Torque in nested Halbach cylinders

Permanent magnet variable flux sources are produced by rotating two nested N-segment, permanent magnet, Halbach cylinders. Torque is primarily an end effect, determined by field nonuniformities due to the finite length and segmented structure of the cylinders. Due to symmetry, one cylinder experiences zero torque in a uniform applied field. Experiment and numerical simulation reveal that the torque is composed of a dominant term of frequency 1/(2π) and harmonics at (kN±1)/(2π), where k is an integer