Electromagnetic compatibility test device and method for hub motor shaft current

Abstract

This application relates to the field of electromagnetic compatibility testing technology, and more specifically, to an electromagnetic compatibility testing device and method for hub motor shaft current. The device comprises: a shielded room, a system master control, a dynamometer, a hub motor tooling, and a testing system. The shielded room is provided with a dynamometer, a hub motor tooling, and a testing system. The hub motor tooling is used to install and secure the hub motor under test. The hub motor rotor end is provided with an output shaft connected to the dynamometer via the output shaft. The testing system is used to measure the hub motor shaft current. The system master control is used to control the hub motor to operate under various operating conditions and collect the shaft current under each operating condition. Furthermore, electromagnetic compatibility test results are obtained based on the shaft current. This application can improve the electromagnetic compatibility and reliability of the hub motor and its control system.

Description

Technical Field

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

[0002] With the rapid development of new energy vehicles and intelligent electric drive technologies, in-wheel motors (IWMs) have become a crucial component of new energy vehicle drive systems due to their high integration, high efficiency, and flexible layout. However, during operation, IWMs are prone to generating shaft currents due to the high-frequency switching of the inverter and the effects of parasitic capacitance. This current can form a loop through the bearings, leading to bearing corrosion and affecting the motor's lifespan and the vehicle's electromagnetic compatibility (EMC) performance.

[0003] Current EMC testing methods primarily focus on the overall EMC performance of the vehicle or powertrain, such as radiated emission (RE), conducted emission (CE), and immunity testing. However, there is a lack of systematic research on the EMC impact of in-wheel motor shaft current, and existing test standards do not specifically define measurement methods for shaft current. Therefore, an EMC test method for in-wheel motor shaft current that can simulate real-world operating conditions is urgently needed. This method should include precise shaft current measurement capabilities, comprehensive EMC analysis tools, and be suitable for use in EMC darkroom testing environments to ensure accurate and repeatable test results. Summary of the Invention

[0004] The purpose of this application is to provide an electromagnetic compatibility test device and method for the shaft current of a hub motor, so as to perform an electromagnetic compatibility test on the shaft current of the hub motor.

[0005] In order to achieve the above objectives, this application adopts the following technical solutions:

[0006] In a first aspect, the present application provides an electromagnetic compatibility test device for hub motor shaft current, comprising: a shielded room, a system master control, a dynamometer, a hub motor tooling, and a test system;

[0007] The shielded room is equipped with a dynamometer, a hub motor tooling and a test system;

[0008] The hub motor fixture is used to install and fix the hub motor to be tested;

[0009] The rotor end of the hub motor is designed with an output shaft, which is connected to the dynamometer via the output shaft;

[0010] The test system is used to measure the shaft current of the hub motor;

[0011] The system master control is used to control the hub motor to operate under multiple working conditions and collect shaft current under each working condition; and obtain electromagnetic compatibility test results based on the shaft current.

[0012] In a second aspect, the present application provides an electromagnetic compatibility test method for a hub motor shaft current, using an electromagnetic compatibility test device for a hub motor shaft current, the method comprising:

[0013] Arrange the test environment based on the electromagnetic compatibility test device of the hub motor shaft current;

[0014] In the test environment, the hub motor under test is controlled to operate under multiple operating conditions, and the shaft current under each operating condition is collected; wherein the multiple operating conditions include multiple speeds, multiple torques, and multiple loads of the hub motor;

[0015] Based on the shaft current under each operating condition, the total energy and common-mode interference voltage in the specified frequency band are calculated.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] This application provides a hub motor shaft current electromagnetic compatibility test method, which can effectively evaluate the shaft current characteristics of the hub motor under different operating conditions and its impact on the electromagnetic compatibility (EMC) performance, thereby improving the electromagnetic compatibility and reliability of the hub motor and its control system. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the specific implementation methods of the present application or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the specific implementation methods or the description of the prior art. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0019] Figure 1 Schematic diagram of the structure of the electromagnetic compatibility test device for the hub motor shaft current provided in an embodiment of the present application;

[0020] Figure 2 1 is a flow chart of an electromagnetic compatibility test method for a hub motor shaft current provided in an embodiment of the present application;

