This paper compares two flux-weakening control methods used in the high-speed operation of a wound field synchronous motor (WFSM) and proposes a standard for the selection of an appropriate flux-weakening control method. WFSM is characterized by generating rotor flux by flowing current in the field windings. Therefore, there are two ways to control the flux-weakening of the WFSM. The first way is to inject a negative d-axis current, which is similar to other types of motors, and the second way is to use the inherent characteristic of WFSM, which reduces a field current. According to the design characteristics of WFSM, the two flux-weakening control methods show differences in the torque-speed curve at the high-speed region. In this paper, the comparison of two flux-weakening control methods for WFSM is suggested. In addition, a standard for selecting the appropriate flux-weakening control method is proposed. The validity of the proposed method is verified by experimental results.
