Capacitor stray inductance test method and system

Abstract

The application provides a capacitor stray inductance test method and system. The method comprises the following steps: connecting one end of a connecting line to an impedance analysis unit, and performing connection compensation on the connecting line; connecting the other end of the connecting line to a capacitor mounting unit in a test fixture to obtain a first loop, and performing open circuit compensation on the first loop; based on the first loop, connecting a shorting row unit in the test fixture to the capacitor mounting unit through a connecting piece to obtain a second loop, and performing short circuit compensation on the second loop; based on the second loop, removing the connecting piece and the shorting row unit, and connecting the capacitor mounting unit to an electrode of a capacitor to be tested to obtain a third loop, and testing the capacitor to be tested to obtain the stray inductance of the capacitor. The method is a non-discharge method stray inductance test method, eliminates the additional stray parameters introduced by the connecting line and the test fixture, and directly tests the stray inductance of a large-capacity and large-size capacitor.

Description

Technical Field

[0001] This application relates to the field of electronic power technology, and in particular to a method and system for testing stray inductance of large-capacity, large-size capacitors. Background Technology

[0002] Large-capacity, large-size metallized film capacitors are widely used in high-capacity power electronic devices such as flexible DC transmission, rail transit traction converters, industrial drives, new energy, and electric vehicles. The structure of the capacitor dictates that it possesses an equivalent series inductance. Even in the converter circuit of low-inductance busbar power devices, the stray inductance of the capacitor can affect the reverse recovery peak power of the diode and the turn-off overvoltage of the power device during switching transients. Excessive stray inductance can lead to overvoltage or failure of the power device outside its safe operating area. Therefore, accurately testing the stray inductance of capacitors is crucial for capacitor manufacturing, power electronic device design, and operation and maintenance.

[0003] Traditional testing methods mainly use the discharge method to test the stray inductance of capacitors. First, the capacitor is charged, and then the capacitor electrodes are short-circuited. The stray inductance of the capacitor is calculated by the oscillation frequency of the test current. The test results of this method include both the stray inductance of the capacitor and the stray inductance of the circuit with the electrodes short-circuited, so the test results are inaccurate. Summary of the Invention

[0004] To address the aforementioned issues, this application provides a method and system for testing stray inductance in capacitors, which solves the technical problem that existing technologies cannot accurately measure the stray inductance of large-capacity, large-size capacitors.

[0005] In a first aspect, this application provides a method for testing the stray inductance of a capacitor, comprising:

[0006] One end of the connecting line is connected to the impedance analysis unit, and the impedance analysis unit performs connection compensation on the connecting line.

[0007] The other end of the connecting wire is connected to the capacitor mounting unit in the test fixture to obtain the first circuit, and the first circuit is compensated for open circuit by the impedance analysis unit.

[0008] Based on the first circuit, the shorting block unit in the test fixture is connected to the capacitor mounting unit through the connector to obtain the second circuit, and the impedance analysis unit performs short-circuit compensation on the second circuit.

[0009] Based on the second circuit, the connector and the shorting block unit are removed, and the capacitor mounting unit is connected to the electrode of the capacitor under test to obtain the third circuit;

[0010] Based on the third circuit, the capacitor under test is tested by the impedance analysis unit to obtain the stray inductance of the capacitor.

[0011] According to an embodiment of this application, optionally, in the above-described method for testing stray inductance of a capacitor, the connection compensation of the connecting line by the impedance analysis unit includes the following steps:

[0012] The stray parameters of the connecting line are tested using the impedance analysis unit, and the impedance analysis unit is calibrated for the first time to compensate for the connection of the connecting line.

[0013] The stray parameters of the connection line include composite parameters consisting of the stray inductance, capacitance, and resistance of the connection line.

[0014] According to an embodiment of this application, optionally, in the above-described capacitor stray inductance testing method, the first circuit is in an open circuit state;

[0015] The first circuit is compensated for open circuit by the impedance analysis unit, including the following steps:

[0016] The equivalent parallel stray parameters of the capacitor mounting unit are tested by the impedance analysis unit, and the impedance analysis unit is calibrated a second time to compensate for the open circuit of the first circuit.

[0017] The equivalent parallel stray parameters of the capacitor mounting unit include composite parameters consisting of the equivalent parallel stray inductance, capacitance, and resistance of the capacitor mounting unit.

