Kuo-Chi Chiu

Low cogging torque and high efficient 3-phase spindle motors by reshaping magnetic circuit profiles

The dynamic characteristics of a 3-phase spindle motor with 12-poles and 9-slots can be improved by reshaping the magnetic circuit profiles. The stator cores were designed with different ratios of x/y where x is the gap angle between 2-slots and y is the expanded angle of a slot. Experiment and finite element analyses (FEA) results show that x/y ratio of 1/2.5 is an optimal design in achieving dynamic performance for DVD drives applications.

The effect of different profiles of the rotor magnet in an aquatic ac synchronous motor

The cogging torque of the aquatic ac synchronous motor is sensitive to the magnetization profiles, the relative angular offset, the magnetic field strength of the rotor magnet, and the structure of the stator core. With the same magnetic profile of the rotor magnet, the cogging torque of the motor is proportional to the trough width of the stator core. For different magnetic profiles of the rotor magnet combined with the same stator core, the cogging torque of the motor varied markedly with the magnetic profiles of the rotor magnet. The computed values of the cogging torque of the motor are in excellent agreement with the experimental values.

Field improvement of fine magnetic pole pitch fabrication on printed circuit board using a dual layer structure

Fine magnetic pole pitch of less than 1 mm fabricated on printed circuit board with different magnetic poles on single and dual layer structures were analyzed. The central consecutive magnetic poles of magnetic flux density distributions were measured using a Hall probe. The measured values were found in agreement with the calculated values.

Optimal design of fine magnetic pole pitch fabricated on printed circuit board

Using traditional methods, a permanent magnet multipole component magnetized with a magnetic pole pitch of less than 1mm is very difficult to achieve and a costly, complicated magnetization system is required. In this paper, the optimal design of a fine magnetic pole pitch of less than 1mm fabricated on a printed circuit board has been successfully investigated and demonstrated. An optimal magnetic pole pitch having large variation and strength in magnetic-flux density was obtained. The characteristics of the optimal magnetic pole pitch are good for signal detection and processing. The measured values of the magnetic-flux density in the z component are in agreement with the calculated values.

Performance improvement of spindle motor for DVD drive

The brushless spindle motor is widely used for the DVD application. The performances of reading and writing for DVD drive are highly dependent on the dynamic characteristics of this motor. In this paper, a spindle motor with 12-pole, 9-slots, radial winding and driven by the 3-phase circuit is investigated. The dynamic characteristics of spindle motor could be improved by reshaping the magnetic structure. The ratio defined as the expansion angle of opening between two adjacent slots to the expansion angle for each slot are changed with different value to study the improvement effect for the spindle motor. According the experimental results, the ratio with 1/2.5 is the optimal design for this paper.

BACK ELECTROMOTIVE FORCE ENHANCEMENT FOR A NEW SINGLE-PHASE SYNCHRONOUS MOTOR

In this article, the back electromotive force (emf) of a new single-phase synchronous motor of the two-pole type useful in aquarium application is studied. Based on a two-dimensional model, the finite-element method is used to numerically analyze the magnetic field distribution inside the motors, from which the back emfs can be computed. Three different shaping schemes on the stator are investigated, with the objective of enhancing the back-emf constant as well as eliminating the starting dead point. Experiments are conducted on one of the shaping schemes, where the measured data are found to agree very well with the numerical results. To predict the transient behavior of the motors in the startup period, parameters extracted from the numerical results are built into a database. From this database a set of dynamic equations governing the current and angular speed can be constructed, which provides significant accuracy as compared with the experimental values.