Comparative study of detuning effects in indirect rotor flux oriented induction machines due to iron core losses

Recent research indicates that iron loss, although usually neglected, may play an important role in establishing accurate rotor flux oriented control in induction machines. As all the vector controlled induction machines are fed from PWM voltage source inverters, which cause significant increase in total iron losses compared with an ideal sinusoidal supply, it is essential to first establish which part of the iron loss will lead to detuned operation. The aim of this paper is to present experimentally measured iron losses in a set of four induction machines fed from a PWM inverter and to quantify detuning effects in vector controlled induction machines utilising these experimental results. Theoretical investigation of detuned operation, caused by omission of iron loss representation in the control system, is elaborated for the case of an indirect rotor flux oriented induction machine, for all the four induction machines. Results show that the amount of detuning is significant in machines where iron loss with sinusoidal supply is a relatively high percentage of the output power