit 311a. The smoothing circuit 311b sets the voltage of the DC output power to a first voltage. The smoothing circuit 311b includes a series circuit of an inductor L1 and smoothing capacitors C1 and C2. In the smoothing circuit 311b, the connection point between the inductor L1 and the smoothing capacitor C1 is the first output point P1 that outputs a voltage corresponding to the first voltage. In the smoothing circuit 311b, the connection point between the connection point of the diodes D2 and D4 and the smoothing capacitor C2 is the second output point P2 that outputs a voltage lower than the voltage at the first output point P1. In the smoothing circuit 311b, the connection point between the smoothing capacitor C1 and the smoothing capacitor C2 is the third output point P3 that outputs a voltage between the voltage at the first output point P1 and the voltage at the second output point P2. In the relationship between the first output point P1, the second output point P2, and the third output point P3, the first output point P1 is a high voltage point, the second output point P2 is a low voltage point, and the third output point P3 is an intermediate voltage point. In the smoothing circuit 311b, the smoothing capacitors C1 and C2 have the same capacitance. Therefore, the voltage between the voltage at the first output point P1 and the voltage at the third output point P3 is equal to the voltage between the voltage at the second output point P2 and the voltage at the third output point P3. If the voltage between the first output point P1 and the second output point P2 (which corresponds to the first voltage) is E, the voltage between the first output point P1 and the third output point P3 is E/2, and similarly, the voltage between the second output point P2 and the third output point P3 is E/2. This allows the drive circuit 31 to provide five levels of voltage: E, E/2, 0, -E/2, and -E.

The inverter circuit 312 outputs AC output power to the motor 42 based on the DC output power from the converter circuit 311. In this embodiment, the AC output power is three-phase AC power. The inverter circuit 312 includes a plurality of semiconductor switching elements U1 to U4, V1 to V4, and W1 to W4. The semiconductor switching elements U1 to U4, V1 to V4, and W1 to W4 are, for example, transistors.

The semiconductor switching elements U1 to U4, V1 to V4, and W1 to W4 each form a series circuit and are connected between the first output point P1 and the second output point P2.

The connection point of the semiconductor switching elements U1 and U2, the connection point of the semiconductor switching elements V1 and V2, and the connection point of the semiconductor switching elements W1 and W2 are connected to the third output point P3 via diodes D5, D7, and D9, respectively.

The anodes of diodes D5, D7, and D9 are connected to the third output point P3, and the cathodes of diodes D5, D7, and D9 are connected to the connection point of semiconductor switching elements U1 and U2, the connection point of semiconductor switching elements V1 and V2, and the connection point of semiconductor switching elements W1 and W2, respectively.

The connection point of the semiconductor switching elements U2, U3 constitutes the U-phase output terminal Pu, which is connected to the U-phase input terminal of the motor 42. The connection point of the semiconductor switching elements V2, V3 constitutes the V-phase output terminal Pv, which is connected to the V-phase input terminal of the motor 42. The connection point of the semiconductor switching elements W2, W3 constitutes the W-phase output terminal Pw, which is connected to the W-phase input terminal of the motor 42.

The connection point of the semiconductor switching elements U3 and U4, the connection point of the semiconductor switching elements V3 and V4, and the connection point of the semiconductor switching elements W3 and W4 are connected to the third output point P3 via diodes D6, D8, and D10, respectively.

The cathodes of diodes D6, D8, and D10 are connected to the third output point P3, and the anodes of diodes D6, D8, and D10 are connected to the connection point of semiconductor switching elements U3 and U4, the connection point of semiconductor switching elements V3 and V4, and the connection point of semiconductor switching elements W3 and W4, respectively.

In the inverter circuit 312, the semiconductor switching elements U1, U2, V1, V2, W1, and W2 constitute a first semiconductor switching element group connected between the first output point P1 and the motor 42. In particular, the semiconductor switching elements U1 and U2 constitute a U-phase first semiconductor switching element group connected between the first output point P1 and the U-phase input terminal of the motor 42. The semiconductor switching elements V1 and V2 constitute a V-phase first semiconductor switching element group connected between the first output point P1 and the V-phase input terminal of the motor 42. The semiconductor switching elements W1 and W2 constitute a W-phase first semiconductor switching element group connected between the first output point P1 and the W-phase input terminal of the motor 42.

The semiconductor switching elements U3, U4, V3, V4, W3, and W4 constitute a second semiconductor switching element group connected between the second output point P2 and the motor 42. In particular, the semiconductor switching elements U3 and U4 constitute a U-phase second semiconductor switching element group connected between the second output point P2 and the U-phase input terminal of the motor 42. The semiconductor switching elements V3 and V4 constitute a V-phase second semiconductor switching element group connected between the second output point P2 and the V-phase input terminal of the motor 42. The semiconductor switching elements W3 and W4 constitute a W-phase second semiconductor switching element group connected between the second output point P2 and the W-phase input terminal of the motor 42.

The semiconductor switching elements U2, U3, V2, V3, W2, and W3 constitute a third semiconductor switching element group connected between the third output point P3 and the motor 42. In particular, the semiconductor switching elements U2 and U3 constitute a U-phase third semiconductor switching element group connected between the third output point P3 and the U-phase input terminal of the motor 42. The semiconductor switching elements V2 and V3 constitute a V-phase third semiconductor switching element group connected between the third output point P3 and the V-phase input terminal of the motor 42. The semiconductor switching elements W2 and W3 constitute a W-phase third semiconductor switching element group connected between the third output point P3 and the W-phase input terminal of the motor 42.

The converter circuit 311 has a plurality of output points including the first to third output points P1 to P3. The inverter circuit 312 has a plurality of semiconductor switching element groups including a first semiconductor switching element group (semiconductor switching elements U1, U2, V1, V2, W1, W2) connected between the first output point P1 and the motor 42, a second semiconductor switching element group (semiconductor switching elements U3, U4, V3, V4, W3, W4) connected between the second output point P2 and the motor 42, and a third semiconductor switching element group (semiconductor switching elements U2, U3, V2, V3, W2, W3) connected between the third output point P3 and the motor 42. The drive circuit 31 is a so-called multilevel inverter, in particular a three-level inverter.

The inverter circuit 312 is connected to the electric motor 42 by connection lines Lu, Lv, and Lw. The connection lines Lu, Lv, and Lw are connection lines for the U, V, and W phases, respectively. The connection lines Lu, Lv, and Lw connect the U-phase, V-phase, and W-phase output terminals Pu, Pv, and Pw of the inverter circuit 312 to the U-phase, V-phase, and W-phase input terminals of the electric motor 42, respectively.

The state detection circuit 32 detects the state of the drive circuit 31. The state of the drive circuit 31 is the voltage of the DC output power of the converter circuit 311. In this embodiment, the state detection circuit 32 is a voltage detector that detects the DC output power of the converter circuit 311 and outputs a detection voltage indicating the voltage of the DC output power. In this embodiment, the state detection circuit 32 includes a voltage divider circuit connected between the output terminals of the smoothing circuit 311b of the converter circuit 311, that is, between the first output point P1 and the second output point P2, and outputs a detection voltage based on the voltage obtained from the voltage divider circuit. The state detection circuit 32 may also output a detection voltage based on the output of the voltage divider circuit and the differential amplifier. As an example, the non-inverting input terminal and the inverting input terminal of the differential amplifier are connected to both ends of the resistor of the voltage divider circuit, respectively, and the differential amplifier can output the voltage across the resistor as a detection voltage. By using a differential amplifier, the potential difference in the floating state can be detected, and the accuracy of the detection voltage can be improved. The position where the state detection circuit 32 is connected to the drive circuit 31 is not particularly limited, and may be any position where the DC output power of the converter circuit 311 can be detected. The position where the DC output power of the converter circuit 311 can be detected is not limited to within the converter circuit 311, but may be a position within the inverter circuit 312 that is equivalent in circuit terms to the first output point P1 and the second output point P2. The voltage divider circuit can have a conventionally known configuration, so a detailed description will be omitted.

