CN100538220C - cooling device and control method - Google Patents

Abstract

The present invention relates to a cooling device (1) and a control method thereof, which avoid an unexpected stall of the motor of a variable speed compressor (2) performing a refrigeration cycle, caused by overheating or by being unable to respond to a thermal dynamic load caused by heavy operating loads, such as high ambient temperatures or frequent opening or closing of doors, by means of a control method performed by a control card (5).

Description

Cooling device and control method

technical field

The present invention relates to a cooling device comprising a compressor that functions efficiently under heavy operating loads.

Background technique

In cooling installations, the selection of the compressors in the cooling system takes into account the extreme operating conditions according to the climate zone, so the capacity of the compressors can be larger than required, because the maximum possible operating load must be taken into account. A compressor with a capacity greater than required may result in an increased number of starts-stops and increased cycle losses. To overcome this, compressor selection is made based on actual operating conditions that span a greater portion of the compressor's expected life, and the speed of the compressor, that is, the rotational speed of the compressor motor (rpm ) changes in some cases, at this time the cooling device should work under extreme conditions. Various control algorithms have been devised in chillers using variable speed compressor motors to determine when the compressor should be operating at normal speed and when it should be operating at a higher speed. When the cooling unit is operating under heavy operating conditions, such as high ambient temperature or frequent opening and closing of its door, the compressor speed is accelerated with the help of an electronic card. In this case, the compressor is fed by means of an electronics card rather than a network power supply. From time to time there may be overheating or stall, causing an unforeseen stall in the compressor fed through the electronics pack due to the inability to respond to the thermodynamic load under heavy operating conditions. When the compressor starts running after a stall, the disconnection situation is repeated continuously due to algorithmic requirements, and frequent compressor disconnection results in reduced efficiency.

In US Pat. No. 6,231,306, a gas turbine engine includes means for sensing a compressor stall, evaluating a signal received from the sensor, and comparing the sensed signal with a predetermined threshold indicative of a healthy compressor, and Used to provide a processed signal indicating an impending stall condition.

In US Pat. No. 6,532,433, in a method for monitoring and controlling a compressor, at least one compressor operating parameter is monitored in order to obtain time-series data, and the time-series data is filtered by means of a Kalman filter. As a result of this monitoring method, a precursor to compressor stall under heavy load is detected between compressor stalls.

In British Patent GB2292847, in a single phase induction motor utilizing a compressor, a current detector detects stalling of the motor under high load, and a relay cuts power from the capacitor.

In the British patent GB1109346, in the refrigeration compressor, the starting device functions to maintain the excitation of the auxiliary winding after the motor is started, so as to overcome the extreme starting torque of the compressor for a long time, thereby ensuring the running torque of the compressor ( running torque) will drop to a value lower than the normal stalling torque of the motor.

Contents of the invention

The object of the present invention is to realize a cooling device and a control method in which unforeseen successive stalls of the compressor are avoided.

Cooling device and control method In order to obtain the object of the present invention, the motor electronics module enables the operation of the compressor motor at high loads and high speeds, during start and stop phases, and under the command of the thermostat.

The compressor is fed by the network for a period of time at each start and the compressor motor functions at a constant speed as the compressor continues to run in successive stop and start phases. Thus, the electronic circuits controlling the speed of the motor are protected against high currents drawn at start-up.

While the compressor is running, due to overheating before the thermostat generates a stop command, the thermal protector sensing the motor temperature cuts off the feed current to stop the compressor.

Because the thermal protector shuts off the electrical current, if the electronic pack detects that the compressor has stalled, it can be concluded that this is an unexpected stall condition caused by a heavy load condition.

When the compressor is ready to start running again, a predetermined waiting period is consumed before starting so that the stall does not repeat, and due to the reduction of the pressure imbalance between the suction and compression parts of the compressor during this period, The compressor can be started more easily after this stop phase.

When the compressor starts running after waiting a certain period of time, it is fed by the network power supply, resulting in a running period with constant speed which is longer than when it starts running with a signal from the thermostat.

