Common mode choke parameter design method

Abstract

The invention discloses a common-mode inductor parameter design method, which relates to the technical field of power electronics, and comprises the following steps: selecting a magnetic core material, determining basic parameters of a magnetic core and a common-mode inductor winding, and determining the width of a copper bar of the common-mode inductor winding according to busbar current, current density and copper bar thickness; and the length, the width and the height of the magnetic core are determined according to the mutual distances among the copper bars, the magnetic core shell and the magnetic core body and the width of the magnetic core body. According to the method, the size of the magnetic core of the common-mode inductor is minimized through parameterization design and the optimization process, in the design process, the size of the magnetic core is analyzed, derivation solution is conducted on the size of the magnetic core, the width of a magnetic core body with the minimum size is found, and the optimization method not only considers the inductance value and the current bearing capacity of the magnetic core, but also considers the current bearing capacity of the magnetic core. And the requirements of heat dissipation and electromagnetic shielding are also considered, the size of the magnetic core is minimized, so that the common-mode inductor can efficiently operate in a limited space, and the compactness and the integration degree of an electric drive system are remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronics, and in particular to a common-mode inductor parameter design method. Background Art

[0002] With the rapid development of the new energy vehicle industry, electric drive systems, as their core components, are facing increasingly higher requirements for performance and stability. In electric drive systems, electromagnetic interference (EMI) at the DC end is particularly prominent, especially its impact on system operation. To ensure the normal operation of electric drive systems, EMI filters are indispensable, and common-mode inductors are one of the key components. The function of common-mode inductors is to effectively filter out electromagnetic interference and ensure stable system operation.

[0003] However, in the current common-mode inductor design process, especially in the design of the common-mode inductor core size for DC-side EMI filters, a complete theoretical foundation has not yet been established. Designers are often forced to rely on existing cores for design. This approach not only makes it difficult to minimize the core volume, limiting the overall compactness and integration of the electric drive system, but also fails to fully consider the core's thermal design. The core's thermal design is crucial to ensure the stable operation of the common-mode inductor in high-temperature environments. Ignoring this issue may, to a certain extent, affect the spatial layout and performance optimization of new energy vehicles.

[0004] In order to solve the above problems, a common-mode inductor parameter design method is proposed. It comprehensively considers multiple aspects such as material selection, size design and thermal design of the magnetic core, aiming to achieve miniaturized design and efficient heat dissipation of the common-mode inductor, thereby meeting the high performance and stability requirements of the electric drive system of new energy vehicles. Summary of the Invention

[0005] The present invention aims to provide a method for designing common-mode inductor parameters to solve the problems raised in the above background technology.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0007] A common-mode inductor parameter design method includes the following steps:

[0008] Step 1: Select the core material, determine the basic parameters of the core and common-mode inductor winding, and determine the copper busbar width of the common-mode inductor winding based on the busbar current, current density, and copper busbar thickness;

[0009] Step 2: Determine the length, width, and height of the magnetic core based on the distances between the copper busbar, the magnetic core shell, and the magnetic core body, as well as the width of the magnetic core body;

[0010] Step 3: Determine the volume of the core based on the length, width, and height of the core, and organize it into a standard format for parameterization.

[0011] Step 4: Based on the determined core volume, derive and solve to find the core body width that minimizes the core volume;

[0012] Step 5: Calculate the busbar loss and temperature rise based on the busbar current and busbar volume. At the same time, calculate the core loss and temperature rise based on the Steinmetz formula.

[0013] Step 6: If the total temperature rise of the core shell exceeds the maximum allowable temperature, increase the distance between the core body and the core shell, and repeat steps 2 to 5 until the temperature rise meets the requirements.

