Software aided derating and performance prediction of cage-rotor induction motors under distorted supply conditions

This paper reports on the development of a software for determination of thermal conditions of the winding and at the middle of the stator cross-section based on a novel hybrid thermal model and performance prediction using equivalent circuit parameters at fundamental and harmonic voltages of three-phase cage-rotor induction motors when operated at distorted waveforms of the supply system. Static power converters and non-linear loads used by industries for various purposes change the sinusoidal nature of the system voltages, resulting in injection of harmonic voltages in the power system and when three phase cage-rotor induction motors are connected to this power system, the performances of the motors will not be satisfactory. Due to harmonic currents, the total losses in the motor will be more resulting in higher temperature rise of the motor which may not be allowed due to faster deterioration of the properties of the insulating materials thereby reducing the life expectancy of the motor.