A magnetic integrated three-phase emi filter

Abstract

This invention discloses a magnetically integrated three-phase EMI filter, comprising a toroidal magnetic core and a Y-shaped magnetic arm. The Y-shaped magnetic arm is placed inside a window of the toroidal magnetic core, with an air gap between the tip of each magnetic arm and the toroidal magnetic core. Three-phase windings are symmetrically wound on the toroidal magnetic core and the Y-shaped magnetic arm: the three-phase windings on the toroidal magnetic core are wound in the same way as a three-phase common-mode choke, and the three-phase windings on the Y-shaped magnetic arm are wound in the same way as a conventional EE-type three-phase differential-mode inductor. The output terminals of the windings on the toroidal magnetic core are connected to the input terminals of the in-phase windings on the Y-shaped magnetic arm. This filter allows for independent adjustment of the differential-mode and common-mode inductors. Under the same interference suppression performance, the magnetically integrated filter of this invention significantly reduces size and weight compared to conventional three-phase EMI filters. This invention has high research and application value for high-performance, high-reliability permanent magnet synchronous motor drive systems.

Description

Technical Field

[0001] This invention relates to an EMI filter, specifically to a magnetically integrated three-phase EMI filter suitable for the motor side of a three-phase permanent magnet synchronous motor drive system. Background Technology

[0002] Three-phase permanent magnet synchronous motor drive systems are widely used in new energy vehicles, wind power systems, and high-end equipment drives due to their advantages such as high power density and wide speed range. However, the use of PWM technology can lead to conducted EMI problems in the motor. How to effectively suppress conducted EMI in motors has become one of the main challenges.

[0003] Based on their propagation paths, conducted EMI can be divided into differential-mode interference and common-mode interference. Differential-mode interference propagates between power lines, increasing copper and iron losses in the motor; common-mode interference propagates between the power line and ground, damaging the motor bearings. When interference is excessive, it not only degrades system performance but may also affect the normal operation of nearby equipment. To control differential-mode and common-mode interference within specified limits, EMI filters are required.

[0004] EMI filters are divided into active filters and passive filters. Active filters consist of an auxiliary power supply, integrated operational amplifiers, resistors, and capacitors, which can reduce the size of the filter. They effectively reduce low-frequency interference by injecting compensation signals into the system. However, due to limitations such as integrated components, active filters can only suppress low-frequency interference and are difficult to handle high-power signals. In contrast, passive filters are widely used due to their simple design and high reliability.

[0005] Passive filters, composed of passive components such as inductors and capacitors, are typically large in size and weight. Extensive research has been conducted to reduce their size and improve performance. However, most of this research focuses on filters placed between the DC bus and the driver. Research on motor-side EMI filters is relatively limited. For permanent magnet synchronous motor drive systems, conventional EMI filters still rely on separate differential-mode and common-mode inductors, with significantly insufficient research on their magnetic integration optimization. In high-performance and high-reliability permanent magnet synchronous motor drive systems, DC-side and motor-side EMI filters typically coexist and are not interchangeable. Optimizing the size and weight of the motor-side EMI filter can further improve the system's compactness. Summary of the Invention

[0006] This invention provides a magnetically integrated three-phase EMI filter. It integrates a toroidal magnetic core with symmetrical Y-shaped magnetic arms to form an integrated magnetic core structure. Three-phase windings are then strategically wound around this integrated magnetic core to obtain the magnetically integrated EMI filter. This filter allows for independent adjustment of both differential-mode and common-mode inductances. While maintaining the same interference suppression performance, the magnetically integrated filter of this invention significantly reduces size and weight compared to traditional three-phase EMI filters.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A magnetically integrated three-phase EMI filter consists of two magnetic cores: a toroidal core and a Y-shaped magnetic arm. The Y-shaped magnetic arm is placed inside a window of the toroidal core, and an air gap is left between the top of each magnetic arm and the toroidal core. Three-phase windings are symmetrically wound on the toroidal core and the Y-shaped magnetic arm in an appropriate manner: the three-phase windings on the toroidal core are wound in the same way as the three-phase common-mode choke, and the three-phase windings on the Y-shaped magnetic arm are wound in the same way as the traditional EE-type three-phase differential-mode inductor; the output terminal of the winding on the toroidal core is connected to the input terminal of the in-phase winding on the Y-shaped magnetic arm.