[0021] Among them, 1—shielded 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 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—hub motor; 25—hub motor tooling; 26—hub motor tooling output shaft; 27—dynamometer connecting bearing; 28—dynamometer; 29—load; 30—hub motor controller; 3—low relative dielectric constant material support; 4—current probe; 5—LV wiring harness; 6—HV wiring harness; 7—photoelectric conversion equipment; 8—impedance matching network; 9—LV AN; 10—HV AN. DETAILED DESCRIPTION

[0022] The following description of exemplary embodiments of the present application is made in conjunction with the accompanying drawings, including various details of the embodiments of the present application to facilitate understanding. These details should be considered as merely exemplary. Therefore, those skilled in the art will recognize that various changes and modifications may be made to the embodiments described herein without departing from the scope and spirit of the present application. Similarly, for the sake of clarity and conciseness, descriptions of well-known functions and structures are omitted in the following description.

[0023] The present invention provides an electromagnetic compatibility test device for the shaft current of a hub motor. Figure 1 , at least including the shielding room 1, the system master control 19, the dynamometer 28, the hub motor tooling 25 and the test system. The following details the location, connection relationship and function of each component.

[0024] Shielded room 1 is typically constructed from welded metal sheets, forming an enclosed space that isolates the tester from external electromagnetic interference. The walls, ceiling, and floor are covered with high-performance electromagnetic wave absorbing material, effectively absorbing reflected waves, reducing multipath effects, and ensuring a pure test environment. Shielded room 1 houses a dynamometer 28, in-wheel motor fixture 25, and a test system.

[0025] The dynamometer 28 (also called a dynamometer) is a key instrument for analyzing the performance of the hub motor 24. Its core function is to analyze the dynamic performance of the hub motor 24 by measuring parameters such as torque and speed. In this embodiment, the rotor end of the hub motor 24 is designed with an output shaft, which is connected to the dynamometer 28 to output the torque of the 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 operating conditions of 6000 rpm and 500 Nm. The dynamometer 28 is compatible with the hub motor 24 and outputs torque to simulate the operating state of the hub motor 24. The dynamometer 28 is connected to the hub motor tooling output shaft 26 via the dynamometer connecting bearing 27.

[0026] The hub motor fixture 25 is used to install and fix the hub motor 24 to be tested.

[0027] The test system is used to measure the shaft current of the in-wheel motor 24 and transmit the shaft current to the system master control 19. The system master control 19 is connected to the optical fiber 22 via the optical fiber feedthrough 17. The system master control 19 is used to control the in-wheel motor 24 under various operating conditions, collect the shaft current under each operating condition, and obtain electromagnetic compatibility test results based on the shaft current. The operating conditions of the in-wheel motor 24 include various speeds, torques, and loads.

[0028] Optionally, the system master control 19 includes: a motor drive controller, a load control unit and a data acquisition and processing system.

[0029] The motor drive controller is used to provide a simulated road load for the hub motor 24 under test, enabling the hub motor 24 to operate at different speeds and torques. The load control unit is used to control the load 29 (for power recovery operation) to match the output of the power distribution unit of the hub motor 24, and is suitable for hub motors 24 with power recovery functions. The load 29 is, for example, 50Ω. The data acquisition and processing system is used to collect the shaft current of the hub motor 24 under different operating conditions and obtain electromagnetic compatibility test results based on the shaft current. The load 29, HV AN 10, and impedance matching network 8 are placed in the additional shielding box 14.

[0030] Optionally, the electromagnetic compatibility test apparatus for in-wheel motor shaft current provided in this embodiment also includes an HV power supply 15, an LV power supply 13, and multiple filters, such as a power line filter 16. 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 via the LV power line 11. The LV AN 9 is a low voltage artificial power network.

[0031] Multiple filters are used to filter the HV power line 12 of the HV power supply 15, which is double-shielded. The HV power supply 15 and LV power supply 13 are used to power the hub motor 24, simulating various voltage, current, and frequency operating conditions to ensure that the power supply environment of the hub motor 24 under various operating conditions during testing matches actual usage, thereby ensuring the authenticity and reliability of the test results. The HV power supply 15 and LV power supply 13 can be configured according to actual conditions to simulate various voltage, current, frequency, and other different operating conditions to meet various testing requirements. Through the use of this power supply, the electromagnetic compatibility performance of the hub motor 24 under different operating conditions can be accurately evaluated, providing strong support for the development and commissioning of the hub motor 24.

