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Re: Getting more input power
Original poster: Zagarus Rashkae <arbitrarily_random-at-yahoo-dot-com>
Hi Ian,
Comments within...
> Hi all,
>
> I have been talking to my electrician about getting
> a 50A feed into my
> workshop.
> He has informed me that this is usually done with a
> 3-phase connection. I
> should have pressed him for some more questions, but
> forgot, so I'll ask the
> knowledgeable people on this list.
Three-phase is great for DC coiling if you can get it,
and don't mind the extra cost of the rectifiers.
>
> My knowledge of 3-phase power is sketchy, whilst I
> do understand the basics.
>
> If the outlet is rated at 50A 3-ph, then how much
> power is available per
> phase (to neutral) ?
Usually if it says it's 50A, it's 50A per phase
meaning a total of 3 * 50 * 240 = 36kVA, IIRC.
>
> If it is 1/3 of 50A that is OK, I could split the
> power - use one phase for
> the HV supply, and another for the RSG - but this
> raises a major issue. The
> RSG will be out of phase with the HV supply by 120
> or 240 degrees depending
> on which two phases I use. Is there any way of
> adjusting this with some
> sort of phase angle adjustment. The JF phase
> adjuster can only manage about
> 90 degrees or so I believe.
For large adjustments of RSG phasing you can simply
rotate the motor in its cradle. Smaller adjustments
are best done with a phase adjuster while the TC is
running so you can look for best phasing.
>
> I wonder how my NST's would cope if I connected them
> between phases ? This
> way they would be getting 415VAC, not 240VAC - and I
> wonder if the
> insulation in the tranformers could cope with the
> higher voltage. Anyone
> tried this ? My guess is .. no way .. we would be
> upping a 15kV tranformer
> to nearly 30kV, and we all know this is about the
> dialectric strength of
> air, and the first real problem point for insulation
> breakdown and corona.
NSTs are pretty harshly abused in TC duty anyway and
it cannot take the extra stress! Nearly dobling its
rated output voltage will certainly kill it quickly.
>
> Rgs
> Ian
>
>
Regards,
Chris Lu