Emi filter and inverter comprising an emi filter

Abstract

The invention relates to an EMI filter (1) comprising a choke (2). The choke (2) has a magnetic inner core (9) extending along a longitudinal center axis (LA), a magnetic outer core (10) and at least one conductor pair (11) comprising two electrical conductors (12a, 12b). In the choke (2), the inner core (9), the outer core (10) and the respective conductors (12a, 12b) extend along the longitudinal center axis (LA). The inner core (9) is arranged in the outer core (10) and the respective conductors (12a, 12b) are arranged between the inner core (9) and the outer core (10). The respective conductors (12a, 12b) are arranged spaced apart from each other in a circumferential direction and the inner core (9) and the outer core (10) are arranged spaced apart from each other in a radial direction. Thus, a gap (14) is formed between the inner ring (9), the outer ring (10) and the respective conductor (12a, 12b) adjacent in the circumferential direction, respectively. The invention further relates to an inverter comprising the EMI filter (1) according to the invention.

Description

Technical Field

[0001] This invention relates to an EMI filter including a choke coil. The invention also relates to an inverter for an electric motor that includes an EMI filter. Background Technology

[0002] Electronic devices typically do not interact electromagnetically with other nearby devices. However, in reality, inverters generate high electromagnetic interference (EMI) due to the rapid changes in voltage across parasitic capacitances and current across parasitic inductances as semiconductors switch within the inverter. To reduce EMI and increase the inverter's compatibility with other electronic devices, EMI filters can be switched within the inverter.

[0003] Electromagnetic interference is thus divided into common-mode (CM) and differential-mode (DM). EMI filters are therefore able to filter electromagnetic interference in both common-mode (CM) and differential-mode (DM). For this purpose, conventional EMI filters have common-mode chokes and differential-mode chokes combined with capacitors.

[0004] Chokes are sometimes implemented using magnetic cores arranged at the conductors of the inverter. Therefore, the magnetic cores can be E-shaped, C-shaped, U-shaped, and I-shaped. For example, chokes including this type of magnetic core are known from US 2009051478 A1 and EP 2357727 A1. Furthermore, two toroidal magnetic cores arranged inside each other are known from CN 111415810 A. Disadvantageously, this type of EMI filter or this type of choke has high space requirements, which is sometimes unusable. Furthermore, this type of choke cannot be used in high DC current applications. Summary of the Invention

[0005] Therefore, the object of this invention is to provide an improved or at least alternative embodiment for EMI filters and common-type inverters, which overcomes the described disadvantages. The EMI filter is particularly designed in a space-saving manner. The EMI filter is particularly suitable for high DC currents.

[0006] According to the invention, this objective is achieved by the subject matter of the independent claim. Advantageous embodiments are the subject matter of the dependent claims.

[0007] An EMI filter (EMI: Electromagnetic Interference) is provided for the inverter. The inverter is capable of supplying power to an electric motor. Therefore, the EMI filter has a choke ring, which includes a magnetic inner core, a magnetic outer core, and at least one conductor pair. The at least one conductor pair thus has a positive conductor and a negative conductor. In the choke ring, the inner core, the outer core, and each conductor of the at least one conductor pair extend along the longitudinal central axis of the choke ring. The inner core is thus arranged within the outer core, and each conductor of the at least one conductor pair is arranged between the inner core and the outer core. The corresponding adjacent conductors are thus arranged to be spaced apart from each other in the circumferential direction around the longitudinal central axis. Furthermore, the inner core and the outer core are arranged to be spaced apart from each other in the radial direction aligned with the longitudinal central axis. Thus, gaps are formed between the inner ring, the outer ring, and the corresponding conductors adjacent in the circumferential direction.

[0008] In the EMI filter according to the invention, each conductor of at least one conductor pair is surrounded by an outer core in the circumferential direction. The choke is thus suitable for filtering electromagnetic interference in the common mode. Therefore, according to the right-hand rule relative to the current direction of the common mode current in the conductors, the common mode magnetic flux is directed around the choke. Furthermore, in the EMI filter according to the invention, the inner core is arranged between the conductors of at least one conductor pair, or is surrounded by the conductors of at least one conductor pair in the circumferential direction. Thus, a magnetic circuit from the outer core to the inner core is completed in each gap. The magnetic flux within the gap can be added in this way. The choke is thus suitable for filtering electromagnetic interference in the differential mode.

