Common mode noise filter

Abstract

The parasitic inductance of the Y capacitor used in the common-mode noise filter, which suppresses common-mode noise current flowing to the power input side of the power converter, prevents sufficient removal of high-frequency conducted noise. [Solution] A structure was adopted in which a Y-con busbar simultaneously passes through a cylindrical ferrite core through which a portion of the busbar connected to the input power supply passes.

Description

Technical Field

[0001] The disclosed technology relates to a common-mode noise filter that suppresses high-frequency common-mode noise current on the power supply input side, which is suitable for application to a power converter such as an inverter device that converts DC power into AC power to drive a motor or a converter device.

Background Art

[0002] As an example, an in-vehicle inverter inputs a high-voltage DC power supply of several hundred volts, generates a three-phase alternating current by a high-frequency switching circuit with a carrier frequency of about 10 KHz, and supplies power to a driving motor to run.

[0003] The high-frequency switching circuit consists of three sets of so-called half-bridge circuits, and outputs a rectangular wave generated by alternately and rapidly switching between the positive and negative electrodes of the high-voltage power supply to each of the three phases and supplies it to the motor windings.

[0004] The high-frequency switching element is generally mounted on a radiator with a large semiconductor as a known power module and then mounted on a water-cooled cooler. The radiator and the cooler are made of a conductive metal such as copper and are electrically connected to an inverter housing formed by aluminum die-casting. At the same time, the inverter housing is electrically connected to the vehicle body.

[0005] There is a predetermined first capacitance between the output terminal of the half-bridge constituting the power module and the radiator.

[0006] The three-phase rectangular wave output voltage is connected to the motor windings. There is a predetermined second capacitance between the motor windings and the metal motor housing, and the motor housing is electrically connected to the vehicle body.

[0007] Although the high-voltage DC power supply is electrically insulated from the vehicle body, there is a relatively large third capacitance between the secondary battery constituting the high-voltage DC power supply and the vehicle body.

[0008] As described above, when the inverter is operated, a first high-frequency current, which is the derivative of the output voltage of the high-frequency switching circuit, flows from the high-frequency switching circuit to the first path formed by the first capacitance, heat sink, cooler, inverter housing, vehicle body, third capacitance, secondary battery, and inverter.

[0009] As described above, when the inverter is activated, a second high-frequency current, which is the derivative of the output voltage of the high-frequency switching circuit, flows from the high-frequency switching circuit to the second path formed by the motor winding, second capacitance, motor housing, vehicle body, third capacitance, secondary battery, and inverter.

[0010] The sum of the first and second high-frequency currents flows as a common-mode noise current of the same phase and amplitude in the positive and negative terminal wiring of the high-voltage wiring connecting the secondary battery and the inverter. It is known that this current generates a radiated electromagnetic field, which adversely affects wireless communication equipment such as in-car radios.

[0011] When the first and second high-frequency currents flow, the ungrounded terminal voltages of the first and second capacitances fluctuate, and these voltage fluctuations are generated as common-mode noise voltages of the same amplitude and phase on the positive and negative terminals of the high-voltage power supply via the semiconductor elements of the power module.

[0012] Inverters need to suppress the common-mode noise current, and according to Patent Document 1, a technique is disclosed in which a grounded capacitor 9 is connected between the inductor 7 and the inverter circuit 5 to prevent the first and second high-frequency currents from flowing to the power input side. [Prior art documents] [Patent Documents]

[0013] [Patent Document 1] Japanese Patent Publication No. 2015-12650 [Overview of the project] [Problems that the invention aims to solve]

[0014] The capacitor 9 in Patent Document 1 is generally called a Y-capacitor. For example, the high-voltage wiring inside the inverter is formed with busbars made of low-resistance copper plates to handle large currents, and the lead wires of the Y-capacitor are also made of similar busbars.

[0015] Although the leads of a Y-capacitor are designed to minimize their resistance, parasitic inductance due to physical dimensions is unavoidable.

[0016] Figure 5 shows the electrical configuration of a conventional Y-capacitor. Because the parasitic inductance is present in the Y-capacitor, when the first and second high-frequency currents, shown by the thick gray lines in the figure, flow through it, a potential difference is generated across the parasitic inductance. As a result, the midpoint a of the Y-capacitor does not become ground potential, but rather a potential that fluctuates with high frequency, i.e., a common-mode noise voltage.

[0017] The inductor 7 in Patent Document 1 corresponds to the ferrite core in Figure 5, and the high-frequency potential fluctuation at point a becomes a common-mode current on the high-voltage wiring via the path of the thin gray line in the figure, which passes through each busbar, high-voltage wiring, high-voltage power supply, and stray capacitance Cb, and returns to the parasitic inductance via ground. Thus, because parasitic inductance exists in the Y capacitor, there are limitations to the common-mode noise current suppression of inverters using conventional technology.

[0018] Although the above issues were explained using inverters as an example, the basic configuration is the same for various power converters such as DC-DC converters, and engineers in this field will readily realize that similar issues exist. [Means for solving the problem]

[0019] In view of the above issues, the common-mode noise filter of claim 1 comprises a cylindrical ferrite core positioned so as to pass through a portion of the P (positive) busbar and N (negative) busbar connecting the power input section of the power converter and the power conversion means, a Y capacitor consisting of first and second capacitors connected in series between the P busbar and the N busbar on the power conversion means side of the ferrite core opening, and a Y-con busbar connecting the intermediate connection portion of the Y capacitor to ground, wherein the Y-con busbar is configured to pass through the cylindrical ferrite core together with the P busbar and the N busbar.

[0020] The common-mode noise filter of claim 2 includes a cylindrical ferrite core positioned so that a portion of the P busbar and N busbar connecting the power input section of the power converter and the power conversion means passes through it, and on the power conversion means side of the opening of the ferrite core, a first Y-con busbar connecting the P busbar and ground and a second Y-con busbar connecting the N busbar and ground are provided, a first capacitor is connected to a portion of the first Y-con busbar that has been divided in the middle, and a second capacitor is connected to a portion of the second Y-con busbar that has been divided in the middle, and the first Y-con busbar and the second Y-con busbar are configured to pass through the ferrite core together with the P busbar and N busbar.

