How to select MCCB?

Plastic shell circuit breaker (plastic shell air insulated circuit breaker) is widely used in the low-voltage distribution industry, used to cut off or isolate the normal and rated range of fault current, to ensure the safety of lines and equipment.In addition, according to the requirements of China’s “Temporary Power Safety Technical Specification”, the temporary power circuit breaker on the construction site must be transparent shell, can clearly distinguish the main contact state, and the compliance circuit breaker must be affixed with the “AJ” mark issued by the relevant safety department.

QF is generally used to represent the circuit breaker, and foreign drawings are generally referred to as MCCB.Common plastic shell circuit breaker tripping methods are single magnetic tripping, hot magnetic tripping (double tripping), electronic tripping.Single magnetic tripping means that the circuit breaker only trips when the circuit has a short circuit failure, and we usually use this switch in the heater loop or the motor circuit with overload protection function.Thermal magnetic tripping is a line short circuit failure or circuit current for a long time exceeds the rated current of the circuit breaker to trip, so it is also known as double tripping, often used in ordinary power distribution occasions.Electronic tripping is a mature technology emerging in recent years, with electronic tripping circuit breaker magnetic tripping current, hot tripping current, and tripping time are adjustable, more widely applicable occasions, but the cost of circuit breaker is high.In addition to the above three types of tripping devices, moreover, there is a circuit breaker specially used for motor circuit protection. Its magnetic tripping current is generally above 10 times the rated current to avoid the peak current when the motor starts and ensure that the motor starts smoothly and the circuit breaker does not move.

Plastic shell circuit breaker has a variety of accessories can be hung, such as remote electric operation switch mechanism, excitation coil, auxiliary contact, alarm contact, etc.

When selecting the electric operation mechanism, attention should be paid to the supporting circuit breaker housing frame current, because the external size of different shell frame current circuit breaker and the torque of the closing mechanism are different.