A circuit breaker is a switching device capable of closing, carrying and breaking current under normal circuit conditions and capable of carrying and interrupting current under abnormal circuit conditions for a specified period of time. Circuit breaker according to its use is divided into high-voltage circuit breakers and low-voltage circuit breakers, high and low pressure line division is more fuzzy, generally more than 3kV called high-voltage electrical appliances.
Circuit breakers can be used to distribute power, not frequently start the asynchronous motor, the power lines and motors to protect, when they have a serious overload or short circuit and undervoltage problems such as failure to automatically cut off the circuit, its function is equivalent to fuse switch And a combination of overheat relays and the like. And generally do not need to change the parts after breaking the fault current. At present, has been widely used.
Electricity generation, transportation, use, distribution is an extremely important part. Power distribution system, including transformers and a variety of high and low voltage electrical equipment, low-voltage circuit breaker is a wide range of electrical appliances.
Circuit breakers generally by the contact system, arc system, operating mechanism, release, shell and other components.
When the short circuit, the high current (usually 10 to 12 times) to produce the magnetic field to overcome the reaction of the spring, the release device pull the operating mechanism, the switch instantaneous trip. When the overload, the current becomes larger, heat increased, bimetallic deformation to a certain extent to promote the action of the body (the greater the current, the shorter the action time).
There are electronic type, the use of the transformer to collect the current size of each phase, compared with the set value, when the current is abnormal when the microprocessor sends a signal, so that the electronic release device to drive the operating mechanism.
The role of the circuit breaker is to cut off and turn on the load circuit, and cut off the fault circuit to prevent the accident to expand and ensure safe operation. The high-voltage circuit breaker to break 1500V, current 1500-2000A of the arc, these arc can be extended to 2m still continue to burn does not go out. So the arc is high voltage circuit breaker must solve the problem.
The principle of blowing arc is mainly to cool the arc to reduce the heat dissipation, on the other hand through the arc of the arc to enhance the charge of the composite particles and diffusion, while the air gap in the charged particles blowing, the rapid recovery of dielectric dielectric strength.
Low-voltage circuit breakers, also known as automatic air switches, can be used to turn on and off the load circuit, can also be used to control the motor is not frequent start. It is equivalent to the knife switch, over-current relay, loss of stress relays, thermal relays and leakage protector and other electrical parts of the sum of all the functions of low-voltage distribution network is an important protection of electrical appliances.
Low-voltage circuit breaker with a variety of protection functions (overload, short circuit, under voltage protection, etc.), adjustable action value, breaking capacity, easy operation, security, etc., it is widely used. Structure and working principle Low-voltage circuit breaker by the operating mechanism, contacts, protection devices (a variety of release), arc system and other components.
Low-voltage circuit breaker main contact is by manual operation or electric closing. When the main contact is closed, the free trip 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 occurs short circuit or serious overload, the over-current release of the armature pull, so that the free trip mechanism, the main contact disconnect the main circuit. When the circuit is overloaded, the thermal element of the thermal release heats the bimetallic sheet to bend and push the free trip mechanism. When the circuit is undervoltage, the armature of the undervoltage release is released. Also let the free trip mechanism action. Shunt release is used as a remote control, in normal operation, the coil is power, in the need for distance control, press the start button to make the coil power.
The characteristics of the circuit breaker are: rated voltage Ue; rated current In; overload protection (Ir or Irth) and short circuit protection (Im) trip current setting range; rated short-circuit breaking current (industrial circuit breaker Icu; home circuit breaker Icn )Wait.
Circuit breaker wiring methods before the board, the board, plug-in, drawer, the user if no special requirements, are available according to board, board wiring is a common wiring.
1, board wiring: board wiring is the biggest feature is the replacement or maintenance of circuit breakers, do not have to re-wiring, only the front power supply disconnected. Because of the special structure, the product has been designed according to the design requirements of the special installation board and mounting screws and wiring screws, need special attention is due to the reliability of large-capacity circuit breaker contact will directly affect the normal use of circuit breakers, Must be taken seriously and strictly in accordance with the requirements of the manufacturer to install.
2, plug-in wiring: the installation of the installation device board, the first installation of a circuit breaker mount, the installation of six plugs, the circuit breaker connection board has six sockets. The mounting seat has a connecting plate or a mounting seat, and the mounting seat is pre-connected with the power cord and the load line. When used, insert the circuit breaker directly into the mounting seat. If the circuit breaker is broken, just pull out the bad, put a good can. It is the replacement time than the board, board wiring is short, and convenient. Due to plug, pull need a certain amount of manpower. So China's plug-in products, the shell current limit of up to 400A. Thus saving maintenance and replacement time. Plug-in circuit breakers should check whether the plug of the circuit breaker is tightened and the circuit breaker should be tightened safely to reduce the contact resistance and improve the reliability.
3, drawer wiring: the circuit breaker into and out of the drawer is clockwise or counterclockwise rotation, in the main circuit and the secondary circuit are used
Plug-in structure, omitting the necessary isolation of the fixed device, so that a machine with two, to improve the use of the economy, while the operation and maintenance has brought great convenience, increased security and reliability. In particular, the main drawer seat of the drawer seat can be used with the NT type fuse breaker.