TORQUE AND CURRENT STRESS OF A 3-PHASE INDUCTION-MOTOR DUE TO NONSIMULTANEOUS SWITCH-ON

The paper discusses the ways for affecting the current and torque surg es originating due to non-simultaneous switch-on of feeding phases to a 3-phase induction motor. Here, the non-simultaneous switch-on is def ined to be that during which at first two phases are switched on (at a n instant defined with respect to the time course of voltage) and only then, with some delay, the switch-on of the third phase follows. The paper demonstrates that -when compared to a simultaneous switch-on of all 3 phases- proper control of non-simultaneous switch-on as defined above can reduce both the motor impact stress and the current surges s ubstantially. However, unproper successive switching-on may increase t hese unwanted phenomena. First, the present contribution brings an ana lytical solution for current and torque at zero revolutions and then, in the latter part, the influence of the controlled switch-on motor st art is discussed.