[0009] Advantageously, the conductors of at least one conductor pair can be arranged around the longitudinal central axis of the choke and uniformly distributed around the longitudinal central axis. Advantageously, the conductors of at least one conductor pair can pass through only once between the inner and outer cores. In other words, the conductors of at least one conductor pair cannot be wound around either the inner or outer core. In other words, the number of turns of the conductors of at least one conductor pair around the inner and outer cores is equal to one. Advantageously, the conductors of at least one conductor pair can be either rigid or not very flexible. Advantageously, the conductors of at least one conductor pair can be plate-shaped or flat busbars. Advantageously, the conductors of at least one conductor pair can have a substantially rectangular cross-section. Advantageously, the cross-section of the conductors of at least one conductor pair can be adapted to the required current intensity.

[0010] Advantageously, the gap is dielectric and / or diamagnetic. Advantageously, the gap can be an air gap. Advantageously, the width of the gap in the radial direction can be designed such that electromagnetic interference (EMI) in differential mode is filtered at the maximum filtering level. Therefore, EMI in common mode is filtered at a filtering level suitable for the maximum filtering level of differential mode. The width of the gap is a function of the properties of the magnetic materials of the outer and inner cores and the DC current level. In practice, the width of the gap is also affected by the manufacturing tolerances and positioning tolerances of the outer and inner cores.

[0011] In the EMI filter according to the invention, the choke is advantageously capable of filtering electromagnetic interference under both common-mode and differential-mode conditions. The choke therefore has no windings, allowing the choke and the EMI filter to be constructed in a simplified and compact manner. Furthermore, since the individual conductors of at least one conductor pair do not need to be flexible, the cross-sections of the individual conductors of at least one conductor pair can also be freely adapted. Therefore, the choke can be adapted to the required current intensity in a simplified manner.

[0012] In an advantageous embodiment of the EMI filter, the inner core can be specified as a solid or hollow cylinder, or a straight, solid or hollow prism comprising a regular polygonal base. The outer core is a hollow cylinder, or a straight hollow prism comprising a regular polygonal base. Furthermore, the inner and outer cores are arranged coaxially within each other, and at least one conductor pair is arranged between the outer and inner cores to be uniformly distributed about the longitudinal central axis of the choke. In this advantageous embodiment, the choke of the EMI filter is formed as rotationally symmetrical about its longitudinal axis. Current can therefore be symmetrically distributed within the choke, and the electromagnetic characteristics of both the choke and the EMI filter can be improved.

[0013] Advantageously, the gap can be an air gap. Advantageously, the conductors of at least one conductor pair can be formed by means of a plate-shaped busbar. Advantageously, it can be specified that the inner core and outer core are formed of the same material or different materials. Advantageously, the material can have high permeability to improve the filtering of electromagnetic interference in both common mode and differential mode. The properties of the material affect the saturation of the inner and outer cores, and therefore also affect the optimal width of the gap in the choke. As mentioned above, the width of the gap can be designed to achieve the maximum filtering level of electromagnetic interference in both common mode and differential mode.

[0014] Advantageously, the EMI filter can be specified to have at least one X capacitor and at least two Y capacitors. The at least one X capacitor is thus interconnected with the conductors of at least one conductor pair to form a differential-mode filter circuit. The at least two Y capacitors are each connected between the respective conductors of the at least one conductor pair and the inverter base to form common-mode and differential-mode filter circuits. Advantageously, the base can be formed of a metal housing. Advantageously, the Y capacitors can be connected to the base via a ground plane. Advantageously, the at least two Y capacitors and at least one X capacitor, along with the conductors, can be material-bonded to each other, preferably welded.

[0015] Advantageously, the choke of the EMI filter can be specified to have at least two conductor pairs, and therefore at least two positive conductors and at least two negative conductors. The positive and negative conductors then alternate in the circumferential direction. Advantageously, current can be distributed to the positive and negative conductors of the respective conductor pairs. Therefore, high current can flow through the choke. Furthermore, the current can be symmetrically distributed within the choke, and in this advantageous embodiment, the electromagnetic characteristics of both the choke and the EMI filter can be improved. Advantageously, the choke can have exactly two or exactly three conductor pairs. However, it is also conceivable that the choke has more than three conductor pairs. However, it goes without saying that the number of conductor pairs in the choke can be limited by the desired filtering characteristics of the EMI filter, the available space between the outer and inner cores, and the minimum required size of the circumferential gap. Furthermore, the number of conductor pairs in the choke is limited by the inverter design.

