Pole pig testing
Yes my new variac is a Powerstat Variable Autotransformer. 240v in 0 - 280v
out 28A 7.8KVA.
Well, last night I spent about 5 hours testing with the new pole pig. I have
the welder in series with the line side of the variac. The output of the
variac goes directly to the pole pig. This is a completely different animal.
If I did not know better, I would think this is someone elses' project.
Everything is different and confusing. If I would have had your home phone
number last night I would have called you. I think I have taken about five
steps backwards and two forward.
Durring all this testing, I am monitoring the primary current into the pole
pig and the primary voltage. I am still running on my only home made rolled
capacitor so I want to keep the pole pig input under 150 to 166 volts (should
be 9 to 10kv out). The first big difference that I found is in the spark
gaps. When I used to use the neon transformers (12kv -at- 120ma - controlled
to 9 to 10kv max) I used one cylindrical spark gap and it would fire at
about 5 to 6kv. Now I slowly increase the variac up to 150 to 160 volts and
the spark gap will not fire. I tried two gaps in parallel and they will just
barely fire. Finally I used one gap electrically folded in half and it will
fire at about 130 volts - should be about 8kv - but when it's running, it
sounds like it's tearing the hell out of the gaps. These gaps are 7 2.0"
dia copper pipe sections about 2.5" long and gapped at about .030". Then I
tried both gaps in series each folded in half. Now it just barely fires at
about 10kv. Then I tried both gaps folded in half and in parallel. This
doesn't work very well. They won't consistently fire together. It seems to
go back and forth, first one then the other will fire. I finally ended up
just running one gap folded in half.
The next big difference I noticed is when the gaps are firing, no sparks
break out from the coil. I have a neon tube hanging from the ceiling and I
noticed it was glowing so I tried setting a socket on top of the discharger -
using the large 33" toroid at this point. If I provided a ground wire about
30" away I got hot white discharges. Hotter and louder than I ever heard
with the neons. I tried changing the tuning on the primary and this did not
help. I suspect I am now getting a lot more current into the primary of the
coil now but less voltage.
You are correct, this pole pig is very difficult to control. The variac acts
like an on/off switch only. I can control the voltage up until the spark
gaps fire then I have no control. As I ramp up the variac, the voltage on
the pole pig primary goes up to about 130 - 140 volts, current is only a few
amps at this point, then the spark gap fires, current jumps up to 25 to 30
amps and the primary voltage drops down to 80 to 90 volts. This should be
only about 5KV out of the secondary. If I turn the variac up higher, it
seems like the current goes up a bit but the voltage across the primary
actually goes down. What it seems like is I have control of the current but
not the voltage. How do I get the primary voltage up to say 150 while
holding the current to 20 to 30 amps??? I tried a 2000w resistive load and
got weak sparks and only 6 or 7 amps in the primary.
I finally switched dischargers - back to my original 14" toroid. I get a
fine fireworks display. Many violet discharges about three feet long. A
good display. The primary voltage is still only 80 or 90 volts.
I think I finally have a setup similar to yours - without the rotary gap.
How do you ever get the primary voltage up? Do I need to add resistive
loading in parallel with the welder? You said it is possible to eventually
eliminate the welder, which is good, we will need it back at work some day.
I think if I had the variac, the pole pig and the line hooked up with no
load, the current would go through the roof.
It's fun - but help.