[0018] According to an embodiment of this application, optionally, in the above-described capacitor stray inductance testing method, the second circuit is in a short-circuit state;

[0019] The impedance analysis unit performs short-circuit compensation on the second circuit, including the following steps:

[0020] The equivalent series stray parameters of the capacitor mounting unit are tested by the impedance analysis unit, and the impedance analysis unit is calibrated for the third time to compensate for the short circuit of the second circuit.

[0021] The equivalent series stray parameters of the capacitor mounting unit include composite parameters consisting of the equivalent series stray inductance, capacitance, and resistance of the capacitor mounting unit.

[0022] According to an embodiment of this application, optionally, in the above-described method for testing stray inductance of capacitors, after the step of connecting the other end of the connecting wire to the capacitor mounting unit in the test fixture, the method further includes:

[0023] By using a pre-established equivalent circuit model, the dimensions of the connector are determined when the stray inductance of the capacitor mounting unit is equal to the combined stray inductance of the test fixture.

[0024] Wherein, the combined stray inductance of the test fixture is the sum of the stray inductance of the capacitor mounting unit, the stray inductance of the connector, and the stray inductance of the jumper unit;

[0025] The equivalent circuit model includes a three-dimensional model of the combination of the capacitor mounting unit, the connector, and the jumper unit.

[0026] Secondly, this application provides a test system for stray inductance of capacitors, comprising:

[0027] Impedance analysis unit, connecting wires, and test fixture, wherein the test fixture includes a capacitor mounting unit, a jumper unit, and connectors;

[0028] The impedance analysis unit is used to perform connection compensation, open circuit compensation, short circuit compensation, stray parameter and stray inductance tests.

[0029] The connecting line is used to connect the impedance analysis unit and the capacitor mounting unit;

[0030] The capacitor mounting unit is used to connect the connecting line to the electrodes of the capacitor under test when the impedance analysis unit performs stray inductance testing on the capacitor under test.

[0031] The shorting bus unit is used to connect to the capacitor mounting unit via the connector when the impedance analysis unit performs short-circuit compensation.

[0032] According to an embodiment of this application, optionally, in the above-described test system for stray inductance of capacitors, the connecting line is a coaxial cable;

[0033] The number of connecting lines is 4.

[0034] According to an embodiment of this application, optionally, in the above-described test system for stray inductance of a capacitor, the number of connectors is the same as the number of electrodes of the capacitor under test, and the number of connectors is 4.

[0035] The connector is made of a conductive material.

[0036] According to embodiments of this application, optionally, in the above-described test system for stray inductance of capacitors,

[0037] The capacitor mounting unit includes a first printed circuit board, which is provided with a first through hole, a second through hole, a third through hole and a fourth through hole for sequentially connecting to the connector.

[0038] The capacitor mounting unit has a first copper metal layer and a second copper metal layer on the side away from the shorting bus unit; wherein the first copper metal layer is in contact with the first through hole and the third through hole, and the second copper metal layer is in contact with the second through hole and the fourth through hole; the first copper metal layer and the second copper metal layer are not in contact.

[0039] According to an embodiment of this application, optionally, in the above-described capacitor stray inductance testing system, the capacitor mounting unit has four cable sockets on the side away from the shorting bar unit, the cable sockets are used to connect the connecting wires, and the capacitor mounting unit has shielding pins on the opposite side of the cable sockets.

[0040] According to an embodiment of this application, optionally, in the above-mentioned test system for stray inductance of capacitors, the shorting bus unit includes a second printed circuit board or metal plate, and the shorting bus unit is provided with a fifth through hole, a sixth through hole, a seventh through hole and an eighth through hole for sequentially connecting to the connector.

[0041] The second printed circuit board has a third copper metal layer on both the side near the capacitor mounting unit and the side away from the capacitor mounting unit, wherein the third copper metal layer is in contact with the fifth, sixth, seventh and eighth through holes.

