Re: LBS and fuse


demiz said:

dear administrators and all engineers..

i'm a student..

i'm very confused about Load Break Switch and also Fuse..

can you help me please..

i need it for my study..


thanx before..

i hope u will..


A load break switch is a device designed to manually switch a circuit on and off. It can be used for manual control and isolation. It is designed to carry a particular current continuously and also to be able to interrupt that current. For example a 400A load break switch will carry up to 400A continuously and interrupt up to 400Amps. This is in contrast to an isolator( or non-load break) switch which is designed to isolate the circuit only. For example a 400Amp isolator will carry 400Amps continuously but the circuit has to be switched off by some other means before the isolator can be opened as its breaking capability is ZERO Amps.

A fuse is a non switchable device which is designed for circuit protection rather than control. A fuse of a given rating will carry the current of that rating continuously but if the current goes above that value, the fuse will rupture and disconnect the load. How long it takes for the fuse to rupture is a dependent on how much above the rating the current that is flowing in the circuit is. As a rough example,  if the current is twice that of the rating the fuse may take a a few minutes, even an hour to rupture depending on the particular characteristic. If the current is twenty times the rating the the fuse will rupture in a a fraction of a second.

Fuses may be in holders with removeable carriers or bolted into a circuit. If in a holder, they can be used for isolation purposes as a removed fuse shows a visible break in the circuit. However a fuse should never be removed from a energised circuit. Doing so could result in the drawing of an arc which may damage equipment or be fatal to the remover.


Hope that this helps.

Good luck with your studies