A method for evaluating temperature rise performance of drive motor

Abstract

The present invention discloses a method for evaluating the temperature rise performance of a drive motor, which relates to the field of motor technology. The evaluation method comprises the following steps: 1. calibrating the output external characteristics of the drive motor; 2. conducting performance tests at different thermal equilibrium temperatures; 3. conducting operating time tests at different torques; and 3. evaluating the temperature rise performance of the drive motor according to the dynamic requirements of the entire vehicle. The method for evaluating the temperature rise performance of a drive motor provided by the present invention provides a scientific and accurate reference basis for the multi-dimensional evaluation of the temperature rise performance of the drive motor by calibrating the external characteristics of the drive motor through performance tests at different thermal equilibrium temperatures and operating time tests at different torques, thereby making the evaluation method applicable to a variety of different operating conditions and meeting the diversified development needs of new energy vehicle application scenarios.

Description

Technical Field

[0001] The present invention relates to the technical field of motors, and in particular to a method for evaluating the temperature rise performance of a drive motor. Background Art

[0002] As the power source for current new energy vehicles, the operational reliability of the drive motor is closely related to the performance of the entire vehicle. The drive motor starts operating at room temperature and its temperature continues to rise. When it exceeds the ambient temperature, it continues to absorb heat and slowly heats up, while also beginning to dissipate heat to the surrounding area. When the drive motor is in a state of thermal equilibrium and its temperature no longer rises, the difference between the drive motor temperature and the ambient temperature is called the motor temperature rise. The motor temperature rise is directly related to the insulation life of the drive motor, affecting the drive motor's efficiency and other performance indicators. Excessive motor temperature rise can even damage the drive motor. Therefore, motor temperature rise is a very important performance indicator for evaluating the quality of the drive motor.

[0003] Taking the patent with publication number CN104793141B as an example, the existing method for evaluating the temperature rise performance of the drive motor usually only evaluates the working time of the peak torque condition. However, the working conditions simulated by this evaluation method are single and the dimension is single. It cannot scientifically and accurately evaluate the temperature rise performance of the drive motor, nor can it meet the technical requirements brought about by the diversified development of new energy vehicle application scenarios. Summary of the Invention

[0004] The present invention provides a method for evaluating the temperature rise performance of a drive motor, the main purpose of which is to solve the problems existing in the prior art.

[0005] The present invention adopts the following technical solutions:

[0006] A method for evaluating the temperature rise performance of a drive motor comprises the following steps:

[0007] Step 1: Based on the set calibration conditions, calibrate the output external characteristics of the drive motor to obtain the output external characteristic curve, find the speed point where the torque decreases for the first time, and record the speed point before this speed point as the inflection point speed V t ;

[0008] Step 2: Based on the set test conditions and the output external characteristic curve of the drive motor, control the drive motor to try different torques at various speeds and record the corresponding motor winding temperature T in real time. r1 And each motor winding temperature T r1 The maintenance time t1, when a motor winding temperature T r1 The maintenance time t1 exceeds the set time t max , then record the speed and torque in the current state, and formulate different thermal equilibrium temperature torque tables;

[0009] Step 3: Based on the set test conditions, control the drive motor speed V at the inflection point t Output the set peak torque and record the motor winding temperature T at the set frequency r2 , when the motor winding temperature T r2 Reach the set temperature T max When the peak torque reaches 0, the drive motor is immediately powered off and the working time t2 of the drive motor at the peak torque is recorded, thereby drawing a table of working time at different torques at the inflection point speed;

[0010] Step 4: Set different operating conditions according to the actual vehicle operation situation, and obtain the required torque T and required speed n under different operating conditions. Compare with the torque table of different thermal equilibrium temperatures or the working time table of different torques at inflection point speeds to determine whether the thermal equilibrium temperature of the drive motor or the motor working time meets the set operating condition requirements. If so, it is determined that the temperature rise performance of the drive motor meets the vehicle power requirements. Otherwise, it is determined that the temperature rise performance of the drive motor does not meet the vehicle power requirements.

[0011] Furthermore, in step 1, the output external characteristics of the drive motor are preliminarily calibrated based on the set calibration conditions to obtain a full-speed torque table; then, the speed point where the torque decreases for the first time is found from the full-speed torque table, and the interval between this speed point and the previous speed point is refined and divided into several sub-speed points according to the set step size; then, the torque of each sub-speed point is refined and calibrated according to the set calibration method to obtain an inflection point interval speed torque table; finally, the sub-speed point where the torque decreases for the first time is found, and the sub-speed point before this sub-speed point is recorded as the inflection point speed V t .

