JPH0783602B2 - Voltage type inverter device - Google Patents

Description

The present invention relates to an improvement of a charging circuit in a voltage type inverter device, and more particularly to a quick-acting fuse and The present invention relates to a voltage type inverter device capable of protecting a capacitor.

(Prior art) Due to the progress of high power transistors and drive technology for controlling them, and the demand for energy crisis, energy saving, and equipment capacity saving, inverters have been widely used in general industrial equipment, home appliances, vehicles, elevators, etc. ing. Most of these are voltage type inverters having a smoothing capacitor in the main circuit. By the way, the voltage-type inverter has a large capacitor in the main circuit, so if the power supply is turned on at startup as it is, the impedance of the load is very small, so a large inrush current flows instantly, and the rectifier and fast-acting fuse are blown. To do.

In order to prevent such problems, generally, on the AC side,
Alternatively, a capacitor pre-charging circuit is provided on the DC side to charge once through the limiting circuit, and after charging is completed, this charging circuit is short-circuited by the main contactor or disconnected to start normal inverter operation. An example of a conventional circuit in which a preliminary charging circuit is provided on the AC side will be described with reference to FIG.

In the figure, 1 is a three-phase AC power supply, 2a is an exciting coil of the pre-charging contactor 2, 3a is an exciting coil of the main contactor 3, 4 is a main contact of the main contactor 3, and 5 is a main contact of the pre-charging contactor 2. Is. Reference numeral 6 is a limiting resistor that is connected in series to the main contact 5 of the precharging contactor 2 to control the inrush current to the capacitor, and 7 is a fast-acting fuse that is connected in series to the main contact 4 of the main contactor 3. The main contact 5 path of the charging contactor 2 is also guided to the output side via the fast-break fuse 7. Reference numeral 8 is an AC timer that operates with the AC power supply output obtained through the quick-break fuse 7, and 9 is a full-wave rectifier for the output of the three-phase AC power supply 1 through the fast-break fuse 7.
Phase bridge type rectifier, 10 is a smoothing capacitor,
This is for smoothing the rectified output of the rectifier 9.
Reference numeral 11 denotes a discharge resistor for discharging the electric charge of the smoothing capacitor 10, which is connected in parallel to the smoothing capacitor 10 via a normally closed contact 16. Further, 12 is a normally-open contact of an operation preparation command (not shown), 13 is a normally-open contact of the safety circuit, which are connected in series with the exciting coil 2a of the precharging contactor, and are connected between the DC buses 17a and 17b. To be done. Further, 14 is a normally open contact of the AC timer 8 and is the exciting coil 3a of the main contactor.
Is connected in series and is connected between the DC buses 17a and 17b via the normally open contact 13 of the safety circuit 13. Further, 15 is a normally-open contact of the precharging contactor 2, which is used as a contact for turning on / off the timer 8.

The normally closed contact 16 is also a normally closed contact of the precharging contactor 2.

In such a configuration, when the safety circuit is now established and the normally open contact is closed, and then the operation preparation command is issued and the normally open contact 12 for the operation preparation command is closed, the exciting coil 2a of the precharge contactor is attached. The main contact 5 of the precharging contactor 2 is energized. Then, the output of the three-phase AC power supply 1 enters the rectifier 9 through the limiting resistor 6 and the quick-break fuse 7, is rectified, and then applied to the smoothing capacitor 10. As a result, the smoothing capacitor 10 is charged with the current value of the limiting resistor 6.
Further, the AC timer 8 starts counting at the same time when the precharging contactor operation starts, and operates when the preset charging time elapses to close the normally open contact 14 of itself. Therefore, the exciting circuit of the main contactor 3 is closed and the exciting coil 3a is energized, so that the main contactor 3 operates. When the main contactor 3 operates, the preliminary charging circuit is short-circuited (or disconnected), and then the inverter operation mode is entered. By the way, as shown in FIG. 3 (a), when a fault such as a ground fault or a voltage drop occurs in the three-phase AC power supply 1 during operation, the pre-charging contactor 2 may be turned off first and the main charging contactor 2 may be turned off. It is conceivable that the power supply is restored as shown in FIG. 3 (b) before the contactor 3 is turned off (see FIGS. 3 (c) and 3 (d)). At this time, the smoothing capacitor 10 is turned off, and the normally-closed contact 16 of the precharger contactor 2 is turned off.
As a result, discharge is started through the discharge resistor 11 and the capacitor voltage drops (Fig. 3 (e)). When the power is restored while the main contactor 3 is still operating, the pre-charging circuit does not operate normally and the inrush current given by the following equation flows to the power circuit side (the circuit after the fast-acting fuse). .

