What is the breaking capacity of circuit break?
We should choose the right MCCB and circuit breaker hen configuring the electrical switchgear or electrical switchboard.
The breaking capacity of the circuit breaker is an important indicator of the circuit breaker, which refers to the ability of the circuit breaker to safely cut off the fault current. It is generally divided into the rated limit short-circuit breaking capacity ICU and the rated operating short-circuit breaking capacity ICS.
The breaking capacity is 35KA, 50KA, 60KA, 80KA and other specifications, and the limit short-circuit capacity of domestic small circuit breakers is generally between 4-6KA, and the breaking reliability is not high.
If ICU = 50KA, then when the 50KA fault current occurs in the circuit, the circuit breaker can safely cut off the circuit without contact bonding, explosion, etc., but the circuit breaker that has been interrupted by the ultimate short circuit can not be used again.
If IUS = 50KA, when a 50KA fault current occurs, the circuit breaker can safely cut off the circuit, and it can be closed again when the fault is eliminated. Of course, it is best to replace the circuit breaker.
Is it the bigger the better?
An important principle for selecting a circuit breaker is that the ultimate short-circuit breaking capacity of the circuit breaker is greater than the expected short-circuit current of the line. No matter what kind of circuit breaker, its ultimate short-circuit breaking capacity is greater than or equal to its operating short-circuit breaking capacity.
Is the greater the breaking capacity of the circuit breaker the better? Of course.
The greater the breaking capacity, the higher the safety.
For example, when the ICU is selected as 35KA, if the short circuit current in the line is 20KA, it will be cut off in time; but if the ICU is 20KA, the short circuit current is 35KA and it cannot be disconnected. Although the greater the breaking capacity, the better, but the price will be higher. It is still necessary to economically select the appropriate circuit breaker based on its own use and on the premise of ensuring sufficient safety.