[0009] In this invention, the magnetic integrated filter has multiple winding configurations based on the relative positions of the same phase windings on the two magnetic cores and the winding direction of the windings:

[0010] 1. Winding distribution I:

[0011] The A-phase winding on the Y-shaped magnetic arm is adjacent to the A and C-phase windings on the toroidal core; the B-phase winding on the Y-shaped magnetic arm is adjacent to the A and B-phase windings on the toroidal core; the C-phase winding on the Y-shaped magnetic arm is adjacent to the B and C-phase windings on the toroidal core. The winding method is as follows:

[0012] (1) The three-phase windings on the toroidal core and the Y-shaped magnetic arm are all wound counterclockwise;

[0013] (2) The three-phase windings on the toroidal core are wound counterclockwise, and the three-phase windings on the Y-shaped magnetic arm are wound clockwise;

[0014] (3) The three-phase windings on the toroidal core are wound clockwise, and the three-phase windings on the Y-shaped magnetic arm are wound counterclockwise;

[0015] (4) The three-phase windings on the toroidal core and the Y-shaped magnetic arm are all wound clockwise.

[0016] 2. Winding Distribution II:

[0017] The A-phase winding on the Y-shaped magnetic arm is adjacent to the B and C-phase windings on the toroidal core; the B-phase winding on the Y-shaped magnetic arm is adjacent to the A and C-phase windings on the toroidal core; the C-phase winding on the Y-shaped magnetic arm is adjacent to the A and B-phase windings on the toroidal core. The winding method is as follows:

[0018] (1) The three-phase windings on the toroidal core and the Y-shaped magnetic arm are all wound counterclockwise;

[0019] (2) The three-phase windings on the toroidal core are wound counterclockwise, and the three-phase windings on the Y-shaped magnetic arm are wound clockwise;

[0020] (3) The three-phase windings on the toroidal core are wound clockwise, and the three-phase windings on the Y-shaped magnetic arm are wound counterclockwise;

[0021] (4) The three-phase windings on the toroidal core and the Y-shaped magnetic arm are all wound clockwise.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] This invention integrates a common-mode inductor and a differential-mode inductor onto a single filter, significantly reducing the filter's size and weight. For high-performance, high-reliability permanent magnet synchronous motor drive systems, this invention has high research and application value. Attached Figure Description

[0024] Figure 1 The magnetic core structure for a magnetically integrated three-phase EMI filter;

[0025] Figure 2 This refers to two different winding distribution methods on the integrated magnetic core;

[0026] Figure 3 This is the circuit equivalent model of a magnetic integrated filter;

[0027] Figure 4 This refers to a winding and connection method under winding distribution I;

[0028] Figure 5 In order to be in Figure 4 The magnetomotive force generated by the windings on different magnetic cores under the shown conditions;

[0029] Figure 6 The magnetic equivalent circuit of the filter with winding distribution I;

[0030] Figure 7 The size of the filter;

[0031] Figure 8 The magnetic flux density distribution in the magnetic core of the two filters under set conditions;

[0032] Figure 9 The magnetic flux density distribution generated by the magnetic integrated filter under the excitation of differential-mode current and common-mode current, respectively;

[0033] Figure 10 These are the actual dimensions of the two filters;

[0034] Figure 11 These are the high-frequency impedance characteristics of the two filters. Detailed Implementation

[0035] The technical solution of the present invention will be further described below with reference to the accompanying drawings, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention that do not depart from the spirit and scope of the technical solution of the present invention should be covered within the protection scope of the present invention.

