Impact of distorted voltage on three-phase induction motor performance

With ever increasing use of modern electric power applications, percentage of the electrical power flowing through non-linear loads increases. These non-linear loads inject harmonics and distort the current as well as the voltage. Distorted voltages have undesirable effects on the other loads, especially electrical motors, supplied from the point of common coupling (PCC). This article investigates the impact of supply voltage distortion on the performance of three-phase induction motor (IM). Under this operating condition, conventional equivalent circuit of IM is not appropriate. Therefore, a modified equivalent circuit is introduced considering the harmonics as well as the iron core losses of the motor. Steady-state and dynamic characteristics of the motor using MATLAB/SIMULINK software program are obtained. A laboratory prototype was built in order to check the computer simulation results. The experimental system consists of an PWM inverter, DSP (dSPACE-DS1104) and 1.5hp squirrel-cage induction motor. The simulation and experimental results are closely convergent and show that the induction motor under distorted voltage condition is subjected to current increase, high losses, overheating, insulation damage, low efficiency and torque/speed pulsations compared with sinusoidal voltage supply. Furthermore, derating factors for IMs with different harmonic distortion levels are introduced and compared with those of IEC60034-17 standard.