A method of thermal management of an electric motor and system therefor

Abstract

The application belongs to the technical field of aircraft power systems, and relates to a heat management method and system of an electric motor, and proposes an efficient heat dissipation control method, which comprises the following steps: collecting winding temperature and cooling liquid temperature of the electric motor; using a vector control architecture to control the operation of a heat dissipation motor of the electric motor to heat the cooling liquid; calculating the temperature difference between the winding and the cooling liquid of the electric motor to obtain a speed instruction of the heat dissipation motor; calculating the loss of the electric motor and the heat derived by the heat management system to obtain the heat absorbed by the electric motor, and calculating a feedforward amount of the current instruction of the heat dissipation motor; and adjusting the speed of the heat dissipation motor to control the rotating operation of the cooling pump and the fan. The application realizes the heat management of the electric motor in the whole temperature range by adjusting the operating state of the heat dissipation motor in real time, and improves the heat dissipation efficiency of the electric motor under strong overload.

Description

Technical Field

[0001] This invention belongs to the field of aircraft propulsion system technology, and particularly relates to a thermal management method and system for an electric motor. Background Technology

[0002] The electric motor is the core component of an electric vertical takeoff and landing (EVTOL) aircraft, providing the power source for the aircraft. Its reliability and performance directly determine the reliability and performance of the aircraft. Due to the stringent weight requirements of aircraft, the electric motor faces boundary constraints of high power-to-weight ratio and high torque density, resulting in severe winding heat generation. Furthermore, due to the harsh operating conditions throughout the flight profile, the heat accumulation process is complex, leading to a reduction in the insulation life of the windings and even overheating and burnout failure, directly affecting the reliability of the electric motor. In addition, when the temperature rise of the electric motor power transistor exceeds the junction temperature of the device, it can also cause system malfunction, further affecting the safety of the aircraft. Therefore, achieving efficient heat dissipation design for the electric motor windings and power transistors is a fundamental and necessary condition for ensuring the normal operation of the electric motor.

[0003] In existing solutions, the cooling motors of electric motor thermal management systems operate at constant or full speeds throughout their entire working profile, resulting in poor operating condition matching and wasted energy. Furthermore, due to the cumulative effect of heat, electric motors reach high temperatures after operating for a period of time, and their temperature rises rapidly when faced with short-term strong overload conditions, seriously threatening the reliability of insulation. However, existing solutions lack rapid heat dissipation control methods for electric motors under short-term strong overload conditions. Summary of the Invention

[0004] This invention proposes a thermal management method and system for electric motors to improve the heat dissipation efficiency of electric motors.

[0005] The first aspect of this invention provides a thermal management method for an electric motor, comprising:

[0006] Step 1: Collect the winding temperature of the electric motor. Power transistor temperature and coolant temperature ;

[0007] Step 2: Using a vector control architecture, control the operation of the cooling motor of the electric motor. The speed command of the cooling motor vector control is zero, and the d-axis current command is a preset positive value.

[0008] Step 3: Determine the coolant temperature of the electric motor. Is it below the temperature threshold? If yes, return to step two; otherwise, proceed to step four.

[0009] Step 4: Based on the winding temperature of the electric motor Coolant temperature Power transistor temperature Obtain the cooling motor speed command N ref ;

[0010] Step 5: Based on the equivalent mass of the electric motor Equivalent heat capacity and the heat loss P absorbed by the electric motor in Get the feedforward amount of the q-axis current command of the cooling motor. The heat loss absorbed by the electric motor is determined based on the total loss of the electric motor and the heat loss derived from the electric motor thermal management system.

[0011] Step 6: According to the cooling motor speed command Feedforward quantity ΔI of the q-axis current command of the cooling motor qref The duty cycle of the inverter for the cooling motor is calculated using vector control, and PWM (Pulse Width Modulation) is output to adjust the speed of the cooling motor and control the operation of the cooling pump and fan.

[0012] Optionally, obtain the cooling motor speed command N. ref ,include:

[0013] Obtain the winding temperature of the electric motor Coolant temperature First temperature difference ;

[0014] Obtain the power tube temperature of the electric motor Coolant temperature The second temperature difference ;

[0015] The cooling motor speed command is obtained based on the first temperature difference and the second temperature difference. The , These are the preset weighting coefficients.

