The Numbers Are In: Important Financial Data Revealed (continued) Figure 1. Motor Efficiency: Copper vs. Aluminum Efficiency hp kW Poles Al Cu Difference Loss Reduction 4.0 3.0 4 83.2 86.4 3.2 19.0% 7.5 5.5 4 74.0 79.0 5.0 19.2% 10.0 7.5 4 85.0 86.5 1.5 10.0% 15.0 11.0 4 89.5 90.7 1.2 11.4% 25.0 19.0 4 90.9 92.5 1.6 17.6% 40.0 30.0 4 88.8 90.1 1.3 11.6% 120.0 90.0 2 91.4 92.8 1.4 16.3% 270.0 200.0 4 92.0 93.0 1.0 12.5% Average: 14.7% A Consistent Pattern Van Son attained his data from a variety of sources. Data were taken from the copper motor project's own trials but were also gathered from various manufacturers who replaced copper with aluminum in their own rotors. What emerged was a definitive pattern of improved efficiency over a wide range of motors. “From 3 kilowatts to 200 kilowatts, the consistency in the reduction of losses was within a predictable pattern. Theoretically, we looked at anywhere from 12-20% reduction in losses as the result of a rotor that is twice as conductive, or has half the resistance. And the pattern fits. Even though the range of efficiency here is not all that consistent, the difference is what is consistent, and it is predictable. You would expect to have loss reductions higher at the small sizes, and smaller at the large sizes, and that is the exact pattern we're seeing here,” he explained. (See Figure 1.) In one group of experiments, a number of variables were changed from rotor to rotor. And from those tests, once again, a predictable pattern emerged. “This was our chance to experiment with the consistency and the range of pressures and die casting variables, including quenching – air-cooled versus water – quenched,” Van Son explained. “What we found on this group of identical rotors was that the range was so tight on efficiency levels. The watts lost were an average of 157. The low was 153; the high was 167. These are extremely consistent results over a number of rotors.” In the same tests, stray load losses were reduced 23%. Van Son attributed that to the consistency of the performance of the copper rotors. “Theoretically, the conductivity of a rotor shouldn't have that much effect on stray load,” he explained. “But what we believe is, the consistency of these rotors - that is to say the reduction in porosity and the like – was able to reduce those stray load losses.” Additional Implications As different manufacturers have different needs, the implications of the data gathered from the copper motor rotor trials can be applied to several scenarios. “You can go for higher efficiency in the same stack, in order to have the highest efficiency out there,” he explained. “Another possibility is to keep same the efficiency and reduce the stack in order to offset the cost of the copper. Or, something in between. And that's really what we're seeing from those who have modified the rest of the motor design. They're trying to achieve a balance.” “No two manufacturers have the same motivations. They don't have the same markets. They don't have the same applications. And they don't have the same economics,” Van Son said. “But, what we've been able to learn from all these different manufacturers is that there are clearly possibilities by utilizing this technology as a competitive tool in the new marketplace.”

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.