Electromagnetic compatibility test device and method for shaft current of hub motor

Abstract

The invention relates to the technical field of electromagnetic compatibility testing, in particular to an electromagnetic compatibility testing device and method for the shaft current of a hub motor, and the device comprises a shielding chamber, a system master controller, a dynamometer, a hub motor tool and a testing system. A dynamometer, a hub motor tool and a test system are arranged in the shielding chamber; the hub motor tool is used for installing and fixing a hub motor to be tested. An output shaft is designed at the rotor end of the hub motor, and the hub motor is connected with the dynamometer through the output shaft. The test system is used for measuring the shaft current of the hub motor; the system master controller is used for controlling the wheel hub motor to operate under various working conditions and collecting shaft current under each working condition; and obtaining an electromagnetic compatibility test result according to the shaft current. The electromagnetic compatibility and reliability of the hub motor and the control system thereof can be improved.

Description

Technical Field

[0001] The present application relates to the technical field of electromagnetic compatibility testing, and more particularly, to an electromagnetic compatibility test device and method for the shaft current of a wheel hub motor. Background Art

[0002] With the rapid development of new energy vehicles and intelligent electric drive technologies, wheel hub motors have gradually become an important part of the drive systems of new energy vehicles due to their advantages such as high integration, high efficiency, and flexible layout. However, during operation, due to the high-frequency switching of inverters and parasitic capacitance effects, wheel hub motors are prone to generating shaft currents, which may form loops through bearings, leading to bearing electro-erosion and affecting the motor life and the electromagnetic compatibility (EMC) performance of the entire vehicle.

[0003] Current electromagnetic compatibility testing methods mainly focus on the overall EMC performance of the entire vehicle or the power system, such as radiated emission (RE), conducted emission (CE), and immunity testing. However, there is a lack of systematic research on the electromagnetic compatibility impact of the shaft current of wheel hub motors, and existing testing standards do not specify dedicated measurement methods for shaft currents. Therefore, there is an urgent need for an electromagnetic compatibility test method for the shaft current of wheel hub motors that can simulate real operating conditions, which should have accurate shaft current measurement capabilities, comprehensive electromagnetic compatibility analysis means, and be applicable to the EMC anechoic chamber test environment to ensure the accuracy and repeatability of test results. Summary of the Invention

[0004] The purpose of the present application is to provide an electromagnetic compatibility test device and method for the shaft current of a wheel hub motor to conduct electromagnetic compatibility tests on the shaft current of the wheel hub motor.

[0005] To achieve the above purpose, the present application adopts the following technical solutions: In a first aspect, the present application provides an electromagnetic compatibility test device for the shaft current of a wheel hub motor, including: a shielding chamber, a system master controller, a dynamometer, a wheel hub motor tooling, and a test system; The shielding chamber is provided with a dynamometer, a wheel hub motor tooling, and a test system; The wheel hub motor tooling is used for installing and fixing the wheel hub motor to be tested; The rotor end of the wheel hub motor is designed with an output shaft, which is connected to the dynamometer through the output shaft; The test system is used for measuring the shaft current of the wheel hub motor; The system master controller is used for controlling the wheel hub motor to operate under multiple working conditions and collecting the shaft current under each working condition; and obtaining the electromagnetic compatibility test results based on the shaft current.

[0006] In a second aspect, the present application provides an electromagnetic compatibility test method for the shaft current of a wheel hub motor, which applies an electromagnetic compatibility test device for the shaft current of a wheel hub motor. The method includes: Based on the electromagnetic compatibility test device for the shaft current of a wheel hub motor, arrange the test environment; In the test environment, control the wheel hub motor under test to operate under multiple working conditions, and collect the shaft current under each working condition; wherein, the multiple working conditions include multiple rotational speeds, multiple torques, and multiple loads of the wheel hub motor; According to the shaft current under each working condition, calculate the total energy and common mode interference voltage within a specified frequency band.

