Control strategy of a variable flux machine using AlNiCo permanent magnets

This paper is concerned with the development of a vector controller for a variable flux inset permanent magnet synchronous machine (VF-IPMSM). This variable flux machine (VFM) uses low cost aluminum-nickel-cobalt (AlNiCo) permanent magnets (PMs). The demagnetization of the permanent magnets (PMs) is conducted on the stator winding of the machine hence there is no separate winding for the excitation of the PMs. The proposed control method incorporates field weakening for smooth transitions between torque and speed from a higher magnetization state to a lower one. The benefits of the variable flux over a normal insert permanent magnet synchronous machine during field weakening operation are demonstrated. Due to the use of AlNiCo PMs the size of the converter is reduced and hence converter costs reduction.