The first protection device 33 is provided to stop the output of AC output power. The first protection device 33 includes switches Su, Sv, and Sw interposed between the drive circuit 31 and the motor 42. The switches Su, Sv, and Sw are connected between the U-phase, V-phase, and W-phase input terminals of the motor 42 and the U-phase output terminals Pu, Pv, and Pw, respectively. The switches Su, Sv, and Sw may be controllable switches such as semiconductor switches and electromagnetic relays. When the switches Su, Sv, and Sw are closed in the on state, the first protection device 33 enables the output of AC output power from the drive circuit 31 to the motor 42, and when the switches Su, Sv, and Sw are open in the off state, the first protection device 33 stops the output of AC output power from the drive circuit 31 to the motor 42.

The second protection device 34 is provided to stop the input of input power. The second protection device 34 includes switches S1 and S2 interposed between the drive circuit 31 and the power source 10. The switches S1 and S2 are respectively connected between the input terminal of the rectifier circuit 311a and the power source 10. The switches S1 and S2 may be, for example, a controllable switch such as a semiconductor switch or an electromagnetic relay. When the switches S1 and S2 are in the on state where they are closed, the second protection device 34 allows the input of input power from the power source 10 to the drive circuit 31, and when the switches S1 and S2 are in the off state where they are open, the second protection device 34 stops the input of input power from the power source 10 to the drive circuit 31.

The discharge device 36 is connected to the connection lines Lu, Lv, and Lw between the inverter circuit 312 and the motor 42. The discharge device 36 can be switched between a first state in which the connection lines Lu, Lv, and Lw between the inverter circuit 312 and the motor 42 are separated from the reference potential, and a second state in which the connection lines Lu, Lv, and Lw are connected to the reference potential. When the discharge device 36 is in the first state, the discharge device 36 does not have any particular effect on the motor 42. When the discharge device 36 is in the second state, the connection lines Lu, Lv, and Lw are connected to the reference potential, so that the energy stored in the windings of the motor 42 can be released. The reference potential exists outside the drive circuit 31. Here, the reference potential existing outside the drive circuit 31 means that the reference potential and the drive circuit 31 are electrically independent. An example of a reference potential existing outside the drive circuit 31 is the ground. In this embodiment, the reference potential is provided by the ground. That is, the discharge device 36 can release the energy remaining when the compressor 4 is stopped, that is, when the motor 42 is stopped. If energy remains in the motor 42, there is a concern that such residual energy may cause abnormal phenomena such as discharge phenomena in the motor 42. The discharge device 36 enables the release of the energy remaining in the motor 42, so that the possibility of occurrence of abnormal phenomena caused by such residual energy can be reduced, and the suppression of disproportionation reactions can be improved. In addition, if the connection lines Lu, Lv, and Lw are shorted, energy remains in the drive circuit 31. Therefore, by connecting the connection lines Lu, Lv, and Lw to ground, the energy remaining in the drive circuit 31 is released to the outside of the drive circuit 31.

Fig. 3 is a schematic circuit diagram of the discharge device 36. The discharge device 36 includes a plurality of series circuits 361-363 that are connected between a plurality of connection lines Lu, Lv, Lw that respectively correspond to a plurality of phases of the AC output power and a ground that provides a reference potential. The series circuits 361, 362, 363 are U-, V-, and W-phase series circuits of switches SW31, SW32, SW33 and resistors R31, R32, R33 that are connected between the connection lines Lu, Lv, Lw, and ground, respectively.

The switches SW31, SW32, and SW33 are controllable switches. For example, the switches SW31, SW32, and SW33 are configured as 3PST switches that can operate in conjunction with each other. The switches SW31, SW32, and SW33 may be SPST switches that can operate independently. Examples of the switches SW31, SW32, and SW33 include mechanical contact switches such as electromagnetic relays and non-contact switches such as transistors. The first terminals of the switches SW31, SW32, and SW33 are connected to the connection lines Lu, Lv, and Lw, respectively, and the second terminals of the switches SW31, SW32, and SW33 are connected to ground via resistors R31, R32, and R33, respectively. The resistance values of the resistors R31, R32, and R33 are not particularly limited, but are, for example, 1 kΩ. The first state of the discharge device 36 is a state in which the switches SW31, SW32, and SW33 are off. The second state of the discharge device 36 is a state in which the switches SW31, SW32, and SW33 are on.

The control circuit 35 may be realized by, for example, a computer system including at least one processor (microprocessor) and one or more memories. The computer system may include one or more A/D converters. For example, the one or more A/D converters are used to convert the detection voltage from the state detection circuit 32 from analog to digital format. The control circuit 35 controls the drive circuit 31, the first protection device 33, the second protection device 34, and the discharge device 36. In particular, the control circuit 35 executes PWM control of a group of multiple semiconductor switching elements of the inverter circuit 312 of the drive circuit 31 so that the drive circuit 31 operates the electric motor 42. More specifically, the control circuit 35 controls the switching of the multiple semiconductor switching elements U1 to U4, V1 to V4, and W1 to W4 of the inverter circuit 312 of the drive circuit 31 so that the inverter circuit 312 supplies AC output power (three-phase AC power) to the electric motor 42 based on the DC output power from the smoothing circuit 311b.

The semiconductor switching elements U1 to U4 have a first state in which the semiconductor switching elements U1 and U2 are on and the semiconductor switching elements U3 and U4 are off, a second state in which the semiconductor switching elements U3 and U4 are on and the semiconductor switching elements U1 and U2 are off, and a third state in which the semiconductor switching elements U2 and U3 are on and the semiconductor switching elements U1 and U4 are off. The voltage at the U-phase output terminal Pu is E/2 in the first state, -E/2 in the second state, and 0 in the third state.

　There are three states for the semiconductor switching elements V1 to V4: a first state in which the semiconductor switching elements V1 and V2 are on and the semiconductor switching elements V3 and V4 are off; a second state in which the semiconductor switching elements V3 and V4 are on and the semiconductor switching elements V1 and V2 are off; and a third state in which the semiconductor switching elements V2 and V3 are on and the semiconductor switching elements V1 and V4 are off. The voltage at the V-phase output terminal Pv is E/2 in the first state, -E/2 in the second state, and 0 in the third state.

The semiconductor switching elements W1 to W4 have a first state in which the semiconductor switching elements W1 and W2 are on and the semiconductor switching elements W3 and W4 are off, a second state in which the semiconductor switching elements W3 and W4 are on and the semiconductor switching elements W1 and W2 are off, and a third state in which the semiconductor switching elements W2 and W3 are on and the semiconductor switching elements W1 and W4 are off. The voltage at the W-phase output terminal Pw is E/2 in the first state, -E/2 in the second state, and 0 in the third state.

In this way, the drive circuit 31 can provide five voltage levels: E, E/2, 0, -E/2, and -E.

The control circuit 35 controls the switching of the semiconductor switching elements U1-U4, V1-V4, W1-W4 of the inverter circuit 312 of the drive circuit 31 based on, for example, U-phase, V-phase, and W-phase output voltage command values corresponding to the sine wave AC voltages of the U-phase, V-phase, and W-phase of the three-phase AC, respectively, and the first and second carrier triangular waves. The value of the first carrier triangular wave is 0 or more, and the value of the second carrier triangular wave is 0 or less. The drive circuit 31 can provide five levels of voltage: E, E/2, 0, -E/2, and -E, so that the voltage between the U-phase input terminal and the V-phase input terminal of the motor 42, the voltage between the V-phase input terminal and the W-phase input terminal of the motor 42, and the voltage between the W-phase input terminal and the U-phase input terminal of the motor 42 can each be made closer to a sine wave.

The control circuit 35 further executes processing to suppress the disproportionation reaction of the working medium 20 circulating through the refrigeration cycle circuit 2 based on the detected voltage from the state detection circuit 32.

The causes of the disproportionation reaction of the working medium 20 are thought to be heat and radicals. For example, when radicals are generated under high temperature and pressure, the disproportionation reaction of the working medium 20 is thought to proceed. Radicals may be generated, for example, by a discharge phenomenon that may occur when some abnormality occurs in the compressor 4 or the drive circuit 31.

