CN1086795C - Inverter for air conditioner and air conditioner thereof - Google Patents

Abstract

To provide an inverter device for an air conditioner that can reliably reduce high-frequency leakage current even when the switching frequency is high, thereby improving the capacity of a compressor and obtaining a sufficient air-conditioning capacity. In addition, according to this device, the high-frequency leakage current _I1 flowing from the compressor motor 12 to the ground is detected, a current _I2 having a waveform similar to the detected high-frequency leakage current is formed, and the formed current _I2 passes through the The high-frequency leakage current _I1 compulsorily cancels out.

Description

Inverter device for air conditioner and air conditioner

The present invention relates to an air conditioner inverter device that handles high frequency leakage current from a compressor motor to ground.

The air conditioner is equipped with an inverter unit for driving the compressor motor.

The inverter device includes a rectification circuit for rectifying a commercial AC power supply voltage, and a switching circuit for converting the voltage rectified by the rectification circuit into a high-frequency voltage via a switch. The output of this switching circuit is used as drive power and supplied to the compressor motor.

The compressor motor and the compressor part are housed together in the compressor casing, and the compressor casing is grounded for safety.

There is an electrostatic capacitance between the winding of the compressor motor and its casing (ie, ground), and a high-frequency leakage current of several MHz flows from the compressor motor to the ground through the electrostatic capacitance when a switch in the inverter device is driven.

This high-frequency leakage current propagates to the commercial AC power supply by induction, which adversely affects the drive control of the inverter device, and may cause malfunctions of other home appliances and circuit breakers.

In order to reduce this high-frequency leakage current, countermeasures such as installing a choke coil between the output terminal of the inverter unit and the compressor motor wiring, or reducing the switching frequency of the inverter unit itself can be taken.

However, even if a choke coil is provided to reduce high-frequency leakage current, a sufficient reduction effect cannot be obtained when the switching frequency of the inverter device is increased.

If it is said that reducing the switching frequency of the inverter device, the capacity of the compressor cannot be improved, and the capacity of the air conditioner is not enough.

Also, in the case of using liquid fluorocarbons instead of HCFC22 (CHCIF ₂ ), which has been used in the past as a refrigerant that is highly damaging to the ozone layer, especially HFC32 (CH ₂ F ₂ ) and HFC125 (CHF ₂ CF ₃ ) , Due to poor electrical insulation and high dielectric constant, the above-mentioned leakage current increases.

The present invention considers the above situation, and its purpose is to reliably reduce the high-frequency leakage current when the switching frequency is high, and when HFC32 and HFC125 are used instead of HCFC refrigerants, so that the compressor can also be improved. capacity, but also to be able to obtain sufficient air-conditioning capacity.

The inverter device of the air conditioner of the first invention, the air conditioner is equipped with: a compressor; a compressor motor for driving the compressor; a rectification circuit for rectifying the voltage of a commercial AC power supply; A switch circuit that converts the voltage rectified by the rectifier circuit into a high-frequency voltage and outputs the high-frequency voltage as drive power supplied to the compressor motor, and a zero-phase current provided on the rear of the rectifier circuit The detector uses a current similar to the high-frequency leakage current detected by the zero-phase current detector flowing from the compressor motor to the ground as a current canceling circuit formed to cancel the leakage current; the above-mentioned The output terminal of the current cancellation circuit is grounded.

An inverter device for an air conditioner according to a second invention, the air conditioner is equipped with: a compressor; a compressor motor for driving the compressor; a rectifier circuit for rectifying the voltage of a commercial AC power supply; A switch circuit that converts the voltage rectified by the rectifier circuit into a high-frequency voltage, and outputs the high-frequency voltage as the drive power supplied to the compressor motor, and a low-frequency filter provided at the rear of the rectifier circuit passes through The above-mentioned low-frequency filter detects the high-frequency leakage current flowing from the compressor motor to the ground, and uses the current similar to the waveform of the detected high-frequency leakage current as a current offset circuit formed for offsetting the leakage current; the current offset circuit The output is grounded.

The inverter device of the air conditioner of the third invention is in the second invention. First, the low-frequency filter is composed of the electrostatic capacitance existing between the pair of lines and the pair of coils mounted on the magnetic core and inserted into the two lines. Inductance constitutes. Furthermore, the current cancellation circuit has: a coil for detection mounted on the magnetic core of the low-frequency filter; and an amplifying circuit for amplifying the voltage generated on the coil for detection; Frequency leakage current detection uses a current similar in waveform to the detected high-frequency leakage current as a countermeasure against the leakage current, and is formed by means of an amplifier circuit.

