Tai-Fa Ying

Simulation Study Of The Reduction Of Cogging Torque In Permanent Magnet Motors

The reduction of cogging torque in permanent magnet motors has been studied by varying the geometry shape of the saliencies of the armature core on stator of a 12-pole 9-tooth spindle motor. Mechanism of this reduction is explained by the minimum net integral of the product of normal and tangential magnetic flux with respect to the mechanical angle between the stator and rotor.

Cogging torque reduction of a single-phase brushless DC motor

In this research, the cogging torque of a newly designed single-phase brushless DC motor used in CD-ROM application is investigated. A finite element method is employed to numerically analyze the magnetic field distribution inside the motor, in which a three-dimensional mesh is constructed. The torque due to the magnetic coupling between the rotor and stator is estimated based upon the virtual work concept. It is proposed in this paper that the salient pole be divided into several regions in the azimuthal direction. By properly choosing the radii for these regions, the cogging torque can be greatly reduced.

The radial magnetic coupling studies of perpendicular magnetic gears

The torque of the radial magnetic coupling between perpendicular magnetic gears with different magnetic poles has been investigated experimentally. The torque of magnetic coupling decreases with increasing the distance between the magnetic gears. For different multipole magnetic couplings with the same magnetic field strength, the torque of magnetic coupling increases as the number of magnetic poles increases for distances smaller than a critical separation distance d/sub c/, but it is reversed as the separation distance becomes larger. This critical separation distance for our sintered NdFeB magnet system with an iron yoke of 2 mm thickness is roughly between 9 and 11 mm. This phenomenon is explained by analyzing the magnetic coupling strength of different poles of magnets on the perpendicular magnetic gears.

Magnetic coupling studies between radial magnetic gears

The torque of a magnetic gear system with different magnetic poles has been investigated by computer-aided simulation with 2 dimensional modeling processes of finite element analysis. With a fixed separation of distance, the torque shows a maximum for a special number of poles, which shifts to a higher number of poles as the ratio of the radius to the thickness of the magnets increases and shifts to a lower number of poles with addition of an iron yoke. Using this technique, we can obtain an optimum design of a radial magnetic gear system for practical usage.

A new type single-phase spindle motor for HDD and DVD

The cogging torque and dynamic performance of a newly designed single phase brushless DC motor have been investigated in this paper. The single phase brushless spindle motor is usually applied for cooling fan, pump and blower before the performance is improved by the reengineering process. The stator configuration and the drive circuit have been remodeled in order to meet the requirements of the spindle motor used in the DVD and HDD applications. The cogging torque is reduced to 18 g-cm by the salient pole reshaping. An automatic phase adjuster is also introduced to improve the performance of the dynamic characteristics of a single phase spindle motor in this paper. According to the test results, the maximum speed could be increased from 6500 rpm to 12000 rpm and the efficiency from 22% to 38%. A single phase motor has been demonstrated successfully in HDD and DVD applications by reshaping for the salient pole and phase adjusted automatically with the rotation speed.

Study of a high efficiency and low cogging torque spindle motor

A high efficiency and low cogging torque spindle motor has been designed by varying the magnetization profiles of the rotor and the geometry shape of the teeth of the stator in motor. Both radial and fixed magnetization profiles for the magnetic ring in a spindle motor were studied by computer simulation and experimental measurement. After smoothing the edge of the teeth of the stator, we can reduce the cogging torque tremendously. Experimental data are in good consistent with theoretical calculation.

A new automatic phase adjustment of optical drive signal

A new type automatic phase adjuster has been developed to improve the performance of single phase brushless D.C. motor, and provide good accelerating/decelerating capability for achieving the demands of the spindle motor of optical drive. It also had been successfully applied in 8-speed, 12-speed and 16-speed spindle motors of CD-ROM drives.

Torque and cogging torque in sandwich type CD-ROM spindle motor

The sandwich type CD-ROM spindle motor has intrinsic dominance of manufacture and cost. This paper will propose a reference formula of torque constant Kt according to the experimental results, accounting for the mechanism of dead point, and finally introducing a design method to prevent dead point and to reduce the cogging torque.

The dynamic performance affected by the axial magnetic force for a DVD spindle motor

The axial magnetic force induced by rotor and stator is an important performance index to affect the dynamic characteristic on a high-precision DVD spindle motor design. In this research, the axial magnetic forces are calculated at varying relative heights between rotor and stator by 3D finite element method (FEM), and compared with the experimental data. Based on the results of simulation and measurement of the axial magnetic forces, the dynamic vibration could be apparently improved and decreased from 76.7 to 3.85 mg at 6000 rpm with disc by a variation of relative height on a DVD spindle motor. The torque constant and running current are also applied as performance indices to evaluate dynamic performance in the paper.

The performance of a single-phase DC brushless motor utilizing the ferromagnetic base material

Abstract In this paper, the effect of the magnetic base plate on a single-phase sandwich-type brushless DC motor is investigated. The simulation indicates that the cogging torque increases and torque constant k t and coefficient of back emf k e decrease in comparison with a nonmagnetic base plate.