EFFICIENCY IMPROVEMENT OF INDUCTION MOTOR DRIVE WITH VVCF CONTROL

This paper deals with the algorithm and implementation that improves the efficiency of three-phase induction motors by controlling the applied voltage. The applied voltage is controlled by the ac voltage controller, a VVCF (Variable Voltage Constant Frequency) system. The minimum input power control is implemented with a single-chip microprocessor-based digital controller. In order to avoid the loss-of-speed under an abrupt increase of load, a novel speed limiting method using the voltage across the switching elements is proposed Experimental results show that a considerable efficiency improvement has been achieved for an induction motor under light load factor.