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How Circuit Breakers Work_Chengyang Electric

The circuit breaker is generally composed of contact system, arc extinguishing system, operating mechanism, release, shell, etc.

In case of short circuit, the magnetic field generated by high current (generally 10-12 times) overcomes the reaction spring, the release pulls the operating mechanism to act, and the switch trips instantaneously. When the overload occurs, the current becomes larger, the heat generation is intensified, and the bimetallic sheet deforms to a certain extent to push the mechanism action (the greater the current, the shorter the action time).

If there is electronic type, use mutual inductor to collect the current of each phase, and compare with the set value. When the current is abnormal, the microprocessor will send a signal to make the electronic release drive the operation mechanism.

The function of the circuit breaker is to cut off and connect the load circuit and cut off the fault circuit, so as to prevent the accident from expanding and ensure the safe operation. The high-voltage circuit breaker needs to break 1500V and 1500-2000a arc, which can be stretched to 2M and still burn continuously. Therefore, arc extinguishing is a problem that must be solved for high voltage circuit breakers.

The main principle of arc blowing and extinguishing is to cool the arc and reduce the thermal dissociation. On the other hand, the arc is extended by arc blowing to strengthen 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.

Low voltage circuit breakers, also known as automatic air switches, can be used to turn on and off load circuits, or to control infrequent starting motors. Its function is equal to the sum of some or all functions of knife switch, over-current relay, voltage loss relay, thermal relay, leakage protector and other electrical appliances, and it is an important protective electrical appliance in low-voltage distribution network.

Low voltage circuit breaker is widely used because of its many protection functions (overload, short circuit, undervoltage protection, etc.), adjustable action value, high breaking capacity, convenient operation and safety. Structure and working principle the low-voltage circuit breaker is composed of operating mechanism, contact, protection device (various releases), arc extinguishing system, etc.

The main contact of LV circuit breaker is closed by manual operation or electric operation. 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 and the power supply are connected in parallel. When the circuit is short circuited or seriously overloaded, the armature of the over-current release is engaged to make the free release mechanism act and the main contact opens the main circuit. When the circuit is overloaded, the thermal element of the thermal release causes the bimetallic sheet to bend and push the free release mechanism to act. When the circuit is under voltage, the armature of the under voltage release is released. It also makes the free tripping mechanism act. The shunt release is used for remote control. In normal operation, its coil is de energized. When distance control is required, press the start button to make the coil energized.

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