Air conditioning system and driving motor cooling method therefor

Abstract

The present application provides an air conditioning system and a driving motor cooling method for the air conditioning system. The air conditioning system includes: a main circuit, which has a multi-stage compressor, a condenser, a throttling element and an evaporator connected by pipelines; and a cooling branch, whose inlet is connected to the main circuit between the condenser and the throttling element, and whose outlet is connected to at least one of the first-stage air intake port and the intermediate-stage air intake port of the multi-stage compressor, the cooling branch flows through the driving motor of the multi-stage compressor, and a regulating valve for controlling the opening of the cooling branch is arranged on the cooling branch; a control module, which controls the opening of the regulating valve on the cooling branch based on the outlet temperature downstream of the driving motor on the cooling branch and the intermediate air intake pressure of the intermediate-stage air intake port of the multi-stage compressor. According to the air conditioning system and the driving motor cooling method used therefor of the present application, the system efficiency can be effectively maintained or improved while cooling the driving motor.

Description

Technical Field

[0001] The present application relates to the field of air conditioning, and more specifically, to an air conditioning system and a driving motor cooling method therefor. Background Art

[0002] In the field of air conditioning, for refrigeration systems, during operation, the compressor drive motor generates a lot of heat, so it needs to be cooled by a medium such as refrigerant or cooling oil to avoid motor failure or system failure due to excessive temperature. This situation is particularly serious in refrigeration systems with closed compressors. In addition, for air conditioning systems with multi-stage compression, the appropriate motor cooling solution may even affect the system energy efficiency. Summary of the invention

[0003] The present application aims to provide an air conditioning system and a drive motor cooling method therefor, so as to maintain or improve the system energy efficiency while cooling the drive motor.

[0004] To achieve at least one purpose of the present application, according to one aspect of the present application, an air conditioning system is provided, comprising: a main circuit, which has a multi-stage compressor, a condenser, a throttling element and an evaporator connected by pipelines; and a cooling branch, whose inlet is connected to the main circuit between the condenser and the throttling element, and whose outlet is connected to at least one of the first-stage suction port and the intermediate-stage suction port of the multi-stage compressor, the cooling branch flows through the drive motor of the multi-stage compressor, and a regulating valve for controlling the opening of the cooling branch is arranged on the cooling branch; a control module, which controls the opening of the regulating valve on the cooling branch based on the outlet temperature downstream of the drive motor on the cooling branch and the intermediate suction pressure of the intermediate-stage suction port of the multi-stage compressor.

[0005] Optionally, the cooling branch includes a first branch and a second branch connected to the multi-stage compressor downstream of the drive motor on the cooling branch; wherein the first branch includes a first valve for controlling its opening and closing and a first outlet connected to a first-stage air intake port of the multi-stage compressor; and the second branch includes a second valve for controlling its opening and closing and a second outlet connected to an intermediate-stage air intake port of the multi-stage compressor.

[0006] Optionally, the control module controls the opening and closing of the first outlet and / or the second outlet on the cooling branch based on the temperature of the drive motor.

[0007] Optionally, the multi-stage compressor is a screw compressor or a centrifugal compressor.

[0008] To achieve at least one purpose of the present application, according to another aspect of the present application, a drive motor cooling method for an air conditioning system is also provided, which is used for the air conditioning system as described above, and comprises: detecting the outlet temperature downstream of the drive motor on the cooling branch and the intermediate suction pressure of the intermediate stage suction port of the multi-stage compressor; when the difference between the outlet temperature and the saturation temperature corresponding to the intermediate suction pressure is greater than a preset superheat temperature, increasing the opening of the regulating valve; or, when the difference between the outlet temperature and the saturation temperature corresponding to the intermediate suction pressure is less than a preset superheat temperature, reducing the opening of the regulating valve.

[0009] Optionally, it includes: detecting the temperature of the drive motor; when the temperature of the drive motor is greater than a preset cooling temperature, turning on the first branch; or when the temperature of the drive motor is less than a preset cooling temperature, turning on the second branch.

[0010] To achieve at least one purpose of the present application, according to another aspect of the present application, an air conditioning system is also provided, which includes: a main circuit, which has a multi-stage compressor, a condenser, a throttling element and an evaporator connected by pipelines; and a cooling branch, whose inlet is connected to the main circuit between the condenser and the throttling element, and which flows through the drive motor of the multi-stage compressor, and the cooling branch also includes a first branch and a second branch connected to the multi-stage compressor from the downstream of the drive motor; wherein the first branch includes a first valve for controlling its opening and closing and a first outlet connected to the first-stage air intake port of the multi-stage compressor; and the second branch includes a second valve for controlling its opening and closing and a second outlet connected to the intermediate-stage air intake port of the multi-stage compressor; and a control module, which controls the opening and closing of the first outlet and / or the second outlet on the cooling branch based on the temperature of the drive motor.

