| 摘要 |
PURPOSE:To conduct positive restart without generating overcurrents by supplying exciting currents and generating induced voltage on a long service- interruption time. CONSTITUTION:When a motor 4 is restarted under the state in which a service- interruption period is long and residual voltage is extinguished in the motor 4, a CPU 6 performs excitation for a fixed time by operation frequency (f) and voltage V before service interruption by detecting the recovery of service power of a commercial power supply 1, a gate for an inverter 3 is interrupted once, and the induced voltage and phase of the motor 4 are acquired from outputs from a rectifier 11 and a comparator 19. The rotational frequency of the motor 4 is obtained from a period at the first three cycles of induced voltage in said induced voltage and phase, voltage is determined at four cycles, and operation at a second step is started at five cycles. The inverter 3 and the phase of induced voltage are conformed from the output from the comparator 19 in case of the operation. According to such control, pick-up start is commenced. |
