A 3D-Airgap Slotless Permanent Magnet Machine for Transportation Applications

A novel 3D-airgap electric machine concept with multiple torque producing planes within the same structure is proposed to enhance the torque density of conventional machine topologies. The airgap of conventional machine topologies is limited to one fixed plane. The 3D-airgap configuration can be conceived in several different ways. In this research, one planar axial airgap and one cylindrical airgap is electromagnetically integrated into one 3D-airgap machine which increases mass utilization by integrating structural components into torque producing components. Moreover, the 3D-airgap concept maximizes the use of the end-winding section of the radial flux portion by converting it into a torque producing component. The 3D-airgap machine concept is validated through 3D-finite element analysis (FEA). It is found that the 3D-airgap concept can have more than double torque density compared to the 2D-airgap machine within the same active volume. It also helps to increase the torque per unit conductor loss; thus, it will have a better thermal performance for the same output torque. Resulting power density (kW/liter and kW/kg) also improves substantially. Additionally, a simulation method is proposed to predict 3D-airgap machines’ performances using the superposition principle. The proposed simulation method significantly reduces the computational time required for 3D-FEA.