The inverter device of the air conditioner according to the fourth invention is in the second invention. First, the low-frequency filter is composed of the electrostatic capacitance existing between the pair of lines and the pair of coils mounted on the magnetic core and inserted into the two lines. Inductance constitutes. Furthermore, the current cancellation circuit has: a coil for detection installed on the magnetic core of the low-frequency filter, and an amplifier circuit that uses a pair of transistors to perform class A push-pull amplification of the voltage generated on the coil for detection; The high-frequency leakage current flowing from the compressor motor to the ground is detected, and a current having a waveform similar to the detected high-frequency leakage current is used to cancel the leakage current, and is formed by means of an amplifier circuit.

The inverter device of the air conditioner of the fifth invention is in the second invention. First, the low-frequency filter is composed of the electrostatic capacitance existing between the pair of lines and the pair of coils mounted on the magnetic core and inserted into the two lines. Inductance constitutes. Furthermore, the current cancellation circuit has: a pair of detection coils installed on the magnetic core of the low-frequency filter and an amplifying circuit for amplifying the voltage generated on each detection coil by means of corresponding transistors; Detect the high-frequency leakage current flowing from the compressor motor to the ground, and use the current with a waveform similar to the detected high-frequency leakage current to cancel the leakage current, and form it by means of an amplifier circuit.

The inverter device of the air conditioner according to the sixth invention is that in any one of the first to fifth inventions, a drive control circuit for driving and controlling the switch circuit is provided, and the drive control circuit is combined with the amplifier of the switch circuit and the current canceling circuit. Circuits are integrated together.

In the air conditioner of the seventh invention, liquid fluorocarbon is used as the refrigerant of the air conditioner, and the compressor is driven by the inverter device of the first invention.

Fig. 1 is a block diagram showing the configuration of the control circuit of the first embodiment;

Fig. 2 is a figure showing the high-frequency leakage current _I waveform in each embodiment;

Fig. 3 is a diagram showing the _waveform of the offset current I in each embodiment;

Fig. 4 is a diagram showing the waveform of current _I3 flowing in the ground through the canceling effect of various embodiments;

Fig. 5 is a block diagram showing the configuration of the control circuit of the second embodiment;

Fig. 6 is a block diagram showing the configuration of the control circuit of the third embodiment;

Fig. 7 is a block diagram showing the configuration of the control circuit of the fourth embodiment;

Fig. 8 is a refrigerating cycle diagram of the air conditioner in each embodiment. 1-Commercial AC power supply 2-Low frequency filter 5-Rectifier circuit 7-Low frequency filter 8-Magnetic core 9-Coil 10-Filter capacitor 11-Switch circuit 12-Compressor motor 13-Winding 14-Compressor shell 20 - Part control 23-Drive control circuit 30-Current offset circuit 31-Coil for detection 32-NPN transistor 33-PNP transistor

As shown in Fig. 8, as a refrigeration cycle of an air conditioner, a compressor, a condenser, a pressure reducing device (expansion valve, capillary tube, etc.), and an evaporator are sequentially connected through refrigerant piping. Furthermore, HFC32 and HFC125, which have low electrical insulation, are enclosed in the refrigerant of the refrigeration cycle at a weight ratio of about 50%/50% mixed refrigerant.

Next, an inverter device that drives the air conditioner compressor configured in this way will be described.

Next, a first embodiment of the present invention will be described with reference to the drawings.

As shown in FIG. 1 , the rectifier circuit 5 is connected to a commercial AC power supply 1 through a low-frequency filter (also called a line filter) 2 .

The low-frequency filter 2 is composed of choke coils 3, 3 and capacitors 4, 4 to prevent high-frequency noise from propagating to the power supply 1.

The rectifier circuit 5 is composed of a rectifier bridge connected by a bridge type of a plurality of diodes 6, a low-frequency filter 7 connected to the rear portion of the rectifier bridge and a filter capacitor 10 connected to the second low-frequency filter 7 rear portion. The voltage of the AC power source 1 is rectified.

The low-frequency filter 7 is a coil wound on the ferrite core 8 synchronously with copper wires. If the side of the load is considered as the source of noise, the noise current flows through the coil 9a on one side and flows through the coil 9b on the opposite side. The magnetic fields generated by the returning noise currents cancel each other out. Moreover, it is realized by means of such a configuration: high-frequency components are blocked, and only low-frequency components are passed.

