Influences of Closing Phase Angle and Frequency on Electrodynamic Stability of Air Circuit Breaker

Abstract

Short-time withstand current ( $I_{\mathrm{ cw}}$ ) is an important parameter for air circuit breakers (ACBs) and easily causes electrodynamic stability problems. This paper is aimed to investigate the influences of the closing phase angle and frequency on the electrodynamic stability of ACB. Considering the skin effect, the interphase effect, and the nonlinear B–H characteristics of ferromagnet, a calculation model of a three-phase ACB is built based on the 3-D transient finite-element method. It is found that the movable conductors A5, B1, and C1 show the worst electrodynamic stability when the closing phase angle ( $\psi $ ) is equal to $\varphi -\pi $ /2, $\varphi +\pi $ /6, and $\varphi +5\pi $ /6, respectively, where $\varphi $ is the phase angle difference between the voltage and the current. With the frequency increasing from 50 Hz to 100 and 200 Hz, the slope-shaped distribution of peak currents and repulsion forces in phases B and C is changed to the valley-shaped distribution, and the peak current of B1 is increased by 20% and 38.6% at the beginning stage of $I_{\mathrm{ cw}}$ , and by 12.5% and 26.4% at the periodic stage of $I_{\mathrm{ cw}}$ , respectively. In addition, the peak lateral forces of the movable conductors adjacent to other phase are also increased considerably by increasing frequency.