JP2005204438A - Noise filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a noise filter that exerts a full restraint effect to EMI noise generated at a power converter and can significantly reduce the leakage current. <P>SOLUTION: The noise filter restrains the EMI noise caused at the power converter, and comprises a common mode current extraction circuit 9, that is connected to a power line at the output side of the power converter and has low impedance, with respect to a common mode current; interphase capacitors 7a, 7b and 7c connected to a power line at the input side of the power converter; and a common mode choke coil 6, inserted in series to an arbitrary position on a path reaching the common-mode current extracting circuit 9 from the interphase capacitors 7a, 7b and 7c via the power converter. The extraction point of the common-mode current generated at the common mode current extraction circuit 9 is connected to a neutral point, formed by the interphase capacitors. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a noise filter for suppressing leakage current and EMI noise generated by a switching operation of a switching element included in a power converter.

  For example, a power conversion device such as an inverter or a converter generates EMI noise (electromagnetic induction noise) due to a high-speed switching operation of a switching element incorporated therein. This EMI noise may adversely affect, for example, conduction to other devices having a common power supply and malfunction. For this reason, the EMI noise is regulated, and the EMI noise generated by the apparatus needs to satisfy this regulation value. Therefore, conventionally, a countermeasure is taken to suppress EMI noise by a noise filter.

  FIG. 9 is a circuit diagram showing the configuration of the simplest and general noise filter. Here, a case where the motor 4 is driven using an inverter device including the converter 1, the inverter 2, and the smoothing capacitor 3 will be described as an example.

  A high-frequency common mode current generated by switching of the switching element inside the inverter device reaches the motor 4 through the power line, and to the ground through a stray capacitance that exists between the winding of the motor and the ground. Flowing. When there is no noise filter, the common mode current returns from the ground to the power source 5 and returns to the inverter device. The common mode current flowing through the power supply 5 is observed as EMI noise in the common mode.

  Consider a case where a noise filter including a common mode choke coil 6, interphase capacitors 7a, 7b and 7c, and a ground capacitor 8 is attached between the power supply 5 and the inverter device. The common mode choke coil 6 exhibits a large impedance with respect to a common mode current which is a high frequency component flowing in the power supply line, and conversely, the impedance of the bypass circuit composed of the interphase capacitors 7a, 7b and 7c and the ground capacitor 8 is lowered. As a result, the common mode current flowing from the motor 4 to the ground returns to the inverter device through the low-impedance ground capacitor 8 and the interphase capacitors 7a, 7b and 7c, and the common mode EMI noise in the power source 5 is reduced. Interphase capacitors 7a, 7b and 7c act as a bypass circuit for high-frequency normal mode current which is another noise component generated in the inverter device. As a result, the EMI noise in the normal mode at the power source 5 is also reduced.

  As a related technique, Patent Document 1 discloses a noise reduction device and a power conversion device that stably reduce noise by reducing leakage current that flows from the power supply line to the ground line in the device and from the load. doing. In these noise reduction devices and power conversion devices, the zero-phase current transformer detects a leakage current propagating to the AC power supply line as a difference between currents flowing through the lines E1 and E2 on the power conversion circuit unit side rather than the capacitors. The detection ratio is 1. The detected current is induced in the secondary winding of the zero-phase current transformer, and the amplifier circuit amplifies this current. The amplification factor is 1. The noise reduction circuit unit supplies this current as a compensation current to the ground line through the capacitor in the opposite direction to the leakage current so as to cancel the leakage current. Since the amplification factor of the amplifier circuit is 1, oscillation or the like does not occur.

Further, Patent Document 2 discloses a leakage current suppression circuit in which even when a new refrigerant is used, the leakage current flowing through the housing is reduced so that the regulation value can be easily cleared. In this leakage current suppression circuit, a Zener diode is connected bidirectionally between the connection point of the two Y capacitors of the common mode filter and the housing so that a current flows only when a voltage higher than a predetermined voltage is applied. A current suppression circuit is formed in the slab to suppress the current flowing through the housing. In addition, the phase adjustment circuit is formed by optimally setting the values of the capacitance of the Y capacitor and the inductance of the common mode reactor coil so as to be substantially in phase with the current of the other path flowing into the housing. As a result, leakage current flowing from the housing to the ground is suppressed.
JP 2003-174777 A Japanese Patent Laid-Open No. 11-146557

  As described above, in the conventional noise filter, a bypass circuit having a low impedance is formed using a capacitor between the power line and the ground. For this reason, the impedance of the entire path through which the common mode current flows is lower than when no noise filter is present, and the leakage current from the motor increases conversely. This leakage current may adversely affect other equipment having a common ground, or may flow into the motor bearing and cause electric corrosion. Therefore, it is desired to suppress the EMI noise and reduce the leakage current as much as possible.

  The present invention has been made to meet the above-mentioned demands, and the problem is to provide a noise filter that has a sufficient suppression effect on the EMI noise generated by the power converter and can significantly reduce the leakage current. It is to provide.

  In order to achieve the above object, a noise filter according to a first aspect of the present invention is a noise filter that suppresses EMI noise generated in a power converter, and is a common connected to a power line on the output side of the power converter. Low-impedance common mode current extraction circuit for mode current, interphase capacitor connected to the power line on the input side of the power converter, and path from the interphase capacitor to the common mode current extraction circuit via the power converter The first common mode choke coil inserted in series at any position of the common mode current extraction circuit, the common mode current extraction point formed in the common mode current extraction circuit is connected to the neutral point formed by the interphase capacitor It is characterized by that.

  A noise filter according to a second aspect of the present invention is a converter that converts AC power from an input-side power line into DC power, and converts DC power output from the converter into AC power for output-side power lines. A noise filter for suppressing EMI noise generated in a power conversion device having an inverter for output, which is connected to an output side of a converter and a low impedance common mode current extraction circuit connected to a power line on the output side Two interphase capacitors connected in series, and a first common mode choke coil inserted in series at an arbitrary position in the path from the interphase capacitor to the common mode current extraction circuit via the inverter, The common mode current extraction point formed in the common mode current extraction circuit is a neutral point formed at the connection point of two interphase capacitors. Characterized in that it is connected to.

  According to a third aspect of the present invention, there is provided a converter for converting AC power from an input-side power line into DC power, and converting DC power output from the converter into AC power for output-side power lines. A noise filter that suppresses EMI noise generated in a power conversion device including an inverter that outputs to a low-impedance common-mode current extraction circuit connected to an output-side power line, and an output side of the converter One high-voltage interphase capacitor connected, a capacitor provided between one terminal of the interphase capacitors and the common mode current extraction point formed in the common mode current extraction circuit, and an interphase capacitor to an inverter The first common mode cho inserted in series at an arbitrary position in the path to the common mode current extraction circuit via Characterized in that a choke coil.

  The noise filter according to a fourth aspect of the present invention is the noise filter according to the first to third aspects, further comprising at least one of a path from the power source to the interphase capacitor or a path from the common mode current extraction circuit to the load. The second common mode choke coil is inserted.

  A noise filter according to a fifth invention is the noise filter according to the first to fourth inventions, wherein a normal mode noise removing interphase capacitor is further connected to the power supply line on the input side of the power converter. To do.

  A noise filter according to a sixth invention is the noise filter according to the first to fifth inventions, wherein the power converter has a three-phase output, and the common mode current extraction circuit is the same for each leg of the tripod core. A three-phase reactor with windings in the direction and a series circuit with a capacitor connected in series to each of the three windings of the three-phase reactor, and one end of the series circuit is connected to the output of the power converter The other ends of the three series circuits are connected at one place to form a common mode current extraction point.

  A noise filter according to a seventh aspect is the noise filter according to the first to fifth aspects, wherein the power conversion device has a three-phase output, and the common mode current extraction circuit is electromagnetically coupled via an iron core. Two windings belonging to a combination of any two phases among three windings of three single-phase reactors composed of two windings are connected in series so as to cancel the magnetic flux of the iron core against the common mode current. And a series circuit in which a capacitor is connected in series to two windings belonging to a combination of two phases, one end of the series circuit being connected to the output of the power converter, and the other of the three series circuits Are connected at one location to form a common mode current extraction point.

  The noise filter according to an eighth invention is the noise filter according to the first to fifth inventions, wherein the power converter has a single-phase output, and the common mode current extraction circuit has two windings in common. A single-phase reactor connected so as to cancel the magnetic flux of the iron core against the mode current, and two capacitors connected in series to the ends of the two windings of the single-phase reactor, The other end of the winding is connected at one point to form a common mode current extraction point.

