Electromagnetic Analysis of High Speed Machines with Diametrically Magnetized Rotor for Flywheel Battery Applications

This paper investigates on the characteristics for the generation of electricity of high speed machine and derives analytical solutions for open-circuit field, armature reaction field and back-emf in terms of magnetic vector potential and a two dimensional (2-D) polar coordinate system. In particular, since the open-circuit field is essential for the prediction of a back emf, new magnetization modeling technique for diametrically magnetized rotor is presented. Finally, all analytical results are compared with those obtained from finite element (FE) analyses and, in particular, test results such as back-emf measurements are given to confirm the analysis.