How Circuit Breaker Works

A circuit breaker is generally composed of a contact system, an arc extinguishing system, an operating mechanism, a release, and a shell.
When there is a short circuit, the magnetic field generated by the large current (generally 10 to 12 times) overcomes the reaction spring, the release pulls the operating mechanism, and the switch trips instantly. When overloaded, the current becomes larger, the heat generation intensifies, and the bimetallic sheet deforms to a certain extent to promote the action of the mechanism (the greater the current, the shorter the action time).
There is an electronic type, which uses a transformer to collect the current of each phase and compares it with the set value. When the current is abnormal, the microprocessor sends a signal, causing the electronic tripper to drive the operating mechanism.
The function of the circuit breaker is to cut off and connect the load circuit, and cut off the fault circuit to prevent the accident from expanding and ensure safe operation. The high-voltage circuit breaker needs to break 1500V arcs with a current of 1500-2000A. These arcs can be stretched to 2m and still continue to burn without being extinguished. Therefore, arc extinguishing is a problem that high-voltage circuit breakers must solve.
The principle of arc blowing and arc extinguishing is mainly to cool the arc and weaken the heat dissipation. On the other hand, the arc blowing is used to lengthen the arc to enhance the recombination and diffusion of charged particles. At the same time, the charged particles in the arc gap are blown away to quickly restore the dielectric strength of the medium.
Low-voltage circuit breaker, also known as automatic air switch, can be used to connect and break load circuits, and can also be used to control motors that start infrequently. Its function is equivalent to the sum of the functions of some or all electrical appliances such as knife switches, over-current relays, voltage-loss relays, thermal relays and leakage protectors. It is an important protective electrical appliance in low-voltage distribution networks.
Low-voltage circuit breakers have a variety of protection functions (overload, short circuit, undervoltage protection, etc.), adjustable operating values, high breaking capacity, easy operation, safety, etc., so they are widely used. Structure and working principle The low-voltage circuit breaker is composed of operating mechanism, contacts, protection devices (various releases), arc extinguishing system, etc.
The main contacts of the low-voltage circuit breaker are closed manually or electrically. After the main contact is closed, the free tripping mechanism locks the main contact in the closing position. The coil of the overcurrent release and the thermal element of the thermal release are connected in series with the main circuit, and the coil of the undervoltage release is connected in parallel with the power supply. When a short circuit or serious overload occurs in the circuit, the armature of the overcurrent release is attracted, causing the free tripping mechanism to operate, and the main contact disconnects the main circuit. When the circuit is overloaded, the thermal element of the thermal tripper heats up and bends the bimetallic piece, pushing the free tripping mechanism into action. When the circuit is under-voltage, the armature of the under-voltage release is released. It also activates the free tripping mechanism. The shunt tripper is used for long-distance control. During normal operation, its coil is de-energized. When distance control is required, press the start button to energize the coil.