[0032] 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 shielded room 1, and the current (measured by the current probe 4) is transmitted to the receiver 18 outside the shielded room 1 through the high-quality coaxial cable 21. The receiver 18 then analyzes 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 hub motor tooling, and the center of the current probe 4 coincides with the axis center of the output shaft of the hub motor 24 and does not contact, so as to accurately measure the shaft current. The receiver 18 is connected to the high-quality coaxial cable 21 through the wall panel connector 20.

[0033] Optionally, the apparatus also includes a test table. The table contains the in-wheel motor 24 (fixed to the in-wheel motor fixture 25), the HV wiring harness 6 (including HV+ and HV-), the LV wiring harness 5, the HV AN 10, the LV AN 9, the optoelectronic conversion device 7, and the LV power supply 13. The HV AN 10 is a high-voltage artificial power network (HVAN).

[0034] Control commands from system master control 19 are transmitted to shielded room 1 in the form of optical signals. Optoelectronic conversion device 7 within shielded room 1 converts the optical signals into electrical signals, which then control in-wheel motor controller 30 to operate in-wheel motor 24 at various speeds and torques. Similarly, after the control commands from system master control 19 pass through optoelectronic conversion device 7, they can also be used to control load 29 to match the output of the power distribution unit of in-wheel motor 24.

[0035] 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 control 19. For example, the system master control 19 sends shaft current and electromagnetic compatibility test results to the cloud server, and the cloud server sends control instructions to the system master control 19. Remote monitoring and control strategy adjustment can be achieved through cloud-based interaction.

[0036] The grounding strap 23 is used to connect to the ground to ensure electrical safety.

[0037] Figure 2 This is a flow chart of an electromagnetic compatibility test method for a hub motor shaft current provided in an embodiment of the present application, using the electromagnetic compatibility test device for a hub motor shaft current provided in the aforementioned embodiment. Figure 2 The methods shown include:

[0038] S110. Arrange the test environment for the electromagnetic compatibility test device based on the hub motor shaft current.

[0039] S120. In the test environment, control the hub motor under test to operate under multiple operating conditions, and collect the shaft current under each operating condition.

[0040] First, the hub motor 24 to be tested is placed on the test table and then mounted on the hub motor fixture 25 for installation and fixation. The hub motor 24 rotor end is designed with an output shaft, which is connected to the hub motor fixture output shaft 26. The hub motor fixture output shaft 26 is connected to the output shaft of the dynamometer 28. 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., a 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.

[0041] The length of the LV harness 5 should be 1700 ± 300 mm, and the length of the HV harness 6 should be 1700 ± 300 mm. The length parallel to the edge of the reference ground plane 2 should be 1500 mm ± 75 mm. The length of the three-phase cable between the hub motor 24 and the hub motor controller 30 should be less than 1000 mm. The hub motor 24 should be placed on the dynamometer 28 stand, and all harnesses should be placed on a non-conductive, low-relative-permittivity material support 3, 50 mm ± 5 mm above the reference ground plane 2. The LV harness 5 should be placed at least 200 mm from the edge of the reference ground plane 2, and the spacing between the LV harness 5 and the HV harness 6 should be 100 ± 10 mm. The housings of the hub motor 24 and hub motor controller 30 should be connected to the reference ground plane 2 directly or via a specified impedance.

[0042] The system master control 19 applies working load to the in-wheel motor 24 under test, providing simulated road loads to the in-wheel motor 24, causing it to operate at different speeds and torques. The in-wheel motor 24 outputs speed via the in-wheel motor tooling output shaft 26 and torque via the dynamometer 28.

[0043] Next, conduct the shaft current electromagnetic compatibility test. Use a non-metallic, low relative dielectric constant (εr ≤ 1.4) fixture to secure the current probe 4 to one side of the hub motor fixture's output shaft 26. There should be no direct contact between the current probe 4 and the hub motor fixture's output shaft 26, and the center of the current probe 4 should coincide with the center of the hub motor 24's output shaft. For example, measure the shaft current using the current probe 4 at a distance d (recommended d value of 50 mm ± 5 mm) from the hub motor 24's output shaft.

[0044] S130. Calculate the total energy and common-mode interference voltage within a specified frequency band based on the shaft current under each operating condition.

