JP2010205034A - Cooling device for electronic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cooling device for an electronic apparatus, capable of cooling the electronic apparatus, even when a power supply suspension state occurs. <P>SOLUTION: An evaporator 21 is disposed on a server rack 10 to the evaporator 21; an electrical heating source unit 30, having a compressor 32 driven by commercial power, is connected via a first refrigerant circuit 18; and a gas engine heat source unit 120, having a compressor 121 driven by a gas engine 127, is connected via a second refrigerant circuit 19. In normal operation, a centralized controller 200 supplies a refrigerant from the electrical heat source unit 30 to the evaporator 21 by switching to the first refrigerant circuit 18, while in the power supply suspension state, the centralized controller supplies the refrigerant from the gas engine heat source unit 120 to the evaporator 21, by switching from the first refrigerant circuit 18 to the second refrigerant circuit 19. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electronic device cooling apparatus for cooling an electronic device.

Conventionally, an air-water heat exchanger is arranged on the air outlet side of a cabinet in which electronic equipment is housed, and the air blown by a fan attached to the electronic equipment housed in the cabinet is cooled by the air-water heat exchanger. There is known an electronic device cooling apparatus that returns the air to the room (for example, see Patent Document 1).
US Patent Application Publication No. 2006/0232945

However, the above-described technique has a problem that, for example, when an electric power supply stop state due to a power failure or the like occurs, the electronic device cannot be cooled.
The present invention has been made in view of the above-described circumstances, and an object thereof is to provide an electronic device cooling apparatus capable of cooling an electronic device even when a power supply stop state occurs.

To achieve the above object, according to the present invention, in an electronic device cooling apparatus, an evaporator is disposed in a cabinet in which an electronic device is stored, and a refrigerant pipe extending from the evaporator is connected to a refrigerant pipe via a first refrigerant circuit. An electric heat source unit having a compressor and a condenser driven by an electric motor using a commercial power source is connected, and a compressor, a generator and a condenser driven by a gas engine are provided via a second refrigerant circuit. A gas engine type heat source unit that drives an auxiliary machine with the generated power of the generator, and includes a switching means for switching between the first and second refrigerant circuits, from the commercial power source to the electric heat source unit. A detecting means for detecting the occurrence of a power supply stop state, and during normal operation, the switching means switches to the first refrigerant circuit to supply the refrigerant from the electric heat source unit to the evaporator; During the force feed stop state, it switches from the first refrigerant circuit to the second refrigerant circuit, and supplying the refrigerant to the evaporator from the gas engine heat source unit.
According to this configuration, when the power supply is stopped, the refrigerant is supplied to the evaporator by driving the gas engine-driven compressor that can be driven without supplying power. For this reason, the electronic device can be cooled even when the power supply is stopped.

Here, in the electronic device cooling apparatus of the above invention, during normal operation, the compressor included in the gas engine type heat source unit is not driven, and the power supply from the commercial power source to the electric type heat source unit is stopped by the detection means. When the occurrence of the state is detected, the driving of the compressor may be started.
According to this configuration, during normal operation, it is possible to reduce costs by not driving the compressor included in the gas engine type heat source unit, and when the power supply is stopped, driving the compressor ensures In addition, the electronic device can be cooled.

  According to the present invention, when the power supply is stopped, the refrigerant is supplied to the evaporator by driving the gas engine-driven compressor that can be driven without supplying power. The equipment can be cooled.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram illustrating a server rack cooling device 100 (electronic device cooling device) according to the present embodiment.
A server room 2 shown in FIG. 1 is a room in which a server rack 10 (cabinet) in which a server 3 (FIG. 2) as an electronic device to be cooled is accommodated is cooled by an air conditioner 1 for indoor cooling. Is done.
The indoor cooling air conditioner 1 includes an outdoor unit (not shown) and an indoor unit 130 installed in a ceiling space. The indoor unit 130 includes an indoor heat exchanger 131 and an indoor fan 132. ing. When the server room 2 is cooled, the indoor cooling air conditioner 1 causes the indoor heat exchanger 131 to function as an evaporator, and a plurality of air conditioners 1 provided on the ceiling via the duct 144 by the negative pressure generated by the indoor fan 132. Air in the room is sucked from (in this embodiment, three) inlets 142, passed through the indoor heat exchanger 131, cooled, and then led to the underfloor space 146 through the duct 145. The air guided to the underfloor space 146 blows out into the room from the air outlet 147 provided on the floor, cools the server room 2, and is then sucked in through the air inlet 142 again. In this way, air circulates between the server room 2 and the indoor unit 130, and the inside of the server room 2 is cooled.

