Preliminary Design and Operating Region Analysis of a Quad-Winding Axial-Flux PMSG Using the Loading Distribution Method

This paper presents the preliminary design and operating region analysis of a quad-winding axial-flux permanent magnet synchronous generator (AF-PMSG) using the loading distribution method. The configuration comprises four electrically independent three-phase winding sets sharing a common stator core and rotor. Starting from the rated output power, rotational speed, and terminal voltage, reference machine dimensions and electromagnetic parameters are calculated using radial-flux loading equations, and an approximate axial-flux geometry is generated through active surface area equivalence. The stator slots and total rated output capacity are equally allocated among the four winding sets while maintaining the rated terminal voltage of the baseline single-winding generator. Preliminary winding specifications and electrical parameters are calculated, including winding turns, conductor cross-sectional area, phase resistance, phase inductance, and current density. The procedure is implemented in MATLAB R2024a to generate two- and three-dimensional machine geometries and calculate operating characteristics over a range of rotor speeds and terminal voltages. Torque–speed envelopes and maps of electrical output, efficiency, and power factor are analytically estimated from the reference machine model under the prescribed ideal equal-sharing assumption and are not experimentally or FEA validated. A 600 W, 1500 rpm design is examined, with each winding set assigned a rated output of 150 W. The combined output reproduces the baseline output characteristics under the prescribed allocation, confirming calculation consistency within the analytical model. The developed procedure integrates reference sizing, winding rating allocation, geometry generation, and operating region analysis to provide initial specifications for the detailed design of a quad-winding AF-PMSG.