Investigation of a Two-Dimensional Analytical Model of the Homopolar Inductor Alternator

The homopolar inductor alternator (HIA) has some merits over classical machines for applications such as a high-temperature superconducting machine and as flywheel energy storage system. For the design of HIA, the back electromotive force (back-EMF) and air-gap flux density are two key parameters. Due to the intrinsic three-dimensional (3-D) magnetic circuit structure, 3-D finite-element analysis (FEA) is required for accurate modeling of HIA, which is, however, very consuming. To solve this problem, a 2-D analytical model is proposed in this paper. First, the method of air-gap flux density spatial overlay analysis is illustrated. Based on it, the structure and equivalent principle of 3-D converting to 2-D model of HIA are investigated. Finally, the analytical model is applied to HIAs with different rotor structures to prove the accuracy of the proposed model. An experimental platform is built to verify the effectiveness of this model. The results indicate that the proposed model can accurately calculate the back-EMF and air-gap flux density. Meanwhile, it takes much shorter time than 3-D FEA method does.