A Printed Circuit Board Stator Pattern for Loss Trade-Off Mitigation in Slotless Axial Flux Permanent Magnet Motors

This study proposes a printed circuit board (PCB) stator pattern for alleviating the trade-off between DC copper loss and AC winding loss in a slotless axial flux permanent magnet motor (AFPM). The proposed pattern has a structure in which the width of the effective conductor region directly exposed to time-varying magnetic flux is reduced, and two additional conductors with the same width are placed within the available axial space and then connected in parallel through vias. Three-dimensional finite element analysis was performed while varying the effective conductor width ratio from 0.3 to 0.8, and an additional refined sweep was conducted in the range of α = 0.5–0.6, where the minimum total winding loss appeared in the initial sweep. Under the rated operating condition, the minimum total winding loss was obtained at α=0.53 based on the refined sweep results. Under this condition, the phase resistance, DC copper loss, AC winding loss, and total winding loss were reduced by 11.82%, 12.1%, 15.09%, and 12.48%, respectively. As a result, the efficiency increased from 81.53% to 83.5%, while the back electromotive force (BEMF), torque, and output were nearly unchanged. In addition, the AC winding loss distribution decreased in both the coil region closest to the magnets and the coil region farthest from the magnets. These results demonstrate that the proposed pattern is an effective design method for improving the winding loss characteristics of slotless PCB AFPM without meaningful degradation of the fundamental electromagnetic performance.