The switch circuit 11 is connected to the output terminal of the rectification circuit 5 . The switching circuit 11 is constituted by a plurality of switching elements (for example, power transistors), and converts the voltage rectified by the rectifying circuit 5 into a high-frequency voltage through switches, and outputs it.

A compressor motor 12 is connected to the output of the switching circuit 11 . The compressor motor 12 is a brushless DC motor composed of three phase windings 13 , 13 , 13 , and is housed in a compressor housing 14 together with the compressor part. For safety, the compressor casing 14 is grounded.

In the compressor motor 12 , the graph C represents an electrostatic capacity existing between each winding 13 and the compressor casing (ie, ground) 14 .

On the other hand, 20 is the control part of an air conditioner, and controls the whole air conditioner. To this control section 20 are connected an indoor temperature sensor 21 , a receiving section 22 and a drive control circuit 23 .

The room temperature sensor 21 detects the temperature Ta of the room to be air-conditioned. The receiving unit 22 receives infrared rays emitted from a remote operator (hereinafter, simply referred to as a remote controller) 24 . The remote controller 24 transmits data for setting operating conditions by means of infrared rays.

The drive control circuit 23 performs on-off drive to each power transistor of the switch circuit 11 according to an instruction from the control unit 20, and at the same time controls the cycle of the on-off drive (that is, the switching frequency), and controls the on-period (that is, the switching frequency). , on-off duty cycle, PWM control).

The current cancellation circuit 30 is provided for the inverter device configured in this way.

The current cancellation circuit 30 has: a zero-phase current detector 31 arranged on the rear portion of the diode 6 rectifier bridge, and a pair of transistors 32, 33 of NPN type and PNP type pair the output from the zero-phase current detector 31 Voltage is carried out the amplifying circuit of class A push-pull amplification, is connected between the collector and emitter of transistor 32,33, the diode 34,34 that prevents back electromotive force, and the capacitor 35 that removes DC component; The output device 31 detects the high-frequency leakage current _I1 described later that flows from the compressor motor 14 to the ground, and uses the current _I2 having a waveform similar to the detected high-frequency leakage current _I1 as the offset leakage current and by means of the above-mentioned An amplifier circuit is formed to output the current _I2 through the capacitor 35 mentioned above.

The output terminal of the current cancellation circuit 30 is grounded.

Furthermore, it should be noted that the winding direction of the detection coil is in phase with the coil of the filter 7 . If it is wound in antiphase, the phase deviates from the (common mode) noise current flowing in the power supply, making the current for cancellation flow in antiphase.

Next, the operation of the above configuration will be described.

A desired indoor temperature Ts is set using the remote controller 24, and the running operation is started. Then, the switch circuit 11 is driven by the switch, and the compressor motor 12 is driven by the output of the switch circuit 11 .

At this time, the difference ΔT between the indoor temperature Ta detected by the indoor temperature sensor 21 and the set indoor temperature Ts is obtained, and the switching frequency of the switching circuit 11 is controlled based on the temperature difference ΔT.

When the switching frequency of the switching circuit 11 is changed, the rotational speed of the compressor motor 12 is changed. This change in the rotational speed appears as a change in the capacity of the compressor.

When the temperature difference ΔT becomes zero, the switch drive to the switch circuit 11 is stopped, the compressor motor 12 is stopped, and the operation of the compressor is stopped.

However, along with the switch driving of the switch circuit 11, the several MHz high-frequency leakage current _I1 with a waveform as shown in FIG. C and flow.

This high-frequency leakage current _I1 propagates along the commercial AC power supply by induction, which adversely affects the drive control of the inverter device, and may cause malfunctions of other household products and circuit breakers.

Here, since the high-frequency leakage current I ₁ is proportional to the zero-phase current of the motor winding, the high-frequency leakage current I ₁ can be detected by the zero-phase current detector 31 .

When the high-frequency leakage current _I1 is detected, the transistors 32 and 33 perform class A push-pull amplification on the detected high-frequency leakage current _I1 . As shown in FIG. 3, the canceling current _I2 having a waveform similar to the high-frequency leakage current _I1 is formed by this amplification.

The polarity of the canceling current I ₂ is from the ground to the canceling current circuit 30 , and the high-frequency leakage current I ₁ is absorbed by the current canceling circuit 30 and canceled according to the polarity and waveform. With the help of this cancellation, the current _I3 flowing in the ground becomes a low-level waveform as shown in Figure 4.

