[Answer] A Cute Question: Why Is an Air Circuit Breaker Called an “Air” Switch?

[Answer] A Cute Question: Why Is an Air Circuit Breaker Called an “Air” Switch?

Everyone’s answers are basically correct. An air circuit breaker is called that because it uses air as the arc-extinguishing medium. In other words, at relatively low voltages, an electrical arc can be extinguished in air, so these breakers are generally used in low-voltage systems, typically 380V and below.

If the voltage level is higher, such as 10kV to 35kV, then vacuum circuit breakers are used. That means the contacts are placed inside a vacuum interrupter, which makes it easier to extinguish the arc.

At even higher voltages, SF6 circuit breakers are used, meaning the contacts are placed in sulfur hexafluoride gas, which is much harder to ionize.

In the past, older circuit breakers also used oil as the arc-extinguishing medium, but because of certain safety risks, they have now been almost completely phased out.