[0042] Compared with the prior art, one or more embodiments of the above solutions may have the following advantages or beneficial effects:

[0043] This application provides a method and system for testing stray inductance in capacitors. The method includes connecting one end of a connecting wire to an impedance analysis unit and performing connection compensation on the connecting wire through the impedance analysis unit; connecting the other end of the connecting wire to a capacitor mounting unit in a test fixture to obtain a first circuit and performing open-circuit compensation on the first circuit through the impedance analysis unit; based on the first circuit, connecting a shorting busbar unit in the test fixture to the capacitor mounting unit through a connector to obtain a second circuit and performing short-circuit compensation on the second circuit through the impedance analysis unit; based on the second circuit, removing the connector and the shorting busbar unit, and connecting the capacitor mounting unit to the electrodes of the capacitor under test to obtain a third circuit; and testing the capacitor under test through the impedance analysis unit based on the third circuit to obtain the stray inductance of the capacitor. This method is a non-discharge stray inductance testing method, eliminating the additional stray parameters introduced by the connecting wire and the test fixture. It requires no external voltage and no high voltage or high current, directly and accurately testing the stray inductance of large-capacity, large-size capacitors. The testing method is convenient, safe, efficient, and provides accurate test results. Attached Figure Description

[0044] The present application will be described in more detail below based on embodiments and with reference to the accompanying drawings:

[0045] Figure 1 A schematic flowchart of a capacitor stray inductance testing method provided in an embodiment of this application;

[0046] Figure 2 This is a schematic diagram of the structure of a capacitor stray inductance testing system provided in an embodiment of this application;

[0047] Figure 3a A front view of the capacitor mounting unit in a capacitor stray inductance test fixture provided in this application embodiment;

[0048] Figure 3b A schematic diagram of the back structure of a capacitor mounting unit in a capacitor stray inductance test fixture provided in an embodiment of this application;

[0049] Figure 3c This is a schematic diagram of the shorting bus unit in a capacitor stray inductance test fixture provided in an embodiment of this application;

[0050] Figure 3d This is a schematic diagram of the structure of a connector in a capacitor stray inductance test fixture provided in an embodiment of this application;

[0051] In the accompanying drawings, the same parts are referred to by the same reference numerals, and the drawings are not drawn to scale. Detailed Implementation

[0052] The following detailed description of the embodiments of this application, in conjunction with the accompanying drawings, will provide a thorough understanding of how this application uses technical means to solve technical problems and achieve corresponding technical effects, enabling its implementation. The embodiments of this application and the various features within them can be combined with each other without conflict, and all resulting technical solutions are within the protection scope of this application.

[0053] Example 1

[0054] Please see Figure 1 This application provides a method for testing stray inductance of a capacitor, comprising:

[0055] Step S110: Connect one end of the connecting line to the impedance analysis unit, and perform connection compensation on the connecting line through the impedance analysis unit.

[0056] The impedance analysis unit includes an impedance analyzer.

[0057] The connecting line is a flexible cable, including the dedicated extension line for the impedance analyzer, or a custom-made coaxial cable or radio frequency cable. Preferably, a dedicated extension line provided by the impedance analyzer manufacturer is used. The flexible cable can easily achieve a flexible connection between the impedance analyzer and the test fixture and / or the capacitor under test.

[0058] The impedance analysis unit is used to compensate for the connection of the connecting lines, including the following steps:

[0059] The stray parameters of the connecting line are tested using the impedance analysis unit, and the impedance analyzer is calibrated for the first time to compensate for the connection of the connecting line.

[0060] The stray parameters of the connection line include composite parameters consisting of the stray inductance, capacitance, and resistance of the connection line.

[0061] The connection compensation can eliminate the influence of stray parameters of the connection line on the stray inductance test of the capacitor under test.

[0062] Step S120: Connect the other end of the connecting wire to the capacitor mounting unit in the test fixture to obtain the first circuit, and perform open circuit compensation on the first circuit through the impedance analysis unit.

[0063] The test fixture includes a capacitor mounting unit, connectors, and a jumper bar unit.

[0064] The capacitor mounting unit includes a first printed circuit board, which is provided with a first through hole, a second through hole, a third through hole and a fourth through hole for sequentially connecting to the connector.

[0065] The capacitor mounting unit has a first copper metal layer and a second copper metal layer on the side away from the shorting bus unit; wherein the first copper metal layer and the second copper metal layer are covered with a protective layer, the first copper metal layer is in contact with the first through hole and the third through hole, and the second copper metal layer is in contact with the second through hole and the fourth through hole; the first copper metal layer and the second copper metal layer are not in contact.

[0066] The capacitor mounting unit has four cable sockets on the side away from the shorting bar unit. The core wires of the two lower cable sockets contact the first and third through holes via the first copper metal layer, while the core wires of the two upper cable sockets contact the second and fourth through holes via the second copper metal layer.

