Use of thermal network on determining the temperature distribution inside electric motors in steady state and dynamic conditions

This paper outlines a set of useful calculations and design guidelines for motor temperature rise prediction. Steady state analysis is presented, allowing a general view about the expected temperature rise in the stator winding. For transient conditions, starting and stall phenomena are modeled considering factors that are often neglected: the skin effect and the heat exchange from bars to the tooth. End ring temperature rise is assessed. Accurate temperature rise calculation is critical for several reasons: to control the peak temperature for hazardous locations, to predict the fatigue under the heating up and cooling down processes, to calculate the number of consecutive starts and to establish a safe stall time.