The preliminary results on Direct Torque Control for an fractional-slot concentrated winding Interior Permanent Magnet Synchronous Machine

This paper reports results of investigation of the Direct Torque Control (DTC) technique to an fractional-slot Interior Permanent Magnet Synchronous Machine (IPMSM) with concentrated windings (CW). Application of concentrated winding to IPM machine is gaining attention from research community because of its advantages such as high-power density, high efficiency, short end-turns, wider flux-weakening capability, fault tolerance, robust rotor, and presence of additional reluctance torque component, and, the major disadvantage is of non-sinusoidal magnetomotive force (MMF). However, using appropriate combination of slot and pole, sinusoidal EMF and low cogging torque can be achieved despite presence of MMF harmonics. A 14-pole, 18-slot, double layer concentrated winding IPM had been designed and constructed at the University of the New South Wales. The DTC was applied to the prototype machine. In DTC scheme, the requirement of the continuous rotor position sensor and coordinate transformation between stationary and rotating (dq) reference frame is eliminated since all of the calculation is done in stator reference frame. The speed is estimated from the stator flux linkage vectors and the torque angle. The performances of the DTC control scheme is evaluated in terms of torque and current ripple, transient response to step variations of the speed command and load disturbances at maximum torque per ampere and field weakening regions. The experiment results presented clearly demonstrate effectiveness of DTC in IPMSM with CW.