| 摘要 |
PROBLEM TO BE SOLVED: To realize the V/f ratio to a motor equivalent to that when an inverter is used by providing a backup circuit to disconnect the motor from the inverter when the inverter is failed and to switch the motor to a commercial power supply, and a transformer to drop the voltage of the commercial power supply to the voltage of the inverter. SOLUTION: When an inverter INV1 is failed, a backup switch B1 is operated, and a normally close contactor C1b is closed, and at the same time, a normally open contactor C1a is closed. A motor M1 is disconnected from the inverter INV1 on the circuit to close a contactor Ca on a backup circuit 2 side. The motor M1 is driven by the power passing from a commercial power supply PS through the contactors Ca, C1a. The power supply voltage is dropped by the voltage corresponding to the voltage drop in the inverter by a transformer TR. Thus, the V/f ratio equivalent to that when the inverter is used even in the backup by the commercial power supply can be realized to the motor M1. |