[0014] A further improvement of the technical solution of the present invention is that the step 1 specifically includes:

[0015] Collect characteristic data of different magnetic core materials, including but not limited to magnetic permeability, saturation magnetic induction intensity, Curie temperature, loss characteristics, etc. The magnetic core material is a nanocrystalline material or a ferrite material, and other materials such as ferrite can also be used. The collected material characteristic data are sorted and a magnetic core material characteristic database is established;

[0016] Identify the specific application scenarios of common-mode inductors and analyze their application requirements, including operating frequency range, maximum current, required inductance value, ambient temperature, etc. Based on the application requirements, search for suitable materials in the established magnetic core material property database;

[0017] The core shape and common-mode inductor winding structure are determined based on the selected core material. The core is a rectangular core, but other core shapes can also be used. The common-mode inductor winding uses two sets of positive and negative copper bars, which can be placed overlapping or in parallel.

[0018] According to the design requirements of the electric drive system, determine the current, current density and copper busbar thickness in the DC busbar, and then calculate the copper busbar width to meet the performance requirements of the electric drive system;

[0019] The calculation formula for the copper busbar width is:

[0020]

[0021] Where, l copper is the width of the copper busbar, I rms is the current in the DC busbar, J is the current density, w copper is the copper busbar thickness.

[0022] A further improvement of the technical solution of the present invention is that the step 2 specifically includes:

[0023] According to the electromagnetic design and heat dissipation requirements, set the distance between the copper busbar and the core shell;

[0024] According to the heat dissipation and electromagnetic isolation requirements of the core, set the distance between the core shell and the core body;

[0025] According to the electromagnetic design requirements of the core, set the width of the core body;

[0026] Calculate the length of the core based on the width of the copper busbar, the distance between the copper busbar and the core shell, the distance between the core shell and the core body, and the width of the core body. The core length should ensure that the copper busbar is completely covered by the core to achieve effective electromagnetic shielding and heat conduction.

[0027] Calculate the width of the core based on the thickness of the copper busbar, the distance between the copper busbar and the core shell, the distance between the core shell and the core body, the width of the core body, and the insulation distance between the two copper busbars.

[0028] The height of the core is calculated by comprehensively considering the copper busbar width, copper busbar thickness, distance between the copper busbar and the core shell, distance between the core shell and the core body, width of the core body, and insulation distance between the two copper busbars, combined with the common mode inductance value, vacuum permeability and relative permeability.

[0029] A further improvement of the technical solution of the present invention is that the calculation formula for the length of the magnetic core is:

[0030] l case =l copper +2w1+4w2+2w core ;

[0031] Where, l case is the length of the core, l copper is the width of the copper busbar, w1 is the distance between the copper busbar and the core shell, w2 is the distance between the core shell and the core body, w core is the width of the core body;

[0032] The calculation formula of the width of the magnetic core is:

[0033] w case =2w copper +2w1+4w2+2w core +w3;

[0034] Where w case is the width of the core, w copper is the thickness of the copper busbar, w3 is the insulation distance between two copper busbars;

[0035] The calculation formula of the height of the magnetic core is:

[0036]

[0037] Where h case is the height of the core, L is the common mode inductance, μ0 is the vacuum permeability, μ r is the relative magnetic permeability.

[0038] A further improvement of the technical solution of the present invention is that the step three specifically includes:

[0039] For rectangular cores, the core volume is calculated based on the determined core length, width, and height.

[0040] The volume of the magnetic core is organized into a standard format to facilitate subsequent analysis and optimization, and organized into a parameterized formula for easy subsequent use;

[0041] The calculation formula of the volume of the magnetic core is:

[0042]

[0043] Where V core is the volume of the core, l case is the length of the core, w case is the width of the core, h case is the height of the core, l copper is the width of the copper busbar, w1 is the distance between the copper busbar and the core shell, w2 is the distance between the core shell and the core body, w core is the width of the core body, w3 is the insulation distance between the two copper bars, and w copper is the copper busbar thickness, L is the common mode inductance, μ0 is the vacuum permeability, μ r is the relative magnetic permeability;

