Investigation on iron loss characteristics in star-connection and delta-connection under three phase PWM inverter excitation

An iron loss characteristic with three ring specimens connected in a star type and in a delta type on three phase inverter excitation is investigated. It is indicated that iron loss obtained from star-connection is about 14 % larger than that obtained from delta-connection. This difference is caused by potential of neutral point having the third harmonics on star-connection. Therefore, although the zero-phase current may flow, the drive of motor by delta-connection should be performed to reduce the iron loss. In star-connection, since a neutral point exists, a potential on neutral point sways by three phase inverter excitation. As a result, BH curve is expanded by this fluctuation.