JP2012019504A - Noise filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wide-band effective noise filter that can suppress high pass component noise, not only large conductive noise generated in a switching carrier component for power conversion.SOLUTION: The noise filter comprises: main circuit wiring 7a and 7b which are connected to a power converter to propagate AC power; a plurality of common mode coils 1 and 4; and a capacitor to ground 5 for each main circuit wiring for each phase. At least one of the common mode coils is the common mode coil 1 having a resonance circuit in which a resonant wiring 2 is wound in phase with the main circuit wiring 7a and 7b and a resonance capacitor 3 across the resonant wiring 2 is connected.

Description

  The present invention relates to a technique for suppressing conductive noise generated by a power converter using a noise filter.

  In the conventional noise filter, a resonance wiring is attached to a common mode coil, a coil having a resonance capacitor attached to both ends thereof, and a ground-to-ground capacitor. The filter has a large attenuation amount only at a frequency at which resonance is caused by the inductance value of the resonance wiring and the capacitance value of the resonance capacitor (see Patent Document 1 below).

Japanese Patent Laid-Open No. 2001-197665 (page 3, left row, line 1 to line 10, FIG. 1)

  Conductive noise generated from the power conversion device is generated in a wide band from a low frequency component caused by harmonics of the switching carrier frequency of the power conversion element to a high frequency component caused by the impedance of the load device. However, conventionally proposed noise filters are effective only with the resonance frequency of the resonance circuit as the attenuation amount of the noise filter, and it is difficult to secure a noise filter effective over a wide band.

  An object of the present invention is to provide a noise filter that is effective not only for large conductive noise generated by switching carrier components of a power conversion element but also for high-frequency components, which is effective for a wide band. .

  The present invention includes a plurality of common mode coils and a ground-to-ground capacitor for each main circuit wiring in a main circuit wiring connected to a power converter and propagating AC power, wherein at least one common mode coil includes A noise filter comprising a common mode coil with a resonance circuit in which a resonance wiring is wound in the same phase as the main circuit wiring and a resonance capacitor is connected between both ends of the resonance wiring.

  According to the present invention, it is possible to provide a noise filter that is effective not only for large conductive noise generated by switching carrier components of a power conversion element but also for high-frequency components, which is effective for a wide band.

It is a circuit block diagram which shows the noise filter by Embodiment 1 of this invention. It is a figure which shows an example of the attenuation characteristic of the noise filter with respect to the common mode noise by Embodiment 1 of this invention. It is a figure which shows an example of a structure of the common mode coil with the resonant circuit of the noise filter by Embodiment 2 of this invention. It is a figure which shows an example of a structure of the common mode coil of the noise filter by Embodiment 3 of this invention, and the common mode coil with a resonance circuit. It is a figure which shows an example of a structure of the common mode coil with the resonant circuit of the noise filter by Embodiment 4 of this invention. It is a figure which shows an example of a structure of the common mode coil of the noise filter by Embodiment 4 of this invention, and the common mode coil with a resonance circuit. It is a figure which shows the structure of the resonance circuit part of the common mode coil with a resonance circuit used in order to demonstrate the characteristic of the noise filter by Embodiment 5 of this invention. It is a figure for demonstrating the characteristic of the resonance circuit of FIG. It is a figure which shows the characteristic of the resonance circuit of FIG. 8 in detail. It is a figure which shows the equivalent circuit of the resonant circuit part of the common mode coil with the resonant circuit of the noise filter by Embodiment 5 of this invention.

  The noise filter according to the present invention will be described below with reference to the drawings according to each embodiment. In each embodiment, the same or corresponding parts are denoted by the same reference numerals, and redundant description is omitted.

