Improvement of the Continuous Performance of a Traction Machine for a Battery Electric Vehicle through Magnet Segmentation

This work investigates the impact of the magnet segmentation on the continuous performance of an interior permanent magnet synchronous machine of a battery electric vehicle. Electromagnetic and thermal simulations, as well as thermal laboratory experiments are performed for the solid magnet reference design and the segmented magnet variant, and the results are compared, in order to verify the impact of the alteration. The rotor geometry is kept constant, therefore the magnet area is decreased by 1.25% for the segmented design, in order to account for the insulation layer between the segments. This results in a slight decrease in the maximum power and torque values of the segmented designs, throughout the operating range. Finite element analysis results of the designs state that the copper and core losses show only marginal differences between the designs, however the magnet losses are improved 5-7 times after segmentation. Furthermore, the continuous performance is improved for high speeds, at 12000 rpm, the continuous power increases from 46 kW to 65 kW and the continuous torque similarly increases from 39 Nm to 55 Nm. The thermal experiments show that the machine losses at high speeds are lower for the segmented design. Moreover, the rotor temperature of the segmented design is lower than of its solid magnet counterpart.