Investigation of Novel Axial Flux Magnetically Geared Machine

As axial flux permanent magnet (AFPM) machines are currently the most appropriate topologies for limited axial space applications, a novel axial flux magnetically geared permanent magnet (AFMGPM) machine is investigated in this thesis. Based on a yokeless and segmented YASA machine, a new AFMGPM topology was designed and studied. The proposed AFMGPM machine consists of stator segments equipped with concentrated windings and two PM rotors with different pole-pair numbers: a high speed rotor (HSR) and low speed rotor (LSR). The proposed AFMGPM offers the merit of simple mechanical structure and is suitable for applications with limited axial space.
Two possible rotor pole combinations were selected and designed with the same stator segments: MG12/5-7 with HSR pole pairs of 5 and LSR pole pairs of 7, and MG12/4-8 with HSR pole pairs of 4 and LSR pole pairs of 8. These were optimised for maximum torque capability. Performance comparisons at no-load and on-load conditions using 3D-finite element analysis (FEM) reveal that the machine torque performance is sensitive to the PM dimensions and better performance can be obtained with the MG12/5-7 topology.
It is demonstrated that the MG machines are a valid alternative to the conventional planetary gear function in HEVs. Combining the conventional PM machine with the MG machine has made it possible to replace the power split components using only one electrical device. Additionally, the proposed machine can work as a conventional magnetic gear (MG) and a generator. It is shown that the new AFMGPM machine can realise the function of power split devices in conventional HEVs, as a mechanical planetary gear, motor and generator. It is further shown that the rotor manufacturing tolerance has a significant effect in terms of stator/LSR misalignment on the no-load and on-load performances of the machine.
Finally, a performance comparison between the novel machine and the conventional axial flux YASA machine is performed. To validate the predicted results of finite element analysis, a prototype of the new topology and a conventional YASA machine are manufactured and tested. It has, showing that with the benefit of two rotors with different torques and speeds, the new AFMGPM machine has superior performance at all load conditions.