| 摘要 |
PURPOSE:To avoid dangerous state, which may cause fault, positively by preventing an induction motor from running over a stop position due to frequency drop. CONSTITUTION:The inverter unit for controlling the rotational speed of an induction motor 3 through frequency control comprises a load current detecting circuit 6, an overvoltage detecting circuit 4, a stall preventing circuit 7 for controlling the frequency to reduce the load current and regenerative energy upon detection of overcurrent or regenerative overvoltage, a circuit 9 for deciding the operating state of the induction motor 3, and a circuit 8 for controlling the stall preventing circuit 7 according to a decided operating state. When the operating condition deciding circuit 9 makes a decision that the induction motor 3 is in decelerating state, the stall preventing circuit 7 is stopped. |
