Comprehensive Analysis of Alternative Magnet Configurations in a Biased-Flux Machine

Biased-flux motors are a type of electric machine that operate in an unconventional manner but can offer structural and performance advantages over more conventional topologies. Achieving a suitable design in this relatively uncommon topology requires identifying the effect of various factors on its performance. Even small changes in the structure and magnet configuration can have a significant impact on performance. In this paper, the magnet configuration, flux barriers and bridges are investigated to try and improve the performance of a baseline biased-flux motor. The details of the structure and operating principles are explained, and structures are optimised for torque production in a fixed volume. The no-load and full-load operations of alternative variants are studied in terms of cogging torque, flux density, flux line, torque profiles and overload capability. Moreover, a complete comparison has been made between split-magnet and single-magnet topologies in an intermodular permanent magnet motor. The magnetic stresses on the PMs are studied to assess the demagnetisation risks. It has been explained how splitting the magnets and introducing flux barriers increase the torque density and flux bridges decrease the demagnetisation risk. To better analyse the PM demagnetisation, a thermal study is carried out, and the PMs' B-H curve is modified accordingly. A comparative study is also conducted with other stator-permanent magnet motors to better assess the demagnetisation behaviour of the proposed topologies.