Capacitor effects on induction motors fed by quasi-rectangular current sources

Analytical and experimental studies of the capacitor effects on the steep rising and falling voltage spikes and the current harmonics in induction motors fed by quasi-rectangular current sources were conducted for 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 showed 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. The analytical results also show that it is possible to encounter a severe fundamental-frequency current amplification when the capacitor reactance is less than the motor magnetizing reactance