What is the circuit breaker and what is its working principle?

Promulgator : TAIXIDate : 2018-10-11Views : 216

Circuit breaker is a switching device which can close, load and break the current under the condition of normal circuit, and can close, load and break the current under the condition of abnormal circuit within a specified time. Household circuit breaker is generally made up of contact system, arc extinguishing system, operation mechanism, release, shell and so on. Circuit breakers are divided into high-voltage circuit breakers and low-voltage circuit breakers according to their scope of use. The dividing line between high and low voltage is blurred. Generally, circuit breakers above 3KV are called high-voltage electrical appliances.

Definition of low voltage circuit breaker
Low-voltage circuit breaker is a kind of distribution apparatus used in low-voltage power network [AC 50Hz or 60Hz, rated voltage below 120V, DC rated voltage below 1200V]. For its purpose, lv circuit breaker is defined as switching appliances capable of switching on, carrying and disconnecting current under normal circuit conditions, or switching on, carrying a certain time and disconnecting current under specified abnormal conditions (such as overload, short circuit, under-voltage and single-phase earth fault). In the past, it was also called automatic switch, air switch and air circuit breaker.

Working principle of low voltage circuit breaker:
The working principle of lv circuit breaker: low-voltage circuit breaker has a variety of protection functions (overload, short circuit, under-voltage protection, etc.), adjustable operation value, high breaking capacity, easy operation, safety and other advantages, so it is widely used.
The main contacts of lv circuit breaker are operated by manual operation or by electric switching. After the main contact is closed, the free tripping mechanism locks the main contact on the closing position. The coil of the overcurrent release and the thermal element of the thermal release are in series with the main circuit, and the coil and the power supply of the undervoltage release are in parallel. When the circuit is short-circuited or seriously overloaded, the armature of the over-current release closes and the free release mechanism acts, and the main contact disconnects the main circuit. When the circuit is overloaded, the heat element of the thermal release causes the bimetal sheet to bend and pushes the free release mechanism to move. When the circuit is under voltage, the armature of the undervoltage release is released. Household circuit breaker also enables the free tripping mechanism to act. Split-excitation tripper is used for long-distance control. In normal operation, its coil is power-off. When distance control is needed, press the start button to make the coil energized and the armature drives the free tripping mechanism to disconnect the main contact.

Function of low voltage circuit breaker
Low-voltage circuit breaker is one of the main switching devices in low-voltage distribution network. Household circuit breaker can not only switch on and off normal load current, motor working current and overload current, but also switch on and off short-circuit current. It can be used to distribute electric energy, start asynchronous motors infrequently, protect power lines and motors, and cut off circuits automatically when they have serious overload or short circuit and undervoltage faults. Its function is equivalent to the combination of fuse switches and overheating relays. And after breaking the fault current, there is no need to change parts, so it has been widely applied. Mainly used as power switches in low-voltage distribution lines or switchgear cabinets (boxes) which are not frequently operated, and play a protective role in lines, electrical equipment and motors, when they occur serious overcurrent, overload, short circuit, phase break, leakage and other faults, they can automatically cut off the line, play a protective role.