Fuses - Destruction for Good!
By: Thomas Yoon
Destruction! Blow Up! Eliminate! These are not pleasant words!
Unfortunately, when it comes to safety we have no other choices.
In the electrical industry, fuses are destroyed in order to
protect lives or property.
Whenever there is a big fault in the power lines, possibly caused
by short-circuiting, fuses are very helpful to stop the flow of
Unlike circuit breakers, fuses have no mechanical moving parts
that can fail to operate. A fuse is just an electrical link in
the circuit that can melt very quickly whenever a certain
temperature is reached.
Fuses have 4 things to do in a circuit:
- They must sense faults
- They must open quickly when a short-circuit occurs
- They must also sense the normal overloaded conditions, but
must open if the overload becomes excessive or prolonged.
- They must not change or alter the characteristic of the current
during normal operation.
Early types of fuses use lead wires, selected based on their
diameters, connected to terminals. These types have some
disadvantages. Whenever a fuse blows, the molten metal spatters
over the equipment and could cause injury to people or cause fires,
especially when the arc was not confined.
Later, cartridge fuses replaced the old lead wire fuses. These
consist of non-conducting cylinders which contain soft metal fuse
strips. The strips are connected to the ends of the cylinders by
metal caps or ferrules. The entire cartridge fuse is mounted onto a
matching fuse block.
Even these cartridge fuses have 2 types - those with renewable fuse
links and those one-time non-renewable types. The only advantage of
the renewable type - they are more economical because the cartridge
can be reused. However, more precautions are needed with regards to
the cleanliness of the contacts, the securing of the cap bolts, and
the choice of the current rating of the link.
Whenever a fuse blows, it means there is already a big fault in the
circuit. Electricians must be especially careful during this time
and take the necessary precautions. The fuses blow up for safety.
Don't cause another blow up!
Until next time...
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