Shaft current test structure and method for double-shaft EMC (Electro Magnetic Compatibility) on-load test system

Abstract

The invention discloses a shaft current test structure and method for a double-shaft EMC (Electro Magnetic Compatibility) on-load test system, the method depends on a structure obtained by improving the double-shaft EMC on-load test system, a current probe is used for testing shaft current in a non-invasive manner, and the interference on the normal operation of the system is small; the problems that an existing shaft current testing method only focuses on shaft current testing of a motor, comprehensiveness and reliability are poor, and the requirement for shaft current testing of a double-shaft EMC on-load testing system is difficult to well meet are effectively solved. The influence of the magnitude of the shaft current on the EMC on-load test of the electric drive assembly is explored, and the correlation degree and the action mechanism between the shaft current and the electromagnetic compatibility are deeply analyzed and evaluated; in addition, shaft current testing can be carried out in no-load and loaded states, and background noise can be detected. A more comprehensive and accurate solution can be provided for the EMC loading test of the new energy automobile electric drive assembly, and the progress of the test technology in the related field can be promoted.

Description

Technical Field

[0001] The invention belongs to the technical field of measuring electrical variables in physics, and in particular relates to an axis current test structure and method for a dual-axis EMC load test system. Background Art

[0002] The electric drive assembly is one of the most important assembly structures in new energy vehicles. The electric drive assembly includes a motor and related drive components. When the electric drive assembly is working, it will generate electromagnetic interference to nearby electronic components, which can easily affect their normal operation. In order to ensure the safety and reliability of vehicle driving, the electric drive assembly needs to be subjected to electromagnetic compatibility testing during the research and development process. Unlike a single motor that is tested using a single-axis EMC load test system, in order to restore its actual working conditions, the electric drive assembly needs to rely on a dual-axis EMC load test system for testing. Its physical structure is a dual-axis through-wall load test bench (such as the test bench disclosed in Chinese patent CN118707155A), including a gear box and a receiving antenna arranged in an anechoic chamber (ALSE room). The input shaft of the gear box is used to connect to the electric drive assembly and to connect to a dynamometer outside the anechoic chamber through the electric drive assembly and the through-wall shaft. The output end of the gear box is connected to another dynamometer outside the anechoic chamber through another through-wall shaft. An EMI receiver is provided in the shielded room outside the anechoic chamber. The input end of the EMI receiver is electrically connected to the receiving antenna through a signal cable, thereby receiving and processing the electromagnetic interference generated by the electric drive assembly.

[0003] When conducting electromagnetic compatibility testing on the electric drive assembly, its motor is prone to generate shaft voltage due to magnetic imbalance and static charge. When the shaft voltage is higher than the oil film breakdown voltage threshold, shaft current will be generated in the closed loop formed by the various shaft system components. The presence of shaft current will seriously affect the accuracy of the test results, causing a large difference between the test results and the test results of the whole vehicle, and cannot reflect the electromagnetic radiation status of the electric drive assembly in the actual working environment. Therefore, in order to explore the influence of shaft current on the test, deeply analyze and evaluate the correlation and mechanism between shaft current and electromagnetic compatibility, when conducting electromagnetic compatibility test on electric drive assembly, it is necessary to test the shaft current in the dual-axis EMC load test system; the commonly used shaft current test methods are mainly lead method, radio frequency method and additional bearing method, but whether it is the lead method that adds an insulating layer to the outer raceway and bearing chamber of the bearing and leads out the wire to measure the current, or the radio frequency method uses a receiving antenna with a specific bandwidth and undergoes a series of signal processing to quantify the frequency of shaft current, or the additional bearing method sets bearings with different functions inside and outside the motor and uses brushes to guide the current to achieve shaft current measurement, all of them are centered around the motor. When conducting electromagnetic compatibility test on electric drive assembly, in addition to the motor generating shaft current, the dynamometer as the load device of the motor is also prone to generate shaft current during operation, and will enter the anechoic chamber with the shaft transmission parts and merge with the shaft current generated by the motor, which will not only affect the accuracy of the test results, but may even cause the background noise of the anechoic chamber to fail to meet the test standards. However, the commonly used shaft current test method is difficult to be directly used for the shaft current test of the dual-axis EMC load test system itself. Therefore, it is necessary to design a new shaft current test method to fill the current gap in the shaft current test of the dual-axis EMC load test system itself and improve the comprehensiveness of the shaft current test. Summary of the invention

