Design Process of a High Torque Density Direct Drive Involving a Transverse Flux Machine

This paper focuses on the design process of a direct drive motor which is to be installed within the wheel rim of a light electrical vehicle. The work starts with the set of requirements, considering space and mass restriction, torque capability and cycle efficiency. Next it is discussed in what manner the design goals are conflicting, alluding to the trade-off between high torque density and efficiency rating. Supposing low frequencies and a distinct space restriction, it is shown how this conflict is resolved in an optimal way, revealing a descriptive analytic expression. The result is used to govern the design process of a permanent magnet, transverse flux machine. Beginning with an analytic approach, the initial set of geometry parameters is further optimized by finite element analysis.