[0021] The common-mode noise filter according to claim 3 comprises a cylindrical ferrite core positioned so that a portion of the U (U-phase) busbar, V (V-phase) busbar, and W (W-phase) busbar, which connect the power input section of a power converter that receives a three-phase power supply to a power conversion means, passes through it; a Y capacitor consisting of a first capacitor with one end connected to the U busbar, a second capacitor with one end connected to the V busbar, and a third capacitor with one end connected to the W busbar, located on the power conversion means side of the ferrite core opening; and a Y-con busbar connecting an intermediate connection point where the other ends of the first capacitor to the third capacitor are commonly connected to ground, wherein the Y-con busbar is configured to pass through the cylindrical ferrite core together with the U busbar, V busbar, and W busbar.

[0022] The common-mode noise filter according to claim 4 is arranged such that a cylindrical ferrite core is disposed so that a part of a U (phase U) bus bar, a V (phase V) bus bar, and a W (phase W) bus bar that connect between a power input section of a power converter that inputs a three-phase power supply and a power conversion means penetrates therethrough. On the power conversion means side of the ferrite core opening, a first Y-con bus bar that connects between the U bus bar and the ground, a second Y-con bus bar that connects between the V bus bar and the ground, and a third Y-con bus bar that connects between the W bus bar and the ground are provided. A first capacitor is connected to a part of the first Y-con bus bar that is divided in the middle, a second capacitor is connected to a part of the second Y-con bus bar that is divided in the middle, and a third capacitor is connected to a part of the third Y-con bus bar that is divided in the middle. The first Y-con bus bar, the second Y-con bus bar, and the third Y-con bus bar are configured to penetrate the ferrite core together with the U bus bar, the V bus bar, and the W bus bar.

[0023] The common-mode noise filter according to claim 5 is the common-mode noise filter according to claims 1 to 4, wherein a part of the Y-con bus bar is further divided, and at least one resistive element is arranged to be in series with the first, second, and / or third capacitors.

[0024] The common-mode noise filter according to claim 6 is the common-mode noise filter according to claims 1 to 5, wherein without using the ferrite core, the P bus bar, the N bus bar, and the Y-con bus bar, or the U bus bar, the V bus bar, and the W bus bar and the Y-con bus bar are arranged in parallel and adjacent to each other for a predetermined length, and insulators are provided between the respective bus bars.

[0025] The common-mode noise filter according to claim 7 is the common-mode noise filter according to claims 1 to 5, and includes a cylindrical ferrite core, the respective bus bars that penetrate the ferrite core, and a printed circuit board on which the capacitors and resistive elements electrically connected to the respective bus bars are mounted, and the ferrite core and the printed circuit board are configured to be integrally formed in proximity to each other.

[0026] The common-mode noise filter according to claim 8 is the common-mode noise filter according to claim 6, wherein a printed circuit board electrically connected to the bus bar is provided at an end of the bus bars arranged in parallel and adjacent to each other, and the capacitor and the resistor element are mounted on the printed circuit board.

[0027] Claim 9 is a power converter to which a common-mode noise filter having the configuration according to any one of claims 1 to 8 is applied.

Advantages of the Invention

[0028] According to the configuration of claim 1, the common-mode noise voltage generated by the power conversion means occurs between the P bus bar and the N bus bar and the ground, and is grounded from the midpoint of the first and second capacitors connected in series from the P bus bar and the N bus bar via the Y-con bus bar. Therefore, the potential of the ferrite core power input side opening of the Y-con bus bar is the ground potential, and a common-mode noise voltage that varies with respect to the ground potential is applied to the potential of the ferrite core power conversion means side opening of the Y-con bus bar.

[0029] The P bus bar, the N bus bar, and the Y-con bus bar are magnetically coupled inside the ferrite core, and the coupling coefficient K thereof is approximately 1.0.

[0030] At both ends of the P bus bar and the N bus bar inside the ferrite core, due to the magnetic coupling, the same potential difference as the potential difference generated at both ends of the ferrite core of the Y-con bus bar is generated.

[0031] That is, when viewed from both ends of the ferrite core, the voltages at both ends of the P bus bar, the voltages at both ends of the N bus bar, and the voltages at both ends of the Y-con bus bar are equal, and are high-frequency signals having the same phase and the same amplitude.

[0032] As a result, when viewed with respect to the ground potential, the common-mode noise filter has a common-mode noise voltage on the power conversion means side of the P-busbar and N-busbar, and on the power input side of the P-busbar and N-busbar, one end of the Y-converter busbar is at ground potential, resulting in a stable potential without fluctuations. Therefore, it is possible to suppress the outflow of current due to the common-mode voltage generated from the power conversion means through the power wiring to the outside, that is, to suppress common-mode noise current.

[0033] Unintended parasitic inductances are present in the first and second capacitors and the Y-component busbar. However, the value of this inductance is several tens of nH, which is sufficiently small compared to the inductance value of the Y-component busbar in the portion that penetrates the ferrite core, several tens of uH. Nevertheless, even when the common-mode noise voltage in the high-frequency range is applied to the first and second capacitors, the reduction in common-mode noise current flowing through the Y-component busbar due to the parasitic inductance of the Y-component busbar is minimal, thus effectively preventing common-mode noise current from flowing out into the power supply wiring.

[0034] According to the configuration of claim 2, a first Y-converter busbar is provided with one end connected to the P-busbar on the power conversion means side of the ferrite core opening, and a second Y-converter busbar is provided with one end connected to the N-busbar. The first and second Y-converter busbars each have a first capacitor and a second capacitor connected in the middle of their conductive parts, and the first and second Y-converter busbars are configured to penetrate the ferrite core. Therefore, the arrangement of the first and second capacitors in the power converter can be either upstream (power input side) or downstream (power conversion means side) of the ferrite core, thus improving the design flexibility of the capacitor placement.

