| 摘要 |
In a drive using an AC induction motor for moving a load in hoisting and lowering directions, a method for determining motor speed includes, in any order, the steps of selecting first and second voltage signals representing a maximum speed to be attained by the motor at rated output torque in the hoisting and lowering directions, respectively, and selecting a bias voltage. One of the voltage signals is combined with the bias voltage to obtain a feedback signal representing motor speed and the feedback signal is compared with a speed command signal to obtain a deviation signal representing the difference between actual and commanded motor speed. The drive is disabled if the difference is "out of" a predetermined range.
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