[0011] Optionally, a regulating valve for controlling the opening of the cooling branch is further provided between the inlet of the cooling branch and the drive motor.

[0012] Optionally, the control module controls the opening of the regulating valve on the cooling branch based on the outlet temperature downstream of the drive motor on the cooling branch and the intermediate suction pressure of the intermediate stage suction port of the multi-stage compressor.

[0013] Optionally, the multi-stage compressor is a screw compressor or a centrifugal compressor.

[0014] To achieve at least one purpose of the present application, according to another aspect of the present application, a method for cooling a drive motor for an air conditioning system is provided, which is used in the air conditioning system as described above, and includes: detecting the temperature of the drive motor; when the temperature of the drive motor is greater than a preset cooling temperature, turning on the first branch; or when the temperature of the drive motor is less than a preset cooling temperature, turning on the second branch.

[0015] Optionally, it includes: detecting the outlet temperature downstream of the drive motor on the cooling branch and the intermediate suction pressure of the intermediate stage suction port of the multi-stage compressor; when the difference between the outlet temperature and the saturation temperature corresponding to the intermediate suction pressure is greater than a preset superheat temperature, increasing the opening of the regulating valve; or, when the difference between the outlet temperature and the saturation temperature corresponding to the intermediate suction pressure is less than a preset superheat temperature, reducing the opening of the regulating valve.

[0016] According to the air conditioning system and the drive motor cooling method used therefor of the present application, by reasonably designing and selecting the outlet position of the cooling branch on the main circuit, and adjusting the opening of the regulating valve to adjust the refrigerant flow rate of the cooling branch, the system efficiency can be effectively maintained or improved while cooling the drive motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a system schematic diagram of an embodiment of the air conditioning system of the present application. DETAILED DESCRIPTION

[0018] The present application provides an embodiment of an air conditioning system 100. Figure 1 , the air conditioning system 100 includes a main circuit 110 that is generally used to provide a refrigeration cycle and a cooling branch 120 that is used to draw water from the main circuit 110 to provide cooling for the drive motor of the compressor. The main circuit 110 has an exhaust port of a multi-stage compressor 111, a condenser 112, a throttling element 113, an evaporator 114, and an air intake port of the multi-stage compressor 111 that are connected by pipelines to form a loop. Specifically, the multi-stage compressor 111 refers to a compressor that can compress the refrigerant twice or more. For example, the multi-stage compressor 111 shown in the present embodiment has two compression stages, and there is a flow channel between the two compression stages to communicate with each other so as to achieve two compressions of the refrigerant. For example, see Figure 1, the first compression stage of the multi-stage compressor 111 may have a first-stage suction port 111b and a first-stage exhaust port 111c, and the second compression stage may have an intermediate-stage suction port 111d and an intermediate-stage exhaust port 111e; wherein, the refrigerant enters the compressor from the first-stage suction port 111b, and after being compressed in the first compression stage, it may flow out from the first-stage exhaust port 111c, and flow into the second compression stage from the intermediate-stage suction port 111d to be compressed again, and then flow out of the compressor from the intermediate-stage exhaust port 111e to participate in the circulation of the main circuit 110. Of course, if the multi-stage compressor shown has more intermediate stages, it can flow through each intermediate stage in turn in the above manner to receive further compression. Specifically, it flows into the condenser 112 to release heat and condense into a liquid refrigerant, expands and reduces pressure through the throttling element 113, and then enters the evaporator 114 to absorb heat and evaporate, and enters the compressor 111 again to start a new round of working cycle.

