Characteristic Analysis for Concentrated Multiple-Layer Winding Machine With Optimum Turn Ratio

Three-phase fractional slot concentrated winding synchronous machines (FCSM) has excellent electrical properties of high torque density, low cogging torque, and torque ripple, yet in armature, as vibration/noise characteristics are not good due to asymmetric MMF, and due to the presence of subspace harmonics in MMF, eddy-current loss of permanent magnet is increased. If multiple-layer winding with optimum turn ratio is applied to three-phase FCSM, this can improve these problems. In this paper, the turn ratio in concentrated multiple-layer winding machine is proposed to be applied. Considering the turn ratio, a general formula is derived to calculate the winding factor. Using the induced formula, the winding factor changes according to the changes in the turn ratio are calculated, and the turn ratio to remove the harmonic components that the MMF has is determined. To verify improvement in the motor characteristics for the proposed method, turn ratio is applied to motors of 16 pole 18 slot and 10 pole 12 slot. For the two models, MMF distribution in the air gap using FEM is calculated, and through harmonic analysis, reduction or removal of a particular harmonic is verified. In addition, through FEM transient analysis, reduced eddy-current loss in permanent magnet is to be identified, and improvements in vibration/noise are to be verified by deformation/acoustic noise analysis of stator.