[0004] In view of the above-mentioned deficiencies in the prior art, the purpose of the present invention is to provide a shaft current testing structure and method for a dual-axis EMC on-load test system, so as to solve the technical problem that the existing shaft current testing method is difficult to directly use for shaft current testing of a dual-axis EMC on-load test system, and to achieve the effect of improving the comprehensiveness and reliability of shaft current testing.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions: The invention discloses a shaft current test structure for a dual-axis EMC load test system, comprising a gearbox arranged in an anechoic chamber, wherein the gearbox is a shift gearbox, wherein an output shaft of the gearbox is connected to one end of a first through-wall shaft arranged horizontally, the other end of the first through-wall shaft extends out of the anechoic chamber and is transmission-connected to a first dynamometer, an input shaft of the gearbox is transmission-connected to one end of a horizontally arranged test shaft, the other end of the test shaft is transmission-connected to one end of a second through-wall shaft arranged horizontally, the other end of the second through-wall shaft extends out of the anechoic chamber and is transmission-connected to a second dynamometer; the test shaft is grounded and has a smooth and conductive outer cylindrical surface; an annular current probe is rotatably sleeved on the test shaft, a probe fixture for fixing the current probe is arranged below the current probe, a processing unit is arranged in a shielding chamber outside the anechoic chamber, and the processing unit is electrically connected to the current probe for obtaining shaft current data.

[0006] Furthermore, the processing unit includes an EMI receiver and a computer. The EMI receiver is electrically connected to the current probe and the computer respectively. An attenuator is also electrically connected between the EMI receiver and the current probe.

[0007] Furthermore, the first through-wall shaft is transmission connected to the input shaft of the first dynamometer through a first coupling, the first through-wall shaft is transmission connected to the output shaft of the gear box through a second coupling, the test shaft is transmission connected to the input shaft of the gear box through a third coupling, the test shaft is transmission connected to the second through-wall shaft through a fourth coupling, and the second through-wall shaft is transmission connected to the input shaft of the second dynamometer through a fifth coupling.

[0008] Furthermore, a first bearing seat and a second bearing seat for support are respectively provided on the first through-wall shaft near the first coupling and the second coupling, a third bearing seat and a fifth bearing seat are respectively provided on the test shaft near the third coupling and the fourth coupling, and a sixth bearing seat and a seventh bearing seat are respectively provided in the middle part of the second through-wall shaft and near the fifth bearing seat.

[0009] Furthermore, a fourth bearing seat for support is provided in the middle of the test shaft, and an annular carbon brush is provided on the fourth bearing seat. The annular carbon brush is rotatably sleeved on the test shaft and grounded, and the inner side surface of the annular carbon brush contacts the outer cylindrical surface of the test shaft to ground the test shaft.

[0010] Furthermore, the probe clamp includes a clamping plate, a first connecting plate, a second connecting plate, a third connecting plate and a clamp base which are sequentially connected from top to bottom, the upper end of the clamping plate has a clamping portion for clamping and fixing the current probe, the first connecting plate and the second connecting plate are rotatably connected via a transversely arranged first rotating shaft, and the second connecting plate and the third connecting plate are rotatably connected via a transversely arranged second rotating shaft.

[0011] Furthermore, the clamping portion is semicircular in shape with the concave surface facing upward, the current probe is located on the inner side of the clamping portion, and clamping bolts are transversely penetrated and threadedly connected at both ends of the semicircular arc on the clamping portion, and the head of the clamping bolt is located on the outer side of the clamping portion so that the current probe can be clamped and fixed by tightening the clamping bolt.

[0012] Furthermore, the opposite ends of the first connecting plate and the second connecting plate have connecting ears that are alternately distributed laterally, the first rotating shaft is a bolt and rotates through the connecting holes on each connecting ear, the head of the bolt abuts against the connecting ear on one lateral side, and the tail is threadedly connected to the connecting ear on the other lateral side, so that the relative rotation of the first connecting plate and the second connecting plate can be limited by tightening the bolt.

