On the Pole Pair Selection of Synchronous Reluctance Machines for Traction Applications

This paper presents a design methodology for synchronous reluctance (SyR) machines aimed for traction applications considering the usually neglected electromagnetic and mechanical phenomena, namely cross-coupling and structural ribs effect, slot leakage flux and iron losses. Being the bottleneck of analytical methods, accuracy is improved by conducting a limited number of finite element analysis (FEA) and calibrating the initial model. This semi-analytical model is then used to design SyR machines with different number of poles and rated speeds. Maximum speed operation is also considered, reflected through adjusted mechanical ribs dimensions. Torque and power factor of the machines providing the maximum torque with increasing number of poles and maximum speeds are presented and investigated. Results reveal that the optimal pole number from a torque perspective depends on the considered speed. The reasons behind this behaviour is fully investigated as well as how and why the optimal geometry change when considering different number of poles and maximum speeds.