Construction of Vacuum Circuit Breaker
A vacuum circuit breaker consists a moving contact, a fixed contact and a vacuum interrupter. The moving contact is connected to the control mechanism by stainless steel bellows. The fixed and moving contacts are inside an arc shield and the arc shield is located inside the vacuum interrupter. The pressure inside the vacuum interrupter is kept around 10-6 torr at the time of sealing.
The moving contact of the circuit breaker are made to move nearly 5mm to 10mm depending upon the voltage level. The outside envelope of vacuum circuit breaker is made up of glass or ceramic insulating vessel. The contacts are usually made from copper chrome and copper bismuth.
Working of Vacuum Circuit Breaker
When the fault occurs, the control mechanism moves moving contact of the circuit breaker apart from the fixed contact to break circuit connection and arc is generated between the contacts due to ionization of metal ions. Due to the generated arc, the temperature of the contacts raises very high and the contact spaces is filled with vapour of positive ions that is discharged from the contact material.
Advantages of Vacuum Circuit Breaker
- Small size
- Light weight
- Suitability for frequent operation
- Less chance of fire or explosion
- Do not use any harmful chemicals
- Long lifespan
- Very less maintenance
Disadvantages of Vacuum Circuit Breaker
- Difficult to repair in-site
- Cost increases with higher voltages