The working principle of ACB circuit breaker

Promulgator : TAIXIDate : 2018-11-21Views : 201

ACB circuit breaker is a kind of switching device which can turn on, load and break the current in normal circuit and can turn on, load and break the current in abnormal circuit within a specified time. Circuit breakers are divided into high-voltage circuit breakers and low-voltage circuit breakers according to their application scope. The demarcation line between high-voltage and low-voltage is relatively vague. Generally, more than 3kV is called high-voltage electrical appliances. Circuit breakers can be used to distribute electric energy, start asynchronous motors infrequently, and protect power lines and motors. When they have serious overload or short circuit and undervoltage faults, they can automatically cut off the circuit. Their functions are equivalent to the combination of fuse switches and overheating relays. And after breaking the fault current, there is no need to change parts. At present, it has been widely applied.

Distribution is a very important link in the generation, transmission and use of electricity. Distribution system includes transformer and various high and low voltage electrical equipment. Low voltage circuit breaker is a kind of widely used electrical equipment.

Working principle

ACB circuit breaker is generally made up of contact system, arc extinguishing system, operation mechanism, release, shell and so on.

When short circuit occurs, the magnetic field generated by high current (usually 10 to 12 times) overcomes the reaction spring, the release pulls the operation mechanism to move, and the switch trips instantaneously. When overload occurs, electrorheological (ER) becomes larger and calorific value increases, and bimetal sheets deform to a certain extent to promote the action of the mechanism (the greater the current, the shorter the action time).

With electronic type, the current of each phase is collected by transformer and compared with the set value. When the current is abnormal, the microprocessor sends out a signal, which makes the electronic tripper drive the operation mechanism.

The function of ACB 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 should break 1500V arcs with current of 1500-2000A. These arcs can be extended to 2M and still keep burning and not extinguishing. Therefore, arc extinguishing is a problem that must be solved by high voltage circuit breaker.

The principle of arc extinguishing by arc blowing is mainly to reduce thermal dissociation of cooling arc, on the other hand, to strengthen the composition and diffusion of charged particles by arc blowing and elongating arc, at the same time, to disperse charged particles in the arc gap and quickly restore the dielectric insulation strength.

LV circuit breaker, also known as automatic air switches, can be used to turn on and break load circuits, or to control motors that do not start frequently. It is an important protective device in low-voltage distribution network. Its function is equivalent to the sum of some or all functions of switch, over-current relay, Voltage-loss relay, thermal relay and leakage protector.

LV circuit breaker has many protection functions (overload, short circuit, under-voltage protection, etc.), adjustable action value, high interruption ability, easy operation, safety and other advantages, so it is widely used. The structure and working principle of low-voltage circuit breaker are composed of operating mechanism, contacts, protective devices (various trippers), arc extinguishing system, etc.

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 tripper is sucked, which makes the free tripping mechanism act and the main contact disconnects the main circuit. When the circuit is overloaded, the heat element of the thermal release makes the bimetal sheet bend and pushes the free release mechanism to move. When the circuit is under voltage, the armature of the undervoltage release is released. It also enables the free tripping mechanism to act. Excitation tripper is used as long-distance control. In normal operation, its coil is cut off. When distance control is needed, the start button is pressed to make the coil energized.