The inventors have found that when a discharge phenomenon occurs in the compressor 4, a sudden change occurs in the voltage of the DC output power of the converter circuit 311, that is, the voltage of the smoothing circuit 311b of the drive circuit 31. FIG. 4 is a waveform diagram of the voltage of the DC output power of the converter circuit 311. In FIG. 4, the voltage of the DC output current gradually decreases at times t11 to t12, t21 to t22, t31 to 32, t41 to t42, and t51 to 52, but this voltage decrease is due to the switching of the semiconductor switching elements U1 to U4, V1 to V4, and W1 to W4 of the inverter circuit 312. When the switching frequency of the inverter circuit 312 is, for example, 1.0 kHz to 5.0 kHz, the time between time t11 and time t21 is about 0.2 to 1.0 ms. Here, at time t33, a sudden drop in the voltage of the DC output current is observed, which is thought to be due to the occurrence of a discharge phenomenon.

From this perspective, the control circuit 35 determines whether a discharge phenomenon has occurred based on the detected voltage from the state detection circuit 32, and if it determines that a discharge phenomenon has occurred, it stops or limits the operation of the drive circuit 31 to suppress the disproportionation reaction of the working medium circulating through the refrigeration cycle circuit 2.

The control device 3 detects the signs of a disproportionation reaction based on the changes occurring in the DC output power (voltage of the smoothing circuit 311b) inside the drive circuit 31, not on the changes occurring in the current actually flowing from the drive circuit 31 to the motor 42. The time scale of the discharge phenomenon is shorter than the time scale of smoothing (rectification) in the drive circuit 31. For example, the time scale of the discharge phenomenon is on the order of μs. Therefore, it is possible to determine whether a discharge phenomenon is occurring based on the DC output power inside the drive circuit 31. Furthermore, the measurement of the DC output power (voltage of the smoothing circuit 311b) inside the drive circuit 31 can be performed in a shorter time and at a shorter cycle than the measurement of the current actually flowing from the drive circuit 31 to the motor 42. This enables the earlier detection of the signs of a disproportionation reaction of the working medium 20. If the signs of a disproportionation reaction of the working medium 20 can be detected earlier in this way, the disproportionation reaction can be suppressed earlier, thereby improving the suppression of the disproportionation reaction.

In this embodiment, the control circuit 35 stops or limits the operation of the drive circuit 31 when the detected voltage falls below a second voltage that is equal to or lower than the first voltage. The second voltage is set to determine whether a discharge phenomenon has occurred, which may occur when some abnormality occurs in the compressor 4 or the drive circuit 31. Referring to FIG. 4, if the normal voltage (first voltage) of the DC output current is E, it has been observed that the voltage of the DC output current becomes 0.8E or less, or even 0.3E or less, due to a discharge phenomenon. From this point of view, it is preferable that the second voltage is 0.3 times or more and 0.8 times or less than the first voltage. In this embodiment, the second voltage is 0.8 times the first voltage.

The operation of the drive circuit 31 can be stopped by either stopping the output of AC output power, stopping the output of DC output power, or stopping the input of input power. The operation of the drive circuit 31 can be restricted by lowering the set value of the amplitude of the AC output power, or lowering the set value of the frequency of the AC output power.

In this embodiment, the control circuit 35 sets the first protection device 33 to the OFF state to electrically isolate the electric motor 42 from the drive circuit 31 and stop the output of AC output power. When the output of AC output power is to be resumed, the control circuit 35 sets the first protection device 33 to the ON state to connect the electric motor 42 to the drive circuit 31.

In this embodiment, the control circuit 35 controls the drive circuit 31 to lower the set value of the amplitude of the AC output power. In this embodiment, the drive circuit 31 can provide five levels of voltage: E, E/2, 0, -E/2, and -E, so the set value of the amplitude of the AC output power is changed from E to E/2. In this case, the rotation speed of the motor 42 is lower than when the set value of the amplitude of the AC output power is E.

When the input of input power is stopped, the output of AC output power is stopped as a result. In this embodiment, the control circuit 35 sets the second protection device 34 to the OFF state to electrically isolate the power source 10 from the drive circuit 31 and stop the output of AC output power. When the input of input power is to be resumed, the control circuit 35 sets the second protection device 34 to the ON state to connect the power source 10 to the drive circuit 31.

The control circuit 35 stops or limits the operation of the drive circuit 31 in different ways depending on the number of times the detected voltage falls below the second voltage. In particular, the control circuit 35 executes processing that suppresses the disproportionation reaction to a higher degree as the number of times the detected voltage falls below the second voltage increases. This enables the control device 3 to suppress the disproportionation reaction even when relatively minor discharge phenomena occur consecutively within a short period of time. For example, it is possible to prevent disproportionation reactions from being induced beyond a predetermined energy due to consecutive occurrences of low-energy abnormal states (discharges), thereby improving the safety of using the working medium 20.

The control circuit 35 stops or limits the operation of the drive circuit 31 in different ways depending on the time difference between the first time when the detected voltage first becomes less than the second voltage and the second time when the detected voltage next becomes less than the second voltage. In particular, the control circuit 35 executes processing that suppresses the disproportionation reaction to a higher degree the shorter the time difference. This enables the control device 3 to suppress the disproportionation reaction even when relatively minor discharge phenomena occur consecutively within a short period of time. This prevents, for example, a disproportionation reaction from being induced beyond a predetermined energy due to consecutive occurrences of low-energy abnormal states (discharges), improving the safety of using the working medium 20.

The process for suppressing the disproportionation reaction includes, for example, the first process to the third process. The first process is a process for stopping the output of AC output power and resuming the output of AC output power after a standby time has elapsed. The second process is a process for stopping the output of AC output power and operating with a lower set value of the amplitude of the AC output power after a standby time has elapsed. The third process is a process for stopping the output of AC output power and stopping the input of input power. In the first to third processes, the degree of suppression of the disproportionation reaction increases in the order of the third process, the second process, and the first process. In the first or second process, the longer the standby time, the higher the degree of suppression of the disproportionation reaction.

When the operation of the drive circuit 31 is stopped, the control circuit 35 switches the discharge device 36 to the second state. When the operation of the drive circuit 31 is released from the stopped state, the control circuit 35 switches the discharge device 36 to the first state. This makes it possible to release the energy remaining when the compressor 4 is stopped.

Next, an example of the operation of the control circuit 35 of the control device 3 will be briefly described with reference to Figures 5 to 10. Each of Figures 5 to 10 is a part of a flowchart of the operation of the control circuit 35 of the control device 3, and Figures 5 to 10 are combined to complete one flowchart.

Refer to FIG. 5. The control circuit 35 outputs AC output power to the motor 42 based on the input power of the power source 10 via the drive circuit 31 to drive the compressor 4. The control circuit 35 sets the number of abnormalities to 0 (S10). The number of abnormalities indicates the number of times the detected voltage is less than the second voltage. The number of abnormalities is an indicator of the likelihood of a disproportionation reaction occurring.

The control circuit 35 acquires the detection voltage from the state detection circuit 32 (S11). The control circuit 35 determines whether the detection voltage is less than the second voltage (S12).

If the detected voltage is not less than the second voltage (S12: NO), the process returns to step S10. In steps S11 and S12, the control circuit 35 determines whether the detected voltage is less than the second voltage at a predetermined period. It is preferable that the predetermined period here is shorter than the period corresponding to the reference frequency of the inverter circuit 312 (e.g., 1000 to 5000 Hz).

In step S12, if the detected voltage is less than the second voltage (S12: YES), the control circuit 35 adds 1 to the number of abnormalities (S13) and determines whether the number of abnormalities is 1 or less (S14).

In step S14, if the number of abnormalities is 1 or less (S14: YES), the control circuit 35 sets the first protection device 33 to the OFF state to stop the output of AC output power, and switches the discharge device 36 to the second state (S15). The control circuit 35 determines whether a first standby time has elapsed since the output of AC output power was stopped (S16). The first standby time is, for example, 1 s. When the first standby time has elapsed (S16: YES), the control circuit 35 sets the first protection device 33 to the ON state to resume the output of AC output power, and switches the discharge device 36 to the first state (S17), thereby resuming operation of the compressor 4 (S18). Thereafter, the process returns to step S11.

In this way, when the detected voltage becomes less than the second voltage, the control circuit 35 stops the output of the AC output power and switches the discharge device 36 to the second state, and when the first standby time has elapsed since the output of the AC output power was stopped, the control circuit 35 resumes the output of the AC output power and switches the discharge device 36 to the first state.

