| 摘要 |
PURPOSE:To lower the thermal withstanding capacity of a resistor in a DC overvoltage suppressing circuit by delivering a gate ON signal to all turn OFF thyristors upon occurrence of short circuit failure in any one of them. CONSTITUTION:Upon failure of a turn OFF thyristor (GTO) 7-1 in a DC overvoltage suppressing circuit 4, for example, it is detected by a voltage detector 8-1 and a failure detector 11 for the element and a gate ON signal is delivered to all GTOs 7-1,..., 7-4 which are thereby turned ON. Since the energy stored in a capacitor 3 is shunted to resistors 6-1,..., 6-4 connected in series with the GTOs 7-1,...,7-4 in the DC overvoltage suppressing circuit 4, the energy which must be consumed by one resistor is reduced by a factor of four as compared with the energy stored in the capacitor. Consequently, the thermal withstanding capacity of the resistor 6 in the circuit 4 can be reduced. |