[0036] This invention provides a magnetically integrated three-phase EMI filter, which requires the integration of a toroidal magnetic core and a Y-shaped magnetic arm, and the proper winding of three-phase windings on the integrated magnetic core, as detailed below:

[0037] The magnetically integrated three-phase EMI filter consists of two magnetic cores: a toroidal core and a symmetrical Y-shaped magnetic arm. The Y-shaped magnetic arm is placed inside the window of the toroidal core, with a certain air gap between the tip of each magnetic arm and the toroidal core. The three-phase windings are symmetrically distributed on the toroidal core and the Y-shaped magnetic arm. For the outer toroidal core and the inner Y-shaped magnetic arm, the winding method of each phase winding is the same as that of a traditional three-phase common-mode choke and a three-phase differential-mode inductor, respectively. The windings of the same phase on both types of cores are interconnected, and there is a magnetic coupling relationship between the two cores. The toroidal core is mainly used to collect common-mode magnetic flux and provide a path for differential-mode magnetic flux, while the Y-shaped magnetic arm is mainly used to carry differential-mode magnetic flux, and the common-mode magnetic flux inside its core cancels each other out. The common-mode inductance is mainly provided by the winding on the toroidal core, while the differential-mode inductance is jointly provided by the windings on the toroidal core and the Y-shaped magnetic arm. The simultaneous provision of differential-mode and common-mode inductance is achieved through the decoupling and sharing of the magnetic circuit. Theoretically, this filter can suppress both differential-mode and common-mode interference simultaneously.

[0038] (1) Principle Analysis

[0039] Figure 1 The magnetic core structure of the magnetically integrated three-phase EMI filter is shown, with the windings distributed as follows: Figure 2 As shown, there are two distribution methods. In the diagram, the windings... ( ; () represent the toroidal core and the Y-shaped magnetic arm, respectively. The number of turns of each phase winding is denoted as follows: and ; and These represent the toroidal core and the Y-shaped magnetic arm, respectively. The input and output terminals of the phase winding. The circuit equivalent model of the magnetic integrated filter is as follows: Figure 3 As shown.

[0040] A. Winding Distribution I:

[0041] Figure 4This demonstrates a winding and connection method under distribution I. Each phase winding is wound counterclockwise on the magnetic core. and Connected. for Phase current, For filter The voltage of the phase winding. At this time, the magnetomotive force generated by the same-phase windings on different magnetic cores has the same direction, such as... Figure 5 As shown in the figure, and On the toroidal core and the Y-shaped magnetic arm respectively The magnetomotive force generated by the phase winding. The magnetic reluctance is one-third that of a toroidal core. For a single magnetic arm, the magnetic reluctance... The magnetic reluctance of each sub-arm and the toroidal core is measured in the air gap. (Magnetic reluctance of each sub-arm) We can obtain from (1):

[0042] (1)

[0043] In the formula, The effective length of the magnetic circuit. This is the effective cross-sectional area of ​​the magnetic circuit section. The relative permeability of the material corresponding to the magnetic circuit. ρ is the permeability of vacuum.

[0044] according to Figure 5 The magnetic equivalent circuit of the filter of the present invention is as follows: Figure 6 As shown in the figure, and On the toroidal core and the Y-shaped magnetic arm respectively The magnetic flux of the magnetic circuit where the phase winding is located. According to Figure 6 The magnetic circuit expression can be written as:

[0045] (2)

[0046] In the formula:

[0047] (3)

[0048] According to (2) and (3), the magnetic flux of each part in the magnetic circuit is:

[0049] (4)

[0050] (5)

[0051] Therefore, the winding is derived. Induced electromotive force on for:

[0052] (6)

[0053] By substituting (4) and (5) into (6), the self-inductance of the windings and the mutual inductance between the windings of the magnetic integrated filter of the present invention can be obtained.

[0054] Winding current This can be expressed as differential mode current ( ) and common-mode current ( The sum of:

[0055] (7)

[0056] Based on the phase relationship between the three phases, the following expression holds:

[0057] (8)

[0058] (9)

[0059] Substituting (8) into (4) and (5), we can obtain the differential mode component of the magnetic flux in the magnetic circuit:

[0060] (10)

[0061] (11)

[0062] In the formula, and On the toroidal core and the Y-shaped magnetic arm respectively The differential-mode component of the magnetic flux in the magnetic circuit where the phase winding is located;

[0063] By substituting (10) and (11) into (6), the derivation is obtained. Differential component :

[0064] (12)

[0065] Furthermore, the differential mode inductor is obtained. for:

[0066] (13)

[0067] for Differential-mode inductance of phase winding.

[0068] According to (13), the differential mode inductance of the three-phase windings of the magnetic integrated filter of the present invention is the same and is constant.