[0012] Furthermore, in step 4, if the required speed n ≤ the inflection point speed V t , and the required torque T ≥ 60% of the peak torque, then refer to the table of working hours for different torques at the inflection point speed to determine whether the motor working time corresponding to the required torque T meets the working condition requirements.

[0013] Furthermore, in step 4, if the required speed n ≤ the inflection point speed V t , and the required torque T is less than 60% of the peak torque, or the required speed n is greater than the inflection point speed V t , then refer to the different thermal equilibrium temperature torque tables to determine whether the thermal equilibrium temperature of the drive motor corresponding to the required speed n and the required torque T meets the working condition requirements.

[0014] Furthermore, in step 2, the temperature of each motor winding T r1 They are 120℃, 130℃, 140℃ and 150℃ respectively, and the setting time t of each motor winding temperature is max Both are 30 minutes.

[0015] Furthermore, in step 3, the peak torques are set to 100% peak torque, 80% peak torque and 60% peak torque, and the temperature T is set to max is 150℃.

[0016] Furthermore, in step 4, the calculation formulas for the required torque T and the required speed n are:

[0017] (1)

[0018] (2)

[0019] Where: i g is the transmission ratio of the reducer; i0 is the transmission ratio of the main reducer; η T is the transmission efficiency; r is the wheel radius; G is the vehicle gravity; f is the rolling resistance coefficient; C D is the air resistance coefficient; A is the frontal area; u a is the speed of the car; i is the slope; δ is the rotation mass conversion coefficient; m is the mass of the car; For the car acceleration.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. The drive motor temperature rise performance evaluation method provided by the present invention provides a scientific and accurate reference basis for the multi-dimensional evaluation of the drive motor temperature rise performance by calibrating the external characteristics of the drive motor through performance tests at different thermal equilibrium temperatures and working time tests at different torques. This makes the evaluation method applicable to a variety of different operating conditions and can meet the diversified development needs of new energy vehicle application scenarios.

[0022] 2. The output external characteristic calibration method of the driving motor in the present invention performs multi-level speed division on the full speed range, thereby facilitating accurate and rapid finding of the torque inflection point of the driving motor. This calibration method has the advantages of strong applicability, simple operation and high efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a graph showing the output external characteristic of the driving motor in the present invention.

[0024] Figure 2 These are different thermal equilibrium temperature-torque curves of the drive motor in the present invention.

[0025] Figure 3 This is a curve diagram of the working time of the drive motor at different torques at the inflection point speed in the present invention. DETAILED DESCRIPTION

[0026] Specific embodiments of the present invention will be described below with reference to the accompanying drawings.

[0027] Through research experiments and empirical summary, it is found that the impact of motor temperature rise on the power performance of electric vehicles is mainly reflected in two aspects: on the one hand, the motor temperature rise will affect the power output of the drive motor. As the temperature rise increases, the output power of the drive motor will gradually decrease, thereby affecting the power performance of the electric vehicle; on the other hand, the motor temperature rise will affect the duration of the motor torque, thereby affecting the climbing power performance of the electric vehicle. Based on this, the present invention calibrates the external characteristics of the drive motor through performance tests at different thermal equilibrium temperatures and working time tests at different torques, thereby achieving a multi-dimensional evaluation of the temperature rise performance of the drive motor. The following is a detailed introduction to the evaluation method provided by the present invention in conjunction with specific embodiments:

[0028] Step 1: Calibrate the output external characteristics of the drive motor. Specifically, based on the set calibration conditions, the output external characteristics of the drive motor are calibrated on the electric drive test bench according to the motor design parameters and sample status to obtain the output external characteristic curve; find the speed point where the torque decreases for the first time from the output external characteristic curve, and record the speed point before this speed point as the inflection point speed V t . Except the inflection point speed V t The information contained in the external characteristic curve also includes: peak power, peak torque and maximum speed, etc.

[0029] The design parameters of the drive motor in this embodiment are: bus voltage: 576Vdc; continuous power: 60kW; peak power: 120kW; continuous torque: 159N•m; peak torque: 360N•m; maximum speed: 12000r / min; insulation grade: H grade.

[0030] Step 1.1: Set the calibration conditions as follows: bus voltage 576 Vdc, cooling water inlet temperature 65°C. Based on the maximum speed of 12000 rpm in the drive motor's design parameters, divide the speed into equal steps of 1000 rpm. The speed points after division are, from smallest to largest, 1000 rpm, 2000 rpm, 3000 rpm, ..., 1200 rpm.

