Numerical analysis and simulation of magnetic flux and force in a three-coil system

When an electric current flows through a coil, a magnetic field concentrating on the space surrounding the coil is created. By controlling the change of discharge current, there would be a great difference in the electromagnetic force between two coils. Assuming that the directions of the currents flowing through two coils are uniform, the electromagnetic attractive force can be generated. Otherwise, it would cause repulsion. For decades, the research and application about the electromagnetic force has been a hot spot. In this paper, a typical system of three coaxial coils is taken as an example to analyze the magnetic flux distribution and electromagnetic force with each coil, as shown in Fig. 1. The coil formers are all alike. According to Gauss theorem and Ampere's circulation theorem, the basic electromagnetic equations of single coil are described. The electromagnetic attractive/repulsive force between two coils is derived from an equivalent circuit model. The effect of the structural parameters of the coils (inner diameter, outer diameter, turns), polarities of three coils' discharge currents, magnitudes of discharge voltages and the distance between coils on the characteristics of electromagnetic force are investigated and discussed by finite element method. Furthermore, keeping the coil 1 and coil 3 at a fixed position, the motion behavior of coil 2 driven by the electromagnetic force is carried out. For a given distance between coil 1 and coil 3, the optimal position where the coil 2 can get the maximum velocity approaching the coil 3 is found by numerical studies. The obtained results could be helpful and provide a new way for pile driving.