[0044] The above formula is organized into a standard format as follows:

[0045]

[0046] in:

[0047]

[0048]

[0049] A further improvement of the technical solution of the present invention is that the step 4 specifically includes:

[0050] Based on the calculated core volume, the derivative of the core volume with respect to the core body width is derived to obtain the derivative of the volume with respect to the width;

[0051] Set the derivative of volume with respect to width to zero and solve for the width w of the core body corresponding to the minimum volume. m, and verify the width obtained to make it meet the electromagnetic design and heat dissipation requirements;

[0052] The calculation formula for the width of the magnetic core body corresponding to the minimum volume is:

[0053]

[0054] Where w m is the width of the core body corresponding to the minimum volume,

[0055] A further improvement of the technical solution of the present invention is that the step five specifically includes:

[0056] Calculate the busbar resistance based on the busbar resistivity, busbar cross-sectional area, copper busbar width and volume, and calculate the busbar loss based on the busbar current and busbar resistance;

[0057] Calculate the busbar thermal resistance based on the thermal resistance from the busbar to the core shell, and multiply the busbar loss and the busbar thermal resistance to calculate the busbar temperature rise;

[0058] Use the Steinmetz formula to calculate the core loss by combining material constants, operating frequency, and magnetic flux density, where the magnetic flux density is obtained based on the core inductance and current;

[0059] Calculate the core thermal resistance based on the thermal resistance from the core body to the core shell, and calculate the core temperature rise by combining the core loss and the core thermal resistance.

[0060] The busbar temperature rise and the core temperature rise are added together, and the total core shell temperature rise is obtained based on the core shell temperature rise caused by the busbar loss and the core loss.

[0061] A further improvement of the technical solution of the present invention is that the calculation formula of the busbar loss is:

[0062]

[0063]

[0064] Where, P loss_copper is the busbar loss, I rms is the current in the DC busbar, R copper is the busbar resistance, ρ is the busbar resistivity, l copper is the width of the copper busbar, A copper is the busbar cross-sectional area;

[0065] The calculation formula of the core loss is:

[0066] P loss_core =k×f α ×Bβ ;

[0067]

[0068] Where, P loss_core is the core loss, k, α and β are material constants, B is the magnetic flux density, f is the operating frequency, l core is the common mode inductance, μ0 is the vacuum permeability, μ r is the relative magnetic permeability;

[0069] The calculation formulas for the busbar temperature rise and the core temperature rise are:

[0070] ΔT1=P loss_copper R cop-ca ;

[0071] ΔT2=P loss_core R core-ca ;

[0072] Where ΔT1 is the busbar temperature rise, ΔT2 is the core temperature rise, R cop-ca is the thermal resistance from busbar to core housing, R core-ca is the thermal resistance from the core body to the core shell;

[0073] The calculation formula for the total temperature rise of the core shell is:

[0074] ΔT total =ΔT1+ΔT2;

[0075] Where, ΔT total is the total temperature rise of the core shell.

[0076] A further improvement of the technical solution of the present invention is that the step six specifically includes:

[0077] Compare the calculated total temperature rise of the core shell with the maximum allowable temperature;

[0078] If the total temperature rise of the core shell exceeds the maximum allowable temperature, increase the distance between the core body and the core shell;

[0079] Recalculate the thermal resistance from the busbar to the core shell and the thermal resistance from the core body to the core shell based on the new distance between the core body and the core shell;

[0080] Use the new thermal resistance and busbar loss to recalculate the busbar temperature rise, and use the new thermal resistance and core loss to recalculate the core temperature rise. Then, add the new busbar temperature rise and core temperature rise to get the new total temperature rise of the core shell.

[0081] Compare the total temperature rise of the new core shell with the maximum allowable temperature. If the total temperature rise of the new core shell still exceeds the maximum allowable temperature, repeat steps 2 to 5 until the temperature rise meets the requirements.