[0019] In addition, the cooling branch 120 for diverting from the main circuit 110 to provide cooling for the drive motor of the compressor can be arranged so that its inlet 120a is connected to the main circuit 110 between the condenser 112 and the throttling element 113, because the liquid refrigerant here has a relatively high pressure, thereby providing sufficient flow for the branch, which helps to cool the drive motor. The outlet of the cooling branch 120 can be connected to at least one of the first-stage suction port 111b and the intermediate-stage suction port 111d of the multi-stage compressor 111, so that the refrigerant that has completed the motor cooling function can enter the compression stage to participate in a new round of work cycle. Among them, if only one outlet is set for the cooling branch, then of course, the motor cooling function can be performed using the only branch. If two outlets are set for the cooling branch at the same time, which branch can be selected to release the refrigerant that has completed the cooling function according to the actual situation. For example, if the refrigerant is directly led back to the intermediate-stage suction port 111d of the compressor, a higher energy efficiency ratio can be brought to the system as a whole. However, if the suction and exhaust pressure difference caused by releasing to the intermediate suction port 111d is small, it may lead to insufficient liquid supply, which in turn affects the insufficient cooling of the motor. In this case, this branch is not the best choice. As an alternative, it is possible to consider directly leading the refrigerant back to the first-stage suction port 111b of the compressor to provide a certain degree of pressure difference compensation.

[0020] Furthermore, the cooling branch 120 should flow through the driving motor 111a of the multi-stage compressor 111 so as to cool it. A regulating valve 120b for controlling the opening of the cooling branch 120 may also be provided on the cooling branch 120. The corresponding control is performed by the control module of the air conditioning system 100. For example, the opening of the regulating valve 120b on the cooling branch 120 may be controlled based on the outlet temperature T4 downstream of the driving motor 111a on the cooling branch 120 and the intermediate suction pressure P3 of the intermediate stage suction port of the multi-stage compressor 111. Specifically, in order to achieve cooling of the motor while ensuring that the refrigerant entering the first stage or the intermediate stage of the compression stage is sufficiently superheated and presents a gaseous state, the corresponding saturated intermediate suction temperature can be obtained through the intermediate suction pressure P3, and then the superheat of the compressor downstream of the drive motor 111a can be obtained through the temperature difference between the outlet temperature T4 downstream of the drive motor 111a and the saturated intermediate suction temperature, and the opening of the regulating valve 120b is controlled to ensure that the superheat here corresponds to the preset superheat, so as to ensure that the refrigerant that completes the motor cooling function can enter the compression stage suction port in a gaseous form to avoid liquid hammer.

[0021] Under this arrangement, the air conditioning system in this embodiment can effectively maintain or improve the system efficiency while cooling the drive motor by reasonably designing and selecting the outlet position of the cooling branch on the main circuit and adjusting the opening of the regulating valve to adjust the refrigerant flow rate of the cooling branch.

[0022] As briefly described above, in one case, the cooling branch 120 may include a first branch 121 and a second branch 122 connected to the multi-stage compressor 111 from the downstream of the drive motor 111a on the cooling branch 120. Among them, the first branch 121 includes a first valve 121b for controlling its opening and closing and a first outlet 121a connected to the first-stage air intake 111b of the multi-stage compressor 111; and the second branch 122 includes a second valve 122b for controlling its opening and closing and a second outlet 122a connected to the middle-stage air intake of the multi-stage compressor 111. Therefore, when the premise of being able to meet the cooling target of the motor, it is reliable to consider closing the first branch 121 and opening the second branch 122 to maximize the system energy efficiency. If the energy efficiency improvement and motor cooling cannot be achieved at the same time under some working conditions with low suction and exhaust pressure difference, it is possible to consider closing the second branch 122 and opening the first branch 121 to achieve the cooling effect on the motor as much as possible.

[0023] More specifically, the aforementioned control purpose can be achieved by analyzing the temperature T3 of the drive motor 111a through the control module. For example, when the second outlet 122a is opened (i.e., the second valve 122b is opened) and the first outlet 121a is closed (i.e., the first valve 121b is closed), if the temperature T3 of the drive motor 111a is not higher than the set value, it is considered that the current cooling effect fully meets the motor cooling requirements, and it can be considered to maintain the current mode to balance motor cooling and system energy efficiency. If at this time, the temperature T3 of the drive motor 111a is higher than the set value, it is considered that the cooling effect cannot meet the motor cooling requirements, and it can be considered to close the second outlet 122a (i.e., close the second valve 122b), and open the first outlet 121a (i.e., open the first valve 121b) to further improve the cooling of the motor.

[0024] In addition, more detailed improvements or selections may be made to some components of the air conditioning system to better match the aforementioned embodiments.

[0025] For example, such a hermetic multi-stage compressor 111 is generally a screw compressor or a centrifugal compressor.

[0026] For another example, the main circuit 110 may further include a drying filter 115, which is disposed between the condenser 112 and the throttling element 113, to dry the moisture in the system and filter the impurities in the system. Since the refrigerant flowing out of the condenser outlet during normal operation is pure liquid phase refrigerant, the resistance of the refrigerant flowing through the filter can be minimized.

