부산대학교 도서관

Electrical conductivity is an essential parameter to evaluate the conductivity property of metal materials, which has been widely used in the inspection and sorting of metal materials. In this article, a novel conductivity measurement method is proposed based on the eddy-current field of a moving conductor, which can be used in conductivity measurements for arbitrarily finite-size conductors. The measurement method is obtained by solving the eddy-current density in the moving conductor first and then treating it as an excitation source to solve the induced voltage in the pick-up coil; the final conductor conductivity can be directly calculated by using the measured values of induced voltage, parameters of the conductor (size, spatial position, and moving speed), as well as the parameters of coils and dc excitation current. Later in the experiments, the finite-size metal cylinders and balls are chosen, and the relative errors of average calculated conductivity and standard conductivity are within 3%. In fact, the analytical method in this article is applicable to conductivity measurements of arbitrarily small-size conductors, such as short cylinders or tubes, small balls, toroidal bodies, etc. In addition, there is no need to establish different analytical models for different shaped conductors, as well as no need to solve governing equations and boundary conditions containing velocity terms. The conductivity can be calculated directly by analytical expression, without numerical inversion, hence the calculation results are stable and reliable. Finally, the research results of this article can be used for high-speed, online, and real-time sorting of metal materials.