JP6650109B2 - Noise filter - Google Patents

Description

  The present invention relates to a noise filter for reducing electromagnetic noise generated in a power converter or the like.

Power conversion devices, such as inverters and converters, in which power semiconductor elements such as IGBTs and MOSFETs perform high-speed switching of several [kHz] to several hundred [kHz] to convert voltage and current, have high efficiency, small size, light weight, etc. Due to the merits of this, its spread is rapidly expanding.
However, high-speed switching for performing power conversion causes electromagnetic noise, and electromagnetic noise disturbance to peripheral devices is a major problem.

  In order to prevent the above-described electromagnetic noise interference, the power conversion device is generally provided with a noise filter, and the function of the noise filter reduces the electromagnetic noise flowing to the outside. In addition, laws and regulations on electromagnetic noise, which began in Europe, are spreading around the world. Conducted noise (noise terminal voltage) and radiated noise (radiated electric field strength), which are subject to regulation, are reduced in the usage environment of power converters. The level to be decided is clear.

However, even in a power converter that satisfies a predetermined standard, electromagnetic noise interference may occur in the field. This is because the influence on the peripheral devices of the power converter greatly differs depending on the use environment.
If the peripheral device is a device with low noise resistance (a device that easily malfunctions such as a high-sensitivity measuring device), or if a measuring device is arranged in the immediate vicinity of the power converter, the power converter is the most severe. Even if the standard (for example, CISPR22, ClassB) is cleared, electromagnetic noise interference may occur.

  Further, the noise filter of the power converter generally includes a reactor (common mode choke coil), a line capacitor, and a ground capacitor. However, there is an obstacle generated by adding the noise filter. For example, cases where the leakage current flowing through the grounding capacitor increases and the earth leakage breaker responds, and cases where excessive noise current (common mode current) flows through the common mode choke coil causing overheating and burning of the choke coil This kind of overheating / burnout accident may occur, for example, in the following motor variable speed drive system.

FIG. 7 shows an overall configuration of a variable speed drive system that drives a three-phase AC motor (hereinafter simply referred to as a motor) by a three-phase inverter.
7, reference numeral 10 denotes a three-phase AC power supply, reference numeral 20 denotes an input cable, reference numeral 30 denotes a noise filter shown in FIG. 8, which will be described later, reference numeral 40 denotes a three-phase inverter including a diode rectifier circuit 41, a smoothing capacitor _Cdc, and an inverter unit 42. 50 is an output cable, 60 is a motor. _{Incidentally,} S 1 to S ₆ is a semiconductor switching element such as an IGBT.

Here, the noise filter 30 is configured, for example, as shown in FIG. This noise filter 30 is what is known as a so-called π-type filter.
8, a common mode choke coil 31 composed of coils 31R, 31S, 31T is connected between input / output terminals R, R ', S, S', T, T 'of each phase of the noise filter 30. .

Also, between the input terminal R, S, T side and the ground line 32 of the common mode choke coil 31 (E, E _in represents a ground terminal), the first line between the condenser 33 first grounding capacitor 34 and a first filter switch 35 are connected in series, and a second line capacitor 36 is connected between the output terminals R ′, S ′, T ′ of the common mode choke coil 31 and the ground line 32. A second grounding capacitor 37 and a second filter switch 38 are connected in series. 33R, 33S, 33T, 36R, 36S, 36T are capacitors constituting the line capacitors 33, 36, respectively.

The above-described noise filter 30 mainly flows into the ground line 32 via the stray capacitance formed in the output cable 50 and the motor 60 when the three-phase inverter 40 is driven, and flows into the common mode current (high-frequency leakage The stray capacitance formed in the output cable 50 increases and the common mode current increases as the output cable 50 becomes longer.
Depending on the field in which the variable speed drive system is installed, the output cable 50 may be laid beyond the allowable length described in the instruction manual or the like. Excessive common mode current may flow, resulting in overheating and burning.

  In order to avoid the occurrence of such a failure, it is necessary to use an external type noise filter so that it can be replaced with a product compatible with a large current, or to use a filter switch shown in FIG. It is conceivable to enable or disable the filter function by turning on and off 35 and 38.

