Investigating characteristics of a concentrated-winding interior permanent magnet synchronous machine for sensorless direct torque control

This paper investigates characteristics of a fractional-slot, concentrated-winding (FSCW) Interior Permanent Magnet Synchronous Machines (IPMSM) under sensorless Direct Torque Control (DTC). The FSCW IPMSM is being developed vigorously in recent years because of its high-power density, high efficiency, wide field-weakening capability, and high fault tolerance compared to the distributed-wound IPMSMs. The major disadvantage of concentrated winding is often cited to be its non-sinusoidal stator MMF. However, using appropriate combination of slots and poles, nearly sinusoidal EMF and very low cogging torque can be achieved. Although steady-state performance such as efficiency and constant power speed range of this type of PM machines have recently been published, dynamic performances have yet not been reported. The sensorless DTC schemes, which rely on the machine model, were applied to a prototype a 14-pole/ 18-slot, double layer concentrated-wound IPM machine. The model for distributed wound IPMSM was used for the control. This paper investigates the appropriate stationary reference frame of the FSCW IPMSM motors which should be appropriately shifted because of the harmonic and sub-harmonic components in the stator mmf of the concentrated winding machine compared with the distributed windings (DW) machine. The experimental results on the concentrated winding IPM machine confirmed the effectiveness of the proposed adjustment of the stationary reference frame according to the investigation of the difference between concentrated and distributed windings of an IPMSM.