JPS602869B2 - Thyristor power supply circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thyristor chopper circuit, and particularly to an improvement in the circuit for allowing sufficient holding current and commutation current to flow during startup or near no-load.

In Fig. 1, 1 is a power supply, 2 is a thyristor chopper circuit, which is composed of a main thyristor, a commutating thyristor, a commutating capacitor, and a commutating reactor.The voltage applied to a load 3 is controlled by the phase angle control of the thyristor chopper circuit 2. control. The thyristor chopper circuit 2 is often used for field control of motors, generators, etc.
In order to suppress this, a reactor 4, a resistor 5, and a capacitor 6 are inserted as filters. Further, 7 is a freewheel diode. With a load that has a very large inductance such as a power coil, even if the main thyristor of thyristor chopper circuit 2 is turned on when starting the chopper, the load current will not rise easily because the inductance of load 3 is large. The holding current of the main thyristor cannot be secured, and the main thyristor ends up being turned off. Furthermore, since the load of the output filter capacitor 6 is difficult to flow to the load side, the current flows backward through the reactor 4 and tries to flow to the chopper side, which also has the undesirable effect of reducing the holding current. On the other hand, in the thyristor chopper circuit 2, after the main thyristor is turned on, the auxiliary thyristor is turned on to flow commutated current and turn off the voltage applied to the load. Because of the reverse current, the commutation capacitor cannot be sufficiently charged in order to obtain sufficient commutation current, which may cause commutation failure. FIG. 2 shows a case where a resistor 10 is inserted to obtain a holding current, but a capacitor 6
If the discharge current is large, the effect will be small, and there is a drawback that the capacitance of the resistor 10 must be increased in order to increase the effect.

The object of the present invention is to eliminate the above-mentioned drawbacks and to obtain a thyristor chopper circuit which can obtain sufficient holding current and commutation current even during startup.

FIG. 3 shows one embodiment of the present invention, in which 1 is a power supply, 2 is a thyristor chopper circuit, 3 is a load, a reactor 4, a resistor 5,
The capacitor 6 constitutes an output filter, and the freewheel diode 7 is similar to the conventional circuit, but in the present invention, a diode 11 is connected between the freewheel diode 7 and the thyristor chopper circuit 2,
Furthermore, a dummy load resistor 10 is connected between the thyristor chopper circuit 2 and the diode tortoise.

On the other hand, two or more thyristor chopper circuits 2 may be operated in parallel connection, and a case where two circuits are connected in parallel is shown in FIG. 4. In the figure, 1 is a power supply, 2-1 and 2-2 are both thyristor chopper circuits, and an output filter is composed of a reactor 4, a resistor 5, and a capacitor 6, and a freewheel diode 7 and a load 3. The locations are the same as before, but the thyristor chopper circuits 2-1, 2-2
In order to connect them in parallel, coupling diodes 13-1 and 13-2 are used. The circuit for securing the holding current consists of the first circuit of the thyristor chopper, the output of the second circuit, and the coupling diode 1.
Coupling diodes 14-1 and 14-2 of the dummy load resistor 10 are connected between 3-1 and 13-2. The cathodes of the diodes 14-1 and 14-2 are connected in common and connected to the dummy load resistor 10. In the embodiment shown in FIG. 3, when starting the chopper, the main thyristor of the thyristor chopper circuit 2 is turned on.
The dummy load resistor 10 has a resistance value that allows the main thyristor's holding current to flow sufficiently, so the main thyristor is completely turned off.
It becomes N. When the main thyristor is turned on and a voltage is applied to the capacitor 6 and it is charged, the capacitor 6 starts discharging, but because of the diode 11, there is no reverse flow and the current flowing through the dummy load resistor 10 does not decrease. Therefore, the holding current of the main thyristor can be ensured. In the case of FIG. 4, the coupling diodes 13-1, 13-2 can also block the current from the output filter capacitor 6.

Then, to ensure the holding current, a dummy load resistor of 10
A current is passed through the diodes 14-1 and 14-2.
In this case, the diodes 14-1 and 14-2 also serve as diodes for coupling the thyristor chopper circuits 2-1 and 2-2. FIG. 5 shows another modification of the invention.

This means that the parallel coupling of the thyristor chopper circuits 2-1 and 2-2 is the coupling diode 13-1 and 13-2
The coupling diode 13 is used as a diode to prevent backflow.
In this example, a dummy load resistor 10 is inserted between the freewheel diode 7 and the freewheel diode 7. As described above, according to the present invention, by blocking the reverse current from the output side of the thyristor chopper circuit and ensuring a sufficient holding current by the dummy load resistor, the chopper can be started even with no load.

If a current is made to flow through the dummy load resistor to charge the commutation capacitor in order to obtain sufficient commutation current, commutation is possible even when there is no load. Once fully charged, commutation is carried out stably, and operation becomes stable.In addition, if it can be operated without load, it will be effective for uninterrupted power outages, etc., because it will stand by in the starting state when connected in parallel. be.

If the load current is large, use a diode for dummy load resistance.
Other than the diode, a diode with a small rating for the holding current will suffice.

Furthermore, when the load current is not so large, it is effective to reduce the number of diodes.

[Brief explanation of the drawing]

1 and 2 are circuit diagrams showing a conventional thyristor chopper circuit, FIG. 3 is a circuit diagram showing a thyristor chopper circuit according to an embodiment of the present invention, and FIGS. 4 and 5 are respectively circuit diagrams showing a thyristor chopper circuit according to an embodiment of the present invention. FIG. 3 is a circuit diagram showing another embodiment of the present invention. 1...Power source ~ 2,2-1,2-2...Thyristor chopper circuit, 3...Load, 4...Reactor, 5...Resistor, 6 ...Capacitor, 7
...Furi mountain wheel diode, 10...
Dummy load resistance, 11...diode, 13-1, 13
-2...Coupling diode, 14-1, 14-2
””River diode. Figure 1 Figure 2. Figure 3 Figure 4 Figure 5

Claims (1)

[Scope of Claims] 1. In a thyristor chopper circuit, which is composed of a main thyristor, a commutating thyristor, a commutating capacitor, and a commutating reactor, a freewheeling diode is connected to the output side, and the freewheeling diode and the chopper circuit A thyristor chopper circuit, characterized in that a diode for reverse current prevention is connected between the thyristor chopper circuit and a dummy load resistor is connected between the diode and the chopper circuit. 2. A patent characterized in that chopper circuits are connected in parallel via a coupling diode, the anode side of the diode is connected between the coupling diode and the chopper circuit, and the cathode side of the diode is commonly connected to a dummy load resistor. A thyristor chopper circuit according to claim 1.