[0031] Step 1.2: Apply peak current to the drive motor at each speed point to generate torque output, and record the torque value at that speed point. For example, at a speed point of 1000 r / min, apply peak current to the drive motor to generate torque output, and record the torque value at that point as 360 N·m. Similarly, record the torque values ​​of 360 N·m, 360 N·m, ..., 96 N·m for all speed points between 1000 r / min and 12000 r / min, respectively. Create a full-speed torque table based on this.

[0032] Table 1 Full speed torque table

[0033]

[0034] Step 1.3: Compare the torque values ​​from top to bottom in Table 1. Find the speed point (4000 rpm) where the torque first decreases. Further divide the speed points between 3000 rpm and 4000 rpm into equal steps, with M = 5 steps and a step size of 200 rpm. The divided speed points are 3000 rpm, 3200 rpm, 3400 rpm, ..., 4000 rpm, from smallest to largest.

[0035] Step 1.4: Following the method in step 1.2, record the output torques of all sub-speed points from 3200 rpm to 3800 rpm (360 N·m, 338.8 N·m, ..., 303.2 N·m), and draw a speed-torque table for the inflection point range.

[0036] Table 2 Speed ​​and torque table of inflection point range

[0037] Speed ​​(r / min) Torque (N•m) 3200 360 3400 338.8 3600 320 3800 303.2

[0038] Step 1.5: Compare the torque values ​​from top to bottom according to Table 2, and find the sub-speed point 3400r / min where the torque is less than 360N•m for the first time. The previous sub-speed point 3200r / min is the speed corresponding to the torque inflection point. Therefore, the inflection point speed V t =3200r / min.

[0039] Step 1.6: According to Table 1 and Table 2, use the speed of the drive motor as the x-axis coordinate and the torque as the y-axis coordinate to draw the output external characteristic curve of the drive motor, as shown in Figure 1 shown.

[0040] Step 2: Performance test at different thermal equilibrium temperatures. Specifically, based on the set test conditions and the output external characteristic curve of the drive motor, the drive motor is controlled to try different torques at various speeds, and the corresponding motor winding temperature T is recorded in real time. r1 And each motor winding temperature T r1 The maintenance time t1, when a motor winding temperature T r1 The maintenance time t1 exceeds the set time t max , then record the speed and torque in the current state, and formulate a torque table for different thermal equilibrium temperatures.

[0041] The test conditions set in this embodiment are: bus voltage 576Vdc, cooling water inlet temperature 65°C. The temperature of each motor winding T r1They are 120℃, 130℃, 140℃ and 150℃ respectively, and the setting time t of each motor winding temperature is max Each test lasts 30 minutes. For example, based on this test condition, the motor is driven at various speeds with varying torques until the motor winding temperature stabilizes at 150°C for 30 minutes. The speed and torque at the current state are then recorded. This method is used to complete thermal equilibrium temperature tests at 140°C, 130°C, and 120°C, and a table of torques at different thermal equilibrium temperatures is developed.

[0042] Table 3 Torque at different thermal equilibrium temperatures

[0043]

[0044] Figure 2 The torque curves for different thermal equilibrium temperatures are drawn based on Table 3.

[0045] Step 3: Test the working time of different torques. Specifically, based on the set test conditions, control the drive motor to rotate at the inflection point V t Output the set peak torque and record the motor winding temperature T at the set frequency r2 , when the motor winding temperature T r2 Reach the set temperature T max When the peak torque is reached, the drive motor is immediately powered off and the working time t2 of the drive motor at the peak torque is recorded, thereby drawing a table of working times at different torques at the inflection point speed.

[0046] The test conditions set in this embodiment are: bus voltage is set to 576Vdc, cooling water inlet temperature is 65℃. The peak torques are set to 100% peak torque, 80% peak torque and 60% peak torque respectively, and the temperature is set to T max For example: Control the speed of the drive motor at the inflection point V t Output 100% peak torque and record the motor winding temperature T at a frequency of once every 1 second r2 , when the motor winding temperature T r2 When the temperature reaches 150°C, the motor is immediately deenergized and the operating time (t2 = 63 seconds) of the drive motor at 100% peak torque is recorded. This method is then used to complete tests at 80% and 60% peak torque, recording the temperature at each moment. A table is then plotted showing the operating time at different torques at the inflection point speed.

[0047] Table 4 Working time of different torques at inflection point speed

[0048]

[0049]

[0050] Figure 3 The working time curves of different torques at the inflection point speed are drawn based on Table 4.

