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Do tesla coils have phasing?

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lokeycmos

Mon Jul 09 2012, 02:48PM

Registered Member #2553 Joined: Fri Dec 18 2009, 01:36PM
Location: St Cloud Minnesota
Posts: 97

i have my tesla coil all put together, but i just cant get any output from it. ive tried many different things. one of my viewers on youtube mentioned that the primary may be out of phase with the secondary. is this a possibility? i thought that it is AC so it shouldnt matter. please educate me. ty

Dr. Dark Current

Mon Jul 09 2012, 03:24PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

Hi,
it doesn't matter. I ran VTTCs with the secondaries wound in the same direction but also opposite direction than the primary, both worked well.

E.TexasTesla

Mon Jul 09 2012, 09:58PM

Registered Member #4362 Joined: Sat Jan 21 2012, 03:44AM
Location: Texas
Posts: 98

What type of tesla?
If it uses some type of feedback signal it could be out of phase.

More info would help us help you.
edit: sorry, if its the one in you video link, it shouldnt matter. SGTC

Harry

Mon Jul 09 2012, 10:50PM

Registered Member #4081 Joined: Wed Aug 31 2011, 06:40PM
Location: UK
Posts: 139

Try adding more capacitance.
A tighter coupling could also improve results.
EDIT: I now see that you are quenching the spark gap.

PhilGood

Tue Jul 10 2012, 02:34AM

Registered Member #3806 Joined: Sat Apr 02 2011, 09:20PM
Location: France
Posts: 259

Hi,
I noticed in your video you are using steel plates and bolts for your tank capacitor and spark gap, and worse thing, they are screwed directly onto wood.

At the voltages and frequencies we are working with, wood is not an insulator and steel is a poor conductor.

You should use copper and brass for all your wirings.

Your tank caps and spark gap must be insulated with plastic or ceramic.

Dr. Brownout

Tue Jul 10 2012, 02:38AM

Registered Member #2405 Joined: Fri Oct 02 2009, 12:59AM
Location: Wisconsin
Posts: 140

Harry wrote ...

Try adding more capacitance.
A tighter coupling could also improve results.
EDIT: I now see that you are quenching the spark gap.

I agree that coupling looks pretty loose, I would tighten that up first then see if you get any spark. If not then play around with the tuning and see what happens. If you tune it on half power then you can kind of get good idea if your getting close or not. Just use the same voltage input each time after you move the tap position so you are comparing apples to apples.

Daniel Kramnik

Tue Jul 10 2012, 07:09AM

Registered Member #3885 Joined: Sun May 15 2011, 12:47AM
Location: Newton, Massachusetts, United States
Posts: 94

Try finding the actual resonant frequency of the secondary using a function generator and an oscilloscope, and then you'll know if you're even tuning in the right range.

My guess would be that your biggest problem is those ceramic primary caps you're using. I'd go with a string of CDEs instead. I also suspect that part of the problem is that you're driving a large coil with a relatively weak source of power. In my experience, 1.7*rt(Power) is a huge over-estimator of spark performance - try winding a smaller secondary with thinner wire. 28 - 30 gauge is about right if you don't have access to a lathe, which would enable you wind secondary with even thinner wire.

lokeycmos

Tue Jul 10 2012, 02:49PM

Registered Member #2553 Joined: Fri Dec 18 2009, 01:36PM
Location: St Cloud Minnesota
Posts: 97

Daniel Kramnik wrote ...

Try finding the actual resonant frequency of the secondary using a function generator and an oscilloscope, and then you'll know if you're even tuning in the right range.

yes i did do that. the resonant frequency is 325khz

Daniel Kramnik

Tue Jul 10 2012, 05:45PM

Registered Member #3885 Joined: Sun May 15 2011, 12:47AM
Location: Newton, Massachusetts, United States
Posts: 94

Have you also tried scoping the primary to find its resonant frequency at the point where you're tapped?

What procedure did you use to find the secondary resonant frequency?

I'd seriously consider making a new secondary - my 36 gauge 2.5" x 9" secondary with 8" x 2" top load resonates around 220kHz! You definitely want more tank capacitance too. In general, I've noticed that with the frequency kept the same, SGTCs perform significantly better (compared to secondary length) with smaller secondaries wound with thinner wire. Of course, this makes sense because you're pumping the same amount of power into a physically smaller system!

This doesn't explain the total absence of sparks though - what happens when you try removing your Terry filter altogether and closing the spark gap so that it fires more regularly? I've never used one of those filters in any of my spark gap coils, so I doubt you'll cause any damage to your transformer if you tried it just a couple times. Seems like the best thing to do at this point is to strip down the system as much as possible and just get it working in that state before you start worrying about keeping your HV transformer safe in the long-run.

brandon3055

Tue Jul 10 2012, 10:38PM

Registered Member #4548 Joined: Mon Apr 23 2012, 03:52AM
Location: tasmania
Posts: 271

It's possible the primary is resonating at a much higher frequency then the secondary (someone else might have said that) try removing the topload to increas the secondary frequency that might give some resolts also what is the tank capacitance it should probably be around 20nf and when you get it working you will need a better spark gap ether a multi segment or a rotary

BTW my new coil is built on wood and I haven't had any problems but it is powerd by 4 MOT's with that much power dose it matter?

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