Abstract: The reactive power demand of asynchronous motor is mostly depended on the operation condition of its load. The exciting current variation of asynchronous motor from noload condition to stable onload condition was analyzed; and the analysis shows that the reactive power demand of the motor varies along with its operating mode. The reactive power compensation equipment for a motor must be selected according to its practical working mode.

Key words: asynchronous motor, magnetic field variation, exciting current, automatic compensation, static compensation, local compensation