METHOD AND SYSTEM FOR LIMITING CURRENT OUTPUT BY SPEED CONTROLLER WHICH OPERATES ACCORDING TO V/F CONTROL LAW

摘要

PROBLEM TO BE SOLVED: To enable the limitation of a current at overload while maintaining the performance of a motor driven in V/F type control law.

SOLUTION: Relating to a method of limiting the current in the output of a speed controller (V) for a three-phase asynchronous motor (M), the above speed controller (V) operates by pure V/F type control law (LC). In the above method, a revised value to the frequency (Wstat) of a stator is computed, using a limiting function, so as to get the revised frequency (Wstatc) of the stator in the V/F type voltage control law (LC), and it is applied to that. Next, the control voltage (Vqref) to be applied to a motor is obtained, according to the revised frequency (Wstatc) of this stator, by the V/F type voltage control law (LC). This invention also relates to a current limiting system which executes the above method.

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