In this way, the high-frequency leakage current _I1 is detected, and the canceling current _I2 having a waveform similar to the high-frequency leakage current _I1 is formed, and the high-frequency leakage current _I1 is forcibly canceled by the canceling current _I2 , thereby Therefore, for example, even when the switching frequency of the switching circuit 11 is high, it is possible to reliably reduce the high-frequency leakage current I ₁ .

Therefore, the switching frequency of the switching circuit 11 can be increased as much as possible without adversely affecting the drive control of the inverter device, and there is no need to worry about malfunctioning of other home appliances and circuit breakers. Furthermore, the capacity of the compressor can be sufficiently increased, and sufficient air-conditioning capacity can be obtained.

Next, a second embodiment of the present invention will be described with reference to FIG. 5 . In the second embodiment, the configuration of the current cancellation circuit 30 is different from that of the first embodiment.

That is, in the current cancellation circuit 30 , the detection coil 31A is attached to the ferrite core 8 of the low frequency filter 7 . Other configurations are the same as those of the first embodiment.

In this case, the high-frequency leakage current _I1 is also detected, a canceling current _I2 similar to the waveform of the high-frequency leakage current _I1 is formed, and the high-frequency leakage current _I1 is forcibly suppressed by the canceling current _I2 . offset.

In addition, when detecting the zero-phase current, instead of using a dedicated zero-phase current detector, a coil is installed on the low-frequency filter for noise prevention to detect the zero-phase current. Therefore, it can be realized with a simple structure. Low-cost miniaturization of inverter devices.

Next, a third embodiment of the present invention will be described with reference to FIG. 6 .

In the third embodiment, the configuration of the current cancellation circuit 30 is slightly different from that of the second embodiment.

That is, the current cancellation circuit 30 has: a pair of detection coils 36A, 36B installed on the magnetic core 8 of the low frequency filter 7, and the detection coils 36A, 36B are connected by a pair of corresponding NPN transistors 32, 37 respectively. The amplifying circuit of the voltage amplification generated on 36B is connected to the diodes 34, 34 used to prevent back electromotive force and the capacitor 35 for removing the DC component between the collectors and emitters of transistors 32, 37; The coils 36A, 36B used for the zero-phase current magnitude proportional to the high-frequency leakage current _I1 flowing from the motor 14 to the ground detect positive current and negative current respectively, and the waveform similar to the detected high-frequency leakage current _I1 The current _I2 is used to offset the leakage current and is formed by means of an amplifier circuit, and the current _I2 is output through the capacitor 35.

Other configurations are the same as those of the second embodiment.

In this case, the high-frequency leakage current _I1 is also detected, a canceling current _I2 having a waveform similar to the high-frequency leakage current _I1 is formed, and the high-frequency leakage current _I1 is forcibly suppressed by the canceling current _I2 . to offset.

Just like the second embodiment, even if a complementary push-pull (three sets) circuit for high withstand voltage, high amplification factor, and high frequency is not configured using a small number of PNP transistors, but by using a wide variety of NPN transistors A transistor with the same characteristics can also control the canceling current, and the same effect as that of the first embodiment can be obtained.

Next, a fourth embodiment of the present invention will be described with reference to FIG. 7 .

In the fourth embodiment, an integrated circuit 40 is provided instead of the switch circuit 11 of the first embodiment.

The integrated circuit 40 is composed of a switch circuit part 41 corresponding to the switch circuit 11, a drive control circuit part 42 corresponding to the drive control circuit 23 in the first embodiment, and an amplifying circuit corresponding to the current cancellation circuit 30 in the first embodiment. The amplifier circuit unit 43 is integrated into a single-chip element.

By adopting such an integrated circuit 40, it becomes easy to take measures against heat and insulation, which are important in order to exert the performance of the inverter device, and it is also possible to reduce the installation area of the inverter device in the air conditioner.

In addition, in the current cancellation circuit 30 , adjustment resistors 38 , 38 are inserted into the output line of the detection coil 31 . The adjustment resistors 38 and 38 are used to adjust the current amplification factor hfe of the class A push-pull amplification by the amplifier circuit unit 43 .

By properly selecting the resistance values of the adjustment resistors 38 and 38, for example, the "error" of the class A push-pull amplification current amplification factor hfe can be compared, or the magnitude of the high-frequency leakage current _I1 can be compared to form an optimal level of offset current. I ₂ .

