Ieee Transaction on Industrial Electronics

This paper presents a comprehensive analysis and comparison of air-cored axial flux permanent magnet (AFPM) machines with different types of coil configurations. Although coil factor is particularly more sensitive to coil band width and coil pitch in air-cored machines than conventional slotted machines, remarkably no comprehensive analytical equations exist. Here new formulae are derived to compare the coil factor of two common concentrated-coil stator winding types. Then respective coil factors for the winding types are used to determine the torque characteristics, and from that the optimized coil configurations. Three -dimensional (3D) FEA models are built to verify the analytical models. Furthermore, overlapping and wave windings are investigated and compared with the concentrated-coil types. Finally, a prototype machine is designed and built for experimental validations. The results show that the concentrated-coil type with constant coil-pitch is superior to all other coil types under study.