JP2017118387A - Noise filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a noise filter capable of preventing overhead/burning of a common-mode choke coil and implementing measures to cope with an electromagnetic noise failure in a field.SOLUTION: In a π-type noise filter configured by connecting inter-line capacitors 33 and 36 between an input side and an output side of a choke coil 31, connecting a ground capacitor 34 between a neutral point of the inter-line capacitor 33 and a ground line 32 and connecting a ground capacitor 37 between a neutral point of the inter-line capacitor 36 and the ground line 32, a switching connection part 35 consisting of a switch or the like is provided between the ground capacitor 34 and the ground line 32, a switching connection part 38 consisting of a switch or the like is provided between the ground capacitor 37 and the ground line, and a switching connection part 39 consisting of a switch or the like is provided between a node of the ground capacitor 34 and the switching connection part 35 and a node of the ground capacitor 37 and the switching connection part 38.SELECTED DRAWING: Figure 1

Description

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

Power converters such as inverters and converters that convert power and voltage by switching high-speed switching of several [kHz] to several hundreds [kHz] of power semiconductor elements such as IGBTs and MOSFETs have high efficiency, downsizing, weight reduction, etc. Due to the merits of this, the spread is rapidly expanding.
However, high-speed switching for power conversion causes electromagnetic noise, and electromagnetic noise interference with peripheral devices is a major issue.

  In order to prevent the above-described electromagnetic noise disturbance, the power converter is generally provided with a noise filter, and electromagnetic noise flowing out to the outside is reduced by the action of the noise filter. In addition, the legal regulations for electromagnetic noise that began in Europe are spreading worldwide. 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 clarified.

However, even a power conversion device that satisfies a predetermined standard may cause electromagnetic noise interference in the field. This is because the influence on the peripheral devices of the power conversion device varies greatly depending on the use environment.
If the peripheral device is a device with low noise tolerance (a device that is likely to malfunction, such as a highly sensitive measuring device), or if the measuring device is placed in the immediate vicinity of the power converter, the power converter is the most severe Even if the standard (for example, CISPR22, Class B) is cleared, an electromagnetic noise disturbance may occur.

  In addition, the noise filter of the power converter is generally configured to include a reactor (common mode choke coil), a line-to-line capacitor, and a grounding capacitor, but there are also obstacles caused by the addition of the noise filter. For example, the leakage current that flows through the grounding capacitor increases and the earth leakage circuit breaker responds. The excessive noise current (common mode current) flows through the common mode choke coil, causing overheating and burning of the choke coil. This type of overheating / burnout accident may occur, for example, in the following motor variable speed drive system.

FIG. 7 shows the overall configuration of a variable speed drive system that drives a three-phase AC motor (hereinafter simply referred to as “motor”) by a three-phase inverter.
7, 10 is a three-phase AC power source, 20 is an input cable, 30 is a noise filter shown in FIG. 8 to be described later, 40 is a three-phase inverter comprising a diode rectifier circuit 41, a smoothing capacitor C _dc and an inverter unit 42, 50 is an output cable, and 60 is an electric motor. S _{1 to} S ₆ are semiconductor switching elements such as IGBTs.

Here, the noise filter 30 is configured as shown in FIG. 8, for example. This noise filter 30 is known as a so-called π-type filter.
In FIG. 8, a common mode choke coil 31 including coils 31R, 31S, and 31T is connected between input / output terminals R, R ′, S, S ′, T, and T ′ of each phase of the noise filter 30. .

A first line capacitor 33 and a first ground capacitor are disposed between the input terminals R, S, and T of the common mode choke coil 31 and the ground line 32 (E and E _in indicate ground terminals). 34 and the first filter switch 35 are connected in series, and between the output terminals R ′, S ′, T ′ of the common mode choke coil 31 and the ground line 32, a second line capacitor 36 is connected. A second ground capacitor 37 and a second filter switch 38 are connected in series. Reference numerals 33R, 33S, 33T, 36R, 36S, and 36T are capacitors that constitute the line-to-line capacitors 33 and 36, respectively.

The noise filter 30 mainly flows to the ground line 32 via the stray capacitance formed in the output cable 50 and the electric motor 60 when the three-phase inverter 40 is driven, and flows into the system as a common mode current (high-frequency leakage). Current), and the longer the output cable 50, the larger the stray capacitance formed in the output cable 50 and the larger the common mode current.
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. In this case, the common mode choke coil 31 has a design value or more. Of excessive common mode current may cause overheating and burning.

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

  For example, Patent Document 1 describes a power conversion device including a filter switch having a function equivalent to that of FIG. In this patent document 1, enabling / disabling of the filter function can be selected by turning on / off the filter switch, thereby eliminating the troublesome work associated with the replacement of the noise filter. Excessive leakage current can be obtained by turning off the filter switch. This prevents the occurrence of earth leakage breakers and the like.

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

  However, if the filter function is disabled by turning off the filter switch, the amount of noise that flows out of the power converter increases, resulting in new problems such as malfunction of peripheral devices and overheating / burning of common mode choke coils. There is a concern to cause. Further, since the filter switch has only a function for switching the validity / invalidity of the filter function, when an electromagnetic noise failure occurs when the filter function is valid, a new noise countermeasure component must be added.

  Therefore, the problem to be solved by the present invention is not only to switch the validity / invalidity of the filter function, but also to prevent overheating / burning of the common mode choke coil and to implement an appropriate measure against electromagnetic noise disturbance in the field. Is to provide.

In order to solve the above-mentioned problem, the invention according to claim 1 is configured such that a first line capacitor composed of a plurality of capacitors is connected to the input side of the common mode choke coil, and a plurality of capacitors are connected to the output side of the common mode choke coil. A second line capacitor composed of a capacitor is connected; a first ground capacitor is connected between a neutral point of the first line capacitor and a ground line; and 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 portion is provided between a connection point between the first ground capacitor and the first switching connection portion and a connection point between the second ground capacitor and the second switching connection portion. It is provided.

According to a second aspect of the present invention, a first line capacitor composed of a plurality of capacitors is connected to the input side of the common mode choke coil, and a second line composed of a plurality of capacitors is connected to the output side of the common mode choke coil. An intermediate capacitor is connected, 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 grounded capacitor between
A first switching connection between the neutral point of the first line capacitor and the first ground capacitor; and the neutral point of the second line capacitor and the second ground A second switching connection is provided between the capacitor and the capacitor.

  According to a third aspect of the present invention, in the noise filter according to the second aspect, the connection point between the neutral point of the first line capacitor and the first switching connection part, and the second line capacitor A third open / close connection portion is provided between a neutral point and a connection point between the second open / close connection portion.

  According to a fourth aspect of the present invention, in the noise filter according to the second aspect, a connection point between the first switching connection portion and the first ground capacitor, a neutral point of the second line capacitor, Is provided with a third opening / closing connection part.

  According to a fifth aspect of the present invention, in the noise filter according to the second aspect, a connection point between the second switching connection portion and the second ground capacitor, a neutral point of the first line capacitor, Is provided with a third opening / closing connection part.

In the invention according to claim 6, a first line capacitor comprising a plurality of capacitors is connected to the input side of the common mode choke coil, and a second line comprising a plurality of capacitors is provided to the output side of the common mode choke coil. An intermediate capacitor is connected, 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 grounded capacitor between
Providing an open / close connection between the neutral point of the first line capacitor and the first ground capacitor;
An opening / closing connection portion different from the opening / closing connection portion is provided between a connection point between the first opening / closing connection portion and the first grounding capacitor and a neutral point of the second line capacitor. 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 disconnected, and the neutral points of these line capacitors can be connected to each other. As a result, overheating and burning of the common mode choke coil can be prevented, and appropriate measures can be taken against electromagnetic noise disturbance in the field where the power converter or the like is installed.

