A circuit breaker is a switching device that can close, load, and open the current in a normal loop condition and hold and break the abnormal circuit in a specified time. The circuit breaker can be divided into high voltage circuit breaker and low voltage circuit breaker according to its use range.
Circuit breaker can be used to allocate electricity, not frequent start asynchronous motor, the protection of power line and motor, when they happen serious overload or short circuit and under-voltage fault can automatically cut off the circuit, its function is equivalent to fuse switch to owe the combination of thermal relay, etc. Moreover, the parts should not be changed after breaking the current. At present, it has been widely used.
Distribution is an extremely important link in the generation, delivery and use of electricity. The distribution system includes transformers and various high and low voltage electrical equipment, and the low voltage circuit breaker is a widely used electric appliance.
The circuit breaker is composed of contact system, arc extinguishing system, operating mechanism, tripping device and shell.
When short circuit, the magnetic field generated by the large current (usually 10 to 12 times) overcomes the anti-force spring, the tripping device pulls the operating mechanism action, and the switch is instantaneous trip. When overloaded, the current becomes larger, the heat is increased, and the deformation of the bimetal plate is to a certain degree to promote the movement of the body (the larger the current is, the shorter the action time is).
With the electronic type, the size of each phase current is collected by means of the transformer. Compared with the set value, the microprocessor sends out the signal when the current is abnormal, so that the electronic tripping device drives the operation mechanism.
The function of the circuit breaker is to cut off and connect the load circuit, and to cut off the fault circuit to prevent the accident from expanding and ensure the safe operation. The high voltage circuit breaker will open 1500V and the current will be 1500-2000a. The arc can be extended to 2m and continue to burn. So the arc suppression is the problem that the high voltage circuit breaker must solve.
Blow the principle of arc arc mainly cooling arc thermal dissociation, on the other hand stretched by blowing arc arc strengthen composite and diffusion of charged particles, the charged particles in the arc gap blows away at the same time, quickly recover dielectric strength of the medium.
Low-voltage circuit breakers, also known as automatic air switches, can be used to plug and break the load circuit, or to control the motor that does not start frequently. Its function is equal to the knife switch, over-current relay, relay, thermal relay, pressure loss and leakage protector electrical part or all of the functions such as sum, it is a kind of important in the low voltage distribution network protection appliances.
Low voltage circuit breaker has many advantages such as protection function (overload, short circuit, undervoltage protection, etc.), adjustable action value, high breaking ability, convenient operation and safety, so it is widely used. The structure and working principle low voltage circuit breaker consists of operating mechanism, contact, protection device (various kinds of tripping device), and arc extinguishing system.
The main contact of the low voltage circuit breaker is operated by hand or electric switchgear. After the main contact is closed, the free trip mechanism locks the main contact lock in the lock position. The coil of the overcurrent tripping device and the thermal element of the thermal release are in series with the main circuit, and the coil of the undervoltage trip is connected in parallel with the power supply. When the circuit is short circuited or seriously overloaded, the armature of the overcurrent tripping device is absorbed and the free tripping mechanism is made, and the main contact is disconnected from the main circuit. When the circuit is overloaded, the heat element of the thermostat causes the bimetal to bend and move the free trip mechanism. When the circuit is under voltage, the arrester of the undervoltage release is released. Also make free trip mechanism action. The shunt tripping device is used as a remote control. When working normally, its coil is without power, and when it needs distance control, press the start button to make the coil energize.
The wiring mode of the circuit breaker is in front, plate, insert and drawer type. The user can supply the goods without special requirements. The front wiring of the circuit is a common connection mode.
1. Post-plate wiring: the most characteristic of the post-panel wiring is that the circuit breaker can be replaced or maintained without rewiring, only the front power supply is disconnected. Due to the special structure, when the product leaves the factory, according to the requirements of design has been configured with a special installation plate and screw, screw connection, need special attention is due to the large capacity of circuit breaker contact reliability will directly affect the normal use of circuit breaker, so must be attention when installation, strictly according to the requirements of manufacturing plant for installation.
2. Insert wiring: on the mounting plate of the complete set, install a circuit breaker installation seat, and install 6 plugs on the socket. The circuit breaker has 6 sockets on the connection plate. The mounting pedestal has a connection plate or a bolt after the mounting seat, and the mounting seat is pre-connected with the power line and load line. When used, insert the circuit breaker directly into the mounting seat. If the circuit breaker is broken, just pull out the bad and replace it with a good one. Its replacement time is shorter than the plate, and the wiring is short and convenient. It takes a certain amount of manpower to plug and pull. Therefore, China's plug-in products have the maximum current limit of 400A. This saves maintenance and replacement time. Insert circuit breaker should check whether the plug of the circuit breaker is pressed tightly during installation, and the circuit breaker should be securely fastened to reduce contact resistance and improve reliability.
3. Drawer type wiring: the entry and exit drawers of the circuit breaker are rotated clockwise or anticlockwise by the rocker, and are adopted in the main circuit and secondary loop
Insert structure, omitted the stationary isolator, necessary to accomplish one machine with two, improve the economic benefit of the use, at the same time to make a lot of convenient for operation and maintenance, increases the security and reliability. In particular, the main loop of the drawer is used to contact the blade holder.