Development of a Thermal Equivalent Circuit to Quantify the Effect of Thermal Paste on Heat Flow Through a Permanent Magnet Alternator

This paper describes the thermal modeling of a permanent magnet alternator (PMA). The principal focus is on, to investigate the effect of adding thermal paste into the machine end winding region. A thermal lumped parameter network is proposed to quantify the change in heat flow paths for a flange mounted alternator. The thermal model is implemented in Simulink, which allows many different heat paths to be easily combined. Since the addition of a thermal paste introduces new axial heat flow by conduction paths between the stator windings and frame, the developed thermal network considers the detailed heat flow paths in the PMA. The thermal network is extended to the machine frame and part of the mounting plate. It is shown that the axial heat flow has been improved by 5.6% for the PMA with the addition of the thermal paste. This in turn reduces winding temperature by around 10.5% at standstill dc tests. The model accuracy has been validated by performing finite-element analysis thermal simulations and experimental results.