Working principle of circuit breaker

2024-11-06 10:44:11 格雷诺（厦门）开关有限公司

A circuit breaker is generally composed of a contact system, an arc extinguishing system, an operating mechanism, a release device, a housing, etc.
When there is a short circuit, the magnetic field generated by high current (usually 10 to 12 times) overcomes the reaction spring, and the release pulls the operating mechanism to act, causing the switch to trip instantly. When overloaded, the current increases, the heat generation intensifies, and the bimetallic strip deforms to a certain extent to push the mechanism to operate (the larger the current, the shorter the operation time).
There are electronic types that use transformers to collect the current magnitude of each phase, compare it with the set value, and when the current is abnormal, the microprocessor sends a signal to drive the electronic release to operate the operating mechanism.
The function of a circuit breaker is to cut off and connect load circuits, as well as to cut off faulty circuits, prevent accidents from escalating, and ensure safe operation. And the high-voltage circuit breaker needs to break the arc with a current of 1500-2000A at 1500V, which can be extended to 2m and continue to burn without extinguishing. Therefore, arc extinguishing is a problem that high-voltage circuit breakers must solve.
The principle of arc extinguishing by blowing is mainly to cool the arc and reduce thermal ionization. On the other hand, by blowing the arc to elongate the arc, the recombination and diffusion of charged particles are strengthened. At the same time, the charged particles in the arc gap are blown away, quickly restoring the insulation strength of the medium.
Low voltage circuit breakers, also known as automatic air switches, can be used to connect and disconnect load circuits, as well as 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, overcurrent relays, voltage loss relays, thermal relays, and leakage protectors. It is an important protective appliance in low-voltage distribution networks.
Low voltage circuit breakers have various protection functions (overload, short circuit, undervoltage protection, etc.), adjustable operating values, high breaking capacity, easy operation, safety and other advantages, so they are widely used. The structure and working principle of a low-voltage circuit breaker consist of an operating mechanism, contacts, protective devices (various release devices), arc extinguishing system, etc.
The main contact of the 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 release and the thermal element of the thermal release are connected in series with the main circuit, while the coil of the undervoltage release is connected in parallel with the power supply. When a short circuit or severe overload occurs in the circuit, the armature of the overcurrent release will engage, causing the free release mechanism to operate and the main contact to disconnect the main circuit. When the circuit is overloaded, the thermal element of the thermal release generates heat, causing the bimetallic strip to bend and pushing the free release mechanism to move. When the circuit is under voltage, the armature of the undervoltage release is released. Also enables the free release mechanism to operate.