Study on Field-Regulating Characteristic of CPHES Machine

At present, most hybrid excitation machines (HEMs) use direct current to regulate the air-gap flux, which suppresses the field-weakening capability, and results in the range of field-weakening being inferior to that of field-strengthening. To solve this problem, this paper proposes an AC excitation structure (CPHES) and its control method. By changing the magnitude and phase of the AC field current, the strength of the air-gap magnetic field can be easily controlled, and the field-weakening capability can be extended to the same level as the field-strengthening. This paper analyzes the defects of DC excitation in traditional HEMs; and then introduces the structure, principle, and control method of CPHES machine. A 24 slot/8-pole prototype has been developed. The results show that the CPHES machine has symmetric bidirectional fleld-regulating capability, and the speed range of field-weakening for CPHES machine is twice that of traditional HEMs with DC excitation.