Coupled-circuit-model simulation and airgap-field calculation of a dual-stator-winding induction machine

The computer-simulation model of the dual-stator-winding induction machine in which the space harmonics of the stator windings and those of the rotor circuits are accounted for has been presented. The winding-function method is used to calculate the inductances in the machine. The phase-voltage and torque equations thus obtained are further transformed to the rotor reference frame to facilitate simplicity of modelling and using an n x n complex-variable reference frame transformation. Simulation results of the no-load starting transient are presented with the response of the machine to a change in the load torque. The balance of the paper presents an approach, using the stator-winding and rotor-bar currents determined from the coupled-circuit model and the winding functions of the stator windings and the rotor loops, to generate the airgap flux density. A simplified correction scheme, using the B/H curve of the magnetic steel material to account for magnetic saturation in the airgap is introduced, improving the prediction accuracy. Some measurements of no-load and full-load flux densities confirm the computer simulation and FEA results.