Optimum design and 3D finite element analysis of nonslotted and slotted internal rotor type axial flux PM disc machines

Axial flux internal rotor external stator surface mounted permanent magnet (AFIR) disc machines have simple structures, relatively high efficiencies and low cost. These machines can be used for the applications that require high power and torque density, high efficiency and low noise with the use of neodymium iron boron magnets. In this paper, sizing equations of the AFIR machines are derived using generalized sizing equations. Optimum machine design is illustrated by choosing the diameter ratio and the airgap flux density. Using the optimum design data, field analysis of the slotless and slotted AFIR machines are investigated. Pulsating torque analyses are carried out using a 3D finite element analysis (FEA) software. Minimization of cogging torque and ripple torque for both topologies is obtained using FEA utilizing the techniques such as modifying winding structure and skewing the rotor magnets. Finally the comparison of the two topologies in terms of torque quality is illustrated in the paper.