Maximum Torque Operation of Double Inverter fed Wound Rotor Induction Motor Drive in Airgap Flux Orientation

This paper presents a control strategy for the maximum torque operation of a double inverter fed wound rotor induction machine (DI-WRIM) in the airgap flux orientation. The torque optimization is achieved through a mathematical optimization strategy. This strategy provides the values of the reference variables for the drive operation, and these reference variables divide the constant torque region into two operating zones, namely, (OZ-I and OZ-II). The nature of change in the drive operation in these operating zones and further theoretical analysis is supported with plots and current trajectory in i
sd
– i
sq
plane. Moreover, i
sq
= –i
rq
in airgap flux orientation. To maintain this relation, a novel method of controlling i
rq
in the vector control scheme used for the voltage reference generation is discussed. The proposed control and the working of new i
rq
control are validated with adequate simulation and experimental results on two WRIMs that differ by turns ratio of the stator and the rotor windings.