A METHODICAL APPROACH TO DETERMINE IMPORTANT THERMAL PARAMETERS OF A PERMANENT MAGNET ALTERNATOR

Abstract

This paper presents a thermal analysis methodology of a permanent magnet (PM) machine used in an aerospace application. Thermal uncertainties and important thermal parameters due to manufacture and assembly have been exploited by conducting several thermal tests in the machine pre-assembly stages. Steady state DC thermal tests of the stator windings at standstill are crucial to understand the main heat paths in the machine structure. Therefore, thermal data collected from the stator windings and laminations in steady state DC tests are used to calibrate the 3D finite element (FE) thermal model of the machine by employing lumped parameter thermal network (LPTN) and short time thermal transient tests for the windings. It is shown that the thermal experiments in pre-assembly and post-assembly stages are required to obtain a more accurate machine thermal model. Authors report that effective slot thermal conductivity is the principal thermal parameter which needs to be estimated correctly to model an electrical machine thermally and also that off-tooth winding of the machine causes a poor effective slot thermal conductivity. Sensitivity of important thermal parameters on the winding temperature variation is also described by utilising a calibrated 3D FE thermal model of the proposed alternator.