Dynamic Induction Charging of Particles with Finite Conductivity

Despite the common belief that in the process of induction charging the charging time constant and the relaxation time constant are equal, there is no proof that these parameters are related at all. The purpose of this paper is to determine the actual induction charging time constant for practical types of particles having both finite conductivity and permittivity. All investigations were based on numerical simulations done for idealized geometric models of the problem. The model was developed for the transient case and solved by using the COMSOL commercial software, which is based on the Finite Element Method. Spherical and rough particles with various contact areas with the grounded electrode were considered. The surface conduction of the particle was neglected. The effect of the particle contact area, conductivity, and permittivity on the actual charging time constant was investigated and the results were compared with that predicted by the classic relaxation time constant as defined by the material properties. It was found that the actual time constant is not equal to the relaxation time constant but is directly affected by the value of the contact area between the particle and ground electrode.