In step S14, if the number of abnormalities is not 1 or less (S14: NO), referring to FIG. 6, the control circuit 35 determines whether the time difference between the first time when the detected voltage first becomes less than the second voltage and the second time when the detected voltage next becomes less than the second voltage is within a first predetermined time (step S19). The shortness of the time difference is an indicator of the likelihood of a disproportionation reaction occurring. The first predetermined time is, for example, about 100 times the period corresponding to the reference frequency of the inverter circuit 312, and is about 20 to 100 ms.

In step S19, if the time difference is within the first predetermined time (step S19: YES), the control circuit 35 sets the first protection device 33 to the OFF state to stop the output of AC output power, and switches the discharge device 36 to the second state (S20). The control circuit 35 sets the second protection device 34 to the OFF state to stop the input of input power (S21). The control circuit 35 outputs a first abnormality notification (S22). The first abnormality notification indicates that an abnormality has occurred in the refrigeration cycle device 1 that is highly likely to cause a disproportionation reaction. The first abnormality notification is output to, for example, the control circuit of the indoor unit 1b and a remote controller. After this, the control circuit 35 stops the operation of the compressor 4 (S23).

In this way, if the detected voltage becomes less than the second voltage (S19: YES) before a predetermined time (first predetermined time) has elapsed since the output of the AC output power was resumed after the first standby time (S17), the control circuit 35 stops the output of the AC output power, switches the discharge device 36 to the second state (S20), and stops the input of the input power (S21).

If the time difference is not within the first predetermined time in step S19 (step S19: NO), referring to FIG. 7, the control circuit 35 determines whether the time difference is within a second predetermined time that is longer than the first predetermined time (step S24). The second predetermined time is, for example, about 1000 times the period corresponding to the reference frequency of the inverter circuit 312, and is about 200 ms to 1 s.

In step S24, if the time difference is within the second predetermined time (step S24: YES), the control circuit 35 sets the first protection device 33 to the off state to stop the output of the AC output power, and switches the discharge device 36 to the second state (S25). The control circuit 35 changes the switching control of the semiconductor switching element of the drive circuit 31 so that the set value of the amplitude of the AC output power decreases from E to E/2 (S26). The control circuit 35 outputs a second abnormality notification (S27). The second abnormality notification indicates that an abnormality that is likely to cause a disproportionation reaction has occurred in the refrigeration cycle device 1. The second abnormality notification is output to, for example, the control circuit and remote controller of the indoor unit 1b.

The control circuit 35 determines whether a fourth waiting time has elapsed since the output of the AC output power was stopped (S28). The fourth waiting time is longer than the first waiting time. The fourth waiting time is, for example, 60 seconds. When the fourth waiting time has elapsed (S28: YES), as shown in FIG. 8, the control circuit 35 switches the discharge device 36 to the first state and sets the first protection device 33 to the on state to resume the output of the AC output power (S29), thereby resuming the operation of the compressor 4 (S30). In this case, the set value of the amplitude of the AC output power remains lowered from E to E/2.

In this way, when the detected voltage becomes less than the second voltage before a predetermined time (second predetermined time) has elapsed since the resumption of output of the AC output power after the first standby time (S17), the control circuit 35 stops the output of the AC output power, switches the discharge device 36 to the second state (S25), and lowers the set value of the amplitude of the AC output power (S26). When a fourth standby time longer than the first standby time has elapsed since the stop of the output of the AC output power, the control circuit 35 switches the discharge device 36 to the first state and resumes the output of the AC output power while keeping the set value of the amplitude of the AC output power lowered (S29).

Then, the control circuit 35 acquires the detection voltage from the state detection circuit 32 (S31). The control circuit 35 determines whether the detection voltage is less than the second voltage (S32).

If the detected voltage is less than the second voltage in step S32 (S32: YES), proceed to step S20 in FIG. 6.

In step S32, if the detected voltage is not less than the second voltage (S32: NO), the control circuit 35 determines whether the second monitoring time has elapsed since the compressor 4 restarted operating (S33).

In step S33, if the second monitoring time has elapsed since the compressor 4 restarted operating (S33: YES), the control circuit 35 cancels the reduction in the set value of the amplitude of the AC output power, returns the set value of the amplitude of the AC output power to E (S34), and proceeds to step S11 in FIG. 5.

In step S33, if the second monitoring time has not elapsed since the compressor 4 restarted operation (S33: NO), the process returns to step S31.

In steps S31 to S33, if the detected voltage falls below the second voltage between the time when compressor 4 restarts operation and the time when the second monitoring time has elapsed, the process proceeds to step S20 in FIG. 6, and if the detected voltage does not fall below the second voltage between the time when compressor 4 restarts operation and the time when the second monitoring time has elapsed, the process proceeds to step S34.

In this way, if the detected voltage does not become less than the second voltage during the second monitoring time from when the output of the AC output power is resumed after the fourth waiting time has elapsed (S29) (YES in S33), the control circuit 35 cancels the reduction in the set value of the amplitude of the AC output power (S34). If the detected voltage becomes less than the second voltage before the second monitoring time has elapsed after the output of the AC output power is resumed after the fourth waiting time has elapsed (S29) (YES in S32), the control circuit 35 stops the output of the AC output power, switches the discharge device 36 to the second state (S20), and stops the input of the input power (S21).

Returning to FIG. 7, if the time difference is not within the second predetermined time in step S24 (step S24: NO), referring to FIG. 9, the control circuit 35 determines whether the time difference is within a third predetermined time that is longer than the second predetermined time (step S35). The third predetermined time is, for example, about 10,000 times the period corresponding to the reference frequency of the inverter circuit 312, and is about 2 s to 10 s.

In step S35, if the time difference is not within the third predetermined time (step S35: NO), the process returns to step S10, and the control circuit 35 sets the number of abnormalities to 0 (see FIG. 5). In other words, if a sufficient amount of time has passed since the detection of the abnormality, the possibility of a discharge phenomenon occurring is considered to be low, so the number of abnormalities is reset to 0.

In step S35, if the time difference is within the third predetermined time (step S35: YES), the control circuit 35 determines whether the number of abnormalities is 2 or less (S36).

In step S36, if the number of abnormalities is 2 or less (S36: YES), the control circuit 35 sets the first protection device 33 to the off state to stop the output of the AC output power, and switches the discharge device 36 to the second state (S37). The control circuit 35 outputs a third abnormality notification (S38). The third abnormality notification indicates that an abnormality that may cause a disproportionation reaction has occurred in the refrigeration cycle device 1. The third abnormality notification is output, for example, to the control circuit of the indoor unit 1b and a remote controller. The control circuit 35 determines whether a second standby time has elapsed since the output of the AC output power was stopped (S39). The second standby time is longer than the first standby time. The second standby time is, for example, 10 s. When the second standby time has elapsed (S39: YES), the control circuit 35 switches the discharge device 36 to the first state, sets the first protection device 33 to the on state, and resumes the output of the AC output power (S40), thereby resuming the operation of the compressor 4 (S41). After that, return to step S11.

In this way, if the detected voltage becomes less than the second voltage before a predetermined time (third predetermined time) has elapsed since the resumption of the output of the AC output power after the first standby time has elapsed (S17), the control circuit 35 stops the output of the AC output power and switches the discharge device 36 to the second state. When a second standby time longer than the first standby time has elapsed since the output of the AC output power was stopped, the control circuit 35 switches the discharge device 36 to the first state and resumes the output of the AC output power (S40).

In step S36, if the number of abnormalities is not two or less (S36: NO), that is, if the number of abnormalities is three or more, the control circuit 35 sets the first protection device 33 to the off state to stop the output of AC output power, and switches the discharge device 36 to the second state (S42). The control circuit 35 changes the switching control of the semiconductor switching element of the drive circuit 31 so that the set value of the amplitude of the AC output power is reduced from E to E/2 (S43). The control circuit 35 outputs a second abnormality notification (S44).

The control circuit 35 determines whether the third waiting time has elapsed since the output of the AC output power was stopped (S45). The third waiting time is longer than the second waiting time. The third waiting time is, for example, 60 seconds. When the third waiting time has elapsed (S45: YES), as shown in FIG. 10, the control circuit 35 switches the discharge device 36 to the first state and sets the first protection device 33 to the on state to resume the output of the AC output power (S46), thereby resuming the operation of the compressor 4 (S47). In this case, the set value of the amplitude of the AC output power remains lowered from E to E/2.