[0035] According to the configuration of claim 3, a cylindrical ferrite core is provided such that a portion of the U-busbar, V-busbar, and W-busbar, which connect the power input section of a power converter that receives a three-phase power supply to the power conversion means, passes through it. On the power conversion means side of the ferrite core opening, a Y-capacitor is provided, consisting of a first capacitor with one end connected to the U-busbar, a second capacitor with one end connected to the V-busbar, and a third capacitor with one end connected to the W-busbar. An intermediate connection point is provided where the other ends of the first capacitor to the third capacitor are commonly connected to ground, and a Y-con busbar is provided that passes through the cylindrical ferrite core along with the U-busbar, V-busbar, and W-busbar. Therefore, even in a power converter that receives a three-phase AC power supply, high-frequency common-mode noise current to the power input side can be effectively suppressed.

[0036] According to the configuration of claim 4, a cylindrical ferrite core is provided through which a portion of the U-busbar, V-busbar, and W-busbars connecting the power input section of a power converter receiving a three-phase power supply and the power conversion means are passed. On the power conversion means side of the ferrite core opening, a first Y-con busbar is provided connecting the U-busbar to ground, a second Y-con busbar connecting the V-busbar to ground, and a third Y-con busbar connecting the W-busbar to ground. First to third capacitors corresponding to the U-phase to W-phase are connected to the divided portions of each Y-con busbar, and each Y-con busbar is configured to pass through the ferrite core together with the U-busbar, V-busbar, and W-busbar. Therefore, the arrangement of each capacitor can be either upstream (power input side) or downstream (power conversion means side) of the ferrite core, thus improving the design flexibility of capacitor placement.

[0037] According to the configuration of claim 5, since at least one resistive element is arranged in series with the first, second, and third capacitors, anti-resonance (parallel resonance) occurs between the Y-combust bar and each capacitor, preventing an increase in common-mode noise current at a specific frequency.

[0038] According to the configuration of claim 6, the P busbar, N busbar, and Y combined busbar, or the U busbar, V busbar, W busbar, and Y combined busbar are arranged parallel to each other for a predetermined length, and the busbars are insulated from each other. Therefore, the ferrite core is not required to provide a predetermined mutual inductance between the busbars, and common-mode noise current can be suppressed effectively at low cost.

[0039] According to the configuration of claim 7, the ferrite core, busbar, capacitor, and resistor can be formed as a common-mode noise filter component, thereby reducing the assembly time of the power converter and lowering costs.

[0040] According to the configuration of claim 8, the busbar, capacitor, and resistor can be formed as a common-mode noise filter component, thereby reducing the assembly time of the power converter and lowering costs.

[0041] Claim 9 is a power converter to which a common-mode noise filter is applied according to the present invention. Therefore, it can effectively suppress electromagnetic fields generated by common-mode noise current when, for example, an in-vehicle inverter or converter is in operation, and does not interfere with wireless communication equipment such as in-vehicle radios. [Brief explanation of the drawing]

[0042] [Figure 1] This is an in-vehicle inverter to which the common-mode noise filter of the present invention is applied (Example 1). [Figure 2] This is an in-vehicle inverter to which the common-mode noise filter of the present invention is applied (Example 2). [Figure 3] This is a commercial power inverter to which the common mode noise filter of the present invention is applied (Example 3). [Figure 4] This is a commercial power inverter to which the common mode noise filter of the present invention is applied (Example 4). [Figure 5]This is an automotive inverter that applies a common-mode noise filter based on conventional technology. [Figure 6] This diagram illustrates the operating principle of the common-mode noise filter of the present invention. [Figure 7] This figure shows the common mode noise reduction effect of the inverter in Embodiment 1 of the present invention. [Figure 8] This figure shows the structure of the common-mode noise filter of the present invention (Example 5). [Figure 9] This figure shows the structure of the common-mode noise filter of the present invention (Example 6). [Modes for carrying out the invention]

[0043] The following describes the technologies being disclosed. However, the following description is essentially illustrative.

[0044] The basic operating principle of the common-mode noise filter of the present invention will be explained with reference to Figure 6. Note that Figure 6 simplifies the common-mode noise generated by the power converter, treating it as a normal-mode noise source.

[0045] Figure 6(a) is an equivalent circuit illustrating the filter characteristics when the common-mode noise filter of the present invention is applied. Figure 6(b) is an equivalent circuit illustrating the filter characteristics when a common-mode noise filter according to the prior art is applied. Figure 6(c) is a diagram showing the frequency characteristics of the noise attenuation when passing through each common-mode noise filter.

[0046] For example, an inverter uses three sets of half-bridge circuits to rapidly switch between the positive and negative terminals of a high-voltage power supply, generating a square wave that is output to each phase of the three-phase power supply and supplied to the motor windings. Therefore, the output signal waveform of the half-bridge is a high-frequency square wave signal. Since there is a predetermined capacitance between the conductor that transmits this square wave signal to the outside of the inverter and the ground, a differential current of the square wave signal flows through this capacitance. This current becomes a potential fluctuation on the busbar that supplies power to the half-bridge circuit, resulting in a high-frequency common-mode noise voltage.

[0047] The common-mode noise voltage mentioned above is shown as a voltage source in Figure 6(b) as the noise source. One end of the noise source is grounded, and the other end is output to the power supply side via a busbar.

[0048] The busbar has a predetermined resistance Rs2 and parasitic inductance Lb2. The common-mode noise filter connects the busbar to a capacitor C2 (Y capacitor), with the other end of C2 being grounded via a resistor Rd2 and an inductance Lf2, which will be described later. In addition, a portion of the busbar on the power supply side passes through a cylindrical ferrite core to form an inductance Lc, so the current from the noise source generates a common-mode noise voltage on the power supply side via Lc, and a noise current (common-mode noise current) I2 flows through the load resistor.

[0049] The conductive portion to which capacitor C2 is connected is a Y-conjoin busbar, and since it is made of a conductive plate of the same type as the busbar, there exists a predetermined parasitic inductance Lf2 determined by the physical dimensions of the Y-conjoin busbar.

