Jitendra A. Khetani said:
Folllowings are advantage & disadvantage of MCCB & HRC FUse:
1) MCCB to be replaced once it trips on short circuit. Hence shut down for replacement of MCCB.
2) In PCC, Fault current is more, You must use Control fuse instead of MCB as fuse is rated for 80KA or 120KA while MCB is rated for 10KA or 15KA.
3) Wherever you use MCCB, MCCB with Earth fault protection release must be taken, otherwise MCCB will not trip on Ground fault and your Main breaker will trip. But if had use fuse, Fuse will blow off in case of Ground fault.
4)Fuse replace ment will take time.
5) Blowing of fuse of one phase crate single or 2 phase supply & burning of motor.
Jitendra A. Khetani
Excuse-me, but there's some things in your comments should be clarified that are :
1 – About tripping of MCCB on short circuit : If the values of ” Breaking Capacities on Service – Ics “ of installed MCCB or even MCB in any LV network have been correctly chosen depending on the values of ” Isc3max “, no need to replace them after tripping on short circuit.
2 – About the Breaking Capacities of ” MCB ” : certainly that most of used MCB's have ” 6, 10, or 15kA ” but many manufacturers like ” Schneider Electric, ABB, Legrand, hager, and others ” have MCB's with ” 25, 35, and even 50kA ” but the tests' sequences are depending on ” IEC 60947-2 “.
3 – About the tripping of MCCB on Ground Fault ( or Earth Fault ) :
A – The MCCB without earth fault protection can trip on Earth Fault if the value of the magnetic protection built in the MCCB is
smaller than the value of the earth fault current.
B – If the outgoing MCCB installed on the top of the earth fault circuit is not trip but the main MCCB tripped that means the magnetic
protection value of the outgoing MCCB is bigger than the Earth Fault Current, so, the chosen of this protection is not correct and
even the magnetic protection value of the main MCCB is smaller than the Earth Fault Current !!!!!
C – Normally, depending on the used Earthing System, we should calculate the earth fault current value, then decide if the MCCB
should be without or with an Earth Fault Protection, and even this decision will be done depending on the used Earthing System.
For exp. in ” TN-C ” we can't use the Earth Fault Protection, so, in this case, we have only the Magnetic Protection that
should trip on earth fault.