[0067] The connecting line is connected to the capacitor mounting unit via the cable socket. Because the first copper metal layer and the second copper metal layer of the capacitor mounting unit are not in contact, the first circuit is in an open circuit state. Correspondingly, the first circuit is compensated for by the impedance analysis unit, including the following steps:

[0068] The equivalent parallel stray parameters of the capacitor mounting unit are tested using the impedance analysis unit, and the impedance analysis unit is then calibrated a second time to compensate for the open circuit of the first circuit.

[0069] The equivalent parallel stray parameters of the capacitor mounting unit include composite parameters consisting of the equivalent parallel stray inductance, capacitance, and resistance of the capacitor mounting unit.

[0070] The open-circuit compensation eliminates the influence of the equivalent parallel stray parameters of the capacitor mounting unit on the stray inductance test of the capacitor under test.

[0071] After step S120, which involves connecting the impedance analysis unit and the capacitor mounting unit in the test fixture via connecting wires, the method further includes:

[0072] By simulating the equivalent circuit model of the test fixture using a pre-established three-dimensional model of the test fixture, the size of the connector is determined when the stray inductance of the capacitor mounting unit is equal to the combined stray inductance of the test fixture.

[0073] By simulating and designing appropriate dimensions for the test fixture, flexible connections between the test fixture and the connecting lines and impedance analysis unit can be easily achieved, which helps to eliminate the influence of stray parameters of the connecting lines and test fixture on the stray inductance test of the capacitor under test.

[0074] The combined stray inductance of the test fixture is the sum of the stray inductance of the capacitor mounting unit, the stray inductance of the connector, and the stray inductance of the jumper unit.

[0075] The equivalent circuit model includes a three-dimensional model of the combination of the capacitor mounting unit, the connector, and the jumper unit.

[0076] Step S130: Based on the first circuit, the shorting block unit in the test fixture is connected to the capacitor mounting unit through the connector to obtain the second circuit, and the impedance analysis unit is used to perform short-circuit compensation on the second circuit.

[0077] The shorting bus unit includes a second printed circuit board or a metal plate, the metal plate including a copper plate, an aluminum plate, and an iron plate. The shorting bus unit is provided with a fifth through hole, a sixth through hole, a seventh through hole, and an eighth through hole for sequentially connecting to the connector. A third copper metal layer is provided on both the side of the printed circuit board near the capacitor mounting unit and the side away from the capacitor mounting unit, wherein the third copper metal layer is in contact with the fifth through hole, the sixth through hole, the seventh through hole, and the eighth through hole.

[0078] The connector is connected to the first, second, third, and fourth through holes of the capacitor mounting unit, and the fifth, sixth, seventh, and eighth through holes of the shorting bus unit. Because the third copper metal layer of the shorting bus unit is in contact with the fifth, sixth, seventh, and eighth through holes, the second circuit is in a short-circuit state. Correspondingly, the impedance analysis unit performs short-circuit compensation on the second circuit, including the following steps:

[0079] The equivalent series stray parameters of the capacitor mounting unit are tested by the impedance analysis unit, and the impedance analyzer is calibrated for the third time to perform short-circuit compensation for the second circuit.

[0080] The equivalent series stray parameters of the capacitor mounting unit include composite parameters consisting of the equivalent series stray inductance, capacitance, and resistance of the capacitor mounting unit.

[0081] The short-circuit compensation can eliminate the influence of the equivalent series stray parameters of the capacitor mounting unit on the stray inductance test of the capacitor under test; the open-circuit compensation combined with the short-circuit compensation can eliminate the influence of the stray parameters of the capacitor mounting unit on the stray inductance test of the capacitor under test.

[0082] Step S140: Based on the second circuit, remove the connector and the shorting block unit, and connect the capacitor mounting unit to the electrode of the capacitor under test to obtain the third circuit.

[0083] Step S150: Based on the third circuit, the capacitor under test is tested by the impedance analysis unit to obtain the stray inductance of the capacitor.

[0084] After the connection compensation, open circuit compensation, and short circuit compensation, the influence of the stray parameters of the third circuit (including the stray parameters of the capacitor mounting unit and the stray parameters of the connecting lines) on the stray inductance test of the capacitor to be tested can be eliminated.

[0085] Subsequently, the capacitor under test is tested through the impedance analysis unit. Without the need for external voltage or high voltage and high current, the stray inductance of the capacitor can be obtained directly.

