Non-uniform pinching of short-gap intermediate frequency vacuum arc without controlled magnetic field

The 3 mm short-gap butt contact has a compact size and simple structure. According to experimental results, its current interruption ability exceeds 12 kA in the 360–800 Hz range, meeting the demands of aviation power systems. Thus, it is feasible to use it as an aviation variable frequency protective device. However, in high current model, the intermediate frequency vacuum arc inside the butt contact exhibits non-uniform pinching, leading to increased pressure and energy inside the arc. This results in a mixed jet of plasma and droplets, which is a significant factor limiting the further improvement of the current interruption ability. To thoroughly investigate the mechanism of non-uniform pinching in short-gap butt contacts without a controlled magnetic field, a dual-temperature magnetohydrodynamic model of the intermediate frequency vacuum arc is established in this paper. The reason for the ion convergence towards the center under the self-generated magnetic field are analyzed from the perspective of Lorentz force. Additionally, the reasons for the changes in arc pressure and temperature near the anode area are analyzed based on the energy exchange between electrons and ions. The conclusions of this paper can provide an important theoretical basis for optimizing aviation vacuum circuit breakers.