An approach to sizing high power density TFPM intended for hybrid bus electric propulsion

New developments in electric machine topologies have highlighted the possib ilities to make great improvements in propulsion applications. Of particula r interest are hybrid buses which are expected to be introduced in the near future with a large scale, in city transportation networks, in an attempt to reduce air pollution and noise. For such application, transverse flux pe rmanent magnet machine (TFPM)-based electric propulsion system is presently considered to be the most suitable design in so far as it exhibits the hig her power production potential. This paper presents a sizing approach of tw o major TFPM topologies intended for hybrid bus electric propulsion. At fir st glance, it is quite commonly believed that an optimal design. could be r eached through a 3D finite element analysis. Nevertheless, and given the la rge number of degrees of freedom in design, finite element analysis would t ake a very long computation time and would not necessarily lead to optimal solutions. It has been found that analytical developments combined with num erical optimizations represent an interesting approach which offers an effe ctive basis to TFPM sizing.