[0016] Optionally, the heat loss absorbed by the electric motor ;

[0017] Among them, P out Heat loss generated by the thermal management system of electric motor. ;P h Heat loss due to coolant drained from the thermal management system of electric motor Heat dissipation from the heat sink casing The heat dissipated by the fan;

[0018] P loss The total loss of the electric motor, Pm This refers to the stator losses of the electric motor. , For stator copper losses in electric motors, Stator iron loss;

[0019] P p For the power transistor losses of the electric motor. , This refers to the switching losses of the power transistors in the electric motor. This refers to conduction loss.

[0020] Optionally, the d-axis current command in step two can be retrieved. Between 0.05 and 0.2 times, the The fundamental flux linkage amplitude of the cooling motor, the This is the direct-axis inductance of the heat dissipation motor.

[0021] Optional, preset weighting coefficients , satisfy The The insulation class temperature of the electric motor winding, the This refers to the junction temperature of the power transistor in the electric motor.

[0022] Optional, stator copper loss of electric motor Includes DC copper losses, AC copper losses, and stator iron losses of electric motors. It includes hysteresis loss, eddy current loss, and additional loss, the latter being obtained by fitting test data of additional loss of electric motor.

[0023] Optional, the switching losses of the power transistors in the electric motor The switching frequency of the electric motor power transistor Total energy of a single power transistor in a single switching operation Calculated;

[0024] .

[0025] Optional, heat dissipation from coolant The The volumetric flow rate of the coolant, The density of the coolant, the The specific heat capacity of the coolant, The volumetric flow rate is the temperature difference between the coolant inlet and outlet. The The tooth width of the cooling pump, the The module of the cooling pump, the The number of teeth of the cooling pump, the This refers to the rotational speed of the cooling pump.

[0026] Optionally, the heat dissipation housing dissipates heat... The The heat transfer coefficient of the heat dissipation shell is... The heat dissipation area of ​​the heat sink housing is... This refers to the temperature of the heat sink housing.

[0027] Optionally, the heat dissipated by the fan The The airflow of the fan, the The density of air, the The specific heat capacity of air, the The airflow of the fan is the temperature difference between the air before and after passing through the heat sink housing. The calibration is based on the fan speed.

[0028] Optionally, the equivalent mass of the electric motor The This refers to the mass of the electric motor windings. This refers to the weight of the stator core of the electric motor. This refers to the weight of the power transistor in the electric motor.

[0029] Optionally, the equivalent heat capacity of the electric motor The The specific heat capacity of the electric motor windings. This refers to the specific heat capacity of the stator core of an electric motor. This is the specific heat capacity of the power tube in the electric motor.

[0030] A second aspect of the present invention provides an electric motor thermal management system, comprising:

[0031] Controller for performing the electric motor thermal management method as described in any one of the first aspects;

[0032] The cooling motor has two mechanical output ports, which are used to drive the cooling pump and the fan to rotate, respectively.

[0033] Cooling pumps are used to circulate the coolant in the thermal management system.

[0034] A fan is used to force airflow between the heat sink and the outside environment for cooling.

[0035] The heat dissipation housing is used to fix the heat dissipation motor, cooling pump, and fan, and at the same time provide the cavity required for the coolant. The heat dissipation housing is made of a material with a thermal conductivity higher than the preset thermal conductivity.

[0036] Optionally, the surface of the heat dissipation housing has a three-period minimal curved surface structure.

[0037] Optionally, the controller includes:

[0038] The bus communication unit is used to provide feedback to the flight control computer on the temperature status of the electric motor windings, power transistors, and coolant.

[0039] The signal acquisition unit is used to acquire the temperature of the electric motor windings, power transistors, and coolant, and to sample the phase current and rotor position information of the cooling motor.

[0040] The instruction calculation unit is used to calculate the feedforward amount of the vector control speed command and the q-axis current command of the cooling motor.

[0041] The PWM output unit outputs PWM based on the duty cycle calculated by vector control, and amplifies the power to drive the rotation of the cooling motor.

