The difference between an air circuit breaker and a normal one
First, a key concept needs to be made clear: an air circuit breaker is a kind of circuit breaker, not something parallel to a circuit breaker, but a member of the circuit breaker family. Ordinary circuit breakers generally refer to other types of air circuit breakers, such as vacuum circuit breakers, SF6 circuit breakers, oil circuit breakers, etc. Therefore, the essential difference between the two is "circuit breakers using air to extinguish arc" and "circuit breaker using other media to extinguish arc".
I. Core differences: Different Arc-Extinguishing Media
Air Circuit Breaker: As the name implies, it uses air as an arc extinguishing and insulation medium. arc created when the contact is separated is separated, cooled, and extinguished through the arc in the air. Its structure is simple, entirely dependent on air itself.
Ordinary Circuit Breaker (Non-Air Type): arc extinguishing medium is not air, but vacuum, sulphur hexafluoride gas or insulating oil. For example, vacuum circuit breakers are arc extinguished in a vacuum, SF6 circuit breakers arc extinguished with SF6 gas and oil transformers are arc extinguished with oil. The arc quenching properties of these media far exceed those of air, allowing them to handle higher voltages and currents.
ii. Completely Different Voltage Levels and their Applicable Scenarios
There are two types of air circuit breakers:
The first category is low-voltage air circuit breaker, commonly known as an "air switch" (MCB miniature circuit breaker, MCCB molded case circuit breaker, ACB frame circuit breaker). Rated voltage is usually between 380V and 690V, and rated current ranges from a few amperes to several thousand amperes. Small switches in domestic distribution boxes and large switches in a factory's distribution cabinet cabinets are both of these types. It has the advantages of simple structure, low price, easy maintenance and so on, and is the absolute main force in the field of low voltage.
The second is a high-voltage compressed air circuit breaker, which uses compressed air (0.4–6 MPa) as an arc extinguishing and insulation medium, and even compressed air as a power source. This type of circuit breaker, once used in high voltage systems of 110 kV and above, has a high short-circuit capacity, fast operation speed and no fire hazard. However, due to the complexity of the need for a complete compressed air system, it has been largely replaced by SF6 circuit breakers in systems of 110 kV and above.
What are the main applications of common circuit breakers (non-air type)?
Vacuum circuit breakers, with their small size, light weight, excellent maintenance and breakage performance, are currently the absolute mainstream of 35 kV and below. SF6 circuit breakers is the king in the 110kV~500kV high-voltage field, with the strongest insulation and arc extinguishing performance, small footprint and long maintenance cycle. Oil circuit breakers (high and low in oil) are still used in some older 35kV outdoor systems but are being phased out.
III. Performance Comparison: What are the advantages and disadvantages of an air circuit breakers?
Advantages of air circuit breakers:
The simplest structure, with no vacuum bulb, no SF6 gas and no oil, costs the least. Prices for low-voltage air circuit breakers range from a few dollars to several thousand dollars. Arc extinguishing medium is air, it does not cause fire, explosion or pollution, it is very safe. Their breakability is ideal for low voltage applications (4.5kA to 100kA) and no replacement parts are needed in the event of failure; they can be reset and reused.
Weaknesses of air circuit breakers:
Limited arc extinguishing ability, limited voltage levels. Low-voltage air breakers typically have a crushing capacity of 4.5kA to 10kA, vacuum circuit breakers can have a crushing capacity of dozens of kA, and SF6 circuit breakers can have a crushing capacity of dozens or even hundreds of kA. In high voltage application, air circuit breakers has been phased out because the insulation and arc extinguishing performance of air cannot withstand high voltage.
Advantages of a traditional circuit breakers (vacuum/SF6):
Arc-extinguishing properties far exceed air. Vacuum circuit breakers are the mainstream option at 35kV and below, while SF6 circuit breakers are the only option above 110kV. It has the characteristics of large breaking ability, fast running speed and high frequency operation. Vacuum circuit breakers are especially suitable for frequent switching, such as substation operations.
Weaknesses of traditional circuit breakers:
High costs. Vacuum circuit breakers are significantly more expensive than air circuit breakers, and SF6 circuit breakers are even more expensive. In addition, SF6 gas require regular testing and are therefore expensive to maintain. Oil circuit breakers are also at risk of fire and explosion.
IV. INTRODUCTION An air circuit breaker is the "simplest, cheapest, and safest" type in the family of circuit breakers, designed for low-pressure environments. Vacuum circuit breakers and SF6 circuit breakers are considered "traditional circuit breakers" and are "more powerful, expensive and professional" types designed for medium and high voltage and high current situations. They are not substitutes for each other; rather, they each serve their own domain-air circuit breakers are sufficient for your distribution box, and the SF6 circuit breakers are necessary for substations. If you must understand the difference, keep in mind that arc extinguishing media define their domains-low pressure, vacuum and high pressure SF6.
