Influence of Different Direct Cooling Systems on 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.