[0007] Compared with the prior art, the beneficial effects of the present application are as follows: The present application provides an electromagnetic compatibility test method for the shaft current of a wheel hub motor, which can effectively evaluate the shaft current characteristics of the wheel hub motor under different operating conditions and its influence on the electromagnetic compatibility (EMC) performance, thereby improving the electromagnetic compatibility and reliability of the wheel hub motor and its control system. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0009] Figure 1 is a schematic structural diagram of an electromagnetic compatibility test device for the shaft current of a wheel hub motor provided by an embodiment of the present application; Figure 2 is a schematic flow diagram of an electromagnetic compatibility test method for the shaft current of a wheel hub motor provided by an embodiment of the present application; Wherein, 1 - shielding room; 11 - LV power line; 12 - HV power line; 13 - LV power supply; 14 - additional shielding box; 15 - HV power supply; 16 - power line filter; 17 - fiber optic feedthrough; 18 - receiver; 19 - system master control; 2 - reference ground plane; 20 - wall plate connector; 21 - high-quality coaxial cable; 22 - optical fiber; 23 - grounding strap; 24 - wheel hub motor; 25 - wheel hub motor tooling; 26 - output shaft of the wheel hub motor tooling; 27 - dynamometer connecting bearing; 28 - dynamometer; 29 - load; 30 - wheel hub motor controller; 3 - low relative permittivity material support; 4 - current probe; 5 - LV wire harness; 6 - HV wire harness; 7 - optoelectronic conversion device; 8 - impedance matching network; 9 - LV AN; 10 - HV AN. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0010] The exemplary embodiments of the present application will be described below in conjunction with the accompanying drawings. Various details of the embodiments of the present application are included to facilitate understanding, and they should be considered merely exemplary. Therefore, those of ordinary skill in the art should recognize that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of the present application. Similarly, descriptions of well-known functions and structures are omitted in the following description for clarity and conciseness.

[0011] An electromagnetic compatibility test device for the shaft current of a wheel hub motor is provided in an embodiment of the present application. Refer to Figure 1 , and it includes at least a shielding room 1, a system master control 19, a dynamometer 28, a wheel hub motor tooling 25, and a test system. The positions, connection relationships, and functions of each component will be introduced in detail below.

[0012] The shielding room 1 is usually welded by metal plates to form a closed space to isolate external electromagnetic interference. The inner walls, ceiling, and floor are all covered with high-performance electromagnetic wave absorbing materials to effectively absorb reflected waves, reduce the multipath effect, and ensure the purity of the test environment. A dynamometer 28, a wheel hub motor tooling 25, and a test system are arranged inside the shielding room 1.

[0013] The dynamometer 28 (also known as a dynamometer) is a key instrument for the performance of a wheel hub motor. Its core function is to analyze the power performance of the wheel hub motor 24 by measuring parameters such as torque and speed. In this embodiment, an output shaft is designed at the rotor end of the wheel hub motor 24, and the dynamometer 28 is connected through this output shaft to output the torque of the wheel hub motor 24 to the system master control 19. The dynamometer 28 is powered by a dynamometer power supply. The dynamometer 28 meets the maximum working conditions of 6000 rpm and 500 N·m. The dynamometer 28 cooperates with the wheel hub motor 24, and the dynamometer 28 outputs torque to simulate the working state of the wheel hub motor 24. The dynamometer 28 is connected to the output shaft 26 of the wheel hub motor tooling through a dynamometer connecting bearing 27.

[0014] The wheel hub motor tooling 25 is used to install and fix the wheel hub motor 24 to be tested.

[0015] The test system is used to measure the shaft current of the wheel hub motor 24 and transmit the shaft current to the system master control 19. The system master control 19 is connected to an optical fiber 22 through an optical fiber feedthrough 17. The system master control 19 is used to control the wheel hub motor 24 to operate under various working conditions and collect the shaft current under each working condition; and, obtain the electromagnetic compatibility test results based on the shaft current. Among them, the operating conditions of the wheel hub motor 24 include various speeds, various torques, and various loads of the wheel hub motor 24.

[0016] Optionally, the system master control 19 includes: a motor drive controller, a load control unit, and a data acquisition and processing system.

