Field test of motor efficiency and load changes through air-gap torque

Although air-gap torque equations have been known for several decades, this is the first known paper suggesting the use of air-gap torque to measure efficiency and load changes of electric motors in the field. Very few assumed values are required, and the method is applicable for induction motors as well as brushless-DC adjustable-speed and synchronous motors. Theoretical foundation for this proposed method is presented. Experiments conducted on an adjustable-speed motor show the validity and potential of this approach.<>