JP2011155727A - Power converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce earth current flowing out of a power converter. <P>SOLUTION: The power converter accommodates a multiplex winding transformer, an inverter constituted of a plurality of cell inverters which receive power from the multiplex winding transformer while being insulated from one another, by means of the multiplex winding transformer and a filter circuit provided on the inverter output side, wherein the inverter output is supplied to an external motor through the filter circuit in a housing. A low impedance common earth bus line is insulated and arranged in the housing, and the neutral point of the inverter, a fault contact prevention plate of the multiplex winding transformer, and the neutral point of the filter circuit, are connected to the common earth bus line to cause the common earth bus line to be connected to the housing and grounded outside the housing. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a power conversion device having a ground circuit configuration for reducing an outflow current to a ground system.

  In a power converter provided with an inverter generally used for variable speed drive of an induction motor, an AC voltage having a specific frequency is once converted into a DC voltage by a rectifier circuit, and then an inverter using a semiconductor element (IGBT or the like). An output voltage of an arbitrary frequency is obtained by switching in the circuit. At that time, a switching surge voltage is generated and the neutral point of the alternating voltage is changed, which is the main cause of the current flowing out to the grounding system.

  In the conventional power supply device, the ground wire of the high-voltage circuit is connected to the ground electrode of the facility through a single wiring after being gathered to the type A ground electrode having the same potential as the device housing. In addition, when multiple transformers exist in the same row, the grounding of the anti-contact plate was separately wired as Class B installation separately from the device housing grounding.

  There exists a thing described in patent document 1 as a power converter device with which the earthing | grounding countermeasure was given.

JP 2006-304492 A

  FIG. 2 shows an example of a power conversion device with a grounding countermeasure described in Patent Document 1. However, Patent Document 1 does not describe the output filter circuit 20 for suppressing harmonics on the output side and the control circuit, but when these are provided, they are often configured as shown.

  In FIG. 2, the power conversion device 1 stores the following various devices in the same casing as one package and supplies power to the three-phase induction motor 3. The main devices housed here are the multiple transformer 2 from the power input side, the inverter 5 composed of a plurality of cell inverters 10 of the main circuit, the output filter circuit 20, and the like, and may include a control circuit 40. . Among these, the multiple transformer 2 and the inverter 5 are indispensable devices housed in the same housing, and the output filter circuit 20 and the control circuit 40 may be deleted from the housing or installed separately. The output filter circuit 20 includes a filter reactor 21, a filter resistor 22, and a filter capacitor 23.

  In the electric power converter 1 which concerns, the earth | ground of the form suitable for each electric power equipment apparatus is performed. First, since the multiple transformer 2 on the power input side is provided with the anti-incompatibility plate 8 for preventing incompatibility between the primary and secondary windings, this is connected to the transformer anti-intrusion plate via the anti-intrusion plate ground 31. Connect to the grounding electrode (Class B grounding) 35. In the inverter 5, it is connected to the inverter device grounding electrode 34 (class A grounding) via the cell inverter neutral point installation 32. When the output filter circuit 20 is provided, there are many cases where no special grounding is applied. When the control circuit 40 is provided, control circuit grounding (C-type grounding) is performed.

  In the illustration of FIG. 2, there are white circles and black circles as intersections of dotted lines representing the chassis of the power conversion device 1 and each ground, but the former means no connection, and the latter means a connection relationship. That is, as the grounding of the casing of the power conversion device 1, A-type grounding is performed at the inverter 5 which is a main device of the power conversion device 1. In other words, the cell inverter neutral point ground 32 and the casing are connected (black circles in the figure) to the same potential, and then the high-voltage multiple inverter device grounding (class A grounding) is performed. Similarly, in the respective grounding in the transformer 2 and the control circuit 40 indicated by white circles, grounding of a type suitable for each is performed after disconnecting from the casing and thus insulation.

  In the power converter 1, harmonics are generated for various reasons. For example, the voltage output from the output filter circuit 20 is applied to the three-phase induction motor 3, but the ground-to-ground stray capacitance is caused by the change in the voltage between the ground due to the change in the neutral point of the output filter circuit 20 that is not grounded. Harmonic current flows to ground via 42. This eventually becomes a loop current returning from the inverter device ground 34 to the cell inverter neutral point ground 32, which causes the ground current to increase.

  As for the multiple transformer 2 provided on the input side, the harmonic current flows out from the anti-contact plate ground 31 by the switching operation of the cell inverter 10 of the main circuit. The ground current flows from the class B installation electrode 35 to the facility ground electrode, and finally becomes a loop current returning from the inverter device ground electrode 34 to the cell inverter neutral point installation 32, which also causes the ground current to increase. .

  Since each of the above ground currents independently flows outside the housing of the power converter 1, not only the sum of the current values is large, but if the ground cables are not properly separated, the peripheral devices are adversely affected. The potential for effects remains.

