JP2010081665A - Converter device - Google Patents

Abstract

In a three-phase four-wire converter circuit, a smoothing capacitor of a three-phase side converter is reliably discharged with a simple configuration.
In a converter device provided with a three-phase converter circuit 51 for rectifying three-phase alternating current and a single-phase converter circuit 52 for rectifying any one of the three phases and a neutral point, a diode 5a and 5b and the normally closed contact 6 connect the first smoothing capacitor 31 and the second smoothing capacitor 32, and the voltage detector 21 detects the DC output terminal voltage of the single-phase side converter circuit. By opening and closing the closed contact 6, the electric charge of the first smoothing capacitor 31 is discharged to the second smoothing capacitor 32 side, thereby discharging the first smoothing capacitor 31 with a simple configuration when the three-phase AC power supply is cut off. It becomes possible to do.
[Selection] Figure 1

Description

  The present invention relates to a converter device that converts a three-phase AC power source into DC.

  2. Description of the Related Art Conventionally, a converter device that converts an alternating current power source into a direct current is most basic and widely known, which includes a bridge-connected diode and a capacitor that smoothes the output. In such a circuit, since the charge stored in the capacitor is consumed by the load, it is stored in the capacitor in the no-load state where the load is disconnected or in the state where the inverter connected as the load is stopped. Therefore, there is a safety problem that the electric charge is not discharged and the high voltage is maintained.

  In order to solve this, a method of connecting a discharging resistor to both ends of the capacitor is generally used. However, this resistor causes a problem that power is always consumed and efficiency is lowered.

  As a means to solve these problems at the same time, an open / close means is provided in series with the discharge resistor, and it is opened and closed according to the state of the load. There is an inverter device that consumes power (see, for example, Patent Document 1).

  Hereinafter, a conventional inverter device will be described with reference to the drawings. FIG. 2 is a configuration diagram of the inverter device described in Patent Document 1. In FIG. This inverter device includes a converter unit 1, an inverter unit 2, a smoothing capacitor 3, a brake resistor 4, and a brake switching transistor 5, and applies three-phase alternating current to the converter unit 1 from an input power supply 60. The inverter unit 2 outputs an alternating current having a predetermined voltage and a predetermined frequency to the induction motor 70. A normally closed contact 20a of the relay 20 is provided in series with the brake resistor 4 and in parallel with the brake switching transistor 5. The brake resistor 4 is normally closed separately from the brake switching transistor 5. The contact 20a is also brought into a conductive state, and a parallel circuit with the smoothing capacitor 3 is established.

  The voltage supplied to the converter unit 1 by the input power supply 60 is detected by the voltage detector 21, and the power supply voltage detected by the voltage detector 21 is input to the comparator 22. The comparator 22 detects the interruption of the input power supply 60 by comparing the power supply voltage detected by the voltage detector 21 with the comparison reference voltage.

  The relay drive circuit 23 of the relay 20 receives the output signal of the comparator 22, and stops energization of the relay 20 when the input power supply 60 is detected to be cut off.

  In addition, a manual switch 24 is connected to the relay drive circuit 23, and the relay drive circuit 23 prohibits power supply to the relay 20 from being stopped regardless of the inversion of the state of the manual switch 24 except when the interruption of the input power supply 60 is detected. .

  In this inverter device, when the input power source 60 is cut off, this is detected by the comparator 22, and the relay drive circuit 23 stops energization of the relay 20.

  As a result, the normally closed contact 20a of the relay 20 is closed, the brake resistor 4 is connected to both ends of the smoothing capacitor 3, and the smoothing capacitor 3 is discharged by the brake resistor 4.

As described above, in the conventional inverter device, the brake resistor and the relay are connected in series and the opening and closing of the relay is controlled, so that the electrolytic capacitor is surely discharged at the time of stopping while eliminating the power consumption during the normal time. It becomes possible.
JP-A-9-37562

  However, in the conventional configuration, the input power source is a three-phase four-wire type, a converter that supplies the three-phase power source to the inverter side, and a so-called single-phase power source composed of a neutral point and one of the three phases for the control circuit. In the case of a circuit configuration in which a converter to be supplied is provided, it becomes necessary to provide a discharge resistor for each converter.

