To improve the reliability of this power converter, by detecting the trouble of a main switching element and a snubber circuit, and by monitoring the voltage and current of a snubber circuit part for inhibiting overvoltage and an overcurrent connected to the main switching element.
The voltage of a snubber diode 11 reaches zero voltage when one of a GTO 8, a by-passing diode 9 and a snubber capacitor 12 gets trouble and is short-circuited, and voltage reaches zero when snubber diode 11 itself gets trouble and is short-circuited. When the resistor of a snubber resistor 10 is disconnected, the voltage of the snubber capacitor 12 is left as it is charged up to DC voltage, and the voltage of the snubber diode 11 as a difference section with power-supply voltage is not increased up to power-supply voltage. Consequently, the short circuit of the snubber diode 11 and the disconnection of the snubber resistor 10 can also be detected in addition to each short circuit of the GTO 8, the by-passing diode 9 and the snubber diode 12 by monitoring the voltage of the snubber diode 11 by a voltage detector 21. Accordingly, the reliability of a power converter can be maintained.
EGUCHI YOSHIO
AIZAWA HIDETOSHI