  For example, Patent Literature 1 describes a power conversion device including a filter switch having the same function as that of FIG. In this patent document 1, the filter function can be enabled / disabled by turning on / off the filter switch, thereby eliminating the complicated work involved in replacing the noise filter. Turning off the filter switch causes excessive leakage current. The occurrence is prevented, and the earth leakage breaker is prevented from responding.

JP 2012-228021 A (paragraphs [0023] and [0024], FIG. 3 and the like)

  However, if the filter function is disabled by turning off the filter switch, the amount of noise flowing out of the power converter will increase, causing new malfunctions such as malfunction of peripheral devices and overheating and burning of the common mode choke coil. There is a concern that Further, since the filter switch has only a function of switching the validity / invalidity of the filter function, if an electromagnetic noise disturbance occurs when the filter function is valid, a new noise suppression component must be added.

  In view of the above, an object of the present invention is to provide a noise filter that not only switches the validity / invalidity of a filter function but also prevents overheating and burning of a common mode choke coil and implements appropriate measures against electromagnetic noise disturbance in a field. Is to provide.

In order to solve the above problem, the invention according to claim 1 connects a first line capacitor composed of a plurality of capacitors to an input side of a common mode choke coil, and connects a plurality of capacitors to an output side of the common mode choke coil. A second line capacitor composed of a capacitor, a first ground capacitor connected between a neutral point of the first line capacitor and a ground line, and a second line capacitor of the second line capacitor. In a π-type noise filter configured by connecting a second ground capacitor between a neutral point and the ground line,
Providing a first switching connection between the first grounding capacitor and the grounding line, and providing a second switching connection between the second grounding capacitor and the grounding line;
A third switching connection is provided between a connection point between the first grounding capacitor and the first switching connection and a connection point between the second grounding capacitor and the second switching connection. It is provided.

According to a second aspect of the present invention, a first line capacitor including a plurality of capacitors is connected to an input side of a common mode choke coil, and a second line including a plurality of capacitors is connected to an output side of the common mode choke coil. A first ground capacitor is connected between a neutral point of the first line capacitor and a ground line, and a neutral point of the second line capacitor is connected to the ground line. In a π-type noise filter configured by connecting a second ground capacitor between
A first switching connection is provided between a neutral point of the first line capacitor and the first grounding capacitor, and a neutral point of the second line capacitor is connected to the second grounding capacitor. Rutotomoni providing the second opening and closing the connecting portion between the capacitor,
A connection point between the neutral point of the first line capacitor and the first switching connection, and a connection point between the neutral point of the second line capacitor and the second switching connection. A third opening / closing connection portion is provided between them.

According to a third aspect of the present invention, a first line capacitor including a plurality of capacitors is connected to an input side of a common mode choke coil, and a second line including a plurality of capacitors is connected to an output side of the common mode choke coil. A first ground capacitor is connected between a neutral point of the first line capacitor and a ground line, and a neutral point of the second line capacitor is connected to the ground line. In a π-type noise filter configured by connecting a second ground capacitor between
A first switching connection is provided between a neutral point of the first line capacitor and the first grounding capacitor , and a neutral point of the second line capacitor is connected to the second grounding capacitor. A second switching connection is provided between the capacitor and the capacitor ,
A third switching connection for connecting a connection point between the first switching connection and the first grounding capacitor and a neutral point of the second line capacitor is provided.

According to a fourth aspect of the present invention, a first line capacitor including a plurality of capacitors is connected to an input side of a common mode choke coil, and a second line including a plurality of capacitors is connected to an output side of the common mode choke coil. A first ground capacitor is connected between a neutral point of the first line capacitor and a ground line, and a neutral point of the second line capacitor is connected to the ground line. In a π-type noise filter configured by connecting a second ground capacitor between
A first switching connection is provided between a neutral point of the first line capacitor and the first grounding capacitor, and a neutral point of the second line capacitor is connected to the second grounding capacitor. A second switching connection is provided between the capacitor and the capacitor,
A third switching connection for connecting a connection point between the second switching connection and the second grounding capacitor and a neutral point of the first line capacitor is provided.

