Design of high speed flywheel motor/generator for aerospace applications

by Wang, Wensen.

iii Compared with traditional electro-chemical battery systems, a high speed flywheel energy storage system offers the attractive characteristics of high power density and attitude control in aerospace applications. In this thesis, a detailed illustration of the design of a high-speed flywheel permanent magnet motor/generator is presented. Several analysis techniques were used in the design process, including anisotropic electromagnetic and structural continuum solutions and design optimization techniques for the machine and the flywheel inertial rim. Finite Element Analysis (FEA) was conducted to validate the resulting design. The goal of the motor/generator is to provide 100W over a speed range of 150 - 300 krpm. High energy product rare-earth permanent magnet, ultralow loss amorphous iron material, and carbon composites were utilized in the flywheel construction to allow the motor/generator to satisfy the electromagnetic and structural requirements while maximizing energy storage. Special manufacturing and assembly procedures were developed to build this small system. Two-plane rigid body balancing has been implemented to balance the high speed rotor of the system. A field-oriented position sensor-less control scheme was implemented to accomplish spin tests of the motor/generator up to 32,000 rpm with contact ball bearings. The combination of these tests with parameter measurements suggest that the motor/generator design has the potential to achieve the desired power with sufficient efficiency at high speeds with magnetic bearings and a vacuum environment.