Efficiency Optimization Requires Improved Characterization of Polyphase Induction Motor Losses

For many years, industry standards, including IEEE Standard 112, have characterized the component losses of three-phase induction motors as primary and secondary conductor or (I2R) core, friction and windage, and stray load loss (SLL). The definition of each, as epitomized by IEEE 112, guarantees that part of the losses will be characterized as SLL. It also ensures that the secondary I2R loss will be underestimated and that the core loss associated with field distortions resulting from load current are not properly identified. This article provides the opportunity to further optimize motor efficiency by discussing issues with existing test-standard loss models and describing model methods that better characterize motor losses.