Ultraminiaturized Milliwatt-Scale Permanent Magnet Generators

This paper reports the design, fabrication and experimental characterization of ultraminiaturized, axial-flux, permanent-magnet (PM) generators intended for milliwatt range systems. The miniaturization of PM machines is attractive because scaling laws are favorable, but integration of ultra-small permanent magnets is challenging. The generators are 2-pole, multi-turn, 2-mm diameter machines. A single-phase, open-circuit voltage of 51 mVrms has been measured at 392 krpm, which approximately corresponds to 3.6 mW of DC power to a load resistance at the point of maximum power transfer, indicating that this approach shows great promises for milliwatt-scale power devices.