[0050] Figure 6(c) shows the frequency characteristics of the noise source and the noise current flowing to the load resistor in this equivalent circuit. In the low frequency range of around 10 kHz, the signal from the noise source is transmitted directly to the power supply.

[0051] As the frequency of the noise source increases, the impedance of the capacitor C2 decreases, so a large amount of noise current flows through the Y-converter busbar, and the noise current flowing through the load resistor decreases... (1) As the frequency increases further, the impedance of the parasitic inductance Lf2 increases, causing the noise current flowing through the Y-component busbar to decrease, and thus the noise current flowing through the load resistor begins to increase... (2) The upper limit of the noise current flowing through the load resistor is determined by the ratio of the parasitic inductance Lb2 of the busbar to the parasitic inductance Lf2 of the Y-con busbar... (3) As the frequency increases further, the noise current decreases due to the increase in impedance of the inductance Lc formed through the ferrite core...(4).

[0052] As described above, conventional common-mode noise filters cannot adequately attenuate the noise source current flowing through the load resistor due to the parasitic inductance of the Y-combined busbar.

[0053] Equivalent circuit diagram 6(a) of the present invention shows a common-mode noise filter in which one end of a noise source representing a common-mode noise voltage is grounded, and the other end is output to the power supply side via a busbar.

[0054] Since a portion of the busbar on the power supply side passes through a cylindrical ferrite core to form an inductance Lc1, the current from the noise source generates a common-mode noise voltage on the power supply side via Lc1, and a noise current I1 flows through the load resistor.

[0055] The busbar has a predetermined resistance Rs1 and parasitic inductance Lb1. The common-mode noise filter includes a Y-con busbar connected to the noise source side at the ferrite core opening of the busbar, and the Y-con busbar passes through the ferrite core and is grounded via a capacitor C1.

[0056] Since the Y-conversion busbar is made of the same type of conductive plate as the busbar connected to the noise source, a predetermined parasitic inductance Lf1 exists, which is determined by the physical dimensions of the Y-conversion busbar.

[0057] Lc1 is the inductance formed when the busbar penetrates the ferrite core, and Lc2 is the inductance formed when the Y-conjoin busbar simultaneously penetrates the ferrite core. Since Lc1 and Lc2 have the same physical dimensions, Lc1 = Lc2.

[0058] Since Lc1 and Lc2 have the same polarity, the induced electromotive forces generated across both Lc1 and Lc2 are equal. Also, since the noise source sides of Lc1 and Lc2 are connected in common, the power supply terminals T1 and T2 of Lc1 and Lc2 are always at the same potential.

[0059] The noise current flowing through the busbar is grounded via Lc2, capacitor C1, and the parasitic inductance Lf1 of the Y-con busbar.

[0060] In the case of an actual inverter, Lc1 and Lc2 are approximately 40uH because they pass through a high-permeability ferrite core, and the parasitic inductance Lf1 is about 30nH.

[0061] The 40uH inductance Lc2 of the Y-combined busbar within the ferrite core is sufficiently large compared to the 30nH parasitic inductance Lf1 of the Y-combined busbar. Therefore, when a high-frequency noise source signal flows in series between Lc2 and Lf1, the voltage drop across Lf1 is almost negligible, effectively making it equivalent to having no Lf1 at all.

[0062] Figure 6(c) shows the frequency characteristics of the noise source and the noise current flowing to the load resistor in this equivalent circuit. In the low frequency range of around 10 kHz, the signal from the noise source is transmitted directly to the power supply.

[0063] As the frequency of the noise source increases, the current flowing through capacitor C1 increases, and the voltage drop across inductance Lc2 increases. This voltage drop becomes the voltage at power supply side T1 of Lc1. As a result, the signal transmitted from the noise source to the power supply side load resistor exhibits a frequency characteristic that attenuates linearly with increasing frequency.

[0064] If we consider the internal impedance of the noise source to be zero, the inductance Lc2 and capacitor C1 appear to be connected in parallel. As a result, Lc2 and C1 may resonate (or anti-resonate) in parallel, and T1 may produce an amplified signal of the noise source. Simultaneously, T2 will also produce the same amplified noise signal as T1. This is represented as "without Rd1" in Figure 6(c).

[0065] To avoid unintended operation due to this parallel resonance, a resistor Rd1 may be inserted in series with the capacitor C1. This resistor is generally called a damping resistor and has the effect of lowering the Q factor of the resonator and preventing parallel resonance.

[0066] As described above, the common-mode noise filter of the present invention has the excellent effect of being able to sufficiently attenuate the high-frequency components of the noise source without being affected by the parasitic inductance of the Y-combined busbar.

[0067] (First example) A first embodiment of the common-mode noise filter of the present invention will be described below with reference to Figure 1. In this embodiment, an example of applying the common-mode noise filter of the present invention to an in-vehicle inverter is disclosed.

[0068] In Figure 1, 1 is an inverter, which includes a common-mode noise filter 12 and a power conversion means 13. 11a and 11b are power input terminals, connected to a DC high-voltage power supply 2 via power wiring 2a and 2b, and configured to supply power to the power conversion means 13 from the positive busbar 1a and negative busbar 1b. Note that the control circuit for controlling the power conversion means 13 is not shown.

[0069] The power conversion means 13 consists of three sets of semiconductor half-bridges connected between the positive and negative busbars 1a and 1b. It outputs a load drive voltage via a three-phase output wiring as a square wave signal switched at high frequency from the midpoint of the half-bridges, generating a sinusoidal current in the internal windings of the drive motor 3 to drive the motor. The input section of the power conversion means 13 is equipped with a DC link capacitor 131 for the purpose of smoothing the power supply voltage.

[0070] The common-mode noise filter 12 includes a cylindrical ferrite core 121 that penetrates a portion of the positive busbar 1a inside the inverter 1, and the negative busbar 1b and the Y-con busbar 1d further penetrate the ferrite core 121.