[0045] Optionally, perform a fast Fourier transform on the shaft current i(t) in the time domain to obtain the spectrum characteristics .

[0046] ;

[0047] Where i(t) is the shaft current in the time domain, j is the imaginary unit, is the frequency term. Indicates the current at frequency The amplitude distribution under the condition is calculated, where F represents the fast Fourier transform algorithm. The spectrum is analyzed for high-amplitude harmonics, switching frequency components, or their multiples. This step is implemented in the software built into the system master control 19.

[0048] According to the spectrum characteristics The spectral power density is obtained and integrated within the specified frequency band to obtain the total energy within the specified frequency band. Specifically, the shaft current spectral power density (PSD) is defined as a reference indicator for electromagnetic interference (EMI) risk:

[0049] ;

[0050] Among them, PSD() is the calculation formula of spectral power density.

[0051] Calculate the total energy within a certain frequency band as an EMI evaluation parameter ,For example:

[0052] ;

[0053] Among them, 150kHz~30MHz is the disturbance frequency range in typical EMC standards.

[0054] According to the equivalent impedance of the path from the hub motor bearing to the ground and the spectrum characteristics, the common mode interference voltage is obtained. :

[0055] ;

[0056] in, is the equivalent impedance of the path from the hub motor bearing to the ground, is the common-mode voltage distribution that may cause EMI.

[0057] Optionally, after calculating the total energy and common-mode interference voltage in a specified frequency band based on the shaft current under each operating condition, the method further includes: pre-testing the electromagnetic compatibility of the hub motor using a conducted emission current method to obtain the frequency of the conducted interference; calculating the correlation between the frequency of the conducted interference and the spectrum peak in the spectrum characteristics; if the correlation is greater than a set threshold, determining that the shaft current has an impact on the electromagnetic compatibility performance of the hub motor.

[0058] For example, conducted EMI testing includes both conducted emission current and voltage methods, requiring a test platform built using a linear impedance stabilization network (LISN) and current probes. Following CISPR 25 or CISPR-22 standards, testing is performed using voltage methods (such as peak limit detection) and transient pulse methods. Conducted emissions are measured using current probes to determine the frequency of conducted interference.

[0059] Will Compare the spectrum peak in the signal with the frequency point of EMI conducted interference, analyze the correlation between the two in frequency and amplitude, and further calculate the correlation coefficient:

[0060] ;

[0061] Where ρ is the correlation coefficient, Indicates the frequency in EMI test f The interference current value, Indicates the current at frequency The amplitude distribution under , cov() is the covariance, for The variance of for The variance of . The larger the correlation coefficient, the greater the impact of the shaft current on the electromagnetic compatibility performance of the hub motor. For example, when the correlation coefficient approaches 1, it means that the shaft current has a significant impact on EMC.

[0062] This application provides an electromagnetic compatibility test method for the shaft current of a hub motor, which can effectively evaluate the shaft current characteristics of the hub motor under different operating conditions and its impact on electromagnetic compatibility (EMC) performance, thereby improving the electromagnetic compatibility and reliability of the hub motor and its control system. Through current probes and spectrum analysis, real-time monitoring and spectrum analysis of the hub motor shaft current are achieved, effectively capturing the shaft current characteristics under different operating conditions, improving measurement accuracy and data reliability. The use of an electromagnetic compatibility shielded room and standardized test layout effectively shields external electromagnetic interference, improves the repeatability and consistency of test results, and provides a reliable basis for the EMC design and improvement of hub motors. 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 electrocorrosion and improving the motor's service life and reliability.

[0063] This application was tested within a shielded room to reduce external electromagnetic interference and ensure the accuracy of the measurement data. Furthermore, an optimized grounding method and shielding structure were used to minimize the impact of parasitic capacitance on the test results. High-frequency current probes, slip rings / shunt resistors, oscilloscopes, and spectrum analyzers were used to accurately monitor the magnitude, spectral characteristics, and propagation path of the shaft current. The impact of these on the test results of electromagnetic conduction and emission shaft current was analyzed in combination with different operating conditions.

[0064] After analyzing the test data, it can be used to optimize the in-wheel motor's shielding structure, grounding method, and control strategy. For example, adjustments to the inverter's pulse width modulation (PWM) method can be made to reduce high-frequency common-mode voltage and thus mitigate shaft current generation at its source. Furthermore, the adverse effects of shaft current on motor life can be reduced by optimizing bearing insulation design.

