Compact Permanent Magnet Power Supply for Directed Energy

摘要

There is a growing need for light and compact power generation in mobile and space-constrained platforms. The transient load profiles typical for advanced weapons demand energy storage that can be charged and discharged quickly and fail benignly. A composite flywheel-based electromechanical battery (EMB) operating at high-speed provides compact and lightweight energy storage and minimal degradation over a large cycle life without the hazards associated with a battery or capacitor failure. Moreover, it can be designed with a generator capable of rapid recharging, as the charge rate is governed by mechanical inertia rather than electrochemistry. A topology that shows promise is an arbor-based EMB with an integral PM motor/generator for rapid recharging. An inside-out PM motor/generator allows the magnets to be structurally supported at the inner diameter of the rotating arbor/flywheel with an interior stator winding. The arbor connects the high-strain flywheel rim and a low-strain rotor hub while providing structural stiffness and torque transmission. A composite arbor enables a lightweight structure that can operate at top speeds several times higher than metals with material properties engineered to strain match the flywheel rim. The higher speed is important because the stored energy scales linearly with mass but with the square of velocity. So small high-speed rotating machines can have high power and energy density. Even with the potential benefits, the technology is not commonplace because of two technical challenges. One is composite arbor development and the other is removal of rotor heat due to windage and magnet losses. An EMB concept with an integral PM motor/generator will be presented, which addresses these issues in the 100 kW power range and can store tens of MJ. Utilizing a composite arbor design validated by spin test saves significant development time and cost, and active rotor cooling enables a significant increase in performance.