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If there is a fault in a
piece of equipment then
excessive current may
flow.
This will cause
overheating and possibly
a fire.
Fuses protect against
this happening. Current
from the supply to the
equipment flows through
the fuse.
 The fuse is a piece of
wire which can carry a
stated current. If the
current rises above this
value it will melt.
If the fuse melts
(blows) then there is an
open circuit and no
current can then flow
thus protecting the
equipment by isolating
it from the power
supply.
The fuse must be able to
carry slightly more than
the normal operating
current of the equipment
to allow for tolerances
and small current
surges.
With some equipment
there is a very large
surge of current for a
short time at switch on.
If a fuse is fitted to
withstand this large
current there would be
no protection against
faults which cause the
current to rise slightly
above the normal value.
Therefore special antis
urge fuses are fitted.
These can stand 10 times
the rated current for 10
milliseconds. If the
surge lasts longer than
this the fuse will blow.
Always find out why the
fuse blew before
replacing it.
Occasionally they grow
tired and fail. If the
fuse is black and
silvery then it is
likely that there is a
dead short (very low
resistance) somewhere.
ALWAYS REPLACE THE
FUSE WITH THE CORRECT
TYPE AND VALUE. |
