The torque of magnetic coupling with different magnetic poles has been investigated by theoretical computations with two dimensional modeling processes of finite element analysis. The torque is sensitive to the number of magnetic poles, the material of the magnetic gears, and the distance between the magnetic gears. For a 2 mm separation distance of two magnetic gears with 20 mm radius, the maximum torque occurs between 6 and 20 poles which is dependent on the thickness of the iron yoke inside the magnets, and on the magnetization configuration within a pole of the magnets. This is explained by analyzing the magnetic coupling strength of each pole. Finally, the computer calculation is tested using an experimental data taken from a sintered NdFeB magnetic gear.
The phase evolution, microstructure, and magnetic properties of melt spun SmCo7−xNbx (x=0–0.6) ribbons have been investigated using powder x-ray diffraction, transmission electron microscopy, and vibrating sample magnetometer, respectively. SmCo7−xNbx ribbons could crystallize in TbCu7-type structure only for low Nb substitution of x=0–0.3 at high wheel speed of 30–40 m/s. According to the structure refinement, the doping element Nb prefers to occupy the 2e site. The intrinsic coercivity increases dramatically from 1.9 kOe for SmCo7 ribbon to 10.2 kOe for SmCo6.8Nb0.2 ribbon at wheel speed of 40 m/s. The mechanism of the coercivity enhancement has been discussed. The optimal magnetic properties of σr=54.4 emu/g and Hic=10.2 kOe were obtained in SmCo6.8Nb0.2 ribbon.
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