[0082] Due to the adoption of the above technical solution, the present invention has the following technical advancements compared to the prior art:

[0083] 1. The present invention provides a common-mode inductor parameter design method. Through parametric design and optimization processes, the core volume of the common-mode inductor is minimized. During the design process, by analyzing the core volume and taking its derivative and solving it, the core body width that minimizes the volume is found. This optimization method not only considers the inductance value and current carrying capacity of the core, but also takes into account the requirements of heat dissipation and electromagnetic shielding. The minimized core volume enables the common-mode inductor to operate efficiently in a limited space, significantly improving the compactness and integration of the electric drive system. This is especially important for application scenarios such as new energy vehicles that have extremely high requirements for space layout. It can free up more space for other key components, optimize the overall vehicle layout, and improve overall performance.

[0084] 2. The present invention provides a common-mode inductor parameter design method, which optimizes thermal performance by performing detailed calculations on the loss and temperature rise of the busbar and the magnetic core, and adjusting the distance between the magnetic core body and the magnetic core shell. The loss is calculated based on the busbar current and resistance, and the temperature rise is calculated in combination with the thermal resistance. At the same time, the Steinmetz formula is used to calculate the magnetic core loss, and the temperature rise is calculated based on the magnetic core thermal resistance. The distance between the magnetic core body and the shell is iteratively adjusted to ensure that the total temperature rise does not exceed the maximum allowable temperature. This optimized thermal design method can effectively reduce the temperature rise of the magnetic core shell, avoid performance degradation and reliability problems caused by high temperature, which is crucial for the stable operation of the electric drive system at high power and high frequency, and can significantly extend the service life of the equipment and reduce maintenance costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0085] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments described in the present invention. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0086] Figure 1 This is a schematic diagram of the common-mode inductor design of the present invention;

[0087] Figure 2 Schematic diagram of the method of the present invention. DETAILED DESCRIPTION

[0088] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0089] Examples, such as Figure 1 、 Figure 2 As shown, the present invention provides a common mode inductor parameter design method, comprising the following steps:

[0090] Step 1: Select the core material, determine the basic parameters of the core and common-mode inductor winding, and determine the copper busbar width of the common-mode inductor winding based on the busbar current, current density and copper busbar thickness. Collect characteristic data of different core materials, including but not limited to magnetic permeability, saturation magnetic induction intensity, Curie temperature, loss characteristics, etc. Among them, the core material is nanocrystalline material or ferrite material, and other materials such as ferrite can also be selected. The collected material characteristic data are sorted out to establish a core material characteristic database for subsequent query and analysis, clarify the specific application scenarios of common-mode inductors, analyze the application requirements of common-mode inductors including operating frequency range, maximum current, required inductance value, ambient temperature, etc., and query the suitable materials in the established core material characteristic database according to the application requirements. For example, for high-frequency applications (>100 MHz), nickel-zinc ferrite can be selected because it has low initial magnetic permeability but can maintain constant magnetic permeability at high frequencies. For low-frequency applications (10kHz to 50MHz), manganese-zinc ferrite can be selected because of its high magnetic permeability and can provide a larger inductance value. The core shape and common-mode inductor winding structure are determined based on the selected core material. The core is a rectangular core, and other core shapes can also be selected. The common-mode inductor winding uses two sets of positive and negative copper bars, which can be overlapped or placed in parallel. Overlapping the two sets of copper bars can optimize electromagnetic performance and reduce parasitic effects. Placing the two sets of copper bars in parallel is suitable for scenarios that require a larger heat dissipation area. Based on the design requirements of the electric drive system, determine the current, current density, and copper bar thickness in the DC busbar, and then calculate the copper bar width to meet the performance requirements of the electric drive system;

[0091] The calculation formula for the copper busbar width is:

[0092]

[0093] Where, l copper is the width of the copper busbar, I rms is the current in the DC busbar, J is the current density, w copper is the copper busbar thickness;