FIG. 2 is a diagram showing the server rack 10.
The server rack 10 includes a cabinet body 11 having an open front surface and a rear surface. A caster 13 is provided at the bottom of the cabinet body 11 so that the server rack 10 can be easily moved.

  In the cabinet main body 11, a plurality of servers 3 are stacked one above the other with their rear surfaces facing the rear surface of the cabinet main body 11. The server 3 is configured by, for example, a blade server and includes a cooling fan 4. When the temperature in the server 3 exceeds a predetermined temperature, the fan 4 is driven to introduce outside air into the server 3. It has a forced air cooling function to discharge from the back of the equipment. For this reason, by arranging the back surface of the server 3 toward the back surface of the cabinet body 11, when the fan 4 is driven, room air is sucked from the cabinet front opening 64 by the fan 4, as indicated by the broken arrow in FIG. After the server 3 is cooled, it passes through the rear door 12 and is discharged into the room. The server 3 is supplied with power from a UPS (uninterruptible power supply) (not shown), and even if the power supply from the commercial power supply 300 (FIG. 3) is stopped, the server 3 and The fan 4 continues to operate.

A rear door 12 is provided on the rear surface of the cabinet body 11 to open and close the rear opening 65 in a single opening so as to be freely closed. By opening the rear door 12, the server 3 in the cabinet body 11 can be accessed. The rear door 12 is configured to be freely ventilated, and an evaporator 21 is disposed therein.
As shown in FIG. 2, the evaporator 21 is configured integrally with the rear door 12 of the server rack 10, extends substantially vertically above and below the rear door 12, and is an upper evaporation portion with a substantially middle portion between the upper and lower sides as a boundary. 22 and the lower evaporator 23, and the upper evaporator 22 is responsible for cooling the upper half of the server 3 in the cabinet body 11, and the lower evaporator 23 is responsible for cooling the lower half of the server 3. . The server rack 10 of this configuration is configured not to include a blower fan, and air heated by the exhaust heat of the server 3 by the fan 4 built in the server 3 circulates through the evaporator 21. For this reason, for example, the depth dimension of the rear door 12 can be shortened and the depth dimension of the server rack 10 itself can be shortened as compared with a configuration in which a blower fan is built in the rear door 12. Note that a blower fan may be arranged in the rear door 12, indoor air may be introduced into the cabinet body 11 by the blower fan, and the air passing through the server 3 may be circulated to the evaporator 21.

The evaporator 21 is configured by a plate fin tube type heat exchanger including a copper tube and an aluminum plate fin, and as shown in FIG. 1, a first copper tube through which a refrigerant from the electric heat source unit 30 flows. 21A and a second copper pipe 21B through which the refrigerant from the gas engine heat source unit 120 flows.
As shown in FIG. 1, the first refrigerant pipe 31 (the first liquid pipe 31 </ b> A and the first gas pipe 31 </ b> B) extending from the electric heat source unit 30 is flexible in the first copper pipe 21 </ b> A of the evaporator 21. The first refrigerant circuit 18 is formed by connecting through pipes (flexible liquid pipe 25 and flexible gas pipe 26).
The second copper pipe 21B of the evaporator 21 includes a second refrigerant pipe 41 (second liquid pipe 41A and second gas pipe 41B) in the gas engine type heat source unit 120 and a flexible pipe (flexible liquid pipe). 42 and the flexible gas pipe 43), whereby the second refrigerant circuit 19 is formed.
In this embodiment, although details will be described later, it is possible to switch between the first copper pipe 21A and the second copper pipe 21B to which the refrigerant flows.