  According to the noise filter of the first aspect of the invention, in addition to reducing the common mode current generated in the power converter by the first common mode choke coil, most of the common mode current flowing out to the power supply line has a low impedance common. Since the current flows through the circuit formed by the mode current extraction circuit and the interphase capacitor, the common mode current hardly flows to the ground or the power source. As a result, in addition to reducing EMI noise at the power source, the leakage current can be greatly reduced.

  According to the noise filter of the second invention, the interphase capacitor is provided on the output side of the converter, so that the common mode current flowing from the common mode current extraction circuit to the interphase capacitor is blocked by the converter and is prevented from flowing into the power supply. be able to. As a result, the common mode current extracted from the common mode current extraction circuit does not bypass the power supply, and EMI noise in the power supply can be further reduced.

  According to the noise filter according to the third aspect of the invention, the number of interphase capacitors having a relatively large shape can be reduced because the number of interphase capacitors that require a high breakdown voltage is one. As a result, the noise filter can be reduced in size.

  According to the noise filter of the fourth invention, since the second common mode choke coil is further inserted into at least one of the path from the power source to the interphase capacitor or the path from the common mode current extraction circuit to the load, the common mode current The impedance of the path through the power supply is further increased with respect to the common mode current bypass circuit including the extraction circuit and the interphase capacitor. As a result, the leakage current and EMI noise can be further reduced as compared with the noise filters according to the first to third inventions.

  According to the noise filter according to the fifth aspect of the present invention, since the noise removing interphase capacitor is further connected to the power supply line on the input side of the power converter, a bypass having a low impedance with respect to the normal mode current that flows to the power supply. A circuit is formed.

  According to the noise filter of the sixth aspect of the invention, the three-phase reactor of the common mode current extraction circuit exhibits a large inductance with respect to the normal mode current, so that almost no reactive current flows from the power converter. On the other hand, since there is almost no inductance with respect to the common mode current, only the common mode current can be selectively extracted.

  According to the noise filter of the seventh invention, as in the case of using the three-phase reactor, only the common mode current can be selectively extracted, and the leakage inductance can be reduced by devising the winding structure of the single-phase reactor. It is possible to suppress as much as possible.

  According to the noise filter according to the eighth aspect of the invention, in the single-phase output power converter, common mode current flowing through the ground and the power source can be reduced as in the case of the three-phase output.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following embodiments, the same or corresponding components will be described with the same reference numerals. Moreover, an inverter apparatus shall be used as a power converter device.

  FIG. 1 is a diagram illustrating a configuration of a drive circuit for driving a load by an inverter device to which a noise filter according to a first embodiment of the present invention is applied.

  The inverter device includes a converter 1, an inverter 2 and a smoothing capacitor 3. The input terminal of the converter 1 is connected to the power supply 5 through a common mode choke coil 6 and a power supply line which will be described later. The output terminal of the converter 1 is connected to the input terminal of the inverter 2. The converter 1 converts AC power supplied from the power source 5 through the input side power line and the common mode choke coil 6 into DC power and sends the DC power to the inverter 2.

  The input terminal of the inverter 2 is connected to the output terminal of the converter 1 as described above. An output terminal of the inverter 2 is connected to a motor 4 as a load and a common mode current extraction circuit 9 described later via a power supply line. The inverter 2 converts the DC power from the converter 1 into AC power, and supplies the AC power to the motor 4 via the power line on the output side. Smoothing capacitor 3 is connected between the output terminals of converter 1 (equal between the input terminals of inverter 2), and smoothes the DC power output from converter 1.

  The noise filter includes a common mode choke coil 6, interphase capacitors 7 a, 7 b and 7 c, and a common mode current extraction circuit 9. In the common mode choke coil 6, three windings 6 a to 6 c corresponding to three electric wires are electromagnetically coupled to each other, and are inserted in series in a power supply line connecting the power supply 5 and the converter 1.

  One terminal of the interphase capacitors 7a, 7b and 7c is connected to the three electric wires constituting the power supply line between the power source 5 and the common mode choke coil 6, and the other terminal is connected to one place. A neutral point is formed.