[0042] This invention proposes a thermal management method and system for electric motors, addressing the need for heat dissipation across the entire flight profile of electric motors. By fully considering the heat accumulation effect, the rotational speed of the cooling motor is dynamically adjusted in real time, achieving efficient heat dissipation of the electric motor windings and power transistors, thus ensuring the safe and reliable operation of the electric motor. Attached Figure Description

[0043] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 This is a flowchart of a thermal management method for an electric motor;

[0045] Figure 2 This is a schematic diagram of an electric motor thermal management system;

[0046] Figure 3 This is a schematic diagram of a controller for an electric motor thermal management system;

[0047] Figure 4 This is a control block diagram for coolant preheating in an electric motor thermal management system;

[0048] Figure 5 This is a control block diagram for the speed regulation of the cooling motor in an electric motor thermal management system.

[0049] Figure 6This is a flowchart of a method for calculating the feedforward quantity of the q-axis current command of a heat dissipation motor in an electric motor thermal management system.

[0050] Explanation of reference numerals in the attached figures:

[0051] 10-Controller, 20-Cooling motor, 30-Cooling pump, 40-Fan, 50-Cooling housing, 101-Bus communication unit, 102-Signal acquisition unit, 103-Instruction calculation unit, 104-PWM output unit. Detailed Implementation

[0052] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0053] The features and illustrative embodiments of various aspects of the present invention will now be described in detail. Numerous specific details are set forth in the following detailed description to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention may be practiced without requiring some of these specific details. The following description of embodiments is merely intended to provide a better understanding of the invention by illustrating examples of the invention. The invention is by no means limited to any specific setups and methods set forth below, but covers any improvements, substitutions, and modifications to structures, methods, and devices without departing from the spirit of the invention. Well-known structures and techniques are not shown in the drawings and the following description to avoid unnecessarily obscuring the invention.

[0054] It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other, and the various embodiments can be referenced and cited in each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0055] like Figure 1-6 As shown, this invention discloses a thermal management method and system for an electric motor. The thermal management method for the electric motor adopts the following scheme:

[0056] This invention collects data on the motor winding temperature, power transistor temperature, and coolant temperature; controls the operation of the motor's cooling motor to heat the coolant; calculates the temperature difference between the motor windings, power transistors, and coolant to obtain the cooling motor speed command; calculates the heat loss absorbed by the motor to obtain the feedforward amount of the cooling motor current command; and adjusts the cooling motor speed to control the rotation of the cooling pump and fan. By adjusting the operating state of the cooling motor in real time, this invention achieves thermal management of the motor across its entire temperature range, improving the motor's heat dissipation efficiency under severe overload conditions.

[0057] In a specific embodiment, the electric motor thermal management method provided by the present invention takes the following specific steps:

[0058] Step 1: Set the electric motor's cooling motor to use a vector control architecture and collect the winding temperature of the electric motor. Power transistor temperature and coolant temperature ;

[0059] Step 2: Using a vector control architecture, control the operation of the cooling motor of the electric motor. The speed command of the cooling motor vector control is zero, and the d-axis current command is a preset positive value.

[0060] Step 3: Determine the coolant temperature of the electric motor. Is it below the temperature threshold? ,if If yes, return to step two; otherwise, proceed to step four.

[0061] Step 4: Calculate the first temperature difference between the electric motor windings and the coolant. Calculate the second temperature difference between the power tube and coolant of the electric motor. The speed command of the cooling motor is obtained by linear combination. The , Preset weighting coefficients;

[0062] Step 5: Stator copper loss of the electric motor Stator iron loss Calculate the stator losses of an electric motor The switching losses of the power transistors in the electric motor Conduction loss Calculate the power transistor losses of an electric motor Calculate the total losses of the electric motor. The heat loss generated by the coolant in the electric motor thermal management system Heat dissipation from the heat sink casing Heat dissipated by the fan Calculate the heat loss derived from the electric motor thermal management system According to the heat balance equation Calculate the heat loss absorbed by the electric motor The equivalent mass of the electric motor Equivalent heat capacity Calculate the feedforward amount of the q-axis current command for the cooling motor. ;

[0063] Step 6: According to the cooling motor speed command q-axis current command feedforward ΔI qref The duty cycle of the inverter for the cooling motor is calculated using vector control, and the output PWM is used to adjust the speed of the cooling motor and control the operation of the cooling pump and fan.

