| In this dissertation novel magnetic circuit layouts of passive rotor transverse flux motors with a permanent magnet flux accumulator design on the stator are presented and investigated. The main advantage of these passive rotor designs is that the permanent magnets are fixed in place on the stator which reduces the mechanical stresses compared to the case of rotor mounted magnets. The fixed magnets allow higher rotational speeds. This design also is advantageous from the cooling perspective, because the magnets can dissipate their heat through the surrounding casing material. It also makes the magnets available for active fluid cooling in high power machines. Two novel passive rotor transverse flux motor designs are proposed and evaluated in this dissertation, that are referred to here as the slanted rotor design and the reduced magnet material design. The goal is to identify the passive rotor designs that have the least saturation problems, make economic use of the permanent magnet material and achieve high force densities. For the design that matches those criteria best, the reduced magnet material design, an analytical design methodology for the magnetic circuit is developed, that ensures a near optimal use of the magnet material by adjusting the operating point of the permanent magnets to their energy maximum. Using three-dimensional finite element analyses the preliminary optimum magnet use designs are then investigated to obtain relationships of the geometric design parameters providing the highest force densities. The results of the infinite element and analytical analyses of the reduced magnet material design recommendations are derived reflecting the geometrical, magnet material and saturation constraints of this design. By combining the design recommendations with the theoretical efficient magnet use design methodology, it is possible to find magnetic circuit layouts that meet both the criteria of minimum magnet use and high force density. |
