Investigation of Starting Characteristics with respect to Starting-Bar Shape in a Double-Cage Induction Motor

This paper presents the new shape of a rotor bar improving the starting performances in a double-cage induction motor (IM). The rotor bar of a doble-cage IM is composed of a working bar, neck, and starting bar and each part has different effects on the characteristics of a motor. In this paper, it is confirmed that a starting bar has a dominant effect on the starting performances. The shape of a starting bar is designed by using the two ratios of the depth to width and the lower to upper width, respectively. The starting performances are closely analyzed by estimating the reactance and resistance of a rotor bar with respect to the depth through multi-layer method and FEA. Finally, by applying both the ratios to the starting bar, their mutual influence is scrutinized by using a response surface methodology and three models satisfying both starting torque and current aimed in this paper is proposed.