Magnet topology optimization to reduce harmonics in high-speed axial flux Generators

The effect of the shape and distance between adjacent permanent magnet (PM) poles on the quality of the output voltage of an ironless axial flux PM generator is investigated. Two possible magnet shapes, semicircular and trapezoidal, with equal volume and surface area, are modeled using a three-dimensional finite-element method (FEM). For each particular magnet shape, the space between the adjacent magnets on the same rotor is varied, the induced voltages are analyzed, and the harmonics contents determined. The results obtained from the FEMs are favorably compared to the experimental results obtained from a particular prototype which was constructed from a semicircular magnet shape.