In this way, when the detected voltage becomes less than the second voltage before a predetermined time (third predetermined time) has elapsed since the resumption of output of the AC output power after the second standby time (S40), the control circuit 35 stops the output of the AC output power, switches the discharge device 36 to the second state (S42), and lowers the set value of the amplitude of the AC output power (S43). When a third standby time longer than the second standby time has elapsed since the stop of the output of the AC output power, the control circuit 35 switches the discharge device 36 to the first state and resumes the output of the AC output power while keeping the set value of the amplitude of the AC output power lowered (S47).

Then, the control circuit 35 acquires the detection voltage from the state detection circuit 32 (S48). The control circuit 35 determines whether the detection voltage is less than the second voltage (S49).

If the detected voltage is less than the second voltage in step S49 (S49: YES), proceed to step S20 in FIG. 6.

In step S49, if the detected voltage is not less than the second voltage (S49: NO), the control circuit 35 determines whether the first monitoring time has elapsed since the compressor 4 restarted operating (S50). The first monitoring time may be the same as or different from the second monitoring time in step S33.

In step S50, if the first monitoring time has elapsed since the compressor 4 restarted operating (S50: YES), the control circuit 35 cancels the reduction in the set value of the amplitude of the AC output power, returns the set value of the amplitude of the AC output power to E (S51), and proceeds to step S11 in FIG. 5.

In step S50, if the first monitoring time has not elapsed since the compressor 4 restarted operation (S50: NO), the process returns to step S48.

In steps S48 to S50, if the detected voltage becomes less than the second voltage between the time when the compressor 4 restarts operation and the time when the first monitoring time has elapsed, the process proceeds to step S20 in FIG. 6, and if the detected voltage does not become less than the second voltage between the time when the compressor 4 restarts operation and the time when the first monitoring time has elapsed, the process proceeds to step S51.

In this way, if the detected voltage does not become less than the second voltage during the first monitoring time from when the output of the AC output power is resumed after the third waiting time has elapsed (S47) (YES in S50), the control circuit 35 cancels the reduction in the set value of the amplitude of the AC output power (S51). If the detected voltage becomes less than the second voltage before the first monitoring time has elapsed after the output of the AC output power is resumed after the third waiting time has elapsed (S47) (YES in S49), the control circuit 35 stops the output of the AC output power, switches the discharge device 36 to the second state (S20), and stops the input of the input power (S21).

In the control device 3 described above, the control circuit 35 stops the operation of the drive circuit 31 when an abnormality occurs, such as when a discharge phenomenon occurs. This reduces the possibility of abnormalities such as discharge phenomena occurring continuously. Furthermore, the control circuit 35 connects the connection lines Lu, Lv, and Lw, which are the current paths between the inverter circuit 312 and the electric motor 42, to a reference potential by the discharge device 36. This makes it possible to release the energy stored in the electric motor 42 by driving the compressor 4. This reduces the possibility of abnormal phenomena occurring due to residual energy when the electric motor 42 of the compressor 4 is stopped, and makes it possible to improve the suppression of disproportionation reactions.

[1.2 Effects, etc.]
The control device 3 described above controls the compressor 4 of the refrigeration cycle circuit 2 in which the working medium 20 circulates. The control device 3 includes a drive circuit 31 that drives the compressor 4, and a discharge device 36 that can switch between a first state in which the connection lines Lu, Lv, and Lw between the drive circuit 31 and the compressor 4 are separated from a reference potential and a second state in which the connection lines Lu, Lv, and Lw are connected to the reference potential. This configuration can reduce the possibility of an abnormal phenomenon occurring due to residual energy when the compressor 4 is stopped, and enables improved suppression of the disproportionation reaction.

In the control device 3, the reference potential exists outside the drive circuit 31. This configuration allows the remaining energy when the compressor 4 is stopped to be released outside the drive circuit 31.

In the control device 3, the reference potential is provided by the ground. This configuration allows the remaining energy to be released outside the drive circuit 31 when the compressor 4 is stopped.

The control device 3 further includes a control circuit 35 that controls the drive circuit 31 and the discharge device 36. In response to detection of an abnormality in at least one of the compressor 4 and the drive circuit 31, the control circuit 35 stops the operation of the drive circuit 31 and switches the discharge device 36 to the second state. This configuration can reduce the possibility of abnormal phenomena occurring due to residual energy when the compressor 4 is stopped, and enables improved suppression of the disproportionation reaction.

In the control device 3, the control circuit 35 switches the discharge device 36 to the first state when the operation of the drive circuit 31 is released from the stopped state. This configuration can shorten the time difference between the release of the operation of the drive circuit 31 and the switching of the discharge device 36 to the first state, and can shorten the stop time of the compressor 4.

In the control device 3, the discharge device 36 has series circuits 361, 362, 363 consisting of switches SW31, SW32, SW33 and resistors R31, R32, R33. The series circuits 361, 362, 363 are connected between the connection lines Lu, Lv, Lw and the reference potential. The first state is a state in which the switches SW31, SW32, SW33 are off. The second state is a state in which the switches SW31, SW32, SW33 are on. This configuration can reduce the possibility of abnormal phenomena occurring due to residual energy when the compressor 4 is stopped, and enables improved suppression of the disproportionation reaction.

In the control device 3, the resistance of resistors R31, R32, and R33 is 1 kΩ. This configuration can reduce the possibility of abnormal phenomena occurring due to residual energy when the compressor 4 is stopped, and enables improved suppression of disproportionation reactions.

In the control device 3, the connection lines Lu, Lv, Lw include a plurality of connection lines Lu, Lv, Lw that respectively correspond to the three phases of the AC output power. The discharge device 36 has a plurality of series circuits 361, 362, 363 that are respectively connected between the plurality of connection lines Lu, Lv, Lw and the reference potential. This configuration can reduce the possibility of abnormal phenomena occurring due to residual energy when the compressor 4 is stopped, and enables improved suppression of the disproportionation reaction.

The control device 3 further includes a state detection circuit 32 that detects the state of at least one of the compressor 4 and the drive circuit 31. The drive circuit 31 includes a converter circuit 311 that outputs DC output power based on the input power from the power source 10 so that the voltage of the DC output power becomes a first voltage, and an inverter circuit 312 that outputs AC output power to the compressor 4 based on the DC output power. The state detection circuit 32 detects the DC output power and outputs a detection voltage indicating the voltage of the DC output power. When the detection voltage becomes less than a second voltage that is equal to or less than the first voltage, the control circuit 35 stops the operation of the drive circuit 31 and switches the discharge device 36 to the second state. This configuration can reduce the possibility of an abnormal phenomenon occurring due to the energy remaining when the compressor 4 is stopped, and enables improved suppression of the disproportionation reaction.

In the control device 3, the second voltage is 0.3 to 0.8 times the first voltage. This configuration enables early detection of signs of a disproportionation reaction in the working medium 20 and improves suppression of the disproportionation reaction.

The discharge device 36 described above is connected to the connection lines Lu, Lv, and Lw between the compressor 4 of the refrigeration cycle circuit 2 in which the working medium 20 circulates and the drive circuit 31 that drives the compressor 4, and is configured to be switchable between a first state in which the connection lines Lu, Lv, and Lw are isolated from the reference potential, and a second state in which the connection lines Lu, Lv, and Lw are connected to the reference potential. This configuration can reduce the possibility of abnormal phenomena occurring due to residual energy when the compressor 4 is stopped, and enables improved suppression of the disproportionation reaction.

The refrigeration cycle device 1 described above includes a control device 3 and a refrigeration cycle circuit 2. This configuration can reduce the possibility of abnormal phenomena occurring due to residual energy when the compressor 4 is stopped, and enables improved suppression of disproportionation reactions.

In the refrigeration cycle device 1, the working medium contains an ethylene-based fluoroolefin. This configuration allows for improved suppression of the disproportionation reaction of the working medium 20.

In the refrigeration cycle device 1, the ethylene-based fluoroolefin is 1,1,2-trifluoroethylene, trans-1,2-difluoroethylene, cis-1,2-difluoroethylene, 1,1-difluoroethylene, tetrafluoroethylene, or monofluoroethylene. This configuration enables improved suppression of the disproportionation reaction of the working medium 20.

In the refrigeration cycle device 1, the working medium 20 further contains difluoromethane. This configuration enables improved suppression of the disproportionation reaction of the working medium 20.

