EMF waveform optimization using the permanent magnet volume-integration method

The emf expression can be derived with the PM volume-integration method, allowing easier optimization and prediction of the emf harmonic content. An analytical expression is developed for predicting the electromotive force (emf) waveforms and flux linkage resulting from the motion of permanent magnets (PM) in the case of two cylinders, where the outer cylinder carries a surface-mounted winding and the inner cylinder carries the PMs. The expressions are based on the PM Volume-Integration Method, which uses a volume integral calculated over the magnet volume, rather than the usual surface integral over the coil surface. The specific case of surface-mounted arc PM with radial magnetization is analyzed. An outer cylinder with infinitely thin winding distribution on its inner surface is considered. The chording factor, slot factor and spread factor are included in the analytical expression. The emf waveform and related harmonics are predicted analytically and validated by comparing with a finite element analysis and with experiment.