MAGNETIC-FIELD ANALYSIS OF ASYMMETRICAL MACHINES BY FINITE-ELEMENT METHOD

Magnetic and electric asymmetry have been used by many electrical mach ine designers to develop useful devices. The main feature of such desi gns is the nonsinusoidal variation of the magnetic field with time. Th e effect of harmonics on the overall performance is normally studied a nalytically either by using the symmetrical components method or the r otating field concept. Both methods lead to a cascade type equivalent circuit which can be used to predict performance and as an aid to opti mise the design. For accurate analysis, however, a detailed simulation of the magnetic field distribution is needed. This would normally req uire the time stepping finite element method. Tn this paper, a simple finite element technique to solve, nonlinear time periodic magnetic fi eld problems in asymmetrical electrical machines is proposed. The appr oach is based on a steady-state magnetodynamic formulation together wi th application of harmonic balance to the diffusion equation. The theo ry is verified on a special low speed generator with asymmetry on both stator and rotor.