[0064] This invention addresses the issue of low coolant temperature and poor flow in electric generators when they are not in operation, employing a preheating method. Under low-temperature conditions, the invention first increases losses by energizing the generator to preheat the coolant. When energized, the speed command is zero, and the motor is stationary, effectively preventing rotor friction damage caused by high coolant resistance. A vector control strategy is used, ensuring the speed command is zero, guaranteeing a zero q-axis current command and a preset positive d-axis current command, accelerating motor heating. Preheating to a suitable operating temperature range for the coolant is also necessary. This invention effectively reduces the viscous resistance of the coolant.

[0065] Under normal operating conditions with high temperatures, the coolant is in a liquid state and has low viscous resistance, so there is no need for continuous preheating. The cooling motor can be directly controlled to rotate and drive the coolant to flow, thereby cooling the electric motor.

[0066] In this invention, the heat dissipation effect of the heat sink, fan, and coolant is fully considered under the hardware conditions of the heat sink including the heat sink housing, fan, and coolant (pump) by using the heat balance equation.

[0067] The present invention also provides an electric motor thermal management system for performing the above-described electric motor thermal management method, the system comprising:

[0068] The controller is used to acquire the physical quantities of the electric motor's thermal management system and to drive the electric motor's cooling motor.

[0069] The cooling motor has two mechanical output ports, which are used to drive the cooling pump and the fan to rotate, respectively.

[0070] Cooling pumps are used to circulate the coolant in the thermal management system.

[0071] A fan is used to force airflow between the heat sink and the outside environment for cooling.

[0072] The heat dissipation housing is used to fix the heat dissipation motor, cooling pump, and fan, and at the same time provide the cavity required for the coolant. The heat dissipation housing is made of a high thermal conductivity material, and the surface of the heat dissipation housing has a three-period minimal surface structure. The three-period minimal surface adopts the Gyroid topology (also known as the spiral icosahedral topology).

[0073] For example, the heat dissipation housing is made of a lightweight material with a thermal conductivity greater than 200 W / (m·K).

[0074] For example, the controller includes:

[0075] The bus communication unit is used to provide feedback to the flight control computer regarding the electric motor windings, power transistors, and other components.

[0076] The temperature state of the coolant;

[0077] The signal acquisition unit is used to acquire the temperature of the electric motor windings, power transistors, and coolant, and to sample the phase current and rotor position information of the cooling motor.

[0078] The instruction calculation unit calculates the feedforward amount of the vector control speed command and the q-axis current command for the cooling motor.

[0079] The PWM output unit outputs PWM based on the duty cycle calculated by vector control, and amplifies the power to drive the rotation of the cooling motor.

[0080] For example, the d-axis current command in step two is taken as Between 0.05 and 0.2 times, the The fundamental flux linkage amplitude of the cooling motor, the This is the direct-axis inductance of the heat dissipation motor.

[0081] For example, the preset weighting coefficients mentioned in step four , satisfy The The insulation class temperature of the electric motor winding, the This refers to the junction temperature of the power transistor in the electric motor.

[0082] In this embodiment of the invention, the weighting coefficient is calculated based on the proportional relationship between the two heat sources, the winding and the power transistor, and their distance from the temperature rise limit. The closer they are to the temperature rise limit, the greater their contribution to the speed command. The steady-state speed of the cooling motor is to ensure the balance between the temperatures of the two heat sources and the temperature of the coolant.

[0083] For example, the stator copper loss of the electric motor described in step five The stator iron loss of an electric motor consists of two parts: DC copper loss and AC copper loss. It comprises three parts: hysteresis loss, eddy current loss, and additional loss. The additional loss is obtained by fitting the additional loss test data of the electric motor.

[0084] For example, the power transistor switching losses of the electric motor described in step five The switching frequency of the electric motor power transistor Total energy of a single power transistor in a single switching operation Calculated .

[0085] For example, the heat loss generated by the coolant in step five The The volumetric flow rate of the coolant, The density of the coolant, the The specific heat capacity of the coolant, The volumetric flow rate is the temperature difference between the coolant inlet and outlet. The The tooth width of the cooling pump, the The module of the cooling pump, the The number of teeth of the cooling pump, the This refers to the rotational speed of the cooling pump.

