This document summarizes a presentation on circuit breakers. It defines a circuit breaker as an electromechanical device that operates automatically under normal and abnormal conditions. It discusses the arc formation process between circuit breaker contacts and classifications of circuit breakers based on the interrupting medium used, including bulk oil, miniature oil, air, air blast, SF6, and vacuum circuit breakers. Advantages and applications of each type are provided. In conclusion, it restates that a circuit breaker is an automatic device with fixed and moving contacts that uses different mediums to extinguish arcs, and types of circuit breakers depend on their breaking capacity.

1. A presentation on
Presented by,
Mr. Chetan D. Patil
Assistant Professor
Department of Electrical Engineering
Circuit Breakers
Sharad Institute of Technology,
College of Engineering,
Yadrav (Ichalkaranji)

2. Contents:
• Classification of Conducting Materials:
 Introduction
 Arc formation process
 Voltage current characteristic’s of arc
 Classification of circuit breakers
 Advantages and Disadvantages
 Applications

3. Introduction:
• It is a electromechanical device
• It is operate automatically and manually under normal and abnormal condition
• The circuit breaker has mainly two contacts :
 Fixed contact
 Moving contact

4. Arc Formation Process :
• Normally the contact area between the two
contact is less
• During a fault condition due to the less
contact area current density is maximum
and due to this temperature between two
contact is high
• Due to this ionized particles produced in
surrounding area acts as conductor is
called as “ARC”

5. Voltage-Current Characteristics of arc:
• Arc voltage
• Transient restriking voltage
• Recovery voltage
• RRRV
• Current chopping

6. Classification of Circuit Breakers :

7.  1) Bulk Oil Circuit Breaker:
• In this type large amount of oil is used
• The oil serves to purpose,
 It extinguishes the arc
 It isolate the current conducting path between contacts

8.  2) Miniature Oil Circuit Breaker:
• Drawback of bulk oil circuit breaker is overcome by using MOCB
• There are two main parts,
 Circuit breaking chamber
 Supporting chamber

9.  3) Air Break Circuit Breaker:
• Drawback of bulk oil circuit breaker is overcome by using
MOCB
• It consist of main contact and arcing contact
• The both contacts are made up of high resistance copper alloy
with silver plated
• Arc splitters are used to increase length of arc

10.  4) Air Blast Circuit Breaker:
• In this type of CB pressurized air is used for arc
extinguishing
• In this type the contact are separated at a very small
distance near about 1.75cm

11. Advantages of ABCB:
- Cheapness and free availability of interrupting media
- High speed operation
- Elimination of fire hazard
- Less maintenance, suitable for frequent operation

12. Disadvantages of ABCB:
- An air compressor plant had to be installed and maintained
- The air blast CB has high level noise when air is discharged
- Problem of re-striking voltage
- Problem of chopping of current

13.  5) SF6 Circuit Breaker:
• Properties of SF6 gas:
 It is colorless, odorless and non-toxic
 It is non-inflammable
 It is chemically inert gas
 It is electronegative gas

14.  6) Vacuum Circuit Breaker:
• In such breaker vacuum is used as arc quenching media
• Range of vacuum is 10−7
to 10−5
Torr
• Arc is struck between contact it because of metallic vapor
thus arc is stickily quenched because of high dielectric
strength of vacuum

15. Advantages of VCB:
- Simple in construction
- The contact separation is about 1 cm which is adequate for current interruption
- It has less maintenance, silent operation
- Long life, high speed of dielectric recovery

16. Disadvantages of VCB:
- It is costly
- In the event of loss of vacuum, the entire CB become useless
- It can’t be repaired at the site

17. Applications:
• Classification of Conducting Materials:
 Introduction
 Arc formation process
 Voltage current characteristic’s of arc
 Classification of circuit breakers
 Advantages and Disadvantages
 Applications
Sr. No. Type Of Circuit Breaker Applications
1 Bulk Oil Circuit Breaker Medium voltage circuit
up to 22KVA.
2 Miniature Oil Circuit Breaker For outdoor
applications.
3 Air Break Circuit Breaker For low voltage and
medium voltage
application.
4 Air Blast Circuit Breaker For arc furnace, in EHV
lines.
5 SF6 Circuit Breaker For medium and high
voltage protection.

18. Conclusion:
It is an electromechanical device which operate automatically and manually
under normal and abnormal condition. It has mainly two contacts fixed and moving contact.
The classification of CB depends on the basis of medium used for arc
extinguish. Depending upon their breaking capacity CB’s are used.

19. Thank you ….