| 摘要 |
PURPOSE:To prevent the occurrence of start shock by breaking an electromagnetic contactor, after causing excitation components of currents to flow in an induction motor in order to demagnetize second magnetic flux, when an elevator is stopped. CONSTITUTION:When a start command 16 is issued, a main-circuit contactor 15 is made, the command 16 is sent to the CPU of a voltage frequency controller 7, and on the basis of the command of the CPU the exciting current component of a forcing pattern is generated for a specified time from an exciting current commanding device. Next when the elevator moves and stops, the start command is removed, its contact is broken, an exciting current component of a demagnetizing pattern is generated for the CPU's operation for a specified time to demagnetize secondary magnetic flux, and the main-circuit contactor 15 is broken after demagnetization. As the main-circuit contactor 15 is broken after demagnetizing the secondary residual flux completely, in this way, so when restarted next time overexcitation of the secondary flux does not occur, even if a forcing pattern of a specified exciting current is generated, and a weighting apparatus does not shift at the time of start. |