[0086] For example, the heat dissipation generated by the heat dissipation shell described in step five The The heat transfer coefficient of the heat dissipation shell is... The heat dissipation area of ​​the heat sink housing is... This refers to the temperature of the heat sink housing.

[0087] For example, the heat dissipated by the fan described in step five The The airflow of the fan, the The density of air, the The specific heat capacity of air, the The airflow of the fan is the temperature difference between the air before and after passing through the heat sink housing. The calibration is based on the fan speed.

[0088] For example, the equivalent mass of the electric motor described in step five The This refers to the mass of the electric motor windings. This refers to the weight of the stator core of the electric motor. This refers to the weight of the power transistor in the electric motor.

[0089] For example, the equivalent heat capacity of the electric motor described in step five The The specific heat capacity of the electric motor windings. This refers to the specific heat capacity of the stator core of an electric motor. This is the specific heat capacity of the power tube in the electric motor.

[0090] See the instruction manual appendix Figure 1 Appendix Figure 4 Appendix Figure 5 Appendix Figure 6 The controller of the electric motor thermal management system adopts a vector control architecture, and the electric motor thermal management method takes the following steps:

[0091] S1. Collect the winding temperature of the electric motor. power transistor temperature Coolant temperature ;

[0092] S2. A vector control architecture is adopted to control the operation of the electric motor's cooling motor. The speed command for the cooling motor in vector control is zero to keep the cooling motor stationary and prevent additional stirring losses caused by the low temperature and high viscosity of the coolant when the cooling motor rotates. The d-axis current command for the cooling motor is... The The fundamental flux linkage amplitude of the cooling motor, the The direct-axis inductor of the heat dissipation motor enables rapid heating of the motor windings, thereby increasing the temperature and reducing the viscosity of the coolant;

[0093] S3. Determine the coolant temperature of the electric motor. Is it below the temperature threshold? Under current operating conditions Execute S2 again until the coolant temperature reaches the specified level. Not lower than the temperature threshold If so, then execute S4;

[0094] S4. Calculate the first temperature difference between the electric motor windings and the coolant. Calculate the second temperature difference between the power tube and coolant of the electric motor. The speed command of the cooling motor is obtained by linear combination. The preset weighting coefficients , satisfy The Temperature is the insulation class temperature of the electric motor windings. This refers to the junction temperature of the power transistor in the electric motor.

[0095] S5, Stator copper loss of the electric motor Stator iron loss Calculate the stator losses of an electric motor The stator copper loss of the electric motor The stator iron loss of an electric motor consists of two parts: DC copper loss and AC copper loss. It comprises three parts: hysteresis loss, eddy current loss, and additional loss. The additional loss is obtained by fitting experimental data of the additional loss of the electric motor, and is derived from the switching loss of the power transistor of the electric motor. Conduction loss Calculate the power transistor losses of an electric motor The switching losses of the power transistors in the electric motor The switching frequency of the electric motor power transistor Total energy of a single power transistor in a single switching operation Calculated Calculate the total losses of the electric motor. The heat loss generated by the coolant in the electric motor thermal management system Heat dissipation from the heat sink casing Heat dissipated by the fan Calculate the heat loss derived from the electric motor thermal management system The heat loss generated by the coolant The This refers to the volumetric flow rate of the coolant. The density of the coolant, The specific heat capacity of the coolant. The volumetric flow rate is the temperature difference between the coolant inlet and outlet. The For the tooth width of the cooling pump, The module of the cooling pump, The number of teeth on the cooling pump. The heat dissipation from the heat sink is the speed of the cooling pump. The Let be the heat transfer coefficient of the heat dissipation casing. This refers to the heat dissipation area of ​​the heat sink casing. The temperature of the heat sink housing, and the heat dissipation carried out by the fan. The This refers to the airflow of the fan. For the density of air, The specific heat capacity of air. The airflow of the fan is the temperature difference between the air before and after passing through the heat sink housing. The heat loss absorbed by the electric motor is calculated based on the fan speed. The equivalent mass of the electric motor Equivalent heat capacity Calculate the feedforward amount of the q-axis current command for the cooling motor. The equivalent mass of the electric motor The This refers to the mass of the electric motor windings. This refers to the weight of the stator core of the electric motor. The weight of the power transistor in the electric motor, and the equivalent heat capacity of the electric motor. The The specific heat capacity of the electric motor windings. This refers to the specific heat capacity of the stator core of an electric motor. Specific heat capacity of the power tube in an electric motor;

[0096] Step 6: According to the cooling motor speed command q-axis current command feedforward ΔI qref The duty cycle of the inverter for the cooling motor is calculated using vector control, and the output PWM is used to adjust the speed of the cooling motor and control the operation of the cooling pump and fan.

