VCB (Vaccum Circuit Breaker) - Electrical C & V


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18 March 2020

VCB (Vaccum Circuit Breaker)

What is VCB (Vaccum Circuit Breaker)?

The full form of VCB is Vacuum Circuit Breaker. The medium of extinguishing the electric arc generated in any abnormal situation or at the time of make and break is here. Therefore, it is called the VCB or the Vacuum Circuit Breaker. It is used in the VCB Panel of power stations, substations and industries. These breakers are used for medium voltage from 11kv to 33kv.

VCB (Vaccum Circuit Breaker)

The VCB has moving and fix contacts which are permanently sealed with vacuum. Due to vacuum sealing there is no oxygen content and the electrical arc extinguishes quickly. The degree of vacuum in this breaker ranges from 10-7 to 10-5 torr (unit of torr vacuum). After the air and SF6, then through other means, this breaker does its job in a very good way.

1. VCB is used from medium voltage ie 11kv to 33kv.
2. The Air Circuit Breaker is used for low voltage 450volt.
3. SF6 breakers are used for high voltage values ​​higher than 33kv.

Working Principle of Vacuum Circuit Breaker

Vacuum Circuit Breaker which breaks the circuit in abnormal condition. And according to our requirement we can open and close the circuit. The main work in VCB is of vacuum. The vacuum bottle has contact make and break. The above contact is fixed. And below are contact moving, which is make and break on getting the command.

The vacuum breaker in the circuit breaker does not have the value of oxygen in the bottle. Therefore, there is no arc generated. Or in other words, there is very little. Is caused by ionization of arc metal. And it also bases on the contact material. But vacuum is a much better medium than other insulating materials.

Metallic vapors, electrons and ions are generated during arc times. The arcs generated in it are extinguished by vacuum. Its dialectical strength is also better. Therefore, these breakers are considered better than others.

VCB also has protection in addition to overload, short circuit, earth fault, under-over voltage. Which provides protection to the electric circuit in any unusual situation.

Function of VCB Breaker 

1. Vacuum Circuit Breaker consists of Closing Circuit, Tripping Circuit, Indicating Circuit, Spring Charging Circuit.

2. In the closing circuit, the closing coil receives the command, which is the breaker close.

3. The tripping circuit supplies the shunt coil which separates the breaker from the circuit.

4. In the spring charging circuit, the spring charging motor of the breaker is supplied which is the spring charge of the breaker. Spring charge can also be done by manual handle.

5. Indicating circuit - This represents the current state of the breaker in this circuit of the VCB. It shows the breaker ON 'OFF' TRIP 'TRIP Circuit Healthy' and the breaker test and service position.

6. Auxiliary Contact - Circuit Breaker has some NO and NC contacts. Which is used for controlling and interlocking.

7. Counter - which counts breaker operation. Well in VCB you can do 1000 to 1200 operations.

8. Indicator - In circuit breaker test or service position, one can see the condition of spring charge or discharge and breaker close or open.

9. Vacuum Interrupter -
The one that creates an obstruction in the arc is called Interrupter. It has a steel arc chamber inside the ceramic insulator. Which has a vacuum. Fix and moving contacts are open and closed. Vacuum pressure is usually 10–6 bar.

Advantages of Vacuum Circuit Breakers

1- No gas or chemical is used in the operation of VCB breaker. Therefore, it is pollution free circuit breaker.

2- Vacuum Circuit Breaker offers both indoor and outdoor types. We can apply according to our needs.

3 - The number of options of VCB breaker is 1000 to 1200 which is much more than the other.

4 - Maintenance is very less. However, preventive maintenance is done once a year.

5 - Operation of Vacuum Circuit Breaker can be done very easily. And it is also cheaper in price.

Disadvantages of Vacuum Circuit Breakers

1 - Vacuum Circuit Breaker is only used up to 36kv.

2- A separate vacuum interrupter has to be used if using for more than this voltage.

3 - Design of Vacuum Interrupter requires very good technology.

4 - If the vacuum is released due to any reason, then the complete breaker becomes useless. To repair it, we have to send it out.

Application of VCB

1- VCB is very effective for high speed switching. Therefore, it is a very good option in the industry application.

2 - Vacuum Circuit Breaker Second Breaker in Law Fault Interception Capacity Breaker

3 - VCB is economically cheaper in price than a similar capacity breaker.

4 - Maintenance and problems in Circuit Breaker are negligible. Therefore, it is more prevalent.

For a medium voltage of 5 - 11kv to 33kv the efficiency of the breaker, operation, maintenance and price of the breaker is ahead of the Vacuum Circuit breaker compared to other breakers. Therefore, it is used in almost every industry.

 Maintenance of VCB

- The breaker is isolated and racked out after taking permission from the concerned department.
- The front cover and terminal cover of the VCB are opened.
- Circuit Breaker's power contact is cleaned with CRC 2-26 spray.
- Apply CRC 2-26 sprays to Vacuum Circuit Breaker's control contacts and moving parts. And it is cleaned with cloth.
- Every limit switch in Vacuum Circuit Breaker, Aux. Check the tightness of the nut bolt of the switch and mechanism.


- Dust proof grease ((ISOFLEX TOPAZ) is applied to each of the moving parts and micenizam peaks.
-Titeness of control and power contacts is checked.
- The bolt on top of the interrupter is tightened by hand. If it is too tight then it can be damaged.
- Circuit Breaker's micenisms, base plate and last cover of rake in out should be checked.
- Counter reading and status, closing tripping coil, spring charging motor and anti pumping contactor should be charged.
- Check the status of CT and PT in the VCB and the connection is tightness.
- Lubricate the earthing switch and shutter in the VCB Circuit Breaker.
- Breaker operation is done in test and service positions. And Induction lamps are also checked with every condition.

Circuit Breaker:- Click Here
Air Circuit Breaker:- Click Here
SF6 Circuit Breaker:- Click Here

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