Estimation of Equivalent Thermal Conductivity for Impregnated Electrical Windings Formed from Profiled Rectangular Conductors

Abstract

In order to improve accuracy and reduce model setting-up and solving time in thermal analysis of electrical machines, transformers and wound passive components, the multimaterial winding region is frequently homogenised. The existing winding homogenization techniques are predominantly focused on winding constructions with round conductors, where thermal conductivity across conductors is usually assumed to be isotropic. However, for the profiled rectangular conductors that assumption is no longer valid, and anisotropy of the winding equivalent thermal conductivity needs to be considered. This paper presents analytical methods for deriving equivalent thermal properties of impregnated windings with profiled rectangular conductors. The techniques allow for computationally efficient and accurate derivation of the composite thermal conductivity accounting for the material thermal anisotropy. Efficacy of the methods has been demonstrated on a number of hardware winding samples commonly used in low-voltage applications. The theoretical analysis has been supplemented with experimentally derived data showing close correlation.