[0071] A capacitor 122a is connected to the positive busbar 1a near the opening on the power conversion means 13 side of the ferrite core 121, and a capacitor 122b is connected to the negative busbar 1b near the opening on the power conversion means 13 side of the ferrite core 121. The other ends of capacitors 122a and 122b are connected in common and grounded via a Y-conformation busbar 1d. The Y-conformation busbar 1d is formed from a thin, flat conductor and therefore has a parasitic inductance Lf. 123 is the damping resistor Rd, which can be achieved by selecting a material with a predetermined resistivity for the Y-conformation busbar 1d, adjusting the material thickness of the Y-conformation busbar 1d, or by cutting the Y-conformation busbar 1d in the middle and attaching a fixed resistor.

[0072] When the power conversion means 13 operates, a common-mode noise current Icom flows between the output side stray capacitance of the power conversion means 13 and the motor winding stray capacitance and ground, as described above.

[0073] The parasitic inductance Lf of the Y-combined busbar 1d is extremely small, approximately 30 nH, which is significantly smaller than the 40 uH inductance inside the ferrite core of the Y-combined busbar 1d. Therefore, there is almost no voltage drop across the parasitic inductance Lf due to the common-mode noise current Icom.

[0074] If the damping resistor Rd is set to around 0.5 to 1 Ω, unintended characteristics due to the aforementioned parallel resonance can be prevented, and the voltage drop across the damping resistor Rd due to the common-mode noise current Icom is almost negligible.

[0075] Therefore, the power input side opening terminal Tc of the ferrite core 121 of the Y-combined busbar 1d is at approximately ground potential.

[0076] The common-mode noise current Icom flows through the Y-conversion busbar 1d to capacitors 122a and 122b, and then returns to the power conversion means 13 through the positive busbar 1a and negative busbar 1b.

[0077] Since the capacitance of capacitor 122a is selected to have a sufficiently small impedance in the bandwidth of the target common-mode noise frequency, the voltage drop across capacitor 122a due to the common-mode noise current Icom is approximately zero.

[0078] Since the capacitance of capacitor 122b is selected to have a sufficiently small impedance in the bandwidth of the target common-mode noise frequency, the voltage drop across capacitor 122b due to the common-mode noise current Icom is approximately zero.

[0079] When a common-mode noise current Icom flows, the potentials of the positive busbar 1a and the negative busbar 1b within the power conversion means 13 fluctuate at a high frequency relative to the ground potential, and this becomes the common-mode noise voltage. The high-frequency potential fluctuations of the positive busbar 1a and the negative busbar 1b are in phase and have the same amplitude.

[0080] The absolute potentials of the positive busbar 1a and the negative busbar 1b with respect to ground are offset by the DC voltage of the high-voltage power supply 2, but this is unrelated to the high-frequency common-mode noise current and will not be mentioned in this explanation.

[0081] The common-mode noise voltage is applied to terminal Ta-1, which is formed by the positive busbar 1a passing through the ferrite core 121 to the opening on the power conversion means 13 side, and to terminal Tb-1, which is formed by the negative busbar 1b passing through the ferrite core 121 to the opening on the power conversion means 13 side.

[0082] The fluctuations of the common-mode noise voltage across the positive busbar 1a and the negative busbar 1b are in phase and have the same amplitude, and the voltages across capacitor 122a and capacitor 122b are approximately zero. (We will not mention the fact that the voltage from the high-voltage power supply 2 is applied, as mentioned above.)

[0083] Since the Y-combined busbar 1d is connected to capacitors 122a and 122b, the relationship between the power conversion means 13-side opening terminal Tc-1 and the other terminals in the ferrite core 121 of the Y-combined busbar 1d is such that Ta-1 potential = Tb-1 potential = Tc-1 potential. In other words, common-mode noise voltages of the same phase and amplitude are generated at Ta-1, Tb-1, and Tc-1.

[0084] As described above, the power input side opening terminal Tc of the ferrite core 121 of the Y-combined busbar 1d is at ground potential. At the same time, a common-mode noise voltage is applied to the power conversion means 13 side opening terminal Tc-1 of the ferrite core 121 of the Y-combined busbar 1d.

[0085] The inductance values ​​of the internal positive busbar 1a, negative busbar 1b, and Y-con busbar 1d, which penetrate the ferrite core 121, are equal, they have the same polarity, and their coupling coefficient K is 1.

[0086] Therefore, the voltages at the power conversion means 13 side terminals Ta-1, Tb-1, and Tc-1 of the positive busbar 1a, negative busbar 1b, and Y-con busbar 1d are common-mode noise voltages, and the voltages at the power supply input side terminals Ta, Tb, and Tc remain stable and do not fluctuate to the same extent as the ground potential.

[0087] Therefore, since the potential between terminal Ta of the positive busbar 1a and terminal Tb of the negative busbar 1b is stable, it is possible to suppress the flow of high-frequency common-mode noise current to the power supply wiring 2a and 2b.

[0088] Figure 7 compares the simulation results of the common-mode noise current flowing through the power input wiring of an in-vehicle inverter to which the common-mode noise filter of the present invention is applied, and the common-mode noise current flowing through the power input wiring of an in-vehicle inverter to which a common-mode noise filter of the conventional technology is applied. As can be seen, when the common-mode noise filter of the present invention is applied, it can be confirmed that the noise level is reduced over a wide frequency band.

[0089] As described above, the common-mode noise filter of the present invention is not affected by the parasitic inductance of the Y-combined busbar and can suppress common-mode noise current to the power input side of the inverter over a wide frequency range including a desired high-frequency band. Therefore, when an inverter to which the common-mode noise filter of the present invention is applied is equipped, it has the excellent effect of not interfering with wireless communication equipment installed in the vehicle.

[0090] (Second example) A second embodiment of the common-mode noise filter of the present invention will be described below with reference to Figure 2. In this embodiment, an example of applying the common-mode noise filter of the present invention to an in-vehicle inverter is disclosed, and some of the explanations of the configuration and operation that overlap with the first embodiment will be omitted.

[0091] Figure 2, part 1 is an inverter, which includes a common-mode noise filter 12 and a power conversion means 13. 11a and 11b are power input terminals, connected to a DC high-voltage power supply 2 via power wiring 2a and 2b, and configured to supply power to the power conversion means 13 from the positive busbar 1a and negative busbar 1b. Note that the control circuit for controlling the power conversion means 13 is not shown.

