JPH0247132B2 - GYAKUHEIRETSUSAIRISUTATENKOSOCHI - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an anti-parallel thyristor ignition device that alternately ignites two sets of main thyristors connected in parallel with opposite polarities by an optically auxiliary thyristor.
In particular, the protection function is provided by a circuit configuration that is relatively simple and can be manufactured at low cost.

Conventionally, this type of thyristor ignition device:
As shown in FIG. 1, two main thyristors 1 and 2 connected in parallel with opposite polarities are each
A single optically auxiliary thyristor 3 connected in series to a current limiting resistor 4 via diodes 5A, 5C and 5B, 5D connected in series with each other with opposite polarities.
An anti-parallel thyristor ignition device is known in which thyristor ignition is alternately ignited.

In order to protect the main thyristors 1 and 2 from overvoltage application in such a conventional ignition device, breakover diodes 12A and 12B and reverse blocking diode 11 are generally used as shown in FIG.
A and 11B are connected in series with current limiting resistors 10A and 10B, respectively, and connected between the anodes and gates of main thyristors 1 and 2, thereby creating a protection circuit for each main thyristor 1 and 2 individually. was established. Therefore, the conventional thyristor ignition device of this type has the disadvantage that the circuit configuration is complicated and expensive in order to provide the protection function.

An object of the present invention is to provide an anti-parallel thyristor ignition device that eliminates the above-mentioned conventional drawbacks, provides an overvoltage protection function to the main thyristor, and enables inexpensive ignition with a simple circuit configuration. It is in.

That is, the anti-parallel thyristor ignition device of the present invention is an anti-parallel thyristor ignition device in which two sets of main thyristors connected in parallel with opposite polarities are ignited alternately by an optically auxiliary thyristor, which has a breakover characteristic. The device is characterized in that an element is connected in parallel to the optically auxiliary thyristor either directly or via a resistor.

The present invention will be described in detail below with reference to the drawings.

First, an example of the most basic circuit configuration of the ignition device of the present invention is shown in FIG. The illustrated configuration includes a breakover diode 8 and a current limiting resistor 9 of opposite polarity in a series connection circuit of an optically auxiliary thyristor 3 and a current limiting resistor 4 in the conventional anti-parallel thyristor ignition device shown in the first diagram.
This is a series connection circuit connected in parallel.
Therefore, a breakover diode 8 is connected in parallel with the optically auxiliary thyristor 3 with opposite polarity.
can be replaced with a circuit element exhibiting similar breakover characteristics, such as a combination of a thyristor and a Zener diode, and each of the diodes 5A to 5D is connected to the voltage applied to the main thyristors 1 and 2. It is for selecting the main thyristor to be fired by applying gate current alternately according to the polarity, and each diode 6A, 6B is
This is to prevent voltage from being applied to the gate electrodes of the main thyristors 1 and 2, and each resistor 7
A and 7B are for suppressing the gate current from becoming excessive.

the main thyristor 1 to be fired as described above;
In the bridge circuit of diodes 5A to 5D that performs selection 2, the AC terminals are connected to the gate electrodes of the main thyristors 1 and 2, and the DC terminals are connected to the optical auxiliary thyristor 3 and the breakover diode, respectively. The current limiting resistors 4 and 9 are bridged by anti-parallel connection via the current limiting resistors 4 and 9, or the current limiting resistors 4 and 9 can be used in common or completely eliminated to connect the optical auxiliary thyristor 3 and the breakover diode 8. It is also possible to directly connect them in antiparallel. In such a configuration, when the optically auxiliary thyristor 3 receives the optical trigger signal,
A gate pulse current is sent out and applied to the main thyristors 1, 2 via diode bridges 5A-5D. Therefore, the main thyristors 1 and 2 are alternately fired by the gate current flowing depending on the polarity of the applied voltage. For example, when the anode potential is positive with respect to the cathode potential of the main thyristor 1, [6A
→5A→4→3→5D→1], the gate current flows and the main thyristor 1 fires, and when the anode potential is positive with respect to the cathode potential of the main thyristor 2, the gate current flows through the path of [6B→5C→ 4→3→5B
→2], the gate current flows and the main thyristor 2 fires.

During such ignition operation, if the forward voltage of either the main thyristor 1 or 2 exceeds a predetermined voltage value, a breakover diode 8 is installed to protect the main thyristor from destruction due to the application of overvoltage. conducts beyond the breakover voltage, and depending on the polarity of the voltage applied to the main thyristors 1 and 2, a gate current flows through the main thyristor to which the overvoltage is applied through a path similar to the above-mentioned path during normal ignition. emergency ignition. For such an emergency ignition, a light emitting diode may be connected in series with the breakover diode 8 to monitor the generation of gate current at the time of the emergency ignition.