It is a circuit diagram which shows the structure of 1st Embodiment of this invention. It is a circuit diagram which shows the structure of 2nd Embodiment of this invention. It is a circuit diagram which shows the use condition of 2nd Embodiment of this invention. It is a circuit diagram which shows the use condition of 2nd Embodiment of this invention. It is a circuit diagram which shows the use condition of 2nd Embodiment of this invention. It is a circuit diagram which shows 3rd Embodiment of this invention. 1 is an overall configuration diagram of an electric 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 30 </ b> A according to the first embodiment of the present invention, and corresponds to the invention according to claim 1. In the following embodiments, components 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 differs from that of FIG. 8 in that the connection point between the first ground capacitor 34 and the first filter switch 35 and the connection between the second ground capacitor 37 and the second filter switch 38. A 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 the first, second, and third open / close connection portions in the claims, respectively. These first, second, and third open / close connection portions may be configured by fixedly arranging switches. As will be described later, a short-circuit piece and a pair of connection points that can be short-circuited by the short-circuit piece. You may comprise by.

  In FIG. 1, when the filter switch 35 is 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, since the common mode current that causes overheating and burning of the common mode choke coil 31 flows to the side of the line capacitors 33 and 36, the common mode choke coil 31 hardly flows. Thereby, it can prevent that an excessive electric current flows into the common mode choke coil 31, and can prevent the overheating and burning.

  Further, the filter switches 35 and 38 are respectively constituted by a short-circuit piece and a pair of connection points that can be short-circuited by the short-circuit piece, and after removing one short-circuit piece, a portion corresponding to the filter switch 39 of FIG. If the pair of connection points provided in the circuit is short-circuited, it is not necessary to provide an independent component as the filter switch 39.

Next, FIG. 2 is a configuration diagram of a noise filter 30B according to the second embodiment of the present invention, and corresponds to the invention according to claim 2.
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, but in the second embodiment, the filter switches 35 and 38 are connected between the line capacitors 33 and 36. Are connected between the neutral points of the capacitor and the grounding capacitors 34 and 37, respectively.

Usually, the components constituting the noise filter are arranged in one place so that a large noise reduction effect can be obtained. Therefore, as shown in FIG. 2, filter switches 35, 38 are provided between the line capacitor and the ground capacitor. It is not common to provide
However, in the first embodiment shown in 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 shown in FIG. By separating the line-to-line capacitors 33 and 36 and the ground capacitors 34 and 37 by the filter switches 35 and 38 and connecting (turning on) the filter switch 39 as shown in FIG. Only the line capacitors 33 and 36 are connected in series via the filter switch 39.
Thereby, compared with 1st Embodiment, the impedance of the bypass path of a common mode electric current becomes small, and the effect which prevents the common mode choke coil 31 from overheating and burning can be improved further.

  More specifically, in the second embodiment, not only the number of capacitors in the common mode current bypass path is reduced, but the electrostatic capacity of the line-to-line capacitors 33 and 36 is more than the ground capacitors 34 and 37 as a design method. The capacity is generally larger. This is because a common mode filter is constituted by the leakage inductance of the common mode choke coil 31 and the grounding capacitors 34 and 37, whereas a normal mode filter is constituted by the leakage inductance of the common mode choke coil 31 and the line-to-line capacitors 33 and 36. The resonance frequency of each filter is set to approximately the same value (near several 10 [kHz]). Here, since the leakage inductance of the common mode filter 31 is very small, by setting the capacitance of the line capacitors 33 and 36 to be larger than the capacitance of the ground capacitors 34 and 37, the resonance frequency of both filters is set to the same level. 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 connection connected in parallel to the common mode choke coil 31 is performed. Since the electric capacity is increased, a larger common mode current can be bypassed to the line capacitors 33 and 36 side. As a result, since the common mode current flowing through the common mode choke coil 31 is reduced, the possibility of overheating and burning of the common mode choke coil 31 is reduced.
Note that the noise filter 30 </ b> C in FIG. 3 corresponds to the invention according to claim 3.

