Maximum torque control of stator-flux-oriented induction machine drive in the field-weakening region

In a conventional stator-flux-oriented (SFO) induction machine drive system, the field-weakening method is used to vary the stator-flux reference in proportion to the inverse of the rotor speed. This paper investigates why the maximum torque capability cannot be obtained in a conventional SFO system. This paper proposes a new selection method of flux reference to obtain maximum torque capability in the field-weakening region by considering voltage, torque, and current limits. The proposed method is verified by simulation and experiment with a 5 hp induction motor drive.