High Voltage Forum

Tesla coils => Solid state Tesla coils => Topic started by: FilipŠebík on January 09, 2018, 03:47:39 PM

Title: Best core for GDT and FBT
Post by: FilipŠebík on January 09, 2018, 03:47:39 PM
Hey, today I took my SSTC driver to school and probed the GDT on oscilloscope. The things I saw... I can't even explain how horrible the waveform looked. I just though that the bad performance of my driver would be caused by my interrupter, which I probed too and its very good looking.

GDT: So to the core type. As far as I've searched, I found this https://www.tme.eu/gb/details/tx42_26-3e25/ring-ferrites/ferroxcube/tx422613-3e25/
Nothing more. I know its against the rules, but if someone wants to take their time, they can find a core on this page https://www.tme.eu/gb/katalog/ring-ferrites_113555/ Where I can buy stuff from and this would be useful for everyone that is looking for a good core.

FBT: I found this https://www.tme.eu/gb/details/ppas100/current-transformers/talema/as-100/ I don't know if 1:50 ratio is good for FBT, but as I've seen on many schematics that they use 1:50 ratio, I though that it should be good. If it would be better to wind my own FBT, then this one? https://www.tme.eu/gb/details/tx42_26-3e25/ring-ferrites/ferroxcube/tx422613-3e25/ :DDD I know I posted this one for the GDT, but I think that its ok too :D

Thanks for help
Title: Re: Best core for GDT and FBT
Post by: Laci on January 09, 2018, 04:26:07 PM
I am using the TX42/26/13-3E25 cores as GDT,OCD,FBT.As GDT it works very well(150kHz),as OCD and FBT I did not tested yet.It also depends on the driver and the load.Why would you like to use FBT with primary feedback(right?!)instead of antenna or secondary base feedback?I am just interested. :)
Title: Re: Best core for GDT and FBT
Post by: FilipŠebík on January 09, 2018, 04:35:02 PM
I say, that thing that sucks the most is the antenna, so I want to replace the secondary feedback antenna with a FBT

edit:
Too bad... The TX42/26/13-3E25 core is not on stock... So I tried to find another one and I found this https://www.tme.eu/gb/details/tn25_15-3e25/ring-ferrites/ferroxcube/tn251510-3e25/ and this one https://www.tme.eu/gb/details/tn29_19-3e25/ring-ferrites/ferroxcube/tn291975-3e25/ I don't know if any of those are good or bad. This is my last resort, or maybe my GDT is wound bad? Its a yellow core from PC power supply. I wound huge amount of turns of a cat6 cable around it. I can bring the core to my school and measure it at thursday, but not earlier. I would wind less turns on it and even test some other cores that I have. I even have some flyback cores that I will use to wind my own flyback (more on that later) and I can test those too :DDDD Also I think that using flyback core is stupid but who knows :D
Title: Re: Best core for GDT and FBT
Post by: Laci on January 09, 2018, 06:28:28 PM
The yellow core from the PC PSU is really bad for GDT,its made out of iron powder which is not good.I recommend you to check out my "SSTC (Not) Working Correctly" post.I had the same questions and got perfect answers to all of them.

https://highvoltageforum.net/index.php?topic=122.0
Title: Re: Best core for GDT and FBT
Post by: oneKone on January 10, 2018, 12:49:13 AM
I've been using n30 cores from rs components for my gdt , they seem to work well and are relatively cheap. The one I've been using is:
  https://au.rs-online.com/mobile/p/ferrite-rings/2120982/

Title: Re: Best core for GDT and FBT
Post by: FilipŠebík on January 10, 2018, 08:55:47 AM
So I ordered 7 cores to test, and if some of them fail, I can use them in something else. I will test them when they arrive and I will be in school. I will post the core at different frequencies with waveforms from oscilloscope.

These are the cores:
https://www.tme.eu/gb/details/tn25_15-3e25/ring-ferrites/ferroxcube/tn251510-3e25/
https://www.tme.eu/gb/details/tn29_19-3e25/ring-ferrites/ferroxcube/tn291975-3e25/
https://www.tme.eu/gb/details/tn32_19-3e25/ring-ferrites/ferroxcube/tn321913-3e25/
https://www.tme.eu/gb/details/tn20_10-3e25/ring-ferrites/ferroxcube/tn20107-3e25/
https://www.tme.eu/gb/details/tn14_9-3e25/ring-ferrites/ferroxcube/tn1495-3e25/
https://www.tme.eu/gb/details/tn10_6-3e25/ring-ferrites/ferroxcube/tn1064-3e25/
https://www.tme.eu/gb/details/tn13_7.5-3e25/ring-ferrites/ferroxcube/tn13755-3e25/
Title: Re: Best core for GDT and FBT
Post by: futurist on January 10, 2018, 03:13:30 PM
3E25 material will work fine. I use same ferroxcube cores from TME for both GDT and CTs
Title: Re: Best core for GDT and FBT
Post by: FilipŠebík on January 12, 2018, 07:31:19 PM
Nice, the cores arrived and just waiting till Tuesday, so I can test them on oscilloscope in school. Any ideas on how many windings I should use? I say about 12-15, so 13 is fine I guess. And I won't test the TN14, TN13 and TN10 because they are too small. And I will make a new thread with links for the cores, scope pictures, frequencies used as well as some other things too.
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Title: Re: Best core for GDT and FBT
Post by: Mads Barnkob on January 12, 2018, 09:02:04 PM
I flipped through my file archive and found a spreadsheet I made back in 2013 to calculate GDTs. Some day I will convert it to a online calculator, but for now you can try it out here.

It is in openoffice format, I don't know if excel can open it?
Title: Re: Best core for GDT and FBT
Post by: FilipŠebík on January 13, 2018, 06:57:34 AM
Thanks for the calculator, I calculated "Something" and came up with 13 turns on the primary. Duh what a coincidence that I predicted that :D
Title: Re: Best core for GDT and FBT
Post by: Hydron on February 02, 2018, 10:48:39 AM
This is what I used:
http://uk.farnell.com/epcos/b64290l0674x830/ferrite-core-toroid-n30/dp/1190604?st=n30%20toroid

I could only fit 5-6 turns on in my case, so I had to find something with higher Al (this has 5.75uH).