[0094] Step 2: Determine the length, width, and height of the magnetic core based on the mutual distances between the copper busbar, the core shell, and the core body, as well as the width of the core body. Set the distance between the copper busbar and the core shell based on the electromagnetic design and heat dissipation requirements. This distance ensures that the heat generated by the copper busbar can be effectively transferred to the core shell, and avoids adverse effects of the electromagnetic field on the core shell. Set the distance between the core shell and the core body based on the heat dissipation and electromagnetic isolation requirements of the core. This distance ensures that the heat of the core body can be effectively transferred to the core shell, and avoids electromagnetic interference between the core body and the core shell. Set the width of the core body based on the electromagnetic design requirements of the core. This width meets the requirements of the inductance value and current carrying capacity of the core, ensuring that the core can provide a stable inductance value under normal working conditions. Combined with the width of the copper busbar and the distance between the copper busbar and the core shell, the distance between the core shell and the core body is the best. The length of the magnetic core is calculated based on the distance between the core shell and the core body, and the width of the core body. The length of the magnetic core ensures that the copper busbar can be completely covered by the magnetic core to achieve effective electromagnetic shielding and heat conduction. The width of the magnetic core is calculated based on the thickness of the copper busbar, the distance between the copper busbar and the core shell, the distance between the core shell and the core body, the width of the core body, and the insulation distance between the two copper busbars. The height of the magnetic core is calculated based on the width of the copper busbar, the thickness of the copper busbar, the distance between the copper busbar and the core shell, the distance between the core shell and the core body, the width of the core body, and the insulation distance between the two copper busbars, and combined with the common mode inductance value, vacuum permeability and relative permeability. The height of the magnetic core meets the requirements of the common mode inductance value, and the magnetic permeability and saturation magnetic induction intensity of the core material are taken into account to ensure that the core will not saturate under normal working conditions.

[0095] In addition, the length of the core is calculated as:

[0096] l case =l copper +2w1+4w2+2w core ;

[0097] Where, l case is the length of the core, l copper is the width of the copper busbar, w1 is the distance between the copper busbar and the core shell, w2 is the distance between the core shell and the core body, w core is the width of the core body;

[0098] The calculation formula of the core width is:

[0099] w case =2w copper +2w1+4w2+2w core +w3;

[0100] Where w case is the width of the core, w copperis the thickness of the copper busbar, w3 is the insulation distance between two copper busbars;

[0101] The calculation formula for the core height is:

[0102]

[0103] Where h case is the height of the core, L is the common mode inductance, μ0 is the vacuum permeability, μ r is the relative magnetic permeability;

[0104] Step 3: Determine the volume of the core based on the length, width, and height of the core, organize it into a standard format, and perform parameterization. For rectangular cores, calculate the volume of the core based on the determined length, width, and height of the core. Organize the volume of the core into a standard format to facilitate subsequent analysis and optimization, and organize it into a parameterized formula for easy subsequent use.

[0105] The calculation formula of the core volume is:

[0106]

[0107] Where V core is the volume of the core, l case is the length of the core, w case is the width of the core, h case is the height of the core, l copper is the width of the copper busbar, w1 is the distance between the copper busbar and the core shell, w2 is the distance between the core shell and the core body, w core is the width of the core body, w3 is the insulation distance between the two copper bars, and w copper is the copper busbar thickness, L is the common mode inductance, μ0 is the vacuum permeability, μ r is the relative magnetic permeability;

[0108] The above formula is organized into a standard format as follows:

[0109]

[0110] in:

[0111]

[0112] Step 4: Based on the determined core volume, perform derivative and solve to find the core body width that minimizes the core volume. Based on the calculated core volume, take the derivative of the core volume with respect to the core body width to obtain the derivative of the volume with respect to the width. Set the derivative of the volume with respect to the width to zero and solve to obtain the core body width w corresponding to the minimum volume. m , and verify the width obtained to make it meet the electromagnetic design and heat dissipation requirements;

