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RE: First Light for 10" Coil.



Original poster: "Peter Reid" <peter-at-reidconsulting-dot-com.au> 

Hi Ted.

I'll answer your questions as best I can!

All 6 of my MOT's are fully immersed in oil as well. I'll post a new
photo showing the setup and how they are connected etc. But basically
they are phased above ground like yours. I only ballast the input to the
MOT's, The ballast is constructed with 170-180 turns of 6mm wire wound
around a 65mm PVC tube, split across 4 layers. I managed to get hold a
about 20kg of welding rods, for about $20, they were water damaged. I
stripped the flux off them grouped them all together and potted them
with a casting resin, in a bit of spare 65mm pvc tube, I used silicon
spray to line the tube to ensure easy removal of the core once it was
set.

I haven't measured the exact inductance range of the ballast, as my DMM
only measures down to 10mH, It can be calculated pretty easily though.

With the core fully inside the tube the mains current with the MOTS
shorted is just under 20A, with the core fully out it's about 70A. There
is no noticeable heating in the core of the inductor; however at high
current runs the windings get a little warm after a while. The inductor
hardly makes any noise all in all I am really happy with it, considering
how much it cost to make.

Last run of the coil I managed to get consistent 9.5ft (3 meter) power
arc's to a ground rod while sucking a tad under 40A from the mains
(ballast core raised about 20cm).

With regards to the bps & firing angle, I first tried 400bps vs 200bps
and found that the coil performed much better at the lower break rate,
however in your situation I would guess that since you're running 90nF
300bps would be better. I just use the remote phase adjuster I have
built to adjust the phase as its running, after the first run I found
that the optimal phase shift was about 80% of the way around on my
variac, to fix this I shifted all my brass electrodes by one hole
(45deg), in essence adding a 45 deg phase shift. Now it tunes around
10-50% depending on ballast setting.  All electrodes are spaced 90 deg.
With holes at every 45 deg.

One thing I have noticed is that its really important to run a very
small safety gap spaces on your transformer safety gaps MOT's can handle
over current easily but over voltage is another story, Also I start
having all sorts of problems if the SRSG gap gets too wide especially at
higher power levels.

I've managed to get my whole set-up to run on a circuit that is feed
though a 30mA RCD without it tripping :) Initially I couldn't get it to
run for more than about 0.5sec, once I ironed out all the bugs it didn't
trip anymore.

I hope that helps a bit, have you got any photos of your current set-up
/ sparks? I'd be really interested to see them if you do.

Regards

Peter Reid.


-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Wednesday, 24 December 2003 3:47 PM
To: tesla-at-pupman-dot-com
Subject: Re: First Light for 10" Coil.

Original poster: tesla <tesla-at-paradise-dot-net.nz>

Greetings Peter

A most interesting coil and quite similar to my own

Very interested in the way you have done things

The differences
Mine has 90nF of the 1600v 0.33uF caps (like Robin Copini)
SRSG is currently 300bps and all electrodes are near the 90deg and
270deg
points. This needs fixing, How did you decide on the location for your
rotating electrodes to set timing

I use PFC of over 100uF and up to 6 MOT's. The MOTs I have are in oil
and
phased about ground. I use 900watt xfrmrs. I run fixed ballasting of
22mHy.
I was intrigued by your ballast and would be interested in the short
form
specs on that.

I have just purchased the bits to put a dedicated outlet at the house so
should be able to run the thing flat out.

My operating freq, toroids and so forth are pretty similar, I can maker
the
beast do 2 metre O/P but I know it will do better when I get SRSG timing
better and a dedicated mains. It will run > than 40amps if I let it so
need
to keep it at that level or things start to go wrong, like fuses start
to
blow.

Hope to hear more from your expts

Rgds
Ted L in NZ
----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Wednesday, December 24, 2003 8:54 AM
Subject: First Light for 10" Coil.


  > Original poster: "Peter Reid" <peter-at-reidconsulting-dot-com.au>
  >
  > Hello Everyone on the Tesla Coil Mailing List.
  >
  > I have just finished building my new MOT powered 10" Coil and managed
to
  > tune it somewhat. I am quite happy with the results so far, however I
am
  > wondering if anybody could shed some light onto areas I should work
on In
  > order to improve the spark length and power handling capabilities of
this
  > coil. So far I have managed occasional 8.5ft Power Arcs to a grounded
rod.
  > However I feel that the coil is still capable of a lot more.
Initially the
  > spark output was quite poor until I increased the coupling between
the
  > primary and secondary. (I don't think I've gone too far).
  >
  > I will list the specifications below. With the current setup I am
getting
  > quite powerful arcs to the strike rail and ground with-in about a 3ft
  > radius around the coil.
  >
  > I have posted some photos on my website for anyone that's interested.
I
  > also have some pretty good video footage, but that isn't on the
  > webpage.
  >
<http://tesla.reidconsulting-dot-com.au/>http://tesla.reidconsulting-dot-com.au
  > Any input / help with improving the current setup would be greatly
  > appreciated, I am just a little worried about burning up my secondary
if I
  > try and pump any more power though it.
  >
  >
  >
  > Coil Specs are as follows..
  >
  > Primary
  > Flat Spiral, Wound with ½ In Copper tubing, spaced but ½ inch.
  > ID = 12.7in
  > OD = 32.5in
  > Turns = 10.25, tapped at about turn 6.15
  > Primary sits 1.5ft above the ground on a specially made wooden
platform.
  > Strike Rail = 1/2copper tube raised by ½ inch around outside of
primary.
  >
  > Secondary
  > Wound on a 10" PVC pipe, which has been baked and sealed with many
coats
of
  > polyurethane.
  > Winding length = 41in
  > Wire Diameter = 0.9mm B&S Gauge 19
  > The bottom turn of the secondary is elevated 1 inch above the top of
the
  > primary winding.
  >
  > Toroid
  > 12" x 42.5" (Tube Diameter x Outside Diameter of Toroid)
  > Mounted 12in above the top winding on the secondary.
  >
  > Measured Res Frequency of Secondary is 84.8kHz, and primary has been
tuned
  > to exactly that. (Can someone please tell me if its worth trying to
detune
  > it by 1/3 of a turn to account for streamer loading etc?.)
  >
  > Capacitor
  >              0.15uF MMC Cap Bank made up of 144, 942C20P15K caps.
  >
  > Power Supply
  >              6 MOT Supply, Currently Ballasted to 40A -at- 240V (Using a
  > Sliding Choke Balast)
  >              Maximum line draw current of 80A -at- 220v when the ballast
is
  > removed. That's 17.6kVA J
  >              Approx 12kV output.
  >
  > Spark Gap.
  >              200bps Sync Gap, with a Remote Phase Adjuster.
  >              Single Gap, Tungsten static electrodes, and 4 x 8mm
brass
  > threaded rod (moving electrodes) Spinning on a 12in
  > G-10 disc (3000 rpm) Gap spacing is about 1-2mm total.
  >
  >
  > BTW, Thanks to everybody who has contributed to the mailing list, the
help
  > I have received from you guys has been invaluable.
  >
  >
  > Regards
  >
  > Peter Reid.
  >
  >
  >