| 摘要 |
PURPOSE:To quickly restart an AC motor by immediately turning on a main switch when the charged voltage of a smoothing capacitor between a power source side PWM converter and load side PWM becomes higher than a prescribed value by turning on an auxiliary switch which is connected in series with a resistance before turning on the main switch. CONSTITUTION:A series circuit of a charging resistance 5 and auxiliary switch 4 is connected in parallel with a main switch 2 which connects three-phase AC power source 3 to a power source side PWM inverter 1. By charging a smoothing capacitor 7 with the direct current outputted from the inverter 1, a load side PWM inverter 6 is driven. An AC motor 8 is driven by means of the VVVV outputted from the inverter 6. The terminal voltage of the capacitor 7 is inputted to a control circuit 17 after detection and, when the terminal voltage is higher than a prescribed value, the main switch 2 is turned on and the auxiliary switch 4 is turned off. Therefore, the anxiety of passengers can be reduced, since the AC motor 8 can be restarted quickly after the power supply is restored from a momentary break. |
