Improving Induction Motor Efficiency with Die-cast Copper Rotor Cages

This paper examines some of the electromagnetic considerations for achieving near optimum efficiency of a hypothetical 10-Hp industrial motor with a copper rotor cage. The loss budgets for the motor with an aluminum cage and that for a substituted copper cage are calculated using a Matlab program. Rotor bar shape is then varied to improve "pull-up" torque and control starting current of the copper rotor machine. The performance of this modeled motor is then compared to the performance of recently introduced commercial high efficiency copper rotor machines and some of the design considerations used by the manufacturers to achieve the performance are discussed. Advances in the die casting process that have made the copper rotor motor cost effective are reviewed.