[0016] Advantageously, it can be specified that at least one conductor pair is accommodated in at least some regions of the outer recess of the outer core and / or in at least some regions of the inner recess of the inner core in the radial direction. Therefore, by adjusting the depth of the outer recess in the radial direction, the width of the gap in the radial direction can be adjusted independently of the width of the respective conductor.

[0017] Advantageously, the EMI filter can be specified to have a dielectric housing, and the choke coil is housed within the dielectric housing of the EMI filter in some areas. Advantageously, in some areas, additional components of the EMI filter can be housed within an insulating housing of the EMI filter. The housing can advantageously be made of plastic. Advantageously, the housing can be formed during a casting process. Advantageously, the choke coil can be cast into the housing. Advantageously, at least one conductor pair of the choke coil can be cast into the housing. Advantageously, additional components of the EMI filter can be cast into the housing.

[0018] The present invention also relates to an inverter for an electric motor. Therefore, the inverter includes a capacitor plate containing at least one capacitor. In the inverter, the at least one capacitor is interconnected between at least one pair of conductors. Needless to say, the inverter can also include additional components. In particular, the inverter can include at least one transistor plate containing at least two transistors. The capacitor plate and the corresponding transistor plate are then electrically interconnected. According to the invention, the inverter has the aforementioned EMI filter. The EMI filter thus electrically switches with the inverter's capacitor plate. Advantageously, the EMI filter can have a DC battery terminal for interconnecting the inverter with a DC power supply. The DC battery terminal is then electrically interconnected with the inverter's capacitor plate.

[0019] Relative to its longitudinal central axis, the inverter can advantageously have an open longitudinal end facing the motor and a closed longitudinal end away from the motor. Needless to say, this definition refers to an inverter properly arranged on an electric motor. Advantageously, it can be specified that an EMI filter is fixed to the closed longitudinal end of the inverter away from the motor.

[0020] Advantageously, it is possible to specify that the conductor material of the EMI filter is bonded, preferably soldered, to a corresponding copper plate on the capacitor plate of the inverter. Advantageously, the EMI filter can be bonded, preferably soldered, to the capacitor plate from the open longitudinal end of the inverter facing the motor. Therefore, the assembly of the EMI filter to the inverter can be significantly simplified.

[0021] Advantageously, the EMI filter can be securely connected in a form-fit and / or force-fit manner. Advantageously, the EMI filter can be threaded onto the inverter. Advantageously, the longitudinal center axis of the choke can be aligned parallel to or coincide with the longitudinal center axis of the inverter.

[0022] Other important features and advantages of the invention are apparent from the dependent claims, the drawings, and the corresponding description based on the drawings.

[0023] It goes without saying that, without departing from the scope of the invention, the above features and the features described below can be used not only in their respective specific combinations, but also in other combinations or individually. Attached Figure Description

[0024] Preferred exemplary embodiments of the present invention are shown in the accompanying drawings and will be described in more detail in the following description, in which the same reference numerals denote the same or similar or functionally identical parts.

[0025] Indicatively:

[0026] Figure 1 and Figure 2A view of an EMI filter, shown without a housing, according to the present invention is illustrated.

[0027] Figure 3 An exploded view of an EMI filter according to the present invention, shown as without a housing, is illustrated.

[0028] Figure 4 A view of an EMI filter with a housing according to the present invention is shown;

[0029] Figure 5 A view of the choke coil in an EMI filter according to the present invention is shown;

[0030] Figure 6 An EMI filter according to the present invention is shown. Figure 5 The equivalent circuit diagram of the choke shown is shown.

[0031] Figure 7 It shows Figure 5 A view of the simulated magnetic path of the choke shown;

[0032] Figures 8 to 11 It shows the characterization Figure 5 and Figure 7 The diagram shows the choke coil. Detailed Implementation

[0033] Figure 1 A side view of an EMI filter 1, shown without a housing, according to the present invention is shown.

[0034] Figure 2 A view of the EMI filter 1 according to the invention, shown from the bottom, is presented as without a housing.

