In a Circuit how the MCB and Fuse ratings are calculated.
And shall the fuse follws the MCB or it is otherwise?

Answer Posted / viraj dua

Dear all there are two parameters for determining the
selection of MCB
1.Type of load-
Resistive(e.g Home circuits)-B curve MCB(operates @
3-5 times the rated current)
Inductive-Motors etc.-C curve MCB(operates @ 5-10
times the rated current)

Highly inductive load-Transformers etc.-D curve MCB
(operates @ 10-15 times the rated current)

2.current in the circuit.

Now you will find that curve along with rated current is
mentioned on the MCB e.g. C6(do not confuse rated current
with the breaking capacity which is the max. current CB can
witstand)
C6 means this MCB is usable for Inductive load where
Circuit can witstand upto 30 Amps and MCB should trip if
Current Reaches 30 amps(5times of 6Amps)-60 Amps(10 Times)

Rated current is mentioned as 'ln' in electrical literature.

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