(However, V _p : power supply voltage, R: power supply internal resistance, V _c : capacitor terminal voltage, c: capacitor capacity) And at this time, if the capacitor voltage of the smoothing capacitor 10 has dropped sufficiently,
The inrush current at this time (see FIG. 3 (f)) may destroy the fast-acting fuse 7 and the capacitor 10 (third part).
(See FIG. (G)).

(Problems to be Solved by the Invention) As described above, in the conventional pre-charging circuit, when the power source becomes abnormal and the power is recovered immediately, the pre-charging circuit may not operate normally. In this case, a voltage drop occurs due to the discharge of the smoothing capacitor during a power failure, and if the charging path via the main contactor is alive due to differences in holding current, follow this path to determine the charging voltage. An inrush current may flow through the reduced capacitor, which may blow the fast-acting fuse or destroy the capacitor.

Therefore, an object of the present invention is to prevent an abnormal operation of the pre-charging circuit caused by a power failure or a voltage drop within a relatively short time of the power source, and always operate in a normal procedure in any state. Another object of the present invention is to provide a voltage type inverter device capable of preventing the circuit from being damaged by an inrush current.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention provides a voltage type inverter main circuit that receives an AC power supply output supplied from the outside and converts it into a DC power supply. Is used as a power source and a self-holding operation is started during the starting operation to pre-charge the smoothing capacitor of the main circuit, and a pre-charging circuit is operated at the end of pre-charging to operate this pre-charging circuit. In a voltage type inverter device including a self-holding open / close switch circuit that separately supplies the AC power supply output to the main circuit and a discharging circuit that discharges the smoothing capacitor when the inverter device is stopped, The smoothing capacitor discharge circuit is provided with means for opening the discharge circuit while the open / close switch circuit is operating.

(Operation) When the apparatus is activated in such a configuration, first, the pre-charging circuit which is self-holding as the AC power source and starts the operation starts to pre-charge the smoothing capacitor of the main circuit. When the preliminary charging by the preliminary charging circuit is completed, the self-holding open / close switch circuit operates to electrically separate the preliminary charging circuit and supply the AC power output to the main circuit. This allows
The inverter device starts operation. It is assumed that the AC power supply becomes abnormal in such a state. As a result, both the self-holding type pre-charging circuit and the open / close switch circuit are released from self-holding, and the inverter device is stopped
The smoothing capacitor discharge circuit starts discharging the capacitor. When the abnormality is recovered, restart operation is performed to charge the smoothing capacitor by following the above-mentioned regular procedure, and then the inverter operation is started. It is possible to suppress the occurrence of inrush current. Further, it is assumed that, when the AC power supply becomes abnormal during the operation of the inverter device and immediately recovers, only the preliminary charging circuit is released from the self-holding due to the difference in the holding current. In such a case, in the past, the discharge circuit was activated and the inrush current might be generated at the same time when the power was restored.However, when the open / close switch circuit is operating in this device, the discharge circuit is in the open state, so There is no discharge of the capacitor through the circuit, maintaining the capacitor voltage. Therefore, it is possible to prevent the occurrence of an inrush current when the power supply is restored after the occurrence of an abnormality in the AC power supply in a short time. Therefore, it is possible to prevent the device from being damaged due to the generation of the inrush current and to obtain high reliability.

