Reduced losses in die-cast machines with insulated rotors

This paper reports an investigation into the influence of inter-bar currents on the performance of die-cast cage induction machines. The work is based on an extensive set of experimental measurements using a series of specially made die-cast cage induction motors with bars insulated using alternate processes. The observations arising from the test results are reinforced by predictions made using an analytical model. The work in this study shows that increasing the insulation of the rotor cage will reduce loss and thereby improve the efficiency. This premise is demonstrated both experimentally and analytically. The efficiency gain can be attributed to the inhibition of the flow of inter-bar currents.