[0013] Furthermore, the first connecting plate and the clamping plate are connected by a double ball joint universal joint, which includes a locking bolt and two limit plates arranged in parallel and at intervals. An arc-shaped limit portion is connected to the inner side of the limit plate near the end, and the concave surfaces of the two limit portions at the same end are opposite to each other and form a ball bowl. A matching ball head is rotatably provided in the ball bowl, and a connecting rod is formed on the ball head. The connecting rod extends from between the two limit portions, and the two ends of the double ball joint universal joint are respectively connected to the first connecting plate and the clamping plate through the connecting rod; the locking bolt vertically passes through the two limit plates, the head of the locking bolt abuts against one limit plate, and the tail is threadedly connected to the other limit plate, so as to limit the rotation of the ball head in the ball bowl by tightening the locking bolt; the third connecting plate and the fixture base are also connected by a double ball joint universal joint.

[0014] The present invention also includes an axis current test method for a dual-axis EMC load test system, wherein the axis current test method is performed using the axis current test structure as described above, including a no-load test and a loaded test; No-load test: connect the test shaft only to the input shaft of the gearbox, adjust the gearbox gear position to make the speed ratio 1:1, and test the shaft current generated by the first dynamometer and entering the anechoic chamber through the current probe; connect the test shaft only to the second through-wall shaft, and test the shaft current generated by the second dynamometer and entering the anechoic chamber through the current probe; Loading test: connect the test shaft to the input shaft of the gearbox and the second through-wall shaft respectively, adjust the gearbox gear position and control the speed of the first dynamometer and the second dynamometer to form a pair of dynamometers, and test the shaft current generated by the first dynamometer and the second dynamometer and entering the anechoic chamber through the current probe.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. The shaft current testing method of the present invention is simple and convenient to operate, has high testing efficiency, does not require major changes to the existing dual-axis EMC on-load test system, has a wide testing range, and uses a current probe to test the shaft current, which is a non-invasive measurement and is beneficial to reducing interference with the normal operation of the system; the current probe used has the characteristics of high bandwidth and high precision, can accurately and quickly capture the changes in the shaft current, can meet the needs of high-frequency testing of the shaft current, and effectively reflect the dynamic change process of the shaft current; compared with the existing shaft current testing method, the present invention successfully fills the gap in the verification method of the influence of the shaft current of the dual-axis EMC on-load test system itself on the electromagnetic compatibility test results of the electric drive assembly.

[0016] 2. The shaft current testing method described in the present invention can effectively solve the problem that the current shaft current testing method only focuses on the shaft current testing of the motor itself, has poor comprehensiveness and reliability, and is difficult to meet the shaft current testing requirements of the dual-axis EMC load test system. It is beneficial to explore the influence of the shaft current on the EMC load test of the electric drive assembly, and to deeply analyze and evaluate the correlation and action mechanism between the shaft current and electromagnetic compatibility.

[0017] 3. The shaft current test method described in the present invention is based on the shaft current test structure obtained by improving the dual-axis EMC loading test system. When the dynamometers on both sides are used as electromagnetic compatibility "noise sources" and carbon fiber through-wall shafts and insulating couplings are used for insulation treatment, the shaft current on the surface of the shaft system transmission parts connected to the "noise source" in the anechoic chamber is detected. This solves the problem of difficulty in detecting electromagnetic interference in the propagation path when the test equipment is processing the noise source. The test range of the current probe is greatly improved, and the measurement accuracy is high.