  Further, when the load connected to the converter on the three-phase power source side is only an inverter, it is necessary to provide a control circuit for controlling the discharge circuit, resulting in an increase in the number of components.

  The present invention solves the above-described conventional problems, and in a circuit configuration in which a three-phase power converter and a single-phase power converter are provided side by side, the smoothing capacitor can be reliably discharged with a simple configuration. An object of the present invention is to provide a converter device that can be used.

  In order to solve the conventional problems, a converter device of the present invention includes a three-phase AC power source, a three-phase side converter circuit that rectifies and smoothes the three-phase AC, and one phase and a neutral point of the three-phase AC. A single-phase converter circuit that rectifies and smoothes so-called single-phase alternating current, a diode and a normally closed contact that connect the three-phase converter circuit and the single-phase converter circuit, and a DC output voltage of the single-phase converter circuit. By providing the voltage detector, the smoothing capacitor of the three-phase side converter circuit can be reliably discharged with a simple configuration.

  In the converter device of the present invention, the DC output terminal of the three-phase side converter circuit and the DC output terminal of the single-phase side converter circuit are connected by a normally closed contact and a diode, and the voltage at the DC output terminal of the single-phase side converter circuit is By opening and closing the normally closed contact, it becomes possible to discharge the smoothing capacitor of the three-phase converter circuit with certainty, and it is possible to reduce circuit parts compared to the conventional inverter device configuration Become.

  According to a first aspect of the present invention, there is provided a three-phase four-wire AC power source, a three-phase converter circuit including a first rectifier circuit and a first smoothing capacitor having a three-phase AC output as an input, and a three-phase AC output. A single-phase side converter circuit consisting of a second rectifier circuit and a second smoothing capacitor that receive the single phase and neutral point, and a voltage detector that detects the DC output terminal voltage of the single-phase side converter circuit. A diode and a normally closed contact are connected in series in a direction in which current flows from the positive DC output end of the first smoothing capacitor to the positive DC output end of the second smoothing capacitor, and the second smoothing capacitor A single-phase side converter that is detected by a voltage detector, in which a diode and a normally closed contact are connected in series in a direction in which current flows from the negative side DC output end of the first smoothing capacitor toward the negative side DC output end of the first smoothing capacitor. The converter device is characterized in that the normally closed contact is opened when the DC output terminal voltage of the inverter circuit exceeds a predetermined value, and the discharge of the first smoothing capacitor provided in the three-phase side converter can be simplified. It becomes possible to carry out reliably with a simple configuration.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a diagram showing an embodiment of a configuration of a converter device according to the present invention.

  In FIG. 1, 60 is a three-phase four-wire AC power supply (hereinafter referred to as three-phase power supply), 11 is a first rectifier circuit, and 12 is a second rectifier circuit.

  The first rectifier circuit 11 is supplied with the three-phase output of the three-phase power source 60 at the AC input terminal, and the first smoothing capacitor 31 is connected to the DC output terminal to constitute the first converter circuit 51. (Hereafter referred to as a three-phase converter).

  Also, one of the three-phase outputs of the three-phase power supply 60 and the neutral point are input to the AC input terminal of the second rectifier circuit 12, and the second smoothing capacitor 32 is connected to the DC output terminal. Thus, the second converter circuit 52 is configured (hereinafter referred to as a single-phase side converter).

  A load 41 and a load 42 are connected to the DC output terminals of the three-phase side converter 51 and the single-phase side converter 52, respectively.

  The diode 5a and the normally closed contact 6 are connected in series from the positive DC output end of the three-phase side converter 51 to the positive DC output end of the single phase side converter 52, and the negative side DC of the single phase side converter 52 is connected. A diode 5b and a normally closed contact 6 are connected in series from the output end toward the negative side DC output end of the three-phase side converter.

