Commercial vs Self-Made GDT Performance

[bockett]

Hello again! I've noticed that most people seem to be winding their own GDTs rather than buying commercially available ones. Is there a reason for avoiding commercial GDTs for use in tesla coils, or is it more about greater control or just wanting to build it themselves? I was planning on using a prebuilt GDT because I want to avoid making another potential point of failure for myself, but I also wanted to make sure I'm not overlooking any significant benefits of making my own.

If commercial GDTs are fine, then I would also appreciate any input on which one would be best. I have been looking mostly at the Vishay MGDT100125 and the Pulse P0584ANL. The Vishay one has lower leakage inductance and a 1:1.25:1.25 turn ratio, but it looks like an unconventional design and the Pulse one has better Et (Drive Excitation Max in the Vishay datasheet). I've tried looking into them myself but I don't have any reference points to help make sense of some of the numbers I've seen in their datasheets. If anyone would be able to provide good target values for things like leakage inductance and Et that would make a GDT suitable, that would also be really helpful.

Please let me know if I can explain any of my questions better, and thank you for your time!

[costas_p]

Personally, i am using 2x P0584NL for my TO247 full bridge drsstc running around 230kHz with no problems so far.

Calculating ET=(Vgate_drive * DutyOn) / Freq, then you can find that for 24V gate drive you can go as low as ~127kHz

[Manz]

I used a "self made" gdt because I was able to find plenty of cores at a really low price (just a couple of bucks per core) at my local electronics faire so I'm guessing price might be one of the reasons why GDTs are often DIY.
But Im a newbie so I might be wrong, lets wait for the experts

[Mads Barnkob]

I think prices on commercial GDTs was just something different 15 years ago and that is the main reason for homemade GDTs.

[Hydron]

You can also get leakage inductance lower if you DIY one (at the cost of higher inter-winding capacitance). Needs some care to do though - use the minimum number of turns and couple primary/secondary very well (I've used thin co-ax with shield for primary and core for secondary) and you can get <200nH leakage L. Not sure it's worth it though given the ease of using a COTS part that's not much worse!

Note that if you're using big long wires to or from your GDT then there is no reason to worry about the leakage L, as the wires will contribute a lot unless you're careful (the trick I use is to put the drive MOSFETs right next to the GDT, then connect to the IGBT gates via ribbon cable, with a number of alternating E/G lines in parallel giving low inductance, with the added bonus that ribbon cable is extremely easy to work with).

[bockett]

Thank you so much for the feedback everyone! I think I'm only going to go with a 12V gate drive for my first coil, so I'll probably end up using the Vishay because it has lower leakage inductance, but maybe I'll try winding my own in the future. Thank you again and have a nice day!

[Hydron]

That Vishay one is also pretty expensive, but seeing how it's built makes me thing that maybe it's a good chance to try some planar transformer design using JLCPCB's 6-layer promo (50*50mm for $2). Now I'm really annoyed that I sent off an order for work a week ago without whipping one up and adding it to it