[0027] In addition, a driving motor cooling method for an air conditioning system is also provided herein, which can be used in the air conditioning system 100 of any of the above embodiments or any combination thereof. Specifically, the driving motor cooling method of the air conditioning system includes: detecting the outlet temperature T4 downstream of the driving motor 111a on the cooling branch 120 and the intermediate suction pressure P3 of the intermediate stage suction port of the multi-stage compressor 111; when the difference between the outlet temperature T4 and the saturation temperature corresponding to the intermediate suction pressure P3 is greater than the preset superheat temperature, it means that the liquid-phase refrigerant evaporates too fully when cooling the motor, and it can be considered to increase the opening of the regulating valve 120b to appropriately increase the amount of liquid-phase refrigerant introduced; or, when the difference between the outlet temperature and the saturation temperature corresponding to the intermediate suction pressure is less than the preset superheat temperature, it means that the liquid-phase refrigerant evaporates insufficiently when cooling the motor, and it can be considered to reduce the opening of the regulating valve 120b to appropriately reduce the amount of liquid-phase refrigerant introduced.

[0028] In addition, when the cooling branch 120 of the air conditioning system to which the method is applied includes at least two outlets, the method may further include: detecting the temperature T3 of the drive motor 111a and making a judgment; when the temperature T3 of the drive motor 111a is greater than the preset cooling temperature, the motor cooling should be taken as the primary task, and at this time, the first branch 121 is turned on and the second branch 122 is not turned on; or when the temperature T3 of the drive motor 111a is less than the preset cooling temperature, the motor cooling can be satisfied while appropriately improving the system energy efficiency, and at this time, the second branch 122 is turned on and the first branch 121 is not turned on.

[0029] As a variation of the embodiment of the aforementioned air conditioning system and the embodiment of the corresponding cooling method, an embodiment of an air conditioning system can also be additionally provided herein. The air conditioning system 100 includes a main circuit 110 that is generally used to provide a refrigeration cycle and a cooling branch 120 that is used to divert flow from the main circuit to provide cooling for the drive motor of the compressor. Among them, the main circuit is the same as the main circuit in the aforementioned embodiment, so it is not repeated. Its cooling branch 120 can be arranged so that its inlet 120a is connected to the main circuit 110 between the condenser 112 and the throttling element 113, because the liquid refrigerant here has a relatively high pressure, thereby providing sufficient flow for the branch, which helps to cool the drive motor. And it should also flow through the drive motor 111a of the multi-stage compressor 111 so as to cool it. In addition, the cooling branch 120 can also include a first branch 121 and a second branch 122 connected to the multi-stage compressor 111 downstream of the drive motor 111a. The first branch 121 includes a first valve 121b for controlling its opening and closing and a first outlet 121a connected to the first-stage air intake port 111b of the multi-stage compressor 111; and the second branch 122 includes a second valve 122b for controlling its opening and closing and a second outlet 122a connected to the middle-stage air intake port of the multi-stage compressor 111. In addition, the air conditioning system should also include a control module for performing response control, which can control the opening and closing of the first outlet 121a and / or the second outlet 122a on the cooling branch 120 based on the temperature T3 of the drive motor 111a.

[0030] In this arrangement, since the cooling branch has two branches, it is possible to choose which branch to use to release the refrigerant that has completed the cooling function according to the actual situation. For example, if the refrigerant is directly led back to the intermediate-stage air intake port 111d of the compressor, a higher energy efficiency ratio can be brought to the system as a whole. However, if the suction and exhaust pressure difference brought by the release to the intermediate-stage air intake port 111d is small, it may cause insufficient discharge volume, thereby affecting the insufficient degree of cooling of the motor. At this time, this branch is not the best choice. As an alternative, it is possible to consider directly leading the refrigerant back to the first-stage air intake port 111b of the compressor to provide a certain degree of pressure difference compensation. Therefore, when the premise of being able to meet the cooling target of the motor can be met, it is reliable to consider closing the first branch 121 and opening the second branch 122 to maximize the system energy efficiency. If the energy efficiency improvement and motor cooling cannot be achieved at the same time under some working conditions with low suction and exhaust pressure difference, it is possible to consider closing the second branch 122 and opening the first branch 121 to achieve the cooling effect on the motor as much as possible. More specifically, when the second outlet 122a is open and the first outlet 121a is closed, if the temperature T3 of the drive motor 111a is not higher than the set value, it is considered that the cooling effect fully meets the motor cooling requirement, and it is possible to consider maintaining the current mode to balance motor cooling and system energy efficiency. If at this time, the temperature T3 of the drive motor 111a is higher than the set value, it is considered that the current cooling effect cannot meet the motor cooling requirement, and it is possible to consider closing the second outlet 122a and opening the first outlet 121a to further improve the cooling of the motor.