  As an example in which the influence of the ground current is remarkable, the installation pole 50 on the equipment side as shown in FIG. 3 is a common bus, and not only the A type high voltage ground 34 but also the B type anti-contact plate ground 35, When the C type installation 41 of the low-voltage control circuit is grounded in the same system (when the external ground bus system is adopted), the influence of the harmonic current flowing out from the power converter 1 having a large capacity is generally ignored. If the installation cable is not properly separated, the control by the peripheral device 43 and its own control circuit 40 may be adversely affected. Further, other instrumentation wiring may exist near the power line between the power converter 1 and the three-phase induction motor 3, and in this case, noise may be generated in the instrumentation wiring.

  In the present invention, a multi-winding transformer and an inverter made up of a plurality of cell inverters that are insulated from each other and fed by the multi-winding transformer are housed in a housing, and the inverter output is supplied to an external motor. In the converter, the common ground bus is insulated in the housing, the neutral point of the inverter is connected to the common ground bus, and the multi-winding transformer incompatibility prevention plate is connected to the common ground bus. By grounding at, the outflow of harmonic current generated by the switching operation of the inverter is reduced.

In the present invention, in a power converter that houses an inverter that is a plurality of cell inverters and a filter circuit provided on the inverter output side, and supplies the inverter output to an external electric motor via the filter circuit.
By insulating the common ground bus in the housing, connecting the neutral point of the inverter to the common ground bus and the neutral point of the filter circuit, connecting the common ground bus to the housing and grounding it outside the housing, Reduces the outflow of harmonic currents due to fluctuations in the neutral point of the filter circuit.

  In the present invention, a multi-winding transformer, an inverter composed of a plurality of cell inverters that are mutually insulated and fed by the multi-winding transformer, and a filter circuit provided on the inverter output side are housed in a housing. In a power converter that supplies inverter output to an external motor via a filter circuit, a common ground bus is insulated in the housing, and the neutral point of the inverter is connected to the common ground bus to prevent intermingling of multiple winding transformers. By connecting the plate and the neutral point of the filter circuit, connecting the common ground bus to the chassis and grounding it outside the chassis, the switching current of the inverter and the harmonic current fluctuations due to the neutral point fluctuation of the filter circuit Reduce spillage.

  Further, the control circuit may be insulated from the housing and grounded outside the housing.

  According to the present invention, the ground current flowing out from the power converter can be greatly reduced.

It is a basic lineblock diagram of a power converter to which the present invention is applied. It is a general grounding block diagram in the prior art. It is the earthing | grounding block diagram in a board | substrate outside bus-bar system. It is a block diagram of the common ground bus in the panel.

  Examples of the present invention will be described below.

  FIG. 1 shows the overall configuration of the device of the present invention.

  The power conversion device 1 is a power supply device that directly drives the high-voltage motor 3 without boosting the voltage by an output transformer by connecting the single-phase cell inverters 10 in series corresponding to N stages.

  The plurality of cell inverters 10 of the inverter 5 have a single-phase voltage type inverter configuration, convert the input three-phase voltage to DC by the rectifier circuit 11, smooth the DC voltage by the smoothing capacitor 12, and then by the inverter circuit 13 Perform switching and obtain an output of any voltage / frequency.

  In order to obtain the output voltage by the series connection of the cell inverters 10, each cell inverter 10 needs to be electrically insulated and includes a multiple transformer 2 having a plurality of insulated secondary windings. In addition, an anti-intrusion plate 8 is provided between the transformer primary winding and the secondary winding, and an exclusive anti-intrusion plate ground electrode 31 is provided. Each cell inverter 10 is connected in a star shape, and the cell inverter neutral point 32 on the opposite side to the output side is installed through a resistor. That is, single-phase cell inverters connected in series form a plurality of phase unit inverters, and the neutral point 32 on the opposite side of the plurality of phase unit inverters is defined as a cell inverter neutral point 32.

  The output side of the inverter 5 has an output filter circuit 20 for suppressing harmonics and voltage surges. The circuit includes a filter reactor 21, a filter resistor 22, and a filter capacitor 23. In addition, an output filter circuit neutral point 33 is installed to suppress harmonic voltage components between the ground.

  In the present invention, for the purpose of reducing harmonics flowing in the power line between the three-phase induction motor 3 or the ground, the harmonics are enclosed in the housing (dotted line in the figure) of the power converter 1. Specifically, we decided to form a harmonic circulation route inside the enclosure and prevent it from flowing out as much as possible.

  In order to realize the present invention, the common ground bus 24 is provided in a state of being electrically floated from the housing by the insulating support 25. The common ground bus 24 is connected to a ground contact electrode 31 for preventing contact, a neutral point 32 for a cell inverter, and a neutral point 33 for an output filter circuit. The impedance (Zcom) of the common ground bus 24 is set to a value sufficiently smaller than the impedance of the equipment grounding electrode 50 (Zg, 10Ω or less in the case of class A grounding). The common ground bus 24 may be a so-called ground bar having a metal bar shape because a large current may flow.

