3-D Transient Finite-Element Analysis and Experimental Investigation of Short-Circuit Dynamic Stability for Air Circuit Breaker

Short-time withstand current ( $I_{\mathrm{ cw}}$ ) is a crucial parameter of air circuit breakers (ACBs) due to the selective protection. Considering the skin effect, the interphase effect, and the nonlinear $ {B}$ – $ {H}$ characteristics of ferromagnet, the 3-D transient finite-element method is adopted to analyze the short-circuit dynamic stability of a three-phase ACB. The transient current, the repulsion torque, the tilting torque, and the sliding torque on each movable conductor are calculated at the beginning stage and the periodic stage of $I_{\mathrm{ cw}}$ , respectively. It is found that the electromagnetic torque tilts and slides the outer movable conductors toward the middle of each phase. The movable conductors of phase B perform the worst in the aspect of dynamic stability. The relevant experiments are also conducted to investigate the dynamic stability through observing the position, the size, and the sliding trace of the erosion marks on contact tips. Based on the proposed calculation model, it is found that installing ferromagnet plates on both the sides of movable conductor groups can enhance the dynamic stability.