Embodiment 1 FIG.
FIG. 1 is a circuit configuration diagram showing an example of a noise filter according to Embodiment 1 of the present invention. In FIG. 1, for example, an AC power source is connected to one end A, a power conversion element is connected to the other end B, and a single-phase reciprocating main circuit wiring 7a, 7b that propagates AC power from the AC power source to the power conversion element is a common mode coil. 4 and a common mode coil 1 with a resonance circuit are provided. A ground-to-ground capacitor 5 is connected to each main circuit wiring 7a, 7b, and a line-to-line capacitor 6 is connected between the main circuit wirings 7a, 7b. The common mode coil 4 has main circuit wires 7a and 7b wound in the same phase, and the common mode coil 1 with a resonance circuit further has resonance circuits 2 and resonance wires wound around the main circuit wires 7a and 7b in the same phase. 2 is provided with a resonance circuit unit including a resonance capacitor 3 connected between the two ends.

  In a power conversion device such as an inverter, high frequency noise is generated by switching of a power conversion element. The high-frequency noise becomes common mode noise via a load device such as a motor, and flows into the ground (GND) or the input power supply side as conductive noise. In order to suppress such conductive noise, a noise filter is attached to the input power supply side of the power converter. Since the conductive noise is caused by the switching of the power conversion element, it is generated at the frequency of the harmonic component of the switching carrier frequency. For this reason, conductive noise is generated for each carrier frequency, and generally exhibits frequency characteristics that are large in the low frequency band and small in the high frequency band. In the high frequency band, conductive noise is generated due to the impedance between the power converter and a load device (not shown) that receives the converted power. As a noise filter attached to the input power source side of the power converter, it is necessary to suppress both noise of the inverter carrier frequency generated on the low frequency side and noise caused by the impedance of the load device generated on the high frequency side.

  With the configuration shown in FIG. 1, the attenuation amount of the noise filter with respect to common mode noise is as shown in FIG. In this way, the filter has a large attenuation at the resonance frequency of the resonance circuit unit of the common mode coil 1 with the resonance circuit, and suppresses conductive noise generated at the harmonic component frequency of the switching carrier frequency of the power conversion element. It becomes possible. Further, by using such a noise filter, it is possible to secure an attenuation amount in the high frequency band by the common mode coil 4 and the ground-to-ground capacitor 5 working even in a band deviating from the resonance frequency of the resonance circuit unit. Therefore, it is possible to obtain a noise filter that is effective not only at the resonance frequency of the resonance circuit but also over a wide band.

Also by such a configuration, it is possible to determine the capacitance value C ₅ of the capacitance values C ₃ and ground between the capacitor 5 of the resonant capacitor 3 independently. Capacitance value C ₃ of the resonance capacitor 3 is to determine the resonant frequency of the resonant circuit may be determined from the inductance value L ₂ of the resonant lines 2. The capacitance value C ₅ of ground between the capacitor 5 in order to secure the attenuation in a band off from the resonance frequency of the resonance circuit, the inductance value L ₄ of the normal common mode coil 4 resonance capacitor 3 is not attached It is possible to decide. For this reason, there is an advantage that the filter circuit constant can be determined from the desired inductance value and capacitor capacitance value. The capacitance value C ₅ generally ground between the capacitor 5 is set smaller than the point of view of leakage current, capacitance value C ₃ of the resonance capacitor 3 is set larger from the viewpoint of saturation of the coil core. Thus, the noise filter as in the first embodiment of the present invention has a great merit because the capacitance values of the resonant capacitor 3 and the ground capacitor 5 can be determined independently.

Note is made smaller than the capacitance value C ₃ of the resonance capacitor 3 of the capacitance value C ₅ a resonant circuit with common-mode coil 1 of the ground between the capacitor 5, it is possible to reduce the leakage current.
Further, by decreasing the inductance value L ₁ of the resonant circuit with common-mode coil 1 than the inductance value L ₄ of the common mode coil 4 having no resonant circuit, to suppress the magnetic saturation of the common mode current and the resonance current Can do.
Further, the winding inductance value L ₂ of the resonance wiring 2 of the resonance mode common mode coil 1 and the capacitance value C ₃ of the resonance capacitor 3 are set to values that become the resonance frequency according to the switching carrier frequency in the power converter. Thereby, the conductive noise which generate | occur | produces with the carrier frequency of switching in a power converter device can be efficiently suppressed with a noise filter.