[0017] Among them, the motor drive controller is used to provide an analog road load for the measured in-wheel motor 24, so that the in-wheel motor 24 operates at different speeds and different torques. The load control unit is used to control the load 29 (for the power recovery condition), so as to match the output of the power distribution unit of the in-wheel motor 24, and is applicable to the in-wheel motor 24 with a power recovery function. The load 29 is, for example, 50 Ω. The data acquisition and processing system is used to collect the shaft current of the in-wheel motor 24 under different working conditions, and obtain the electromagnetic compatibility test results according to the shaft current. The load 29, HV AN 10 and the impedance matching network 8 are placed in the additional shielding box 14.

[0018] Optionally, the electromagnetic compatibility test device for the in-wheel motor shaft current provided in this embodiment further includes an HV power supply 15, an LV power supply 13 and multiple groups of filters, such as a power line filter 16. Among them, the LV power supply 13 is, for example, a 12V, 24V or 48V battery. The HV power supply 15 is a high voltage power supply, and the LV power supply 13 is a low voltage power supply. The LV power supply 13 is connected to the LV AN 9 through the LV power line 11. The LV AN 9 is a low voltage artificial network.

[0019] Among them, multiple groups of filters are used to filter the HV power line 12 of the HV power supply 15, and the HV power line 12 is double-layer shielded; the HV power supply 15 and the LV power supply 13 are used to supply power to the in-wheel motor 24, simulating various voltage, current and frequency conditions, so as to ensure that the power supply environment of the in-wheel motor 24 under various conditions during the test is consistent with the actual use situation, thereby realizing the authenticity and reliability of the test results. The HV power supply 15 and the LV power supply 13 can be set according to the actual situation to simulate various different conditions such as voltage, current, and frequency to meet various test requirements. Through the use of this power supply, the electromagnetic compatibility performance of the in-wheel motor 24 under different conditions can be accurately evaluated, providing strong support for the development and debugging of the in-wheel motor 24.

[0020] Optionally, the test system includes: a current probe 4 and a receiver 18. The current probe 4 is connected through the RF cable interface in the shielding chamber 1, and the current (measured by the current probe 4) is transmitted to the receiver 18 outside the shielding chamber 1 through a high-quality coaxial cable 21. The receiver 18 then analyzes and obtains the shaft current and transmits the shaft current to the system master control 19. The high-quality coaxial cable 21 can effectively shield external interference. The current probe 4 is fixed at the position of the output shaft 26 of the in-wheel motor tooling, and the center of the current probe 4 coincides with the axis of the output shaft of the in-wheel motor 24 and does not touch, so as to accurately measure the shaft current. The receiver 18 is connected to the high-quality coaxial cable 21 through the wall plate connector 20.

[0021] Optionally, the device further includes a test table. On the test table are placed the hub motor 24 to be tested (fixed on the hub motor tooling 25), the HV harness 6 (including HV+ and HV-), the LV harness 5, the HV AN 10, the LV AN 9, the optoelectronic conversion device 7, and the LV power supply 13. Among them, the HV AN 10 is a High Voltage Artificial Network.

[0022] The control instruction of the system master controller 19 is transmitted into the shielding room 1 in the form of an optical signal. The optoelectronic conversion device 7 in the shielding room 1 converts the optical signal into an electrical signal and then controls the hub motor controller 30, so that the hub motor 24 operates under different rotational speed and torque conditions. Similarly, after passing through the optoelectronic conversion device 7, the control instruction of the system master controller 19 can also control the load 29 size through the system master controller 19 to match the output of the power distribution unit of the hub motor 24.

[0023] Optionally, the device further includes a cloud server (not shown) and a wireless communication device (not shown); the wireless communication device is used to transmit data between the cloud server and the system master controller 19. For example, the system master controller 19 sends the shaft current and electromagnetic compatibility test results to the cloud server, and the cloud server sends control instructions to the system master controller 19. Remote monitoring and adjustment of control strategies can be achieved through cloud interaction.

[0024] The grounding strap 23 is used to connect to the ground to ensure electrical safety.

[0025] Figure 2 is a flowchart of an electromagnetic compatibility test method for the shaft current of a hub motor provided by an embodiment of the present application, applying the electromagnetic compatibility test device for the shaft current of a hub motor provided by the foregoing embodiment. Figure 2 The method shown includes: S110. Based on the electromagnetic compatibility test device for the shaft current of a hub motor, arrange the test environment.