[0113] The calculation formula for the width of the core body corresponding to the minimum volume is:

[0114]

[0115] Where w m is the width of the core body corresponding to the minimum volume,

[0116] Step 5. Calculate the busbar loss and temperature rise based on the busbar current and busbar volume. At the same time, calculate the core loss and temperature rise based on the Steinmetz formula. Calculate the busbar resistance based on the busbar resistivity, busbar cross-sectional area, copper bus width and volume. Calculate the busbar loss based on the busbar current and busbar resistance. Calculate the busbar thermal resistance based on the thermal resistance from the busbar to the core shell. Multiply the busbar loss and the busbar thermal resistance to obtain the busbar temperature rise. Calculate the core loss using the Steinmetz formula based on the material constant, operating frequency, and magnetic flux density. The magnetic flux density is obtained based on the inductance and current of the core. Calculate the core thermal resistance based on the thermal resistance from the core body to the core shell. Combine the core loss and the core thermal resistance to calculate the core temperature rise. Add the busbar temperature rise and the core temperature rise. Obtain the total temperature rise of the core shell based on the temperature rise of the core shell caused by the busbar loss and the core loss.

[0117] The calculation formula for busbar loss is:

[0118]

[0119] Where, P loss_copper is the busbar loss, I rms is the current in the DC busbar, R copper is the busbar resistance, ρ is the busbar resistivity, l copper is the width of the copper busbar, A copper is the busbar cross-sectional area;

[0120] The calculation formula for core loss is:

[0121] P loss_core =k×f α ×B β ;

[0122]

[0123] Where, P loss_core is the core loss, k, α and β are material constants, B is the magnetic flux density, f is the operating frequency, l core is the common mode inductance, μ0 is the vacuum permeability, μ r is the relative magnetic permeability;

[0124] The calculation formulas for busbar temperature rise and core temperature rise are:

[0125] ΔT1=P loss_copper R cop-ca ;

[0126] ΔT2=P loss_core R core-ca ;

[0127] Where ΔT1 is the busbar temperature rise, ΔT2 is the core temperature rise, R cop-ca is the thermal resistance from busbar to core housing, R core-ca is the thermal resistance from the core body to the core shell;

[0128] The total temperature rise of the core shell is calculated as follows:

[0129] ΔT total =ΔT1+ΔT2;

[0130] Where, ΔT total is the total temperature rise of the core shell;

[0131] Step 6. If the total temperature rise of the core shell exceeds the maximum allowable temperature, increase the distance between the core body and the core shell, and re-execute steps 2 to 5 until the temperature rise meets the requirements. Compare the calculated total temperature rise of the core shell with the maximum allowable temperature. If the total temperature rise of the core shell exceeds the maximum allowable temperature, increase the distance between the core body and the core shell, wherein the increased distance is determined according to the thermal design requirements and the heat dissipation capacity of the core. Recalculate the thermal resistance from the busbar to the core shell and the thermal resistance from the core body to the core shell according to the new distance between the core body and the core shell. Use the new thermal resistance and busbar loss to recalculate the busbar temperature rise. Use the new thermal resistance and core loss to recalculate the core temperature rise. Then, use the new busbar temperature rise and core temperature rise to obtain the new total temperature rise of the core shell. Compare the new total temperature rise of the core shell with the maximum allowable temperature. If the new total temperature rise of the core shell still exceeds the maximum allowable temperature, repeat steps 2 to 5 until the temperature rise meets the requirements.

