Is this good GDT ?

[LoOdaK]

Hi guys I finally got ferrite cores and it was my first time that I wound GDT.

Could you please take a look at it and point at some mistakes and things I could improve.
GDT is made with cat5 cable, primary should be around 8 turns and secondaries around 12 turns
My concern is that wires are not twisted enough but I would like to hear opinions from more experienced people

Picture:

[davekni]

My concern is that wires are not twisted enough but I would like to hear opinions from more experienced people

GDT ratios other than 1:1 are inherently difficult to make with low leakage inductance.  Yours is likely good enough.  I haven't personally used 2:3 ratio GDTs.  If you have a scope available, check resulting gate waveforms to make sure you have enough series resistance to damp excessive overshoot.

Since I've seen 2:3 ratio GDTs several times on this forum, decided to try to come up with a better winding technique (lower leakage inductance).  Came up with two options.  Both are tricky to construct, however.  Might eventually add one to my GDT tutorial thread if I can manage to make it reasonable.

Your lead wires are nicely twisted.  If you want to be a perfectionist and try to optimize the windings more:  What matters is pairing of primary and secondary wires.  Twisting of the two primary wires together within the winding is counter-productive.  As much as possible, pair primary wires with secondary wires.

Both of my thoughts for 2:3 designs use 3 paralleled primary wires instead of 2 or 1.  That way there is a primary turn for every secondary turn.  In your case, there would be a total of 24 primary wire turns (3 wires of 8 turns each).  That matches the 24 secondary wire turns (2 separate wires of 12 turns each).

My first thought is to wind the primary first.  (Wind all three primary wires together as a flat ribbon, not twisted for the part wrapping around the core, only lead sections twisted.  Then wind the two secondaries with each secondary turn between two primary turns.  I tried that with normal stranded cat5 wire.  Was difficult to hold primary in place while winding secondary.  May retry with solid wire.  That may be workable.

Other version is to pre-twist the three primary wires with two secondaries, then wind the twisted wires.  Hard to explain without pictures.  Also hard to keep track of which segment of twisted wire wraps which direction around the core.  I've messed that up twice already trying to document an example.

The key point is that your GDT is likely fine.  I'm just a perfectionist, so try to dream up more ideal options.

[Mads Barnkob]

Could you please try to upload the picture to the forum? It seems like your image host is blocking other countries?

All I am seeing is this:

[davekni]

Could you please try to upload the picture to the forum? It seems like your image host is blocking other countries?

All I am seeing is this:

Interesting.  The picture worked fine yesterday and earlier today.  Now it isn't showing up for me either.  Yes, I agree that it would be best to put the picture directly in the post.  I hadn't even noticed that it wasn't initially.  The image that showed up initially in the post was plenty large that I don't click on any link.

[LoOdaK]

Strange, I still see the photo 

Here is the link to the photo:
https://i.imgur.com/XyHqABx.jpg

EDIT: I also edited the image link in the post, it should show up now

[Mads Barnkob]

Your GDT winding is fine and will work just as good as a perfectly made one. There was once a website called the thedatastream that made GDT winding experiments. From very tight and perfect, to loosely coupled windings. There was a difference! But no difference that meant it would not work.

I think Dave tried to explain this winding method, where you parallel alle the "white" wires in the twisted pairs, for the primary and then use the color wire, one for each secondary. This way you have the primary twisted into the normal twisted pairs. Very tight coupling.



Picture from: https://kaizerpowerelectronics.dk/tesla-coils/kaizer-drsstc-i/

[LoOdaK]

Sorry for the late reply,

thank you guys for the explanations and example, I hope my GDT will perform well.
I will post here results of my project for sure