JP2017041920A - Inverter device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inverter device which can appropriately suppress both a high frequency leakage current and a leakage current of an AC power frequency component.SOLUTION: The inverter device includes: an inverter circuit; a housing side ground terminal to ground a device housing; a motor side ground terminal to connect a shield coating which covers the outer periphery of a cable connected to a motor and/or the ground line of the motor; and a noise filter circuit connected to a power supply line which supplies power to the inverter circuit. The noise filter circuit includes: a first grounding capacitor part which is connected between the power supply line and the motor side ground terminal; and a second grounding capacitor part which is connected between the motor side ground terminal and the housing side ground terminal.SELECTED DRAWING: Figure 1

Description

  Embodiments described herein relate generally to an inverter device.

  The inverter device supplies AC power of a desired frequency to a load such as a motor by switching a switching element such as an IGBT at high speed and performing PWM control. In this case, if a high-frequency leakage current flows to the ground via the motor cable connecting the motor and the inverter device or the stray capacitance of the motor due to the sudden change in voltage due to the switching operation described above, the commercial AC power supply is turned off. May affect the operation of other devices.

  On the other hand, it is common practice to insert an EMC (Electromagnetic compatibility) filter in the inverter device to suppress the leakage current from flowing into the commercial AC power supply. The EMC filter is often composed of a capacitor including a ground capacitor, a common mode choke, or the like. However, the grounding capacitor is effective for high-frequency leakage current that is a target of EMC countermeasures, but generates leakage current of AC power frequency components. Between the increase / decrease in the high-frequency leakage current corresponding to the switching frequency and the increase / decrease in the leakage current of the AC power supply frequency component according to the capacitance of the grounding capacitor, there is a conflict as shown in FIG. There is a relationship.

JP-A-1-2433843

For this reason, if emphasis is placed on EMC countermeasures and the capacitance of the grounding capacitor is increased too much, the leakage current of the AC power supply frequency component increases, causing problems such as unnecessary operation of the leakage breaker.
Therefore, an inverter device that can appropriately suppress both high-frequency leakage current and leakage current of AC power supply frequency component is provided.

The inverter device of the embodiment is
An inverter circuit;
A housing-side ground terminal for grounding the device housing;
A shield coating covering the outer periphery of the cable connected to the motor and / or a motor-side ground terminal for connecting the ground wire of the motor;
A noise filter circuit connected to a power line for supplying power to the inverter circuit,
The noise filter circuit includes a first grounding capacitor connected between the power line and the motor-side ground terminal, and a second ground connected between the motor-side ground terminal and the housing-side ground terminal. And a capacity portion.

The figure which is 1st Embodiment and shows the structure of an inverter apparatus The figure which shows the modification of a noise filter circuit The figure which shows the result of having simulated the generation | occurrence | production state of the high frequency area noise about the case where the noise filter circuit without the capacitor | condenser C3 is applied to an inverter apparatus, and the case where the noise filter circuit of this embodiment is applied. The figure which shows the result of FIG. 3 separately by (a) and (b) The figure which is 2nd Embodiment and shows the structure of an inverter apparatus

(First embodiment)
Hereinafter, a first embodiment will be described with reference to FIGS. 1 to 4. As shown in FIG. 1, an inverter device 1 includes a rectifier circuit 3 that rectifies a voltage input from a three-phase commercial AC power supply 2 and outputs a DC voltage 3. A smoothing capacitor 4 that smoothes the DC voltage. And an inverter circuit 5 that reversely converts the signal to the motor M and supplies it to the motor M. The inverter circuit 5 is configured by connecting switching elements such as IGBTs in a three-phase bridge. Each phase output terminal of the inverter circuit 5 is connected to one end of each phase stator winding (not shown) of the motor M via the cable 6.

  Further, the inverter device 1 includes a housing-side ground terminal G1 for grounding the casing of the device 1 and a motor-side ground terminal for connecting a shield coating covering the outer periphery of the cable 6 and / or a ground wire of the motor M. At least two ground terminals with G2 are provided. Further, the inverter device 1 includes a noise filter circuit 7.

The noise filter circuit 7 has three capacitors C1a connected to AC power supply lines 8a, 8b, and 8c, each connecting one end of the star connection between the commercial AC power supply 2 and each phase AC input terminal of the rectifier circuit 3. , C1b and C1c, a capacitor C2 connected between the common connection point of the star connection and the motor side ground terminal G2, and a capacitor C3 connected between the motor side ground terminal G2 and the housing side ground terminal G1. And. Also,
C1 = C1a = C1b = C1c
And Here, the capacitors C1 and C2 correspond to a first grounded capacity part (capacitor circuit), and the capacitor C3 corresponds to a second grounded capacity part. The DC output terminal of the rectifier circuit 3 and the inverter circuit 3 are connected by DC power supply lines 9a and 9b.

  In the noise filter circuit, for example, the capacitor C2 may be omitted as shown in FIG. Further, each capacitor element in the figure may be composed of a plurality of parallel or series capacitors. Further, the noise filter circuit 7 may include a common mode choke.

Here, the equivalent capacitor capacity of the first grounded capacity section (the combined capacity between each phase of the first grounded capacity section and the common connection point) is C1 × C2 / (C1 + C2)
It is represented by Then, the capacitor capacity C3 of the second grounded capacity part is set smaller than the capacitor capacity of the first grounded capacity part.

