RE: More Ballasting this Danged Transformer :)

["David Dean" <deano-at-corridor-dot-net> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

Hi Ryan,

Actually that is 80 amps to an arc with a voltage drop across it of
something like 20 volts.
The 80 volts is the nominal open circuit voltage of the welder. The short
circuit current will be a bit higher than 80 amps. The thing to do is to
short the secondary of the welder and then measure the primary current
drawn. That will give you an absolute maximum current that can be supplied
to the transformer's low voltage windings when connected in series with the
primary of the welder, and the high voltage windings shorted. Of course more
current could be supplied to a capacitive load, especially if you happen to
get close to a resonant condition between the ballast and the cap you are
charging.

If you could be satisfied with a rougher estimate, you could make a guess
based on the transformation ratio of the welder. Its secondary open circuit
voltage is around 80 V, and its input voltage is approximately 240 V so that
gives a three to one ratio. If the output terminals of the welder were to be
shorted, the current would be "close" to 80 amps, so the primary current
would be about 1/3 of that. Probably not more than 30 to 35 amps anyway.

> Subject: More Ballasting this Danged Transformer :)
>
>
> Original poster: "Ryan Ries" <spud-at-wf-dot-net>
>
> 	Alright, we've decided to power the pole pig using the 3-phase dryer
> outlet.  That's only a mere 10 feet or so to the driveway. (Less extension
> cord = better) Plus, we don't have to make any "uncertified" housewiring
> modifications, and the dryer is on a 40A dedicated circuit.  So far we're
> in good shape.  As for ballasting, we plan on splicing another 3-phase
> recepticle into the extension cord, and wiring it up all *crazy* like so
> that if we plugged an arc welder into that 3-phase recepticle, it wouldn't
> be parallel, but would instead be in series with the transformer.  (We are
> only using the two opposing conductors in the 3-phase system.)
> 	Now, everyone on the list thus far has told me that the
> readings on the
> arc welder will bear no relation to the actual amount of current being fed
> to the transformer.  I understand that, because the markings on the welder
> were made assuming that you were going to be using the primary coil of the
> welder in relation to the secondary.  But, is there not some way to at
> least closely estimate the actual amount of current?  For instance, the
> lowest current setting on the arc welder reads "80 Amps".  80 Amps is
> obviously too much, but that's also assuming 80 Amps at the 80
> Volts coming
> out of the secondary leads of the welder.  At that setting, what amount of
> current would the welder actually be consuming from a 240v input?
>
> 	Ryan Ries
>
>
>