Next, in another configuration example of the ignition device of the present invention shown in FIG. An antiparallel thyristor rectifier circuit having the same circuit configuration as the arc device but omitting the optically auxiliary thyristor was connected in cascade, and each was connected in series by a single optically auxiliary thyristor 3 via pulse transformers 13A and 13B. The main thyristors 1, 1' and 2, 2' are fired alternately, and a breakover diode 8 for overvoltage protection is connected in antiparallel to the single optical auxiliary thyristor 3. 1, 1', 2,
2' is protected from destruction due to overvoltage application in the same manner as described above. Regarding the number of cascade-connected stages of such anti-parallel connected thyristor rectifier circuits, the pulse transformers 13A and 1 are connected to the AC terminals of the diode bridges 5A to 5D, respectively, whose DC terminals are bridged by the optically auxiliary thyristor 3.
If the number of 3B secondary windings is increased according to the number of stages, it is possible to have any desired number of stages, but in reality, it is difficult to achieve the desired number of stages, but in reality, the performance of pulse transformers, optically auxiliary thyristors, etc., expansion costs, etc. The number of cascade connections should be appropriately selected by taking this into account.

Next, in still another configuration example of the ignition device of the present invention shown in FIG. The pulse transformer 13 in the ignition device of each stage is connected in cascade in two stages.
The secondary windings A and 13A' and 13B and 13B' are connected in parallel, respectively.
Even if a fault occurs in the anti-parallel thyristor ignition device of either the upper or lower stage, the gate current can be supplied to the main thyristor of the faulty stage using the gate pulse current in the anti-parallel thyristor ignition device of the other stage. It is set as. Therefore, in each pulse transformer 13A, 13A' and 13B, 13B' whose secondary windings are connected in parallel, one winding of the two secondary windings of one pulse transformer is connected to the other pulse transformer. is connected to the gate electrode of the main thyristor of the stage to which it belongs, and connected to the gate electrode of the main thyristor of the stage to which the other pulse transformer of one winding belongs. Therefore,
Although it is expensive to install an optical auxiliary thyristor for ignition and a breakover diode for protection in each stage, even if a failure occurs in the ignition device of one stage, the gate current of the other stage can be diverted. Since it is possible to fire four or more main thyristors at any time, it is extremely effective when particularly high reliability is required.In addition, if the number of secondary windings of the pulse transformer is increased, cascade connection is possible. The number of stages can be increased arbitrarily within the possible range.

As is clear from the above description, according to the present invention, as an anti-parallel thyristor ignition device having an overvoltage protection function, a light auxiliary thyristor and a breakover diode are combined to form an ignition device equivalent to a light auxiliary thyristor for ignition. During normal operation, a gate current is supplied to the main thyristor via the optically auxiliary thyristor by an optical trigger signal, and in an emergency when the forward voltage of the main thyristor exceeds a predetermined value, the breakover diode is supplied to the main thyristor. Since the gate current is supplied to the main thyristor via the thyristor for emergency ignition, the number of circuit elements for providing protection functions can be reduced compared to conventional methods, simplifying the circuit configuration and reducing manufacturing costs. can be reduced.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing the circuit configuration of a conventional anti-parallel thyristor ignition device, Fig. 2 is a circuit diagram showing a circuit configuration with the same protection function, and Fig. 3 is a circuit diagram showing the circuit configuration of a conventional anti-parallel thyristor ignition device. FIGS. 4 and 5 are circuit diagrams showing other configuration examples, respectively. 1, 1', 2, 2'...main thyristor, 3, 3'
...Light-assisted thyristor, 4, 4', 7A, 7A',
7B, 7B', 9, 10A, 10B...Resistance, 5
A, 5A', 5B, 5B', 5C, 5C', 5D, 5
D', 6A, 6A', 6B, 6B', 11A, 11B,
14A, 14A', 14B, 14B', 14C, 1
4C', 14D, 14D'...Diode, 8, 8',
12A, 12B...Breakover diode,
13A, 13A', 13B, 13B'...Pulse transformer.

Claims (1)

[Claims] 1. In order to alternately fire two sets of main thyristors connected in parallel with opposite polarities by an optically auxiliary thyristor, the optically auxiliary thyristor is connected between the DC side terminals of a diode bridge, and the In an anti-parallel thyristor ignition device in which each AC side terminal is connected directly or indirectly to the gate of a separate main thyristor, a circuit element having breakover characteristics is connected in parallel to the optical auxiliary thyristor either directly or through a resistor. An ignition device for an anti-parallel thyristor characterized by: