A fuse is made up of a piece of metal that
melts when overheated; a circuit breaker has an internal switch mechanism that
is tripped by an unsafe surge of electricity. Fuses tend to be quicker to interrupt the
flow of power, but must be replaced after they melt, while circuit breakers can usually
simply be reset.
In this video I will go to show you Difference between Fuse and MCB.
·
Fuses
and MCBs are rated in amps. The amp rating given on the fuse or MCB body is the
amount of current it will pass continuously. This is normally called the rated
current or nominal current.
·
Many
people think that if the current exceeds the nominal current, the device will
trip, instantly. So if the rating is 30 amps, a current of 30.00001 amps will
trip it, right? This is not true.
·
The
fuse and the MCB, even though their nominal currents are similar, have very
different properties.
·
For
example, For 32Amp MCB and 30 Amp Fuse, to be sure of tripping in 0.1 seconds,
the MCB requires a current of 128 amps, while the fuse requires 300 amps.
·
The
fuse clearly requires more current to blow it in that time, but notice how much
bigger both these currents are than the ’30 amps’ marked current
rating.
·
There
is a small likelihood that in the course of, say, a month, a 30-amp fuse will
trip when carrying 30 amps. If the fuse has had a couple of overloads before
(which may not even have been noticed) this is much more likely. This explains
why fuses can sometimes ‘blow’ for no obvious reason.
·
If
the fuse is marked ’30 amps’, but it will actually stand 40 amps for over an
hour, how can we justify calling it a ’30 amp’ fuse? The answer is that the
overload characteristics of fuses are designed to match the properties of
modern cables. For example, a modern PVC-insulated cable will stand a 50%
overload for an hour, so it seems reasonable that the fuse should as well.
More information,
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