In the refrigeration cycle device 1, the working medium 20 further contains saturated hydrocarbons. This configuration enables improved suppression of the disproportionation reaction of the working medium 20.

In the refrigeration cycle device 1, the working medium 20 contains a haloalkane having one or two carbon atoms as a disproportionation inhibitor that suppresses the disproportionation reaction of ethylene-based fluoroolefins. This configuration enables improved suppression of the disproportionation reaction of the working medium 20.

In the refrigeration cycle device 1, the saturated hydrocarbons include n-propane. This configuration allows for improved suppression of the disproportionation reaction of the working medium 20.

The control device 3 described above can be said to execute the following control method. The control method is executed by the control device 3 that controls the compressor 4 of the refrigeration cycle circuit 2 in which the working medium 20 circulates. The control device 3 includes a drive circuit 31 that drives the compressor 4, and a discharge device 36 that can switch between a first state in which the connection lines Lu, Lv, and Lw between the drive circuit 31 and the compressor 4 are separated from a reference potential, and a second state in which the connection lines Lu, Lv, and Lw are connected to the reference potential. The control method stops the operation of the drive circuit 31 and switches the discharge device 36 to the second state in response to detection of an abnormality in at least one of the compressor 4 and the drive circuit 31. This configuration can reduce the possibility of an abnormal phenomenon occurring due to the energy remaining when the compressor 4 is stopped, and enables improved suppression of the disproportionation reaction.

The control method executed by the control device 3 can be realized by a computer system executing a program. This program is executed by a computer system included in the control device 3 that controls the compressor 4 of the refrigeration cycle circuit 2 in which the working medium 20 circulates. The control device 3 includes a drive circuit 31 that drives the compressor 4, and a discharge device 36 that can switch between a first state in which the connection lines Lu, Lv, and Lw between the drive circuit 31 and the compressor 4 are separated from a reference potential, and a second state in which the connection lines Lu, Lv, and Lw are connected to the reference potential. The program causes the computer system to stop the operation of the drive circuit 31 and switch the discharge device 36 to the second state in response to detection of an abnormality in at least one of the compressor 4 and the drive circuit 31. This configuration can reduce the possibility of an abnormal phenomenon occurring due to the energy remaining when the compressor 4 is stopped, and enables improved suppression of the disproportionation reaction.

2. Modifications
The embodiments of the present disclosure are not limited to the above-mentioned embodiments. The above-mentioned embodiments can be modified in various ways depending on the design, etc., as long as the object of the present disclosure can be achieved. Below, modified examples of the above-mentioned embodiments are listed. The modified examples described below can be applied in appropriate combination.

In one modified example, the discharge device 36 is not necessarily limited to a configuration in which multiple connection lines Lu, Lv, and Lw can be connected to a reference potential, but only needs to be able to connect at least one of the multiple connection lines Lu, Lv, and Lw to a reference potential.

In one modified example, in the control circuit 35, stopping the operation of the drive circuit 31 may include one or more of stopping the output of AC output power, stopping the output of DC output power, or stopping the input of input power. Restricting the operation of the drive circuit 31 may include one or more of reducing the set value of the amplitude of the AC output power, or reducing the set value of the frequency of the AC output power.

In one modified example, the control circuit 35 may gradually stop and decelerate the electric motor 42. As one example, the control circuit 35 may gradually reduce the effective value of the AC output power supplied to the electric motor 42 by gradually reducing at least one of the amplitude and frequency of the AC output power.

In one modified example, the operation of the control circuit 35 is not necessarily limited to the operations shown in the flowcharts shown in Figures 5 to 10. The flowcharts shown in Figures 5 to 10 are merely examples.

For example, in the operation of the control circuit 35, the processes of steps S19 to S23, i.e., the processes of stopping the output of AC output power and stopping the input of input power, are not essential. In the operation of the control circuit 35, the processes of steps S24 to S28, i.e., the processes of stopping the output of AC output power and lowering the set value of the amplitude of the AC output power after the standby time has elapsed, are not essential. Similarly, in the operation of the control circuit 35, the processes of steps S29 to S34, steps S35 to S41, or steps S42 to S51 are not essential.

The control circuit 35 does not necessarily have to stop or limit the operation of the drive circuit 31 in a different manner depending on the time difference between the first time when the detected voltage first becomes less than the second voltage and the second time when the detected voltage next becomes less than the second voltage, or the number of times the detected voltage becomes less than the second voltage.

In one modified example, the first protection device 33 is not limited to a circuit configuration including switches Su, Sv, and Sw, and may include a circuit configuration that adjusts the magnitude of the AC output power output from the drive circuit 31 to the electric motor 42, for example, the magnitude of the voltage. The first protection device 33 may be disposed within the drive circuit 31.

In one modified example, the second protection device 34 is not limited to a circuit configuration including switches S1 and S2, and may include a circuit configuration that adjusts the magnitude of the input power input from the power source 10 to the drive circuit 31, for example, the magnitude of the voltage. The second protection device 34 may be disposed within the drive circuit 31.

In one modified example, the control device 3 does not necessarily have to include both the first protection device 33 and the second protection device 34, and may include either the first protection device 33 or the second protection device 34, and if the drive circuit 31 has a function of adjusting the AC output power, the first and second protection devices 33, 34 can be omitted. For example, the control circuit 35 may stop the output of AC output power to the motor 42 by turning on the semiconductor switching elements V1 to V4 of the inverter circuit 312 and turning off the remaining semiconductor switching elements U1 to U4, W1 to W4. In this case, the first protection device 33 may be omitted.

FIG. 11 shows a modified control device 3A. In FIG. 11, the control device 3A includes a third protection device 37. The third protection device 37 is provided to stop the output of DC output power. The third protection device 37 includes switches S3, S4, and S5 interposed between the converter circuit 311 and the inverter circuit 312 of the drive circuit 31. The switch S3 is commonly connected between the first output point P1 and the semiconductor switching elements U1, V1, and W1. The switch S4 is commonly connected between the second output point P2 and the semiconductor switching elements U4, V4, and W4. The switch S5 is commonly connected between the third output point P3 and the connection point between the diodes D5 and D6, the connection point between the diodes D7 and D8, and the connection point between the diodes D9 and D10. The switches S3, S4, and S5 may be controllable switches such as semiconductor switches and electromagnetic relays. The third protection device 37 allows the output of DC output power from the converter circuit 311 to the inverter circuit 312 when the switches S3, S4, and S5 are closed in the on state, and stops the output of DC output power from the converter circuit 311 to the inverter circuit 312 when the switches S3, S4, and S5 are open in the off state.

When stopping the output of power to the compressor, the safety level increases in the order of stopping the input power, stopping the output of DC output power, and stopping the output of AC output power. Therefore, after the operation of the first protection device 33, the third protection device 37 may be operated before the second protection device 34 is operated. Note that if the third protection device 37 is present, the second protection device 34 may be omitted.

In one modified example, the third protection device 37 is not limited to a circuit configuration including switches S3, S4, and S5, but may include a circuit configuration that adjusts the magnitude of the DC output power output from the converter circuit 311 to the inverter circuit 312, for example, the magnitude of the voltage.

In one modified example, the state detection circuit 32 is not limited to a configuration that detects the voltage value of the DC output power of the converter circuit 311. The state detection circuit 32 may be configured to detect the state of at least one of the compressor 4 and the drive circuit 31.

For example, the state of the drive circuit 31 may be the current value of the current flowing through the drive circuit 31. As an example, the current value of the current flowing through the drive circuit 31 may include at least one of the current values of the output AC current of the U-phase, V-phase, and W-phase legs of the drive circuit 31. In this case, the abnormality of the drive circuit 31 is a current abnormality. The control circuit 35 may detect the current abnormality in response to the current value of the current flowing through the drive circuit 31 detected by the state detection circuit 32 exceeding a predetermined current value. As another example, the current value of the current flowing through the drive circuit 31 may include the current value of the DC current flowing between the converter circuit 311 and the inverter circuit 312 of the drive circuit 31. In this case, the control circuit 35 may determine that a current abnormality has occurred in the drive circuit 31 if the current value of the DC current flowing between the converter circuit 311 and the inverter circuit 312 of the drive circuit 31 exceeds a predetermined current value. When the control circuit 35 determines that a current abnormality has occurred in the drive circuit 31 (i.e., when a current abnormality in the drive circuit 31 is detected), it may stop or limit the operation of the drive circuit 31.