[0018] 4. The shaft current test structure of the present invention can not only perform shaft current tests in the no-load and loaded states of the dual-axis EMC loading test system, but also detect whether the anechoic chamber meets the background noise requirements; secondly, a smooth test shaft without insulating coating is used to connect the dynamometers on both sides, providing a complete closed loop for the shaft current, truly simulating the shaft current existing in the power transmission path of the dual-axis EMC loading test system under actual load conditions, and verifying whether the background noise of the anechoic chamber meets the international standard limit under this condition; the method using the shaft current test structure effectively fills the gap in the current shaft current test method of the dual-axis EMC loading test system, and provides a more comprehensive and accurate solution for the EMC loading test of the electric drive assembly of new energy vehicles, which is conducive to promoting the progress of testing technology in related fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a schematic top view of the shaft current test structure described in the embodiment; Figure 2is a front view schematic diagram of the probe fixture structure described in the embodiment; Figure 3 It is a flowchart of the steps of the shaft current testing method described in the embodiment; Figure 4 A flowchart of the background noise detection method described in the embodiment; Among them, the first dynamometer 1, the first coupling 2, the first bearing seat 3, the first through-wall shaft 4, the second bearing seat 5, the second coupling 6, the gear box 7, the third coupling 8, the third bearing seat 9, the test shaft 10, the fourth bearing seat 11, the probe fixture 12, the current probe 13, the fifth bearing seat 14, the fourth coupling 15, the sixth bearing seat 16, the second through-wall shaft 17, the seventh bearing seat 18, the fifth coupling 19, the second dynamometer 20, the anechoic chamber 21, the shielding room 22, the computer 23, the EMI receiver 24, the attenuator 25, the signal cable 26, the clamping bolt 27, the clamping part 28, the clamping plate 29, the ball head 30, the limit plate 31, the locking bolt 32, the first connecting plate 33, the first rotating shaft 34, the second connecting plate 35, the second rotating shaft 36, the third connecting plate 37, the fixture base 38, the limit part 39, and the connecting rod 40. DETAILED DESCRIPTION

[0020] To make the purpose, technical solution and advantages of the embodiments of the present invention more clear, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0021] Example: See also Figure 1 The invention discloses a shaft current test structure for a dual-axis EMC load test system, comprising a gearbox 7 arranged in an anechoic chamber 21, wherein the gearbox 7 is a shift gearbox 7, wherein an output shaft of the gearbox 7 is connected to one end of a horizontally arranged first through-wall shaft 4, wherein the other end of the first through-wall shaft 4 extends out of the anechoic chamber 21 and is connected to a first dynamometer 1 by transmission, and an input shaft of the gearbox 7 is connected to one end of a horizontally arranged test shaft 10 by transmission, wherein the other end of the test shaft 10 is connected to one end of a horizontally arranged second through-wall shaft 17 by transmission, wherein the other end of the second through-wall shaft 17 extends out of the anechoic chamber 21 and is connected to a second dynamometer 20 by transmission; the test shaft 10 is grounded and has a smooth and conductive outer cylindrical surface; an annular current probe 13 is rotatably sleeved on the test shaft 10, and a probe fixture 12 for fixing the current probe 13 is provided below the current probe 13; a processing unit is provided in a shielding chamber 22 outside the anechoic chamber 21, and the processing unit is electrically connected to the current probe 13 for obtaining shaft current data.

[0022] See also Figure 1The processing unit includes an EMI receiver 24 and a computer 23. The EMI receiver 24 is electrically connected to the current probe 13 and the computer 23 respectively. An attenuator 25 is also electrically connected between the EMI receiver 24 and the current probe 13. In this embodiment, the attenuator 25 is connected to the current probe 13 through a signal cable 26. A voltage probe with a carbon brush is used. The carbon brush has excellent conductivity and outstanding wear resistance. Its soft characteristics enable it to form good electrical contact with the measured shaft under a certain pressure, which effectively ensures that the voltage signal can be smoothly transmitted from the measured shaft to the voltage probe. During the test, the carbon brush should be in close contact with the measured shaft.

[0023] See also Figure 1 Specifically, the first through-wall shaft 4 is transmission-connected to the input shaft of the first dynamometer 1 through the first coupling 2, the first through-wall shaft 4 is transmission-connected to the output shaft of the gear box 7 through the second coupling 6, the test shaft 10 is transmission-connected to the input shaft of the gear box 7 through the third coupling 8, the test shaft 10 is transmission-connected to the second through-wall shaft 17 through the fourth coupling 15, and the second through-wall shaft 17 is transmission-connected to the input shaft of the second dynamometer 20 through the fifth coupling 19; in this embodiment, the first coupling 2 and the fifth coupling 19 are insulating couplings; in this way, it is beneficial to reduce the shaft current generated by the dynamometer and entering the anechoic chamber 21, thereby reducing the impact of the dynamometer on the test environment in the anechoic chamber 21, and is beneficial to use the dual-axis EMC load test system to perform electromagnetic compatibility testing on the electric drive system.