  The voltage detector 7 detects the DC output terminal voltage of the single-phase side converter 52, and the detected voltage is compared with a predetermined value by the comparator 8. Based on the result obtained from the comparator 8, the relay driving means 9 opens the normally closed contact when the voltage is higher than a predetermined value, that is, the relay driving means 9 energizes the relay coil 6a.

  In the above configuration, the predetermined voltage value to be compared by the comparator 8 is set lower than the DC output terminal voltage of the single-phase side converter at the normal time, and in the steady state after power-on, the voltage detector 7 The detected voltage always exceeds a predetermined value, and the normally closed contact 6 is normally open. Here, when the three-phase AC power supply 60 is cut off, the electric charge of the smoothing capacitor 32 is discharged by the load 42, and the voltage at the DC output terminal of the single-phase side converter circuit decreases. Thereby, when the voltage detected by the voltage detector 7 falls below a predetermined value, the energization of the normally closed contact 6 to the relay coil 6a is stopped, the normally closed contact 6 is closed, and the first diode 5a and the first diode 5a The electric charge stored in the first smoothing capacitor 31 is moved to the second smoothing capacitor 32 by the second diode 5b to be discharged.

  Here, as is clear from the relationship between the three-phase output of the three-phase power supply 60 and the neutral point output, the DC output terminal voltage of the first smoothing capacitor 31 in the steady state is the DC output terminal of the second smoothing capacitor 32. Since the voltage is about 1.7 times the voltage, when the normally closed contact 6 is closed and the second smoothing capacitor 32 is charged, the voltage rises to 1.7 times the normal voltage. The normally closed contact 6 is returned to the open state by the voltage detector 7 and the comparator 8.

  However, since the three-phase AC power supply 60 is cut off, the DC output terminal voltage of the first smoothing capacitor 32 decreases and falls below a predetermined value, so that the normally closed contact 6 is closed again. These states are repeated, and the process ends when the charge of the first smoothing capacitor 31 is discharged.

As described above, the smoothing capacitor of the three-phase side converter can be surely discharged by only detecting the DC output terminal voltage of the single-phase side converter, and the number of parts can be reduced.

  As described above, the converter device according to the present invention reliably discharges the smoothing capacitor of the three-phase converter with a small number of parts in a circuit configuration in which the three-phase converter circuit and the single-phase converter circuit need to be separated. It becomes possible.

The circuit block diagram of the converter apparatus in Embodiment 1 of this invention Circuit diagram of conventional inverter device

Explanation of symbols

60 Three-phase AC power source 1, 11, 12 Rectifier circuit 3, 31, 32 Smoothing capacitor 5a, 5b Diode 41, 42 Load 6 Normally closed contact 6a Relay drive coil 21 Voltage detector 22 Comparator 9 Relay drive means 4 Brake resistance 5 Switching transistor for brake 70 Induction motor 20 Relay 23 Relay drive circuit 24 Manual switch 51 Three-phase side converter 52 Single-phase side converter

Claims (1)

A three-phase four-wire AC power source having a neutral point, a three-phase side converter circuit comprising a first rectifier circuit and a first smoothing capacitor that receive the three-phase AC output of the three-phase four-wire AC power source; A second rectifier circuit having one phase of the three-phase four-wire AC power supply and a neutral point as inputs, and a single-phase side converter circuit including a second smoothing capacitor, and the second A voltage detector for detecting a DC terminal voltage of the smoothing capacitor, and a first diode in a direction in which a current flows from a positive DC terminal of the first smoothing capacitor toward a positive DC terminal of the second smoothing capacitor; And the normally closed contact is connected, and the second diode and the normally closed contact are connected in a direction in which current flows from the negative DC side of the second smoothing capacitor to the negative DC side of the first smoothing capacitor. The voltage detector Detected voltage, if it exceeds a predetermined setting value, and characterized in that the normally-closed contact to the open state, the converter device.

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