An investigation into the thermal modelling of induction motors.

Electric motors are the ubiquitous workhorses of the industry, working a in wide
range of conditions and applications. Modern motors, designed to exact ratings
using new materials improved manufacturing techniques, are now much smaller but
have higher loadings. They are being operated much nearer to the point of overload
then ever before. To ensure a satisfactory life span for the motor, temperature rise
must be limited to safe values. A lumped parameter thermal model has been developed,
which allows rapid and accurate estimation of the temperature distribution in
a machine. The lumped parameter thermal model depends on the accurate knowledge
of the thermal coefficients and more importantly the loss distribution. Hence
the temperature time technique was implemented to investigate the iron loss density
distribution. Experimental results are discussed and loss density information
throughout the volume of the machine was generated.
A novel method of determining the thermal coefficients employed in the heat flow
equation was investigated, using the thermal lumped parameter model of a machine.
Finally a 2-D finite element method was used to corroborate, or otherwise, the use
of the lumped thermal network model.