| 摘要 |
PURPOSE:To prevent excessive current flow even upon short circuit of a semiconductor element by closing a contactor based on specific conditions after application of a gate signal onto a semiconductor switching element constituting an inverter circuit. CONSTITUTION:A first contactor 2 and a second contactor 3, connected in series with a charging current limiting resistor 4, are connected in series with a DC power supply and the output of the series circuit is fed through filter circuits 5-7 thus constituting an input circuit of an inverter. When the inverter is started, gate signals are applied on semiconductor switching elements 8a-8f constituting an inverter circuit 8 upon closing of the first contactor 2. Upon elapse of a predetermined time, it is confirmed that the output of a voltage detector 7 for the filter circuits 5-7 is higher than a set value and then the second contactor 3 is closed. According to the constitution, excessive current is blocked from flowing into the input circuit upon failure of the semiconductor switching elements 8a-8f in the inverter. |
