Field oriented control of a synchronous drive

Field oriented control (FOC) may be used for simple high-power synchronous drives, such as pumps and fans, to unify system with asynchronous drives. But distinction is strong influence of torque component of current on flux. Internal feedback in control object is investigated. This feedback becomes positive one in definite regimes. A simple addition in control is proposed, based on features of control object: component of reference for excitation current as function of torque reference and flux reference. Special parameters should be used for flux regulator. Positive results are confirmed by tests at virtual test bench of high-power AC drives.