Embodiment 2. FIG.
FIG. 3 is a diagram showing an example of the configuration of a common mode coil with a resonance circuit of a noise filter according to Embodiment 2 of the present invention. In the common mode coil 1 with a resonance circuit, single-phase main circuit wirings 7a and 7b are wound around the magnetic core 8 in the same phase. In addition, the resonance wiring 2 is wound in the same phase as the main circuit wirings 7 a and 7 b, and the resonance capacitors 3 are attached to both ends of the resonance wiring 2.

In such a common mode coil with a resonance circuit 1, the inductance value L ₂ of the resonance wiring ₂ and the capacitance value C of the resonance capacitor 3 with respect to the common mode current flowing in the same phase through the single-phase main circuit wirings 7 a and 7 b. ₃ can have a large impedance at the frequency of resonance. However, since no magnetic flux is generated in the magnetic core 8 with respect to the normal mode current (for example, commercial frequency current) flowing in the opposite phase through the single-phase main circuit wirings 7a and 7b, core saturation can be suppressed.

  Thus, according to the present invention, not only the main circuit wirings 7a and 7b but also the resonance wiring 2 is wound around the magnetic core 8 and the resonance capacitor 3 is attached (resonance circuit 3). By configuring the unit, a common mode coil is configured to have a resonance impedance with respect to the common mode current, and a noise filter is configured by attaching such a common mode coil with a resonance circuit.

Embodiment 3 FIG.
4 is a diagram showing an example of the configuration of a common mode coil and a common mode coil with a resonance circuit of a noise filter according to Embodiment 3 of the present invention. The single-phase main circuit wirings 7a and 7b are wound around two concentric (coaxial) magnetic cores, that is, the outer annular magnetic core 8a and the inner annular magnetic core 8b as a whole. On the other hand, the resonance wiring 2 is wound only on one of the outer annular magnetic core 8a and the inner annular magnetic core 8b, here only the outer annular magnetic core 8a, and the resonance capacitor 3 is provided at both ends. Connected to form a resonant circuit unit.

  With this configuration, the outer annular magnetic core 8a forms a resonance circuit, but the inner annular magnetic core 8b does not form a resonance circuit. Therefore, the common mode coil 4 and the common with the resonance circuit in the first embodiment are used. A noise filter having a large attenuation amount at the resonance frequency and an attenuation effect in a wide band can be obtained by integrating the mode coils 1 into one.

  Note that the two magnetic cores do not have to be coaxial, but may be two magnetic cores extending in parallel.

Embodiment 4 FIG.
FIG. 5 is a diagram showing an example of the configuration of a common mode coil with a resonance circuit of a noise filter according to Embodiment 4 of the present invention. FIG. 6 is a diagram showing an example of the configuration of a common mode coil and a common mode coil with a resonance circuit of a noise filter according to Embodiment 4 of the present invention. FIG. 5 shows a configuration of the second embodiment shown in FIG. 3 in which a plurality of resonance circuit units each including a resonance wiring 2 and a resonance capacitor 3 are provided. FIG. 6 shows a configuration of the third embodiment shown in FIG. 4 in which a plurality of resonance circuit units each including a resonance wiring 2 and a resonance capacitor 3 are provided. In the resonance circuit unit, the resonance wiring 2 may be wound around either the outer annular magnetic core 8a or the inner annular magnetic core 8b. A plurality of resonance circuits are formed by attaching a plurality of resonance circuit units (2, 3), and the common mode coil with a resonance circuit can have resonance impedances at a plurality of frequencies.

