| 摘要 |
In a control circuit for driving an induction motor wherein an AC voltage is converted into a direct current by a rectifying circuit and the direct current is converted into a signal of a variable voltage and frequency by means of a transistor inverter connected in parallel with a smoothing capacitor, a regenerative circuit is connected in parallel with the inverter, and a first monitoring circuit is provided for comparing the terminal voltage Vc of the smoothing capacitor and a first reference voltage E1 when braking is to take place. When the condition Vc >/= E1 holds, the transistor inverter is disabled but the regenerative circuit is allowed to operate. When the condition Vc < E1 holds, the transistor inverter is operated in the regenerative braking region. A second monitoring circuit is provided for comparing the smoothing capacitor terminal voltage Vc and a second reference voltage E2 (E2 > E1). When the condition Vc >/= E2 holds, both the transistor inverter and regenerative circuit are disabled immediately. |