As a result, as shown in FIG. 1, the leakage current from the motor M and the cable 6 is recovered through the first grounded capacitor section having a relatively large capacity in the noise filter circuit 7, and is circulated to the commercial AC power supply 2 side. It is suppressed. Furthermore, the leakage current of the AC power supply frequency component passes through the series circuit of the first and second grounded capacitance units. The equivalent capacitor capacity of this series circuit is C1 × C2 × C3 / (C1 × C2 + C2 × C3 + C3 × C1)
Thus, since the capacitance C3 is dominant and has a value smaller than the capacitance C3, the leakage current of the AC power frequency component can be suppressed low.

Here, as an example, the value of each capacitance is C1: 1 μF.
C2: 0.47 μF
C3: 0.047 μF
Then, the equivalent capacitor capacity of the first ground capacitance part is C1 × C2 / (C1 + C2) ≈0.32 μF
On the other hand, the equivalent capacitance of the series circuit of the first and second grounded capacitance units is C1 × C2 × C3 / (C1 × C2 + C2 × C3 + C3 × C1) ≈0.041 μF
It becomes.

  FIG. 3 shows the case where a noise filter circuit in which the motor side ground terminal G2 and the housing side ground terminal G1 are directly connected without the capacitor C3 is applied to the inverter device (shown by a solid line in the figure). This is a result of simulating the generation state of high-frequency region noise when the above noise filter circuit 7 is applied (indicated by a broken line in the figure). 4 (a) and 4 (b) individually show the same results. The noise level of the noise filter circuit 7 of this embodiment is generally lower.

  Further, the simulation result of the leakage current at the power supply frequency of 50 Hz is 2.4 mA in the noise filter circuit without the capacitor C3, whereas the noise filter circuit 7 of the present embodiment has an extremely small value of 0.2 mA. became.

As described above, according to the present embodiment, the noise filter circuit 7 has an independent first grounded capacitor part that is dominant in measures against high-frequency leakage current and a second grounded capacitor part that is dominant in AC power supply frequency leakage current. Therefore, it is possible to enhance the effect of preventing the high frequency leakage current from flowing to the commercial AC power supply 2 side and to prevent the leakage current of the power frequency component from increasing.
In addition, since the capacitance of the second grounded capacitance unit is set smaller than that of the first grounded capacitance unit, the combined capacitance value when these are connected in series is made smaller, and the leakage current of the power supply frequency component is increased. It can be further suppressed.

(Second Embodiment)
Hereinafter, the same parts as those in the first embodiment are denoted by the same reference numerals, description thereof will be omitted, and different parts will be described. As shown in FIG. 5, the inverter device 11 of the second embodiment has a configuration in which a switch circuit 12 (short circuit) is connected in parallel to the capacitor C3. The installation conditions for each user of the inverter device are individually different. For this reason, when the stray capacitance from the motor M or the cable 6 to the ground (shown by a broken line in the figure) is relatively large, a high-frequency leakage current via the stray capacitance may be a problem.

  In such a case, the switch circuit 12 is closed and the capacitor C3 is short-circuited. As a result, the leakage current of the power supply frequency component increases, but the effect of collecting the high-frequency leakage current in the path indicated by the broken line in the figure can be improved. As a result, the leakage current of the power supply frequency component increases, but the standard inverter device 11 can answer a wide range of user requests, and the situation of providing a plurality of types of inverter devices can be avoided in order to deal with individual users.

(Other embodiments)
The capacitance value of the second grounded capacitance portion does not necessarily need to be set smaller than the capacitance value of the first grounded capacitance portion.
You may apply about the case where an inverter apparatus receives power supply from a single phase commercial alternating current power supply.
The first grounded capacitance unit may be connected to the DC power supply lines 9a and 9b.

  Although some embodiments of the present invention have been described, the present invention is not limited to the configurations shown in each embodiment, and these embodiments are presented as examples and are not intended to limit the scope of the invention. Not intended. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  In the drawings, 1 is an inverter device, 2 is a commercial AC power supply, 3 is a rectifier circuit, 5 is an inverter circuit, 6 is a cable, 7 is a noise filter circuit, 8 is an AC power supply line, 9 is a DC power supply line, and C1 and C2 are Capacitor (first grounded capacity part), C3 is a capacitor (second grounded capacity part), 11 is an inverter device, 12 is a switch circuit (short circuit), G1 is a housing side ground terminal, G2 is a motor side ground terminal, and M is Indicates a motor.

Claims (3)

An inverter circuit;
A housing-side ground terminal for grounding the device housing;
A shield coating covering the outer periphery of the cable connected to the motor and / or a motor-side ground terminal for connecting the ground wire of the motor;
A noise filter circuit connected to a power line for supplying power to the inverter circuit,
The noise filter circuit includes a first grounding capacitor connected between the power line and the motor-side ground terminal, and a second ground connected between the motor-side ground terminal and the housing-side ground terminal. An inverter device having a capacity unit.   2. The inverter device according to claim 1, wherein a capacity of the second grounded capacity portion is set smaller than that of the first grounded capacity portion.   The inverter device according to claim 1, further comprising a short circuit for short-circuiting the second grounded capacitance unit.

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