(Embodiment) An embodiment of the present invention will be described below with reference to FIG. In the figure, the same parts as those in FIG. 2 are designated by the same reference numerals, 1 is a three-phase AC power supply, 2a is an exciting coil 3a of the precharging contactor 2, and 3a is an exciting coil of the main contactor 3. Is a main contact of the main contactor 3, and 5 is a main contact of the pre-charging contactor 2. 6 is a limiting resistor which is connected in series to the main contact 5 of the pre-charging contactor 2 and limits the inrush current to the capacitor 10, and 7 is a fast-acting fuse which is connected in series to the main contact 4 of the main contactor 3. The path of the main contact 5 of the pre-charging contactor 2 is also guided to the output side via the quick-break fuse 7. Reference numeral 8 is an AC timer that operates on the output of the AC power source obtained through the fast-acting fuse 7, and 9 is the three-phase AC power source 1 through the fast-acting fuse 7.
Is a three-phase bridge type rectifier for full-wave rectifying the output of the rectifier, and 10 is a smoothing capacitor for smoothing the rectified output of the rectifier 9. Reference numeral 11 denotes a discharge resistor for discharging the electric charge of the smoothing capacitor 10, which is connected in parallel to the smoothing capacitor 10 via the normally closed contact 16 of the precharging contactor 2. Further, 12 is a normally open contact of an operation preparation command (not shown), 13 is a normally open contact of the safety circuit, these are connected in series with the exciting coil 2a of the precharge contactor,
Connected between DC buses 17a and 17b. A normally open contact 14 of the AC timer 8 is connected in series with the exciting coil 3a of the main contactor, and is connected between the DC busbars 17a and 17b via the normally open contact 13 of the safety circuit 13. Further, 15 is a normally-open contact of the pre-charging contactor 2, which is used as a contact for turning on / off the AC timer 8. When the AC timer 8 is turned on, it advances the count until it reaches the set count value, and activates its own contact 14.

Reference numeral 18 is a normally closed contact of the main contactor 3, which is a normally closed contact 16 of the precharging contactor 2 which is a discharge circuit, and a discharge resistance.
It is connected in series to 11 series circuits.

The basic configuration of such a preliminary charging circuit is the same as that of the conventional example, but the smoothing capacitor 10 is used in this device.
Of the main contactor 3 is connected in series with the normally-closed contact 16 of the precharging contactor 2 connected in parallel to the smoothing capacitor 10 which is a discharging circuit of FIG. Connect the closed contacts 18 in series,
The difference is that the discharge circuit can be opened when the main contactor 3 operates. The pre-charging operation and the main contactor closing conditions are the same as those described with reference to FIG.

In such a configuration, when the safety circuit is now confirmed, the operation preparation command is issued, and the normally open contact 12 is closed, the exciting coil 2a of the precharge contactor 2 is energized and the main contact 5 thereof is closed. This connects to the main contact 5.
The output of the three-phase AC power supply 1 flows through the limiting resistance 6, is rectified by the rectifier 9, and then is supplied to the smoothing capacitor 10 to charge it. At this time, the normally-closed contact 16 of the precharging contactor 2 is opened to open the discharge circuit, and the normally-opened contact 15 of the precharging contactor 2 is closed. On the other hand, the AC timer 8 starts counting when the normally open contact 15 is closed, and activates its own contact at the time when a preset value is counted. That is, the AC timer 8 is a smoothing capacitor.
It operates after waiting for the time corresponding to the charging time of 10 to complete the charging. As described in FIG. 2, the main contactor 3 operates when the AC timer 8 operates and short-circuits the preliminary charging circuit. It is assumed that the voltage drops during operation, for example, due to an abnormality in the power supply system. In this case, both of the contactors 2 and 3 are turned off. However, due to the difference in the holding current of the contactors, the power may be restored before the precharging contactor 2 is turned off first and the main contactor 3 is turned off. Conceivable. Even in this case, since the main contactor 3 of the smoothing capacitor 10 of the main circuit is not turned off, the normally-closed contact 18 of the main contactor 3 is in an open state, so that the discharging circuit is not formed and the smoothing capacitor 10 is charged. It is kept in the state of holding the electric charge. Therefore, even if the power supply returns to the normal state, the inrush current to the smoothing capacitor 10 does not flow because the terminal voltage of the smoothing capacitor 10 is high, and there is no concern that the fast-acting fuse 7 will be blown or the capacitor will be destroyed by the inrush current. . If the power failure continues for a long time, the main contactor 3 is turned off so that the normally closed contact 18 is also closed, and the normally closed contact 16 of the precharging contactor 2 which is off is also in the closed state. Therefore, a discharge circuit is formed, and the smoothing capacitor 10 starts discharging by this discharge circuit. At this time, even if the power is restored in the middle of discharging, the main contactor 3 is not turned on until the preliminary charging circuit operates, that is, the preliminary charging contactor 2 operates and the AC timer 8 operates, and therefore, The normal operation does not cause an inrush current. Therefore, it is possible to prevent the blowout of the fast-acting fuse or the failure due to the inrush current to the smoothing capacitor in the system in which the fuse is not provided.