When the compressor is running after an unforeseen stall phase, the opening of the thermal protector should be detected immediately, so using a separate thermal sensor that detects the temperature of the thermal protector is essential for transmitting the thermal protector data to the electronics. Plugins are helpful.

Description of drawings

The cooling device and control method used to achieve the objects of the present invention are shown in the accompanying drawings, in which,

Figure 1 is a schematic diagram of the cooling device.

Fig. 2 is a flow chart of the control method.

Fig. 3 is the speed-time graph and temperature-time graph of the operation of the compressor of the cooling device.

The components shown in the figure are labeled as follows:

1. Cooling device

2. Compressor

3. Thermal protector

4. Thermostat

5. Electronic plug-in

6. Thermal protector thermal sensor

Detailed ways

The cooling device 1 includes a variable-speed compressor 2 for performing a refrigeration cycle; a thermal protector 3 that detects the temperature of the compressor 2, turns on when the value is higher than a preset temperature, and turns off Current I, so as to stop the operation of the compressor 2, and the thermal protector 3 closes when the value is lower than the preset temperature, so as to provide the restart of the compressor 2; a command to disconnect; and the electronics module 5, which provides the execution of the algorithm that controls the operating speed of the compressor 2 and the duration of the start-stop.

As the compressor performs its normal operation in successive start-stop phases (T-on, T-off), the start-stop phase is controlled by a thermostat in each pass from the T-off phase to the T-on phase. 4's on and off commands, since a high current I will be generated each time the compressor 2 is started, the current I required by the motor is directly obtained from the network power supply within a predetermined period of time T1 to protect the electronic plug-in 5, and during this period T1, the compressor 2 operates at a constant speed Vo. When the period T1 ends, the compressor 2 starts running at a variable speed different from the constant speed Vo, such as a higher speed V1 , by feeding power through the electronic card 5, so as to provide the required cooling (Fig. 3).

When the compressor 2 is running, the current I passes through the thermal protector 3 and reaches the motor of the compressor 2 . The thermal protector 3 is placed in the electrical connection box on the casing of the compressor 2, and is turned on or off according to changes in ambient temperature. The thermal protector 3 opens when the temperature is higher than a preset value, thereby shutting off the current I from the network power supply to the motor of the compressor 2, and closes when the temperature is lower than a preset value, thereby allowing the current I from the network power supply to reach the compressor 2 motors. When the motor of the compressor 2 is overheated, the thermal protector 3 turns off the current I, thereby stopping the compressor 2 and protecting the electronic module 5 .

In the case where the thermal protector 3 turns off the current I so that the compressor 2 is stopped without receiving an off command from the thermostat 4, the current I is not supplied to the compressor 2 within the preset pause period T2, thereby This allows the pressure in the refrigeration system to be equalized and does not take into account any switch-on commands that may be generated by the thermostat 4 during this period. When the period T2 ends, the compressor 2 is started with the current I supplied independently from the thermostat 4 . After starting, the compressor 2 runs at a constant speed Vo for a period T3 which is longer than the period T1 in which the compressor 2 runs at a constant speed Vo and is fed by means of a current I from the network supply. Electricity, network power is applied at each first start, after which a current I is supplied through the electronics pack 5 and it runs at speed V1. When the compressor 2 is running at the speed Vo or V1, if an off command is received from the thermostat 4, this command is executed, thereby starting the T-off phase.

The control method of the cooling device 1 for avoiding repeated and unforeseen stalls of the compressor 2 consists of the following steps:

-Compressor 2 starts to run 100 under the connection command of thermostat 4

- Compressor 2 runs 101 at constant speed Vo at startup and during period T1

- After the time period T1 is completed, the current I is supplied through the electronic card 5 and the compressor 2 is run 102 at the speed V1

- regardless of whether the thermal protector 3 has closed the current I, the thermal protector 3 is controlled 103

- If the thermal protector 3 has not yet closed the current I, then enter step 106 in which the thermostat 4 is controlled regardless of whether the thermostat 4 has generated a disconnection command

- If the thermal protector 3 has switched off the current I, then pause for a time period T2 104 without supplying the current I to the compressor 2

- Compressor 2 is operated at constant speed Vo for a period T3 longer than the period T1105 during which the current I is supplied by the network power supply

- The thermostat 4 is controlled 106 regardless of whether the thermostat 4 has generated an opening command

- If the thermostat 4 has not generated a disconnect command, then return to step 102 where the compressor 2 runs at speed V1

- If the thermostat 4 has generated an off command, the compressor 2 starts an off period T-off 107 .