[0026] S120. In the test environment, control the hub motor to be tested to operate under various conditions, and collect the shaft current under each condition.

[0027] First, place the hub motor 24 to be tested on the test table, place the hub motor 24 on the hub motor tooling 25 for installation and fixation. The rotor end of the hub motor 24 is designed with an output shaft, and this output shaft is connected to the output shaft 26 of the hub motor tooling. The output shaft 26 of the hub motor tooling is connected to the output shaft of the dynamometer 28. Refer to Figure 1, the HV power supply 15 supplies power to the in-wheel motor controller 30 and the in-wheel motor 24 through the power line filter 16, the HV AN 10, and the impedance matching network 8. The LV power supply 13 (i.e., the battery, providing 12V / 24V / 48V voltage) supplies power to the in-wheel motor controller 30 and the in-wheel motor 24 through the LV AN 9.

[0028] The length of the LV harness 5 is 1700±300, the length of the HV harness 6 should be 1700±300 mm, the length parallel to the front edge of the reference ground plane 2 should be 1500 mm±75 mm, and the length of the three-phase line between the in-wheel motor 24 and the in-wheel motor controller 30 should be less than 1000 mm. The in-wheel motor 24 should be placed on the bench of the dynamometer 28, and all harnesses should be placed on the non-conductive, low relative dielectric constant material support 3 and at a position 50mm±5mm above the reference ground plane 2. The LV harness 5 should be placed at least 200mm from the front edge of the reference ground plane 2, and the spacing between the LV harness 5 and the HV harness 6 should be 100±10mm. The housings of the in-wheel motor 24 and the in-wheel motor controller 30 should be directly or connected to the reference ground plane 2 through a specified impedance.

[0029] The system master control 19 is used to load the operating conditions of the measured in-wheel motor 24, that is, to provide a simulated road load for the measured in-wheel motor 24 so that the in-wheel motor 24 operates at different speeds and different torques. The in-wheel motor 24 outputs speed through the output shaft 26 of the in-wheel motor tooling and outputs torque through the dynamometer 28.

[0030] Then, the shaft current electromagnetic compatibility test is carried out. A non-metallic, low relative dielectric constant (εr≤1.4) fixture is used to fix the current probe 4 on one side of the output shaft 26 of the in-wheel motor tooling. The current probe 4 should not be in direct contact with the output shaft 26 of the in-wheel motor tooling, and the center of the current probe 4 should coincide with the axis of the output shaft of the in-wheel motor 24. For example, the shaft current is measured using the current probe 4 at an interval distance d from the output shaft of the in-wheel motor 24 (the recommended d value is 50 mm±5mm).

[0031] S130. Calculate the total energy and common-mode interference voltage in the specified frequency band according to the shaft current under each operating condition.

[0032] Optionally, perform a fast Fourier transform on the shaft current i(t) in the time domain to obtain the spectral characteristics .

[0033] ; where i(t) is the shaft current in the time domain and j is the imaginary unit, is the frequency term. represents the current at frequency The amplitude distribution under [conditions], where F is the Fast Fourier Transform algorithm. Analyze whether there are high-amplitude harmonics, switching frequency components, or their multiple frequency components in the spectrum. This step is implemented in the software-built-in application of the system master control 19.

[0034] According to the spectral characteristics Obtain the spectral power density, integrate the spectral power density within a specified frequency band to obtain the total energy within the specified frequency band. Specifically, define the shaft current spectral power density (Power Spectral Density, PSD) as an electromagnetic interference (Electromagnetic Interference, EMI) risk reference index: ; where PSD() is the calculation formula for the spectral power density.

[0035] Calculate the total energy within a certain frequency band as the EMI evaluation parameter , for example: ; where 150 kHz to 30 MHz is the disturbance frequency range in the typical EMC standard.

[0036] According to the equivalent impedance of the in-wheel motor bearing to the grounding path and the said spectral characteristics, obtain the common-mode interference voltage : ; where is the equivalent impedance of the in-wheel motor bearing to the grounding path, is the common-mode voltage distribution that may cause EMI.

