Electrical safety must be used in the circuit accessories - circuit breaker. Circuit breaker is divided into high voltage circuit breaker and low voltage circuit breaker, both different applications, circuit breaker manufacturers today to give you several types of high and low voltage circuit breaker and the difference.
High voltage circuit breaker
1, high voltage circuit breaker (QF) -- short circuit, arc extinguishing, normal load
The high-voltage circuit breaker has a reliable arcing device, which has a strong arcing ability. When the circuit is working, it can be used to switch on or cut off the load current. When the circuit is faulty, it can prevent the accident from expanding and ensure the safe operation. Can also be used to cut off large short circuit current. High voltage circuit breaker to open 1500V, current of 1500-2000A arc, the arc can be stretched to 2m still continue to burn not extinguished. Therefore, arc extinguishing is a problem that high voltage circuit breaker must solve.
High voltage circuit breaker according to the different arc extinguishing medium can be divided into multi oil arc extinguishing circuit breaker, low oil circuit breaker, high voltage circuit breaker, vacuum circuit breaker, sulfur hexafluoride circuit breaker, magnetic blow circuit breaker, etc.
Several types of low-voltage circuit breakers
1, frame circuit breaker (universal) - ACB
In the rated current, in principle the rated current 630A heart requires the use of frame circuit breaker, molded case circuit breaker is generally 630A(some new products can reach 1600A) below. It can be seen that the rated current of the frame circuit breaker is much larger, generally 630A-6300A. In addition, frame circuit breakers are higher than MOLDED case circuit breakers in segment capacity.
In practical application, the circuit above 800A or the circuit with particularly high requirements for segmented capacity or the circuit with more functions should use the frame circuit breaker, and the circuit below 630A generally uses the molded case circuit breaker.
All parts of the frame circuit breaker are installed in an insulated metal frame, often open type, can be installed with a variety of accessories, replacement of contacts and components is more convenient, mostly in the power end of the main switch. There are several kinds of over current release, such as electromagnetic release, electronic release and intelligent release. The circuit breaker has four protection sections: long delay, short delay, instantaneous and ground fault, and the setting value of each protection is adjusted in a certain range according to the class of its shell frame.
2, Molded case circuit breaker -- MCCB
Can automatically cut off the current when the current exceeds the tripping setting. MCCBS usually contain thermal-magnetic trip units, but larger MCCBS may be equipped with solid-state trip sensors. The trip unit is divided into thermal magnetic trip and electronic trip.
Also referred to as a device circuit breaker because the outer contact of the ground wire terminal, the arcing chamber, the release, and the operating mechanism are housed in a plastic case. Auxiliary contact, undervoltage tripping device and shunt tripping device are modular, very compact structure, generally do not consider maintenance, suitable for the protection switch branch.
Its use of manual operation, large capacity can choose electric split. Due to the application of electronic over-current release, it can be divided into two types: class A and Class B. Class B has A good three-section protection characteristics, but because of the price factor, the market share of class A products using thermal magnetic release is higher.
Molded case circuit breaker is over current trip has electromagnetic and electronic two kinds, general electromagnetic molded case circuit breaker is non-selective circuit breaker, only long delay and instantaneous two kinds of protection, electronic molded case circuit breaker has long delay, short delay, instantaneous and ground fault four kinds of protection functions. Some new products of electronic MCCB also have the function of regional selective interlocking.
3, miniature circuit breaker - MCB
It is the most widely used terminal protection appliance in building electrical terminal distribution device. Used for single-phase, three-phase short-circuit, overload, over-voltage protection under 125A, including unipolar 1P, 2P, 3P, 4P and so on.
In the design of civil buildings, low-voltage circuit breakers are mainly used for overload, short circuit, over-current, voltage loss, undervoltage, grounding, leakage, automatic switching of double power supply and motor infrequent starting (9 kinds) protection, operation and other purposes.
The differences between the preceding circuit breakers
ACB- universal (frame type) circuit breaker, MCCB- molded case circuit breaker, MCB- miniature circuit breaker, ELCB- leakage circuit breaker is the main difference:
(1) The breaking ability of ACB is relatively high, MCCB is the second and MCB is the worst.
(2) the location of the installation, ACB are adopted as the main circuit breaker (power master switch), because it itself has the time delay function, can delay the breaker and tripping, but also has the very good communication function and selectivity, while MCCB was adopted as the power distribution electric, in the middle of the line, because it only has the capability of breaking and inverse time tripping ability, No selectivity, most can only be used as a subordinate protection switch, emergency stop switch HW; MCB is mostly used in the load side, because its breaking capacity is relatively lower than half of 6000A and 4500A;
(3) The external dimensions also vary greatly. MCB has small volume and convenient installation, while ACB has the largest volume and complicated installation, and MCCB is in the middle.