[0086] This embodiment provides a method for testing stray inductance in capacitors. The method includes connecting one end of a connecting wire to an impedance analysis unit and performing connection compensation on the connecting wire using the impedance analysis unit; connecting the other end of the connecting wire to a capacitor mounting unit in a test fixture to obtain a first circuit, and performing open-circuit compensation on the first circuit using the impedance analysis unit; based on the first circuit, connecting a shorting busbar unit in the test fixture to the capacitor mounting unit using a connector to obtain a second circuit, and performing short-circuit compensation on the second circuit using the impedance analysis unit; based on the second circuit, removing the connector and the shorting busbar unit, and connecting the capacitor mounting unit to the electrodes of the capacitor under test to obtain a third circuit; and testing the capacitor under test using the impedance analysis unit based on the third circuit to obtain the stray inductance of the capacitor. This method is a non-discharge stray inductance testing method, eliminating the additional stray parameters introduced by the connecting wire and test fixture. It requires no external voltage, no high voltage or high current, and directly tests the stray inductance of large-capacity, large-size capacitors. The testing method is convenient, safe, efficient, and provides accurate test results.

[0087] Example 2

[0088] Please see Figure 2 This application provides a capacitor stray inductance testing system for testing the stray inductance of a capacitor 4 under test. The system includes an impedance analysis unit 1, a connecting wire 2, and a test fixture 3.

[0089] The test fixture 3 includes a capacitor mounting unit 31, a shorting bar unit 32, and a connector 33.

[0090] The impedance analysis unit 1 includes impedance analyzers of different models, used for connection compensation of the connecting line 2, open circuit compensation and short circuit compensation of the test fixture, and stray inductance testing of the capacitor 4 under test.

[0091] The connecting line 2 is used to connect the impedance analysis unit 1 and the capacitor mounting unit 31.

[0092] The connecting line 2 is a coaxial flexible cable, including a dedicated extension line for the impedance analyzer 1, a custom-made coaxial cable, and connectors and cable plugs that are compatible with the cable. The cable plugs include Bayonet Nut Connectors (BNC) and similar connectors.

[0093] The number of connecting lines 2 is the same as the number of test ports (not shown in the figure) of the impedance analyzer. Optionally, the number of connecting lines 2 and the number of test ports of the impedance analyzer are both 4. Preferably, the connecting lines 2 are four dedicated extension cables with a characteristic impedance of 50 ohms provided by the impedance analyzer manufacturer, and a BNC cable plug that is compatible with the dedicated extension cables; the flexible cable can easily realize the flexible connection between the impedance analyzer and the test fixture and / or the capacitor under test.

[0094] The capacitor under test 4 includes a large-capacity, large-size capacitor.

[0095] like Figure 3c As shown, the shorting bus unit 32 is used to connect to the capacitor mounting unit 31 via the connector 33 when the impedance analysis unit 1 performs short-circuit compensation.

[0096] When the impedance analysis unit 1 performs short-circuit compensation, the shorting bus unit 32 is disposed on the back side of the capacitor mounting unit 31.

[0097] like Figure 3a As shown, this application provides a front view of the capacitor mounting unit 31 in a capacitor stray inductance test fixture. The capacitor mounting unit 31 is used to connect the connecting line 2 to the electrodes of the capacitor 4 under test when the impedance analysis unit 1 performs stray inductance testing on the capacitor 4 under test. The capacitor mounting unit 31 includes a first printed circuit board, which has a first through-hole 311, a second through-hole 312, a third through-hole 313, and a fourth through-hole 314 for sequentially connecting to the connector 33. The number of through-holes in the capacitor mounting unit 31 is the same as the number of electrodes of the capacitor 4 under test.

[0098] The dimensions of the first through hole 311, the second through hole 312, the third through hole 313 and the fourth through hole 314 are larger than the dimensions of the electrode bolts or screw holes of the capacitor under test 4. Preferably, the diameter of each through hole is 1-2 mm larger than the diameter of the electrode bolts or screw holes.

[0099] The capacitor mounting unit 31 is located on the side away from the shorting bar unit 32 (e.g., Figure 3aThe front side shown in the figure has a first copper metal layer 315 and a second copper metal layer 316. The first copper metal layer 315 and the second copper metal layer 316 are covered with a protective layer (not shown in the figure). The first copper metal layer 315 is in contact with the first through hole 311 and the third through hole 313, and the second copper metal layer 316 is in contact with the second through hole 312 and the fourth through hole 314. The first copper metal layer 315 and the second copper metal layer 316 are not in contact, and the distance between the first copper metal layer 315 and the second copper metal layer 316 is as small as possible.

