I started making a drsstc

[Miki_407]

Long time no update I have done some tests and this is a photo of a breakout on 120vdc. It is 10-15cm long. It works on 120w and everything is cold to the touch(except primary that gets a little warm)

[davekni]

Nice picture!  And congratulations on your progress.

[Miki_407]

I tested it on 300 vdc and my not really good secondary design finally met it's limits

But not all is lost. I got a topload higher and it is pretty badly done but now. Have no flashovers.

And then I asked what song to play on it and I now needed to test it on higher notes.

Sorry for grammar and misspelled words I am in a hurry
Edit: Links are fixed now

[Mads Barnkob]

Great results There is however no sound on your first two videos?

The problems with flash-over in the first video is "racing sparks" due to too high coupling between primary and secondary coil.

It is interesting that it did help to raise the topload, the field lines from the topload could be too close and fight the voltage distribution on the secondary coil? DaveKni? Uspring?

[davekni]

I can only speculate on details.  Here are my thoughts:

Noticed that both racing sparks occurred just after a ground arc rose and stretched enough to break.  Perhaps that breaking-arc situation is causing momentarily-higher primary current or less-even electric field distribution up the secondary.

Two possibilities to why raising top-load helped:  First, the initial top-load position is roughly at the top of the secondary, making a shorted turn.  Raising the top-load will increase secondary inductance and lower coupling a bit.  Second, it may be a bit out-of-tune after the change.  Seems like performance was reduced a bit with the raised top-load.

[Miki_407]

There is however no sound on your first two videos?

Video was taken using a "slow motion" mode on my phone( only 4x slower) so there is no audio.
To me it seems to start from the topload as is seen from another angle.

I can say that performance was reduced a little after raising the topload.
Should I wind a new secondary taller then this one but with ticker wire to try to keep resonant frequency the same.

[davekni]

Thank you for the new viewing angle!  That looks more like an issue with top-load smoothness rather than "racing sparks".  Raising the top load will help with that.  Or, you could keep the top-load at its lower position and make it smoother.  Add another ring or two to improve the toroid approximation (more closely-spaced rings).  Make sure all ring mounting is all internal with no protrusions, at least no protrusions on the bottom side.

Also, a second grounded strike ring at the bottom, larger diameter at the same height, will reduce peak field, reducing the chance of an arc starting at the ground strike rings.

I expect secondary frequency is slightly lower with the raised top-load.  At its higher position it blocks less magnetic field from the secondary.  No need to rewind the secondary.  Instead lower primary frequency a bit to match.  Add another turn (or fraction of a turn) to the primary winding or increase MMC capacitance a little.

[Miki_407]

So after some testing I noticed that it was sparking inside a tube I used to get topload higher. After replacing tube with another cylinder it was sparking from end of the secondary to the ground around primary. To me it was odd that placing a single turn of electrical tape stopped sparking. Performance has improved. I don't have a video to show. I will order some wire for a new secondary as this one has one place I needed to solder after a accidental drop. I will make it taller and try keep resonant frequency the same according to javatc. Wire should arrive by mid April in worst case.

[davekni]

Electrical tape cannot block the entire Tesla coil field, but it can redistribute local fields enough to prevent arc initiation there.  Corona at the high-field point under the tape is likely to eventually degrade tape, with arcs eventually forming there again.

[Miki_407]

Wire came from UK and i made a new secundary. Now topload looks too small. But no more flash overs and with new primary it has a lot better arcs. This is me next to it. And i will add a video after i record it.

[futurist]

Good job! I can't believe you did this all by yourself 

Svaka čast da si sa 14 godina uspio dovršiti tako kompliciran projekt, za bilokakvu pomoć stojimo na raspolaganju 

[Miki_407]

Well i made it with my twin brother and it is 15 years old (my birthday was 15th april).
Not a valid youtube URL
Youtube shorts dont seem to work with this so here is a link directly:
https://youtube.com/shorts/iLdY4g5vxb4?feature=share

It isnt the best but i am happy with it. This is a half way in between C3 and C4 note in midi editor.

[Miki_407]

Update time!

I have to make a new topload. When a arc hits ground i placed there my usb to midi converter crashes and stops giving new notes. A better video will be uploaded tomarrow.

[Miki_407]

So i come with a problem. After a flashover to primary performance is bad. Current stops rising as it can be seen:


I don't know what is happening so I am asking for help from people more experienced than me.

[davekni]

It would be much easier to answer with information.  Scope traces have no vertical scale listed, nor which signals are being probed.  (I'm going to guess that the cyan trace is one H-Bridge output and yellow is primary current.  No idea on scaling.)  Also, no info on setup.  Bridge supply voltage?  Secondary in place or not?  Other load instead of secondary?

Guessing on everything, my thought would be a shorted turn on the secondary where the strike hit.

[Miki_407]

I am sorry for not providing information and also for asking this question before trying to replace igbts. I only ever got igbts to fail by short circuiting so i thought they were still alive. Now it works.
 Thanks for your time. Next time i will prepare the question better and i will provide all the information.

[davekni]

Don't worry.  You are learning a lesson that will help with college (and even hi-school) science classes.  Students frequently give answers without units, and that reduces grades.  You have a head-start on your future science and engineering studies:  Include units with measurements and calculated values.  And, lab reports should include a description of the experimental conditions, such as the grams of reactants used in a chemistry experiment.