A vacuum circuit breaker is the suitable for mainly medium voltage application circuit breaker where the arc quenching takes place in vacuum. The major parts of Vacuum Circuit Breakers circuit breaker are breaker contacts. Vapor condensing shields, metallic bellows. End flanges and enclosure. The vacuum pressure inside a vacuum interrupter is normally maintained at 10 - 6 bar.
In this video I will share about vacuum circuit Breaker.
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The production of arc in a vacuum circuit breaker and its extinction can be explained as follows:
• When the contacts of the breaker are opened in vacuum, an arc is produced between the contacts by the ionization of metal vapors of contacts. However, the arc is quickly extinguished because the metallic vapors, electrons and ions produced during arc rapidly condense on the surfaces of the circuit breaker contacts, resulting in quick recovery of dielectric strength.
• 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.
Typical parts of vacuum circuit breaker are shown in the figure.
• It consists of fixed contact, moving contact and arc shield mounted inside a vacuum chamber.
• 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.
• A glass vessel or ceramic vessel is used as the outer insulating body.
• The arc shield prevents the deterioration of the internal dielectric strength by preventing metallic vapors falling on the inside surface of the outer insulating cover.
• 1. Capacitor bank switching
• 2. Reactor switching
• 3. Transformer switching
• 4. Line dropping.
• 2. Self contained i.e., no need of periodic refilling of gas or oil.
• 3. Compact size.
• 4. Low power requirement for making and breaking operations.
• 5. Pollution free.
• 6. Long life
• 7. Non-explosive.
• 8. Suitable for repeated operating duty.
• 9. High speed ’of dielectric recovery.
• 10. Silent operation.
• 11. Low maintenance.
• 12. Capable of interrupting highly inductive and capacitive currents without restriking.
content source by-
http://www.electricaledition.com/2015/12/vacuum-circuit-breakers-vcb-construction-advantages.html
http://www.studyelectrical.com/2014/11/vacuum-circuit-breaker-vcb-working-construction.html