[0035] Figure 3 An exploded view of the various components of the EMI filter 1 according to the present invention is shown. The EMI filter thus has a choke 2, a plurality of X capacitors 3, a plurality of Y capacitors 4, an E-type choke 5, a conductive ground plane 6, a conductive positive battery terminal 7a, and a conductive negative battery terminal 7b. The choke 2 thus includes a magnetic inner core 9, a magnetic outer core 10, and three conductor pairs 11, each having a conductive positive conductor 12a and a conductive negative conductor 12b, respectively.

[0036] Each positive conductor 12a and each positive battery terminal 7a is thus realized by means of a positive electrode element 13a, while each negative conductor 12b and each negative battery terminal 7b is thus realized by means of a negative electrode element 13b. The positive electrode element 13a and the negative electrode element 13b are thus formed to be conductive, integral, plate-shaped, and folded. Each positive conductor 12a and each positive battery terminal 7a is therefore conductive and electrically connected to each other. Each negative conductor 12b and each negative battery terminal 7b is therefore conductive and electrically connected to each other. Thus, the positive conductor 12a and the negative conductor 12b are respectively formed as flat or plate-shaped, or respectively formed as plate-shaped busbars.

[0037] In the choke 2, the inner core 9, the outer core 10, the positive conductors 12a, and the negative conductors 12b extend along the longitudinal central axis LA of the choke 2. Conductors 12a and 12b, the inner core 9, and the outer core 10 are electrically insulated from each other. Electrical insulation can be achieved with air. Alternatively, conductors 12a and 12b, the inner core 9, and the outer core 10a can be molded in a plastic housing to provide electrical insulation. The positive conductors 12a and the negative conductors 12b are thus arranged radially aligned with respect to the longitudinal central axis LA between the inner core 9 and the outer core 10. Furthermore, the positive conductors 12a and the negative conductors 12b are arranged to alternate and be evenly distributed in the circumferential direction around the longitudinal central axis LA. Additionally, corresponding adjacent conductors 12a and 12b are arranged to be spaced apart from each other in the circumferential direction, such that gaps 14 are formed between the inner core 9, the outer core 10, and the respective conductors 12a and 12b, which are adjacent in the circumferential direction. The following will be based on... Figures 7 to 11 The advantageous characteristics of choke coil 2 will be described in more detail.

[0038] Choke 2, X capacitor 3, and Y capacitor 4 are electrically interconnected to form filter circuit 8. Furthermore, ground plane 6, positive battery terminal 7a, and negative battery terminal 7b are electrically interconnected with filter circuit 8. Each X capacitor 3 is interconnected with corresponding conductors 12a and 12b of the corresponding conductor pair 11 of choke 2, and each Y capacitor 4 is connected via ground plane 6 between the corresponding conductors 12a and 12b of the corresponding conductor pair 11 and the base (here, the metal housing) of inverter 1. Figure 3 As can be seen particularly clearly, the E-type choke 5 has two E-shaped magnetic cores 15 arranged around the positive electrode element 13a and the negative electrode element 13b. The E-type choke 5 or magnetic cores 15 are thus arranged between the choke 2 or the positive conductor 12a and the negative conductor 12b and the positive battery terminal 7a and the negative battery terminal 7b, respectively.

[0039] Figure 4 A view of an EMI filter 1 according to the present invention is shown. Figure 4An EMI filter 1 with a housing 16 is shown, which at least in some areas surrounds or encloses the components of the EMI filter 1. The housing 16 is dielectric and can be made of plastic. In particular, the housing 16 can be formed during a casting process, in which the components of the EMI filter 1 can then be cast into the housing.

[0040] refer to Figures 1 to 4 An EMI filter 1 is provided for the inverter of the electric motor. If the EMI filter is interconnected with the inverter, the corresponding conductors 12a and 12b are conductively connected to the capacitor plate of the inverter. The positive battery terminal 7a and the negative battery terminal 7b then form the DC battery terminals of the inverter.

[0041] Figure 5 A view of the choke coil 2 in the EMI filter 1 according to the invention is shown. As can be seen particularly clearly here, the positive conductor 12a and the negative conductor 12b are arranged to alternate and be uniformly distributed in the circumferential direction. The inner core 9 and the outer core 10 are each shown as straight hollow prisms with regular hexagonal bases. A corresponding conductor of the six conductors 12a or 12b is respectively assigned to one of the six sides / sides of the corresponding prism. The corresponding conductor 12a or 12b is thus arranged in the outer recess 17 of the outer core 10.

