RE: [TCML] 6 MOT stack?

[Yurtle Turtle <yurtle_t@xxxxxxxxx>]

I think you can get away with 5 kVA on a 4" coil:

http://www.classictesla.com/hot-streamer/adam/sparks.jpg

Though you may have a few problems along the way if you aren't careful:

http://www.classictesla.com/hot-streamer/adam/burnt_mmc.jpg

Cheap resistors

http://www.classictesla.com/hot-streamer/adam/burnt_primary1.jpg

Gotta watch those primary strikes

http://www.classictesla.com/hot-streamer/adam/burnt_secondary.jpg

This happened on the far side of the coil, where it wasn't visible

Adam


--- On Tue, 6/2/09, S&JY <youngs@xxxxxxxxx> wrote:

> From: S&JY <youngs@xxxxxxxxx>
> Subject: RE: [TCML] 6 MOT stack?
> To: "'Tesla Coil Mailing List'" <tesla@xxxxxxxxxx>
> Date: Tuesday, June 2, 2009, 9:23 PM
> Jeremy,
> 
> Yes, there is no substitute for more power for longer
> streamers.  But with a
> 23 inch secondary, 2 KVA is probably about all it can
> take.  You will need a
> longer (& wider) secondary to handle 5 KVA.
> 
> I run a 6 MOT stack, centrally grounded, with all 6 MOTs
> immersed in
> transformer oil.  The oil is the key to survival of
> the outer two MOTs at
> the high primary to core voltages, and all of them by
> helping get rid of the
> heat.
> 
> The archives are full of ballasting ideas, ranging from
> using a welder in
> series with your stack, to using a reel of #10 wire, to
> winding your own
> iron core inductor, to using more MOTs with the secondaries
> shorted.
> 
> Personally I prefer not using any ballast and instead
> rectifying and
> filtering the output of a MOT stack, then using DC resonant
> charging with a
> variable speed rotary spark gap.
> 
> You might also consider eventually going solid state, e.g.
> DRSSTC, which
> avoids the need for high voltages completely.
> 
> Steve Y.
> 
> -----Original Message-----
> From: tesla-bounces@xxxxxxxxxx
> [mailto:tesla-bounces@xxxxxxxxxx]
> On Behalf
> Of Jeremy Chan
> Sent: Tuesday, June 02, 2009 7:08 AM
> To: TCML
> Subject: [TCML] 6 MOT stack?
> 
> 
> Greetings to all,
> I have recently completed the construction of my first
> coil. It has a 3ft by
> 3ft primary with 17.5 turns, a 4.5'' by 23'' secondary
> wound with 22.5 AWG
> wire, and a 6.5'' by 16'' torroid. The primary and
> secondary is supported on
> a 4ft by 4ft 12mm plywood board, supported over a second
> lower deck by 8
> threaded rods, which houses my circuitry. The whole set-up
> is mounted on 6
> 3'' diameter castor wheels so the thing is mobile.
> There is no problem with this set-up, in fact it is an
> over-kill where it
> comes to most aspects such as the supporting structures and
> wires etc. The
> problem is that i am currently running the whole thing off
> a 15/30 NST (the
> best thing i could find in the pathetic island country of
> Singapore), which
> effectively supplies 225W to a coil which I believe is more
> than capable of
> handling 5kW. Thus far, I have only maxed out 20cm sparks
> no matter what I
> tried (save for increasing the safety and master gaps, cos
> i can't afford to
> kill my only precious 15/30 NST). Angling the primary to 45
> degrees to
> increase coupling seems to offer no appreciable advantage
> over a flat
> Archimedes spiral, and the optimal primary turn has been
> tapped at turn 12.5
> I have thus come to the conclusion that I simply need more
> power. Since,
> once again, over-head power lines are non-existent in the
> wonderful island
> country of Singapore, pole pigs are non-existent as well;
> and there's no way
> I will be able to draw enough power to supply a 200kVA pad
> mount transformer
> in my neighbourhood since my neighbourhood is probably
> powered by 1 of those
> in the first place... The next best thing would be MOTs,
> a.k.a. the 'mini
> pole pigs'. I have a dozen of them aching to be used, 6 of
> them appearing to
> be of the same model, which is a good thing. The bad thing
> is that I have no
> idea whatsoever how ballasting works. I am a Chemistry
> major in university,
> and the coil construction was already stretching the bounds
> of my electrical
> engineering experience. I do know that an unballasted MOT
> puts out about
> 3500W of power before burning out after 5 minutes, and a
> ballasted MOT puts
> out about 1kW. But I need to know how to ballast a MOT
> stack for about 5kW,
> whether capacitively or inductively. Programmes for
> calculating circulating
> currents as well as trans/cap matches would be much
> appreciated. 
> I considered a 4 MOT stack initially, but am concerned if
> it can handle the
> full 5kW for prolonged periods, and the 8400V supplied
> seems low for a 5kW
> coil. Then again, with a 6 MOT stack I am worried that the
> MOTs at the
> extremities might not be able to handle the 6300V even with
> the stack
> centrally earthed. Does anyone have any experience or
> advice on these
> matters?
> Any advice would be much appreciated.Merci Beacoup,Jeremy
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