[0100] Preferably, the distance between the first copper metal layer 315 and the second copper metal layer 316 is 0.5-2 mm.

[0101] The capacitor mounting unit 31 is located on the side away from the shorting bar unit 32 (i.e., as shown in the image). Figure 3a The front side (shown in the diagram) is provided with multiple cable sockets 317, each corresponding to a connector for connecting the cable. Optionally, the cable sockets include bayonet nut connectors (BNC) or similar sockets. Specifically, the core wires of the two lower cable sockets 317 (located at the corresponding position on the first copper metal layer 315) are connected to the first through hole 311 and the third through hole 313 via the first copper metal layer 315, while the core wires of the two upper cable sockets 317 (located at the corresponding position on the second copper metal layer 316) are connected to the second through hole 312 and the fourth through hole 314 via the second copper metal layer 316.

[0102] The cable socket 317 is used to connect the connecting wire 12.

[0103] The core wires of the two cable sockets 317 in the lower half of the capacitor mounting unit 31 are close to the core wires of the two cable sockets 317 in the upper half.

[0104] like Figure 3b As shown, this application provides a rear structure of a capacitor mounting unit 31 in a capacitor stray inductance test fixture. The capacitor mounting unit 31 is located on the opposite side of the cable socket 317 (i.e., as shown in the diagram). Figure 3b The back side (shown in the diagram) is provided with shielded pins 318. Shielded pins 318 correspond to cable sockets 317.

[0105] The dimensions of the capacitor mounting unit 31 meet the electrode mounting requirements of the capacitor under test 4. Optionally, the inner diameter of the through hole of the capacitor mounting unit 31 is 1-2 mm larger than the diameter of the electrode bolt or screw hole of the capacitor under test 4, and the thickness of the capacitor mounting unit 31 is 2 mm.

[0106] The shorting bus unit 32 includes a second printed circuit board or a metal plate, the metal plate including a copper plate, an aluminum plate, and an iron plate. The shorting bus unit is provided with a fifth through hole 321, a sixth through hole 322, a seventh through hole 323, and an eighth through hole 324 for sequentially connecting to the connector 33. A third copper metal layer (not shown in the figure) is provided on both the side of the printed circuit board near the capacitor mounting unit 31 (back side) and the side away from the capacitor mounting unit 31 (front side), wherein the third copper metal layer is in contact with the fifth through hole 321, the sixth through hole 322, the seventh through hole 323, and the eighth through hole 324. The number of through holes in the shorting bus unit 32 is the same as the number of electrodes of the capacitor under test 4.

[0107] The dimensions of the shorting unit 32 are the same as those of the capacitor mounting unit 31. Optionally, the inner diameter of the through hole of the shorting unit 32 is 1-2 mm larger than the diameter of the electrode bolt or screw hole of the capacitor under test 4, and the thickness of the shorting unit 32 is 2 mm.

[0108] like Figure 3d As shown, the connector 33 is used to connect the capacitor mounting unit 31 and the shorting bus unit 32. The number of connectors 33 is the same as the number of electrodes of the capacitor under test, and the material of the connectors 33 includes a conductive material. Optionally, the number of connectors 33 is 4, and the material of the connectors 33 includes at least one of copper, iron, and aluminum.

[0109] The connector 33 is designed as a through-type cylindrical structure, which may be a cylinder or a prism. Optionally, the inner diameter of the cylindrical structure is 1-2 mm larger than the diameter of the electrode bolt or screw hole of the capacitor under test, the outer diameter of the cylindrical structure is larger than the inner diameter of the cylindrical structure, and the inner diameter of the cylindrical structure is 1-2 mm larger than the diameter of the electrode contact surface of the capacitor under test.

