| 摘要 |
PURPOSE:To confirm safety by directly storing an output signal from a current detector under a state where a current command value is generated during stoppage of elevator and correcting the offset voltage during operation of elevator thereby delivering current command continuously even during stoppage and detecting failure of inverter stop signal generator. CONSTITUTION:Iu, Iv represent output signals from current detectors for detecting respective phase currents of an induction motor while Icu, Icv represent current command values. When an elevator stops causing stoppage of an inverter, only offset voltages appear in Iu, Iv and sample & hold circuits 24b, 25b store the outputs Iu, Iv as offset voltages Iou, Iov. Upon starting the inverter, the sample & hold circuits 24b, 25b enter into held state and output offset voltages Iou, Iov which are applied on the non-inverted input sides of differential amplifiers 12a, 13a, 14a thus correcting the offset voltage of the current detector. |
