Assessment of Induction Motor Tolerance to Supply Voltage Unbalance for Different Dual-Winding Configurations

In this paper, an assessment of three-phase squirrel-cage induction motor tolerance to supply voltage unbalance for different dual-winding configurations, focusing on the phase current unbalance rate, the maximum amplitude of phase currents, and the per-slot stator conduction losses, is presented, including theoretical deductions, simulations, and experiments. Fifteen different dual-winding configurations were tested in an induction motor with externally reconfigurable windings at different load and slip conditions under supply voltage unbalance resulting from lowering the amplitude of one line-to-neutral voltage. The dual-winding configurations experimentally tested included the star-series, delta-series, and star-delta connection modes, with different angular displacements between the two partial windings, namely, 0, 20, 40, 60, and 240 electrical degrees. The experiments that were conducted allowed for obtaining novel results and conclusions, including identifying the three dual-winding configurations that lead to the lowest per-slot per-unit conduction losses under the considered type of supply voltage unbalance. Compared to the commonly used delta-connected windings, the identified dual-winding configurations may provide more motor tolerance to supply voltage unbalance, ultimately extending the useful lifetime of the stator windings.