[0024] See also Figure 1 The first through-wall shaft 4 is provided with a first bearing seat 3 and a second bearing seat 5 for support, respectively, near the first coupling 2 and the second coupling 6; the test shaft 10 is provided with a third bearing seat 9 and a fifth bearing seat 14, respectively, near the third coupling 8 and the fourth coupling 15; the middle part of the second through-wall shaft 17 and near the fifth bearing seat 14 are provided with a sixth bearing seat 16 and a seventh bearing seat 18, respectively; in this way, the first through-wall shaft 4, the test shaft 10 and the second through-wall shaft 17 are supported by two bearing seats, respectively, which is beneficial to improving the rotation stability of each shaft system transmission component and the stability of the shaft current test structure.

[0025] See also Figure 1A fourth bearing seat 11 for support is provided in the middle of the test shaft 10, and an annular carbon brush is provided on the fourth bearing seat 11. The annular carbon brush is rotatably sleeved on the test shaft 10 and grounded, and the inner side surface of the annular carbon brush contacts the outer cylindrical surface of the test shaft 10 to ground the test shaft 10; in this way, the fourth bearing seat 11 is provided in the middle of the test shaft 10, which further improves the rotation stability of the test shaft 10, and the annular carbon brush is fixed with the help of the fourth bearing seat 11 and rotatably sleeved on the test shaft 10, and the inner diameter of the annular carbon brush matches the diameter of the test shaft 10 to ensure that the inner side surface of the annular carbon brush maintains good contact with the outer cylindrical surface of the test shaft 10, and the test shaft 10 is grounded through the annular carbon brush, so that the shaft transmission components of the shaft current test structure form a loop to facilitate the test shaft 10 current.

[0026] See also Figure 2 The probe fixture 12 includes a clamping plate 29, a first connecting plate 33, a second connecting plate 35, a third connecting plate 37 and a fixture base 38 connected in sequence from top to bottom. The upper end of the clamping plate 29 has a clamping portion 28 for clamping and fixing the current probe 13. The first connecting plate 33 and the second connecting plate 35 are rotatably connected by a transversely arranged first rotating shaft 34, and the second connecting plate 35 and the third connecting plate 37 are rotatably connected by a transversely arranged second rotating shaft 36; in this way, the probe fixture 12 can be folded, unfolded and folded for easy use and storage; in this embodiment, the base of the fourth bearing seat 11 is used as the fixture base 38.

[0027] See also Figure 2 The clamping portion 28 is semicircular in shape with the concave surface facing upwards, the current probe 13 is located on the inner side of the clamping portion 28, and clamping bolts 27 are transversely penetrated at both ends of the semicircular on the clamping portion 28 and threadedly connected, and the head of the clamping bolt 27 is located on the outer side of the clamping portion 28; in this way, after the current probe 13 is placed inside the clamping portion 28, the current probe 13 can be clamped and fixed by tightening the clamping bolt 27, so that the clamping portion 28 can clamp and fix current probes 13 of various sizes, which is conducive to improving practicality and flexibility of use.

[0028] See also Figure 2 The opposite ends of the first connecting plate 33 and the second connecting plate 35 have connecting ears that are alternately distributed laterally. The first rotating shaft 34 is a bolt and rotates through the connecting holes on each connecting ear. The head of the bolt abuts against the connecting ear on one lateral side, and the tail is threadedly connected to the connecting ear on the other lateral side. In this way, the relative rotation of the first connecting plate 33 and the second connecting plate 35 can be limited by tightening the bolt, thereby locking the height of the probe clamp 12, which is beneficial to improving the applicability and practicality of the probe clamp 12.

[0029] See also Figure 2The first connecting plate 33 is connected to the clamping plate 29 through a double ball joint universal joint, which includes a locking bolt 32 and two parallel and spaced limiting plates 31. The inner side of the limiting plate 31 is connected to a circular arc-shaped limiting portion 39 near the end. The concave surfaces of the two limiting portions 39 at the same end are opposite to each other and form a ball bowl. A matching ball head 30 is rotatably arranged in the ball bowl. A connecting rod 40 is formed on the ball head 30. The connecting rod 40 extends from between the two limiting portions 39. The two ends of the double ball joint universal joint are respectively connected to the first connecting plate 33 and the clamping plate 29 through the connecting rod 40; the locking bolt 32 vertically penetrates the two limiting plates 31, and the locking bolt The head of 32 is in contact with a limit plate 31, and the tail is threadedly connected to another limit plate 31, so that the ball head 30 can be limited to rotate in the ball bowl by tightening the locking bolt 32; the third connecting plate 37 is also connected to the fixture base 38 by a double ball joint universal joint; in this way, after loosening the locking bolt 32, the ball head 30 can rotate in the ball bowl, and not only can the distance between the connecting parts at both ends be adjusted by the double ball joint universal joint, but also the connecting parts at both ends can be relatively rotated. After adjusting to the right position, tighten the locking bolt 32 to complete the posture fixation, making the use of the probe fixture 12 more flexible, which is conducive to reducing the difficulty of use and meeting different test requirements.