[0092] The power conversion means 13 consists of three sets of semiconductor half-bridges connected between the positive and negative busbars. It outputs a load drive voltage via a three-phase output wiring as a square wave signal switched at high frequency from the midpoint of the half-bridges, generating a sinusoidal current in the internal windings of the drive motor 3 to drive the motor. The input section of the power conversion means 13 is equipped with a DC link capacitor 131 for the purpose of smoothing the power supply voltage.

[0093] The common-mode noise filter 12 includes a cylindrical ferrite core 121 that penetrates a portion of the positive busbar 1a inside the inverter 1, and the negative busbar 1b, Y-con busbar 1d, and Y-con busbar 1e further penetrate the ferrite core 121.

[0094] A capacitor 122a is connected to the positive busbar 1a near the opening on the power conversion means 13 side of the ferrite core 121, and a capacitor 122b is connected to the negative busbar 1b near the opening on the power conversion means 13 side of the ferrite core 121. Capacitor 122a is grounded via a Y-con busbar 1d. Capacitor 122b is grounded via a Y-con busbar 122e.

[0095] The Y-combined busbars 1d and 1e are formed from thin, flat conductors and therefore have parasitic inductance Lf. 123a and 123b are damping resistors Rd, which can be achieved by selecting a material with a predetermined resistivity for the Y-busbar, adjusting the thickness of the Y-combined busbar material, or by cutting the Y-combined busbar in the middle and attaching a fixed resistor.

[0096] With the above configuration, the voltage at the power conversion means 13 side opening of the ferrite core 121 for each bus bar 1a, 1b, 1d, and 1e that passes through the ferrite core 121 is a common-mode noise voltage, and the voltage at the power input side opening of the ferrite core 121 for each bus bar 1a, 1b, 1d, and 1e remains stable and does not fluctuate to the same extent as the ground potential.

[0097] Therefore, since the potentials of the power input terminals 11a and 11b are stable, it is possible to suppress the flow of high-frequency common-mode noise current to the power wiring 2a and 2b.

[0098] Furthermore, the arrangement of capacitors 122a and 122b in this embodiment is Y-combust bar 1d can be located anywhere on the Y-conbusbar 1e. However, the capacitors 122a and 122b, which have relatively large physical dimensions, can be placed either on the power input side or the power conversion means side of the ferrite core 121, which has the advantage of simplifying the design of the power converter.

[0099] (Third example) A third embodiment of the common-mode noise filter of the present invention will be described below with reference to Figure 3. In this embodiment, an example of applying the common-mode noise filter of the present invention to a commercial power inverter is disclosed, and some of the explanations of configurations and operations that overlap with the first embodiment will be omitted.

[0100] Figure 31 shows an inverter, which includes a common-mode noise filter 12 and a power conversion means 13. 11a, 11b, and 11c are power input terminals connected to a three-phase AC power supply 2 via power wiring 2a, 2b, and 2c, and power is supplied from the U (U-phase) busbar 1a, V (V-phase) busbar 1b, and W (W-phase) busbar to the power conversion means 13. The power conversion means 13 converts the AC power from the U busbar 1a, V busbar 1b, and W busbar 1c into a DC voltage using a rectifier 133 and smooths it using a DC link capacitor 131. Note that the control circuit for controlling the power conversion means 13 is not shown.

[0101] The power conversion means 13 consists of a rectifier means 133 connected to the U busbar 1a, V busbar 1b, and W busbar 1c, and three sets of semiconductor half-bridges connected to a DC power supply smoothed by a DC link capacitor 131. A square wave signal switched at high frequency from the midpoint of the half-bridges is output as a load drive voltage via three-phase output wiring, generating a sinusoidal current in the internal windings of the motor 3 to drive the motor.

[0102] The common-mode noise filter 12 includes a cylindrical ferrite core 121 that penetrates a portion of the U-busbar 1a inside the inverter 1, and the V-busbar 1b, W-busbar 1c, and Y-con busbar 1d further penetrate the ferrite core 121.

[0103] Capacitor 122a is connected to the U-busbar 1a near the opening on the power conversion means 13 side of the ferrite core 121, capacitor 122b is connected to the V-busbar 1b near the opening on the power conversion means 13 side of the ferrite core 121, and capacitor 122c is connected to the W-busbar 1c near the opening on the power conversion means 13 side of the ferrite core 121. The other ends of capacitors 122a, 122b, and 122c are connected in common and then grounded via the Y-con busbar 1d.

[0104] The Y-combined busbar 1d is formed from a thin, flat conductor and therefore has a parasitic inductance Lf. 123 is the damping resistor Rd, which can be achieved by selecting a material with a predetermined resistivity for the Y-busbar, adjusting the thickness of the Y-combined busbar material, or by cutting the Y-combined busbar in the middle and attaching a fixed resistor.

[0105] With the above configuration, the voltage at the power conversion means 13 side opening of the ferrite core 121 for each bus bar 1a, 1b, 1c, and 1d that passes through the ferrite core 121 is a common-mode noise voltage, and the voltage at the power input side opening of the ferrite core 121 for each bus bar 1a, 1b, 1c, and 1d remains stable and does not fluctuate to the same extent as the ground potential.

[0106] Therefore, since the potentials of the power input terminals 11a, 11b, and 11c are stable, it is possible to suppress the flow of high-frequency common-mode noise current to the power wiring 2a, 2b, and 2c.

[0107] (Fourth embodiment) A fourth embodiment of the common-mode noise filter of the present invention will be described below with reference to Figure 4. In this embodiment, an example of applying the common-mode noise filter of the present invention to a commercial power inverter is disclosed, and some explanations of the configuration and operation that overlap with the first and second embodiments will be omitted.