The first refrigerant pipe 31 is routed in the underfloor space between the upper floor 2A and the lower floor 2B of the server room 2, and the flexible liquid pipe 25 and the flexible gas pipe 26 connected to the first refrigerant pipe 31 are Then, it is connected to the evaporator 21 in the rear door 12 through the opening hole 2C (FIG. 2) of the upper floor 2A. For this reason, as shown in FIG. 2, after the flexible liquid pipe 25 and the flexible gas pipe 26 extend downward from the evaporator 21, the flexible liquid pipe 25 and the flexible gas pipe are drawn so as to bend gently in the underfloor space. By giving a margin to the length of the pipe 26, only the flexible liquid pipe 25 and the flexible gas pipe 26 move in accordance with the movement of the rear door 12 when the rear door 12 is opened and closed. Accordingly, no force is applied to the other piping when the rear door 12 is opened and closed, and a steel pipe can be applied to the other piping, for example, the first liquid pipe 31A and the first gas pipe 31B.
The same can be said for the second refrigerant pipe 41.

  As shown in FIG. 1, the electric heat source unit 30 includes a variable capacity compressor 32, a compressor motor 33 (electric motor), an outdoor fan motor 34 that drives an outdoor fan 37, a condenser 35, an expansion valve 36, and a control. A unit 80 is provided. Then, the compressor 32 driven by the compressor motor 33 compresses and discharges the refrigerant filled in the first refrigerant circuit 18, whereby the refrigerant circulates in the first refrigerant circuit 18 and the refrigeration cycle operation. I do. During this refrigeration cycle operation, the air discharged from the server 3 is cooled by the evaporator 21 and discharged into the room.

  On the other hand, the gas engine heat source unit 120 includes a compressor 121, an outdoor heat exchanger 123 (condenser), an expansion valve 124, an outdoor fan motor 126 that drives the outdoor fan 125, a gas engine 127, a generator 128, and a control unit 85. It has. Then, the compressor 121 driven by the gas engine 127 compresses and discharges the refrigerant filled in the second refrigerant circuit 19, whereby the refrigerant circulates in the second refrigerant circuit 19, and circulates and refrigerates. Perform cycle operation. By controlling the rotation speed of the gas engine 127, the refrigeration capacity can be adjusted. The gas engine 127 drives the generator 128 together with the compressor 121. Although the electric power generated by the generator 128 will be described in detail later, the frequency and voltage are adjusted by an inverter (not shown) and the like, and then supplied to each part of the gas engine heat source unit 120. In each part of the second refrigerant circuit 19, a part to which electric power is supplied from the generator 128 is an auxiliary machine.

  Here, since the conventional server cooling device is equipped with an air-water heat exchanger, if water leaks even from a part of the path through which the chiller water circulates in the air-water heat exchanger, this water damages the server. There is a risk. In this configuration, as described above, since the refrigerant circulating in the refrigeration cycle is supplied to the evaporator 21, even if the refrigerant leaks from the path through which the refrigerant circulates, the refrigerant instantly evaporates. However, there is no short circuit or short circuit of the server 3.

FIG. 3 is a block diagram illustrating a configuration example of a control system of the server rack cooling apparatus 100. In this figure, the thin solid line indicates the control signal line, the broken line indicates the power supply line, and the thick solid line (the line segment between the gas engine 127 and the generator 128) indicates the drive shaft.
As shown in FIG. 1, the centralized controller 200 is disposed on the lower floor 2 </ b> B of the underfloor space, and is a control circuit for centrally controlling the control units 80 and 85. The centralized controller 200 is supplied with power from the commercial power supply 300.
The centralized controller 200 is connected to server temperature sensors 29E and 29F (FIG. 2) that are provided in the server rack 10 and detect the temperature in the server rack 10. The server temperature sensors 29E and 29F are connected to the server rack. A signal indicating the temperature within 10 is input. The server temperature sensor 29E is provided at a position corresponding to the upper evaporation unit 22, and the server temperature sensor 29F is provided at a position corresponding to the lower evaporation unit 23. The centralized controller 200 detects the temperature in the server rack 10 by, for example, a statistical method based on the temperature signals input from the server temperature sensors 29E and 29F.

