Abstract: Dynamic stability is the basic function that medium voltage switchgear must have, in the process of dynamic stability test, if the friction between the dynamic and static contact fingers and the closing holding force of the operating mechanism cannot reliably keep the dynamic and static contact fingers in the grounding and closing position, the moving contact fingers will be repelled by the electrodynamic force generated by the short-circuit current and fusion welding or even arcing will occur. With the help of finite element analysis, this paper studies the mechanism of dynamic stability, analyzes the root cause of the electrodynamic action of the charged conductor, and proposes a new method to solve the dynamic stability of the grounding switch, and uses the open magnetic ring to regulate the magnetic field distribution of the moving finger, so as to reduce the electrodynamic force of the moving finger.

    Key words: magnetic ring; electrodynamic force; grounding switch; dynamic stability test