| 摘要 |
PCT No. PCT/JP87/00623 Sec. 371 Date Jun. 6, 1988 Sec. 102(e) Date Jun. 6, 1988 PCT Filed Aug. 21, 1987 PCT Pub. No. WO88/01450 PCT Pub. Date Feb. 25, 1988.An apparatus for controlling an adjustable-speed alternating current motor coupled to drive an elevator cage. The apparatus includes a converter connected to a source of AC power for converting the AC power into DC power, an inverter connected through relatively positive and negative conductors to the converter for inverting the DC power into DC output power having adjustable frequency, voltage magnitude, and current magnitude to drive the motor, and a control circuit for controlling an inverter to drive the motor at an adjustable speed. When a power failure occurs, the control circuit prevents flow of power through the converter to the power source and reduces the current magnitude of the inverter output power to a predetermined minimum limit enough to maintain a synchronous relationship between the inverter and the motor. When the power failure continues for a predetermined time, an electric resistor is connected between the relatively positive and negative conductors to provide a dynamic braking of the motor. |