In addition, by using the inverter device shown in the above-mentioned first to fourth embodiments as a driving device for a compressor in an air conditioner, even liquid fluorocarbons such as HFC32 and HFC125 having low electrical insulation Even when the compound is enclosed as a refrigerant in a refrigeration cycle, the leakage current from the compressor can be controlled, and an air conditioner free from the problem of ozone depletion and further high-frequency problems can be provided.

In addition, the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the same gist.

As described above, if according to the inverter device of the air conditioner of the present invention, a high-frequency leakage current flowing from the compressor motor to the ground is detected, a current forming a waveform similar to the detected high-frequency leakage current flows through the The formed current forcibly cancels the high-frequency leakage current, so even in the case of high switching frequency, the high-frequency leakage current can be reliably reduced, so the capacity of the compressor can be improved, and sufficient air-conditioning capacity can be obtained .

Claims (7)

1. An inverter device of an air conditioner, the air conditioner is equipped with: a compressor; a compressor motor (12) for driving the compressor; a rectifier for rectifying the voltage of the commercial AC power supply (1) circuit (5); and for converting the voltage rectified by the rectification circuit (5) into a high-frequency voltage through conversion, and using the high-frequency voltage as the driving power provided to the compressor motor (12) The output switching circuit (11) is characterized in that it is equipped with: A zero-phase current detector (31) arranged on the rear of the rectification circuit (5); A current having a waveform similar to the high-frequency leakage current detected by the zero-phase current detector (31) flowing from the compressor motor (12) to the ground is used as a leakage current cancellation Current offset circuit (30); The output of said current canceling circuit (30) is grounded. 2. An inverter device for an air conditioner, the air conditioner is provided with: a compressor; a compressor motor (12) for driving the compressor; a rectifier for rectifying the voltage of the commercial AC power supply (1) circuit (5); and for converting the voltage rectified by the rectification circuit (5) into a high-frequency voltage through conversion, and using the high-frequency voltage as the driving power provided to the compressor motor (12) The output switching circuit (11) is characterized in that it is equipped with: a low-frequency filter (2) arranged on the rear of the rectification circuit (5); The high-frequency leakage current flowing from the compressor motor (12) to the ground is detected by the low-frequency filter (2), and a current similar to the waveform of the detected high-frequency leakage current is used for leakage current cancellation. The current offset circuit (30); The output of said current canceling circuit (30) is grounded. 3. The inverter device for an air conditioner according to claim 2, wherein: The low-frequency filter is composed of an electrostatic capacitance existing between a pair of lines and an inductance of a pair of coils installed on the magnetic core and plugged into the two lines; The current cancellation circuit has: a detection coil mounted on the magnetic core of the low-frequency filter; and an amplifying circuit for amplifying the voltage generated on the detection coil; The high-frequency leakage current flowing to the ground is detected, and a current having a waveform similar to the detected high-frequency leakage current is used for leakage current cancellation by means of the amplifier circuit. 4. The inverter device for an air conditioner according to claim 2, wherein: The low-frequency filter is composed of an electrostatic capacitance existing between a pair of lines and an inductance of a pair of coils installed on the magnetic core and plugged into the two lines; The current cancellation circuit has: a coil for detection installed on the magnetic core of the low-frequency filter; The high-frequency leakage current flowing from the compressor motor to the ground is detected by the output coil, and a current having a waveform similar to the detected high-frequency leakage current is used to cancel the leakage current by means of the amplifier circuit. 5. The inverter device for an air conditioner according to claim 2, wherein: The low-frequency filter is composed of an electrostatic capacitance existing between a pair of lines and an inductance of a pair of coils installed on the magnetic core and plugged into the two lines; The current cancellation circuit has: a pair of detection coils installed on the magnetic core of the low-frequency filter and an amplifying circuit for amplifying the voltage generated on the detection coils by means of corresponding transistors; Each of the detection coils detects the high-frequency leakage current flowing from the compressor motor to the ground, and the current with a waveform similar to the detected high-frequency leakage current is used for leakage current cancellation by means of the amplifier circuit. form. 6. The inverter device for an air conditioner according to any one of claims 1 to 5, wherein: A drive control circuit for driving and controlling the switch circuit is provided, and the drive control circuit is integrated into an integrated circuit together with the switch circuit and the amplifier circuit of the current cancellation circuit. 7. An air conditioner, in which a liquid fluorocarbon is used as a refrigerant of the air conditioner, wherein the compressor is driven by means of the inverter device as claimed in claim 1.

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