Magnetic flux analysis of a new e-core HEFSM with various slot-pole combinations for HEV

The significant growth of today's cities has led to increased use of transportation, which brings about aggravated urban pollution and other serious environmental issues such as the greenhouse effect that culminates in global warming. Gases produced by vehicles should be strictly controlled and proactive measures must be taken to minimize these deleterious emissions. To face this challenge, private automakers have introduced such HEVs that reduce the use of combustion engines by integrating them with electric motors. IPMSM is an example of successfully developed electric motor for HEV which utilizes rare-earth PM commonly employed to increase their power density. Despite its good performances and being well operated, IPMSM has some drawbacks of (i) three-phase armature windings are wound in the form of distributed windings, resulting in high copper loss and large coil end length, (ii) mechanical stress of rotor depends on substantial number of PM bridges, which causes considerable flux leakage between PMs, (iii) complex shape and structure renders design optimization difficult, and (iv) constant flux from PM is hard to control, especially at light-load and high-speed operating points. To address these weaknesses, a new E-Core HEFSM built from concentrated armature windings, robust rotor structure, much simpler shape, and controllable PM flux via DC-FEC is introduced to serve as an alternative candidate for HEV drive system . Although, the proposed E-Core HEFSM exploits primary excitation by PM as well as DC-FEC as secondary source, the underlying purpose of using two excitation field sources is to combine the advantages of PM-excited and DC-FEC synchronous machine . Importantly, DC-FEC controls excitation flux in the air gap, which strengthens flux weakening capability . In effect, hybrid excitation by manipulating excitation flux enables designing a machine with relatively low armature magnetic reaction while extending the speed operation range as well as improving efficiency in the most frequent operating zones of the traction motor . In this paper, performances of 6S-4P, 6S-5P, 6S-7P, and 6S-8P E-Core HEFSMs encompassing magnetic flux linkage, induced-voltage, cogging torque, magnetic flux enhancing, torque and power characteristics are discussed .