CIRCUIT BREAKER IS A MECHANICAL
SWITCHING DEVICE CAPABLE OF MAKING ,
CARRYING AND BREAKING SERVICE CURRENTS.
IT SHALL ALSO MAKE , CARRY FOR
A SPECIFIED TIME AND BREAK UNDER SPECIFIED
ABNORMAL CONDITIONS SUCH AS A SHORT
CIRCUIT .
LVSM8.PPT/NRS
BASIC FUNCTIONS OF A CIRCUIT BREAKER
TO MAKE, CARRY & BREAK SERVICE CURRENTS
TO PROTECT THE SYSTEM AGAINST ABNORMAL
CONDITIONS LIKE OVER LOAD, SHORT CIRCUIT
AND EARTH FAULT
TO PROVIDE THE RIGHT DISCRIMINATION TO
ENSURE CONTINUOUS SUPPLY TO ALL
HEALTHY FEEDERS IN CASE OF A FAULT
ON ONE FEEDER
TYPES OF L.T. CIRCUIT BREAKERS
OIL CIRCUIT BREAKERS
AIR CIRCUIT BREAKERS
MOULDED CASE CIRCUIT BREAKERS
MINIATURE CIRCUIT BREAKERS
MOTOR PROTECTION CIRCUIT BREAKERS
CONTACT MECHANISM OF ACB
ARC CHUTE
ARCING CONTACT
ARC
BUTTONS
LVSM8.PPT/NRS
AIR CIRCUIT BREAKER
MANUALLY
OPERATED
FIXED TYPE
DRAW OUT TYPE
ELECTRICALLY
OPERATED
FIXED TYPE
DRAW OUT TYPE
LVSM8.PPT/NRS
AVAILABLE RATINGS
1000 AMPS
2000 AMPS
4000 AMPS
630 AMPS
1250 AMPS
2500 AMPS
5000 AMPS
800 AMPS
1600 AMPS
3200 AMPS
6300 AMPS
UTILISATION CATEGORIES
A
CIRCUIT BREAKERS NOT INTENDED FOR
SELECTIVITY UNDER SHORT CIRCUIT
CONDITIONS AND THEREFORE WITHOUT
A SHORT TIME WITHSTAND CURRENT.
B
CIRCUIT
BREAKERS
INTENDED FOR
SELECTIVITY UNDER SHORT CIRCUIT
CONDITIONS AND THEREFORE WITH A
SHORT TIME WITHSTAND CURRENT.
CIRCUIT BREAKER SELECTION - PARAMETERS
1.
2.
3.
4.
5.
6.
7.
CURRENT RATING & VOLTAGE
SHORT CIRCUIT BREAKING CAPACITY
SHORT CIRCUIT MAKING CAPACITY
UTILISATION CATEGORY
VERSION
TYPE OF OVER CURRENT PROTECTION
ACCESSORIES
-- VOLTMETRIC RELEASES
-- EARTH FAULT RELEASE
-- LOCKS & INTERLOCKS
-- MICRO SWITCHES
SHORT CIRCUIT MAKING CAPACITY DEPENDS ON
1
POWER FACTOR
2
INSTANT OF SWITCHING RATIO ( n )
SHORT CIRCUIT MAKING CAPACITY n =
SHORT CIRCUIT BREAKING CAPACITY
RATIO n BETWEEN SHORT C IRCUIT MAKING CAPACITY
AND SHORT CIRCUIT BREAKING CAPACITY
SHORT CIRCUIT
BREAKING
CAPACITY
( I in KA - rms )
POWER
FACTOR
MINIMUM