[0030] The probe fixture 12 used in the shaft current test structure described in the present invention is cast as one body with the fourth bearing seat 11 and adopts a foldable design. When the electromagnetic compatibility test of the electric drive assembly is performed, it can be folded to reduce the volume, which not only helps to reduce the impact on the operation of the dual-axis EMC load test system, but also has good space utilization. The probe fixture 12 can not only clamp current probes 13 of various sizes, but also can flexibly adjust the position and posture of the current probe 13, and has good flexibility in use.

[0031] The shaft current test structure for the dual-axis EMC load test system of the present invention is obtained by connecting the test shaft 10 with its upper components instead of the electric drive assembly to the dual-axis EMC load test system. The test shaft 10 with a smooth outer cylindrical surface and no insulating coating is connected between the input shaft of the gear box 7 and the relative through-wall shaft through a coupling. The test shaft 10 is grounded through an annular carbon brush to make the shaft current test structure form a complete loop. The shaft 10 current is tested on the test shaft 10 using a current probe 13 and the shaft current data is obtained through the EMI receiver 24 and the computer 23.

[0032] See also Figure 3 , based on the shaft current test structure, the method of testing the shaft current using the current probe includes a no-load test and a loaded test; No-load test: connect the test shaft only to the input shaft of the gearbox, adjust the gearbox gear to make the speed ratio 1:1, and test the shaft current generated by the first dynamometer and entering the anechoic chamber through the current probe; connect the test shaft only to the second through-wall shaft, and test the shaft current generated by the second dynamometer and entering the anechoic chamber through the current probe; the frequency of the shaft current conducted interference measured by the current probe should be consistent with that specified in CISPR25, that is, the test frequency range is 9kHz - 110MHz, and the current signal measured by the current probe is transmitted to the EMI receiver located in the shielded room via the signal cable and attenuator. After being processed by the EMI receiver, the shaft current conducted interference test data can be obtained on the computer.

[0033] Loading test: connect the test shaft to the input shaft of the gearbox and the second through-wall shaft respectively, adjust the gearbox gear position and control the speed of the first dynamometer and the second dynamometer to form a pair of dynamometers, and test the shaft current generated by the first dynamometer and the second dynamometer and entering the anechoic chamber through the current probe.

[0034] The shaft current testing method for the dual-axis EMC on-load test system of the present invention is simple and convenient to operate, has high testing efficiency, does not require major changes to the existing dual-axis EMC on-load test system, has a wide testing range, uses a current probe to test the shaft current, belongs to non-invasive measurement, and minimizes interference with the normal operation of the system; the adopted current probe has the characteristics of high bandwidth and high precision, can accurately and quickly capture the change of the shaft current, can meet the needs of high-frequency testing of the shaft current, and effectively reflect the dynamic change process of the shaft current; compared with the existing shaft current testing method, the present invention successfully fills the gap in the verification method of the influence of the shaft current of the dual-axis EMC on-load test system itself on the electromagnetic compatibility test result of the electric drive assembly; therefore, the shaft current testing method of the present invention can effectively solve the problem that the current shaft current testing method only focuses on the shaft current test of the motor itself, has poor comprehensiveness and reliability, and is difficult to better meet the shaft current testing needs of the dual-axis EMC on-load test system, and is conducive to exploring the influence of the shaft current size on the EMC on-load test of the electric drive assembly, and deeply analyzing and evaluating the correlation and action mechanism between the shaft current and electromagnetic compatibility.

[0035] The shaft current testing method described in the present invention is based on the shaft current testing structure obtained by improving the dual-axis EMC loading test system. When the dynamometers on both sides are used as electromagnetic compatibility "noise sources" and carbon fiber through-wall shafts and insulating couplings are used for insulation treatment, the shaft current on the surface of the shaft system transmission parts connected to the "noise source" in the anechoic chamber is detected. This solves the problem of difficulty in detecting electromagnetic interference in the propagation path when the test equipment is processing the noise source. The test range of the current probe is greatly improved, and the measurement accuracy is high.

