Performance Analysis of Induction Motor with Variable Air-Gaps using Finite Element Method

Abstract

In this study, three models of induction motor (IM) were used to examine the effect of different air-gaps (0.3 mm, 0.5 mm, and 1.0 mm) which have the same electrical features. One of these is the standard 3-phase, 1.5 kW, wye connected motor and the others are modified motors which have different diameters. The torque, efficiency and ripple values of each model were calculated using Finite Element. It was observed that the model with 1.0 mm has lower efficiency of 88.4% compared with the other efficiencies of 94% and 92%. Also, lower power factor values of 0.92 and 0.95 were obtained at 0.7 mm and 1.0 mm gaps respectively while highest power factor of 0.97 were obtained at 0.3 mm gap at the same speed of 1360 rpm.  Furthermore, it was observed that increase in the gap increases the magnetizing current produced in the gap from 3 A to 4.36 A at rated conditions. Besides, losses were increased from 73.7 W to 91.4 W while the torque ripples increased from 4.15% to 4.74%. Considering the reliability and efficiency of the motor, the prime value of the air-gap thickness should be between 0.3 – 0.5 mm for the studied motor. Hence, there is need for the designer of induction motor to maintain the minimum air-gap length in order to improve the power factor and to reduce the no-load losses in the motor.