High performance induction motor drive in field weakening region

Induction motor field weakening control which maximizes the power factor and output torque capability in steady state and transient condition is presented in this paper. By considering both voltage limit and current limit of the system, the optimal torque equation can be obtained in the field weakening region. Operating frequency is compared with the transition frequency to determine the region of field weakening operation. In conventional vector control of induction machine, losses are neglected. Ignoring iron losses in an induction motor model causes errors in the calculation of rotor flux, slip and torque and these errors result in performance deterioration. So, here induction motor model with an iron loss resistor is considered. Loss model of induction motor is referenced to rotor flux and this transformation results in no leakage inductance on rotor side. The effectiveness of the proposed speed control in field weakening region is verified through simulation in MATLAB/SIMULINK on a 750 W three phase induction motor. Simulation results indicate the effectiveness of performance improvement of the drive in field weakening region.