As described above, the present apparatus uses the AC power supply as a power source in the voltage-type inverter main circuit that receives the output of the AC power supply supplied from the outside and converts it into DC, and starts the operation by self-holding during the starting operation. A pre-charging circuit for pre-charging the smoothing capacitor of the circuit and a pre-charging circuit which operates at the end of pre-charging by this pre-charging circuit to electrically separate the pre-charging circuit and which supplies the AC power output to the main circuit. A holding-type open / close switch circuit and a discharge circuit that discharges the smoothing capacitor when the inverter device is stopped are provided.At startup, the capacitor is charged by the preliminary charging circuit, and then the inverter operation is started. In a voltage type inverter device that suppresses current generation, the open / close switch circuit is operating in the discharge circuit of the smoothing capacitor. It is obtained by a structure provided with means for open the electric discharge circuit.

When the AC power supply becomes abnormal during the operation of such a device and it recovers immediately, even if only the pre-charging circuit is released from the self-holding due to the difference in holding current, the open / close switch circuit operates in this device. The discharging circuit keeps the circuit open while the capacitor is being discharged, and the discharging circuit does not discharge the capacitor, so that the capacitor voltage can be maintained. Therefore, it is possible to prevent the inrush current from being generated when the AC power supply recovers after a short time abnormality has occurred, so that the discharge circuit operates to lower the capacitor potential and generate inrush current at the same time when the power is restored. The risk of inviting is eliminated, and therefore, it is possible to prevent the occurrence of an inrush current after recovery in an abnormality of the AC power supply in a short time. Therefore, it is possible to prevent the device from being damaged due to the generation of the inrush current and to obtain high reliability.

The present invention is not limited to the embodiments described above and shown in the drawings, but can be appropriately modified and implemented within the scope of the invention.

[Effects of the Invention] As described above in detail, according to the present invention, it is possible to prevent malfunction and occurrence of inrush current due to malfunction when the power supply is restored after an abnormality has occurred in the AC power supply for a short time.
It is possible to provide a voltage source inverter device having features such that the device can be prevented from being damaged due to the occurrence of an inrush current and high reliability and safety can be secured.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a main part showing an embodiment of the present invention, and FIG.
FIG. 3 is a circuit diagram of a main part for explaining a conventional example, and FIG. 3 is a time chart for explaining its operation. 1 ... 3-phase AC power supply, 2 ... Precharger contactor, 2a
...... Excitation coil of pre-charging contactor, 3 ...... Main contactor, 3a …… Excitation coil of main contactor, 4 …… Main contactor of main contactor, 5 …… Main contact of pre-charging contactor, 6 …… Limiting resistance , 7 ... Fast-acting fuse, 8 ... AC timer, 9 ... Rectifier, 10 ... Smoothing capacitor, 11 ...
Discharge resistance, 12 …… Main circuit closing command contact, 13 …… Safety circuit confirmation signal contact, 14 …… AC timer normally open contact, 15 …… Preliminary contactor normally open contact, 16 …… Preliminary charging contactor Normally closed contacts, 17a, 17b ... DC busbar, 18 ... Normally closed contact of main contactor.

Claims (1)

[Claims] 1. A smoothing of the main circuit, wherein a voltage type inverter main circuit for converting an output of an AC power supply supplied from the outside into a DC is supplied with the AC power supply and self-holds to start an operation during a starting operation. Precharging circuit for precharging the capacitor for charging, and a self-holding type opening / closing circuit that operates at the end of precharging by the precharging circuit to electrically separate the precharging circuit and supply the AC power output to the main circuit. In a voltage type inverter device comprising switch means and a discharge circuit for discharging the smoothing capacitor when the inverter device is stopped, the open / close switch means is a main circuit switch for opening / closing a power supply path to the main circuit, The main circuit switch is interlocked with an auxiliary switch that operates in the opposite direction of the main circuit switch. The auxiliary circuit is connected in series to the discharge circuit of the sensor, and the pre-charging circuit interlocking switch means that is opened during self-holding of the pre-charging circuit in conjunction with the pre-charging circuit is connected in series to the series circuit. A voltage-type inverter device having the above-mentioned configuration.