How to choose miniature circuit breakers C and D

The miniature circuit breaker used for motor starting should be D-type, the C-type is used for power distribution control and lighting, and the D-type is larger than the C-type short-circuit segmentation multiple, such as the rated 32A switch, D short circuit The segment capacity is about 7-10 times the rated value, and C is about 4-7 times.

The small size is easy to use and flexible, and the wide range of applications are in the power system. The miniature circuit breaker has short-circuit protection (electromagnetic trip) overload protection (bimetal thermal trip). Miniature circuit breakers are equipped with leakage tripping accessories to form our most common leakage protector. Common types of miniature circuit breakers are Type C and Type D.

Protection principle Short-circuit protection: When the line is short-circuited, the short-circuit current is very large. The electromagnetic force of the electromagnetic coil is used to drive the iron core inside the coil to push the push rod, and the push rod is opened to unlock the lock, and the breaking function time is less than or equal to 0.1 second. Overload protection: When the line has an overload fault, the current exceeds the rated current and is less than the set short-circuit current value. The overload current bends the hot bimetal element and pushes the lock, thereby realizing the function of the breaker. The time varies according to the current. The corresponding delay.

Type C and D type difference

The difference between the C type and the D type is the difference in the instantaneous trip current of the short circuit, and the overload protection is the same.

Type C: The magnetic trip current is (5-10) In, which means that the trip occurs when the current is 10 times the rated current, and the action time is less than or equal to 0.1 second. Suitable for protecting conventional loads and lighting lines. (Households are mostly C type)

Type D: The magnetic trip current is (10-20) In, which means that when the current is 20 times the rated current, the trip time is less than or equal to 0.1 second. It is suitable for protecting equipment with high inrush current, starting a load with a large current, like a small motor that is directly started.