ROTARY AND PIG TESTING
Subject: ROTARY AND PIG TESTING
From: richard.quick-at-slug-dot-org (Richard Quick)
Date: Mon, 22 May 1995 03:32:00 GMT
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Quoting Ed Sonderman:
ES> After we talked last night, I did some more testing. I can
ES> get a good jacobs ladder with the pig transformer by using
ES> resistive loading only.
Yeah. The Jacob's Ladder is trickier with inductive ballasting.
The inductive delay plays havoc with the Jacob's Ladder arc
getting smoothly going.
ES> Using a 2000W heater the ladder works and I get 10A primary
ES> current. Using about 5000W I get about 27A primary current
ES> and a nice hot arc on the ladder. The arc does go up the
ES> ladder and it is hot. If I run it too long the brass rods
ES> get so hot they start to fall over. I think the pig is
ES> working fine.
Sounds like. The Jacob's Ladder is working just fine. This is one
of the best ways to test a Tesla power supply.
ES> As I mentioned, I ran the rotary with two 12kv 30ma neons
ES> and the rotary works good. Limited to 10,000V I get about
ES> 20" discharges. So the rotary and the pig are both ok.
OK, I would concur with this.
ES> Next I connected the pig back up to the coil with 7000W of
ES> resistive load and the welder out of the circuit. Using the
ES> rotary gap only I do get consistent firing.
OK, got it so far.
ES> Limited to about 10,000V I get 10A of primary current and
ES> about 20" discharges. Since I'm now supplying about 150ma
ES> of current to the coil primary circuit I would expect to get
ES> much better performance than I had with the two 12kv 30 ma
ES> neons. Do you have any ideas?
My numbers come up about the same as yours. You are feeding the
primary of the pig about 160 volts -at- 10A = ~1.5 kVA actual into
the tank circuit. I would expect 3+ feet of discharge at this
power level. Thoughts:
Is the rotary gap running too fast or two slow? Gap speed can
really alter the power processing performance of the system.
The capacitor is not able to process all of this power across the
dielectric. This capacitor (.02 ufd) will only process about 75ma
across the dielectric. Increase the capacitor value, or increase
the voltage. (I know, I know, I have been there :-)
Input voltage is probably too low, and combined with the
inductive delay of the welder, the initial power up may not have
the voltage and current to get the gaps up and firing reliably.
Remember that it takes nearly a full second from the time the
gaps fire, to the time the current is able to pass though all of
the copper and various cores, to show up in the tank circuit
proper. The inductive delay plus low operating voltage is likely
part of the problem.
Keep your sense of humor. I am not seeing any basic flaws or
problems. While the exact cure is escaping me, the problem would
seem to be a minor one.
ES> I also tried the same setup only with a static gap in series
ES> with the rotary. The performance was not as good.
This is telling you that the working input voltage is too low and
that the gap system (rotary with static gap in series) is
providing too much gap distance and quench for this input voltage
and power level. The series static gap will be desirable as power
levels climb up to around 3 - 5 kVA.
ES> When doing this testing, sometimes I hear a loud pop from
ES> the rotary. I don't know what is causing this.
Rotor vibration would be the first thing I would check. It may be
detectable only at speed. Fix a piece of carbon paper to each of
the stationary electrodes. Run the gap up to speed and back down
a few times (coil off). If you don't hear a pop, and the carbon
paper leaves no indication of contact, you may be hearing
kickback in the gap.
ES> So far, I still have had much better performance with a 12kv
ES> 120ma neon power supply than with the new pig. This thing
ES> is indeed difficult to figure out.
Hey, what are hobbies for?
ES> Can you give me a detailed description of your setup?
ES> Rotary, static gap, welder, resistive loads, etc. At what
ES> variac setting does everything start to work well? My pig
ES> should put out 14,400v but I have never had it up over
ES> 10,000v when connected to the coil.
OK, the first big difference is the pig I use for my 10 inch coil
is a 22890 volt secondary. I am running much higher voltages. I
also have a 50:1 pole pig (25kVA) with a 12,000 volt secondary.
It is much more difficult to work with as my gap experience tends
to be with higher voltages. I can get it to work, but believe it
or not, my higher voltage pig is easier for me to quench. The
lower voltage pig seems to require a closer, more precise, gap
setting. Of course this close and precise gap setting must handle
about four times the current to process the same amount of power
at 12,000 volts.
With the 22890 volt pig the gaps fire easily and reliably when
the variacs are opened up about two-thirds of the way (about 160
volts input to the pig primary). With the 12,000 volt transformer
the gaps will not fire at all unless I reconfigure them. Once
reconfigured for the 12000 volt pig the variacs must be opened up
nearly all the way (200+ volts into the primary) before I get a
reliable gap fire.
The welder I am using is a Medco "Big Red" with a patented
variable shunt. The primary on the welder is rated 60 amps with a
5% duty cycle at maximum amperage. When running the 22890 volt
pig I use the welder alone. On the 12000 volt pig the inductive
delay is a serious problem (the core of this pig is rated 25kVA)
so two 1000 watt Magic Chef oven elements in parallel are used in
series with the welder to smooth things out without too much
The 12kv pig seems to work best with just the rotary, no static
gaps, 500 watts of resitive ballast in series with the welder,
and the variacs opened all the way up. It tends to cook my
electrodes on the rotary.
I hope you can get this problem figured out. My guess would be
that once you get some higher voltage capacitance on line and can
bump up the input voltage some, this should straighten out.
Anybody else have any thoughts?
... If all else fails... Throw another megavolt across it!
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