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Re: Repost: NST VA Rating and Power Factor

Original poster: "Bill Vanyo by way of Terry Fritz <twftesla-at-qwest-dot-net>" <vanyo-at-echoes-dot-net>

Tesla list wrote:
> Original poster: "Jason Petrou by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <jasonp-at-btinternet-dot-com>
> >  My power supply consists of three 15/60 NST's.  Two are Franceformers,
> >  and are marked 495 VA, and also have "High Power Factor" on the label.
> >  The other is a Magnatek/Jefferson, marked 900 VA.
> If you do the math (15000V*0.06A) you get 900VA - which is what it should be
> for all 15/60 NSTs. I have no idea how you have got just under half that for
> the franceformer ones... it is technically impossible :) I'd recheck the
> labels, and if you are still lost measure the Vout of the secondary, then
> short out the secondary and measure the current flow, and also measure the
> current out of the mains socket. I think that the xfmr must be labeled
> incorrectly. I dont know what the High Power Factor means - i'd check with
> the company (or wait for other replies from the list

Here's a link to a two page PDF file from the manufacturer. Page 2 lists
"normal power factor" and "high power factor" models, and the ones I
have are model 15060 PC.  If you compare their 15060 P and 15060 PC
models, the only difference is Primary VA (890 vs. 495) and Input Amp
(7.72 vs. 4.13) (and 3 lbs weight difference).


> >  Also, regarding the problem of tripping the house breaker (It was on a
> >  15amp breaker, but there is a 20amp available that I'll try next time):
> >  I've got a 240 volt line in my garage (20 amp breaker).  If I use my
> >  variac to step this down to 120 volts, will I be able to draw more
> >  amperage?  The variac is 240 volt 50 amp, and has multiple terminals,
> >  and I think there's a way to use it as a stepdown (other than just
> >  leaving the dial at 50%), though I'm not sure how to do this (asking in
> >  another post).
> If you didnt already get a reply to this...
> If you have a 240V supply and step down to 120V you will get more current
> provided your step down tranny can handle it.

It's a 240 volt 50 amp variac, so I think it can handle it.  Now if I
can just figure out which connections to use on the variac to make it
step down 240 to 0 to 120.  I think it can be done - there are several
connecting posts, but I have no documentation on the variac.  I posted
this question in another post.  I'd repost that too, but I suspect it's
more arcane of a question, and not likely to get an answer.  :(

> That way you can use american
> NSTs on a british supply, and more of them to boot. However if you use a
> british NST with a Vin of 240, you will get half the voltage out of the
> secondary but no more current (they are current limited). Same, if you plug
> a 120V tranny into 240V then for a short while you will get double the Vout
> from the secondary. However 2 things could happen... 1) the primary core
> saturates and the Vout of the secondary drops drastically as the primary
> stops conducting. 2) the insulation on the secondary would break down due to
> corona from the wires.

I want to use multiple american trannies on a 240 line (we have them
here in the US, for things like electric stoves and elctric clothes
dryers), stepped down to 120, for the sole purpose of being able to
parallel three or four 15/60's (I have three now, looking for fourth)
without tripping breakers.
> Good luck, sorry aobut the l8ness of my reply
> Jason