Working Principle of Circuit Breaker

Circuit breaker is generally composed of contact system, arc extinguishing system, operating mechanism, decoupler, housing, etc.

When short-circuiting, the magnetic field generated by the high current (generally 10 to 12 times) overcomes the counterforce spring, the decoupler pulls the operating mechanism into action and the switch trips instantaneously. When overloaded, the current becomes large, heat generation increases, and the bimetal is deformed to a certain degree to push the mechanism into action (the larger the current, the shorter the action time).

There are electronic types, using mutual inductors to collect the current size of each phase, compare with the set value, and when the current is abnormal the microprocessor sends a signal to make the electronic decoupling drive the operation mechanism.

The role of the circuit breaker is to cut off and connect the load circuit, as well as cut off the fault circuit to prevent the expansion of the accident and ensure safe operation. The high-voltage circuit breaker to open 1500V, the current of 1500-2000A arc, these arcs can be stretched to 2m still continue to burn without extinguishing. Therefore, arc extinguishing is a high-voltage circuit breaker must be solved.

The principle of blowing arc extinguishing is mainly to cool the arc to weaken the heat free, on the other hand, by blowing arc elongation arc to strengthen the composite and diffusion of charged particles, while blowing the charged particles in the arc gap, and quickly restore the dielectric strength of insulation.

Low-voltage circuit breakers, also known as automatic air switches, can be used to turn on and off the load circuit, but also can be used to control infrequent starting of the motor. Its function is equivalent to the sum of some or all of the functions of the gate switch, overcurrent relay, loss of voltage relay, thermal relay and leakage protector and other electrical appliances, is an important protection appliance in the low-voltage distribution network.

Low-voltage circuit breaker has various protection functions (overload, short-circuit, under-voltage protection, etc.), adjustable action value, high breaking capacity, easy operation and safety, so it is widely used. Structure and working principle of low-voltage circuit breaker consists of operating mechanism, contacts, protection devices (a variety of decouplers), arc extinguishing system, etc.

The main contact of low-voltage circuit breaker is manually operated or electrically closed. After the main contact is closed, the free release mechanism locks the main contact in the closed position. The coil of the overcurrent derailer and the thermal element of the thermal derailer are connected in series with the main circuit, and the coil of the undervoltage derailer is connected in parallel with the power supply. When the circuit is short-circuited or severely overloaded, the armature of the overcurrent derailleur attracts, making the free derailleur mechanism act, and the main contact disconnects the main circuit. When the circuit is overloaded, the thermal element of the thermal decoupler heats up to bend the bimetal and push the free decoupling mechanism into action. When the circuit is under-voltage, the armature of the under-voltage detonator is released. Also make the free decoupling mechanism action. The shunt release is used as a long-distance control, in normal operation, its coil is disconnected, in need of distance control, press the start button to energize the coil.


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