SMOOTH STARTING OF SLIP RING INDUCTION-MOTORS

Starting of three-phase wound rotor induction motors by stepped resist ances added in the rotor circuit suffers from several problems. This p aper suggestes a novel method of starting by inserting a parallel comb ination of resistance, inductance and capacitance in the rotor circuit . The proposed method guarantees a smooth and high starting torque ove r most of the starting period besides a controlled starting current. A mathematical model is developed based on a frequency domain quasi-ste ady state equivalent circuit. An optimization technique is, then, appl ied to determine the values of the rotor added elements such that mini mum starting time is achieved subject to current and torque constraint s. Experimental verification has been carried out, and the computed re sults are in good agreement with the measured values.