[0069] Substituting (9) into (4) and (5), we can obtain the common-mode components of the magnetic flux in the magnetic circuit:

[0070] (14)

[0071] (15)

[0072] In the formula, and On the toroidal core and the Y-shaped magnetic arm respectively The common-mode component of the magnetic flux in the magnetic circuit where the phase winding is located;

[0073] Similarly, it can be deduced that common mode component :

[0074] (16)

[0075] Furthermore, the common-mode inductance is obtained. for:

[0076] (17)

[0077] for Common-mode inductance of phase winding.

[0078] It can be seen that (17) is the same as the expression for the common mode inductance of a conventional three-phase common mode choke.

[0079] According to (13) and (17), the magnetic integrated filter of the present invention can make the three-phase windings symmetrical and simultaneously provide differential-mode inductance and common-mode inductance under distribution I. The differential-mode inductance value and the common-mode inductance value can be controlled by adjusting the number of turns of the magnetic core and the winding. The differential-mode inductance value is related to both types of magnetic cores and their windings. The differential-mode flux flows through the toroidal core and the Y-shaped magnetic arm, and there is differential-mode coupling between the two types of magnetic cores. The common-mode inductance value is mainly related to the toroidal core and its windings. Ideally, the common-mode flux exists only in the toroidal core, and there is common-mode decoupling between the two types of magnetic cores.

[0080] Under distribution I, the same analysis can be performed when the windings have other winding and connection methods. It can be seen that different winding and connection methods do not affect the common-mode inductance of the filter of this invention, but they do affect its differential-mode inductance value. Due to space limitations, the differential-mode inductance and common-mode inductance of the filter of this invention under different conditions will not be shown. To obtain better suppression performance with the same size and number of winding turns, the winding and connection method of the windings under distribution I should be the same as... Figure 4 Equivalent.

[0081] B. Analysis of winding distribution II:

[0082] This section provides a detailed analysis of the winding under distribution II and... Figure 4 Similar winding and connection methods apply to other cases. Following the same analysis process as in A, the differential mode component of the magnetic flux in this case is obtained:

[0083] (18)

[0084] (19)

[0085] Furthermore, the differential mode inductance is obtained as follows:

[0086] (20)

[0087] The common-mode component of the magnetic flux in the magnetic circuit is derived as follows:

[0088] (twenty one)

[0089] (twenty two)

[0090] Furthermore, the common-mode inductance is obtained as follows:

[0091] (twenty three)

[0092] It should be noted that, unlike winding distribution I, different winding and connection methods under distribution II will not affect the differential-mode inductance and common-mode inductance values ​​of the filter of this invention. Due to space limitations, further details will not be provided.

[0093] C. Comparison of the two winding distributions:

[0094] This section compares two winding distribution methods of the magnetic integrated filter of the present invention. It is assumed that the number of turns on the toroidal core and the Y-shaped magnetic arm are the same under both winding distributions. Comparing (13) and (20), it can be seen that winding distribution I can generate a larger differential-mode inductance. Comparing (17) and (23), it can be seen that the common-mode inductance generated under both winding distributions is the same. Therefore, it can be seen that the winding distribution method of the magnetic integrated filter of the present invention only affects the differential-mode inductance value. In order to obtain better differential-mode interference suppression performance with the same size and number of turns, the magnetic integrated filter of the present invention adopts winding distribution I. The present invention adopts... Figure 4 The winding and connection methods are shown.

[0095] (2) Result verification:

[0096] Based on the experimental platform, a conventional filter and the magnetically integrated filter of this invention were designed. The maximum differential-mode current in the winding is 4A, and the maximum common-mode current is 0.4A. The differential-mode inductance and common-mode inductance are designed to be 0.7mH and 3mH, respectively. For the toroidal core of both the conventional filter and the magnetically integrated filter of this invention, high-permeability MnZn-Ferrite J is selected. To avoid magnetic flux saturation, Powder Cores-DSF090, which has low permeability and high saturation magnetic flux density, is selected for the Y-shaped magnetic arm of the magnetically integrated filter. Figure 7 The dimensions of the designed filter are shown. For conventional filters, the number of turns per phase winding on an EE-type magnetic core is 45, and the number of turns per phase winding on a toroidal core is 18; for the filter of this invention, the number of turns per phase winding on a toroidal core is 21, and the number of turns per phase winding on a Y-type magnetic arm is 42. AWG 16 wire is selected.

