JPH04331495A - Polyphase inverter - Google Patents

Abstract

PURPOSE:To simplify the constitution by producing AC voltages having different phases from a three winding transformer, subjecting thus produced AC Voltages to twelve phase rectification through interconnected general purpose inverters, and then producing three-phase AC voltages from respective inverters. CONSTITUTION:First and second AC three-phase voltages ac1, ac2, having phase difference of 30 deg., are fed from a three winding transformer to first and second general purpose inverter units 16, 17, respectively. DC terminals thereof are connected in common and fed with DC voltages subjected to twelve phase rectification. An inverter circuit then inverts the twelve phase rectified DC voltages into AC voltages which are fed to respective induction motors 11, 12. Consequently, the circuitry can be simplified by the use of single three winding transformer.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyphase inverter device capable of reducing the generation of harmonics in power equipment such as induction motors.

0002

[Prior Art] Recently, there has been a tendency for semiconductor-applied equipment to be widely used in power conversion equipment such as inverters used to drive power equipment such as induction motors, and this trend will continue to grow. It is predicted that the situation will strengthen. The use of such semiconductor application equipment is often accompanied by the generation of harmonics, and the generation of these harmonics increases voltage distortion, which may cause trouble in incidental equipment. Therefore, it is desirable to generate as few harmonics as possible. As a countermeasure against this problem, it has been pointed out that the generation of harmonics can be suppressed by making the output voltage waveform from the converter section of the power conversion device multi-phase, such as 12 to 24 phases.

An example of this type of power conversion device is an inverter device that converts three-phase AC into a 12-phase rectified waveform and then drives an induction motor with the three-phase AC. This inverter device includes two transformers that convert a three-phase AC voltage into first and second three-phase AC voltages having a phase difference of 30 degrees, rectifies the first and second three-phase AC voltages, and converts the first and second three-phase AC voltages into two transformers. two converters for obtaining first and second DC voltages;
and an inverter that receives the first and second DC voltages and generates a three-phase AC voltage, and the three-phase AC voltage is applied to power equipment such as an induction motor.

0004

[Problems to be Solved by the Invention] However, as the number of phases increases, the circuit configuration of the power conversion device becomes more complicated. The above-described inverter device requires two transformers and two converters, and is inevitably complicated in configuration. In addition, as mentioned above, one power converter usually drives only one power device, so power converters that obtain AC output voltage after multiphase rectification have many disadvantages in terms of economy and reliability. There were also problems in terms of

[0005]

[Means for Solving the Problems] According to the present invention, a three-winding transformer for obtaining first and second three-phase AC voltages having mutually different phases from three-phase AC, a rectifier section, and an inverter section are provided. a first inverter means connected via a connection point, the first inverter means rectifying the first three-phase alternating current voltage by the rectifying section and converting it into the first alternating current voltage in the inverter section; and a second inverter means having the same configuration as the means and for rectifying the second three-phase AC voltage and converting it into a second AC voltage, the rectification in the first and second inverter means A polyphase inverter device is obtained in which the connection points of the inverter section and the inverter section are connected to each other, and the third inverter means is the same as the first and second inverter means.

[0006]

[Operation] As described above, in the present invention, a three-winding transformer is used to generate six-phase AC voltages with different phases, and these six-phase AC voltages are applied to a commercially available general-purpose inverter means connected to each other. In this inverter means, after performing 12-phase rectification, three-phase AC voltage is generated from each inverter means. With this configuration, each three-phase AC voltage can be supplied to different power devices. Furthermore, by connecting induction motors to the first to third inverter means, the regenerated energy of the induction motors can be effectively utilized.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, a polyphase inverter device according to an embodiment of the present invention receives a three-phase input AC voltage ACi and supplies three-phase AC voltages AC1, AC2, and AC3 to three induction motors 11. , 12, and 13. Specifically, the multiphase inverter device includes a three-winding transformer 15 that receives a three-phase input AC voltage ACi and outputs first and second three-phase AC voltages that are 30 degrees out of phase with each other. . As is clear from the figure, the three-winding transformer 15 has a primary winding connected in delta and two secondary windings connected in delta and star. First and second three with different degree phases
Phase alternating current voltages ac1 and ac2 are generated. In the figure, 3
The first and second three as the output voltage of the winding transformer 15
Although the phase alternating current voltages ac1 and ac2 are depicted as appearing on one line, in reality, the first and second three-phase alternating current voltages ac1 and ac2 are output on three lines.

