FEM Analysis of the Inter-Bar Currents in Induction Motors Aimed at Estimating Contact Resistance

Abstract

The paper deals with the phenomena of the inter-bar currents in induction motors equipped with die-cast aluminum cage. The inter-bar currents cause additional stray losses, as well as increase the losses in the cage bars. The basic modeling element for a correct estimation of these currents is the knowledge of the contact resistance between the bars and the rotor laminations. By means of an extremely accurate and reliable 3D-FEM model of a 4-poles 15 kW induction motor, with closed rotor slots, the authors investigate the impact of a variable contact resistance on the inter-bar currents, rotor Joule losses, and the voltage drop along the bars. The obtained results are compared with those reported in other research works. The simulation results theoretically demonstrate that ad-hoc locked rotor tests can be suitably designed for developing a new non-destructive methods for the contact resistance measurement.