Thread-topic: [TCML] Looking for suggestions on tuning.
If you're gap runs at 1800RPM and fires twice a revolution you have 60bps, this is just every half cycle. Normally the lowest rate is 100/120bps (50Hz/60Hz respectively).
Does it actually fire four times per revolution?
If your 27nF cap charges to say 20KV (assuming peak alignment of spark with no inductive kick), you have 5.4J per bang, and an average power of 320W. If you were generous and assumed an inductive kick which effectively transfers all the power from the unused half-cycle, you might get up to ~10J/bang and 600W.
For that power level 4-5foot sparks is pretty good.
As David says, for larger sparks you need to increase the total power throughput, which means bigger cap size and higher break rate. With 100nF+ and say 240bps (assuming ballast suitably adjusted) you could push much more power through the primary. Having said that, you're going to want a bigger secondary system to deal with the increase level (else you'll have terrible flashover problems).
Hope that helps,
Colin.
-----Original Message-----
From: Tesla [mailto:tesla-bounces@xxxxxxxxxx] On Behalf Of David
Sent: 12 March 2015 03:10
To: Tesla Coil Mailing List
Subject: Re: [TCML] Looking for suggestions on tuning.
Caleb, actually with about 27 nFd of primary C, and a 4x18 secondary coil, 4 to 5 ft. sparks are actually pretty respectable. I would submit that you are basically trying power a go cart with an Indy race car engine. Let me explain. Your transformer is beastly enough for for charging a much larger primary C and a coil system many times physically larger than what you have. Certainly, your transformer, welder ballast and large variac combination power supply are deserving of a much larger coil, with around ~100 nFd primary C and a matching huge topload to drive. If you had a properly sized and designed coil system to match your beastly power supply, you should easily expect 12 to 15 foot arcs once properly tuned! Unfortunately, you won't be able to achieve performance any where near this with your present "emasculated" coil system. I would definitely hold on to that monster power supply for a future "man-sized" coil, though and consult javatc for future construction guidelines.
David
Sent from my iPhone
> On Mar 11, 2015, at 6:49 PM, Caleb Thompson <calebriant777@xxxxxxxxx> wrote:
>
> Tesla coil: http://youtu.be/R3cwkj1ms8c. This is a video, it's a 4"×18"
> secondary with 26 awg wire, primary has 12 turns 5/16" apart, 1800
> rpm synchronous spark gap , fires twice per revolution, mmc bank
> using 942C20P15K-F .15mfd 2000v DC caps, 11 in series, two sets in parallel.
> 14.4kv 15kva transformer, two bushing, using a 225 arc welder to
> limit current, a 60 amp variable transformer control. It makes 4.5'
> to 5' arcs at best, Any suggestions will be appreciated , thanks.
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