The control unit 80 controls the compressor motor 33, the expansion valve 36, and the outdoor fan motor 34 based on the control signal input from the centralized controller 200. Electric power is supplied to the compressor motor 33, the expansion valve 36, the outdoor fan motor 34, and the control unit 80 from the commercial power supply 300.
The control unit 85 controls the gas engine 127, the outdoor fan motor 126, and the expansion valve 124 based on the control signal input from the centralized controller 200. The generator 128 is driven by a gas engine 127 that is operated by, for example, city gas. In the present embodiment, the electric power generated by the generator 128 can be supplied to the centralized controller 200, the control unit 85, the control unit 80, the expansion valve 124, the outdoor fan motor 126, and the like. Instead of directly supplying the power generated by the generator 128 to each unit, for example, the frequency and voltage may be adjusted by an inverter or the like and then supplied to each unit.

Next, the operation of the server rack cooling device 100 according to the present embodiment will be described.
First, the operation when the power supply from the commercial power supply 300 is normal will be described.
When the power supply from the commercial power supply 300 is normal, the control unit 80 controls the compressor motor 33 to drive the compressor 32 under the control of the centralized controller 200 and controls the expansion valve 36 within an appropriate range. Open. The centralized controller 200 detects the temperature in the server rack 10 based on the signals input from the server temperature sensors 29E and 29F, and performs control based on the difference between the temperature in the server rack 10 and the target temperature. The unit 80 is controlled to control the compressor motor 33 so that the server room 2 has a target temperature. Note that the appropriate temperature range of the ambient temperature of the server 3 is generally set to 17 to 26 ° C. If the temperature rises further, the lifetime of the semiconductor and electronic parts constituting the server 3 is shortened and the failure rate is increased. For example, in the case of a semiconductor, if the failure rate at 40 ° C. is 1, it is 10 times at 60 ° C. and 100 times at 80 ° C. In the case of an electrolytic capacitor, if the temperature rises by 10 ° C., the life is halved. Therefore, normally, for example, 20 ° C. belonging to the range of 17 to 26 ° C. described above is set as the target temperature for air conditioning. Thereby, not only can the thermal runaway of the server 3 due to temperature rise be prevented, but also the failure rate of the electronic components constituting the server 3 can be reduced and the lifetime can be extended.

On the other hand, the control unit 85 stops the driving of the compressor 121 by stopping the driving of the gas engine 127 under the control of the centralized controller 200 and closes the expansion valve 124. Thereby, the supply of the refrigerant from the gas engine heat source unit 120 to the evaporator 21 is stopped.
That is, when the power supply from the commercial power source 300 is normal, the compressor 32 of the electric heat source unit 30 is driven, while the drive of the compressor 121 of the gas engine heat source unit 120 is stopped. The evaporator 21 is supplied with the refrigerant only from the electric heat source unit 30. This is because the drive level of the compressor 32 can be changed more finely when the compressor 32 is driven by the compressor motor 33 than when the compressor 121 is driven by the gas engine 127. When the power supply from the commercial power source 300 is normal and the compressor 32 of the electric heat source unit 30 can be driven, the server 3 is cooled by using the compressor 32 in the server room 2. This is because the temperature can be suitably brought close to the target temperature.

By the way, during execution of the above-described operation, a power failure occurs in the commercial power supply 300 due to a lightning strike or the like, and a safety device (shutoff device) disposed between the commercial power supply 300 and the electric heat source unit 30 is provided. When the supply of electric power from the commercial power source 300 to the electric heat source unit 30 stops due to operation, the compressor motor 33 to which the electric power is supplied from the commercial power source 300 cannot be driven, and the first refrigerant The refrigerant does not circulate in the circuit 18 and the server 3 cannot be cooled.
Based on this, in the present embodiment, the server 3 can be cooled even if the power supply from the commercial power supply 300 is stopped by performing the following operation.

FIG. 4 is a flowchart showing the operation of the server rack cooling apparatus 100 when the power supply from the commercial power supply 300 is stopped.
At the start of the operation of the flowchart, the server rack cooling device 100 is in a state where the power supply from the commercial power supply 300 is normal, that is, while the compressor 32 of the electric heat source unit 30 is driven, It is assumed that the driving of the compressor 121 of the gas engine type heat source unit 120 is stopped and the refrigerant is supplied to the evaporator 21 only from the electric heat source unit 30.
The server rack cooling device 100 includes a battery (not shown) that can be charged by the generator 128, and immediately after the power supply stop state occurs, power is supplied from the battery to each part of the server rack cooling device 100. Shall be.
Further, during the operation described below, the centralized controller 200 functions as a switching unit that switches between the first refrigerant circuit 18 and the second refrigerant circuit 19 and a detection unit that detects the occurrence of a power supply stop state from the commercial power supply 300. To do.

