Abstract
Taking the mechanical double-break DC vacuum circuit breaker as the research object, the magnetic field and temperature field distribution between the breaks and the plasma characteristics under the working condition of gap difference caused by actuator dispersion are investigated to explore the difference of arc characteristics between the two breaks with different gaps. Based on the system of equations of Maxwell and magnetohydrodynamic (MHD) equations, a non-simultaneous breaking model of the DB DC VCB is established, and parameters such as magnetic flux density, plasma velocity, inter-contact pressure, and ion and electron temperatures are calculated. The simulation results show that the cathode surface field emission effect is stronger in the small gap break (delayed breaking break). Besides, in the small gap break, the arc temperature in is higher, the rate of decrease of temperature is lower, the electron velocity is higher, the magnetic flux density is lower, the regulatory ability of magnetic field is weaker, and the plasma diffusion speed is slower. In the arc ignition stage, the arc aggregation state duration of small gap break is longer than the normal break, and the arc transition time in small gap break is increased, which means the arc in small gap break get diffusion state later, and it is not conducive to the plasma diffusion and arc energy dissipation. Therefore, the arc energy density between delayed breaking break is greater, the arc morphology transition time is longer, the residual particle concentration after arc extinguishing is higher, and the probability of re-strike breakdown increases with the increase of gap difference. Improving the synchronization of the actuator could improving the breaking ability of DB DC VCB.