  The common mode current extraction circuit 9 is connected to the power line on the output side of the inverter 2 so as to be in parallel with the motor 4. The extraction point of the common mode current formed in the common mode current extraction circuit 9 is connected to the neutral point formed by the interphase capacitors 7a, 7b and 7c.

  In the drive circuit configured as described above, the impedance of the common mode current extraction circuit 9 with respect to the normal mode current is set to be sufficiently higher than the operation frequency of the motor 4 and the carrier frequency of the inverter device. This is to suppress the reactive current flowing from the inverter device into the common mode current extraction circuit 9 as much as possible.

  On the other hand, for the common mode current, the impedance of the circuit formed by the common mode current extraction circuit 9 and the interphase capacitors 7a, 7b and 7c is sufficiently higher than the impedance of the circuit formed by the motor 4, the ground and the power source 5. It is set to be low.

  As a result, the common mode current generated in the inverter device does not flow to the motor 4, the ground, and the power source 5, but flows to the circuit formed by the common mode current extraction circuit 9 and the interphase capacitors 7a, 7b, and 7c. In addition, since the common mode choke coil 6 showing high impedance with respect to the common mode current is attached to the power supply line between the interphase capacitors 7a, 7b, 7c and the common mode current extraction circuit 9, Leakage current and EMI noise at the power supply 5 are greatly reduced.

  In the configuration shown in FIG. 1, the common mode choke coil 6 is connected between the interphase capacitors 7a, 7b, and 7c and the inverter device. However, the interphase capacitors 7a, 7b, and 7c pass through the inverter device. It can be configured to be inserted at any position on the path to the common mode current extraction circuit 9, for example, between the output terminal of the inverter 2 and the common mode current extraction circuit 9, or between the converter 1 and the inverter 2.

  FIG. 2 is a diagram illustrating a configuration of a drive circuit for driving a load in an inverter device to which a noise filter according to a second embodiment of the present invention is applied.

  The inverter device includes a converter 1, an inverter 2 and a smoothing capacitor 3. The input terminal of the converter 1 is connected to the power supply 5 through a power supply line. The output terminal of the converter 1 is connected to the input terminal of the inverter 2 via a common mode choke coil 11 described later. The converter 1 converts AC power supplied from the power source 5 through the power line on the input side into DC power and supplies the DC power to the inverter 2 through the common mode choke coil 11. The common mode choke coil 11 is formed by electromagnetically coupling two windings 11a and 11b to each other.

  The input terminal of the inverter 2 is connected to the output terminal of the converter 1 via the common mode choke coil 11 as described above. An output terminal of the inverter 2 is connected to a motor 4 as a load and a common mode current extraction circuit 9 described later via a power supply line. The inverter 2 converts DC power supplied from the converter 1 via the common mode choke coil 11 into AC power, and supplies the AC power to the motor 4 via the power line on the output side. The smoothing capacitor 3 is connected between the input terminals of the inverter 2 and smoothes the DC power supplied from the converter 1 through the common mode choke coil 11.

  The noise filter includes interphase capacitors 10 a and 10 b, a common mode choke coil 11, and a common mode current extraction circuit 9. The interphase capacitor 10a and the interphase capacitor 10b are connected in series, and are connected between the output terminals of the capacitors. The connection point between the interphase capacitor 10a and the interphase capacitor 10b forms a neutral point.

  The common mode choke coil 11 is inserted in series in a line connecting the output terminal of the converter 1 and the input terminal of the inverter 2.

  The common mode current extraction circuit 9 is connected to the power line on the output side of the inverter 2 so as to be in parallel with the motor 4. A common mode current extraction point formed in the common mode current extraction circuit 9 is connected to a neutral point formed by the interphase capacitors 10a and 10b.

  In the configuration shown in FIG. 2, the common mode choke coil 11 is connected between the output terminals of the interphase capacitors 10a and 10b and the input terminal of the inverter 2, but the interphase capacitors 10a and 10b pass through the inverter 2. Then, it is configured to be inserted at an arbitrary position on the path to the common mode current extraction circuit 9, for example, between the output terminal of the inverter 2 and the common mode current extraction circuit 9, or between the smoothing capacitor 3 and the inverter 2. it can.