[0097] In one specific embodiment, the electric motor thermal management system is described in the appendix to the specification. Figure 2 The system includes: a controller 10, a cooling motor 20, a cooling pump 30, a fan 40, and a heat sink housing 50. The controller 10 is a storage medium for the electric motor thermal management method of the present invention, used to collect physical quantities of the electric motor thermal management system and drive the electric motor cooling motor 20. The cooling motor 20 has two mechanical output ports, used to drive the cooling pump 30 and the fan 40 to rotate respectively. The cooling pump 30 is used to realize the circulation of coolant in the thermal management system. The fan 40 is used to realize forced air cooling between the heat sink housing and the external airflow. The heat sink housing 50 is used to fix the cooling motor 20, the cooling pump 30, and the fan 40, and to provide the cavity required by the coolant. The heat sink housing 50 is made of a high thermal conductivity material and has a three-period minimal curved surface structure on its surface, which increases the heat dissipation area and improves the heat dissipation efficiency.

[0098] For example, see the appendix to the instruction manual. Figure 3The controller includes a bus communication unit 101, a signal acquisition unit 102, a command calculation unit 103, and a PWM output unit 104. The bus communication unit 101 is used to feed back the temperature status of the electric motor windings, power transistors, and coolant to the flight control computer. The signal acquisition unit 102 is used to acquire the temperature of the electric motor windings, power transistors, and coolant, and simultaneously sample the phase current and rotor position information of the cooling motor 20. The command calculation unit 103 calculates the feedforward amount of the vector control speed command and q-axis current command of the cooling motor 20. The PWM output unit 104 outputs PWM based on the duty cycle calculated by vector control, and amplifies the power to drive the rotation of the cooling motor 20.

[0099] For example, see the appendix to the instruction manual. Figure 1 Appendix Figure 4 Appendix Figure 5 Appendix Figure 6 The controller of the electric motor thermal management system adopts a vector control architecture, and the electric motor thermal management method takes the following steps:

[0100] S11. Collect the winding temperature of the electric motor. power transistor temperature Coolant temperature ;

[0101] S12. A vector control architecture is adopted to control the operation of the cooling motor of the electric motor. The speed command of the cooling motor in vector control is zero, and the d-axis current command of the cooling motor is... The The fundamental flux linkage amplitude of the cooling motor, the For cooling the motor, the direct-axis inductor;

[0102] S13. Determine the coolant temperature of the electric motor. Is it below the temperature threshold? Under current operating conditions, the coolant temperature is... Not lower than the temperature threshold Execute S14;

[0103] S14. Calculate the first temperature difference between the electric motor windings and the coolant. Calculate the second temperature difference between the power tube and coolant of the electric motor. The speed command of the cooling motor is obtained by linear combination. The preset weighting coefficients , satisfy The Temperature is the insulation class temperature of the electric motor windings. This refers to the junction temperature of the power transistor in the electric motor.