[0036] See also Figure 4 When conducting shaft current test, the background noise test can also be carried out with the help of dual-axis EMC load test system. It is necessary to ensure that the dynamometers on both sides are in normal working condition and are not connected to the electric drive assembly. Use the monopole antenna, biconical antenna, log-periodic antenna and horn antenna installed in the anechoic chamber and connected to the attenuator for testing. Among them, the biconical antenna, log-periodic antenna and horn antenna need to adjust the polarization direction respectively to achieve horizontal polarization and vertical polarization tests, and the antenna should be kept at a distance of 1m from the location where the electric drive assembly is installed; use the monopole antenna to aim at the location where the electric drive assembly is installed in the frequency range of 150kHz to 30MHz for testing; use the biconical antenna to aim at the location where the electric drive assembly is installed in the frequency range of 30MHz to 200MHz for testing; use the log-periodic antenna to aim at the location where the electric drive assembly is installed in the frequency range of 200MHz to 1GHz for testing; and use the log-periodic antenna to aim at the location where the electric drive assembly is installed in the frequency range of 1GHz to 2.5GHz. Use a horn antenna to aim at the location where the electric drive assembly is installed to perform testing within the frequency range; the test results are transmitted to the EMI receiver through the signal cable and attenuator, and the noise floor test data can be viewed on the computer; if the noise floor data measured in the no-load state is lower than the standard limit, perform a noise floor test in the loaded state. If the noise floor data is higher than the standard limit, it is necessary to investigate the cause of the excessive noise floor and make corresponding adjustments.

[0037] The shaft current test structure for the dual-axis EMC loading test system of the present invention is of great significance. Firstly, the structure can perform shaft current test in the no-load state of the dual-axis EMC loading test system, and can detect whether the anechoic chamber meets the background noise requirements; secondly, a smooth test shaft without insulating coating is used to connect the dynamometers on both sides, providing a complete closed loop for the shaft current, truly simulating the shaft current existing in the power transmission path of the dual-axis EMC loading test system under actual load conditions, and verifying whether the background noise of the anechoic chamber meets the international standard limit under this condition; the method using the shaft current test structure effectively fills the gap in the current shaft current test method of the dual-axis EMC loading test system, provides a more comprehensive and accurate solution for the EMC loading test of the electric drive assembly of new energy vehicles, and is conducive to promoting the progress of testing technology in related fields.

[0038] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the technical solution. Those skilled in the art should understand that those modifications or equivalent substitutions of the technical solution of the present invention that do not depart from the purpose and scope of the technical solution should be included in the scope of the claims of the present invention.

Claims

1. The shaft current test structure for the dual-axis EMC load test system is characterized by: The invention comprises a gearbox arranged in an anechoic chamber, the gearbox is a shifting gearbox, an output shaft of the gearbox is connected with one end of a first through-wall shaft arranged horizontally, the other end of the first through-wall shaft extends out of the anechoic chamber and is connected to a first dynamometer by transmission, an input shaft of the gearbox is connected to one end of a horizontally arranged test shaft by transmission, the other end of the test shaft is connected to one end of a horizontally arranged second through-wall shaft by transmission, the other end of the second through-wall shaft extends out of the anechoic chamber and is connected to a second dynamometer by transmission; the test shaft is grounded and has a smooth and conductive outer cylindrical surface, an annular current probe is rotatably sleeved on the test shaft, a probe clamp for fixing the current probe is arranged below the current probe, a processing unit is arranged in a shielding chamber outside the anechoic chamber, and the processing unit is electrically connected to the current probe for obtaining shaft current data.

2. According to claim 1, the shaft current test structure for the dual-axis EMC load test system is characterized in that: The processing unit comprises an EMI receiver and a computer. The EMI receiver is electrically connected to the current probe and the computer respectively. An attenuator is also electrically connected between the EMI receiver and the current probe.

