Home › Electrical Engineering Forum › General Discussion › Applications where LV fuses are technically more adapted than LV circuit-breakers? › Re: Applications where LV fuses are technically more adapted than LV circuit-breakers?

Dear Mr. Anilsabaji ;

First, as you said the VSD can withstand up to “ 65kA ”, but I want to add that this value is depending on the VSD’s Type and the manufactures.

About your example “ 8 Alternators ” I have the following comments :

1 – As we know all that many CB manufactures produce a special rang of CB called “ Limiter CB ” that can limit the Short Circuit Currents, and also they added in the catalogs some special tables containing the “ Upstream & Downstream Values ” of the short circuit currents for each “ Limiter CB ” as a guide for the users, so, we can use them where we need to limit the short circuit currents even to a value smaller than “ 10kA ”.

2 – As I understood that each Alternator is “ 2000kVA, 690V, 60Hz, X”d=20% ”, and by a simple calculation we know that exactly at the connection points “ Isc3max = 9.23kA ”, and by using the necessary cables ( only 15meters ) it drops to “ ≈ 9kA ”, that means by splitting these 8 alternators into 2 groups of “ 4 ”, the Short Circuit Current value at BB will be “ ≈ 36kA ”, so, we don’t have any problem for the big VSD, and for the small the problem can be solved by using a Limiter CB.

3 – Also we know all the there are some weakness points of Fuses, like : 1 of 3 fuses blown that are using to protect an Outgoing, where to know it we should use a special fuses equipped with “ Striker ” with also a special base of fuse holder equipped with “ Auxiliary contact ” by which we will have a signal once happen.

4 – Using the Fuses to protect circuits oblige to have Fuses as spare parts from all installed kinds and ratings to be able to replace any blown one.