What is the difference between C-type and D-type of miniature circuit breakers? How to choose them?

Promulgator : TAIXIDate : 2018-08-13Views : 119

Miniature circuit breakers used for motor startup should be type D, type C for distribution control and lighting, type D for short-circuit segment multiple larger than type C, such as rated 32A switch, D short-circuit segment capacity is about 7-10 times rated, C is about 4-7 times.

Small size, easy installation, flexible use, widely used in power system. 63 amp mcb with short circuit protection (electromagnetic release) overload protection (bimetal thermal release). The household circuit breaker is equipped with the leakage tripping attachment to form our most common leakage protector. Small circuit breakers are commonly C and D.

Principle of Short Circuit Protection: When the circuit has short circuit fault, short circuit current is very large, the use of electromagnetic coil to drive the iron core in the coil to push the push rod, push rod to unlock the lock, to achieve breaking function of less than or equal to 0.1 seconds.

Overload protection: when the line overload fault occurs, the current exceeds the rated current and is less than the set short-circuit current value. The overload current causes the thermal bimetal element to bend and push the lock, thus realizing the function of the circuit breaker. The time has corresponding delay according to the current size.

The difference between type C and type D

The difference between type C and type D of 63 amp mcb is that the instantaneous tripping current is different, and the overload protection is the same.

Type C: The magnetic trip current is (5-10) In, which means that when the current is 10 times the rated current, the trip time is less than or equal to 0.1 seconds. It is applied to protect conventional loads and lighting lines. (all households use 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 seconds. It is suitable for protecting equipment with high impulse current, starting load with large current, such as direct starting small motor.

Circuit breaker is a switching device which can close, load and break the current under normal circuit conditions, and can carry and break the current under abnormal circuit conditions (including short circuit conditions) within a specified time. Circuit breakers can be used to distribute electric energy, start asynchronous motors infrequently, protect power lines and motors, and automatically cut off circuits when they have serious overload or short-circuit or under-voltage faults. Their functions are equivalent to the combination of fuse switches and over-heated relays. And after breaking the fault current, there is no need to change parts. At present, it has been widely applied.

The 63 amp mcb is generally composed of contact system, arc extinguishing system, operating mechanism, tripper, shell, etc. Circuit breakers are divided into miniature circuit breakers, moulded case circuit breakers and frame type circuit breakers according to their structures.

Function of circuit breaker

Cut off and connect the load circuit, and cut off the fault circuit, prevent the accident from expanding, ensure the safe operation. The high-voltage circuit breaker to break 1500V, current 1500-2000A arcs, these arcs can be extended to 2m still burning non-extinguishing. Therefore, arc extinguishing is a problem that must be solved by high voltage circuit breaker.

Low-voltage household circuit breaker, also known as automatic air switches, can be used to switch on and off the load circuit, but also can be used to control the motor starting infrequently. Its function is equivalent to the sum of some or all of the functions of the switch, overcurrent relay, Voltage-loss relay, thermal relay and leakage protector. It is an important protective device in low-voltage distribution network.

Low-voltage household circuit breaker has a variety of protection functions (overload, short circuit, under-voltage protection, etc.), adjustable operating value, high breaking capacity, easy operation, safety and other advantages, so it is widely used. The structure and working principle of low voltage circuit breaker are composed of operating mechanism, contacts, protective devices (various release devices), arc extinguishing system, etc.