According to a fifth aspect of the present invention, a first line capacitor including a plurality of capacitors is connected to an input side of a common mode choke coil, and a second line including a plurality of capacitors is connected to an output side of the common mode choke coil. A first ground capacitor is connected between a neutral point of the first line capacitor and a ground line, and a neutral point of the second line capacitor is connected to the ground line. In a π-type noise filter configured by connecting a second ground capacitor between
Providing a switching connection between the neutral point of the first line capacitor and the first ground capacitor;
Before a connection point between KiHiraki closed connecting portion and the first grounding capacitor, between the neutral point of the second line between the capacitors, as said opening and closing the connecting portion having a different opening and closing the connecting portion It is.

  According to the present invention, the line capacitor and the ground capacitor connected to the input side and the output side of the common mode choke coil can be separated, and the neutral points of these line capacitors can be connected to each other. Thus, it is possible to prevent overheating and burning of the common mode choke coil, and to take appropriate measures against electromagnetic noise disturbance in the field where the power converter and the like are installed.

FIG. 1 is a circuit diagram illustrating a configuration of a first exemplary embodiment of the present invention. FIG. 4 is a circuit diagram illustrating a configuration of a second exemplary embodiment of the present invention. FIG. 10 is a circuit diagram illustrating a use state of the second embodiment of the present invention. FIG. 10 is a circuit diagram illustrating a use state of the second embodiment of the present invention. FIG. 10 is a circuit diagram illustrating a use state of the second embodiment of the present invention. It is a circuit diagram showing a third embodiment of the present invention. 1 is an overall configuration diagram of a motor variable speed drive system using a three-phase inverter. It is a block diagram of the noise filter in FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a configuration diagram of a noise filter 30A according to the first embodiment of the present invention, and corresponds to the first aspect of the present invention. In the following embodiments, those having the same functions as those in FIG. 8 are denoted by the same reference numerals as those in FIG.

  The first embodiment of FIG. 1 is different from that of FIG. 8 in that a connection point between a first ground capacitor 34 and a first filter switch 35 and a connection between a second ground capacitor 37 and a second filter switch 38 are provided. The point where the third filter switch 39 is connected between the points. By turning on the filter switch 39, overheating and burning of the common mode choke coil 31 can be prevented.

  Here, the first, second, and third filter switches 35, 38, and 39 correspond to first, second, and third opening / closing connectors in claims, respectively. These first, second, and third opening / closing connection sections may be configured by arranging switches fixedly, or, as described later, a short-circuiting piece and a pair of connection points that can be short-circuited by the short-circuiting piece. May be used.

  In FIG. 1, when the filter switches 39 are turned on after the filter switches 35 and 38 are turned off, a bypass path of the common mode choke coil 31 is formed by the line capacitors 33 and 36 and the ground capacitors 34 and 37. For this reason, the common mode current which causes overheating and burning of the common mode choke coil 31 flows by bypass to the line capacitors 33 and 36, so that the common mode current hardly flows through the common mode choke coil 31. Thus, it is possible to prevent an excessive current from flowing through the common mode choke coil 31 and prevent overheating and burning.

  The filter switches 35 and 38 are respectively constituted by a short-circuiting piece and a pair of connection points which can be short-circuited by the short-circuiting piece. After removing one of the short-circuiting pieces, a portion corresponding to the filter switch 39 of FIG. When the pair of connection points provided in the above is short-circuited, it is not necessary to provide an independent component as the filter switch 39.

Next, FIG. 2 is a basic configuration diagram of a noise filter 30B according to a second embodiment of the present invention.
The second embodiment differs from FIG. 8 in the connection positions of the filter switches 35 and 38. That is, in FIG. 8, the filter switches 35 and 38 are connected between the ground capacitors 34 and 37 and the ground line 32, respectively. However, in the second embodiment, the filter switches 35 and 38 are connected between the line capacitors 33 and 36. Are connected between the respective neutral points and the ground capacitors 34 and 37, respectively.

