Die-Cast Copper Motor Rotors: Motor Test Results, Copper Compared to Aluminum
Motor manufacturers have long realized that because the electrical conductivity of copper is nearly 60% higher than that of aluminum, substituting copper for aluminum in the squirrel cage of the induction motor would markedly increase the electrical energy efficiency of the machine. Most motors larger than about 200 kW and a few special purpose smaller motors are built with copper squirrel cage structures manufactured by a time consuming and costly fabrication process. The intricate squirrel cage of smaller motors is produced by pressure die casting aluminum. Alternative cost-effective manufacturing methods have not been devised. A major barrier to adoption of copper for the rotor has been the high cost resulting from the short die life of the ordinary die steels experienced in die casting copper with its high melting temperature (1083°C compared to 660°C for aluminum).
Copper motor rotors: Energy saving efficiency, now also economic feasibility
Replacing aluminum with copper in the die cast squirrel cage conductor bars in electric induction motor rotors has enormous potential benefit in terms of improved efficiency, energy savings, reduced maintenance and reduced weight and cost. Energy savings in the US alone can eventually exceed the output of three to four new 600 megawatt generating plants. The major deterrent to that conversion has been the short tool life associated with casting molten copper. Research sponsored by the Copper Development Association has identified recommended tool materials and casting practices that significantly improve tool life. THT Presses, Inc. has developed a vertical die casting machine with design features especially suitable for casting motor rotors, and have demonstrated capability to cast a wide range of copper motor sizes on that equipment. They now cast copper-alloy motor rotors for customer evaluation and for limited-volume production runs. THT's Sub Liquidus rheocasting process provides future opportunity for even better tool life when die casting copper alloys.
Energy-Efficient Electric Motors Selection and Application
Induction motor characteristics energy-efficient motors electric power costs the power factor application of electric motors induction motors and adjustable-speed drive systems economics of energy-efficient motors and systems.