FEA Characterization of Bi-Axial Excitation Machine for Automotive Traction Applications

Bi-axial excitation generator for automobiles (BEGA) machines are ideally suitable for unity power factor at the base speed which would give the best power density and lowest cost for a traction-motor inverter system. In this paper, three different designs of bi-axial excitation motors are presented: One employing rare-earth free ferrite magnets and two employing NdFeB magnets. The permanent magnets are oriented along the q-axis and are used to compensate the stator flux in order to achieve higher power factor. This reduces the required inverter size thus bringing down the overall system cost. The flux compensation is analyzed using 2D FEA and the motor performances are compared to other commonly used traction motor topologies.