For example, the state of the compressor 4 may include at least one of the phase current of the compressor 4 and the rotation speed of the motor 42 of the compressor 4. The current value of the phase current of the compressor 4 may include the current values of the U-phase, V-phase, and W-phase currents. In this case, the abnormality of the compressor 4 may include an abnormality related to a layer short of the compressor 4. An abnormality related to a layer short of the compressor 4 may include the layer short of the compressor 4 itself, an abnormality that may cause a layer short of the compressor 4, and an abnormality that may be caused by a layer short of the compressor 4. Specific examples of abnormalities related to a layer short of the compressor 4 include a layer short of the compressor 4, a leakage current of the compressor 4, and an open-phase operation of the compressor 4. When an imbalance occurs in the phase currents of the compressor 4, an abnormality related to a layer short of the compressor 4 may occur. The control circuit 35 may determine whether an abnormality of the compressor 4 has occurred based on the state of the compressor 4 detected by the state detection circuit 32. For example, if an imbalance in the phase currents of the compressor 4 occurs, the control circuit 35 may determine that an abnormality related to a layer short in the compressor 4 has occurred. Also, if a deviation in the rotation speed of the motor 42 of the compressor 4 occurs, there is a possibility that an abnormality related to a layer short in the compressor 4 has occurred. When the control circuit 35 determines that an abnormality related to a layer short has occurred in the compressor 4 (i.e., when an abnormality related to a layer short in the compressor 4 is detected), it may stop or limit the operation of the drive circuit 31.

In one variation, the power source 10 may be any of a variety of AC power sources, particularly a commercial power source. Although the voltage and frequency of the commercial power source vary depending on the country, the drive circuit 31 may be configured to be capable of driving the electric motor 42 using any of a variety of commercial power sources.

In one modified example, the drive circuit 31 can be configured to supply AC output power corresponding to the type of the electric motor 42, etc. The AC output power is not limited to three-phase AC power, and can be single-phase AC power.

In one modified example, the converter circuit 311 may have a plurality of third output points. The plurality of third output points may output different voltages. The inverter circuit 312 may have a plurality of third semiconductor switching element groups respectively connected between the plurality of third output points and the motor 42. If the total number of the first output point P1, the second output point P2, and the plurality of third output points P3 is n, the drive circuit 31 can provide a voltage of (2×n-1) levels. By increasing n, the voltage waveform applied to the motor 42 by the drive circuit 31 can be made closer to a sine wave.

In one modified example, the circuit configuration of the inverter circuit 312 is not limited to the circuit configuration in FIG. 2. The circuit configuration of the inverter circuit 312 in FIG. 2 is a so-called NPC (Neutral-Point-Clamped) type, but may be an A-NPC (Advanced-NPC) type. The inverter circuit 312 only needs to have a plurality of semiconductor switching element groups that are respectively connected between a plurality of output points with different voltages and the electric motor. The plurality of semiconductor switching elements that make up the plurality of semiconductor switching element groups may include semiconductor switching elements that are included in common to two or more semiconductor switching element groups.

In one modified example, the refrigeration cycle device is not limited to an air conditioner (so-called room air conditioner (RAC)) configured with one indoor unit connected to one outdoor unit. The refrigeration cycle device may be an air conditioner (so-called package air conditioner (PAC), building multi air conditioner (VRF)) configured with multiple indoor units connected to one or multiple outdoor units. Alternatively, the refrigeration cycle device is not limited to an air conditioner, and may be a refrigeration or cooling device such as a refrigerator or freezer.

In one variant, the abnormality notifications such as the first to third abnormality notifications may be issued directly or indirectly. Direct issuing is when the air conditioner outputs the abnormality notification directly using the outdoor unit 1a, indoor unit 1b, or remote controller, etc. For example, the abnormality notification may be output using light from a light source device (LED, red light, warning indicator lamp, etc.) provided on the outdoor unit 1a, indoor unit 1b, or remote controller of the air conditioner, sound from a sound generating device (speaker, buzzer, alarm, sound generator, alarm, etc.), or visual display (message display, backlight flashing, etc.) by a display device (display, display panel, etc.). Indirect issuing is when the abnormality notification is output and/or stored outside the air conditioner via a communication network such as the Internet or a server. Indirect notifications include push notifications (notifications to mobile phones and smartphones), notifications to voice assistants (Alexa Echo, Google Home, etc.), automatic notifications to manufacturers or maintenance companies, sending messages to monitoring equipment of management companies, notifications to service centers, etc., notifications to fire engines or security companies, and saving the abnormality history in a storage device.

In one modified example, the control device 3 may acquire various index values (state values) when diagnosing an abnormality in the refrigeration cycle circuit 2. For example, index values used in diagnosing an abnormality in the refrigeration cycle circuit 2 include suction pressure/evaporation saturation temperature, discharge pressure/condensation saturation temperature, suction gas refrigerant temperature, discharge gas refrigerant temperature, condenser outlet refrigerant temperature, evaporator inlet refrigerant temperature, evaporator outlet refrigerant temperature, load side blown air temperature, receiver liquid level, number of discharge precursor detections, number of state switches of the discharge device 36, number of warnings issued, number of operation restrictions, and number of operation stops. The results of the diagnosis by the control device 3 are preferably stored in the internal memory of the control device 3 or an external server or the like for a predetermined period (e.g., 1 to 3 years) or more. Similarly, the history of abnormality notifications by the control device 3 is preferably stored in the internal memory of the control device 3 or an external server or the like for a predetermined period (e.g., 1 to 3 years) or more.

3. Aspects
As is apparent from the above embodiment and modifications, the present disclosure includes the following aspects.

[Aspect 1]
A control device for controlling a compressor of a refrigeration cycle circuit in which a working medium circulates,
The control device includes:
A drive circuit for driving the compressor;
a discharge device capable of switching between a first state in which a connection line between the drive circuit and the compressor is separated from a reference potential and a second state in which the connection line is connected to the reference potential;
Equipped with
Control device.

[Aspect 2]
The reference potential exists outside the drive circuit.
The control device of aspect 1.

[Aspect 3]
The reference potential is provided by ground.
The control device of aspect 2.

[Aspect 4]
A control circuit for controlling the drive circuit and the discharge device is further provided.
The control circuit stops the operation of the drive circuit and switches the discharge device to the second state in response to detection of an abnormality in at least one of the compressor and the drive circuit.
The control device according to any one of aspects 1 to 3.

[Aspect 5]
The control circuit switches the discharge device to the first state when the stop of the operation of the drive circuit is released.
The control device of aspect 4.

[Aspect 6]
The discharge device includes a series circuit of a switch and a resistor,
the series circuit is connected between the connection line and the reference potential;
the first state is a state in which the switch is off,
The second state is a state in which the switch is on.
The control device according to any one of aspects 1 to 5.

[Aspect 7]
The resistance value of the resistor is 1 kΩ or less.
The control device of aspect 6.

[Aspect 8]
the connection lines include a plurality of connection lines respectively corresponding to three phases of AC output power,
The discharge device has a plurality of the series circuits respectively connected between the plurality of connection lines and the reference potential.
The control device according to any one of aspects 4 to 7.

[Aspect 9]
A state detection circuit for detecting a state of at least one of the compressor and the drive circuit is further provided,
the drive circuit includes a converter circuit that outputs DC output power based on input power from a power source so that a voltage of the DC output power becomes a first voltage, and an inverter circuit that outputs AC output power to the compressor based on the DC output power,
the state detection circuit detects the DC output power and outputs a detection voltage indicative of a voltage of the DC output power;
When the detection voltage becomes less than a second voltage that is equal to or less than the first voltage, the control circuit stops the operation of the drive circuit and switches the discharge device to the second state.
The control device of aspect 4 or 5.

[Aspect 10]
The second voltage is 0.3 to 0.8 times the first voltage.
The control device of aspect 9.

[Aspect 11]
The compressor includes:
A sealed container that forms a flow path of the working medium;
a compression mechanism located within the sealed container and configured to compress the working medium;
an electric motor located within the sealed container for operating the compression mechanism;
Equipped with
The inverter circuit outputs the AC output power to the electric motor,
The connecting line is between the inverter circuit and the electric motor.
The control device according to any one of aspects 1 to 10.

