Feasibility Study and Harmonic Analysis of Fractional-Slot Distributed Winding in Brushless Doubly Fed Machines

Fractional-slot distributed winding (FSDW) is widely used in electrical machines due to its shorter end windings and greater design flexibility. This paper investigates the feasibility and impact of applying a FSDW configuration in a frame size D160 Brushless Doubly Fed Machine (BDFM). First, the feasibility of implementing the FSDW in the studied BDFM is evaluated through an analytical assessment of the direct magnetic coupling potential between the stator windings. The analytical results are then validated by the finite element (FE) model. Then, a comparative harmonic analysis is performed by simulating a 48-slot BDFM with integral-slot distributed windings (ISDWs) as the reference, using the same dimensions and rotor structure as the 36-slot BDFM. The FE simulation results for the 36 -slot BDFM with FSDW are further validated by experimental measurements. The results demonstrate that the FSDW configuration introduces no additional harmonics, and decreases total harmonic distortion (THD) by approximately 4 %.