Multidisciplinary Design of High-Speed Solid Rotor Homopolar Inductor Machine for Flywheel Energy Storage System

Homopolar inductor machine (HIM) has been applied in the field of flywheel energy storage system (FESS) due to its merits of simple structure, brushless exciting, and low idling losses. The rotor of HIM not only plays the role of energy conversion but also serves as a flywheel to store kinetic energy, which is different from other electrical machines used in FESS. Meanwhile, the HIM usually operates at high speed to improve the power density and storage energy. To obtain good performance and high reliability, the design and optimization of HIM should consider multiphysics, including storage energy, electromagnetic performance, rotor stress and dynamics, and so on. However, the existing researches mainly focus on the analysis of electromagnetic performance and lack multidisciplinary design. To solve this problem, a multidisciplinary design method of HIM is proposed and investigated. First, the operation principle of HIM is illustrated, and the multidisciplinary design method is proposed. Then, the storage energy, electromagnetic performance (including no-load air-gap flux density, saliency ratio, torque, and electromagnetic power), rotor stress, and modal of HIM are deeply analyzed according to the proposed design flow. Finally, a prototype of HIM is manufactured and tested. The results calculated by finite-element analysis are validated by experiments. The design method proposed in this article provides a straightforward procedure for the multidisciplinary design of HIM.