The most basic classification of circuit breakers-ACB MCCB MCB

Circuit breakers, which fall into three broad categories.

The first type is called air circuit breaker or air-insulated circuit breaker. The symbol for a frame Breaker is ACB, since the word Air is Circuit and the word Breaker is Breaker.

The second type, called molded case circuit breaker, is MCCB;
The third type is the miniature circuit breaker, whose symbol is MCB.

The rated current range of ACB is from 1250A to 6300A, the maximum rated current range; The rated current range of MCCB is from 10A to 1600A, with the rated current range in the middle. The MCB has the smallest current rating range, from 6A to 63A, but it is the mainstay of home circuit breakers.
No matter which kind, the insulation between the contacts inside the circuit breaker relies on air, which is also the reason why the MCB is commonly known as the air switch.
Since the insulation between the contacts inside the circuit breaker depends on air, it is necessary for us to discuss the breakdown characteristics of air, as well as some basic knowledge of the arc.

2. About arc

We see the arc as a cloud of hot gas. Inside the arc, at temperatures above 3,000 degrees, electrons escape from the atoms to form negative ions, which are lost so that the air molecules are all plasma, a mixture of electrons and positively ionic gas.

3. Opening distance of the circuit breaker

Frame circuit breaker ACB, the shortest distance between the moving contact and the static contact is called open distance.
The opening distance is used to ensure that the air between the open contacts does not undergo electrical breakdown.