HELP 3-phase!!!!

supersparks said:
dont forget, this isnt the US,
Noted, that's why I used a 415/240V rather than a 208/120V system in my example.

supersparks said:
i cant realy see that there would be much difference, but i have seen 3 phase alone, with no neutral, and there has been no tranny.
...i always thaught that the idea was that you balance the load perfectly on the phases, so there is no current for the neutral to compensate, so is not needed......
The only way to balance the load perfectly would be to hook up only three-phase devices, such as three phase motors and three phase electric heaters. In these cases the phases can't help but balance (assuming the product was designed well) and you don't have to worry about it.
When using single-phase devices, all you can do is balance it as best you can and live with the neutral current you will inevitably have left over. For this you usually need a star-connected transformer feeding the system, although I have seen center-tapped grounded deltas (but not for this type of application).

supersparks said:
whilst i think about it :eek:ne thing i dont understand is; what do you do with the neutrals from the fittings? do you connect across phases instead of phase-neutral
Do you mean what do you do with the neutral connections on the device you are hooking up to the three-phase system? You don't want to hook up a single-phase device across two phases of a three-phase system, they usually require the neutral conductor to be grounded, and this obviously isn't an option if you're using two live phases. Also don't forget that phase-to-phase you'll be getting 415V, not 240V (line-to-line = line-to-neutral x 1.73).
If we're still under the assumption that we don't have a neutral available, what we'll want to do in this case is hook up a delta-to-star transformer and use the neutral from the star side as the return path for each phase that is powering computers.

Another thing, you don't want hook up a computer to an ungrounded delta system anyway. It's floating with respect to the building ground and the power supply won't like that. A star connection is definitely the way to go here.
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thing is he ony has a 3 phase supply(he said so) , perhaps it is in a building he is beinng "loaned" or perhaps a 3 phase generator
breezer said:
thing is he ony has a 3 phase supply(he said so) , perhaps it is in a building he is beinng "loaned" or perhaps a 3 phase generator
Well, right, but if you take each phase seperately you have three single-phase supplies. You just need a neutral.
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yes, but you seem to be missing the point. The origonal poster said he has only a 3 phase supply i was wondering how i can split a 3 phase supply into single phases and get a neutral from it and but have "played" with mains before shows he is not competant, also if anyone has a 3 phase distribution system they want to lend me for this weekend implies he only wants it for a short time.

all of what you have said is true, (i never said it wasn't) but the poster is just not competant, that is the point so its poitless to say what he can do since he probaly has no idea to what we are refering and in any case he is NOT QUALIFIED TO DO IT anyway
"yankey-sparky" is completly correct in all of his postings, Three phase is not for the DIYer, Having said that, Neither is Single phase?
ban-all-sheds said:
Oh I think that's a bit extreme...

Oops :( Sorry "b a s" I just know that electricity is extremely dangerous, and just because something works does not imply that it is safe to use for the next 20 years or so, I once met a bloke who called himself a "Qaulified Electrician", He said that he knew all about earthing, But when I questioned him, He did not know about "Earth fault loop impedances" Or "Disconnection times", This bloke had also failled his C&G Part 1 & 3, And did not turn up for his C&G BS7671 (2381) Exams,
paulh53 said:
Well they got here quick :eek:

What,these guys are "Qualified Electrician" as well :?:

Sorry,couldn't help it :LOL:
CALL THE PROFESSIONAL (Not The Professionals)

There's always one isn't there :confused:

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