Torque per Ampere Enhancement of a Three-Phase Induction Motor by Means of a Capacitive Auxiliary Winding

This paper presents the use of a capacitive three-phase auxiliary winding to enhance the torque per ampere of a three-phase Squirrel Cage Induction Motor (SCIM) for electric traction, which generally requires high torque density, a high power factor and high efficiency. The three-phase auxiliary winding is only magnetically coupled to the stator's main winding. A conventional 5.5-kW, 50-Hz, and 4-pole three-phase SCIM is modified to accommodate the main and auxiliary windings in the stator slots. The electromagnetic conditions of the machine are studied by means of Finite Element Analysis (FEA). The results obtained from FEA are validated by means of practical results. The results from both FEA and experimental measurements evidence that the torque per ampere is tremendously enhanced when a capacitive excitation is applied to the auxiliary winding of the SCIM.