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..


They are two different things.

A load break switch is a device which can be manually switched by a person. It is there to be able to switch a power supply on to a load or to isolate the load. The significance of the words “load break” is that the switch is designed to be able to interrupt the current passing through it. i.e a 400A load break switch is designed to carry up to 400Amps continuoulsy and also to be able to break (switch off) up to a 400Amp flowing current.

This is in contrast to an isolator (or non load break switch) which is designed to carry the current but not interrupt it. With an isolator there must be another switch upstream to break the current as the isolator is designed to switch at zero amps.

A fuse is a non manually switchable device. It is a fault current  interruption device. It is designed to carry a given current continuously but to rupture when a current higher than that given current passes through it. The time that it will take for the fuse to rupture is dependent on how much above the fuse rating the current flowing is. As an example, a current twice that fuse rating may cuase the fuse to rupture in an hour or two. A current twenty times the rating will cause the fuse to rupture in a fraction of a second. HRC (High Rupture Capacity) fuses are capable of interrupting very high currents (many thousands of Amps) and thus are used for short circuit protection.

Some fuses are unstalled into holders but others may be bolted into circuits. With fuses in holders, you can isolate a circuit by fulling out the fuse. This is handy as you can see a visible break in the circuit. However you should never full out a fuse from an energised circuit. You should always switch the circuit off first. If you were to full a fuse on a DC (Direct Current) circuit which was feeding ai inductive load you could draw an arc which could be damaging to the equipment and even fatal to yourself.