POWER CONVERTER

PURPOSE:To prevent damage of a power converter from spreading and causing a secondary trouble by detecting the magnitude of reverse bias voltage or current between the control terminal of a gate turn ON thyristor (GTO element) and a reference potential applying terminal and then controlling the power converter based on the detection results. CONSTITUTION:Before a GTO element 6 constituting an inverter unit 3 begins switching operation, a detecting section 9 detects a reverse bias voltage VGK to be applied between the gate and cathode of each GTO element 6 from a reverse bias start signal section 10 through a gate driver 7. Upon detection of an abnormal reverse bias voltage, a gate logic section 8 stops operation of the inverter unit 3, i.e., the switching operation of the GTO element. According to the invention, damage of the inverter unit 3 including the GTO element 6 can be prevented from spreading to cause a secondary trouble.