[0042] In choke 2, each conductor 12a and 12b is surrounded or enclosed by the outer core 10 in the circumferential direction, thus choke 2 is suitable for filtering common-mode electromagnetic interference. Furthermore, the inner core 9 is surrounded or enclosed by corresponding conductors 12a and 12b in the circumferential direction, making choke 2 suitable for filtering differential-mode electromagnetic interference. In addition, choke 2 has high symmetry, and the current can be symmetrically distributed within choke 2. Therefore, it can filter electromagnetic interference particularly effectively.

[0043] The following will be based on Figures 6 to 11 The characteristics of choke 2 are described in more detail. For this purpose, choke 2 is shown in a model. In this model, the positive conductor 12a and the negative conductor 12b are numbered consecutively from 1 to 6 in the circumferential direction. The corresponding three positive conductors 12a of choke 2 are thus identified by the numbers 1, 3, and 5. The corresponding three negative conductors 12b of choke 2 are thus identified by the numbers 2, 4, and 6.

[0044] Magnetic coupling between individual conductors 12a and 12b is generated in the choke 2 by means of an outer core 10, which surrounds or encloses conductors 12a and 12b on the outside, respectively. Therefore, an inductance is generated between individual conductors 12a and 12b.

[0045] The resulting common-mode inductances in the matrix can be combined as follows:

[0046]

[0047] The resulting differential-mode inductances in the matrix can be combined as follows:

[0048]

[0049] In both cases, L_CM / DM_xx therefore represents the self-inductance of the corresponding conductor 12a or 12b, and L_CM / DM_yx represents the mutual inductance between the corresponding conductors 12a or 12b. If x is not equal to y, then L_CM / DM_xy = L_CM / DM_yx. If we also consider the resistance R_xx of the corresponding conductors 12a and 12b, we get Figure 6 The equivalent circuit diagram is shown.

[0050] therefore, Figure 6 The equivalent circuit diagram of choke 2 according to the above model is shown. The three upper branches thus represent the corresponding positive conductor 12a of choke 2. The three lower branches thus represent the corresponding negative conductor 12b of choke 2.

[0051] In the case of the corresponding positive conductors 12a of choke coil 2, numbered 1, 3 and 5

[0052] I_DC – Identifies the DC current in choke coil 2 in the equivalent circuit diagram;

[0053] I_DC / 3 – Identifies a portion of the DC current in the corresponding positive conductor 12a in the equivalent circuit diagram;

[0054] i_DM11, i_DM33, i_DM55 – Identify the differential-mode DC current in the corresponding positive conductor 12a in the equivalent circuit diagram;

[0055] i_CM11, i_CM33, i_CM55 – Identify the common-mode DC current in the corresponding positive conductor 12a in the equivalent circuit diagram;

[0056] R_11, R_33, R_55 – Identify the resistance of the corresponding positive conductor 12a in the equivalent circuit diagram;

[0057] L_DM11, L_DM33, L_DM55 – Identify the differential-mode self-inductance of the corresponding positive conductor 12a in the equivalent circuit diagram;

[0058] L_CM11, L_CM33, L_CM55 – Identify the common-mode self-inductance of the corresponding positive conductor 12a in the equivalent circuit diagram.

[0059] In the case of the corresponding negative conductors 12b of choke coil 2 numbered 2, 4 and 6,

[0060] I_DC – Identifies the DC current in choke coil 2 in the equivalent circuit diagram;

[0061] I_DC / 3 – Identifies a portion of the DC current in the corresponding negative conductor 12b in the equivalent circuit diagram;

[0062] i_DM22, i_DM44, i_DM66 – Identify the differential-mode DC current in the corresponding negative conductor 12b in the equivalent circuit diagram;

[0063] i_CM22, i_CM44, i_CM66 – Identify the differential-mode DC current in the corresponding negative conductor 12b in the equivalent circuit diagram;

[0064] R_22, R_44, R_66 – Identify the resistance of the corresponding negative conductor 12b in the equivalent circuit diagram;

[0065] L_DM22, L_DM44, L_DM66 – Identify the differential-mode self-inductance of the corresponding negative conductor 12b in the equivalent circuit diagram;

[0066] L_CM22, L_CM44, L_CM66 – Identify the common-mode self-inductance of the corresponding negative conductor 12b in the equivalent circuit diagram.

