CAPACITOR EFFECTS ON INDUCTION-MOTORS FED BY QUASI RECTANGULAR CURRENT SOURCES

The analytical and experimental studies of the capacitor effects on the steep rising and failing voltage spikes and the current harmonics in induction motors fed by quasi rectangular current sources are conducted through the case of a motor fed with a six pulse current source. The phase current of the motor fed by the six-pulse current source goes through various regions of harmonic current (and voltage) variations. The analytical and experimental results show that as the value of the capacitor reactance is reduced gradually toward the motor magnetizing reactance, the motor encounters the higher frequency current amplifications first, and subsequently, the seventh-harmonic amplification and then the fifth-harmonic amplifications. Analytical result also shows that it is possible to encounter a severe fundamental-frequency current amplification when the capacitor reactance is less than the motor magnetizing reactance.