JP2510116B2 - 3-phase rectifier circuit - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a three-phase rectifier circuit.

[0002]

2. Description of the Related Art FIG. 4 shows a conventional three-phase full-wave diode rectifier circuit. As shown in the figure, diodes 5a-5
The three-phase full-wave diode rectifier circuit 5 having rectifiers 5c ', 5a'-5c' is connected to each phase of the three-phase AC power supply 1 and the connection point A,
They are connected at B and C. A capacitor 22 is connected to the DC side of the three-phase full-wave diode rectifier circuit 5 to reduce the pulsation of the DC output voltage. Capacitor 22
A load 21 is connected in parallel with.

[0003]

In the three-phase full-wave diode rectifier circuit of FIG. 4, the ripple current flowing through the capacitor 22 is large and the input current waveform flowing from the three-phase AC power supply 1 becomes a pulse shape, and the three-phase AC power supply 1 There was a defect that the voltage waveform of was distorted and the power factor of the input decreased. As a countermeasure against this drawback, various countermeasures such as multi-phase and multi-pulse rectifiers represented by a dual 3-phase 12-pulse rectifier circuit consisting of a combination of a star connection and a triangle connection equipped with a transformer on the input side are available. Although it is currently being implemented, it is inevitable that the equipment will become larger and the cost will increase. Therefore, the present invention, in the three-phase full-wave diode rectifier circuit, without using a transformer on the input side,
The input current waveform is approximated to a sine wave so that the voltage waveform of the three-phase AC power source connected to the three-phase full-wave diode rectifier circuit is prevented from being distorted and the input power factor is improved.

[0004]

According to the present invention, an AC reactor is connected in series between an input terminal of each phase of a main conversion circuit composed of a three-phase full-wave diode rectifier circuit and a three-phase AC power source. The input terminal of each phase of the conversion circuit is connected to one end of the three switches of the first group, the other ends of the three switches are commonly connected, and the single-phase self-excited conversion circuit is connected to the connection point. In this single-phase self-excited conversion circuit, a second group of switches each consisting of four sets of two switches connected in series are connected in parallel to the DC side of the main conversion circuit. Two capacitors connected in series with each other are connected in parallel to the DC side of the main conversion circuit, and one end of the primary winding of the first single-phase transformer is connected to the middle point of the two switches of the first set. , The other end is connected to the middle point of the two switches of the second set, and the primary winding of the second single-phase transformer One end of each of the three switches is connected to the middle point of the two switches, and the other end is connected to the middle point of the two switches of the fourth set to connect the first single-phase transformer and the second single-phase transformer. The secondary windings of the reactor are connected in series and one end of the
The switches are connected to the commonly connected terminals and the other end is connected to the middle point of the two capacitors, and the three switches of the first group are synchronized with the three-phase AC power supply, respectively. The switches are sequentially turned on every 1/3 cycle, and the four sets of switches of the second group are synchronized with the three-phase AC power supply and are alternately turned on at a frequency three times that of the three-phase AC power supply.

[0005]

By using the above means, the three-phase full-wave diode rectifier circuit is connected in series between the input terminal of each phase of the three-phase full-wave diode rectifier circuit and the three-phase AC power source. The generated voltage waveform between the terminals is in the same phase as the AC voltage applied to the AC power source side terminal of the AC reactor and has a stepwise waveform of 24 steps in one cycle. The input current waveform of the rectifier circuit according to the present invention has a stepwise waveform of 24 steps.

[0006]

