Attractive and repulsive forces of ferromagnetic materials in time-varying electromagnetic fields

Electromagnetic forces of ferromagnetic materials consist of attractive and repulsive components, which can be introduced from the Lorentz force formula and the Kelvin force formula. In harmonic fields, the attractive and the repulsive forces both have DC and AC components and they cancel out with each other to reduce the total average force. The contributions or influences of the frequency, magnetic permeability and electric conductivity of the material to attractive and repulsive forces in time-varying fields are analyzed and simulated by the numerical experiments using FEM methods. Results show that the total time average electromagnetic forces can be reduced greatly, even to zero in certain states, which is useful to control the vibration problem.