Analytical Magnetic Field Distribution of Slotless Brushless Machines With Inset Permanent Magnets

An analytical open-circuit magnetic field distribution for slotless brushless machines with inset permanent magnets is presented. Three different magnetization patterns (radial, parallel, and Halbach) have been considered and their results compared with each other. The induced back-electromotive force (EMF) is also presented for each magnetization pattern. The effects of iron inter-pole on the magnetic flux density and back-EMF have been studied. To verify the model, the results have been compared with those obtained from finite element analyses (FEA).