RE: Getting Closer to First Light with 10KVA Pig

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

Hi Ryan

What is the nameplate data on your pig?
Does it have a high voltage switch on the side of the can?
Normally there is a switch for the high voltage, if it is a dual voltage
transformer.

A lot of times the voltage rating is stated for different applications, like
14400/24940Y.
The Y voltage is for one transformer (of three) used in a Y configuration,
that is for a three phase installation. For single phase the first number is
the one that means something. Mine is a 5KVA, 120/240, 7200/12470Y X
14400/24940Y. With the switch set at 14400, it gives 14400 out whether the
input is 120 or 240 as long as the correct input lugs are used.

When I first got it, I connected the output (welding) leads of a
generator/welder directly to X1 and X2 (120V input). The output of the
welder is about 80V open circuit, and 20V at 180A. I used copper tubing to
make a Jacobs ladder between the high voltage bushings. Then I went to
resistive ballast as I did not have a variac that could handle the current
and that limited voltage as well as current, to a small degree. Now I just
use a welder (pri of welder in series with low voltage windings of pig) and
a big variac to control it all. I run my welder at the lowest current
setting (shunts all the way in) and the secondary open, NOT SHORTED AS IS
FREQUENTLY RECOMENDED, and still am burning too much power in the SRSG, not
enough current limiting going on. Shorting the secondary of the welder just
makes more current flow, not a good thing.

I have yet to need anywhere near 5KVA. My 4" coil has used up to 2.5 KVA
without problems, but that is all the power it can handle. Any extra power
just gets burned in the gap, and that usually means a drop in performance as
quenching is adversely affected.

Personally I would recommend using some resistive ballast to start out with.
Get a "feel" for what is happening with the current limiting before you try
to go all out with inductive ballast. Resistive ballast wastes energy, but
it is smooth and predictable, inductive ballast can give some surprising
results if you happen to hit a "sweet spot". It can very easily over volt
the caps due to inductive kick etc.

You said that your pig is 120/240 14400/28800. If that is true, then
inputting 240 to the X1, X3 terminals will output 14400 if the switch is set
for 14400, or 28800 if the switch is set that way.
If the transformer does not have a switch, then it will have to be set
internally. This information is on the nameplate.

OK, lets pretend that the transformer does not have a switch. You will need
to know the turns ratio to see where it is set. That is easy. just hook the
high voltage bushings to a low voltage source, a variac comes to mind, and
measure the output voltage across the _low voltage_ terminals (outer 2, that
is X1, and X3 leaving X2 alone). If you put 120VAC into the _high voltage_
terminals and read 2 volts between X1 and X3, you are set for 14400 or 60 to
1. If you read 1 volt, then you are set at 120 to 1 which would give 28800.

Let us not worry about ballast at this point, lets just find out what you
have really got there first. Am attaching a picture of my nameplate for
reference.

Original poster: "Ryan Ries" <spud-at-wf-dot-net>

	Well, we're getting closer to lighting up our Veretus coil with the new
transformer, but there are still some heavy preparations to be made.  First
of all, when I asked about the ballasting with a welder, you told me that
the current scale on the welder will probably bear no relation to the
actual current going to the pig.  As such, does anyone out there have a
high-power (100amp) ammeter to sell?  Fortunately, I found a surplus of
oilfield wire, it has three insulated conductors in it, all 8 or 6 gauge
solid copper.  It has very hefty rubber insulation on each conductor and is
all coated with another layer of all-weather rubber stuff, and is topped
off with flexible metal conduit stuff.  I imagine this cord would have cost
a fortune if I didn't have so many "connections". :)
	Fortunately, I have some experience in residential house wiring, because
my breaker box is plum full.  What I want to do is install a secondary box
and feed it with a breaker from my main box.  I've been looking around,
because I don't want to spend $40 on a 100a breaker, but I think I may have
to.  What I plan to do is feed the pig with 120v, up to 84 amps.  The
reason why I am so insistant on using 120v is that if used 240v, the output
of the pig would be over 28Kv, and my capacitors could never handle that.
($$$$ Not having any money can be a real pain. $$$$$)
	Anyway, thanks again, and I'm sure I'll have another slew of questions
after this message is answered. :)