Numerical analysis and design optimization of a homopolar inductor machine used for flywheel energy storage

This paper investigates a homopolar inductor machine (HIM) for flywheel energy storage in electromagnetic launch applications. An equivalent 2-dimension (2-D) finite-element model is presented to predict the machine behavior, and the effectiveness of the equivalence is validated by the comparison of 2-D and 3-D results. Based on the 2-D model, the rotor tooth shape is then optimized so as to achieve high fundamental value of the air-gap flux density for a given rotor diameter. It is shown that the proposed 3-D to 2-D equivalence can predict the performance of the HIM in an accurate and fast way, which is quite valuable in the design stage of a HIM.