[0108] Figure 4-1 shows an inverter, which includes a common-mode noise filter 12 and a power conversion means 13. 11a, 11b, and 11c are power input terminals connected to a three-phase AC power supply 2 via power wiring 2a, 2b, and 2c, and configured to supply power from the U-busbar 1a, V-busbar 1b, and W-busbar 1c to the power conversion means 13. The power conversion means 13 converts the AC power from the U-busbar 1a, V-busbar 1b, and W-busbar 1c into a DC voltage using a rectifier 133 and smooths it using a DC link capacitor 131. Note that the control circuit for controlling the power conversion means 13 is not shown.

[0109] The power conversion means 13 consists of a rectifier means 133 connected to the U busbar 1a, V busbar 1b, and W busbar 1c, and three sets of semiconductor half-bridges connected to a DC power supply smoothed by a DC link capacitor 131. A square wave signal switched at high frequency from the midpoint of the half-bridges is output as a load drive voltage via three-phase output wiring, generating a sinusoidal current in the internal windings of the motor 3 to drive the motor.

[0110] The common-mode noise filter 12 includes a cylindrical ferrite core 121 that penetrates a portion of the U-busbar 1a inside the inverter 1, and the V-busbar 1b, W-busbar 1c, Y-con busbar 1d, Y-con busbar 1e, and Y-con busbar 1f further penetrate the ferrite core 121.

[0111] A capacitor 122a is connected to the U-busbar 1a near the opening on the power conversion means 13 side of the ferrite core 121, a capacitor 122b is connected to the V-busbar 1b near the opening on the power conversion means 13 side of the ferrite core 121, and a capacitor 122c is connected to the W-busbar 1b near the opening on the power conversion means 13 side of the ferrite core 121. The other ends of capacitors 122a, 122b, and 122c are grounded via Y-con busbars 1d, 1e, and 1f.

[0112] The Y-combination busbars 1d, 1e, and 1f are formed from thin, flat conductors and therefore have parasitic inductance Lf. 123a, 123b, and 123c are damping resistors Rd, which can be achieved by selecting a material with a predetermined resistivity for the Y-busbar, adjusting the thickness of the Y-combination busbar material, or by cutting the Y-combination busbar in the middle and attaching a fixed resistor.

[0113] With the above configuration, the voltage at the power conversion means 13 side opening of the ferrite core 121 for each bus bar 1a, 1b, 1c, 1d, 1e, 1f that passes through the ferrite core 121 is a common-mode noise voltage, and the voltage at the power input side opening of the ferrite core 121 for each bus bar 1a, 1b, 1c, 1d, 1e, 1f remains stable and does not fluctuate to the same extent as the ground potential.

[0114] Therefore, since the potentials of the power input terminals 11a, 11b, and 11c are stable, it is possible to suppress the flow of high-frequency common-mode noise current to the power wiring 2a, 2b, and 2c.

[0115] Furthermore, the capacitors 122a, 122b, and 122c in this embodiment can be placed anywhere on the Y-component busbars 1d, 1e, and 1f, respectively. However, the capacitors 122a, 122b, and 122c, which have relatively large physical dimensions, can be placed either on the power input side or the power conversion means side of the ferrite core 121, which has the advantage of simplifying the design of the power converter.

[0116] (Fifth embodiment) A fifth embodiment of the common-mode noise filter of the present invention will be described below with reference to Figure 8. This embodiment discloses the physical structure of the common-mode noise filter based on the first embodiment described above.

[0117] Reference numeral 12 denotes the common-mode noise filter of the present invention, in which busbars 1a, 1b, and 1c, which are made of thin copper plates, pass through a cylindrical ferrite core 121.

[0118] Each busbar 1a, 1b, and 1c has a fastening hole on the power input side for fastening to the power input terminal of the power converter, and the other ends of busbars 1a and 1b have fastening holes for fastening a busbar for electrically connecting to the power conversion means side of the power converter.

[0119] A printed circuit board 124 is positioned in close proximity to the ferrite core 121, and the copper foil patterns of the printed circuit board 124 are electrically connected to the busbars 1a, 1b, and 1c by solder or screws (not shown).

[0120] The printed circuit board 124 is equipped with capacitors 122a and 122b and a resistor 123. Capacitor 122a is electrically connected to the circuit of busbar 1a and resistor 123, capacitor 122b is electrically connected to the circuit of busbar 1b and resistor 123, and the other end of resistor 124 is electrically connected to busbar 1c.

[0121] The busbar, ferrite core, and printed circuit board may be molded together as a single unit (not shown) using resin molding, or they may be fixed inside a resin case.

[0122] In this embodiment, capacitors 122a and 122b and resistor 123 are mounted on a printed circuit board 124 and electrically connected to each busbar. However, these capacitors and resistors may be directly connected to each busbar without using a printed circuit board. Furthermore, this embodiment shows a specific structure in which three busbars penetrate a ferrite core, based on Embodiment 1 of the present invention. However, a structure in which multiple busbars penetrate the core may be used, corresponding to Embodiments 2 to 4.

[0123] (Sixth embodiment) A sixth embodiment of the common-mode noise filter of the present invention will be described below with reference to Figure 9. This embodiment discloses the physical structure of the common-mode noise filter based on the first embodiment.

[0124] Reference numeral 12 denotes the common-mode noise filter of the present invention, wherein the power input side of the busbars 1a, 1b, and 1c, which are formed from thin copper plates, has fastening holes for fastening to the power input terminals of the power converter, and the other ends of busbars 1a and 1b also have fastening holes for fastening busbars for electrically connecting to the power conversion means side of the power converter.

[0125] Busbars 1a, 1b, and 1c are arranged opposite each other with an insulating member 1z in between over a length L. This configuration ensures that the busbars 1a, 1b, and 1c form mutual inductances with each other and are magnetically coupled, and each busbar 1a, 1b, and 1c has a predetermined inductance.

[0126] A printed circuit board 124 is placed at the power conversion means end of each busbar, and the copper foil patterns of the printed circuit board 124 are electrically connected to the busbars 1a, 1b, and 1c by solder or screws (not shown).

[0127] The printed circuit board 124 is equipped with capacitors 122a and 122b and a resistor 123. Capacitor 122a is electrically connected to the circuit of busbar 1a and resistor 123, capacitor 122b is electrically connected to the circuit of busbar 1b and resistor 123, and the other end of resistor 123 is electrically connected to the circuit of busbar 1c.