In one embodiment of the invention, the cooling device 1 comprises a thermal protector thermal sensor 6 which detects the temperature of the thermal protector 3 . The thermal protector thermal sensor 6 detects whether the temperature of the thermal protector 3 is lower than a preset value, at which the thermal protector 3 is turned off, and the thermal protector 3 thus allows the flow of current I. When the thermal protector 3 stops the compressor 2 by turning off the current I, if the temperature drops back to a normal value at the end of the pause period T2, the thermal protector 3 is closed, allowing the current I to flow, and the electronic package 5 is in the thermal protector 3 Run compressor 2 either immediately or later after shutdown following data received from thermal protector thermal sensor 6.

With the method performed by the control of the cooling device 1 using the electronic card 5, the repetition of stalls is avoided in the trial start after the unforeseen stall of the compressor 2, and the trial start after the unforeseen stall can be successful.

In the embodiment of the present invention, without the need to measure and evaluate various parameters of the compressor 2, the unpredictable stall of the compressor 2 can be avoided by implementing a simple control method, and an effective performance, so as to obtain the required cooling value in the cooling device 1 under high-intensity working load, such as high ambient temperature or frequent opening and closing of the door of the cooling device 1 .

Claims (4)

1. A cooling device (1) comprising a variable speed compressor (2) providing refrigeration cycle performance; a thermal protector (3) detecting the temperature of said compressor (2); A thermostat (4) generating on and off commands for the compressor (2) during the stop phase, characterized by having an electronic insert (5) which, without taking into account the In case of an on command generated by the thermostat (4), no current (I) is supplied to the compressor (2) for a preset second period of time (T2), when the thermal protector (3) is closed current (I), the compressor (2) is stopped when the compressor (2) is running without receiving an off command from the thermostat (4), and the electronic The plug (5) activates the compressor (2) at the end of the second period (T2) with the current (I) supplied independently from the thermostat (4), and after activation, The compressor (2) is run at a constant speed (Vo) for a third period (T3) longer than the first period (T1) preset for each start. 2. The cooling device (1) as claimed in claim 1, characterized in that, by means of a thermal protector thermal sensor (6) detecting the temperature of the thermal protector (3), the electronic package (5) The compressor (2) can be started immediately or later after the thermal protector (3) is turned off. 3. The control method for the cooling device (1) as claimed in claim 1 or 2, comprising the following steps: the compressor (2) starts running (100) under the connection command of the thermostat (4) ); the compressor (2) operates (101) at a constant speed (Vo) at startup and during the first period (T1); when the first period (T1) ends, the current (I ) is supplied through the electronics card (5) and the compressor (2) runs (102) at a first speed (V1); regardless of whether the thermal protector (3) has shut off the current (I ), the thermal protector (3) is all controlled (103); if the thermal protector (3) has not yet closed the current (I), enter into no matter whether the thermostat (4) has produced the disconnection command , the step (106) in which the thermostats (4) are all controlled; if the thermal protector (3) has closed the current (I), then no current (I) is supplied to the compressor ( 2), suspend a second period (T2) (104); the compressor (2) runs at a constant speed (Vo) for a third period (T3), and the third period (T3) is longer than A first period (T1) (105) of current (I) being supplied by network power; regardless of whether the thermostat (4) has generated said opening command, said thermostat (4) is controlled (106); if If the thermostat (4) has not generated the disconnect command, then return to the step (102) of the compressor (2) running at the first speed (V1); if the thermostat (4) has generated the Off command, then the compressor (2) starts the off phase (T-off) (107). 4. The control method according to claim 3, characterized in that, the second period (T2) of stopping after the thermal protector (3) shuts off the current (I) is different from the period required to balance the pressure in the cooling system same length.

Images