Abstract: In order to solve the problem of high-amplitude low-order stator harmonics in magnetomotive force (MMF) of fractional-slot concentrated-winding (FSCW) permanent magnet (PM) machines, theoretical analysis of the FSCW-PM machines with star-delta (Y-△) hybrid connection in the winding was carried out in this paper. Firstly, a calculation method of stator MMF harmonics, which was suitable for arbitrary ratio of winding turns and differential mechanical angle, was derived. Furthermore, the method was extended from three-phase to m-phase FSCW-PM machines. Based on this method, the elimination principle of stator MMF harmonics by adopting the Y-△ hybrid connection was given, which could provide the principle to design the Y-△ hybrid connection windings to study how to use Y-△ hybrid connection in multi-layer winding structure to suppress the high-amplitude low-order stator MMF harmonics. Finally, four three-phase 12-slot/10-pole FSCW-PM machines with different winding layers and connections were established and calculated by the finite-element method. The result shows that the negative stator of Y-△ hybrid connection in multi-layer winding with given multilayer-winding turn ratio and offset angle can effectively decrease the high-amplitude low-order stator MMF harmonics, reduce core loss and permanent magnet eddy-current loss in FSCW-PM machines, which improves their performances.