[0110] The column height of the connector 33 was obtained through simulation design. The specific simulation method includes:

[0111] After the capacitor mounting unit 31 is designed, modeling and finite element simulation of the capacitor mounting unit 31 are performed, including: extracting the stray inductance from the two cable sockets 317 in the lower half of the capacitor mounting unit 31 through the first copper metal layer 315 contacting the first through hole 311 and the third through hole 313, and the stray inductance from the second copper metal layer 316 contacting the second through hole 312 and the fourth through hole 314 contacting the two cable sockets 317 in the upper half; then completing the corresponding shorting bar unit 32 structure design according to the structure of the capacitor mounting unit 31; then using 3D modeling software, connecting the through holes of the capacitor mounting unit 31 and the through holes of the shorting bar unit 32 through connectors to establish a combined 3D model of the capacitor mounting unit 31, the connectors 33 and the shorting bar unit 32; adjusting the connections in the 3D modeling software. The height of the component ensures that the stray inductance extracted by finite element simulation from the lower half of the cable socket 317 of the capacitor mounting unit 31 to the first through hole 311 and the third through hole 313, through the first through hole 311 and the third through hole 313 to the connector 33 to the shorting bar unit 32, then through the second through hole 312 and the fourth through hole 314 to the second through hole 312 and the fourth through hole 314 of the capacitor mounting unit 31, and through the second copper metal layer 316 to the upper half of the cable socket 317 of the capacitor mounting unit 31 is equal to the stray inductance extracted by finite element simulation from the lower half of the cable socket 317 of the capacitor mounting unit 31 to the first through hole 311 and the third through hole 313, and from the second through hole 312 and the fourth through hole 314 to the upper half of the cable socket 317. That is, the column height of the connector 33 is determined by the fact that the stray inductance of the capacitor mounting unit 31 is equal to the combined stray inductance of the capacitor mounting unit 31, the connector 33, and the shorting bar unit 32.

[0112] For a detailed embodiment of the method for testing stray inductance of capacitors using the above system, please refer to Embodiment 1. This embodiment will not be repeated here.

[0113] In summary, this application provides a method and system for testing stray inductance in capacitors. The method includes connecting one end of a connecting wire to an impedance analysis unit and performing connection compensation on the connecting wire using the impedance analysis unit; connecting the other end of the connecting wire to a capacitor mounting unit in a test fixture to obtain a first circuit and performing open-circuit compensation on the first circuit using the impedance analysis unit; based on the first circuit, connecting a shorting busbar unit in the test fixture to the capacitor mounting unit via a connector to obtain a second circuit and performing short-circuit compensation on the second circuit using the impedance analysis unit; based on the second circuit, removing the connector and the shorting busbar unit, and connecting the capacitor mounting unit to the electrodes of the capacitor under test to obtain a third circuit; and testing the capacitor under test using the impedance analysis unit based on the third circuit to obtain the stray inductance of the capacitor. This method is a non-discharge stray inductance testing method, eliminating additional stray parameters introduced by the connecting wire and test fixture. It requires no external voltage, no high voltage or high current, and directly tests the stray inductance of large-capacity, large-size capacitors. The testing method is convenient, safe, efficient, and provides accurate test results.

[0114] In the several embodiments provided in this application, it should be understood that the disclosed methods can also be implemented in other ways. The method embodiments described above are merely illustrative.

[0115] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0116] Although the embodiments disclosed in this application are as described above, the content is merely for the purpose of facilitating understanding of this application and is not intended to limit this application. Any user skilled in the art to which this application pertains may make any modifications and changes in the form and details of the implementation without departing from the spirit and scope disclosed in this application; however, the scope of patent protection of this application shall still be determined by the scope defined in the appended claims.

Claims

1. A method for testing stray inductance of a capacitor, characterized in that, include: One end of the connecting line is connected to the impedance analysis unit, and the impedance analysis unit performs connection compensation on the connecting line. The other end of the connecting wire is connected to the capacitor mounting unit in the test fixture to obtain the first circuit, and the first circuit is compensated for open circuit by the impedance analysis unit. Based on the first circuit, the shorting block unit in the test fixture is connected to the capacitor mounting unit through the connector to obtain the second circuit, and the impedance analysis unit performs short-circuit compensation on the second circuit. Based on the second circuit, the connector and the shorting block unit are removed, and the capacitor mounting unit is connected to the electrode of the capacitor under test to obtain the third circuit; Based on the third circuit, the capacitor under test is tested through the impedance analysis unit to obtain the stray inductance of the capacitor; After the step of connecting the other end of the connecting wire to the capacitor mounting unit in the test fixture, the method further includes: By using a pre-established equivalent circuit model, the dimensions of the connector are determined when the stray inductance of the capacitor mounting unit is equal to the combined stray inductance of the test fixture. Wherein, the combined stray inductance of the test fixture is the sum of the stray inductance of the capacitor mounting unit, the stray inductance of the connector, and the stray inductance of the jumper unit; The equivalent circuit model includes a three-dimensional model of the combination of the capacitor mounting unit, the connector, and the jumper unit; The method further includes: Based on the three-dimensional model, the height of the connector is adjusted in the three-dimensional modeling software so that the stray inductance of the capacitor mounting unit is equal to the combined stray inductance of the capacitor mounting unit, the connector, and the jumper unit.