  First, when the supply of power from the commercial power source 300 to the electric heat source unit 30 is stopped, the centralized controller 200 detects this, and determines in step S10 that a power supply stop state has occurred (step S10). ; Yes), the process proceeds to step S11. Note that when the power supply is stopped, power is not supplied to the compressor motor 33, the expansion valve 36, and the outdoor fan motor 34, and these stop operating.

In step S11, the centralized controller 200 closes the expansion valve 36 of the electric heat source unit 30. Thereby, the circulation of the refrigerant in the first refrigerant circuit 18 is completely stopped, and the supply of the refrigerant from the electric heat source unit 30 to the evaporator 21 is stopped. In step S12, the centralized controller 200 opens the expansion valve 124 of the gas engine type heat source unit 120. In step S <b> 13, the centralized controller 200 starts driving the compressor 121 by driving the gas engine 127. As a result, the refrigerant circulates in the second refrigerant circuit 19 and supply of the refrigerant from the gas engine heat source unit 120 to the evaporator 21 is started. Furthermore, power generation by the generator 128 is started, and electric power is supplied from the generator 128 to the centralized controller 200, the control units 80 and 85, the expansion valve 124, and the outdoor fan motor 126.
In the series of operations from step S11 to step S13, the centralized controller 200 switches from the first refrigerant circuit 18 to the second refrigerant circuit 19, and supplies the refrigerant from the gas engine type heat source unit 120 to the evaporator 21. ing.

In step S14, the centralized controller 200 detects the temperature in the server room 2 based on the signals input from the server temperature sensors 29E and 29F.
In step S15, it is determined whether or not the temperature detected in step S14 is equal to the target temperature (for example, 20 ° C.) of the server room 2. If it is determined that they are equal (step S15; Yes), the process proceeds to step S17. In other cases (step S15; No), the process proceeds to step S16. For example, if it is determined that the temperature is higher than the target temperature, or if it is determined that the temperature is lower, the process proceeds to step S16.

  In step S16, the centralized controller 200 calculates the refrigeration load based on the difference between the temperature of the server room 2 detected in step S14 and the target temperature, and controls the control unit 85 based on the refrigeration load. Then, the output of the gas engine 127 is adjusted. Thereby, since the output of the gas engine 127 is adjusted so that the room temperature of the server room 2 approaches the target temperature, the server 3 can be prevented from causing a temperature abnormality (for example, thermal runaway).

  In step S17, the centralized controller 200 determines whether or not the power supply stop state has been resolved. If it is determined that the power supply stop state has been resolved (step S17; Yes), the process proceeds to step S18, and otherwise (step S17; No) returns to step S14 and repeats the same processing. For example, when the power failure is resolved and the power supply stop state is resolved, the process proceeds to step S18.

In step S <b> 18, the centralized controller 200 drives the compressor 32 by driving the compressor motor 33. In step S19, the centralized controller 200 opens the expansion valve 36 of the electric heat source unit 30 within an appropriate range. As a result, the refrigerant circulates in the first refrigerant circuit 18 and supply of the refrigerant from the electric heat source unit 30 to the evaporator 21 is started. In step S <b> 20, the centralized controller 200 stops driving the compressor 121 by stopping driving the gas engine 127. In step S21, the centralized controller 200 closes the expansion valve 124 of the gas engine type heat source unit 120. Thereby, the circulation of the refrigerant in the second refrigerant circuit 19 is completely stopped, and the supply of the refrigerant from the gas engine type heat source unit 120 to the evaporator 21 is stopped.
In step S22, the centralized controller 200 instructs the control units 80 and 85 to resume normal operation.

  By performing the operation as described above, the power supply stop state from the commercial power supply 300 is generated, so that the compressor motor 33 of the electric heat source unit 30 cannot be driven, and therefore the electric heat source unit 30 evaporates. Even when the refrigerant cannot be supplied to the evaporator 21, by driving the gas engine 127 that can be driven regardless of the state of the commercial power supply 300, the refrigerant flows into the evaporator 21 from the gas engine heat source unit 120, and the server 3 can be continuously performed.

