Development of an alterable and rotary permanent magnetic field

In this paper, a system that can produce alterable and rotary permanent magnetic field is developed. It can be used for crystal growth, chemical crystal and biologic cell, etc. A homogeneous magnetic field can be produced in the central region by two annular permanent magnets, and the density of magnetic flux is controlled by changing the angle of the magnetic field produced by the inner annular magnet and that produced by the outer annular magnet. The angle can vary continuously from 0 to 180 degree, consequently, causing the density of magnetic flux varied from 0.006 to 0.18 Tesla. To obtain a rotary magnetic field, the two annular magnets are driven to rotate synchronously. After the wanted magnetic field is achieved, the relative position of the inner and the outer annular magnet is fixed, thus, the inner and outer annular magnets can rotate synchronously at a given speed. The rotation speed up to 20 rad/min can be achieved. A monitoring system, based on industrial computer, is used to set parameters to control the magnetic field and the rotation speed, and to show the real-time operation parameters and working status of the system. Through experimental verification, the measured data has good agreement with the given value. The system is also applied on a furnace for single crystal growth, the result shown that the quality of the single crystal being grown under magnetic field is significantly improved when compared to those grown under no magnetic field.