Analytical thermal models for small induction motors

Purpose - Thermal analysis is an important design aspect and becoming a more important component of the electric motor design process due to the push for reduced weights and costs and increased efficiency. The purpose of this paper is to demonstrate that the accuracy of analytical thermal models depends on the accuracy of the thermal resistance computation and on the number of nodes in the equivalent thermal circuit. Design/methodology/approach - In this paper, several thermal analytical models with different numbers of nodes are compared against with each other and with experimental data. Findings - It is demonstrated that the more sophisticated and detailed model having a larger number of nodes can be used to calibrate the simpler but faster models with less nodes. The models are all for the same range of small totally enclosed non-ventilated induction motors. Originality/value - This paper shows that simplified and/or detailed analytical thermal models can be successfully used in predicting the temperature rise in small induction motors. The level of detail and accuracy of these models strongly depends on the number of nodes and how the thermal resistances are set up. The calibration process for various reduced nodal model has been successfully described. Once calibrated, the reduced node thermal models give both satisfactory accuracy and allow very fast and robust thermal calculations.