3. The shaft current test structure for the dual-axis EMC load test system according to claim 2, characterized in that: The first through-wall shaft is connected to the input shaft of the first dynamometer through the first coupling, the first through-wall shaft is connected to the output shaft of the gear box through the second coupling, the test shaft is connected to the input shaft of the gear box through the third coupling, the test shaft is connected to the second through-wall shaft through the fourth coupling, and the second through-wall shaft is connected to the input shaft of the second dynamometer through the fifth coupling.

4. The shaft current test structure for the dual-axis EMC load test system according to claim 2, characterized in that: A first bearing seat and a second bearing seat for support are respectively provided on the first through-wall shaft near the first coupling and the second coupling, a third bearing seat and a fifth bearing seat are respectively provided on the test shaft near the third coupling and the fourth coupling, and a sixth bearing seat and a seventh bearing seat are respectively provided in the middle part of the second through-wall shaft and near the fifth bearing seat.

5. The shaft current test structure for the dual-axis EMC load test system according to claim 1, characterized in that: A fourth bearing seat for support is provided in the middle of the test shaft, on which an annular carbon brush is rotatably sleeved on the test shaft and grounded, and the inner side of the annular carbon brush contacts the outer cylindrical surface of the test shaft to ground the test shaft.

6. The shaft current test structure for the dual-axis EMC load test system according to claim 1, characterized in that: The probe clamp includes a clamping plate, a first connecting plate, a second connecting plate, a third connecting plate and a clamp base which are sequentially connected from top to bottom. The upper end of the clamping plate has a clamping portion for clamping and fixing the current probe. The first connecting plate and the second connecting plate are rotatably connected via a transversely arranged first rotating shaft, and the second connecting plate and the third connecting plate are rotatably connected via a transversely arranged second rotating shaft.

7. The shaft current test structure for the dual-axis EMC load test system according to claim 6, characterized in that: The clamping portion is semicircular in shape with the concave surface facing upwards. The current probe is located on the inner side of the clamping portion. Clamping bolts are transversely penetrated at both ends of the semicircular arc on the clamping portion and are threadedly connected. The head of the clamping bolt is located on the outer side of the clamping portion so that the current probe can be clamped and fixed by tightening the clamping bolt.

8. The shaft current test structure for the dual-axis EMC load test system according to claim 6, characterized in that: The first connecting plate and the second connecting plate have connecting ears that are alternately distributed laterally at the opposite ends. The first rotating shaft is a bolt and rotates through the connecting holes on each connecting ear. The head of the bolt abuts against the connecting ear on one lateral side, and the tail is threadedly connected to the connecting ear on the other lateral side, so that the relative rotation of the first connecting plate and the second connecting plate can be limited by tightening the bolt.

9. The shaft current test structure for a dual-axis EMC load test system according to claim 6, characterized in that: The first connecting plate and the clamping plate are connected by a double ball joint universal joint, which includes a locking bolt and two limit plates arranged in parallel and at intervals. An arc-shaped limit part is connected to the inner side of the limit plate near the end, and the concave surfaces of the two limit parts at the same end are opposite to each other and form a ball bowl. A matching ball head is rotatably arranged in the ball bowl, and a connecting rod is formed on the protrusion of the ball head. The connecting rod extends from between the two limit parts, and the two ends of the double ball joint universal joint are respectively connected to the first connecting plate and the clamping plate through the connecting rod; the locking bolt vertically passes through the two limit plates, the head of the locking bolt abuts against one limit plate, and the tail is threadedly connected to the other limit plate, so as to limit the rotation of the ball head in the ball bowl by tightening the locking bolt; the third connecting plate and the fixture base are also connected by a double ball joint universal joint.

10. A shaft current test method for a dual-axis EMC load test system, characterized in that: The shaft current test method is performed using the shaft current test structure as described in any one of claims 1 to 9, including a no-load test and a loaded test; No-load test: connect the test shaft only to the input shaft of the gearbox, adjust the gearbox gear position to make the speed ratio 1:1, and test the shaft current generated by the first dynamometer and entering the anechoic chamber through the current probe; connect the test shaft only to the second through-wall shaft, and test the shaft current generated by the second dynamometer and entering the anechoic chamber through the current probe; Loading test: connect the test shaft to the input shaft of the gearbox and the second through-wall shaft respectively, adjust the gearbox gear position and control the speed of the first dynamometer and the second dynamometer to form a pair of dynamometers, and test the shaft current generated by the first dynamometer and the second dynamometer and entering the anechoic chamber through the current probe.

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