The Directional Electromagnetic Shielding Technology In The Current Measurement Of The Aluminum Refine Cell

Large aluminum refiner plan is a very special, complex and strong magnetic field environment. In this environment, the common measurement technology and equipment of the anode leader current measurement cannot be used. As a result of that, the roasting process of aluminum refiner cell can’t be effectively, quantitatively and accurately controlled. The research group proposed a method of using Hall component to measure the current of anode anode leader, but the Hall component is easily affected by the interfering magnetic field. In order to solve the problem that the Hall component is easily affected by the interfering magnetic field, we proposed to exert the shielding outside of the Hall component to eliminate the influence of interfering magnetic field.Firstly, based on the theory of electromagnetic shielding, analyzed and summarized the basic theory of directional electromagnetic shielding technology, including the concept, the radial shielding principle, the radial boundary condition, the axial shielding principle, the shielding material, the shielding effectiveness and the calculation method of the shielding effectiveness for the points in the target area, and derivate the formulas of the shielding effectiveness in the target area.Secondly, discussed the measuring device of the aluminum anode leader current, analyzed the relationship between the anode leader current distribution and the magnetic field distribution model around the anode leader. Then, established the magnetic field distribution models around the anode leader before and after shielding. With the help of the method of the magnetic scalar potential and the magnetic vector potential in the ANSYS of the finite element analysis software, respectively do the simulations for the two models. After the simulation, chose several points in the target area (the place where the Hall component was added), listed the intensity of magnetization and component in the direction of x、y and z axis in the magnetic field distribution models around the anode leader before and after shielding, and calculated the effectiveness for the points. With the help of the formulas, calculated and got the shielding effectiveness, then analyzed the shielding results.Again, at the basis of the magnetic field distribution model around the anode leader before and after shielding, studied and analyzed the influence on effectiveness in the target area from shielding body geometry and material properties, and get the choice range of the thickness、the length and the material of the shielding. Then, according to the distance between the center of the target area and the anode leader、the quantity and the type of the Electrified conductor, respectively established magnetic field distribution model around the anode leader before and after shielding, analyzed the influence on the shielding effectiveness of the points in the target area from the distance between the center of the target area and the anode leader and the quantity and the type of the Electrified conductor.