Influence of different direct cooling systems on an interior permanent magnet traction machine performance

This paper investigates the impact of direct cooling systems on a 3-phase 12 slot/10 pole, 30kW interior permanent magnet machine for electric two-wheeler applications. Both in-slot oil cooling and shaft spray cooling models have been developed, allowing to compare with an air-cooling system in terms of continuous torque-speed envelopes and drive cycle efficiency. Multi-domain simulations have been carried out using Ansys Motor-CAD. It is found that the best continuous performance is obtained by shaft spray cooling and the in-slot oil cooling on its own is the least attractive. The combination of in-slot oil cooling and air cooling shows a significantly better performance than air cooling but the gain in the continuous torque may not justify the design and manufacturing complexity associated with it

Computationally efficient 3D analytical magnet loss prediction in surface mounted permanent magnet machines

This study proposes a computationally efficient analytical method, for accurate prediction of three-dimensional (3D) eddy current loss in the rotor magnets of surface mounted permanent magnet (SPM) machines considering slotting effect. Subdomain model incorporating stator tooth tips is employed to generate the information on radial and tangential time-derivatives of 2D magnetic field (eddy current sources) within the magnet. The distribution of the eddy current sources in 3D is established for the magnets by applying the eddy current boundary conditions and the Coulomb gauge imposed on the current vector potential. The 3D eddy current distributions in magnets are derived analytically by employing the method of variable separation and the total eddy current loss in the magnets are subsequently established. The method is validated by 3D time-stepped finite element analysis for 18-slot, 8-pole and 12-slot, 8-pole permanent magnet machines. The eddy current loss variations in the rotor magnets with axial and circumferential number of segmentations are studied. The reduction of magnet eddy current loss is investigated with respect to harmonic wavelength of the source components to suggest a suitable segmentation for the rotor magnets in SPM machines