  Also in the second embodiment, the filter switches 35 and 38 are each constituted by a short-circuit piece and a pair of connection points that can be short-circuited by the short-circuit piece, and after both the short-circuit pieces are removed, one of the short-circuit pieces If a pair of connection points provided at a portion corresponding to the filter switch 39 in FIG.

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 is an example in which the noise filter 30D is configured by connecting the filter switch 39 between the connection point of the filter switch 35 and the ground capacitor 34 and the neutral point of the line capacitor 36. These are examples in which the noise filter 30E is configured by connecting the filter switch 39 between the neutral point of the line capacitor 33 and the connection point of the filter switch 38 and the ground capacitor 37.
These noise filters 30D and 30E correspond to the inventions according to claims 4 and 5, respectively.
In either case, the filter switches 35 and 38 are constituted by short-circuit pieces, one of the short-circuit pieces is removed, and then a pair of connection points provided at a portion corresponding to the filter switch 39 of FIG. 4 or FIG. What is necessary is just to short-circuit.

The connection configuration as shown in FIGS. 4 and 5 is possible because a general noise filter is designed to satisfy the standard. This type of standard requires a conduction noise (noise terminal voltage) of 150 [kHz] to 30 [MHz] and a radiation noise (radiation of 30 [MHz] to 1 [GHz] (up to 6 [GHz]). In general, the noise filter is designed so that the noise can be reduced as a whole for 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.

  Specifically, the combination of the common mode choke coil 31 and the second ground capacitor 37 reduces noise of about 1 [MHz] or less, while the first ground capacitor 34 is connected to the AC power supply 10. The 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 generated in the entire wide frequency band of 150 [kHz] to 30 [MHz] is the cause. That is, in most cases, electromagnetic interference in a narrow frequency band usually occurs in combination with a peripheral device causing the failure.
For example, in the case of noise mixing into AM radio, electromagnetic noise in the frequency band of 531 [kHz] to 1602 [kHz] becomes a problem. Alternatively, the peripheral device may malfunction due to electromagnetic noise occurring at 150 [kHz] or less which is not regulated. That is, the electromagnetic noise disturbance occurs due to a combination of a power conversion device such as an inverter and an affected peripheral device.

  Therefore, if 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 greatly reduced as compared with the case of FIG.

  Further, when the installation location of the third filter switch 39 is selected so that the circuit shown in FIG. 5 is configured, the amount of reduction of the electromagnetic noise of about 1 [MHz] or less is reduced, whereas 1 [MHz] ] Electromagnetic noise in the above frequency band is reduced. In general, noise countermeasures in a frequency band of 5 [MHz] or more largely depend on component arrangement and are difficult to obtain by theoretical calculation. However, in the configuration of FIG. 5, it is expected that the electromagnetic noise can be reduced by focusing on the high frequency by turning on the filter switches 35 and 39 and collecting the ground capacitors 34 and 37 on the power source side.

In the second embodiment shown in FIGS. 2 to 5, the first and second line capacitors 33 and 36, the first line capacitor 33, the first line capacitor 33, and the first line capacitor 33, except for the installation location of the third filter switch 39 and its on / off state. , 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-circuit pieces constituting the first and second filter switches 35 and 38, all of the parts shown in FIGS. A circuit is constructed.
Accordingly, the noise filters 30B, 30C, 30D, and 30E in FIGS. 2 to 5 can be configured by using common components, and the problem that should be most countered (approximately 1 [MHz] when protecting the common mode choke coil) In the case of reducing the following electromagnetic noise, the configuration may be selected according to the case of reducing the electromagnetic noise of 1 [MHz] or more, and the configuration of the noise filter when the filter switch which is the basic configuration is not provided (filter The noise reduction effect is not impaired by the configuration in which the switches 35 and 38 are turned on and the switch 39 is turned off. Therefore, the conventional filter design (determination of circuit constants) is not adversely affected.

