Impact of iron loss on behavior of vector controlled induction machines

Vector control principles are derived under the assumption that iron core loss may be neglected. The paper discusses effects of this simplification on performance of vector controlled induction machines. Indirect stator, air gap and rotor flux oriented control of a current fed machine are dealt with, with the emphasis on indirect rotor flux oriented control. Models of vector controlled induction machines that account for the iron loss are derived, and the mechanism of core loss influence on behavior of the drives is highlighted. It is shown that detuning caused by neglecting the core loss will inevitably take place. The amount of detuning is investigated for steady-state operation, for all three types of vector control. Some insight into detuning during transient operation is provided for the case of indirect rotor flux oriented induction machine. The concluding part of the paper presents a new decoupling circuit for indirect rotor flux oriented control. The circuit accounts for iron loss and thus eliminates detuning which is otherwise present.