In general, the components constituting the noise filter can be more concentratedly arranged at one place to obtain a large noise reduction effect. Therefore, as shown in FIG. 2, the filter switches 35 and 38 are provided between the line capacitor and the ground capacitor. Is not common.
However, in the first embodiment of FIG. 1, the line capacitors 33 and 36 and the ground capacitors 34 and 37 are connected in series by turning on the filter switch 39, whereas in the second embodiment of FIG. By separating (turning on) the filter switch 39 as shown in FIG. 3 after separating the line capacitors 33 and 36 from the ground capacitors 34 and 37 by the filter switches 35 and 38, respectively, a bypass path of the common mode current is provided. Only the line capacitors 33 and 36 are connected in series via the filter switch 39.
Thereby, the impedance of the bypass path of the common mode current is smaller than that of the first embodiment, and the effect of preventing the common mode choke coil 31 from overheating and burning can be further enhanced.

  More specifically, in the second embodiment, not only the number of series-connected capacitors in the bypass path of the common mode current is reduced, but also, as a design technique, the electrostatic capacitance of the line capacitors 33 and 36 is reduced rather than the ground capacitors 34 and 37. Generally, the capacity is larger. This is because a common mode filter is formed by the leakage inductance of the common mode choke coil 31 and the ground capacitors 34 and 37, whereas a normal mode filter is formed by the leakage inductance of the common mode choke coil 31 and the line capacitors 33 and 36. The resonance frequency of each filter is set to a substantially similar value (around several tens [kHz]). Here, since the leakage inductance of the common mode filter 31 is very small, the resonance frequency of both filters is set to be substantially the same by making the capacitance of the line capacitors 33, 36 larger than the capacitance of the ground capacitors 34, 37. ing.

That is, as shown in the noise filter 30C of FIG. 3, when only the line capacitors 33 and 36 are connected in series to the bypass path via the filter switch 39, the static mode connected in parallel with the common mode choke coil 31 is achieved. Since the capacitance is increased, more common mode current can be bypassed to the line capacitors 33 and 36. As a result, the common mode current flowing through the common mode choke coil 31 is reduced, so that the possibility of overheating and burning of the common mode choke coil 31 is reduced.
The noise filter 30C in FIG. 3 corresponds to the second aspect of the present invention.

  Also in the second embodiment, the filter switches 35 and 38 are each configured by a short-circuiting piece and a pair of connection points that can be short-circuited by the short-circuiting piece. If a pair of connection points provided at a portion corresponding to the filter switch 39 in FIG. 3 is short-circuited by using, there is no need to provide an independent component as the filter switch 39.

4 and 5, when an electromagnetic noise disturbance occurs in the field, the filter configuration can be rearranged so as to obtain a desired noise reduction effect without adding a new noise filter. it can.
That is, FIG. 4 shows an example in which the filter switch 39 is connected between the connection point between the filter switch 35 and the ground capacitor 34 and the neutral point of the line capacitor 36 to form the noise filter 30D. Is an example in which a filter switch 39 is connected between a neutral point of the line capacitor 33 and a connection point between the filter switch 38 and the ground capacitor 37 to form the noise filter 30E.
These noise filters 30D and 30E correspond to the invention according to claims 3 and 4 , respectively.
In any case, the filter switches 35 and 38 are configured by short-circuit pieces, one of the short-circuit pieces is removed, and a pair of connection points provided at a portion corresponding to the filter switch 39 in FIG. 4 or FIG. What is necessary is just to short-circuit.

The connection configuration shown in FIGS. 4 and 5 becomes possible because a general noise filter is designed to satisfy the standard. This type of standard requires conducted noise (noise terminal voltage) of 150 [kHz] to 30 [MHz] and radiation noise (radiation of 30 [MHz] to 1 [GHz] (up to 6 [GHz]). In general, a noise filter is designed so that noise can be reduced as a whole in such a wide frequency band.
That is, in the conventional noise filter 30 shown in FIG. 8, the ground capacitors 34 and 37 connected on both sides of the common mode choke coil 31 have different frequency bands to be reduced.

  More specifically, the combination of the common mode choke coil 31 and the second ground capacitor 37 reduces noise of about 1 [MHz] or less, whereas the first ground capacitor 34 Combination with the wiring inductance of the input cable 20 is effective in reducing noise of about 1 [MHz] or more (standard is 5 [MHz] or less).

