Arc extinguishing is one of the important applications of circuit breakers, because the arc will not only damage equipment lines, but also affect personal safety. So what is the necessity of arc extinguishing? Generally, there are four methods of arc extinguishing, including mechanical arc extinguishing, magnetic arc extinguishing and so on. In this paper, I describe the common methods of arc extinguishing and the arc extinguishing principles of some common circuit breakers.

    Firstly, the commonly used arc extinguishing methods are discussed. There are mainly four kinds of arc extinguishing methods: arc extinguishing, arc extinguishing, arc extinguishing and arc extinguishing.

    1. Mechanical arc extinguishing: The arc is rapidly elongated by the limit device. This method is mostly used in switchgear.

    2. Magnetically blown arc extinguishing: Under the action of a magnetic field produced by a magnetic blown coil in series with contacts, the arc is elongated by electromagnetic force and blown into an arc extinguishing hood composed of solid medium, which contacts with solid medium, and the arc is cooled and extinguished.

    3. Narrow slot (longitudinal slot) arc extinguishing method: Under the action of magnetic field electrodynamic force formed by arc, the arc can be elongated and entered into the narrow (longitudinal) slot of arc extinguishing hood. Several longitudinal slots can divide the arc into several segments and contact with solid medium, and the arc will quickly extinguish. This structure is mostly used in AC contactors.

    4. Grid arc extinguishing method: When the contacts are separated, the arc generated is pushed into a group of metal grids under the action of electric power and divided into several segments. Each of the metal grids insulated from each other is equivalent to an electrode, so there are many anode and cathode voltage drops. For AC arc, when the arc passes zero, a medium strength of 150 V to 250V will appear near the cathode, which makes the arc unable to maintain and extinguish. Because the effect of grid arc extinguishing is much stronger than that of DC arc extinguishing, grid arc extinguishing is often used in AC electrical appliances.

    These methods are mainly aimed at some low-voltage circuit breakers. To understand the reasons for adopting these methods, it is necessary to clarify the principle of arc extinguishing of circuit breakers.