Vacuum Circuit Breaker (VCB) - Principle, Construction and Working

Welcome To System Protection

www.systemprotection.in

About Us Ensuring a constant blood flow in your body is the doctors’ job, ensuring a constant power supply to your industrial plants is ours. And we take our job seriously. We at System Protection are a team of experienced and enthusiastic professionals who ensure that your operations are safe, economic and efficient. Our core expertise lies in performing vital and reliable field services in the areas of Electrical Testing, Commissioning, Maintenance and Consulting. A brief overview of our diverse set of services is as below :

www.systemprotection.in

Vacuum Circuit Breaker (VCB) - Principle, Construction and Working

www.systemprotection.in

In vacuum circuit breakers, vacuum is used as the arc quenching medium.

Vacuum offers the highest insulating strength. So it has far superior arc quenching properties than any other medium.

www.systemprotection.in

For example, when contacts of a breaker are opened in vacuum, the interruption occurs at first current zero with dielectric strength between the contacts building up at a rate thousands of times higher than that obtained with other circuit breakers.

www.systemprotection.in

The technology is suitable for mainly medium voltage application. For higher voltage vacuum technology has been developed but not commercially viable.

www.systemprotection.in

Principle of Vacuum Circuit Breaker

www.systemprotection.in

The production of arc in a vacuum circuit breaker and its extinction can be explained as follows :

www.systemprotection.in

• The salient feature of vacuum as an arc quenching medium is that as soon as the arc is produced in vacuum, it is quickly extinguished due to the fast rate of recovery of dielectric strength in vacuum.

www.systemprotection.in

Construction of Vacuum Circuit Breaker

www.systemprotection.in

• The movable member is connected to the control mechanism by stainless steel bellows. This enables the permanent sealing of the vacuum chamber so as to eliminate the possibility of leak.

www.systemprotection.in

• A glass vessel or ceramic vessel is used as the outer insulating body.

www.systemprotection.in

• The arc shield prevents the deterioration of the internal dielectric strength by preventing metallic vapours falling on the inside surface of the outer insulating cover.

www.systemprotection.in

Working of Vacuum Circuit Breaker

www.systemprotection.in

• When the breaker operates, the moving contact separates from the fixed contact and an arc is struck between the contacts. The production of arc is due to the ionisation of metal ions and depends very much upon the material of contacts.

www.systemprotection.in

• The arc is quickly extinguished because the metallic vapours, electrons and ions produced during arc are diffused in a short time and seized by the surfaces of moving and fixed members and shields.

www.systemprotection.in

Click for Here Vacuum Circuit Breaker

www.systemprotection.in

www.systemprotection.in