Tests Show Mass-Produced Copper-Rotor Motors More Efficient Than Nameplate Claims Siemens’ “Above NEMA” Motors Are Also Cost-Competitive - We’ve known for some time that electric motors with die-cast copper rotors can exhibit efficiencies higher than comparable aluminum-cage models if both are designed specifically for that purpose. Basic physics — the I2R relationship — makes it self-evident. However, data from the Copper Development Association supporting that expectation were mostly derived from what are essentially hand-made test motors, of which no more than a few dozen examples in various sizes were constructed. In fact, a few of those motors actually were proved to be less efficient than expected, owing to certain process- or materials-related phenomena, as described in an earlier Update. Regular readers will recall that two factors, excessive oxygen content of the melt and inappropriate metallurgical condition of the lamination steel, proved to be particularly detrimental. It would therefore be reasonable to expect that other, yet-undiscovered devils might be hiding among the many exacting details attending overall motor design and manufacture. MORE >>

Update: Copper Motor Rotor is published monthly by the Copper Development Association Inc. to provide current information of interest to those in the electric motor and related industries. CDA assumes no responsibility or liability in connection with this publication and makes no warranties of any kind with respect to the information contained herein.