Thermal Analysis of a Three-Phase Induction Motor with Frame Design Considerations

The present work investigates the temperature distribution inside different parts of a three-phase induction motor when motor frame dimensions (fins thickness, fins height, fins spacing) were changed, and when frame material is changed from cast iron to cast aluminum. A 2.2 kW, 2 poles, insulation class F, totally enclosed fan cooled (TEFC), squirrel cage, three-phase induction motor is modeled according to its design documents and it is analyzed by a thermal network method (TNM) based on Motor-CAD software. The results show the motor temperatures are in direct proportional with fins thickness, fins spacing, and in inverse proportional with fins height. In addition, the motor temperature will decrease when using the cast aluminum frame. The results were verified by finite element method (FEM) results obtained based on Flux2D software with a good agreement. This work will help the induction motor designer in prediction the thermal state of induction motor when modifying the frame, without needing manufacturing and testing expensive prototype motor. (paper)