Die Casting Copper Motor Rotors

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Die Casting Copper Technique Improves Energy Efficiency of Electric Motors

Though it conducts electricity less efficiently than copper, aluminum is the industry’s preferred fabrication material in electric induction motor rotors. Traditional tool steel casting molds suffer thermal shock, shortening mold life and increasing operating costs when used for die casting copper rotors. ThermoTrex Corporation, with the assistance of a NICE3 grant, proposed a process for copper die casting using molds from high-temperature, thermal shock-resistant materials. The copper industry successfully tested these mold materials for copper die casting at higher temperatures (copper melts at 1083°C, aluminum at 660°C).

The copper die-casting technology developed by the copper industry is now in commercial use. The process replaces the tool steel molds used for the aluminum die casting with molds made from high-temperature die materials. In addition, the new process preheats the die inserts, reduces the temperature differential between the mold surface and the cooler interior, and avoids mold failure from thermal shock and thermal fatigue.

In 2003, SEW Eurodrive of Bruchsal, Germany, was the first company, worldwide, to bring the technology to market. A line of high-efficiency gear motors (1.1-5.5 kW) use copper rotors at a competitive price. Although traditional high-efficiency motors are larger than standard motors, gear boxes using copper rotor technology provide efficiency without increasing motor size. In 2004, FAVI S.A., a major French supplier of copper and copper alloy die castings, began offering custom-designed, copper-based rotors for squirrel-cage electric motors in sizes ranging from fractional to 100 hp. Siemens Corporation began commercial production and sales domestically in 2006 in the 1 to 20 hp range.

Squirrel-Cage Motor with Die Cast Copper Rotors

Impact of Commercialized Technology
  2003 2004 2005 2006 2007 2008 2009 2010 2011
Energy Savings (Trillion Btu) 0.003 0.007 0.012 0.029 0.062 0.125 0.152 0.163 0.168
Emissions Reductions
(Thousand Tons)
Carbon 0.054 0.134 0.242 0.567 1.211 2.451 2.987 3.202 3.309
NOx 0.000 0.001 0.002 0.005 0.010 0.020 0.024 0.026 0.027
SOx 0.001 0.001 0.003 0.006 0.013 0.027 0.033 0.035 0.036
Particulates 0.000 0.000 0.000 0.000 0.000 0.001 0.001 0.001 0.001



  • Invented by the ThermoTrex Corporation and commercialized by the Copper Development Association Inc.
  • Marketed by SEW Eurodrive, FAVI S.A, and Siemens Corp. with more than 300,000 in use in the U.S. in 2011.


Can be used in electric motors throughout U.S. industry, which account for more than 60% of all electricity use in the nation.



  • Reduces electric motor total energy loss by 15% to 20%.
  • Decreases operating costs compared with conventional motors.



Reduces production time and hand labor compared with former methods of producing copper motor rotors.



Decreases operating costs compared with conventional motors.


Contact Information

Ned Brush
(781) 891-6909
Copper Development Association Inc.