[Aspect 12]
the compressor is connected to a connection line between a compressor of a refrigeration cycle circuit in which a working medium circulates and a drive circuit that drives the compressor, and is configured to be switchable between a first state in which the connection line is separated from a reference potential and a second state in which the connection line is connected to the reference potential;
Discharge device.

[Aspect 13]
A control device according to any one of aspects 1 to 11;
The refrigeration cycle circuit;
Equipped with
Refrigeration cycle equipment.

[Aspect 14]
The working medium comprises an ethylene-based fluoroolefin;
The refrigeration cycle apparatus of aspect 13.

[Aspect 15]
The ethylenic fluoroolefin is 1,1,2-trifluoroethylene, trans-1,2-difluoroethylene, cis-1,2-difluoroethylene, 1,1-difluoroethylene, tetrafluoroethylene, or monofluoroethylene;
The refrigeration cycle apparatus of aspect 14.

[Aspect 16]
The working medium further comprises difluoromethane.
The refrigeration cycle apparatus of aspect 14.

[Aspect 17]
The working medium further comprises a saturated hydrocarbon.
The refrigeration cycle apparatus of aspect 14.

[Aspect 18]
The working fluid contains a haloalkane having 1 or 2 carbon atoms as a disproportionation inhibitor for suppressing the disproportionation reaction of the ethylenic fluoroolefin.
The refrigeration cycle apparatus of aspect 14.

[Aspect 19]
The saturated hydrocarbons include n-propane.
The refrigeration cycle apparatus of aspect 17.

[Aspect 20]
A control method executed by a control device that controls a compressor of a refrigeration cycle circuit in which a working medium circulates, comprising:
The control device includes:
A drive circuit for driving the compressor;
a discharge device capable of switching between a first state in which a connection line between the drive circuit and the compressor is separated from a reference potential and a second state in which the connection line is connected to the reference potential;
Equipped with
The control method includes stopping the operation of the drive circuit and switching the discharge device to the second state in response to detection of an abnormality in at least one of the compressor and the drive circuit.
Control methods.

[Aspect 21]
A program executed by a computer system provided in a control device that controls a compressor of a refrigeration cycle circuit in which a working medium circulates,
The control device includes:
A drive circuit for driving the compressor;
a discharge device capable of switching between a first state in which a connection line between the drive circuit and the compressor is separated from a reference potential and a second state in which the connection line is connected to the reference potential;
Equipped with
The program causes the computer system to stop operation of the drive circuit and switch the discharge device to the second state in response to detection of an abnormality in at least one of the compressor and the drive circuit.
program.

Aspects 2 to 11 and aspects 14 to 19 are optional elements and are not required. Aspects 2 to 11 and aspects 14 to 19 can be appropriately combined with aspect 12, 20, or 21.

The present disclosure is applicable to a control device, a discharge device, a refrigeration cycle device, a control method, and a program. Specifically, the present disclosure is applicable to a control device for a refrigeration cycle circuit in which the working medium contains an ethylene-based fluoroolefin as a refrigerant component, a discharge device, a refrigeration cycle device including the refrigeration cycle circuit and the control device, a control method executed by the control device, and a program (computer program) used in the control device.

REFRIGERATION CYCLE DEVICE 2 REFRIGERATION CYCLE CIRCUIT 3 CONTROL DEVICE 4 COMPRESSOR 10 POWER SUPPLY 20 WORKING MEDIUM 31 DRIVE CIRCUIT 32 STATUS DETECTION CIRCUIT 35 CONTROL CIRCUIT 36 DISCHARGE DEVICE 361, 362, 363 SERIAL CIRCUIT SW31, SW32, SW33 SWITCH R31, R32, R33 RESISTOR 40 ENCLOSED CONTAINER 41 COMPRESSION MECHANISM 42 ELECTRIC MOTOR 311 CONVERTER CIRCUIT 312 INVERTER CIRCUIT Lu, Lv, Lw CONNECTION WIRE

Claims (20)

A control device for controlling a compressor of a refrigeration cycle circuit in which a working medium circulates,
The control device includes:
A drive circuit for driving the compressor;
a discharge device connected to a connection line between the drive circuit and the compressor and switchable between a first state in which the connection line is separated from a reference potential and a second state in which the connection line is connected to the reference potential;
Equipped with
Control device. The reference potential exists outside the drive circuit.
The control device of claim 1. The reference potential is provided by ground.
The control device of claim 2. A control circuit for controlling the drive circuit and the discharge device is further provided.
The control circuit stops the operation of the drive circuit and switches the discharge device to the second state in response to detection of an abnormality in at least one of the compressor and the drive circuit.
The control device of claim 1. The control circuit switches the discharge device to the first state when the stop of the operation of the drive circuit is released.
The control device of claim 4. The discharge device includes a series circuit of a switch and a resistor,
the series circuit is connected between the connection line and the reference potential;
the first state is a state in which the switch is off,
The second state is a state in which the switch is on.
The control device of claim 1. The resistance value of the resistor is 1 kΩ or less.
The control device of claim 6. the connection lines include a plurality of connection lines respectively corresponding to three phases of AC output power,
The discharge device has a plurality of the series circuits respectively connected between the plurality of connection lines and the reference potential.
The control device of claim 6. a state detection circuit for detecting a state of at least one of the compressor and the drive circuit,
the drive circuit includes a converter circuit that outputs DC output power based on input power from a power source so that a voltage of the DC output power becomes a first voltage, and an inverter circuit that outputs AC output power to the compressor based on the DC output power,
the state detection circuit detects the DC output power and outputs a detection voltage indicative of a voltage of the DC output power;
When the detection voltage becomes less than a second voltage that is equal to or less than the first voltage, the control circuit stops the operation of the drive circuit and switches the discharge device to the second state.
The control device of claim 4. The second voltage is 0.3 to 0.8 times the first voltage.
The control device of claim 9. the compressor is connected to a connection line between a compressor of a refrigeration cycle circuit in which a working medium circulates and a drive circuit that drives the compressor, and is configured to be switchable between a first state in which the connection line is separated from a reference potential and a second state in which the connection line is connected to the reference potential;
Discharge device. A control device according to any one of claims 1 to 10;
The refrigeration cycle circuit;
Equipped with
Refrigeration cycle equipment. The working medium comprises an ethylene-based fluoroolefin;
The refrigeration cycle apparatus of claim 12. The ethylenic fluoroolefin is 1,1,2-trifluoroethylene, trans-1,2-difluoroethylene, cis-1,2-difluoroethylene, 1,1-difluoroethylene, tetrafluoroethylene, or monofluoroethylene;
The refrigeration cycle apparatus of claim 13. The working medium further comprises difluoromethane.
The refrigeration cycle apparatus of claim 12. The working medium further comprises a saturated hydrocarbon.
The refrigeration cycle apparatus of claim 12. The working fluid contains a haloalkane having 1 or 2 carbon atoms as a disproportionation inhibitor for suppressing the disproportionation reaction of the ethylenic fluoroolefin.
The refrigeration cycle apparatus of claim 13. The saturated hydrocarbons include n-propane.
The refrigeration cycle apparatus of claim 16. A control method executed by a control device that controls a compressor of a refrigeration cycle circuit in which a working medium circulates, comprising:
The control device includes:
A drive circuit for driving the compressor;
a discharge device connected to a connection line between the drive circuit and the compressor and switchable between a first state in which the connection line is separated from a reference potential and a second state in which the connection line is connected to the reference potential;
Equipped with
The control method includes stopping the operation of the drive circuit and switching the discharge device to the second state in response to detection of an abnormality in at least one of the compressor and the drive circuit.
Control methods. A program executed by a computer system provided in a control device that controls a compressor of a refrigeration cycle circuit in which a working medium circulates,
The control device includes:
A drive circuit for driving the compressor;
a discharge device connected to a connection line between the drive circuit and the compressor and switchable between a first state in which the connection line is separated from a reference potential and a second state in which the connection line is connected to the reference potential;
Equipped with
The program causes the computer system to stop operation of the drive circuit and switch the discharge device to the second state in response to detection of an abnormality in at least one of the compressor and the drive circuit.
program.

Images