Microfabricated high-speed axial-flux multiwatt permanent-magnet generators--Part II: design, fabrication, and testing

This paper presents the design, fabrication, and characterization of permanent-magnet (PM) generators for use in microscale power generation systems. The generators are three-phase, axial-flux, synchronous machines, each consisting of an eight-pole surface-wound stator and PM rotor. The devices are fabricated using a combination of microfabrication and precision assembly. Characterization is achieved using a custom-built experimental test stand that incorporates an off-the-shelf gas-driven spindle to power the machines. At a rotational speed of 120 000 rpm, one generator demonstrates 2.5 W of mechanical-to-electrical power conversion and, coupled to a transformer and rectifier, delivers 1.1 W of dc electrical power to a resistive load. This watt-scale electrical power generation demonstrates the viability of scaled PM machines for practical power generation applications. [1701] Index Terms--AC generators, micromachining, permanent-magnet (PM) machines, power microelectromechanical systems (MEMS).