Investigation on Magnetic Torque of Multi-Polarly Micro Rotor Using Shape-Magnetic-Anisotropy

A double pole pair milli-size rotor with 1 mm in outer diameter and 0.3 mm in inner diameter was fabricated from an isotropic laminated film magnet with a non-magnetic material. Permeance coefficient distribution together with static magnetic field of the film were also estimated by using 3-D and 2-D finite element model, and the average permeance coefficient, B/¿oH, could be estimated as 18.7. A torque of the isotropic film magnet with the remanence value of approximately 1 T was measured under the different field strength, and a relative torque and relative torque constant, dT/dH-gradient, of the above-mentioned magnet with the double pole pair increased by 172% and 152%, respectively, compared with those of an anisotropic bulk magnet with a single pole pair whose remanence value was approximately 1.3 T. It was found that use of isotropic laminated film magnet is effective in obtaining a micro multi-polarly magnetized rotor with highly dense torque.