FIG. 1 shows an example of a three-phase rectifier circuit according to the present invention, which is an input terminal A, B for each phase of a three-phase full-wave diode rectifier circuit 5 composed of diodes 5a-5c, 5a'-5c '. , C and a three-phase AC power supply 1 including AC power supplies 1a, 1b, and 1c, AC reactors 2, 3, and 4 are connected in series, and an input terminal A of each phase of the three-phase full-wave diode rectifier circuit 5 is provided. B and C are respectively connected to one ends of switches SA, SB, and SC made of, for example, bidirectional self-arc-extinguishing semiconductor elements, and the other ends of the switches SA, SB, and SC are commonly connected at a terminal n. Connect a single-phase self-excited conversion circuit to the connection point. This single-phase self-excited conversion circuit has a set of four switches S each composed of two switches, which are, for example, self-turn-off type semiconductor elements connected in series.
1 and S2, S3 and S4, S5 and S6, S7 and S8 are respectively connected in parallel to the DC side of the three-phase full-wave diode rectifier circuit 5, and two capacitors 19 are connected in series with each other.
20 is connected in parallel to the DC side of the three-phase full-wave diode rectifier circuit 5, one end of the primary winding 17a of the single-phase transformer 17 is connected to the midpoint of the switches S1 and S2, and the other end is connected to the switches S3 and S2.
4, the one end of the primary winding 18a of the single-phase transformer 18 is connected to the middle point of the switches S5 and S6, and the other end is connected to the middle point of the switches S7 and S8. The secondary winding 17b of 17 and the secondary winding 18b of the single-phase transformer 18 are connected in series, one end thereof is connected to the terminal n, and the other end is connected to the midpoint N of the two capacitors. And configure. The control circuit 22 detects the phase of the voltage of the three-phase AC power supply 1, and sequentially turns on the switches SA, SB, and SC in synchronization with the three-phase AC power supply 1 every 1/3 cycle, and switches S1 to S1.
S8 is synchronized with the three-phase AC power supply 1 and the three-phase AC power supply 3
Turn on alternately at double frequency. FIG. 2 shows an example of the switching pattern and the voltage waveform of each part. Va is the input voltage waveform, and VnN is obtained by turning on and off the self-extinguishing semiconductor elements S1 to S8 according to the switching pattern. Further, the phase voltage VAN is applied to the self-extinguishing semiconductor elements S1 to S1 while the bidirectional self-extinguishing semiconductor element SA is turned on.
It is obtained by turning S8 on and off. Similarly, the phase voltage VBN and the phase voltage VCN are obtained. Also, the interphase voltage V
AB is obtained from the difference between VAN and VBN. FIG. 3 shows an example of the bidirectional self-arc-extinguishing semiconductor elements SA, SA, SC and the self-arc-extinguishing semiconductor elements S1 to S8. (A) is an example of the self-extinguishing type semiconductor elements S1 to S8, in which a diode 23 and a transistor 24 are connected in anti-parallel. (B) is an example of a bidirectional self-extinguishing type semiconductor element SA, SB, SC, in which diodes 25a to 25d are bridge-connected, and a transistor 26 is further connected.

[0007]

According to the present invention, as described above, since the interphase voltage of the three-phase full-wave diode rectifier circuit 5 has a stepwise waveform of 24 steps, the input current waveform also has a stepwise waveform of 24 steps. The harmonics contained in the input current are reduced, the distortion of the voltage waveform of the three-phase AC power supply is suppressed, and the input power factor is also improved. Moreover, since a transformer is not required for the input, the device can be downsized.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a three-phase rectifier circuit of the present invention.

FIG. 2 is a diagram showing a switching pattern of the rectifier circuit of the present invention and a voltage waveform of each part.

FIG. 3A shows an example of self-arc-extinguishing type semiconductor devices SA, SB, SC used in the three-phase rectifier circuit of the present invention,
(B) is a figure showing an example of bidirectional self-extinguishing type semiconductor elements S1-S8.

FIG. 4 is a diagram showing a general example of a conventional three-phase rectifier circuit.

[Explanation of symbols]

 1 3 Phase AC Power Supply 2 AC Reactor 3 AC Reactor 4 AC Reactor 5 3 Phase Full Wave Diode Rectifier Circuit 17 Single Phase Transformer 18 Single Phase Transformer 19 Capacitor 20 Capacitor 21 Load 22 Capacitor 23 Diode 24 Transistor 25 Diode 26 Transistor SA Both Directional self-extinguishing semiconductor element SB Bidirectional self-extinguishing semiconductor element SC Bidirectional self-extinguishing semiconductor element S1 Self-extinguishing semiconductor element S2 Self-extinguishing semiconductor element S3 Self-extinguishing type Semiconductor element S4 Self-extinguishing semiconductor element S5 Self-extinguishing semiconductor element S6 Self-extinguishing semiconductor element S7 Self-extinguishing semiconductor element S8 Self-extinguishing semiconductor element

Claims (1)

(57) [Claims] 1. An AC reactor is connected in series between an input terminal of each phase of a main conversion circuit composed of a three-phase full-wave diode rectifier circuit and a three-phase AC power supply, and an input terminal of each phase of the main conversion circuit. Is connected to one end of three switches of the first group, the other ends of the three switches are commonly connected, and a single-phase self-excited conversion circuit is connected to the connection point. Is a group of two switches connected in series with each other. A second group of switches, each of which is composed of four sets, is connected in parallel to the DC side of the main conversion circuit, and two switches are connected in series. A capacitor is connected in parallel to the DC side of the main conversion circuit, one end of the primary winding of the first single-phase transformer is connected to the midpoint of the two switches of the first set, and the other end is connected to the second set. Connect to the midpoint of the two switches and connect one end of the primary winding of the second single-phase transformer to the second set of two switches. Connected to the middle point of the switch and the other end to the middle point of the two switches of the fourth set, and connecting the secondary windings of the first single-phase transformer and the second single-phase transformer in series. Then, one end thereof is connected to the commonly connected terminals of the three switches of the first group, and the other end thereof is connected to the midpoint of the two capacitors, and the three of the first group are connected. The switches are sequentially turned on every 1/3 cycle in synchronization with the three-phase AC power supply, the four sets of switches in the second group are synchronized with the three-phase AC power supply, and the frequency is three times that of the three-phase AC power supply. 3 phase rectifier circuit that turns on alternately with.