| 摘要 |
PURPOSE:To enable to protect an element under any drive conditions while operating a motor in a stable range that the motor does not cause stalling by providing the second current level setter determined from the characteristics of the motor. CONSTITUTION:The first current level setter 5 for setting an element protecting level, and the second current level setter 7 for setting a current so as not to exceed stopping/starting torque point slip determined in cooperation with load induction motor characteristics and V/f ratio during present outputting are provided. A current level setter 8 selects either smaller one, but can operated in a stable range without stalling or damaging the element even if any V/f is set and driven or even if any kind of motor is coupled by controlling to decrease the frequency or stop the increase in the frequency so as not to reach the slip frequency or higher of the level current. |