[0128] The busbar and printed circuit board may be formed as a single resin mold (not shown) or fixed inside a resin case.

[0129] In this embodiment, capacitors 122a and 122b and resistor 123 are mounted on a printed circuit board 124 and electrically connected to each busbar. However, these capacitors and resistors may be directly connected to each busbar without using a printed circuit board. Furthermore, this embodiment shows a specific structure in which three busbars are arranged opposite each other, based on Embodiment 1 of the present invention. However, a structure in which multiple busbars are arranged opposite each other may be used, corresponding to Embodiments 2 to 4.

[0130] As shown in Examples 1 to 6 above, the common-mode noise filter of the present invention includes a ferrite core in the conductive path of the Y-conversion busbar, and the inductance of this ferrite core portion becomes large. Therefore, the impedance of the Y-conversion circuit is large, and the high-frequency common-mode current flowing back through the power conversion means is reduced by this inductance. Conventional Y-capacitors suppress the outflow of common-mode noise current to the power input wiring by minimizing the parasitic inductance of the Y-conversion busbar as much as possible and grounding the high-frequency common-mode components superimposed on the P-busbar and N-busbar inside the inverter with a sufficiently low impedance.

[0131] Due to the differences described above, inverters using the common-mode noise filter of the present invention exhibit a smaller common-mode noise current flowing from the load motor windings toward ground, while inverters employing conventional common-mode noise filters exhibit a larger common-mode noise current flowing from the load motor windings toward ground.

[0132] It is known that a portion of the common-mode noise current flowing through the motor windings also flows into the motor bearings, reducing their lifespan. Therefore, the common-mode noise filter of the present invention can reduce the absolute value of the common-mode noise current, which also has the added benefit of improving the lifespan of the motor bearings. [Explanation of Symbols]

[0133] 1 Inverter 2 power supply 3 motors 12 Common-mode noise filters 13 Power conversion means 121 Ferrite core 122 Capacitors 123 Damping resistor

Claims

1. The power input section of the power converter and the power conversion means are connected by a P busbar and an N busbar, A cylindrical ferrite core is arranged such that a portion of the P busbar and the N busbar passes through it, On the power conversion means side of the opening of the ferrite core, a Y capacitor is provided, consisting of a first and second capacitor connected in series between the P busbar and the N busbar. The system includes a Y-conbus bar connecting the intermediate connection points of the first and second capacitors to ground, The Y busbar is configured to pass through the cylindrical ferrite core together with the P busbar and the N busbar in a common mode noise filter.

2. A cylindrical ferrite core is positioned so that a portion of the P busbar and N busbar, which connect the power input section and the power conversion means of the power converter, passes through it. On the power conversion means side of the opening of the ferrite core, a first Y busbar connects the P busbar and ground, A second Y busbar connects the aforementioned N busbar to ground, Equipped with, The first capacitor is connected to the section of the first Y-component busbar that has been divided in the middle. A common-mode noise filter in which a second capacitor is connected to a portion of the second Y-combined busbar that has been split in the middle, and the first Y-combined busbar and the second Y-combined busbar are configured to pass through the ferrite core together with the P-busbar and the N-busbar.

3. A U-busbar, a V-busbar, and a W-busbar connect the power input section of a power converter that receives a three-phase power supply to the power conversion means. A cylindrical ferrite core is arranged so as to pass through a portion of the U-busbar, the V-busbar, and the W-busbar, On the power conversion means side of the opening of the ferrite core, a Y capacitor is provided, consisting of a first capacitor with one end connected to the U busbar, a second capacitor with one end connected to the V busbar, and a third capacitor with one end connected to the W busbar. A Y-conbus bar connects the intermediate connection point, where the other end of the third capacitor is commonly connected to the first capacitor, to ground, Equipped with, The Y busbar is configured to pass through the cylindrical ferrite core together with the U busbar, the V busbar, and the W busbar in a common mode noise filter.

4. U-busbars, V-busbars, and W-busbars connect the power input section of a power converter that receives a three-phase power supply to the power conversion means, A cylindrical ferrite core is arranged so as to pass through a portion of the U-busbar, the V-busbar, and the W-busbar, On the power conversion means side of the opening of the ferrite core, a first Y-conjoined busbar connecting the U-busbar and ground, a second Y-conjoined busbar connecting the V-busbar and ground, and a third Y-conjoined busbar connecting the W-busbar and ground, Equipped with, A common-mode noise filter comprising: a first capacitor connected to a portion of the first Y-component busbar that has been split midway; a second capacitor connected to a portion of the second Y-component busbar that has been split midway; and a third capacitor connected to a portion of the third Y-component busbar that has been split midway; and the first Y-component busbar, the second Y-component busbar, and the third Y-component busbar, together with the U-busbar, the V-busbar, and the W-busbar, are configured to pass through the ferrite core.

5. In the common-mode noise filters of claims 1 to 4, A common-mode noise filter obtained by further dividing a portion of the Y-combust bar and arranging at least one resistive element in series with the first, second, and / or third capacitors.

6. In the common-mode noise filters of claims 1 to 5, A common-mode noise filter configured without using the ferrite core, in which the P busbar, the N busbar, and the Y combined busbar, or the U busbar, the V busbar, the W busbar, and the Y combined busbar are arranged parallel to each other for a predetermined length, and the spaces between the busbars are insulated.

7. In the common-mode noise filters of claims 1 to 5, The aforementioned cylindrical ferrite core, Each of the busbars that penetrates the ferrite core, A printed circuit board equipped with the capacitor and resistor elements electrically connected to each of the busbars, Equipped with, A common-mode noise filter formed by integrating the ferrite core and the printed circuit board in close proximity.

8. In the common-mode noise filter of claim 6, At the ends of the busbars arranged in parallel and close proximity, A common-mode noise filter comprising a printed circuit board electrically connected to the busbar, with the capacitor and resistor elements mounted on the printed circuit board.

9. A power converter to which the common mode noise filter described in any one of claims 1 to 8 is applied.

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