ABSTRACT
This chapter develops an equivalent thermal circuit with expressions for its parameters to calculate steady-state temperatures in a few points (nodes). It also develops on temperature variation in time (thermal transients) and on finite element modelling computation of temperatures in the machine with lumped thermal parameter estimation. Heat removal and the temperature distribution within the induction motor are the major objectives of thermal design. Finding the highest winding temperature spots is crucial to insulation (and machine) working life. In electric (induction) machines, the thermal energy flows from the windings in slots to laminated core teeth through the conductor insulation and slot line insulation. The convection heat transfer coefficient depends on the velocity of the fluid, fluid properties (viscosity, density, and thermal conductivity), the solid body geometry, and orientation. Intermittent operation with induction machines occurs both in line-start constant frequency and voltage and in variable speed drives (variable frequency and voltage).
