Vadodara institute of engineering,kotambi

NAME:NAFISKHANPATHAN(13ELEE181)

BARIYA VIPUL(13ELEE182)

PATEL AMIT(13ELEE180)

BRANCH:EE-2

PPT OF EEE

Miniature circuit breaker(mcb)

Miniature Circuit Breakers (MCB)Multi 9

Protect cables againstoverloads and short

circuits Let the current flow

without overheating on cables

Open and close a circuit under rated current

Protect against insulation

faults (see earth leakageprotection module)

DefinitionMain functions

Miniature circuit = switch + trip unit breaker (MCB)

Symbol

A mechanical system to open and close the circuit

A bimetal strip to act against overloads

A magnetic trip to act against short circuits

DefinitionA Multi 9 circuit breaker has:

Miniature circuit = switch + trip unit breaker (MCB)

It has standardized modular dimensions

125A

50 kA

440 V CA

DefinitionMain performances

It fits in your pocket...

Definition

Multi 9 standard Multi 9 switchgear comes in 9 mm pitch

width

symmetricalrail

externalpartdepth

6010 maxi

3545maxi

44 maxi

21.3

81

The modular design meets 2 criteria:

mounting on a 35 mmsymmetrical rail

dimensions- modules in widths of 17.5 mm + 0.5 - 0- external part = 45 mm- depth between 55 and 70 mm

The technologyActive parts

C60N NC100 / NC125

terminal

fixed contact

movingcontact

strip braid

magnetictrip

load side terminal

terminal

bimetral strip

strip braid

movingcontact

magnetic trip

load side terminal

strip braidbimetal strip

Overload protection

bimetal

tripping barbimetal

tripping bar

screwcalibration

stripbraid

NC45 NC100 / NC125

A bimetal strip is used: to protect the cable against overloadssymbol: principle of the bimetal: in a Multi 9 circuit

breaker

Thermal tripping curve

the "thermal" part of thetripping curve must be

inaccordance with the

standard

Overload protection

Legend:In = rated currentInd = no tripping currentId = tripping current

tripping

notripping

destructionof bimetal

accuracy

t (s)

I/InIn Ind Id

Overload protection

Simultaneous multi-pole tripping

Temperature derating our circuit breakers do not have temperature

compensation if the calibration temperature is different from

the ambient temperature: derating is required

Short-circuit protection

Short-circuit current is given as RMS or peak(Isc or Îsc)RMS = Root Mean Square in symmetrical DC(with PF = I)

Short-circuit protection must limit thermal stress in the cable in order to prevent cable damage (which may reach vaporization of the copper in some cases)

Comments slide 29

Short-circuit protection

"By-pass" technique for the protection of sensitive partsof the circuit breaker DCbreaking is difficult

"By-pass" technique for the protection of sensitive parts of the circuit breaker (magnetic trip)

The arc in Multi 9 circuit breakers

2 breaking techniques used by Multi 9

arcinghorn arcing

horn

NC45 NC100 / NC125

Short-circuit protectionMagnetic tripping curve

Our curves are instantaneous tripping curves

Legend:Ind = no tripping currentId = tripping current

destructionof the solenoid

trippingnotripping

t (s)

I/InInd Id

B curve 3 and 5 In protection

low short-circuit current generators

The magnetic tripping levels with high inrush current:like LV/LV transformers

C Curve 5 and 10 In control and protection of

circuits with high short-circuit currentin industrial and domestic distributions

D and K curves tripping betwen tripping: 10 to 14 In; more particulary

adopted for installations with highinrush currents like LV/LV transformers

Z curve 2.4 to 3.6 In protection against

electronic circuits

MA curve 12 In; protection only against

short-circuit and high inrush currentssuch as motors, coil

G

M

Side panel marking:

Marking

Front panel marking:

Circuit breaker marking is governed by strict rules in accordance with the standards and decisions made by the manufacturer

Choosing a circuit breakerIn conclusion

A Multi 9 circuit breaker is determined by:

rating

breaking capacity number of poles

voltage

tripping curve standard

frequency

type of load

Auxiliaries: C60

SD: alarm switch MX + OF: shunt trip MN: undervoltage release

The information is transmitted via a mechanical link C60/NC100 and NC125 auxiliaries are not compatible

54 mm maxi

4 types of auxiliaries for ourMulti 9 circuit breakers

OF: indication switch

MX+OFOF SD C60

44/3

MN

51/3

52/3

54/3

53/3

Auxiliaries: NC100 - NC125

The information is transmitted via a mechanical link C60/NC100 and NC125 auxiliaries are not compatible

NC100H MX+OFor Vigi

MN orOF SD

33/3

34/3

35/3

36/327

/3

SD: alarm switch MX + OF: shunt trip MN: undervoltage release

4 types of auxiliaries for ourMulti 9 circuit breakers

OF: indication switch

THANKYOU