Investigation of doubly fed twin stator induction motor as a variable speed drive

A doubly fed twin stator induction motor fed from two independent sources of different voltage and frequency is being evaluated as a variable speed drive. As part of the evaluation, experiments have been conducted on a pair of identical wound rotor induction motors. An analytical method to predict the steady-state performance of a doubly fed twin stator induction motor (DFTSIM) is described. The magnitudes, frequencies and the phase relation between the two stator applied voltages (referred to rotor) are assumed and the various currents, voltages, power terms and the torque output are computed. The analytical method aids in predetermining the conditions for stable synchronous operation of the DFTSIM. The study investigates the machine performance capability and the effect of control frequency and voltage/frequency ratio on the control winding power and volt ampere requirement. The predicted results are in good agreement with the experimental results confirming the validity of the proposed analytical method.