A Fast Identification Method for Rotor Flux Density Harmonics and Resulting Rotor Iron Losses of Inverter-Fed Induction Motors

Inverter-fed induction machines' iron loss characteristics become more complicated because of the harmonics brought by pulse width modulated (PWM) voltage-source power supplies. There are two main difficulties associated with analyzing the iron loss of induction motors, i.e., the identification of rotor flux density harmonics and the accurate prediction of iron loss. In order to reveal the iron loss characteristics of the inverter-fed induction motors, especially on the rotor side, a computationally efficient rotor flux density harmonics identification method using data from a single power supply fundamental frequency cycle (supply cycle) is proposed. With the proposed identification method, the rotor iron loss characteristics of a 5.5- and a 30-kW inverter-fed induction motors are investigated. By comparing the predicted and measured iron losses of those induction motors under both sinusoidal and PWM inverter voltage supplies, the effectiveness of the proposed method is validated. Furthermore, the detailed iron loss characteristics of the two induction machines under both sinusoidal and PWM inverter voltage supplies are studied.