[0031] Furthermore, a regulating valve 120b for controlling the opening of the cooling branch 120 may be provided between the inlet 120a of the cooling branch 120 and the drive motor 111a. More specifically, the corresponding control may be performed by the control module of the air conditioning system 100. For example, the opening of the regulating valve 120b on the cooling branch 120 may be controlled based on the outlet temperature T4 downstream of the drive motor 111a on the cooling branch 120 and the intermediate suction pressure P3 of the intermediate stage suction port of the multi-stage compressor 111. Specifically, in order to achieve cooling of the motor while ensuring that the refrigerant entering the first stage or the intermediate stage of the compression stage is sufficiently superheated and presents a gaseous state, the corresponding saturated intermediate suction temperature can be obtained through the intermediate suction pressure P3, and then the superheat of the compressor downstream of the drive motor 111a can be obtained through the temperature difference between the outlet temperature T4 downstream of the drive motor 111a and the saturated intermediate suction temperature, and the opening of the regulating valve 120b is controlled to ensure that the superheat here corresponds to the preset superheat, so as to ensure that the refrigerant that completes the motor cooling function can enter the compression stage suction port in a gaseous form to avoid liquid hammer.

[0032] In addition, similarly, more detailed improvements or selections may be made to some components of the air conditioning system to better match the aforementioned embodiments.

[0033] For example, such a hermetic multi-stage compressor 111 is generally a screw compressor or a centrifugal compressor.

[0034] For another example, the main circuit 110 may further include a drying filter 115, which is disposed between the condenser 112 and the throttling element 113, to dry the moisture in the system and filter the impurities in the system. Since the refrigerant flowing out of the condenser outlet during normal operation is pure liquid phase refrigerant, the resistance of the refrigerant flowing through the filter can be minimized.

[0035] Similarly, a method for cooling a drive motor for an air conditioning system is also provided herein, which can be used in an air conditioning system of any of the above embodiments or a combination thereof. Specifically, the method for cooling a drive motor for an air conditioning system includes: detecting the temperature T3 of the drive motor 111a and making a judgment; when the temperature T3 of the drive motor 111a is greater than a preset cooling temperature, the first branch 121 should be turned on to meet the motor cooling as the primary task; or when the temperature T3 of the drive motor 111a is less than the preset cooling temperature, the second branch 122 can be turned on to meet the motor cooling while appropriately considering improving the system energy efficiency.

[0036] In addition, when the cooling branch 120 of the air conditioning system to which the method is applied also includes a regulating valve 120b arranged thereon, the method may further include: detecting the outlet temperature T4 downstream of the drive motor 111a on the cooling branch 120 and the intermediate suction pressure P3 of the intermediate stage suction port of the multi-stage compressor 111; when the difference between the outlet temperature T4 and the saturation temperature corresponding to the intermediate suction pressure P3 is greater than the preset superheat temperature, it indicates that the liquid-phase refrigerant evaporates too fully when cooling the motor, and it may be considered to increase the opening of the regulating valve 120b to appropriately increase the amount of liquid-phase refrigerant introduced; or, when the difference between the outlet temperature and the saturation temperature corresponding to the intermediate suction pressure is less than the preset superheat temperature, it indicates that the liquid-phase refrigerant evaporates insufficiently when cooling the motor, and it may be considered to reduce the opening of the regulating valve 120b to appropriately reduce the amount of liquid-phase refrigerant introduced.

[0037] The following will combine the above embodiments with the attached Figure 1 First, in the main loop 110, the gas-phase refrigerant enters the compressor from the first-stage air intake port 111b of the compressor 111, and after being compressed in the first compression stage, it can flow out from the first-stage exhaust port 111c, and flow into the second compression stage from the intermediate-stage air intake port 111d to be compressed again, and then flow out of the compressor from the intermediate-stage exhaust port 111e to flow into the condenser 112 to release heat and condense into a liquid-phase refrigerant.

