My SGTC is underperforming

[MarcusFunt]

My "old style" Spark gap tesla coil is not performing as well as i had hoped.

I'm using 10 942C20P15K-F capacitors in series to give me 20kv (I'm using them at max 7kv) at 15nf.
I have an 8 turn primary with 1mm copper wire (I know its really thin. I have 2.5mm wire on it's way from Amazon)
I have a zvs driver as my power source (I would have used a nst, but i haven't found any i could get my hands on).
I use two, 10cm long 1cm diameter pipes with fan as spark gap.

On the secondary side I'm using a 75mm Ø white pvc pipe with 28Gauge wire around it, about 900 turns.
And a top load made with 110mm aluminum drier duct.

I'm thinking that my psu and primary are the bottleneck. I could be wrong tho?.

[klugesmith]

Welcome to the forum, Marcus. I have no personal TC experience, but you have my sympathy for your disappointing TC project.  Is that what you came for?  The original post contains no question, and no request for advice.  Nor is one implicit, at least to this reader.

We have to guess what you mean by "underperforming".  Are sparks or arcs nonexistent, or smaller than you had hoped?  Numbers, please.

[304er]

Hi,

Yes, some more details needed here.

What are you getting for spark output? Did you design this with paper and pencil? Or did you use some computer program? Even still...if design work was calculated some way, my experience is that old school tuning is still required for best performance. There are in my opinion aways real world variables out of our control when you actually build a Tesla coil, unless if you possibly control everything to be perfect, again hard to do , especially if one is "budget building" a coil. (Well...you did spend on the good caps, unless you got lucky on good prices for these somewhere. We discussed this recently of good possible prices somewhere in a different thread here.) Test equipment measurements are required along the way to verify if it is within what was designed to begin with, and this requires a lot of time and work. If none of this was done, then most likely quite out of tune. Even if you follow something with the extra work I said, tuning is usually still required, but you are much closer to optimum tuning. Reducing losses in parts of the whole circuit helps some too.

Also I am going to assume your ZVS does not have a whole lot of power output possibly. You did not say what it is. A coil's input power is directly related to minimum power out (spark length) expected.
So it is possible you are getting what is expected for your power in.

Just some rambling thoughts here for not having many details.

Chris

[MarcusFunt]

Hi,

Yes, some more details needed here.

What are you getting for spark output? Did you design this with paper and pencil? Or did you use some computer program? Even still...if design work was calculated some way, my experience is that old school tuning is still required for best performance. There are in my opinion aways real world variables out of our control when you actually build a Tesla coil, unless if you possibly control everything to be perfect, again hard to do , especially if one is "budget building" a coil. (Well...you did spend on the good caps, unless you got lucky on good prices for these somewhere. We discussed this recently of good possible prices somewhere in a different thread here.) Test equipment measurements are required along the way to verify if it is within what was designed to begin with, and this requires a lot of time and work. If none of this was done, then most likely quite out of tune. Even if you follow something with the extra work I said, tuning is usually still required, but you are much closer to optimum tuning. Reducing losses in parts of the whole circuit helps some too.

Also I am going to assume your ZVS does not have a whole lot of power output possibly. You did not say what it is. A coil's input power is directly related to minimum power out (spark length) expected.
So it is possible you are getting what is expected for your power in.

Just some rambling thoughts here for not having many details.

Chris

I am using a zvs driver at around 150 watt output and getting 8cm(bit over 3 inches) out of the coil in open air(18cm (7 inches) to ground). I designed it in javatc and have a flat primary coil tapped at 7.8 turns (calculated 8 in javatc). Others have made coils with similar specifications that gave up to 30cm arcs.
What do you think is the bottleneck?

Marcus

[304er]

Hi Marcus,

What does javatc predict for your coil parameters for output spark?
I will admit I am old school, I do not use a program like this at all.

I will admit I have never used a ZVS on a spark gap coil. So yours is a hybrid.
150 watts does not seem like much power to me.
Need some others to chime in here on this ZVS.

Also is your spec of toroid of 110mm correct of ducting diameter? This minor diameter would result in a quite large toroid for a coil this size with the power input you have also if I am understanding this correctly.

Chris

[MarcusFunt]

Hi Marcus,

What does javatc predict for your coil parameters for output spark?
I will admit I am old school, I do not use a program like this at all.

I will admit I have never used a ZVS on a spark gap coil. So yours is a hybrid.
150 watts does not seem like much power to me.
Need some others to chime in here on this ZVS.

Also is your spec of toroid of 110mm correct of ducting diameter? This minor diameter would result in a quite large toroid for a coil this size with the power input you have also if I am understanding this correctly.

Chris

Javatc predicted a 50cm spark, although i would never trust it. I know my psu is not very powerfull, i may be able to buy a 0.5kw nst from Mads barnkob.
My toroid is quite big but i couldnt find smaller duct in my local hardware store.

Marcus

[304er]

Hi Marcus,

I will admit that I was expecting a somewhat high number for output from javatc. Seems to be a common thing that I have noticed sometimes by others too, even though I have never used this program, I suppose this is caused by some missing or incorrect inputs somewhere.

Yes, my opinion is not enough power in, especially to charge up a 15nf tank capacitor.
The tank capacitor is usually matched in a certain range for power input.

And okay on verification on toroid size, yes quite big for your current power input.

Okay on the lead for more power... :^)

Got to "run" here... going to be spark gap coiling in my basement myself experimenting this afternoon for me here in my time zone.

Chris

[MarcusFunt]

Hi Marcus,

I will admit that I was expecting a somewhat high number for output from javatc. Seems to be a common thing that I have noticed sometimes by others too, even though I have never used this program, I suppose this is caused by some missing or incorrect inputs somewhere.

Yes, my opinion is not enough power in, especially to charge up a 15nf tank capacitor.

And okay on verification on toroid size, yes quite big for your current power input.

Okay on the lead for more power... :^)


Got to "run" here... going to  spark gap coil in my basement myself experimenting this afternoon for me here in my time zone.

Chris


Chris

Thank you very much for your answers. i made a video if you get time to check it out

[paulj]

Hi
It's not surprising that you have poor performance, The SGTC flyback rarely gives good results except on tiny models.
With your design, your flyback is not able to supply enough power to power your circuit, maybe it is supplying enough VOLTAGE, but not enough CURRENT.

 You need a new transformer. Use an NST, or if you don't have money, pass on a MOT.
(be careful these transformers are very dangerous to use be careful)

it may also be necessary to review the design of the capacitor so as not to burn it out.

Regards.