Overview of Hybrid Excited Machines for Electric Vehicles

This paper provides an overview of various hybrid excited machine topologies including: (1) both PM and DC coils in rotor; (2) PM in rotor and DC coils in stator based on conventional rotor PM machines; (3) both PM and DC coils in stator based on doubly salient, flux reversal, switched flux, stator slot PM machines; as well as (5) others based on Vernier machines, hybrid steppers, and claw-pole machines, etc. The series and parallel hybrid excitations are discussed and the advantages as well as drawbacks are analyzed. Moreover, the flux weakening control strategies for HEPMMs based on the utilization of flux weakening currents are highlighted by controlling (1) field excitation current only, (2) armature current only, (3) optimal field and armature current hybrid method. Finally, the potential of using HEPMMs to mitigate the overvoltage due to uncontrolled generator fault are described.