However, when an electromagnetic noise disturbance occurs in the field, it is rare that the electromagnetic noise is caused by an electromagnetic noise occurring in a wide frequency band of 150 [kHz] to 30 [MHz]. That is, usually, in most cases, electromagnetic interference in a narrow frequency band occurs in combination with a peripheral device that is causing a failure.
For example, in the case where noise is mixed into AM radio, electromagnetic noise in a frequency band of 531 [kHz] to 1602 [kHz] becomes a problem. Alternatively, peripheral devices may malfunction due to electromagnetic noise generated below 150 kHz that is not subject to regulation. That is, the electromagnetic noise disturbance occurs due to a combination of a power conversion device such as an inverter and peripheral devices affected by the power conversion device.

  Therefore, the installation location of the third filter switch 39 is selected so that the circuit shown in FIG. 4 is configured, the first filter switch 35 is turned off, and the second and third filter switches 38 and 39 are turned on. Electromagnetic noise in a frequency band of 1 [MHz] or less can be reduced more than in the case of FIG.

  In addition, when the installation location of the third filter switch 39 is selected so that the circuit shown in FIG. 5 is configured, the reduction amount of the electromagnetic noise of about 1 [MHz] or less described above is reduced, but the 1 [MHz] is reduced. ] The electromagnetic noise in the above frequency band is reduced. Generally, measures against noise in the frequency band of 5 [MHz] or more largely depend on the arrangement of components and the like, and are difficult to obtain by theoretical calculation. However, in the configuration of FIG. 5, by turning on the filter switches 35 and 39 and consolidating the ground capacitors 34 and 37 on the power supply side, it is expected that electromagnetic noise can be reduced by specializing in high frequencies.

In the second embodiment shown in FIGS. 2 to 5 described above, except for the installation location of the third filter switch 39 and the on / off state of the third filter switch 39, the first and second line capacitors 33 and 36, the first , The second filter switches 35 and 38, and the first and second ground capacitors 34 and 37 have the same connection configuration.
In other words, by turning on or off the portion corresponding to the third filter switch 39 using the short-circuiting pieces constituting the first and second filter switches 35 and 38, all of the components shown in FIGS. A circuit is configured.
Therefore, the noise filters 30B, 30C, 30D, and 30E in FIGS. 2 to 5 can be configured using common components, and the problem to be dealt with most (about 1 [MHz] when protecting the common mode choke coil). In order to reduce the following electromagnetic noise, the configuration may be selected according to the case of reducing the electromagnetic noise of 1 [MHz] or more. The configuration in which the switches 35 and 38 are turned on and the switches 39 are turned off does not impair the noise reduction effect. Therefore, the conventional design of the filter (determination of the circuit constant) is not adversely affected.

Next, FIG. 6 is a configuration diagram showing a third embodiment of the present invention, and corresponds to the fifth aspect of the present invention. The noise filter 30F according to the third embodiment corresponds to a configuration in which the second filter switch 38 is removed from the noise filter 30D in FIG.

That is, in the third embodiment shown in FIG. 6, the operation of the first and third filter switches 35 and 39 integrates the π-type filter having the basic configuration and the ground capacitors 34 and 37 on the inverter 40 side. (The filter switch 35 is turned off, the filter switch 39 is turned on), and the configuration for preventing the common mode choke coil 31 from overheating and burning. (The filter switches 35 and 39 are turned on). Further, if both the filter switches 35 and 39 are turned off, the ground capacitor 34 can be separated from the ground line 32, so that the leakage current can be reduced.
However, as shown in FIGS. 2 to 5, all the ground capacitors cannot be separated from the ground line, so the effect of reducing the leakage current can be said to be limited. However, there is an advantage that the number of filter switches can be constituted by two. is there.

Note that each of the embodiments described above relates to a noise filter connected to a three-phase AC circuit, but the present invention is also applicable to a case where the noise filter is connected to a single-phase AC circuit.
Further, the same effect can be obtained when a part or all of the noise filter according to the present invention is connected to a DC intermediate circuit (for example, a connection point of the smoothing capacitor _Cdc in FIG. 7) of the power converter. .
In addition, in each embodiment, a noise filter built in the variable speed drive system is assumed, but the present invention is also applicable to an external type noise filter.

  INDUSTRIAL APPLICABILITY The present invention can be used for various power conversion devices and power supply devices that drive loads such as electric motors by inverters, converters, and the like.

