Answer / sanjay kumar

FUSE RATING CAN BE CALCULATED AS FOLLOWS:
SAY A MOTOR FULL LOAD CURRENT RATING IS 30A,TAKE FUSE OF
RATING 2.5TIMES OF FLC. SO FUSE RATING WILL BE 80A.IF IN
CASE THIS RATING FUSE IS NOT AVAILABLE, WE CAN GO FOR NEXT
HIGHER LEVEL. BUT IF NEXT HIGHER LEVEL FUSE IS SO HIGH THAT
IT CANT BE TAKE THEN GO FOR SOMEWHAT LOWER LEVEL. THIS IS
BASED ON MY EXPERIENCE IN THE INDUSTRY.


SECOND PAART IS FOR MCB:

MCB SELECTION SHOULD BE SOMEWHAT HIGHER THAN FUSE RATING.

Answer / amaravathi

fuse rating will be calculated by following formula.
125% of rated current.but we can use nearest value of fuse rating value.

Answer / devamanohar

The MCB rating shall be more than the fuse rating if it is
used for the service to switch off & on while the circuit
is in service.The fuse rating shall be 200% of the rated
curent normally as it is used for short circuit
protection.If the MCB is stay put type(No operation while
in service) it can be selected for rated current or 1.2
times of rated current value.

Answer / shaik

depending on the full load capacity ratings is calculated.
It is not necessary to connect MCB and fuse both,one is
enough.if u want to connect both then first fuse the MCB

Answer / mahesh s.chorghe

MCB RATING SHOULD BE 2.5 TIMES OF LOAD CURRENT AND FUSE
RATING GRETER THAN (1.5 TIMES)MCB

Answer / moideen.t.y

Fuse size can be calculated by this formula, 225% of full
load current.
locked rotor amps is the 500% of full load current.

400kw, 3.3Kv motor want to fix 1000km away from substation. What is full load current? and what is the cable size for motor? I amp expecting answer and advice from your side.. thanks...

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