Comprehensive Analysis of Influencing Factors of AC Copper Loss for High-Speed Permanent Magnet Machine with Round Copper Wire Windings

Abstract

AC copper loss from stator winding is one of the main losses of the high-speed permanent magnet machines (HSPMMs) and directly affects the performance of the machines. AC copper losses are influenced by many factors, including the frequency, conductor diameter, temperature performance, etc. These factors cause the AC losses to increase significantly at high frequencies due to the skin effect and proximity effect. In this paper, a comprehensive analysis of the AC copper losses of HSPMMs with round copper wire windings is presented. Firstly, the structure and parameters of a 60 kW, 30,000 rpm high-speed permanent magnet machine are provided. Then, based on this parameter, a 2D-finite element model (2D-FEM) is established to obtain the AC copper loss. Through the eddy-current field analysis, the current density distribution of the stator winding and the variation trends of AC copper losses under different frequencies are observed. In addition, by comparing the winding current density distribution and the AC copper loss value under different conditions, the influencing factors of AC winding losses are comprehensively analyzed, including the frequency, conductor diameter, number of conductors per slot, notch height of the stator slot, and working temperature. Finally, four stator coil cases are manufactured, which have different conductor diameters and wire strands. The AC losses of the four cases at different frequencies are tested, and the theoretical results are verified by measuring the AC/DC loss ratios (kac) of different conductor cases at various frequencies.