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. The steady-state analysis is presented, allowing a general view about the expected temperature rise in the stator winding. For transient conditions, the starting and stall phenomena are modeled considering the factors that are often neglected: the skin effect and the heat exchange from the bars to the tooth. The end ring temperature rise is assessed. The 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.

I. Introduction

Temperature rise is one of the key items to be considered while designing a machine. For steady-state conditions, the temperature of the insulation is important to be controlled in order to ensure that the winding life requirements are met. For the transient conditions, there is a very sharp increase in the temperature of the conductors, both on the squirrel cage and the stator windings.