| 摘要 |
PURPOSE:To prevent overheat of a transistor by a method wherein judgement is made as to whether closing of a bypass contactor is good or bad, and when the closing is not good, a driver is so informed. CONSTITUTION:A transistor TR is connected to a circuit of a motor 1 for power running. A bypass contactor 7 is connected in parallel with this transistor TR. A field-weakening resistor R is connected in parallel to a field coil 6 of the motor 1 for power running, while a contactor 17 is connected in series to the resistor R. A voltage detecting circuit 18 for detecting a voltage VCE between the collector and the emittor of the transistor TR. Moreover, a circuit 19 for judging whether closing and opening of the bypass contactor 7 is good or bad is connected to the circuit 18, and when the closing of the contactor 7 is bad, the failure is displayed in a display device 21 from the circuit 19. |
