Profiling the Eddy Current Losses Variations of High-Speed Permanent Magnet Machines in Plug-In Hybrid Electric Vehicles

Abstract

High-speed permanent magnet (PM) machines have been recognized as a popular choice for plug-in hybrid electric vehicles (PHEVs). Although high-speed operation can enhance the machine power density, more rotor eddy current losses can be expected. Those losses dominantly result from the current harmonics that may vary during the vehicle driving cycles. Therefore, it is crucial to profile the eddy current losses variations, thus identifying the worst case. To achieve this objective, a new indicator, namely the frequency-weighted harmonics distortion (FWTH), is defined correlating with eddy current losses in this article. Profiling eddy current losses variations by FWTH relieves the computational burden seen in the finite element analysis (FEA) as its derivation simply governs all the current harmonics. Various machine and converter operation conditions are covered in the study. The strong correlations between the addressed FWTH factor and the eddy current losses have been validated from the FEA, and then the experimental results on a 110-krpm, 35-kW PM machine served in PHEVs. The effectiveness of using FWTH to profile the eddy current losses variations during driving cycles has been proven, where the worst eddy current case has been identified for the tested machine.