[0037] Optionally, after calculating the total energy within the specified frequency band and the common-mode interference voltage according to the shaft current under each working condition, it further includes: pre-conducting electromagnetic compatibility tests on the in-wheel motor using the conducted emission current method to obtain the frequency points of conducted interference; calculating the correlation between the frequency points of the conducted interference and the spectral peak in the spectral characteristics; if the correlation is greater than the set threshold, it is determined that the shaft current has an impact on the electromagnetic compatibility performance of the in-wheel motor.

[0038] For example, the conducted EMI test includes the conducted emission current method and the voltage method, and equipment such as a linear impedance stabilization network (LISN) and a current probe are required to build a test platform. Follow the CISPR 25 or CISPR-22 standard, conduct tests through the voltage method (such as peak limit detection) and the transient pulse method, measure the conducted radiation through a current probe, and obtain the frequency points of conducted interference.

[0039] Take Compare the spectral peaks with the frequency points of EMI conducted interference, analyze the correlation between the two in terms of frequency and amplitude, and further calculate the correlation coefficient: ; where ρ is the correlation coefficient, represents the interference current value at frequency f in the EMI test, represents the amplitude distribution of the current at frequency , cov() is the covariance, is the variance of is the variance of The larger it is, the greater the impact of the shaft current on the electromagnetic compatibility performance of the in-wheel motor. For example, when the correlation coefficient approaches 1, it indicates that the shaft current has a significant impact on EMC.

[0040] This application provides a method for electromagnetic compatibility testing of the shaft current of an in-wheel motor, which can effectively evaluate the shaft current characteristics of the in-wheel motor under different operating conditions and its impact on the electromagnetic compatibility (EMC) performance, thereby improving the electromagnetic compatibility and reliability of the in-wheel motor and its control system. Through current probes and spectrum analysis, real-time monitoring and spectrum analysis of the shaft current of the in-wheel motor are achieved, effectively capturing the shaft current characteristics under different operating conditions, and improving the measurement accuracy and data reliability. Using an electromagnetic compatibility shielding chamber and a standardized test layout, external electromagnetic interference is effectively shielded, and the repeatability and consistency of the test results are improved, providing a reliable basis for the EMC design and improvement of the in-wheel motor. By measuring and analyzing the propagation path and influencing factors of the shaft current, this application can optimize the motor insulation design, shielding grounding scheme, and control strategy, thereby reducing the risk of bearing electro-erosion and improving the service life and reliability of the motor.

[0041] This application conducts tests in a shielding chamber to reduce external electromagnetic interference and ensure the accuracy of measurement data. At the same time, by optimizing the grounding method and shielding structure, the influence of the parasitic capacitance effect on the test results is reduced. Using high-frequency current probes, slip rings / shunt resistors, oscilloscopes, and spectrum analyzers, etc., the magnitude, spectrum characteristics, and propagation path of the shaft current are accurately monitored, and the influence of different working conditions on the test results of the shaft current of electromagnetic conducted emissions is analyzed.

[0042] After analyzing the test data, it can be used to optimize the shielding structure, grounding method, and control strategy of the in-wheel motor. For example, adjusting the inverter pulse width modulation (PWM) method to reduce the high-frequency common-mode voltage and reduce the generation of shaft current from the source. In addition, the adverse impact of the shaft current on the motor life can be reduced by optimizing the bearing insulation design.

[0043] This application is applicable to the EMC testing of in-wheel motors, electric drive systems and new energy vehicles, providing technical support for the electromagnetic compatibility optimization, control strategy improvement and certification of related products, and enhancing the electromagnetic compatibility performance and long-term stability of the system.

[0044] It should be understood that various forms of the processes shown above can be used, with steps reordered, added or deleted. For example, the steps described in this application can be executed in parallel, sequentially or in a different order, as long as the desired results of the technical solutions disclosed in this application can be achieved, and no limitations are imposed herein.

[0045] The above specific embodiments do not constitute a limitation on the protection scope of this application. Those skilled in the art should understand that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions and improvements made within the spirit and principles of this application shall be included within the protection scope of this application.

