| 摘要 |
PURPOSE:To provide an overload detecting device which can improve the operating performance of a motor irrespective of the starting of the motor from a hot state or cold state. CONSTITUTION:An overload detecting device is constituted of a current value squaring means 512, primary filter 513, overload comparator 515, initial value setting means 516, time counting means 53, backup storing means 52, and backup power supply 56. The means 512 squares the detected motor current Si to produce the square Sj of the motor current. The squared value Sj becomes a thermal value Stheta when it is processed by the filter 513. The comparator 515 outputs an error Er when the thermal value Stheta is larger than a prescribed reference value. When the power supply is interrupted, the time counting means 53 counts the time from the interruption to the restoration of the power supply. The initial value setting means 516 obtains an initial value Xo from the count value td of the counting means 53 and a stored value Xb when the power supply is restored and sets value Xo in the filter 513. |