[0132] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. A common mode inductor parameter design method, characterized in that: The following steps are involved: Step 1: Select the core material, determine the basic parameters of the core and common-mode inductor winding, and determine the copper busbar width of the common-mode inductor winding based on the busbar current, current density, and copper busbar thickness; Step 2: Determine the length, width, and height of the magnetic core based on the distances between the copper busbar, the magnetic core shell, and the magnetic core body, as well as the width of the magnetic core body; Step 3: Determine the volume of the core based on the length, width, and height of the core, and organize it into a standard format for parameterization. Step 4: Based on the determined core volume, derive and solve to find the core body width that minimizes the core volume; Step 5: Calculate the busbar loss and temperature rise based on the busbar current and busbar volume. At the same time, calculate the core loss and temperature rise based on the Steinmetz formula. Step 6: If the total temperature rise of the core shell exceeds the maximum allowable temperature, increase the distance between the core body and the core shell, and repeat steps 2 to 5 until the temperature rise meets the requirements.

2. The common-mode inductor parameter design method according to claim 1, wherein: The step 1 specifically includes: Collect characteristic data of different magnetic core materials, including but not limited to magnetic permeability, saturation magnetic induction intensity, Curie temperature, loss characteristics, etc., where the magnetic core material is nanocrystalline material, and organize the collected material characteristic data to establish a magnetic core material characteristic database; Identify the specific application scenarios of common-mode inductors and analyze their application requirements, including operating frequency range, maximum current, required inductance value, and ambient temperature. Based on these requirements, search for suitable materials in the established magnetic core material property database. Based on the selected magnetic core material, determine the magnetic core shape and the structure of the common-mode inductor winding. The magnetic core is a rectangular core, and the common-mode inductor winding uses two sets of positive and negative copper bars. The two sets of copper bars can be placed overlapping or in parallel. According to the design requirements of the electric drive system, determine the current, current density and copper busbar thickness in the DC busbar, and then calculate the copper busbar width; The calculation formula for the copper busbar width is: Where, l copper is the width of the copper busbar, I rms is the current in the DC busbar, J is the current density, w copper is the copper busbar thickness.

3. The common-mode inductor parameter design method according to claim 2, wherein: The second step specifically includes: According to the electromagnetic design and heat dissipation requirements, set the distance between the copper busbar and the core shell; According to the heat dissipation and electromagnetic isolation requirements of the core, set the distance between the core shell and the core body; According to the electromagnetic design requirements of the core, set the width of the core body; Calculate the length of the core based on the width of the copper busbar, the distance between the copper busbar and the core shell, the distance between the core shell and the core body, and the width of the core body. Calculate the width of the core based on the thickness of the copper busbar, the distance between the copper busbar and the core shell, the distance between the core shell and the core body, the width of the core body, and the insulation distance between the two copper busbars. The height of the core is calculated by comprehensively considering the copper busbar width, copper busbar thickness, distance between the copper busbar and the core shell, distance between the core shell and the core body, width of the core body, and insulation distance between the two copper busbars, combined with the common mode inductance value, vacuum permeability and relative permeability.

4. The common-mode inductor parameter design method according to claim 3, wherein: The calculation formula of the length of the magnetic core is: l case =l copper +2w1+4w2+2w core ; Where, l case is the length of the core, l copper is the width of the copper busbar, w1 is the distance between the copper busbar and the core shell, w2 is the distance between the core shell and the core body, w core is the width of the core body; The calculation formula of the width of the magnetic core is: w case =2w copper +2w1+4w2+2w core +w3; Where w case is the width of the core, w copper is the thickness of the copper busbar, w3 is the insulation distance between two copper busbars; The calculation formula of the height of the magnetic core is: Where h case is the height of the core, L is the common mode inductance, μ0 is the vacuum permeability, μ r is the relative magnetic permeability.