[0067] Resistors R_11, R_33, R_55, R_22, R_44, and R_66 are combined to form a block RES_block. Differential-mode self-inductances L_DM11, L_DM33, L_DM55, L_DM22, L_DM44, and L_DM66 are combined to form a block LDM_block. (LM) / 2 is applied to this block LDM_block. Here, L refers to the self-inductance of each conductor 12a, 12b or the diagonal element (elements L_DM11, L_DM33, L_DM55, L_DM22, L_DM44, L_DM66) in the matrix [L_DM], and M refers to the mutual inductance between two conductors 12a, 12b or the off-diagonal element (L_xy) in the matrix [L_DM], where x is not equal to y. Common-mode self-inductances L_CM11, L_CM33, L_CM55, L_CM22, L_CM44, and L_CM66 are combined to form a block LCM_block. (L+M) / 2 is applied to this block LCM_block. Here, L refers to the self-inductance of each conductor 12a, 12b or diagonal element (elements L_CM11, L_CM33, L_CM55, L_CM22, L_CM44, L_CM66) in the matrix [L_CM], and M refers to the mutual inductance between two conductors 12a, 12b or off-diagonal elements (elements Lxy) in the matrix [L_CM], where x is not equal to y.

[0068] Figure 7 A view showing the choke 2 with simulated magnetic path within it is presented. From Figure 7As can be seen, in each case, the common-mode magnetic flux in the inner core 9 and the outer core 10 tends to flow in the same direction. The differential-mode magnetic flux tends to bridge the gap 14.

[0069] Figure 8 A schematic diagram characterizing the choke coil 2 is shown. The diagram illustrates the differential-mode inductances L_DM14, L_DM12, and L_DM16 between one of the positive conductors 12a and each of the three negative conductors 12b. Differential-mode inductance is defined as the inductance between two conductors 12a and 12b carrying currents in opposite directions. Therefore, only inductances L_DM14, L_DM12, and L_DM16 are relevant to differential-mode filtering. Thus, the differential-mode inductance, expressed in nH, relative to the gap width (in mm), is depicted when the DC current I_DC equals 1100A. Consequently, the maximum differential-mode inductance L_DM14 is generated between the conductors 12a and 12b, which are opposite each other and at the maximum distance.

[0070] Figure 9 Another schematic diagram is shown to characterize choke 2. This diagram illustrates the common-mode inductances L_CM12 and L_CM16 between one of the positive conductors 12a and the adjacent negative conductor 12b. Due to the symmetry of the choke, the following equations apply:

[0071] L_DM14=L_DM25=L_DM36

[0072] L_DM41=L_DM14

[0073] L_DM52=L_DM25

[0074] L_DM63 = L_DM36.

[0075] Therefore, the common-mode inductance, expressed in μH, is depicted as a function of the width of gap 14, expressed in mm, when the DC current I_DC equals 1100A. The common-mode inductances L_CM12 and L_CM16 are thus identical for both pairs of conductors 12a and 12b.

[0076] Figure 10 Another schematic diagram for characterizing the choke coil 2 is shown. This diagram illustrates the differential-mode inductances L_DM12, L_DM14, and L_DM16 between one of the positive conductors 12a and each of the three negative conductors 12b. This depicts the common-mode inductance, expressed in nH, as a function of the DC current I_DC, expressed in A, with the width of the gap 14 equal to 1050 μm. The differential-mode inductances L_DM12, L_DM14, and L_DM16 thus show a fixed relationship with the DC current I_DC until the inner core 9 and outer core 10 saturate.

[0077] Figure 11Another schematic diagram for characterizing the choke coil 2 is shown. This diagram illustrates the common-mode inductance L_CM14 between one of the positive conductors 12a and the negative conductor 12b positioned at maximum distance from each other. Thus, the common-mode inductance, expressed in μH, is depicted as a function of the DC current I_DC, expressed in A, with the width of the gap 14 being equal to 1050 μm. The common-mode inductance L_CM14 decreases with increasing DC current I_DC. This is because the magnetic materials of the inner core 9 and the outer core 10 approach magnetic saturation, and the permeability of the materials decreases.