  According to such a configuration, since the common mode coil with a resonance circuit mounted on the noise filter has a plurality of resonance circuits, a large impedance can be obtained at a plurality of resonance frequencies. For this reason, the attenuation characteristic of the noise filter can have a large attenuation at a plurality of frequencies, and a noise filter corresponding to a frequency having a plurality of peaks can be obtained with respect to the conductive noise from the power converter. it can.

Embodiment 5 FIG.
FIG. 7 is a diagram showing a configuration of a resonance circuit portion of a common mode coil used for explaining the characteristics of the noise filter according to the fifth embodiment of the present invention. Specifically, the capacitor 3 is removed from the resonance wiring 2 and the magnetic core 8 c is wound with the resonance wiring 2. When the impedance frequency and phase characteristics of the resonance circuit of FIG. 7 are measured, the result shown in FIG. 8 is obtained. The impedance | Z | shown by the solid line (left vertical axis in FIG. 8) is 90 degrees in the low frequency band around 0.1 MHz, and the phase shown by the broken line (right vertical axis in FIG. 8) is almost 100% inductive. Show. However, when the frequency becomes as high as several hundred kHz, resistance is added and the phase of the impedance gradually becomes smaller than 90 degrees. When the frequency is further increased, the phase is slightly lower than 0 degree, and the impedance is almost resistive.

  When the impedance Z is decomposed into inductive and resistive, it becomes as shown in FIG. The solid line indicates impedance | Z |, the alternate long and short dash line indicates resistance R (resistance component), and the broken line indicates inductivity | jωL | (inductive reactance component). As apparent from FIG. 9, the impedance is almost 100% reactance component in a low frequency band around 0.1 MHz. When the frequency is as high as several hundred kHz, the resistance component increases. In the band of several hundred kHz, the reactance component has a maximum value, and when the frequency is further increased, the reactance component due to the inductance becomes zero. The resistance component takes a maximum value in the vicinity of the frequency that becomes 0, and in the frequency band above this, the impedance is almost a resistance component. Such characteristics are caused by the magnetic characteristics of the material of the magnetic core 8c, but are characterized in that reactance and resistance are switched according to the frequency.

  On the other hand, an equivalent circuit of the resonance circuit portion of the common mode coil with resonance circuit 1 can be represented by a parallel circuit of a capacitor CC, an inductance LL, and a resistance RR as shown in FIG. The resonance Q value can be written as Q = 2πfCR, where f is the resonance frequency, C is the capacitance of the capacitor, and R is the resistance value. The larger the Q value, the narrower the resonance band and the larger impedance can be obtained. That is, it can be said that the common mode coil 1 with a resonance circuit of the noise filter is advantageous to have a large Q value. Since the resistance value R corresponds to the resistance component of the coil, in order to obtain a filter having a large attenuation, the attenuation can be drastically increased by using a portion where the resistance component of the coil increases. However, as shown in FIG. 9, in the vicinity where the resistance component has a maximum value, the (inductive) reactance also becomes small, so the coil L value (inductance L) becomes small and it becomes difficult to resonate. is there. In other words, the upper limit frequency for dramatically increasing the filter attenuation is determined by the frequency at which the resistance component takes the maximum value, or the frequency at which the (inductive) reactance component becomes 0 (the phase of the coil impedance is 0). is there.

  As described above, the resonance frequency of the resonance circuit including the resonance wiring 2 and the resonance capacitor 3 is equal to or higher than the lowest frequency (generally 150 kHz) at which noise is restricted, and the resistance component of the impedance of the common mode coil 1 with the resonance circuit. Is set to a frequency that is less than the frequency at which the maximum value is reached, or less than the frequency at which the reactance component of the impedance is 0 (the phase of the impedance of the common mode coil 1 with a resonance circuit is 0 degrees). Can be earned.

In each of the above embodiments, a single-phase alternating current has been described. However, the present invention is not limited to this and can be applied to a multi-phase alternating current.
Furthermore, the present invention is not limited to the above-described embodiments, and it goes without saying that all possible combinations thereof are included.