  Next, FIG. 6 is a block diagram showing a third embodiment of the present invention, and corresponds to the invention according to claim 6. 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 of FIG.

That is, in the third embodiment shown in FIG. 6, the basic configuration of the π-type filter and the ground capacitors 34 and 37 are integrated on the inverter 40 side by the operations of the first and third filter switches 35 and 39. And a configuration that can significantly reduce electromagnetic noise in a frequency band of 1 [MHz] or less (a filter switch 35 is turned off and a filter switch 39 is turned on), and a configuration that prevents overheating and burning of the common mode choke coil 31 (Filter switches 35 and 39 are turned on) can be realized. Further, if both the filter switches 35 and 39 are turned off, the grounding capacitor 34 can be disconnected from the grounding line 32, so that the leakage current can be reduced.
However, as shown in FIGS. 2 to 5, since all the ground capacitors cannot be disconnected from the ground line, the effect of reducing the leakage current can be said to be limited, but there is an advantage that the number of filter switches can be configured with two. is there.

In addition, although each embodiment mentioned above is related with the noise filter connected to a three-phase alternating current circuit, this invention is applicable also when connected to a single phase alternating current circuit.
Furthermore, the same effect can be obtained also when part or all of the noise filter according to the present invention is connected to the DC intermediate circuit of the power conversion device (for example, the connection location of the smoothing capacitor C _dc in FIG. 7). .
In addition, although each embodiment assumes a noise filter built in the variable speed drive system, 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 a load such as an electric motor using an inverter, a converter, or the like.

10: Three-phase AC power supply 20: Input cables 30A, 30B, 30C, 30D, 30E, 30F: Noise filter 31: Common mode choke coils 31R, 31S, 31T: Coil 32: Ground wire 33, 36: Line capacitor 33R, 33S, 33T, 36R, 36S, 36T: Capacitors 34, 37: Grounding 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 (6)

A first line capacitor composed of a plurality of capacitors is connected to the input side of the common mode choke coil, and a second line capacitor composed of a plurality of capacitors is connected to the output side of the common mode choke coil. A first grounding capacitor is connected between the neutral point of the first line capacitor and the ground line, and a second grounding is performed 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 portion is provided between a connection point between the first ground capacitor and the first switching connection portion and a connection point between the second ground capacitor and the second switching connection portion. A noise filter characterized by being provided. A first line capacitor composed of a plurality of capacitors is connected to the input side of the common mode choke coil, and a second line capacitor composed of a plurality of capacitors is connected to the output side of the common mode choke coil. A first grounding capacitor is connected between the neutral point of the first line capacitor and the ground line, and a second grounding is performed 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 between the neutral point of the first line capacitor and the first ground capacitor; and the neutral point of the second line capacitor and the second ground A noise filter, characterized in that a second open / close connection is provided between the capacitor and the capacitor. The noise filter according to claim 2,
A connection point between the neutral point of the first line capacitor and the first switching connection part, and a connection point between the neutral point of the second line capacitor and the second switching connection part A noise filter characterized in that a third switching connection portion is provided between them. The noise filter according to claim 2,
A noise filter comprising: a third switching connection for connecting a connection point between the first switching connection and the first grounded capacitor and a neutral point of the second line capacitor. . The noise filter according to claim 2,
A noise filter comprising: a third switching connection portion for connecting a connection point between the second switching connection portion and the second ground capacitor and a neutral point of the first line capacitor. . A first line capacitor composed of a plurality of capacitors is connected to the input side of the common mode choke coil, and a second line capacitor composed of a plurality of capacitors is connected to the output side of the common mode choke coil. A first grounding capacitor is connected between the neutral point of the first line capacitor and the ground line, and a second grounding is performed 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 an open / close connection between the neutral point of the first line capacitor and the first ground capacitor;
An open / close connection portion different from the open / close connection portion is provided between a connection point between the first open / close connection portion and the first ground capacitor and a neutral point of the second line capacitor. Feature noise filter.

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