Some commentary on the choice of rotor bar material for induction motors

Almost any metal can be used in the design of the squirrel cage of an induction machine. Obviously lead is not used because of its low melting point and magnesium because of its low flash point. Others are rejected because of the cost, lack of strength, resistance, thermal conductivity, or manufacturability including ease of joining. Basically, the choice fails to two materials, aluminum and copper and their alloys. For lowest cost of manufacture, especially for mass production, aluminum surpasses copper. In order to determine which of the two materials is the best takes the combined skills of an electrical, a mechanical and a metallurgical engineer. This paper discusses some of the considerations in the choice of rotor bar material