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The working principle of circuit breaker

Jan 08, 2019

Circuit breaker is generally composed of contact system, arc extinguishing system, operating mechanism, tripping device, housing and so on.

When short circuit, large current (generally 10 to 12 times) generated by the magnetic field to overcome the reaction spring, release pull operating mechanism action, switch instantaneous trip. When overload occurs, the current becomes larger and the calorific value increases, and the deformation of the bimetal sheet to a certain extent pushes the mechanism to move (the higher the current, the shorter the action time).

If there is an electronic type, use the transformer to collect the current of each phase and compare it with the set value. When the current is abnormal, the microprocessor will send out a signal to make the electronic tripping device drive the operation mechanism.

The function of circuit breaker is to cut off and put through the load circuit, and cut off the fault circuit, to prevent the expansion of the accident, to ensure safe operation. The high voltage circuit breaker to break 1500V, current of 1500-2000a arc, these arc can be elongated to 2m still continues to burn. Therefore, arc extinguishing is a problem that must be solved for high voltage circuit breaker.

The principle of blowing arc extinguishing is to cool the arc to weaken thermal disconnection, on the other hand, extend the arc by blowing arc to strengthen the recombination and diffusion of charged particles, and at the same time blow away the charged particles in the arc gap to quickly restore the insulation strength of the medium.

Low-voltage circuit breakers, also known as automatic air switches, can be used to switch on and off load circuits or to control infrequently started motors. It is equivalent to the function of knife switch, over current relay, voltage loss relay, thermal relay and leakage protector and other electrical parts or all of the sum, is an important protection of low-voltage distribution network electrical appliances.

Low voltage circuit breaker has a variety of protection functions (overload, short circuit, under voltage protection, etc.), adjustable action value, high breaking capacity, convenient operation, safety and other advantages, so it is widely used. Structure and working principle low-voltage circuit breaker is composed of operating mechanism, contact, protection device (all kinds of tripping devices), arcing system, etc.

The main contact of the low voltage circuit breaker is manually operated or electrically operated. After the main contact is closed, the free tripping mechanism locks the main contact in the closing position. The coil of the over-current tripping device and the thermal element of the thermal tripping device are connected in series with the main circuit, and the coil of the under-voltage tripping device is connected in parallel with the power supply. When the circuit short circuit or serious overload occurs, the armature of the over-current tripping device is absorbed to make the free tripping mechanism operate and the main contact is disconnected from the main circuit. When the circuit is overloaded, the thermal element of the thermal tripping device heats up, causing the bimetallic sheet to bend and pushing the free tripping mechanism into action. The armature of the under-voltage release is released when the circuit undervoltage is applied. Also causes the free trip mechanism to act. Shunt trip is used as remote control. In normal operation, the coil is power off. When distance control is needed, press the start button to energize the coil.