5. The common-mode inductor parameter design method according to claim 4, wherein: The step three specifically includes: For rectangular cores, the core volume is calculated based on the determined core length, width, and height. The volume of the magnetic core is organized into a standard format and a parameterized formula; The calculation formula of the volume of the magnetic core is: Where V core is the volume of the core, l case is the length of the core, w case is the width of the core, h case is the height of the core, l copper is the width of the copper busbar, w1 is the distance between the copper busbar and the core shell, w2 is the distance between the core shell and the core body, w core is the width of the core body, w3 is the insulation distance between the two copper bars, and w copper is the copper busbar thickness, L is the common mode inductance, μ0 is the vacuum permeability, μ r is the relative magnetic permeability; The above formula is organized into a standard format as follows: in:

6. The common-mode inductor parameter design method according to claim 5, wherein: The step 4 specifically includes: Based on the calculated core volume, the derivative of the core volume with respect to the core body width is derived to obtain the derivative of the volume with respect to the width; Set the derivative of volume with respect to width to zero and solve for the width w of the core body corresponding to the minimum volume. m , and verify the width obtained to make it meet the electromagnetic design and heat dissipation requirements; The calculation formula for the width of the magnetic core body corresponding to the minimum volume is: Where w m is the width of the core body corresponding to the minimum volume, 7. The common mode inductor parameter design method according to claim 6, characterized in that: The step five specifically includes: Calculate the busbar resistance based on the busbar resistivity, busbar cross-sectional area, copper busbar width and volume, and calculate the busbar loss based on the busbar current and busbar resistance; Calculate the busbar thermal resistance based on the thermal resistance from the busbar to the core shell, and multiply the busbar loss and the busbar thermal resistance to calculate the busbar temperature rise; Use the Steinmetz formula to calculate the core loss by combining material constants, operating frequency, and magnetic flux density, where the magnetic flux density is obtained based on the core inductance and current; Calculate the core thermal resistance based on the thermal resistance from the core body to the core shell, and calculate the core temperature rise by combining the core loss and the core thermal resistance. The busbar temperature rise and the core temperature rise are added together, and the total core shell temperature rise is obtained based on the core shell temperature rise caused by the busbar loss and the core loss.

8. The common-mode inductor parameter design method according to claim 7, wherein: The calculation formula of the busbar loss is: Where, P loss_copper is the busbar loss, I rms is the current in the DC busbar, R copper is the busbar resistance, ρ is the busbar resistivity, l copper is the width of the copper busbar, A copper is the busbar cross-sectional area; The calculation formula of the core loss is: P loss_core =k×f α ×B β ; Where, P loss_core is the core loss, k, α and β are material constants, B is the magnetic flux density, f is the operating frequency, l core is the effective magnetic path length of the common mode inductor, μ0 is the vacuum permeability, μ r is the relative magnetic permeability; The calculation formulas for the busbar temperature rise and the core temperature rise are: ΔT1=P loss_copper R cop_ca ; ΔT2=P loss_core R core_ca ; Where ΔT1 is the busbar temperature rise, ΔT2 is the core temperature rise, R cop_ca is the thermal resistance from busbar to core housing, R core_ca is the thermal resistance from the core body to the core shell; The calculation formula for the total temperature rise of the core shell is: ΔT total =ΔT1+ΔT2; Where, ΔT total is the total temperature rise of the core shell.

9. The common-mode inductor parameter design method according to claim 8, wherein: The step six specifically includes: Compare the calculated total temperature rise of the core shell with the maximum allowable temperature; If the total temperature rise of the core shell exceeds the maximum allowable temperature, increase the distance between the core body and the core shell; Recalculate the thermal resistance from the busbar to the core shell and the thermal resistance from the core body to the core shell based on the new distance between the core body and the core shell; Use the new thermal resistance and busbar loss to recalculate the busbar temperature rise, and use the new thermal resistance and core loss to recalculate the core temperature rise. Then, add the new busbar temperature rise and core temperature rise to get the new total temperature rise of the core shell. Compare the total temperature rise of the new core shell with the maximum allowable temperature. If the total temperature rise of the new core shell still exceeds the maximum allowable temperature, repeat steps 2 to 5 until the temperature rise meets the requirements.

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