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Re: [TCML] First (or maybe 2nd) light on my medium-sized SG coil, PT current rating?
Hi David,
I have a PT driven coil of approximately the same configuration as yours. My PT is ballasted by an inductor wound around some transformer core material. It has taps to allow changing the amount of inductance. I am able to run the coil with a 20 Amp breaker. My tank cap is 0.035mF MMC. Perhas using a larger cap is what is drawing so much current.
I also have used a section of dryer heater element in series with the inductor. From reviewing some of Richard Hull's material, it was reported that a resistor/inductor gave a smoother running coil. I didn't see too much difference.
My coil streamers are ~ 64" max. I have some chicken wire on the trusses in my garage above the coil to keep the arcs off the house wiring. I remove the circuit board from the door opener as a precaution after blowing the original and paying $90 for a new one.
Jim Zimmerschied
----- Original Message -----
From: David Rieben<mailto:drieben@xxxxxxxxxxx>
To: Tesla Coil Mailing List<mailto:tesla@xxxxxxxxxx>
Sent: Tuesday, April 15, 2008 10:21 AM
Subject: RE: [TCML] First (or maybe 2nd) light on my medium-sized SG coil,PT current rating?
Hi Jim,
My PT is just a regular run-of-the-mill 1.5 kVA rated (@ 30*C)
120:1 GE potential transformer. However, I have found PTs to
be VERY conservatively rated since they are rated to put out
their rated VA output with essentially zero voltage drop. After
all, they are designed for metering a known fraction of primary
line voltage so voltage accuracy is important. For this reason,
most PTs can put out several times more VAs than their name-
plate rating suggests. Of course my PT is made for 120 volt
input, unlike your monster 5 kVA unit with a 240 volt input.
Turth be told, you could probably run up to 20 kVA+ through
that 5 kVA PT of yours if you kept the uninterrupted run times
within reason! BTW, if you want to go even bigger on the
transformer, why not just upgrade to a pole pig as they usually
run much cheaper than equivalent sized PT combos?
With that being said, my PT is running fine but I am finding it dif-
ficult to "hold the reins" on it to keep the current draw within the
limits of a standard 20 amp line service. I suppose running with
2 paralleled MOTs with their secondaries shorted as a ballast
is what's taxing the electric service. You have to remember too
that I have done gotten spoiled to the 12 to 14 ft. super bright
discharges of my Green Monster coil running of up to 90 amps
at 240 volts input and fired with a pole pig. I took on this project
to have a coil that I could run off a standard 120 volt service
but I still want to get all of the "bang for my buck" that I can
muster ;^) I am already getting 50 to 60" arcs with the variac
only set at about 50 to 60 on the dial but if I try to roll it outside
and push it further, it will pretty quickly trip the 20 amp panel
breaker. That's why I was wondering about how much PFCs
would help to hold down the current draw. I suppose that I could
also cut back to one MOT and then be able to turn my variac knob
up higher.
I also think that my .08 uFd primary C along with a relatively
monsterous 6 x 30 top-load is also really sucking the amps for
a standard 120 volt service :^) It seems that a 6" coil is about
at the size limit for firing at its full potetntial from a standard 120
volt, 20 amp electrical service.
--
David Rieben
-------------- Original message --------------
From: "Jim Mora" <wavetuner@xxxxxxxxx<mailto:wavetuner@xxxxxxxxx>>
> Hi David,
>
> -----Original Message-----
> Hello David,
>
> What is the current output of the PT? I have a 5KVA GE that I am planning on
> running on my 8" coil also wound with #22 to 35.5" so your results are
> interesting to me! I plan to use a smaller sat reactor and a combo static
> and dc motor rotary gap. This PT runs on 240v. I wish I had two of em!
>
> Jim Mora
>
> From: tesla-bounces@xxxxxxxxxx<mailto:tesla-bounces@xxxxxxxxxx> [mailto:tesla-bounces@xxxxxxxxxx] On Behalf
> Of David Rieben
> Sent: Monday, April 14, 2008 5:25 PM
> To: Tesla list
> Subject: [TCML] First (or maybe 2nd) light on my medium-sized SG coil
>
> Hi all,
>
> I have finally gotten my mid-sized SG coil project up and running
> A quick rough-up of the specs are about 28" of #22 AWG magnet
> wire wound on a 6" ID (6.5" OD) white PVC pipe for the secondary
> coil. The primary is 11 turns of 3/8" copper tubing wound in the
> classic Archemdian spiral with between 3/8" and 1/2" spacing be-
> tween each turn and the outermost turn has about a 12.5" radius
> (25"diameter). After initial tuning, the primary has been tapped at
> approx. 8 3/4 turns. The transformer is a 120:1 GE potential trans-
> former (14,400 volt output).
>
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