[0097] Finite element simulation is performed to verify the correctness of the design. Figure 8 Two filters were demonstrated. =4A and The magnetic flux density distribution in the core at 0.4A. Based on... Figure 8 (a) It can be seen that the maximum magnetic flux density in the EE type magnetic core is approximately 0.29T, and the maximum magnetic flux density in the common-mode choke is approximately 0.23T, both of which are less than the maximum magnetic flux density limit. According to Figure 8 (b) It can be seen that the maximum magnetic flux density in the toroidal core and the Y-shaped magnetic arm of the magnetic integrated filter of the present invention is approximately 0.20T and 0.43T, respectively, both of which are less than the maximum magnetic flux density limit of the corresponding materials. The designed filter meets the magnetic flux density requirement. Figure 9 The magnetic flux density distributions of the magnetic integrated filter of the present invention under differential-mode and common-mode current excitation are illustrated. It is shown that the magnetic flux density generated by the differential-mode current is distributed in the toroidal core and the Y-shaped magnetic arm, while the magnetic flux density generated by the common-mode current is distributed only in the toroidal core. This indicates that the differential-mode interference suppression performance of the magnetic integrated filter of the present invention is determined by the filter as a whole, while the common-mode interference suppression performance is determined only by the toroidal core portion, verifying the correctness of the above analysis.

[0098] Figure 10 The actual dimensions of the two fabricated filters are shown. It is clearly evident that the magnetically integrated filter of this invention has superior dimensions. The conventional filter occupies a volume and weighs 267.33 cm³. 3 With a weight of 543.3g, the filter of this invention occupies a volume of 146.25cm³ and a weight of 146.25cm³. 3 Compared to traditional filters, the filter of this invention reduces volume and weight by 45.29% and 47.26%, respectively. Figure 11The high-frequency impedance characteristics of the two filters are shown. It can be seen that the impedance characteristics of the two filters are similar. Therefore, under the same interference suppression performance, the filter of this invention is a better choice to minimize the size and weight of the system.

Claims

1. A magnetically integrated three-phase EMI filter, characterized in that... The filter consists of two magnetic cores: a toroidal magnetic core and a Y-shaped magnetic arm. The Y-shaped magnetic arm is placed inside the window of the toroidal magnetic core, and an air gap is left between the top of each magnetic arm and the toroidal magnetic core. Three-phase windings are symmetrically wound on the toroidal magnetic core and the Y-shaped magnetic arm: the three-phase windings on the toroidal magnetic core are wound in the same way as the three-phase common-mode choke, and the three-phase windings on the Y-shaped magnetic arm are wound in the same way as the traditional EE-type three-phase differential-mode inductor; the output terminal of the winding on the toroidal magnetic core is connected to the input terminal of the in-phase winding on the Y-shaped magnetic arm.

2. The magnetically integrated three-phase EMI filter according to claim 1, characterized in that... The A-phase winding on the Y-shaped magnetic arm is adjacent to the A and C-phase windings on the toroidal magnetic core; the B-phase winding on the Y-shaped magnetic arm is adjacent to the A and B-phase windings on the toroidal magnetic core; and the C-phase winding on the Y-shaped magnetic arm is adjacent to the B and C-phase windings on the toroidal magnetic core.

3. The magnetically integrated three-phase EMI filter according to claim 2, characterized in that... The winding method is as follows: (1) The three-phase windings on the toroidal core and the Y-shaped magnetic arm are all wound counterclockwise; (2) The three-phase windings on the toroidal core are wound counterclockwise, and the three-phase windings on the Y-shaped magnetic arm are wound clockwise; (3) The three-phase windings on the toroidal core are wound clockwise, and the three-phase windings on the Y-shaped magnetic arm are wound counterclockwise; (4) The three-phase windings on the toroidal core and the Y-shaped magnetic arm are all wound clockwise.