[0104] S15, Stator copper loss of the electric motor Stator iron loss Calculate the stator losses of an electric motor The stator copper loss of the electric motor The stator iron loss of an electric motor consists of two parts: DC copper loss and AC copper loss. It comprises three parts: hysteresis loss, eddy current loss, and additional loss. The additional loss is obtained by fitting experimental data of the additional loss of the electric motor, and is derived from the switching loss of the power transistor of the electric motor. Conduction loss Calculate the power transistor losses of an electric motor The switching losses of the power transistors in the electric motor The switching frequency of the electric motor power transistor Total energy of a single power transistor in a single switching operation Calculated Calculate the total losses of the electric motor. The heat loss generated by the coolant in the electric motor thermal management system Heat dissipation from the heat sink casing Heat dissipated by the fan Calculate the heat loss derived from the electric motor thermal management system The heat loss generated by the coolant The This refers to the volumetric flow rate of the coolant. The density of the coolant, The specific heat capacity of the coolant. The volumetric flow rate is the temperature difference between the coolant inlet and outlet. The For the tooth width of the cooling pump, The module of the cooling pump, The number of teeth on the cooling pump. The heat dissipation from the heat sink is the speed of the cooling pump. The Let be the heat transfer coefficient of the heat dissipation casing. This refers to the heat dissipation area of ​​the heat sink casing. The temperature of the heat sink housing, and the heat dissipation carried out by the fan. The This refers to the airflow of the fan. For the density of air, The specific heat capacity of air. The airflow of the fan is the temperature difference between the air before and after passing through the heat sink housing. The heat loss absorbed by the electric motor is calculated based on the fan speed. The equivalent mass of the electric motor Equivalent heat capacity Calculate the feedforward amount of the q-axis current command for the cooling motor. The equivalent mass of the electric motor The This refers to the mass of the electric motor windings. This refers to the weight of the stator core of the electric motor. The weight of the power transistor in the electric motor, and the equivalent heat capacity of the electric motor. The The specific heat capacity of the electric motor windings. This refers to the specific heat capacity of the stator core of an electric motor. Specific heat capacity of the power tube in an electric motor;

[0105] S16. According to the cooling motor speed command q-axis current command feedforward ΔI qref The duty cycle of the inverter for the cooling motor is calculated using vector control, and the output PWM is used to adjust the speed of the cooling motor and control the operation of the cooling pump and fan.

[0106] The principle of the electric motor thermal management method and system of this invention is as follows: Addressing the problem of severe heat generation in electric motors during the entire flight profile of an aircraft, especially during takeoff and hovering, a thermal management system based on liquid cooling combined with air cooling is constructed. Based on the losses of the electric motor, the rotational speed of the cooling motor is dynamically adjusted to ensure that the heat generated by the electric motor windings and power transistors is rapidly dissipated by the coolant in direct contact with them, achieving a balance between the electric motor temperature and the coolant temperature. Simultaneously, considering the heat accumulation effect, the temperature rise of the electric motor is estimated based on the current losses of the electric motor and the heat dissipation currently discharged by the thermal management system. This temperature rise is used as a feedforward quantity for the q-axis current command of the cooling motor, achieving effective compensation for the acceleration of the cooling motor and further improving the heat dissipation efficiency when the electric motor experiences a rapid increase in temperature under strong overload.

[0107] The method described in this invention can also be extended to electric propulsion systems, etc.

[0108] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should be covered within the protection scope of the present invention.

Claims

1. A thermal management method for an electric motor, characterized in that, include: Step 1: Collect the winding temperature of the electric motor. Power transistor temperature and coolant temperature ; Step 2: Using a vector control architecture, control the operation of the cooling motor of the electric motor. The speed command of the cooling motor vector control is zero, and the d-axis current command is a preset positive value. Step 3: Determine the coolant temperature of the electric motor. Is it below the temperature threshold? If yes, return to step two; otherwise, proceed to step four. Step 4: Based on the winding temperature of the electric motor Coolant temperature Power transistor temperature Obtain the cooling motor speed command N ref ; Step 5: Based on the equivalent mass of the electric motor Equivalent heat capacity and the heat loss P absorbed by the electric motor in Get the feedforward amount of the q-axis current command of the cooling motor. The heat loss absorbed by the electric motor is determined based on the total loss of the electric motor and the heat loss derived from the electric motor thermal management system. Step Six: According to the cooling motor speed command Feedforward quantity ΔI of the q-axis current command of the cooling motor qref The duty cycle of the inverter for the cooling motor is calculated using vector control, and the output PWM is used to adjust the speed of the cooling motor and control the operation of the cooling pump and fan.

2. The electric motor thermal management method according to claim 1, characterized in that, Obtain the cooling motor speed command N ref ,include: Obtain the winding temperature of the electric motor Coolant temperature First temperature difference ; Obtain the power tube temperature of the electric motor Coolant temperature The second temperature difference ; The radiator speed command is obtained based on the first temperature difference and the second temperature difference. The , These are the preset weighting coefficients.

