Motors with Copper Rotors Can Cost Less to Produce (continued) But now there's good news A study conducted for the Copper Development Association Inc. (CDA) by Dr. Edwin Brush of BBF & Associates, Weston, Massachusetts, compared the actual cost of commercial-scale manufacture for EPAct/EFF-1-compliant general purpose motors with die-cast copper rotors with costs for "industry equivalent," mass-produced, aluminum-rotor motors with similar operating characteristics and efficiencies. Industry equivalent motors are composites constructed from information supplied to BBF & Associates by six major motor manufacturers. They were used in place of actual motors to protect the confidentiality of manufacturers' cost information, but participating manufacturers agreed that the composite motors described closely represent actual commercial-scale motor production costs. The result of the CDA/BBF study: The motors with copper rotors cost less to produce, by far! How much less? An average 18% (or $60) less for a 7.5-hp motor and 14% ($64) less for a 15-hp motor! The cost data are broken down in Table 1. The numbers speak for themselves, but the following information may be helpful when interpreting the data: The copper-rotor motors were specifically designed to optimize the use of copper and, at the same time, be equivalent to (i.e., able to compete with) commercial aluminum-rotor EPAct/EFF-1-compliant motors in terms of efficiency and performance. Designs optimized for the copper motors incorporated modifications of such elements as slot design and placement, the number of teeth, stack height, gap width, shaft and bearing characteristics, stator laminations and stator winding configurations, stator winding weight and frame size. We'll return to that last design element in a moment. "Efficiency" refers to electrical energy efficiency as measured according to IEEE Standard 112-B. "Performance" factors include horsepower, inrush current, starting torque and slip. The industry equivalent 15-hp motor has an electrical energy efficiency of 91.1%, which complies with the European EFF-1 standard and is slightly higher than the minimum EPAct minimum value (91.0%) listed in Table 12-11 of NEMA MG 1-1998 R3. That puts it within the range of efficiencies guaranteed for currently produced EPAct motors of this size. 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.