Design Considerations of 2-D Magnetizers for High Flux Density Measurements

A 2-D magnetizer introduces variation in the flux density (B) across the sample under rotational magnetization. This variation requires additional energy requirements that limits the attainable aspect ratios, flux density levels and stresses the supply. A numerical methodology that accounts for the flux leakage and the eddy currents is proposed to analyze uniformity and variation in B in four 2-D magnetizers. The analysis was done beyond the knee of the magnetization curve. Numerical results will show that round magnetizers can mitigate the variation of the square magnetizer by over 92%, by making the MMF more sinusoidal and equalizing the reluctance along the airgap. In addition, deeper yokes minimized the variation by about 50% in the square and the Halbach testers. The results of this analysis was a design that mitigates the variation in B by a combination of sinusoidally distributed windings, and a deep yoke. The proposed magnetizer achieved very high flux densities over a relatively wide frequency range, which were 2.04 and 1.69 T at 60 Hz and 1 kHz, respectively.