MCCB,VCB,ACB all are of different type with same
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
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
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: 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 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
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
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
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
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.
If i have two 3000 kW motors and the whole facility requires
a 10 MVA transformer.
What would be better installing two 5 MVA transformers(one
for 1 motor ) or just a single 10 MVA transformer for both
Give reasons for your answer.