  In the drive circuit to which the noise filter according to the first embodiment described above is applied, a part of the common mode current flowing from the common mode current extraction circuit 9 to the interphase capacitors 7 a, 7 b and 7 c is bypassed to the power source 5. This is because there is a state that is not necessarily conducted in each phase of the converter 1, and in this state, the flow of current is blocked. For example, let us consider a case where the R phase and the S phase are conducting and the T phase is not conducting in the three-phase input. In this case, the T-phase current out of the current flowing to the power supply line through the interphase capacitors 7a, 7b and 7c cannot pass through the converter 1, but bypasses the power supply 5 and flows to the R-phase and S-phase and returns to the inverter 2. .

  On the other hand, in the drive circuit to which the noise filter according to the second embodiment is applied, the interphase capacitors 10a and 10b are provided between the converter 1 and the inverter 2, and therefore the common mode current extraction circuit 9 to the interphase capacitors 10a and 10b The common mode current flowing to 10 b returns directly to the inverter 2 without being blocked by the converter 1. As a result, since the common mode current does not bypass the power supply 5, the EMI noise observed by the power supply 5 can be greatly reduced.

  FIG. 3 is a diagram illustrating a configuration of a drive circuit for driving a load in an inverter device to which a noise filter according to a third embodiment of the present invention is applied.

  The inverter device includes a converter 1, an inverter 2 and a smoothing capacitor 3. The input terminal of the converter 1 is connected to the power supply 5 through a power supply line. The output terminal of the converter 1 is connected to the input terminal of the inverter 2 via a common mode choke coil 11 described later. The converter 1 converts AC power supplied from the power source 5 through the power line on the input side into DC power and supplies the DC power to the inverter 2 through the common mode choke coil 11.

  The input terminal of the inverter 2 is connected to the output terminal of the converter 1 via the common mode choke coil 11 as described above. An output terminal of the inverter 2 is connected to a motor 4 as a load and a common mode current extraction circuit 9 described later via a power supply line. The inverter 2 converts DC power supplied from the converter 1 via the common mode choke coil 11 into AC power, and supplies the AC power to the motor 4 via the power line on the output side. The smoothing capacitor 3 is connected between the input terminals of the inverter 2 and smoothes the DC power supplied from the converter 1 through the common mode choke coil 11.

  The noise filter includes a common mode current extraction circuit 9, a common mode choke coil 11, an interphase capacitor 12 and a capacitor 13. The interphase capacitor 12 is connected between the output terminals of the converter 1. The common mode choke coil 11 is inserted in series in a line connecting the output terminal of the converter 1 and the input terminal of the inverter 2.

  The common mode current extraction circuit 9 is connected to the power line on the output side of the inverter 2 so as to be in parallel with the motor 4. The capacitor 13 is connected between a common mode current extraction point formed in the common mode current extraction circuit 9 and a negative output terminal of the converter 1 (a negative input terminal of the inverter 2).

  In the configuration shown in FIG. 3, the common mode choke coil 11 is connected between the output terminal of the interphase capacitor 12 and the input terminal of the inverter 2. However, the common mode choke coil 11 is connected to the common mode via the inverter 2 from the interphase capacitor 12. It can be configured to be inserted at any position on the path leading to the current extraction circuit 9, for example, between the output terminal of the inverter 2 and the common mode current extraction circuit 9, or between the smoothing capacitor 3 and the inverter 2.

  According to the noise filter according to the third embodiment configured as described above, the noise filter can be configured at low cost because only one interphase capacitor 12 requiring high breakdown voltage is required. Further, since the capacitor 13 can be a small capacitor having a low withstand voltage, the noise filter can be downsized as a whole.

  FIG. 4 is a diagram illustrating a configuration of a drive circuit for driving a load in an inverter device to which a noise filter according to a fourth embodiment of the present invention is applied.

  In this drive circuit, a common mode choke coil 14 is inserted into a power line connecting the power source 5 and the converter 1 in a drive circuit that drives a load with an inverter device to which the noise filter according to the second embodiment shown in FIG. 2 is applied. Has been configured.

  The common mode choke coil 14 is formed by electromagnetically coupling the three windings 14 a to 14 c, and functions to increase the impedance of a leakage current path formed from the motor 4, the ground, and the power source 5.

  According to the noise filter according to the fourth embodiment, the leakage current from the motor 4 and the EMI noise in the power source 5 can be further reduced as compared with the noise filter according to the second embodiment.