[0051] Step 4: Evaluate the temperature rise performance of the drive motor based on the vehicle's dynamic performance requirements. Specifically, set different operating conditions based on the actual vehicle's operation, and calculate the required torque T and required speed n under different operating conditions. Compare the table of torques at different thermal equilibrium temperatures or the table of operating hours for different torques at inflection point speeds to determine whether the thermal equilibrium temperature or operating hours of the drive motor meet the set operating condition requirements. If so, the temperature rise performance of the drive motor is determined to meet the vehicle's dynamic performance requirements. Otherwise, the temperature rise performance of the drive motor is determined to not meet the vehicle's dynamic performance requirements.

[0052] More specifically, the evaluation method for temperature rise performance is: if the required speed n ≤ the inflection point speed V t , and the required torque T ≥ 60% of the peak torque, then refer to the table of working hours of different torques at the inflection point speed to determine whether the motor working time corresponding to the required torque T meets the working condition requirements; if the required speed n ≤ inflection point speed V t , and the required torque T is less than 60% of the peak torque, or the required speed n is greater than the inflection point speed V t , then refer to the different thermal equilibrium temperature torque tables to determine whether the thermal equilibrium temperature of the drive motor corresponding to the required speed n and the required torque T meets the working condition requirements.

[0053] Step 4.1: Set different operating conditions according to the actual vehicle operation situation, and calculate the required torque T and required speed n of the drive motor under each operating condition according to formulas (1) and (2).

[0054] (1)

[0055] (2)

[0056] Where: i g is the transmission ratio of the reducer; i0 is the transmission ratio of the main reducer; η T is the transmission efficiency; r is the wheel radius; G is the vehicle gravity; f is the rolling resistance coefficient; C D is the air resistance coefficient; A is the frontal area; u a is the car speed (km / h); i is the slope; δ is the rotation mass conversion factor; m is the car mass; For the car acceleration.

[0057] This embodiment sets two typical operating conditions, and the parameters of each operating condition are shown in Table 5:

[0058] Table 5 Operating condition parameters

[0059]

[0060] Substituting the parameters of each operating condition into formula (1) and (2), the required torque T and required speed n under each operating condition are obtained as shown in the following table:

[0061] Table 6 Operation Condition Calculation Table

[0062] Operating conditions Required torque T (N•m) Required speed n (r / min) Operating condition 1 48 10500 Operating condition 2 300 2500

[0063] Step 4.2: Compare the table of torques at different thermal equilibrium temperatures or the table of operating hours at different torques at inflection point speeds to determine whether the temperature rise performance of the drive motor meets the actual vehicle operating requirements of each operating condition.

[0064] (a) Temperature rise performance evaluation based on operating condition 1:

[0065] The required speed n in operating condition 1 is 10500r / min, the required torque T is 48N·m, and the inflection point speed V of the drive motor is t =3200r / min, the peak torque is 360N·m, so the required speed n of this operating condition is greater than the inflection point speed V of the drive motor t , the required torque T is less than 60% of the peak torque. It can be seen that this operating condition is a steady-state condition with high speed and low torque. The impact of temperature rise performance on the drive motor is mainly on its power output. Therefore, it is necessary to evaluate whether the thermal equilibrium temperature of the drive motor meets the temperature upper limit requirement of this operating condition when the speed is 10500r / min and the torque is 48N•m.

[0066] Table 5 shows that the upper temperature limit for Operating Condition 1 is 140°C. Comparing this with Table 3, we see that, at a thermal equilibrium temperature of 140°C, when the drive motor speed is 10,000 r / min, the torque is 53.1 N·m, and when the drive motor speed is 11,000 r / min, the torque is 48.3 N·m. This indicates that when the drive motor speed is 10,500 r / min and the required torque is 48 N·m, its thermal equilibrium temperature must be less than 140°C. This indicates that the drive motor's temperature rise performance meets the vehicle dynamics requirements for Operating Condition 1.

[0067] (b) Temperature rise performance evaluation based on operating condition 2:

[0068] The required speed n in operating condition 2 is 2500r / min, the required torque T is 300N·m, and the inflection point speed V of the drive motor is t =3200r / min, the peak torque is 360N·m, so the required speed n of this operating condition is less than the inflection point speed V of the drive motor tThe required torque T is close to 83% of the peak torque. It can be seen that this operating condition is a low-speed and high-torque climbing condition. The impact of temperature rise performance on the drive motor is mainly the impact on the duration of its output torque. Therefore, it is necessary to evaluate whether the operating time of the drive motor meets the operating time requirements of this operating condition when the speed is 2500r / min and the torque is 300N•m.