Claims

1. An electromagnetic compatibility test device for the shaft current of a wheel hub motor, characterized in that Including: A shielding room, a system master control, a dynamometer, a wheel hub motor tooling, and a test system; Inside the shielding room, there are a dynamometer, a wheel hub motor tooling, and a test system; The wheel hub motor tooling is used to install and fix the wheel hub motor to be tested; The rotor end of the wheel hub motor is designed with an output shaft, and the output shaft is connected to the dynamometer; The test system is used to measure the shaft current of the wheel hub motor; The system master control is used to control the wheel hub motor to operate under various working conditions and collect the shaft current under each working condition; And obtain the electromagnetic compatibility test result based on the shaft current.

2. The electromagnetic compatibility test device for the shaft current of the in-wheel motor according to claim 1, characterized in that It also includes: A high-voltage power supply, a low-voltage power supply, and multiple groups of filters; The multiple groups of filters are used to filter the high-voltage power line of the high-voltage power supply; The high-voltage power supply and the low-voltage power supply are used to supply power to the wheel hub motor, simulating various voltage, current, and frequency working conditions.

3. The electromagnetic compatibility test device for the shaft current of a wheel hub motor according to claim 1, characterized in that The test system includes: a current probe and a receiver; The current probe is connected through the RF cable interface inside the shielding room, and the current is transmitted to the receiver outside the shielding room through the RF cable; The current probe is fixed at the position of the output shaft of the wheel hub motor tooling, and the center of the current probe coincides with the axis of the output shaft of the wheel hub motor and does not touch.

4. The electromagnetic compatibility test device for the shaft current of the in-wheel motor according to claim 1, characterized in that, It also includes a test table; On the test table, there are placed the wheel hub motor to be tested, a high-voltage harness, a low-voltage harness, a high-voltage artificial power network, a low-voltage artificial power network, an optoelectronic conversion device, and a low-voltage power supply.

5. The electromagnetic compatibility test device for the shaft current of a wheel hub motor according to claim 4, characterized in that, The system master control includes: A motor drive controller, which is used to provide an analog road load for the wheel hub motor to be tested; A load control unit, which is used to match the output of the power distribution unit of the wheel hub motor; A data acquisition and processing system, which is used to acquire the shaft current of the wheel hub motor under different working conditions and obtain the electromagnetic compatibility test result based on the shaft current.

6. The electromagnetic compatibility test device for the shaft current of the in-wheel motor according to claim 5, characterized in that, It also includes: a cloud server and a wireless communication device; The wireless communication device is used to transmit data between the cloud server and the system master control.

7. An electromagnetic compatibility test method for the shaft current of a wheel hub motor, characterized in that, Applying the electromagnetic compatibility test device for the shaft current of the wheel hub motor according to any one of claims 1-6, the method includes: Based on the electromagnetic compatibility test device for the shaft current of the wheel hub motor, arrange the test environment; In the test environment, control the wheel hub motor to be tested to operate under various working conditions and collect the shaft current under each working condition; among them, the various working conditions include various rotational speeds, various torques, and various loads of the wheel hub motor; According to the shaft current under each working condition, calculate the total energy and the common-mode interference voltage within the specified frequency band.

8. The method according to claim 7, wherein Calculating the total energy and the common-mode interference voltage within the specified frequency band according to the shaft current under each working condition, including: Performing a fast Fourier transform on the shaft current in the time domain to obtain the spectral characteristics; Obtain the spectral power density according to the spectral characteristics; Integrate the spectral power density within the specified frequency band to obtain the total energy within the specified frequency band; According to the equivalent impedance of the wheel hub motor bearing to the grounding path and the spectral characteristics, obtain the common-mode interference voltage.

9. The method according to claim 8, wherein After calculating the total energy and the common-mode interference voltage within the specified frequency band according to the shaft current under each working condition, it further includes: Previously, perform an electromagnetic compatibility test on the wheel hub motor using the conducted emission current method to obtain the frequency points of the conducted interference. Calculate the correlation between the frequency points of the conducted interference and the spectral peak in the spectral characteristics; If the correlation is greater than the set threshold, it is determined that the shaft current has an impact on the electromagnetic compatibility performance of the in-wheel motor.

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