  In the configuration shown in FIG. 4, the common mode choke coil 14 is inserted in the path from the power supply 5 to the interphase capacitors 10 a and 10 b, and this common mode choke coil 14 extends from the common mode current extraction circuit 9 to the motor 4. Can be configured to be inserted into the path. Alternatively, the common mode choke coil can be inserted into both the path from the power supply 5 to the interphase capacitors 10 a and 10 b and the path from the common mode current extraction circuit 9 to the motor 4.

  In the drive circuit for driving the load with the inverter device to which the noise filter according to the first embodiment shown in FIG. 1 is applied, the path from the power source 5 to the interphase capacitors 7a, 7b and 7c and the common mode current extraction circuit 9 The common mode choke coil can be inserted into at least one of the paths from the motor 4 to the motor 4. In the drive circuit that drives the load with the inverter device to which the noise filter according to the third embodiment shown in FIG. 3 is applied, the path from the power source 5 to the interphase capacitor 12 and the common mode current extraction circuit 9 to the motor 4 The common mode choke coil can be inserted into at least one of the paths leading to.

  FIG. 5 is a diagram illustrating a configuration of a drive circuit for driving a load in an inverter device to which a noise filter according to a fifth embodiment of the present invention is applied.

  This drive circuit is a drive circuit for driving a load with an inverter device to which the noise filter according to the second embodiment shown in FIG. 2 is applied. In this drive circuit, three power lines constituting a power line connecting the power source 5 and the converter 1 are connected. One terminal of the interphase capacitors 15a, 15b and 15c is connected to each other, and the other terminal of the interphase capacitors 15a, 15b and 15c is connected to one place. Interphase capacitors 15a, 15b and 15c serve to bypass the high frequency components of normal mode current flowing to power supply 5.

  According to the noise filter according to the fifth embodiment, normal mode noise is not conducted to the power supply 5, so that EMI noise in the power supply 5 can be reduced.

  In the noise filter according to the fifth embodiment, the interphase capacitors 15a, 15b, and 15c are connected to the path from the power source 5 to the converter 1. However, in the noise filters according to the first to fourth embodiments as well, Interphase capacitors 15a, 15b and 15c can be connected to the path leading to converter 1. In these cases, the same effects as described above are obtained.

  FIG. 6 is a diagram showing the structure of the common mode current extraction circuit 9 constituting the noise filter according to the sixth embodiment of the present invention.

  The common mode current extraction circuit 9 includes a three-phase reactor 16 and capacitors 17a, 17b and 17c. Three windings 16a2 to 16c2 are wound around the tripod iron cores 16a1 to 16c1 constituting the three-phase reactor 16 in the same direction. One end of each of the three windings 16a2 to 16c2 is connected to capacitors 17a, 17b and 17c connected to the power line on the output side of the inverter 2, and the other end of each of the three windings 16a2 to 16c2 is 1 They are connected at different points to form the extraction point for common mode current.

  The three-phase reactor 16 configured as described above exhibits a large inductance because the magnetic fluxes generated in the respective phases strengthen each other with respect to the normal mode current. On the other hand, the common mode current flowing through each phase generates the same magnitude of magnetic flux in the same direction on each leg of the iron core. For this reason, the magnetic flux in the iron core does not change in a balanced manner, and does not represent inductance for the common mode current. As a result, only the common mode current flows through the common mode current extraction circuit 9, and the common mode current flowing from the power supply line flows out from the common mode current extraction point.

  According to the noise filter according to the sixth embodiment, the three-phase reactor 16 of the common mode current extraction circuit 9 exhibits a large inductance with respect to the normal mode current, so that the reactive current from the power converter hardly flows. On the other hand, since there is almost no inductance with respect to the common mode current, only the common mode current can be selectively extracted.

  If a large impedance is to be secured only by the three-phase reactor 16 with respect to the low-frequency normal mode current for driving the motor 4, the common mode current extraction circuit 9 becomes very large and is not practical. Capacitors 17a, 17b and 17c cut such a low frequency normal mode current. With this configuration, the common mode current extraction circuit 9 can be suppressed to a practical size.

