Design limitations of reduced magnet material passive rotor transverse flux motors investigated using 3D finite element analysis

This paper presents an analysis of the design limitations of reduced magnet material passive rotor transverse flux motors with permanent magnets on the stator. The benefit of passive rotor designs is that the magnets are located on the fixed stator, which facilitates the use of active fluid cooling if necessary. The field and force solutions are obtained using three-dimensional finite element analysis for electromagnetic fields. Linear as well as saturation cases are investigated to establish design parameter dependencies and to determine minimum and maximum values for certain design parameters, such as the air gap flux density generated by the flux accumulator design of the magnets. It is shown that passive rotor designs achieve the same force densities as active rotor designs and design parameter recommendations are given that insure high force densities and low magnet material use.