Assessing the Impacts of Rewind and Repeated Rewinds on Induction Motors: Is an Opportunity for Re-Designing the Machine Being Wasted?

This paper describes an extensive induction motor rewind study. The consequent effects during the rewind process on loss components and efficiency are investigated. All the tests are conducted in accordance with IEEE 112-B method and some results are justified by the calorimetric approach. The conclusions drawn from the study show little impact of rewinding or repeated rewinding on the motor losses and efficiency if "good practice" is followed strictly. Efficiency results presented for most rewind studies apply for the full load condition. Changes in the balance between fixed losses and load losses resulting from rewinding can however cause the maximum efficiency point to occur at a load, which differs from that of the original design. This may or may not be a disadvantage. Since few motors actually operate continuously at full load, comparisons of efficiency should really be made at the load point that applies specifically to the individual motor being rewound. The question that then arises is whether there is a chance of improving the energy efficiency by modifying the motor design during rewinding so that maximum efficiency occurs at the actual load point of the motor when used for its particular application