4. The magnetically integrated three-phase EMI filter according to claim 3, characterized in that... When the toroidal magnetic core and the three-phase windings on the Y-shaped magnetic arm are all wound counterclockwise, the windings... These represent the toroidal core and the Y-shaped magnetic arm, respectively. The number of turns of each phase winding is denoted as follows: and , ; ; and Connected, for Phase current, For filter Voltage of the phase winding; and On the toroidal core and the Y-shaped magnetic arm respectively The magnetomotive force generated by the phase winding; The magnetic reluctance is one-third that of a toroidal core. For a single magnetic arm, the magnetic reluctance... The magnetic reluctance of the air gap between each sub-magnetic arm and the toroidal core; Each section of magnetic resistance From (1), we get: (1) In the formula, The effective length of the magnetic circuit. This is the effective cross-sectional area of ​​the magnetic circuit section. The relative permeability of the material corresponding to the magnetic circuit. ρ is the permeability of vacuum; and On the toroidal core and the Y-shaped magnetic arm respectively The magnetic flux of the magnetic circuit containing the phase winding is expressed by the following expression: (2) In the formula: (3) According to (2) and (3), the magnetic flux of each part in the magnetic circuit is: (4) (5) Therefore, the winding is derived. Induced electromotive force on for: (6) Winding current Represented as differential mode current With common mode current The sum of: (7) Based on the phase relationship between the three phases, the following expression holds: (8) (9) Substituting (8) into (4) and (5), we obtain the differential mode component of the magnetic flux in the magnetic circuit: (10) (11) In the formula, and On the toroidal core and the Y-shaped magnetic arm respectively The differential-mode component of the magnetic flux in the magnetic circuit where the phase winding is located; By substituting (10) and (11) into (6), the derivation is obtained. Differential component : (12) Furthermore, the differential mode inductor is obtained. for: (13) Substituting (9) into (4) and (5), we obtain the common-mode components of the magnetic flux in the magnetic circuit: (14) (15) In the formula, and On the toroidal core and the Y-shaped magnetic arm respectively The common-mode component of the magnetic flux in the magnetic circuit where the phase winding is located; Similarly, the derivation common mode component : (16) Furthermore, the common-mode inductance is obtained. for: (17)。 5. The magnetically integrated three-phase EMI filter according to claim 1, characterized in that... The A-phase winding on the Y-shaped magnetic arm is adjacent to the B and C-phase windings on the toroidal magnetic core; the B-phase winding on the Y-shaped magnetic arm is adjacent to the A and C-phase windings on the toroidal magnetic core; and the C-phase winding on the Y-shaped magnetic arm is adjacent to the A and B-phase windings on the toroidal magnetic core.

6. The magnetically integrated three-phase EMI filter according to claim 5, characterized in that... The winding method is as follows: (1) The three-phase windings on the toroidal core and the Y-shaped magnetic arm are all wound counterclockwise; (2) The three-phase windings on the toroidal core are wound counterclockwise, and the three-phase windings on the Y-shaped magnetic arm are wound clockwise; (3) The three-phase windings on the toroidal core are wound clockwise, and the three-phase windings on the Y-shaped magnetic arm are wound counterclockwise; (4) The three-phase windings on the toroidal core and the Y-shaped magnetic arm are all wound clockwise.

7. The magnetically integrated three-phase EMI filter according to claim 6, characterized in that... When the toroidal magnetic core and the three-phase windings on the Y-shaped magnetic arm are all wound counterclockwise, the windings... These represent the toroidal core and the Y-shaped magnetic arm, respectively. The number of turns of each phase winding is denoted as follows: and , ; ; The magnetic reluctance is one-third that of a toroidal core. For a single magnetic arm, the magnetic reluctance... The magnetic reluctance of the air gap between each sub-magnetic arm and the toroidal core; Differential mode component of magnetic flux in a magnetic circuit: (18) (19) In the formula, and On the toroidal core and the Y-shaped magnetic arm respectively The differential-mode component of the magnetic flux in the magnetic circuit where the phase winding is located; Furthermore, the differential mode inductor is obtained. for: (20) The common-mode component of the magnetic flux in the magnetic circuit is derived as follows: (21) (22) In the formula, and On the toroidal core and the Y-shaped magnetic arm respectively The common-mode component of the magnetic flux in the magnetic circuit where the phase winding is located; Furthermore, the common-mode inductance is obtained. for: (23)。

Images