DE-13-011 -- Estimation of Induction Motor Circuit Parameters and Efficiency Under Variable Frequencies PDF

Theoretically, motor efficiency is impacted by motor loadas well as frequency. The motor equivalent circuit methodprovides an effective method to estimate motor efficiency.However, the circuit parameters normally have to be determinedthrough field tests, which are impossible to conductwhen systems are in service. Based on the fact that measuredmotor efficiency and power factor data at four load levelsunder the rated frequency are always published, an iterativemethod is proposed to identify the circuit parameters usingpublished data. The circuit parameters are used to estimate themotor efficiency under different frequencies. In this paper, themathematical relations between motor efficiency and powerfactordata and the circuit parameters are first formularized,then the least-squares method is utilized to identify the circuitparameters using the published data under the ratedfrequency, and finally the motor efficiency is estimated underdifferent frequencies.