Mccb is moulded case circuit breaker.
ACB is air circuit breaker.
VCB is vacuum circuit breaker.

MCCB,VCB,ACB all are of different type with same 
functioning.
all of them are used to isolate the power or to trip the 
power at the time of fault in line and thus save the 
circuit from further damage and isolate unheathy part from 
healthy one.
if the circuit if of low rating we can go ahead with MCCB 
but for high rating circuit we go for costlier CB that is 
ACB/VCB because they are more reliable and have long life.

MCCB - Thermomagnetic operaton-For large surges in ct- In
distribution boards-bimetallic strip responding to less
extreme but longer_term over_current conditions-applicable
for    
low voltages.
ACB - low volt power cb-trip characteristics r
adjustable-air s the arc quenching medium-applicable upto 440V.
VCB - medium volt power cb-trip char. adjustable-mechanical
sys. used for trip & open-Vaccuum s the arc quenching
medium-applicable upto 36kV.

MCCB,ACB,VCB all the three are protective devices only. 
They are used to isolate the system which is connected 
below them at fault conditions. Eg, Overload, Short 
circuit,Earth fault.

Depending upon the operating voltages and level of 
protection(Fault Level) needed for the system ,these three 
protection device are selected.

For Eg: If the operating voltage are below 1100V, depend 
upon the fault level we can use MCCB or ACB.

Simillarly if operating voltage are more than 1100V,VCB are 
used.

Mccb is moulded case circuit breaker.
ACB is air circuit breaker.
VCB is vacuum circuit breaker.
But Basic Differnce Is

Mccb use for Low value of current(16A,10A..)
Mccb depend upon Number of Pole
ACB USE FOR PROTECTION IN TRANSMISSON OF POWER IN POWER PLANT
VCB USE FOR PROTECTION IN DISTRIBUTION OF POWER IN POWER PLANT

MCB is stand for miniture circuit breaker.It is for low 
voltages.         
MCCB is stand for moulded case circuit breaker. It is for 
medium voltages. 
ACB is stand for Air circuit breaker.It is for high 
voltages.

MCCB: means moulded case circuit breaker which use ark 
quenching device as AIR which is used upto 500 Amps only
ACB:air circuit breaker which use quenching device as air 
and used upto 3000 Amps at 415 volts 
VCB:vaccum circuit breaker which use ark quenching device 
as a vaccum and used for 415 volts.6.6 KV,11 KV,33 KV,132 
KV,220 KV also.

Mccb is moulded case circuit breaker.
ACB is air circuit breaker.
VCB is vacuum circuit breaker.
MCB is stand for miniture circuit breaker.It is for low 
voltages.         
MCCB is stand for moulded case circuit breaker. It is for 
medium voltages. 
ACB is stand for Air circuit breaker.It is for high 
voltages.

MCCB which is nothing but moulded case circuit breaker.
ACB is nothing but Air circuit breaker and Vcb is Vaccum 
circuit breaker..The main difference between last two thing 
is the arc quenching medium.ACB is air and VCB is 
vaccum.these two things are used for power tr and 
distribution and MCB,MCCBs are used in small rating 
machines also...

wtat is st and pt, ct

MCCB MEANS MOULDED CASE CIRCUIT BREAKER IT IS USED FOR ARC 
QUENCHING AND MEDIUM VOLTAGE

VCB MEANS VACCUM CIRCUIT BREAKER IT IS USED FOR ARC 
QUENCHING HIGH VOLTAGE

ACB MEANS AIR CB AND IT IS USED FOR ARC QUENCHING AND HIGH 
VOLTAGE

MCCb is reliabilty is less
ACB compare to mccb its good
Vcb is more reliability

MCCB-- Moulded Case Circket Breaker
ACB -- Air Circket Breaker
VCB -- Vacume Circket Breaker

MCB we use from 0 to 64 Amp.
MCCB we use from 64 to 800 Amp
ACB we use above 800 Amp

More ever at much higher current level we use VCB because 
at higher current the air around it get ionised and become
conducter which causes short ckt. so at much higher current 
level we generaly use VCB.