[0038] The refrigerant is then divided into two parts, the main part of which flows to the throttling element 113 for expansion and pressure reduction, enters the evaporator 114 to absorb heat and evaporate, and enters the compressor 111 again to start a new round of working cycle; the other part of the refrigerant is introduced into the cooling branch 120 through the inlet 120a, and after being regulated by the regulating valve 120b, flows through the drive motor 111a of the compressor to cool it. Among them, the regulation of the regulating valve 120b here is related to the outlet temperature T4 downstream of the drive motor 111a on the cooling branch 120 and the intermediate suction pressure P3 of the intermediate stage suction port of the multi-stage compressor 111: when the difference between the outlet temperature T4 and the saturation temperature corresponding to the intermediate suction pressure P3 is greater than the preset superheat temperature, it means that the liquid-phase refrigerant evaporates too fully when cooling the motor, and it can be considered to increase the opening of the regulating valve 120b to appropriately increase the amount of liquid-phase refrigerant introduced; or, when the difference between the outlet temperature and the saturation temperature corresponding to the intermediate suction pressure is less than the preset superheat temperature, it means that the liquid-phase refrigerant evaporates insufficiently when cooling the motor, and it can be considered to reduce the opening of the regulating valve 120b to appropriately reduce the amount of liquid-phase refrigerant introduced.

[0039] The refrigerant that has completed the cooling function continues to flow along the cooling branch 120 in preparation for flowing back into the main circuit 110. At this time, it can choose to return to the first-stage air intake port 111b of the compressor via the first outlet 121a of the first branch 121, or it can choose to return to the intermediate-stage air intake port 111d of the compressor via the second outlet 122a of the second branch 122. The specific control method of the branch conduction is associated with the temperature T3 of the drive motor 111a: when the temperature T3 of the drive motor 111a is greater than the preset cooling temperature, the first branch 121 should be turned on to meet the motor cooling as the primary task; or when the temperature T3 of the drive motor 111a is less than the preset cooling temperature, the second branch 122 can be turned on to meet the motor cooling while appropriately considering the improvement of the system energy efficiency. In this way, the entire working process of the air conditioning system is realized.

[0040] The above examples mainly illustrate the air conditioning system of the present application and the drive motor cooling method therefor. Although only some of the embodiments of the present application are described, it should be understood by those skilled in the art that the present application can be implemented in many other forms without departing from its subject matter and scope. Therefore, the examples and embodiments shown are regarded as illustrative rather than restrictive, and the present application may cover various modifications and substitutions without departing from the spirit and scope of the present application as defined in the attached claims.

Claims

1. An air conditioning system, characterized in that: include: A main circuit having a multi-stage compressor, a condenser, a throttling element and an evaporator connected by pipelines; as well as A cooling branch, the inlet of which is connected to the main circuit between the condenser and the throttling element, and flows through the driving motor of the multi-stage compressor, the cooling branch also includes a first branch and a second branch connected to the multi-stage compressor from the downstream of the driving motor; wherein the first branch includes a first valve for controlling its opening and closing and a first outlet connected to the first-stage air intake of the multi-stage compressor; and the second branch includes a second valve for controlling its opening and closing and a second outlet connected to the middle-stage air intake of the multi-stage compressor; as well as A control module controls the opening and closing of the first outlet and / or the second outlet on the cooling branch based on the temperature of the drive motor.

2. The air conditioning system according to claim 1, characterized in that: A regulating valve for controlling the cooling branch is also provided between the inlet of the cooling branch and the drive motor.

3. The air conditioning system according to claim 2, characterized in that: The control module controls the opening of the regulating valve on the cooling branch based on the outlet temperature downstream of the driving motor on the cooling branch and the intermediate suction pressure of the intermediate stage suction port of the multi-stage compressor.

4. The air conditioning system according to any one of claims 1 to 3, characterized in that: The multi-stage compressor is a screw compressor or a centrifugal compressor.

5. A method for cooling a drive motor for an air conditioning system, which is used in the air conditioning system according to any one of claims 1 to 4, characterized in that: include: detecting the temperature of the driving motor; When the temperature of the driving motor is greater than a preset cooling temperature, the first branch is turned on; Alternatively, when the temperature of the drive motor is lower than a preset cooling temperature, the second branch is turned on.

6. The driving motor cooling method according to claim 5, characterized in that: include: Detect the outlet temperature downstream of the drive motor on the cooling branch and the intermediate suction pressure of the intermediate stage suction port of the multi-stage compressor; when the difference between the outlet temperature and the saturation temperature corresponding to the intermediate suction pressure is greater than a preset superheat temperature, increase the opening of the regulating valve; or, when the difference between the outlet temperature and the saturation temperature corresponding to the intermediate suction pressure is less than a preset superheat temperature, reduce the opening of the regulating valve.

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