Finite element analysis and experimental test of an axial flux toroidal generator

This paper describes the development of finite-element models of axial flux toroidal generators. These machines are essentially synchronous generators with flux arising due to permanent magnet excitation and armature reaction currents. 3D magnetostatic FEA of these two cases has facilitated representation of the field MMF by excitation voltage E_f, and the armature reaction by synchronous reactance X_s. Two generators, rated at 20kW and 40kW, have been modelled and the results compared with those obtained from experimental work. The FEA results for Ef lie within 2% of the experimental results, and those for inductance lie within 7.5%. The analysis has then been extended to slotted stator machines. 2D dynamic models have been used to evaluate the excitation voltage and investigate the effects of incorporating rotor skew for the reduction of slot harmonics.