  In order to avoid a failure due to resonance, the resonance frequency of the three-phase reactor 16 and the capacitors 17a, 17b and 17c with respect to the normal mode current is higher than the operation frequency of the motor 4, and conversely lower than the switching frequency of the inverter device. Is set. In addition, when the resonance frequency is high, the iron core of the three-phase reactor 16 is less likely to be magnetically saturated. Therefore, it is preferable to increase the switching frequency in order to reduce the size.

  Further, since the leakage inductance actually exists in the three-phase reactor 16, this acts on the common mode current. The frequency of LC resonance in the path formed by this leakage inductance, the capacitors 17a, 17b and 17c, and the capacitor connected to the common mode current extraction point of the common mode current extraction circuit 9 is the leakage current and EMI to be reduced most. If the noise frequency is set, a greater reduction effect of leakage current and EMI noise is exhibited.

  Of course, the same effect can be obtained even if the three-phase reactor 16 and the capacitors 17a, 17b, and 17c shown in FIG. 6 are replaced.

  FIG. 7 is a diagram showing the structure of the common mode current extraction circuit 9 constituting the noise filter according to the seventh embodiment of the present invention.

  The common mode current extraction circuit 9 includes three single-phase reactors 18a, 18b and 18c and capacitors 17a, 17b and 17c. The single-phase reactor 18a is composed of two windings 18a1 and 18a2 that are electromagnetically coupled via an iron core 18a3. The single-phase reactor 18b is composed of two windings 18b1 and 18b2 that are electromagnetically coupled via an iron core 18b3. The single-phase reactor 18c includes two windings 18c1 and 18c2 that are electromagnetically coupled via an iron core 18c3. The winding 18a1 and the winding 18c2 are connected in series, the winding 18b1 and the winding 18a2 are connected in series, and the winding 18c1 and the winding 18b2 are connected in series.

  That is, each of the three single-phase reactors 18a, 18b and 18c has three winding pairs in which two windings belonging to a combination of two arbitrary phases in three phases are connected in series. And the single-phase reactors 18a, 18b and 18c do not exhibit inductance by canceling out the magnetic flux of the iron core with respect to the common mode current.

  One end of each of the three winding pairs is connected to capacitors 17a, 17b and 17c, and the other end is connected at one point to form a common mode current extraction point.

  According to the noise filter according to the seventh embodiment of the present invention including the common mode current extraction circuit 9 configured as described above, the same operations and effects as the noise filter according to the sixth embodiment are exhibited. Further, when the common mode current extraction circuit 9 is composed of the single-phase reactors 18a, 18b and 18c, it is possible to suppress leakage inductance as much as possible by winding two windings on the same iron core. 9 performance can be further improved.

  FIG. 8 is a diagram showing the structure of the common mode current extraction circuit 9 constituting the noise filter according to the eighth embodiment of the present invention.

  The common mode current extraction circuit 9 includes a single-phase reactor 19 and capacitors 20a and 20b. The single-phase reactor 19 is wound with a winding so as not to exhibit inductance with respect to the common mode current. One end of each of the two windings is connected to capacitors 20a and 20b, respectively, and the other end is connected at one place to form a common mode current extraction point. The single-phase reactor 19 includes two windings 19a and 19b that are electromagnetically coupled via an iron core 19c. The two windings 19a and 19b are wound so that opposite phase voltages are generated.

  According to the noise filter according to the eighth embodiment of the present invention including the common mode current extraction circuit 9 configured as described above, the same operation and effect as the three-phase noise filter according to the sixth and seventh embodiments. Play.

  The present invention is applicable to an inverter device including a converter and an inverter.