  In the present invention, since the resonance wiring and the resonance capacitor are attached to the common mode coil, the common mode coil has a large impedance in a frequency band where conductive noise occurs. With the common mode coil with the resonance circuit, the common mode coil not wound with the resonance wiring, and the capacitor between the ground, the frequency characteristics of the attenuation amount are not monotonously decreased in the noise filter of the present invention, but at the frequency at which the coil resonates. A large amount of attenuation can be obtained, and a noise filter effective not only for the resonance frequency of the resonance circuit but also for a wide band can be obtained. For this reason, with respect to the conductive noise generated from the power converter, a necessary attenuation can be ensured by a small common mode coil or a small-capacitance capacitor to ground.

  DESCRIPTION OF SYMBOLS 1 Common mode coil with a resonance circuit, 2 Resonance wiring, 3 Resonance capacitor, 4 Common mode coil, 5 Ground-to-ground capacitor, 6-line capacitor, 7a, 7b Main circuit wiring, 8, 8c Magnetic body core, 8a Outer annular magnetism Body core, 8b Inner annular magnetic core.

Claims (9)

  A main circuit wiring that is connected to a power converter and propagates AC power includes a plurality of common mode coils and a ground-to-ground capacitor for each main circuit wiring of each phase, and at least one of the common mode coils includes the main circuit wiring. A noise filter comprising a common mode coil with a resonance circuit in which a resonance wiring is wound in the same phase as that of the resonance wiring and a resonance capacitor is connected between both ends of the resonance wiring.   2. The noise filter according to claim 1, wherein the capacitance of the capacitor between the ground is smaller than the capacitance of the resonant capacitor of the common mode coil with a resonant circuit.   The noise filter according to claim 1 or 2, wherein the inductance of the common mode coil with a resonance circuit is smaller than the inductance of the common mode coil having no resonance circuit.   The main circuit wiring connects between the AC power source and the power converter, and the winding inductance of the resonance wiring of the common mode coil with the resonant circuit and the capacity of the resonant capacitor depend on the switching carrier frequency in the power converter. The noise filter according to any one of claims 1 to 3, wherein the noise filter has a value corresponding to a resonance frequency.   5. A common mode coil with a resonance circuit, wherein a main circuit wiring and a resonance wiring are both wound around a magnetic core in the same phase, and a resonance capacitor is connected to both ends of the resonance wiring. The noise filter according to any one of the above.   One common mode coil and one common mode coil with a resonance circuit are combined into a first magnetic core and a second magnetic core extending in parallel, and a main circuit wiring combines the first and second magnetic cores. And the resonance wiring is wound in the same phase with one of the first and second magnetic cores as an axis, and a resonance capacitor is connected to both ends of the resonance wiring. The noise filter according to claim 1, wherein the noise filter is characterized in that:   At least one resonance circuit unit comprising a resonance wiring wound in the same phase with one of the magnetic core and the first and second magnetic cores as an axis and a resonance capacitor connected to both ends of the resonance wiring is added. The noise filter according to claim 5 or 6, characterized in that:   The main circuit wiring connects between the AC power supply and the power converter, and noise regulation is applied to the resonance frequency in the resonance circuit consisting of the winding inductance of the resonance wiring of the resonance mode common mode coil and the capacitance of the resonance capacitor. The noise filter according to any one of claims 1 to 3, wherein the noise filter is set between the lowest frequency and a frequency equal to or lower than a frequency at which the impedance phase of the common mode coil with a resonance circuit becomes 0 degrees.   The main circuit wiring connects between the AC power supply and the power converter, and noise regulation is applied to the resonance frequency in the resonance circuit consisting of the winding inductance of the resonance wiring of the resonance mode common mode coil and the capacitance of the resonance capacitor. The noise filter according to any one of claims 1 to 3, wherein the noise filter is set between the lowest frequency and a frequency at which a resistance component of the impedance of the common mode coil with a resonance circuit becomes a maximum value. .

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