  As described above, in the present invention, the common ground bus 24 is provided in the casing, and the anti-contact plate ground electrode 31, the cell inverter neutral point 32, and the output filter circuit neutral point 33 are connected. This idea of common connection within the chassis is different from the conventional individual device grounding concept (each power device is grounded according to the voltage class used there). In the present invention, the multiple transformer is positioned as a main component in the power conversion device 1, and the B type grounding for personal protection, which is the original purpose of grounding, is independent (even if shared with the A type grounding). As a result of determining that no problem occurs, this configuration is adopted.

  As a result, the surge voltage generated by the switching operation in the inverter 5 and the harmonics generated by the fluctuation of the neutral point voltage are output from the grounding pole 31 of the contact prevention plate of the multiple transformer 2 on the input side and output on the output side. By returning from the filter circuit neutral point ground 33 to the cell inverter neutral point 32, it is possible to reduce the current finally flowing from the high-voltage multiple inverter device ground 34 to the equipment ground electrode. According to the actual measurement results, the outflow current after the implementation of the present invention could be reduced to 1/3 to 1/4.

  In the best mode of the present invention, the leakage currents from the three grounding poles of the main circuit, the anti-contact plate 31, the unit neutral point 32, and the filter circuit neutral point 33 are not individually supplied to the installation pole. It becomes possible to cancel the electromagnetically closed inside of the casing 1 of the inverter panel, and to reduce the ground current finally flowing out from the casing.

  In addition, as the power converter 1, the filter circuit 20 may not be provided in the housing or may be ungrounded even if it is provided. In this case, the contact prevention plate 31 and the unit neutral point 32 are connected to the common ground bus 24, but it is possible to reduce harmonics caused by the surge voltage generated by the switching operation in the inverter 5. Needless to say, the effects of the present invention can be achieved.

  FIG. 4 shows a grounding configuration example to which the present invention is applied. In this example, a high-voltage multiple inverter apparatus is configured to cause the outflow current from three grounding poles of the main circuit, the anti-contact plate 31, the unit neutral point 32, and the filter circuit neutral point 33 to pass through the common ground bus 24 in the housing. The control circuit 40 is installed with control circuit grounding (C type grounding). At this time, the common ground bus 24 is connected to the equipment installation pole 50 after being connected to the chassis of the power converter 1, and the control circuit 40 is not connected to the chassis and is connected to the equipment installation pole 50. The

  According to the present invention, the ground current flowing out from the power converter can be greatly reduced. For this reason, since it can apply also when there exists an installation which is easy to receive the influence of a harmonic in the apparatus vicinity, an application range can be expanded more than before.

DESCRIPTION OF SYMBOLS 1 Power converter 2 Multiplexing transformer 3 Three-phase induction motor 5 Inverter 10 Cell inverter 11 Rectifier circuit 12 Smoothing capacitor 13 Inverter circuit 20 Output filter circuit 21 Filter reactor 22 Filter resistor 23 Filter capacitor 24 Common ground bus (Zcom)
25 Insulation support 31 Transformer contact prevention grounding 32 Cell inverter neutral point grounding 33 Output filter circuit neutral point grounding 34 High voltage multiple inverter device grounding (Class A grounding)
35 Transformer incompatible plate grounding (Class B grounding)
40 Control circuit 41 Control circuit grounding (Class C grounding)
42 Electric motor-to-ground floating capacity 43 Peripheral equipment 50 Equipment ground electrode (Zg)

Claims (4)

In a power converter that houses a multiple winding transformer and an inverter composed of a plurality of cell inverters that are insulated and fed from each other by the multiple winding transformer, and supplies the inverter output to an external motor.
A common ground bus is insulated in the housing, the neutral point of the inverter is connected to the common ground bus, and an incompatibility prevention plate of a multi-winding transformer, and the common ground bus is connected to the housing and the housing. A power converter characterized by being grounded outside. In a power conversion device that houses an inverter consisting of a plurality of cell inverters and a filter circuit provided on the inverter output side, and supplies the inverter output to an external electric motor via the filter circuit.
A common ground bus is insulated in the housing, the neutral point of the inverter and the neutral point of the filter circuit are connected to the common ground bus, and the common ground bus is connected to the housing and external to the housing. A power converter characterized in that it is grounded. A multi-winding transformer, an inverter composed of a plurality of cell inverters that are insulated and fed from each other by the multi-winding transformer, and a filter circuit provided on the inverter output side are housed in a housing, and the inverter output In a power converter that supplies an external electric motor via a filter circuit,
A common ground bus bar is insulated and disposed in the housing, and the neutral point of the inverter, an incompatibility preventing plate of a multi-winding transformer, and a neutral point of the filter circuit are connected to the common ground bus bar. A power conversion device characterized in that a ground bus is connected to the housing and grounded outside the housing. In the power converter device in any one of Claims 1 thru | or 3,
A power conversion device characterized in that a control circuit is insulated and disposed inside the housing, and the control circuit is grounded outside the housing.

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