Use of 3-dimensional finite elements for computation of temperature distribution in the Stator of an Induction Motor during Direct-On-Line Starting

Transient thermal analysis of induction machines is a subject of interest for machine designers in their effort to improve machine reliability. Since the stator is static, it is prone to overheating. Therefore, the study of transient thermal behavior in the stator is useful to identify causes of failure in induction machines. This paper presents a three-dimensional transient heat flow through the stator of an induction motor using arch shaped elements in the r--z plane of the cylindrical co-ordinate system. A temperature-time method is employed to evaluate the distribution of loss in various parts of the machine. Using these loss distributions as an input for finite-element analysis, more accurate temperature distributions can be obtained. The model is applied to one squirrel cage Totally Enclosed Fan Cooled (TEFC) machine of 7.5 kW. Finally, the temperatures obtained by this three-dimensional approximation at different locations of the stator were compared for different stator currents considering the time required for each stator current during the transient in Direct-On-Line starting.