VCBs are used primarily for medium voltage circuits (11kV 
in UK), due to their better arc quenching abilities (these 
high voltages in ACBs or MCCBs would cause an arc between 
the terminals and render the breaker useless).

The fundamental differences between ACBs and MCCBs are.
1. MCCBs cost far less than ACBs
2. MCCBs are better at lower interrupt currents (below 
630/800A), ACBs are better at higher currents (800A and 
above)
3. ACBs are a lot bigger and take up large sections of 
panel that you might be able to fit 3 or 4 smaller MCCBs 
into.
4. The main advantage is ACBs perform better under high 
current short circuits, and will normally withstand for 
long enough to allow a downstream device to open and clear 
the fault, thus localising the short circuit trip.
5. ACBs are more easily serviced (particularly withdrawable 
type).

MCCB-MOULDED CKT BREAKER USED FOR LT SIDE
ACB-AIR CKT BREAKER USED FOR LT SIDE
VCB-VACCUME CKT BREAKER USED FOR HT SIDE

MCBs are miniature circuit breakers with optimum protection
facilities of overcurrent only.These are manufactured for
fault level of up to 10KA only with operating current range
of 0.5 to 63 Amps (the ranges are fixed), single,double and
three pole verson.These are used for smaller loads
-electronic circuits,house wiring etc.
MCCBs are Moulded case Circuit breakers,with protection
facilities of overcurrent, earth fault.it has a variable
range of 50% to 100% operating current.They can be wired for
remote as well as local operation both.They are manufactured
for fault levels of 16KA to 50KA and operating current range
of 25A to 630Amps.They are used for aplication related with
larger power flow requirement.

MCCB---- For Lower Operating Currents & Use And Throw
Technology.(in india generally up to 800A).
ACB --- For High Operating Currents & High end Product &
Protection Features & where Maintanance of Circuit Breaker
is required...
VCB  --- For Higher Operating Voltages--- 6.6KV & above....

amazing how much bullsh*t people put up on here about 
MCCB/ACB/VCB.  be careful when you read the information on 
here, and don't trust 100% that the answers given are 
correct.

MCCB-- Moulded Case Circket Breaker
ACB -- Air Circket Breaker
VCB -- Vacume Circket Breaker

MCB we use from 0 to 64 Amp.
MCCB we use from 64 to 800 Amp
ACB we use above 800 Amp

More ever at much higher current level we use VCB because 
at higher current the air around it get ionised and become
conducter which causes short ckt. so at much higher current 
level we generaly use VCB.
  
Is This Answer

mccb rating 63Ato 400A
ACB instoll the L.T.
VCB instoll the H.T.

MCCB-MOULDED CKT BREAKER USED FOR LT SIDE
ACB-AIR CKT BREAKER USED FOR LT SIDE
VCB-VACCUME CKT BREAKER USED FOR HT SIDE

the main difference is mccb means moulded case circuit 
breaker which use ark 
quenching device as AIR which is used upto 500 Amps only
ACB:air circuit breaker which use quenching device as air 
and used upto 3000 Amps at 415 volts 

Mccb is not having a long life ACB is having long life

mccb s the used low rating Lt pannel.
acb s the used high rating Lt pannel.
vcb s the used high rating Ht pannel.

MCCB( moulded case circuit breaker),VCB(vacuum circuit 
breaker),ACB(air circuit breaker) all are of different 
types of breaker with same 
functioning. name given them according to arc quenching 
medium used inside the breaker i.e. air,vacuum,oil,sf6 etc.
all of them are used to isolate the electrical ckt by 
manually as well as automatically to trip at the time of 
fault in line and thus save the 
circuit from damage and isolate unheathy part from 
healthy one.
if the circuit is of low(voltage &current)rating we can go 
ahead with MCCB or MCB. 
but for high (voltage &current)rating circuit we go for 
costlier Breaker that is 
ACB(air circuit breaker)or VCB(vacuum circuit breaker),OCB
(oil circuit breaker),SF6 etc. because they are more 
reliable and have long life.