Stupid question.

[La Poste]

This may be a daft question so please excuse me.
Why is a domestic 230 volt supply protected by a 100A 415 volt fuse.
The house I am helping with at the moment has a 100A 415 volt main fuse, that's what it says on the fuse holder.
http://www.neweysonline.co.uk/newle...415v-ac/1050152900/ProductInformation.raction
The supply is 230 Volts, I don't get it.
Thanks.

 

[jeremy]

It can be used in applications up to 415V i.e a 3phase supply. Not a daft question, at least your noting all the details on the fuse!

 

[johnboy6083]

no such thing as a daft question, there is such a thing as a daft person who doesnt ask if they dont know!

 

[rocker]

It's what voltage it goes up to, doesn't necessarily mean it's the only voltage that can be used. A bit like amperage ratings I guess.

 

[wattsup]

You can't get 415v on a single line fuse 3-phase, to get that, the feeder cable would blow up first -

To get 400v on one fuse, transformers, dc supplies etc. Voltage don't matter up to a point, possible 1000v, the 100A is all that matters. Hence a variety uses up to a point

 

[jeremy]

Now I'm going to ask the potentially (pun not intended) daft one. If in a 3 phase switched fused isolator all phases fuses are in place what is the potential difference between each phase?

 

[Deleted member 9648]

Now I'm going to ask the potentially (pun not intended) daft one. If in a 3 phase switched fused isolator all phases fuses are in place what is the potential difference between each phase?

400v......between 2 phases.

 

[jeremy]

Is there a variation allowed as in single phase +10%/-6%

 

[vambo]

each phase is 230v and is under the same rule.

 

[jeremy]

If the difference between single phase and earth was at the upper limits, 253V, would the difference between phases increase?

 

[johnboy6083]

you will probably get anything from 400v to 420v. about 415v is most common in my experience.

 

[jeremy]

Cheers, thought so! thats probably why the fuses indicate that they're rated for use in a 415V situation!

 

[pmac10]

think of your single phase supply in a high rise tower block. the building has one 3 phase supply, you have 230v LN on your floor but more than likely 415V L1/L2 with the floor above.

 

[jeremy]

Cheers mate!