Foil Windings in Electric Machines

摘要

While the use of foil windings in transformers and air core inductors is not uncommon, their use in electric machines is just emerging. Although prototype realizations have been reported in the literature, a definitive analysis of their electromagnetic and thermal performance is necessary to evaluate their potential for broad applications. This research is devoted to presenting a comprehensive model for evaluating the thermal performance and AC loss characteristics of foil armature windings in realistic designs. An overview of foil armature windings is presented, highlighting the improved fill factor, AC loss characteristics, and heat transfer properties under steady-state operating conditions for a prototype round conductor coil and foil conductor coil. A lumped parameter thermal model that predicts the heat transfer behavior of the foil conductor coil is presented along with supporting experimental results. Next, a machine design procedure for a foil armature permanent magnet synchronous machine is presented and the prototype foil conductor machine is constructed. The machine is built to specifications and experimental results show strong agreement with analytical and simulation predictions. Experimental evaluation of the AC excitation losses, rotational losses, and thermal performance of the prototype machine provide valuable lessons to utilize foil armature windings to their best capabilities.