Analytical calculations show that during torque transients, the rotor deep bar effects can have a significant influence on the effective rotor time constant of an induction motor. This time constant is an important parameter for both direct and indirect field oriented (DFO and IFO) control. Whenever field orientation (FO) controller parameters differ from the real machine parameters, an incorrect calculation of the decoupling occurs, which can result in dynamic and / or static detuning. In the case of IFO, an incorrect estimation of the rotor time constant also leads to incorrect flux angle calculations with nonlinear torque control and limited stability as a consequence. In particular, the rotor deep bar phenomena result in a deterioration of the overall performance of the drive both dynamically and statically, thereby limiting the static stability region of the drive. In this paper, a rotor deep bar effect compensation circuit for field-oriented controllers is derived from the transient equations of a double-cage induction machine. Torque and flux are decoupled with respect to the airgap flux. Accurate tuning of the field-oriented controller is possible both for steady-state and high-frequency conditions in the rotor. Consequently, an extended static stability region and improved torque dynamics are obtained with the proposed deep bar effect compensated induction motor drive.
