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

In this paper, an analytical and experimental study on the tolerance to supply voltage unbalance of three-phase squirrel-cage induction motors with different dual-winding configurations, is presented, with focus on the phase current unbalance rate, the maximum amplitude of phase currents, and the per-slot stator Joule losses. Fifteen different dual-winding configurations were tested in an induction motor with reconfigurable windings, at no-load condition. The dual-winding configurations tested include the star-series, star-parallel, delta-series, delta-parallel, and star-delta connection modes, with different angular displacements between the dual windings, namely, 0, 20, 40, 120, and 300 electrical degrees. The two configurations leading to the lowest phase current unbalance rate and per-slot Joule losses under voltage unbalance, at no-load, were identified, which, in relation to the commonly used delta-connected single windings, may provide more motor tolerance to supply voltage unbalance, ultimately extending the useful lifetime of the stator winding.