[0069] Table 5 shows that the required operating time for Operating Condition 2 is 67 seconds. Comparing this with Table 4, we see that at the inflection point speed, the drive motor's operating time corresponding to 100% peak torque is 63 seconds, and at 80% peak torque is 107 seconds. Therefore, the operating time corresponding to 83% peak torque is 63 < t < 107 seconds. Further interpolation indicates that the drive motor's operating time at 83% peak torque at the inflection point speed is approximately 100 seconds. This indicates that when the drive motor's speed is 2500 r / min and its torque is 300 N·m, its operating time exceeds the required operating time for Operating Condition 2. Therefore, the drive motor's temperature rise performance meets the vehicle dynamics requirements for Operating Condition 2.

[0070] The above is only a specific implementation of the present invention, but the design concept of the present invention is not limited to this. Any non-substantial changes to the present invention using this concept shall be deemed as an infringement of the protection scope of the present invention.

Claims

1. A method for evaluating the temperature rise performance of a drive motor, characterized by: The steps include: Step 1: Based on the set calibration conditions, calibrate the output external characteristics of the drive motor to obtain the output external characteristic curve, find the speed point where the torque decreases for the first time, and record the speed point before this speed point as the inflection point speed V t ; Step 2: Based on the set test conditions and the output external characteristic curve of the drive motor, control the drive motor to try different torques at various speeds and record the corresponding motor winding temperature T in real time. r1 And each motor winding temperature T r1 The maintenance time t1, when a motor winding temperature T r1 The maintenance time t1 exceeds the set time t max , then record the speed and torque in the current state, and formulate different thermal equilibrium temperature torque tables; Step 3: Based on the set test conditions, control the drive motor speed V at the inflection point t Output the set peak torque and record the motor winding temperature T at the set frequency r2 , when the motor winding temperature T r2 Reach the set temperature T max When the peak torque reaches 0, the drive motor is immediately powered off and the working time t2 of the drive motor at the peak torque is recorded, thereby drawing a table of working time at different torques at the inflection point speed; Step 4: Set different operating conditions according to the actual vehicle operation situation, and obtain the required torque T and required speed n under different operating conditions. Compare with the table of torques at different thermal equilibrium temperatures or the table of working hours with different torques at inflection point speeds to determine whether the thermal equilibrium temperature or working hours of the drive motor meet the set operating condition requirements. If so, it is determined that the temperature rise performance of the drive motor meets the vehicle power requirements. Otherwise, it is determined that the temperature rise performance of the drive motor does not meet the vehicle power requirements. In this step, if the required speed n ≤ the inflection point speed V t , and the required torque T ≥ 60% of the peak torque, then refer to the table of working hours of different torques at the inflection point speed to determine whether the motor working time corresponding to the required torque T meets the working condition requirements; if the required speed n ≤ inflection point speed V t , and the required torque T is less than 60% of the peak torque, or the required speed n is greater than the inflection point speed V t , then refer to the different thermal equilibrium temperature torque tables to determine whether the thermal equilibrium temperature of the drive motor corresponding to the required speed n and the required torque T meets the working condition requirements.

2. The method for evaluating the temperature rise performance of a drive motor according to claim 1, wherein: In step 1, the output external characteristics of the drive motor are preliminarily calibrated based on the set calibration conditions to obtain a full-speed torque table; then, the speed point where the torque decreases for the first time is found from the full-speed torque table, and the interval between this speed point and the previous speed point is refined and divided into several sub-speed points according to the set step size; then, the torque of each sub-speed point is refined and calibrated according to the set calibration method to obtain an inflection point interval speed torque table; finally, the sub-speed point where the torque decreases for the first time is found, and the sub-speed point before this sub-speed point is recorded as the inflection point speed V t .

3. The method for evaluating the temperature rise performance of a drive motor according to claim 1, wherein: In step 2, the temperature of each motor winding T r1 They are 120℃, 130℃, 140℃ and 150℃ respectively, and the setting time t of each motor winding temperature is max Both are 30 minutes.

4. The method for evaluating the temperature rise performance of a drive motor according to claim 1, wherein: In step 3, the peak torques are set to 100% peak torque, 80% peak torque and 60% peak torque, and the temperature is set to T max is 150℃.

5. The method for evaluating the temperature rise performance of a drive motor according to claim 1, wherein: In step 4, the required torque T and required speed n are calculated as follows: （1） （2） Where: i g is the transmission ratio of the reducer; i0 is the transmission ratio of the main reducer; η T is the transmission efficiency; r is the wheel radius; G is the vehicle gravity; f is the rolling resistance coefficient; C D is the air resistance coefficient; A is the frontal area; u a is the speed of the car; i is the slope; δ is the rotation mass conversion coefficient; m is the mass of the car; For the car acceleration.

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