Design studies and performance of HEFSM with various slot-pole combinations for HEV applications

Hybrid electric vehicles (HEVs) using combination of an internal combustion engine (ICE) and one or more electric motors are widely considered as the most promising solution for clean vehicles. One example of successfully developed electric machines for HEVs is interior permanent magnet synchronous motor (IPMSM), selected due to its smaller size and lighter weight providing with design freedom of the vehicles and its higher efficiency contributing to less fuel consumption. However, IPMSM design tends to be difficult due to all permanent magnets (PMs) are built in the rotor core. The mechanical strength relies mainly on thickness and number of bridges around PM but high number of bridges reduces the maximum torque due to increases in flux leakage. Therefore, a new candidate of hybrid excitation flux switching motor (HEFSM) with rugged rotor structure suitable for high-speed operation and with the ability to keep high torque and power density is proposed. Various combinations of slot-pole HEFSMs such as 6S-4P, 6S-5P, 6S-7P and 6S-8P are designed and analyzed. The performances of all designs are compared with IPMSM used in Lexus RX400h.