Thermal modeling of a permanent magnet machine built using Litz wire

Abstract

This paper considers thermal modeling of a 2 MW permanent magnet machine designed and manufactured for marine applications. The main focus is placed on the winding made of the Litz wire, and a practical approach to model heat transfer is presented. The proposed thermal modeling method, named segment-layer, is compared to traditional thermal models used mainly for standard winding configurations. In order to evaluate the accuracy of the developed thermal model, both simulation and experimental results are presented. In the simulation study, the proposed and traditional modeling methods are compared to a detailed finite element model of the Litz wire. Temperature measurements are carried out on the 2 MW machine prototype and a good agreement between the measurements and corresponding thermal model results is achieved. The suggested method is user-friendly and enables both analytical and numerical modeling of the Litz wire. Also, the parameters that play an important role in the winding heat transfer, e.g. impregnation goodness, can be easily implemented in the model developed in this paper.