Performance Analysis of PMSM for EV Application Considering Thermal Constraints

The impact of varying stator slot size on the efficiency and thermal capabilities of an electric vehicle’s permanent magnet synchronous machine is analysed and measured in this research. Finite element analysis was used to analyse an electromagnetic machine with four different sized slot areas, and a lumped parameter network model was used to evaluate a machine with four different sized slot areas thermally. The core losses are reduced due to the broader magnetic path when the slot size is reduced while the other dimensions remain constant, however the winding losses rise. Additionally, due to lower saturation, a greater maximum torque is achieved. The results are compared in the torque-speed operating area of the machine in terms of machine-part and total losses, continuous torque and transient overload capabilities, and energy losses and peak winding temperature during 19 low, middle, and high-speed drive cycles. The biggest slot had the lowest winding losses and, as a result, the most thermally constrained torque capacity. Due to its lower component load (i.e. core) losses, the energy losses with the biggest slot were the highest in 13 of the drive cycles and the lowest in 11 of them with the smallest slot. Because it has the least copper, the smallest slot would also have the lowest material cost.