What Does an Air Circuit Breaker Use to Blow Out the Arc? Breaking Down How Arc Chute Splitter Plates Work - Blog

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"Blowout" Does Not Mean Compressed Air

The "blowing out" mentioned here does not mean using compressed air to blow the arc away. In a standard low-voltage air circuit-breaker, when the electrical circuit is interrupted, the contacts move apart and a strong electric field ionises the air, thereby creating a high-temperature conductive electric arc. If the electric arc is not extinguished, current may continue to flow through it; therefore, the electric arc must be cooled, lengthened and extinguished as quickly as possible.

Arc Chute Splitter Plates and Electromagnetic Force

The arc extinguishing chamber usually contains many parallel metal plates; these are the arc splitter plates. The arc current generates a magnetic field. Under the action of the arc chute structure or a magnetic blowout coil, the arc is subjected to an electromagnetic force, stretched, and driven between the splitter plates.

As soon as the arc enters the splitter plates, it is cut by the metal plates into many short arcs connected in series. Each short arc has a certain voltage drop near its cathode and anode. When these short arcs are connected in series, the total arc voltage rises rapidly, making it difficult for the power source to maintain the arc. At the same time, the metal splitter plates have good thermal conductivity and absorb a large amount of heat, cooling the arc column, causing charged particles to recombine and reducing conductivity. This process is called deionization.

For an AC arc, the current naturally crosses zero every half cycle, and the arc temporarily goes out. If the splitter plates can rapidly cool the arc path and quickly restore dielectric strength, the recovery voltage cannot re-break down the air, and the arc is truly extinguished.

Combined Arc-Extinguishing Action

Therefore, arc splitter plates do not rely solely on "blowing air"; they extinguish the arc through the combined action of electromagnetic arc stretching, short-arc splitting, cooling and deionization, and AC current-zero extinction.