Re: OLTC Update - The baby has arrived :-)))

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Brian by way of Terry Fritz <twftesla-at-qwest-dot-net>" <ka1bbg-at-webryders-dot-net>

AWESOME! cul brian f.
----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Monday, August 26, 2002 3:24 AM
Subject: OLTC Update - The baby has arrived :-)))


> Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>
>
> Hi All,
>
> Our local Tesla meet was tonight and I barely got everything together and
> thrown into the car to Denver.  Lots of last minute stuff...  I got some
> thick poly sheet on the way since primary to secondary arcs were a problem
> yesterday.  On the way down, I decided to run it till it explodes :o))
>
> So we got there and set it up in Bill's lab:
>
> http://hot-streamer-dot-com/temp/OLTC08-25-01.jpg
>
> Note the poly sheet and raising the secondary modifications.  This was
> after the primary to secondary arcing punched a hole clean through a sheet
> of 3/16" G-10 (brand new too!).  The dielectric properties of G-10 allowed
> enough leakage current to carbonize a path "through" the G-10.  The many
> layers of poly act like many caps in series so there is very little
leakage
> current.  A great trick!!  After these mods, the coil worked perfectly
with
> no arcs.  I think the coupling neared the optimal 0.095 for this coil.
>
> I was a little worried since reviewing the flight tape yesterday suggested
> that the coil was damaged buy the "odd sound".  The output decrease
> instantly with the sound.  As it turned out, it was just corona spraying
on
> the back side of the coil.  There was no damage after all ;-))  That
shrink
> wrap is wonderful stuff!!  What IS that stuff anyway??
>
> Earlier in the day, I had added a cap to my Tesla Coil Tuner (TCT) so it
> could work with a low frequency coil like this and calibrated it with the
> frequency counter function of the HP meter.  I could simply tune the coil
> by raising or lowering the toroid on the brass all-thread rod.  So I tuned
> the secondary about 5% low, which as I write this, I realize was incorrect
> =:O  Arauugh!!!!  Should have been 5% high and the streamers would have
> brought it down...  So the darn thing was about 10% out of tune >:-P
>
>
> So we ran it off the variac slowly adding more and more power.  It easily
> lit all the florescent lights in the room as shown here:
>
> http://hot-streamer-dot-com/temp/OLTC08-25-05.jpg
>
> Soon, I had weaned it from the variac (and high power limiting resistor)
> and it was running in it's full "low power" mode!  It was now a true
> transformerless Tesla coil running as a 35 pound unit.  The controllers
and
> all worked perfectly!  The IGBTs were running at about 2500 amps.
>
> Here is the schematic of the system:
>
> http://hot-streamer-dot-com/temp/OLTC08-25-02.gif
>
> The sparks were a little short:
>
> http://hot-streamer-dot-com/temp/OLTC08-25-03.jpg
>
> But there were sparks and a heck of a lot of "power" that filled the room.
> I could kick myself now for screwing up the tuning thing but...  The heck
> with it ;-))
>
> The power of the coil was "ferocious".  None of the usual "let me touch
it"
> folks wanted to go near it :o)))
>
> http://hot-streamer-dot-com/temp/OLTC08-25-02.jpg
>
> It was like burning the aluminum tape off and pitting the aluminum toroid
> :-))  Seemed to have low voltage, but very high current, arcs.  I thought
I
> may have messed up the coil's output impedance, but now I think it was 10%
> out of tune :-p
>
> Here is some testing at full power (still, just off the weenie 120VAC...)
>
> http://hot-streamer-dot-com/temp/OLTC08-25-06.jpg
>
> This is after we had optimized the dwell time with a wooden stick attached
> to the controller dial.  It was really cool and had a giant blue glow that
> the picture didn't capture well.  The arcs were about a foot and a half.
> The dwell time was only 45uS and the arcs seemed "short", but with my darn
> tuning error...
>
> Here we are frying a Microsoft CD :-))
>
> http://hot-streamer-dot-com/temp/OLTC08-25-04.jpg
>
> So there was a bad tuning error but all else went just fine.  The
> controller did perfectly.  The IGBTs ran at 2500 amps just fine.  Messing
> around with the dwell and all proved that the transorbes and all the
> protection circuits work just fine.  Everything came home alive and well
> :-))  If wee "could" have blow the electronics, they "would" have blown...
> Sorry Marco, my dead IGBT bucket is still empty :o)))  Bill did not have
> 240VAC available (probably a good thing :o)) but at 120VAC the OLTC seemed
> to run just fine.
>
> Much to ponder... But not as much as it "could" have been :o)))
>
> So, now, there is now doubt, the OLTC is born!!! :-))))))
>
> Cheers,
>
> Terry
>
>
>
>