[0065] This application is applicable to EMC testing of hub motors, electric drive systems and new energy vehicles, providing technical support for electromagnetic compatibility optimization, control strategy improvement and certification of related products, and improving the electromagnetic compatibility performance and long-term stability of the system.

[0066] It should be understood that the various forms of the processes shown above can be used to reorder, add, or delete steps. For example, the steps described in this application can be performed 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. This is not a limitation herein.

[0067] The above specific embodiments do not constitute a limitation on the scope of protection of this application. Those skilled in the art will appreciate that various modifications, combinations, sub-combinations, and substitutions may be made based on 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 scope of protection of this application.

Claims

1. An electromagnetic compatibility test method for hub motor shaft current, characterized in that: The electromagnetic compatibility test device for hub motor shaft current includes: shielded room, system master control, dynamometer, hub motor tooling and test system; The shielded room is equipped with a dynamometer, a hub motor tooling and a test system; The hub motor fixture is used to install and fix the hub motor to be tested; The rotor end of the hub motor is designed with an output shaft, which is connected to the dynamometer via the output shaft; The test system is used to measure the shaft current of the hub motor; The system master control is used to control the hub motor to operate under multiple working conditions and collect shaft current under each working condition; and obtain electromagnetic compatibility test results based on the shaft current; The method comprises: Arrange the test environment based on the electromagnetic compatibility test device of the hub motor shaft current; In the test environment, the hub motor under test is controlled to operate under multiple operating conditions, and the shaft current under each operating condition is collected; wherein the multiple operating conditions include multiple speeds, multiple torques, and multiple loads of the hub motor; Calculate the total energy and common mode interference voltage in the specified frequency band based on the shaft current under each working condition; Conducting electromagnetic compatibility testing on the hub motor using a conducted emission current method in advance to obtain the frequency of conducted interference; Calculating the correlation between the frequency point of the conducted interference and the spectrum peak in the spectrum characteristic; wherein the spectrum characteristic is obtained by performing a fast Fourier transform on the shaft current in the time domain; If the correlation is greater than a set threshold, it is determined that the shaft current has an impact on the electromagnetic compatibility performance of the wheel hub motor.

2. The method according to claim 1, characterized in that Based on the shaft current under each operating condition, calculate the total energy and common mode interference voltage in the specified frequency band, including: Perform fast Fourier transform on the shaft current in the time domain to obtain the spectrum characteristics; Obtaining spectrum power density according to the spectrum characteristics; Integrating the spectral power density within a specified frequency band to obtain a total energy within the specified frequency band; The common-mode interference voltage is obtained according to the equivalent impedance of the path from the hub motor bearing to the ground and the spectrum characteristics.

3. The method according to claim 1, characterized in that The electromagnetic compatibility test device for the hub motor shaft current also includes: a high-voltage power supply, a low-voltage power supply and multiple sets of filters; The multiple groups of filters are used to filter the high-voltage power lines of the high-voltage power supply; The high-voltage power supply and the low-voltage power supply are used to supply power to the hub motor, simulating various voltage, current and frequency operating conditions.

4. The method according to claim 1, wherein The test system includes: a current probe and a receiver; Connecting the current probe via a radio frequency cable interface in the shielded room, and transmitting the current to a receiver outside the shielded room via the radio frequency cable; The current probe is fixed to the output shaft of the hub motor fixture, and the center of the current probe coincides with the axis center of the output shaft of the hub motor and does not contact with each other.

5. The method according to claim 1, wherein The electromagnetic compatibility test device for the hub motor shaft current also includes a test table; The hub motor to be tested, a high-voltage wiring harness, a low-voltage wiring harness, a high-voltage artificial power network, a low-voltage artificial power network, a photoelectric conversion device and a low-voltage power supply are placed on the test table.

6. The method according to claim 5, characterized in that The system master control includes: A motor drive controller, used to provide simulated road load to the wheel hub motor under test; A load control unit, configured to match the output of the power distribution unit of the hub motor; The data acquisition and processing system is used to collect the shaft current of the hub motor under different working conditions and obtain the electromagnetic compatibility test result according to the shaft current.

7. The method according to claim 6, characterized in that The electromagnetic compatibility test device for the hub motor shaft current 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.

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