We use air circuit breakers the most everyday, especially novice electricians, who don’t have a lot of contact with vacuum circuit breakers, or even heard of them. But when we look at it literally, if there is an air circuit breaker, there will naturally be a vacuum circuit breaker against it. What is the difference between this vacuum circuit breaker and an air circuit breaker? Today we will give a brief introduction.
The so-called "air" and "vacuum" originally referred to the different arc extinguishing devices. The air circuit breaker relies on the arc extinguishing device to stretch the arc, and then relies on air to cool the arc (what is an arc? Arc or spark). The vacuum circuit breaker relies on vacuum arc extinguishing, and there is a vacuum bubble inside.
This leads to the second difference. The air circuit breaker relies on compressed air to perform the opening or closing action. Due to its high vacuum characteristics, the vacuum circuit breaker cannot use the air storage chamber. Therefore, the vacuum circuit breaker relies on the electric valve and electromagnet to control the circuit. Opening and closing.
The detailed action process is:
The air storage cylinder must be filled with sufficient compressed air before the air circuit breaker is activated; the D cavity of the starting valve is filled with compressed air; and a small amount of compressed air enters the arc extinguishing chamber through the ventilation plug, main valve, and supporting porcelain bottle to keep the arc extinguishing chamber A certain positive pressure prevents the intrusion of external humid air. The vacuum circuit breaker does not require a special air storage cylinder. It is closed by an electro-pneumatic valve and an electromagnet. As long as the train runs normally, there will be sufficient air supply.
It can be seen that the internal structure of the vacuum circuit breaker is much simpler than that of the air circuit breaker, so the failure rate is lower and the service life is longer. Of course the price is much higher. Generally, vacuum circuit breakers are used in places with high voltage or special environment, because these places have higher requirements for arc extinguishing.
Finally, note that vacuum circuit breakers cannot be used in DC circuits at present.