Claims

1. An EMI filter (1) for an inverter, comprising a choke coil (2), - wherein, The choke (2) has a magnetic inner core (9), a magnetic outer core (10), and at least one conductor pair (11). - in, The at least one conductor pair (11) has a positive conductor (12a) and a negative conductor (12b) respectively. - In the choke (2), the conductors (12a, 12b) of the magnetic inner core (9), the magnetic outer core (10), and the at least one conductor pair (11) extend along the longitudinal central axis (LA) of the choke (2). - Wherein, the magnetic inner core (9) is arranged in the magnetic outer core (10), and the conductors (12a, 12b) of the at least one conductor pair (11) are arranged between the magnetic inner core (9) and the magnetic outer core (10). - wherein the conductors (12a, 12b) are arranged to be spaced apart from each other in a circumferential direction around the longitudinal central axis (LA), and the magnetic inner core (9) and the magnetic outer core (10) are arranged to be spaced apart from each other in a radial direction aligned with the longitudinal central axis (LA). -In this configuration, gaps (14) are formed between the magnetic inner core (9), the magnetic outer core (10), and the corresponding conductors (12a, 12b) adjacent in the circumferential direction. - Wherein, the choke (2) has at least two conductor pairs (11), and therefore has at least two positive conductors (12a) and at least two negative conductors (12b), - In this configuration, the positive conductors (12a) and the negative conductors (12b) alternate in the circumferential direction. - wherein the at least one conductor pair (11) is formed by means of a plate-shaped busbar, and - wherein, in the at least two conductor pairs (11), each conductor (12a, 12b) is surrounded or enclosed by the magnetic outer core (10) on the outside in the circumferential direction, and the magnetic inner core (9) is surrounded or enclosed by the corresponding conductor (12a, 12b) on the outside in the circumferential direction.

2. The EMI filter according to claim 1, Its features - The magnetic core (9) is a complete or hollow cylinder, or a straight, complete or hollow prism, the prism including a regular polygonal base, and - The magnetic outer core (10) is a hollow cylinder or a straight hollow prism including a regular polygonal base. - The magnetic inner core (9) and the magnetic outer core (10) are coaxially arranged inside each other, and - The individual conductors (12a, 12b) of the conductor pair (11) are arranged around the longitudinal central axis (LA) of the choke (2) and are evenly distributed around the longitudinal central axis.

3. The EMI filter according to claim 1 or 2, Its features - The magnetic inner core (9) and the magnetic outer core (10) are formed of the same material or different materials, and / or - The gap (14) is an air gap.

4. The EMI filter according to claim 1 or 2, Its features - The EMI filter (1) has at least one X capacitor (3) and at least two Y capacitors (4), and - The at least one X capacitor (3) is interconnected with the corresponding conductors (12a, 12b) of the at least one conductor pair (11) of the choke coil (2) to form a differential mode filter circuit (8), and - The at least two Y capacitors (4) are each connected between the conductors (12a, 12b) of the at least one conductor pair (11) and the base of the inverter (1) to form a common-mode and differential-mode filter circuit (8).

5. The EMI filter according to claim 1 or 2, Its features The individual conductors (12a, 12b) of the at least one conductor pair (11) are accommodated in the outer recess (17) of the magnetic outer core (10) and / or in the inner recess of the magnetic inner core (9) in at least some regions in the radial direction.

6. The EMI filter according to claim 1 or 2, Its features The EMI filter (1) has a dielectric housing (16), and the choke (2) is housed in the dielectric housing (16) of the EMI filter (1) in some areas.

7. An inverter for an electric motor, wherein, The inverter includes a capacitor plate containing at least one capacitor. Its features - The inverter has an EMI filter (1) according to any one of the preceding claims, and - The EMI filter (1) is electrically switched with the capacitor board of the inverter.

8. The inverter according to claim 7, Its features The EMI filter (1) is fixed to the longitudinal end of the inverter away from the motor.

9. The inverter according to claim 7 or 8, Its features The conductors (12a, 12b) of at least one conductor pair (11) of the choke coil (2) of the EMI filter (1) are bonded to the corresponding copper plates of the capacitor plate of the inverter.

10. The inverter according to claim 9, Its features The conductors (12a, 12b) of at least one conductor pair (11) of the choke coil (2) of the EMI filter (1) are welded to the corresponding copper plates of the capacitor plate of the inverter.

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