3. The electric motor thermal management method according to claim 1, characterized in that, Heat absorbed by the electric motor ; Among them, P out Heat loss generated by the thermal management system of electric motor. ;P h Heat loss due to coolant drained from the thermal management system of electric motor Heat dissipation from the heat sink casing The heat dissipated by the fan; P loss The total loss of the electric motor, P m This refers to the stator losses of the electric motor. , For stator copper losses in electric motors, Stator iron loss; P p This refers to the power transistor losses in an electric motor. , This refers to the switching losses of the power transistors in the electric motor. This refers to conduction loss.

4. The thermal management method for an electric motor according to claim 1, characterized in that, Step 2 d-axis current command retrieval Between 0.05 and 0.2 times, the The fundamental flux linkage amplitude of the cooling motor, the This is the direct-axis inductance of the heat dissipation motor.

5. The electric motor thermal management method according to claim 2, characterized in that, Preset weighting coefficients , satisfy The The insulation class temperature of the electric motor winding, the This refers to the junction temperature of the power transistor in the electric motor.

6. The electric motor thermal management method according to claim 3, characterized in that, Stator copper loss of electric motor Includes DC copper losses, AC copper losses, and stator iron losses of electric motors. It includes hysteresis loss, eddy current loss, and additional loss, the latter being obtained by fitting test data of additional loss of electric motor.

7. The electric motor thermal management method according to claim 3, characterized in that, Switching losses of power transistors in electric motors The switching frequency of the electric motor power transistor Total energy of a single power transistor in a single switching operation Calculated; 。 8. The electric motor thermal management method according to claim 3, characterized in that, Heat loss from coolant The The volumetric flow rate of the coolant, The density of the coolant, the The specific heat capacity of the coolant, The volumetric flow rate is the temperature difference between the coolant inlet and outlet. The The tooth width of the cooling pump, the The module of the cooling pump, the The number of teeth of the cooling pump, the This refers to the rotational speed of the cooling pump.

9. The thermal management method for an electric motor according to claim 3, characterized in that, The heat dissipation shell dissipates heat. The The heat transfer coefficient of the heat dissipation shell is... The heat dissipation area of ​​the heat sink housing is... This refers to the temperature of the heat sink housing.

10. The electric motor thermal management method according to claim 3, characterized in that, The heat dissipated by the fan The The airflow of the fan, the The density of air, the The specific heat capacity of air, the The airflow of the fan is the temperature difference between the air before and after passing through the heat sink housing. The calibration is based on the fan speed.

11. The electric motor thermal management method according to claim 3, characterized in that, The equivalent mass of the electric motor The This refers to the mass of the electric motor windings. This refers to the weight of the stator core of the electric motor. This refers to the weight of the power transistor in the electric motor.

12. The electric motor thermal management method according to claim 11, characterized in that, The equivalent heat capacity of the electric motor The The specific heat capacity of the electric motor windings. This refers to the specific heat capacity of the stator core of an electric motor. This is the specific heat capacity of the power tube in the electric motor.

13. A thermal management system for an electric motor, characterized in that, include: A controller for performing the electric motor thermal management method as described in any one of claims 1-12; The cooling motor has two mechanical output ports, which are used to drive the cooling pump and the fan to rotate, respectively. Cooling pumps are used to circulate the coolant in the thermal management system. A fan is used to force airflow between the heat sink and the outside environment for cooling. The heat dissipation housing is used to fix the heat dissipation motor, cooling pump, and fan, and at the same time provide the cavity required for the coolant. The heat dissipation housing is made of a material with a thermal conductivity higher than the preset thermal conductivity.

14. The electric motor thermal management system according to claim 13, characterized in that, The surface of the heat dissipation housing has a three-period minimal curved surface structure.

15. The electric motor thermal management system according to claim 13, characterized in that, The controller includes: The bus communication unit is used to provide feedback to the flight control computer on the temperature status of the electric motor windings, power transistors, and coolant. The signal acquisition unit is used to acquire the temperature of the electric motor windings, power transistors, and coolant, and to sample the phase current and rotor position information of the cooling motor. The instruction calculation unit is used to calculate the feedforward amount of the vector control speed command and the q-axis current command of the cooling motor. The PWM output unit outputs PWM based on the duty cycle calculated by vector control, and amplifies the power to drive the rotation of the cooling motor.

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