What is a vacuum circuit breaker? Working principle and application introduction.

Vacuum interrupter technology was first introduced in 1960. But it is still a developing technology. A circuit breaker is a device that cuts an electrical circuit to prevent an unreasonable current from being generated by a short circuit, usually caused by an overload. Its basic function is to interrupt the current flow after a fault is detected. This paper summarizes the vacuum circuit breaker and its working principle. To learn more about circuit breakers read this article about the types of circuit breakers and their importance.

What is a vacuum circuit breaker?

A vacuum circuit breaker is a circuit breaker quenching arc in a vacuum medium. The on-off, on-off, and associated arc breaking operations with current contacts are carried out in the vacuum chamber of the circuit breaker, known as the vacuum circuit breaker.

Vacuum as arc extinguishing medium in circuit breaker is called vacuum circuit breaker because the vacuum has superior arc extinguishing performance so that it has high insulation strength. This applies to most standard voltage applications, as for higher voltages, vacuum techniques are developed but are not commercially viable.

The operation of the current-carrying contact and the associated arc breaking occurs in the vacuum chamber of the breaker, known as the vacuum interrupter. The interrupter consists of a steel arc chamber at the center of asymmetrically placed ceramic insulator. Vacuum pressure maintenance in the vacuum interrupter can be done within 10-6 bar. The performance of a vacuum circuit breaker mainly depends on the material used for current-carrying contact, such as Cu/Cr.

Working principle of vacuum circuit breaker

The working principle of the vacuum circuit breaker is that once the circuit breaker contacts are interrupted in a vacuum, the contacts are ionized by the metal vapor in the contacts to generate an electric arc. However, due to the rapid condensation of electrons, ions and metal vapors generated in the arc outside the CB contact, the arc is easily quenched, so the dielectric strength can be quickly restored. The most important feature of a vacuum is that once an arc is generated in a vacuum, it can be extinguished quickly due to the rapid increase in the dielectric strength of the vacuum.


The arc extinguishing characteristic of the vacuum circuit breaker is different from other types of circuit breakers. The separation of the contact points results in the release of steam, which fills the contact space. It consists of positive ions released from the substance in contact. The vapor density depends on the current in the arc. When the current decreases, the vapor release rate decreases. After the current is zero, if the vapor density is reduced, the dielectric strength of the medium is restored.

When the interrupted current in the air is small, the arc has multiple parallel paths. The total current is divided into a number of parallel arcs that repel each other and spread across the contact surface. This is called a diffusion arc, and it can be easily interrupted.

At high current values, the arc is concentrated in a small area. It vaporizes the contact surface rapidly. Arc interruption is possible if the arc is still diffused. If it is quickly removed from the contact surface, the arc will be re-struck.

The arc extinguishing performance of vacuum circuit breaker is greatly affected by the contact material, shape and process considering metal vapor. The arc's path is constantly moving, so the temperature at any point is not very high.

After the final arc breaking, the dielectric strength of the vacuum circuit breaker increases rapidly, which is unique to the vacuum circuit breaker. They are suitable for capacitor switches because it will provide hammer - no performance. The small current interrupts before the natural current reaches zero, which can lead to chopping, the level of which depends on the material of the contact

Characteristics of vacuum circuit breakers

Compared with other types of circuit breakers, the insulation medium of vacuum circuit breaker has higher requirements on arc suppression performance. The pressure in the vacuum interrupter is about 10-4 for the flood, which includes very few molecules in the interrupter. This kind of circuit breaker basically has the following two special characteristics.

Compared with other insulating media used in circuit breaker, the circuit breaker is a superior medium. It is superior to other media except or SF6 and air because these are used at high pressure.

Once the arc is opened separately in a vacuum by moving the contact, a break occurs at the zero point of the main current. After the arc is cut off, its dielectric strength is more than 1000 times higher than other types of circuit breakers.

These features will make circuit breakers more proficient, lighter in weight and lower in cost. Compared to other circuit breakers, these circuit breakers have a long life and do not require any maintenance.

Application of vacuum circuit breaker

A vacuum circuit breaker is now recognized as the most reliable medium voltage switch current interruption technology. It requires minimal maintenance compared to other circuit breaker technologies.

The technology is mainly suitable for medium voltage applications. For high voltage vacuum technology has been developed, but it is not commercially feasible. Vacuum circuit breakers are used in metal-clad switchgear as well as porcelain-clad circuit breakers.

Professional vacuum circuit breaker supplier and manufacturer

Zhejiang JGGY Electrical Co.,Ltd (jggyelectrical.com), JGGY Electrical was established in 2007, specializing in the manufacture, sales and service of high-voltage electrical products. JGGY Electrical mainly specializes for 6~42kV medium voltage electric (outdoor and indoor): load break switch, disconnector, cutout fuse, surge arrester, vacuum circuit breaker.

Our technical expertise, comprehensive product portfolio and long-term rich experience are helping many customers in need to solve their power problems. We're happy to help at any time.  Whether you need application product advice or technical assistance, our global service team is committed to providing you with the right support. For more technical information about load break switch, feel free to contact us, send an email to sales@jggyelectrical.com.

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