Microfabricated high-speed axial-flux multiwatt permanent-magnet generators- Part I: Modeling

This paper presents the modeling of permanent-magnet (PM) generators for use in microscale power generation systems. The generators are three-phase, axial-flux, synchronous machines, each consisting of a multipole, surface-wound stator and PM rotor. The machines are modeled by analytically solving two-dimensional (2-D) magneto-quasi-static Maxwell's equations as a function of radius. The 2-D field solutions are then integrated over the radial span of the machine to determine circuit parameters such as open-circuit voltage and inductance as well as hysteresis loss in the stator core and eddy current losses in the stator core and windings. The model provides a computationally fast method to determine power and efficiency of an axial-flux PM machine as a function of geometry, speed, and material properties. The open-circuit voltage predictions are also shown to agree well with 3-D finite-element analysis simulation results.