The document provides information about circuit breakers, including: 1) A circuit breaker is a device that can automatically or manually close or open an electrical circuit under normal or abnormal conditions. 2) It operates using two contacts, two coils, and pilot devices to sense faults and trip the circuit. When a fault is detected, the tripping coil energizes to separate the contacts. 3) An arc is produced when the contacts separate but current continues through the arc. Circuit breakers must extinguish the arc quickly.

1. A Presentation on
CIRCUIT BREAKER
Presented by-
SAYAN SARKAR
ROLL NO. 13001616049
EE-3RD YEAR-SEC ‘A’

2. DEFINITION
 It is a device designed to
close/make or open/break the
electrical circuit under abnormal
and normal conditions
automatically and also manually.

3. OPERATING MECHANISM
Circuit Breaker consists of two contacts:
• Fixed contact.
• Moving contact.
Circuit breaker consists of two coils:
• Closing coil –Used to close the circuit.
• Tripping coil-Used to trip the circuit.
CBs are usually arranged with pilot devices to sense a fault
current and to operate the trip opening mechanism
Two contacts called electrode remains closed under normal
operating conditions. When fault occurs on any part of the
system, the trip coil of the circuit breaker get energized and
contacts are separated.

4. ARC PHENOMENON
• An arc is struck when contacts are separated. The current is
thus able to continue. Thus the main duty of a circuit breaker is
to distinguish the arc within the shortest possible time.
• The arc provides the low resistance path to the current and the
current in the circuit remains uninterrupted.
• Arc Resistance depends on factors like:
Degree of Ionization
Length of the arc
Cross section of arc

5. Methods of Arc Quenching
High Resistance Method
• Lengthening of arc
• Reducing the cross
section of the arc
• Splitting the arc
Low Resistance Method
• Lengthening the gap
• High pressure in the
vicinity of the arc
• Cooling the dielectric
medium
• Blast Effect

6. Terms RelatedTo Circuit Breakers
 Arc Voltage
 Restriking
Voltage
 Recovery
Voltage

8. HOW TO CHOOSE A CIRCUIT BREAKER
Voltage
Frequency
interrupting capacity
continuous current rating
unusual operating conditions
product testing

9. THANK
YOU