Voltage Pulsation Induced in DC Field Winding of Different Hybrid Excitation Switched Flux Machines

Voltage pulsation induced in dc field winding of hybrid excitation machines can cause current ripple in dc field winding and may even lead to unstable field excitation. Moreover, it may also impair the torque performance and complicate the drive, especially at high speed. In this article, the voltage pulsation induced in the dc field winding of different hybrid excitation switched flux machines (HESFMs) under both open-circuit and on-load conditions are comparatively studied. It shows that the HESFM topologies significantly affect the dc field winding induced voltage pulsations. To further suppress the induced voltage in field winding, three suppression methods, i.e., rotor step skewing, rotor pole notching, and rotor pole shaping are proposed and compared. It reveals that rotor step skewing has the best suppression performance. Finally, a prototype HESFM with both nonskewed and 2-step skewed rotors are fabricated and tested to confirm the finite element analyses.