2. The method for testing stray inductance of a capacitor according to claim 1, characterized in that, The impedance analysis unit is used to compensate for the connection of the connecting lines, including the following steps: The stray parameters of the connecting line are tested using the impedance analysis unit, and the impedance analysis unit is calibrated for the first time to compensate for the connection of the connecting line. The stray parameters of the connection line include composite parameters consisting of the stray inductance, capacitance, and resistance of the connection line.

3. The method for testing stray inductance of a capacitor according to claim 1, characterized in that, The first circuit is in an open circuit state; The first circuit is compensated for open circuit by the impedance analysis unit, including the following steps: The equivalent parallel stray parameters of the capacitor mounting unit are tested by the impedance analysis unit, and the impedance analysis unit is calibrated a second time to compensate for the open circuit of the first circuit. The equivalent parallel stray parameters of the capacitor mounting unit include composite parameters consisting of the equivalent parallel stray inductance, capacitance, and resistance of the capacitor mounting unit.

4. The method for testing stray inductance of a capacitor according to claim 1, characterized in that, The second circuit is in a short-circuit state; The impedance analysis unit performs short-circuit compensation on the second circuit, including the following steps: The equivalent series stray parameters of the capacitor mounting unit are tested by the impedance analysis unit, and the impedance analysis unit is calibrated for the third time to compensate for the short circuit of the second circuit. The equivalent series stray parameters of the capacitor mounting unit include composite parameters consisting of the equivalent series stray inductance, capacitance, and resistance of the capacitor mounting unit.

5. A test system for stray inductance of a capacitor, characterized in that, include: Impedance analysis unit, connecting wires, and test fixture, wherein the test fixture includes a capacitor mounting unit, a jumper unit, and connectors; The impedance analysis unit is used to perform connection compensation, open circuit compensation, short circuit compensation, stray parameter and stray inductance tests. The connecting line is used to connect the impedance analysis unit and the capacitor mounting unit; The capacitor mounting unit is used to connect the connecting line to the electrodes of the capacitor under test when the impedance analysis unit performs stray inductance testing on the capacitor under test. The shorting bus unit is used to be connected to the capacitor mounting unit via the connector when the impedance analysis unit performs short-circuit compensation. The capacitor mounting unit includes a first printed circuit board, which is provided with a first through hole, a second through hole, a third through hole and a fourth through hole for sequentially connecting to the connector. The capacitor mounting unit has a first copper metal layer and a second copper metal layer on the side away from the shorting bus unit; wherein the first copper metal layer is in contact with the first through hole and the third through hole, and the second copper metal layer is in contact with the second through hole and the fourth through hole; the first copper metal layer and the second copper metal layer are not in contact. The capacitor mounting unit has four cable sockets on the side away from the shorting bar unit. The cable sockets are used to connect the connecting wires. The capacitor mounting unit has shielding pins on the opposite side of the cable sockets. The first and second copper metal layers of the capacitor mounting unit are covered with a protective layer, and the spacing between them is 0.5-2mm.

6. The test system for stray inductance of a capacitor according to claim 5, characterized in that, The connecting line is a coaxial cable; The number of connecting lines is 4.

7. The test system for stray inductance of a capacitor according to claim 5, characterized in that, The number of connectors is the same as the number of electrodes of the capacitor under test, and the number of connectors is 4. The connector is made of a conductive material.

8. The test system for stray inductance of a capacitor according to claim 5, characterized in that, The shorting block unit includes a second printed circuit board or metal plate, and the shorting block unit is provided with a fifth through hole, a sixth through hole, a seventh through hole and an eighth through hole for sequentially connecting to the connector. The second printed circuit board has a third copper metal layer on both the side near the capacitor mounting unit and the side away from the capacitor mounting unit, wherein the third copper metal layer is in contact with the fifth, sixth, seventh and eighth through holes.

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