As described above, according to the present embodiment, the evaporator 21 is disposed in the server rack 10 in which the server 3 is stored, and the refrigerant pipe extending from the evaporator 21 is connected to the refrigerant pipe 18 via the first refrigerant circuit 18. A compressor that is driven by a gas engine 127 through a second refrigerant circuit 19 while connecting a compressor 32 driven by a compressor motor 33 using a commercial power source and an electric heat source unit 30 having a condenser 35. 121, a generator 128 and an outdoor heat exchanger 123, connected to a gas engine heat source unit 120 that drives an auxiliary machine with power generated by the generator 128, a first refrigerant circuit 18, and a second refrigerant circuit 19. The central controller 200 detects the occurrence of a power supply stop state from the commercial power source to the electric heat source unit 30. During normal operation, the centralized controller 200 switches to the first refrigerant circuit 18 to supply refrigerant from the electric heat source unit 30 to the evaporator 21, and from the first refrigerant circuit 18 in the power supply stop state. Switching to the second refrigerant circuit 19, the refrigerant is supplied from the gas engine heat source unit 120 to the evaporator 21.
According to this, in the power supply stop state, the refrigerant is supplied to the evaporator 21 by driving the gas engine driven compressor 121 that can be driven without supplying power. For this reason, the server 3 can be cooled even when the power supply is stopped.

In this embodiment, during normal operation, the compressor 121 included in the gas engine heat source unit 120 is not driven, and the compressor 121 is driven when the centralized controller 200 detects the occurrence of a power supply stop state. Start.
According to this, during normal operation, the cost can be reduced by not driving the compressor 121 included in the gas engine type heat source unit 120, and when the power supply is stopped, by driving the compressor 121, The server 3 can be surely cooled.

The above-described embodiment is merely an aspect of the present invention, and can be arbitrarily modified and applied within the scope of the present invention.
For example, in the above-described embodiment, the conditioned air heat-exchanged in the indoor unit 130 is blown out from the floor outlet 147 and collected from the ceiling inlet 142, but is blown out from the ceiling to the ceiling. You may make it collect | recover on a surface, or you may make it collect | recover on a floor surface by blowing from a ceiling surface.
In the above-described embodiment, the centralized controller 200 functions as a switching unit and a detection unit. However, the control unit 80 and the control unit 85 may function as a switching unit and a detection unit.

It is a figure which shows the server rack cooling device which concerns on this embodiment. It is a figure which shows a server rack. It is a block diagram which shows the control system of a server rack cooling device. It is a flowchart which shows operation | movement of a server rack cooling device.

3 Server (electronic equipment)
10 Server rack (cabinet)
18 First refrigerant circuit 19 Second refrigerant circuit 21 Evaporator 30 Electric heat source unit 32 Compressor 33 Compressor motor (electric motor)
35 Condenser 100 Server rack cooling system (electronic equipment cooling system)
120 Gas engine type heat source unit 121 Compressor 123 Outdoor heat exchanger (condenser)
127 Gas engine 128 Generator 200 Centralized controller (switching means, detection means)
300 Commercial power supply

Claims (2)

Place the evaporator in the cabinet containing the electronic equipment,
An electric heat source unit having a compressor and a condenser driven by an electric motor using a commercial power source is connected to a refrigerant pipe extending from the evaporator via a first refrigerant circuit, and a second refrigerant circuit. A compressor driven by a gas engine, a generator and a condenser, and connected to a gas engine heat source unit that drives an auxiliary machine with the generated power of the generator,
Comprising switching means for switching the first and second refrigerant circuits;
Detecting means for detecting occurrence of a power supply stop state from the commercial power source to the electric heat source unit;
During normal operation, the switching means switches to the first refrigerant circuit to supply refrigerant from the electric heat source unit to the evaporator, and when power supply is stopped, the second refrigerant circuit supplies the second refrigerant circuit to the second refrigerant circuit. An electronic device cooling apparatus, wherein the refrigerant circuit is switched to the refrigerant circuit and the refrigerant is supplied from the gas engine heat source unit to the evaporator. During normal operation, the compressor included in the gas engine heat source unit is not driven,
2. The electronic device cooling according to claim 1, wherein when the detection unit detects the occurrence of a power supply stop state from the commercial power source to the electric heat source unit, driving of the compressor is started. 3. apparatus.

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