Analysis of Air-Gap Magnetic Field in Homopolar Inductor Alternator by Analytical Method and FEM

This paper investigates the air-gap magnetic field characteristics of homopolar inductor alternator (HIA), including theoretical analysis, numerical calculation, and experiment. First, the structure and magnetic circuit characteristics of HIA are analyzed. Second, a linear model of distributed magnetic circuit of HIA is established. An analytical formula for calculating the main air-gap magnetic field at different axial positions is deduced and obtained. Third, finite element method (FEM) is used to compute the magnetic field of HIA. The results from FEM are nearly consistent with those from analytical method. Finally, a prototype is constructed to verify the theoretical analysis and numerical computation. The research shows that the distribution of the main air-gap magnetic field of HIA is uneven along the axial direction. The proposed analytical formula contributes to calculate the main air-gap magnetic flux density of HIA.