A circuit breaker is a switching device that can close, carry and break current under normal circuit conditions, and can close and carry current under abnormal loop conditions (including short-circuit conditions) within a specified time. It is a kind of switch, but it is different from the switch we use. The circuit breaker is mainly used to cut off the current of the high voltage circuit. When our system fails, the current can be cut off quickly, thus preventing the situation from going to serious development. Achieved the role of protecting people's property. It is a good security device.


For low-voltage electrical appliances, the air switch is a circuit breaker that cuts off the short-circuit current. The high-pressure air switch is another matter. So, is the circuit breaker an air switch?

The answer is no, low-voltage circuit breakers can be divided into low-voltage molded case circuit breakers and low-voltage frame type circuit breakers. The former is used for low-voltage and low-current, the latter is used for low-voltage and high-current, and the low-voltage molded case circuit breaker is commonly called automatic air switch.

Several definitions in China's national standard GB14048.2 (mandatory standards, want to know more about low-voltage circuit breakers to see this standard):

1. Circuit breaker: A mechanical switching device that can switch on, carry and break the current under normal circuit conditions, and can also be connected to a specified abnormal circuit (such as a short circuit) to carry a certain time and break current.

2. Molded case circuit breaker: A circuit breaker with a casing made of molded insulation material as an integral part of the circuit breaker.

3. Air circuit breaker: A circuit breaker that opens and closes the contact air in atmospheric pressure.

4. Vacuum circuit breaker: A circuit breaker that opens and closes the contact in a high vacuum tube.

5. Because the molded case circuit breaker generally uses air as the arc extinguishing medium, there is a common name for the air switch, but the air switch is not strictly rigorous because the air switch and the circuit breaker are different concepts.