[0008] First and second three-phase AC voltages ac1 and a
c2 is supplied to first and second inverter devices 16 and 17, respectively, which are commercially available. Referring also to FIG. 2, the first and second inverter devices 16 and 17 are each configured by a similar general-purpose inverter device. As shown in Figure 2, the general-purpose inverter device is
A converter section (rectifier section) 20 that performs six-phase rectification and converts alternating current voltage ac into direct current voltage dc, and converts direct current voltage dc into three
The converter section 20 and the inverter section 21 of each general-purpose inverter device are connected to each other via a DC terminal D, as shown in FIG. Specifically, as shown in Figure 2,
They are connected via a pair of DC terminals DC1 and DC2.

As is well known, the converter unit 20 is constructed by combining diodes, and obtains a DC voltage by rectifying a three-phase AC voltage into six phases. On the other hand, the inverter section 21 is composed of three inverter circuits 26, 27, and 28, and each inverter circuit is controlled by a timing control circuit 30. Since each inverter circuit has a similar configuration, only the inverter circuit 26 will be described here. The inverter circuit 26 has a pair of DC terminals DC1 and D.
It includes a pair of transistors 31 and 32 connected in series between C2 and a pair of diodes 33 and 34 connected in parallel to this transistor series circuit. A common connection point between both transistors 31 and 32 and both diodes 3
The common connection point of 3 and 34 is the 3-phase AC voltage AC1, AC2,
It is connected to one of the three power lines for outputting either AC3.

Here, the pair of transistors in the inverter circuit 26 are turned on and off at different timings. In this example, it is assumed that transistors 31 and 32 are turned on at a predetermined timing. Other inverter circuits 27 and 28 are connected to a different power supply line than inverter circuit 26. Among these, inverter circuit 27
The pair of transistors is turned on and off with a phase difference of 120 degrees with respect to the pair of transistors in the inverter circuit 26, and the pair of transistors in the inverter circuit 28 is turned on and off with a phase difference of 240 degrees. In this configuration, three-phase AC voltage is supplied to the induction motor IM.

Returning to FIG. 1, the DC terminals D of the first and second inverter devices 16 and 17 are connected in common, and as mentioned above, the output voltage of the converter section of both inverter devices has a 30 degree angle. There is a phase difference of When connecting the DC terminals D of two such inverter devices, the DC terminal D
is supplied with a 12-phase rectified DC voltage. On the other hand, in an inverter circuit that converts the DC voltage from such a converter section into a three-phase AC voltage, the 12-phase rectified DC voltage is converted into a three-phase AC voltage, and each induction motor 11, 1
Supply to 2.

Furthermore, in the multiphase inverter device shown in FIG. 1, the DC terminal D of the third inverter device 36 is connected to the DC terminals D of the first and second inverter devices 16 and 17. The output of the third inverter device 36 is supplied to the third induction motor 13. Here, the third
The inverter device 36 is not connected to the three-winding transformer 15. According to this configuration, when the direction of the current flowing through the first or second inverter device 16, 17 changes and enters the braking state, the first or second induction motor 11, 12
A regenerative current flows from the regenerative current to drive the third induction motor 13.

[0013]

As described above, in the present invention, the circuit configuration can be simplified by using a single three-winding transformer, and a general-purpose inverter device can be used, so that special equipment design can be avoided. can save the effort of Further, since no dedicated equipment is required, the area occupied by the equipment can be reduced, and since regenerated energy can be used, it is possible to satisfy the demand for energy saving.

[Brief explanation of drawings]

FIG. 1 is a block diagram for explaining the schematic configuration of a polyphase inverter device according to an embodiment of the present invention.

FIG. 2 is a block diagram for explaining a general-purpose inverter device used in the polyphase inverter device shown in FIG. 1;

Claims (1)

[Claims] Claim 1: A three-winding transformer for obtaining first and second three-phase AC voltages having mutually different phases from three-phase AC, and a configuration in which a rectifier section and an inverter section are connected via a connection point. , a first inverter means for rectifying the first three-phase alternating current voltage by the rectifying section and converting it into the first alternating current voltage in the inverter section, and having the same configuration as the first inverter means; a second inverter means for rectifying a second three-phase alternating current voltage and converting it into a second alternating current voltage, the connection points of the rectifier section and the inverter section of the first and second inverter means being connected to each other; A polyphase inverter device, further comprising a third inverter means that is the same as the first and second inverter means.