10: three-phase AC power supply 20: input cables 30A, 30B, 30C, 30D, 30E, 30F: noise filter 31: common mode choke coil 31R, 31S, 31T: coil 32: ground wire 33, 36: line capacitor 33R, 33S, 33T, 36R, 36S, 36T: Capacitors 34, 37: Ground capacitors 35, 38, 39: Filter switch 40: Three-phase inverter 41: Diode rectifier circuit 42: Inverter unit 50: Output cable 60: Three-phase motor C _dc ： Smoothing capacitor

Claims (5)

A first line capacitor consisting of a plurality of capacitors is connected to the input side of the common mode choke coil, and a second line capacitor consisting of a plurality of capacitors is connected to the output side of the common mode choke coil. A first ground capacitor is connected between a neutral point of the first line capacitor and a ground line, and a second ground is connected between the neutral point of the second line capacitor and the ground line. In a π-type noise filter configured by connecting a capacitor,
Providing a first switching connection between the first grounding capacitor and the grounding line, and providing a second switching connection between the second grounding capacitor and the grounding line;
A third switching connection is provided between a connection point between the first grounding capacitor and the first switching connection and a connection point between the second grounding capacitor and the second switching connection. A noise filter characterized by being provided. A first line capacitor consisting of a plurality of capacitors is connected to the input side of the common mode choke coil, and a second line capacitor consisting of a plurality of capacitors is connected to the output side of the common mode choke coil. A first ground capacitor is connected between a neutral point of the first line capacitor and a ground line, and a second ground is connected between the neutral point of the second line capacitor and the ground line. In a π-type noise filter configured by connecting a capacitor,
A first switching connection is provided between a neutral point of the first line capacitor and the first grounding capacitor, and a neutral point of the second line capacitor is connected to the second grounding capacitor. A second switching connection is provided between the capacitor and the capacitor ,
A connection point between the neutral point of the first line capacitor and the first switching connection, and a connection point between the neutral point of the second line capacitor and the second switching connection. A noise filter characterized by providing a third opening / closing connection section between them. A first line capacitor consisting of a plurality of capacitors is connected to the input side of the common mode choke coil, and a second line capacitor consisting of a plurality of capacitors is connected to the output side of the common mode choke coil. A first ground capacitor is connected between a neutral point of the first line capacitor and a ground line, and a second ground is connected between the neutral point of the second line capacitor and the ground line. In a π-type noise filter configured by connecting a capacitor ,
A first switching connection is provided between a neutral point of the first line capacitor and the first grounding capacitor , and a neutral point of the second line capacitor is connected to the second grounding capacitor. A second switching connection is provided between the capacitor and the capacitor ,
A noise filter , comprising: a third switching connection for connecting a connection point between the first switching connection and the first grounding capacitor and a neutral point of the second line capacitor. . A first line capacitor consisting of a plurality of capacitors is connected to the input side of the common mode choke coil, and a second line capacitor consisting of a plurality of capacitors is connected to the output side of the common mode choke coil. A first ground capacitor is connected between a neutral point of the first line capacitor and a ground line, and a second ground is connected between the neutral point of the second line capacitor and the ground line. In a π-type noise filter configured by connecting a capacitor ,
A first switching connection is provided between a neutral point of the first line capacitor and the first grounding capacitor, and a neutral point of the second line capacitor is connected to the second grounding capacitor. A second switching connection is provided between the capacitor and the capacitor,
A noise filter comprising a third switching connection for connecting a connection point between the second switching connection and the second grounding capacitor and a neutral point of the first line capacitor. . A first line capacitor consisting of a plurality of capacitors is connected to the input side of the common mode choke coil, and a second line capacitor consisting of a plurality of capacitors is connected to the output side of the common mode choke coil. A first ground capacitor is connected between a neutral point of the first line capacitor and a ground line, and a second ground is connected between the neutral point of the second line capacitor and the ground line. In a π-type noise filter configured by connecting a capacitor ,
Providing a switching connection between the neutral point of the first line capacitor and the first ground capacitor;
A connection point between said first grounding capacitor before and KiHiraki closed connection portion, between the neutral point of the second line between the capacitor, providing a separate opening and closing the connecting portion and the open-close connecting portions Characteristic noise filter.

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