An Approach to Sizing High Power Density TFPM Intended for Hybrid Bus Electric Propulsion

New developments in electric machine topologies have highlighted the possibilities to make great improvements in propulsion applications. Of particular 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 permanent magnet machine (TFPM)-based electric propulsion system is presently considered to be the most suitable design in so far as it exhibits the higher power production potential. This paper presents a sizing approach of two major TFPM topologies intended for hybrid bus electric propulsion. At first glance, it is quite commonly believed that an optimal design could be reached through a 3D finite element analysis. Nevertheless, and given the large number of degrees of freedom in design, finite element analysis would take a very long computation time and would not necessarily lead to optimal solutions. It has been found that analytical developments combined with numerical optimizations represent an interesting approach which offers an effective basis to TFPM sizing.