It is a figure which shows the structure of the drive circuit for driving a load with the inverter apparatus to which the noise filter which concerns on Example 1 of this invention was applied. It is a figure which shows the structure of the drive circuit for driving a load with the inverter apparatus to which the noise filter which concerns on Example 2 of this invention was applied. It is a figure which shows the structure of the drive circuit for driving a load with the inverter apparatus to which the noise filter which concerns on Example 3 of this invention was applied. It is a figure which shows the structure of the drive circuit for driving a load with the inverter apparatus to which the noise filter which concerns on Example 4 of this invention was applied. It is a figure which shows the structure of the drive circuit for driving a load with the inverter apparatus to which the noise filter which concerns on Example 5 of this invention was applied. It is a figure which shows the structure of the common mode current extraction circuit which comprises the noise filter which concerns on Example 6 of this invention. It is a figure which shows the structure of the common mode current extraction circuit which comprises the noise filter which concerns on Example 7 of this invention. It is a figure which shows the structure of the common mode current extraction circuit which comprises the noise filter which concerns on Example 8 of this invention. It is a figure for demonstrating the conventional noise filter.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Converter 2 Inverter 3 Smoothing capacitor 4 Motor 5 Power supply 6 Common mode choke coils 7a, 7b, 7c Interphase capacitor 8 Grounding capacitor 9 Common mode current extraction circuit 10a, 10b Interphase capacitor 11 Common mode choke coil 12 Interphase capacitor 13 Capacitor 14 Common mode Choke coils 15a, 15b, 15c Interphase capacitor 16 Three-phase reactors 17a, 17b, 17c Capacitors 18a, 18b, 18c Single-phase reactor 19 Single-phase reactors 20a, 20b Capacitors

Claims (8)

A noise filter for suppressing EMI noise generated in a power converter,
A common mode current extraction circuit having a low impedance with respect to the common mode current connected to the power line on the output side of the power converter;
An interphase capacitor connected to the power line on the input side of the power converter;
A first common mode choke coil inserted in series at an arbitrary position in the path from the interphase capacitor to the common mode current extraction circuit via the power converter,
A noise filter, wherein a common mode current extraction point formed in the common mode current extraction circuit is connected to a neutral point formed by the interphase capacitor. A power converter comprising a converter that converts AC power from an input power line into DC power, and an inverter that converts DC power output from the converter into AC power and outputs the AC power to an output power line A noise filter for suppressing generated EMI noise,
A low impedance common mode current extraction circuit connected to the output power line;
Two series connected interphase capacitors connected to the output side of the converter;
A first common mode choke coil inserted in series at an arbitrary position in the path from the interphase capacitor to the common mode current extraction circuit via the inverter;
A noise filter characterized in that a common mode current extraction point formed in the common mode current extraction circuit is connected to a neutral point formed at a connection point of the two interphase capacitors. A power converter comprising a converter that converts AC power from an input power line into DC power, and an inverter that converts DC power output from the converter into AC power and outputs the AC power to an output power line A noise filter for suppressing generated EMI noise,
A low impedance common mode current extraction circuit connected to the output power line;
One high withstand voltage interphase capacitor connected to the output side of the converter;
A capacitor provided between one terminal of the interphase capacitor and a common mode current extraction point formed in the common mode current extraction circuit;
A first common mode choke coil inserted in series at an arbitrary position in a path from the interphase capacitor to the common mode current extraction circuit via the inverter;
A noise filter characterized by comprising:   4. The second common mode choke coil is further inserted in at least one of a path from a power source to the interphase capacitor or a path from the common mode current extraction circuit to a load. The noise filter according to any one of claims.   5. The noise filter according to claim 1, wherein a normal mode noise eliminating interphase capacitor is further connected to a power supply line on an input side of the power converter. 6. The power converter has a three-phase output;
The common mode current extraction circuit includes:
A series circuit of a three-phase reactor in which the legs of the tripod core are wound in the same direction and a capacitor connected in series to each of the three windings of the three-phase reactor, and one of the series circuits The end is connected to the output of the power converter,
The noise filter according to any one of claims 1 to 5, wherein the other end of the three series circuits is connected at one place to form a common mode current extraction point. . The power converter has a three-phase output;
The common mode current extraction circuit includes:
Of the three single-phase reactor windings that consist of two windings that are electromagnetically coupled via an iron core, two windings belonging to a combination of any two phases generate the magnetic flux of the iron core against the common mode current. A series circuit in which capacitors are connected in series to two windings belonging to the combination of the two phases, and one end of the series circuit is connected to the output of the power conversion device. Connected,
6. The noise filter according to claim 1, wherein the other end of the three series circuits is connected at one place to form a common mode current extraction point. . The power converter has a single phase output,
The common mode current extraction circuit includes:
A single-phase reactor in which two windings are connected so as to cancel the magnetic flux of the iron core against the common mode current;
Two capacitors respectively connected in series to the ends of the two windings of the single-phase reactor,
6. The noise filter according to claim 1, wherein the other ends of the two windings are connected at one place to form a common mode current extraction point. .

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