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SSTC: base feed transformer

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Marko

Wed Dec 05 2007, 07:17PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

Hm... I haven't got any theoretical predictions yet!

- I assume I would gain a lot of efficiency by minimizing the magnetizing current and having high primary cos fi;;

- would I actually be able to hard switch without spoiling the cos fi significantly, like for audio modulation...
So, how would frequency shift or duty cycle modulation affect things? assuming I have good diodes.

I'l try to make some work once I get out of school trouble.

BTW, arcs on the hacked gadgets coil look like my DRSSTC running at 30V in... I hope we can do better than that? And in CW surely.

Marko

Dr. Dark Current

Wed Dec 05 2007, 08:02PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

I think I will try it sometime soon..
So you think a 1:10 xformer is OK, e.g. 15:150 on a flyback core? Or can I use even less turns at this frequency?

My original idea was to make a sstc design more reliable, with disadvantage of added complexity. But I believe it should save quite some FET deaths if it works well and maybe even increase possible maximum streamer length (no pri-sec flashovers)

Mates

Wed Dec 05 2007, 11:37PM

Registered Member #1025 Joined: Sun Sept 23 2007, 07:53PM
Location: Czech Rep.
Posts: 566

I've always thought that ferrite used for fly-back cores can not handle frequencies much over 30 KHz. That would mean pretty large coil. So how is it?

Steve Conner

Thu Dec 06 2007, 09:38AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Well, there are lots of different grades of ferrite, and some are good up to hundreds of kilohertz, or indeed even hundreds of MHz.

Tom540

Thu Dec 06 2007, 04:14PM

Banned on 3/17/2009.
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Mates wrote ...

I've always thought that ferrite used for fly-back cores can not handle frequencies much over 30 KHz. That would mean pretty large coil. So how is it?

We have ferrite cores at work that are driven at 100KHz.

Now with this magnifier config would you tune the primary on the flyback or no?

Dr. Dark Current

Thu Dec 06 2007, 04:17PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

Tom540 wrote ...

Mates wrote ...

I've always thought that ferrite used for fly-back cores can not handle frequencies much over 30 KHz. That would mean pretty large coil. So how is it?

We have ferrite cores at work that are driven at 100KHz.

Now with this magnifier config would you tune the primary on the flyback or no?

Of yourse not, you tune the resonator

Marko

Sun Dec 09 2007, 02:38PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

Hi all

I succeeded making a sparking coil with transformer base feed.

Unfortunately due to hasty ghetto construction I Wrecked the transformer after few seconds of full power run and fun was over.

Due to system being coupled to ground it tended to arc to core and primary (which it normally wouldn't do) and it burst into a fireball.

I was using something like 1:6 winding ratio on the transformer - something between 1:10 and 1:20 would have probably been better. Considering the frequency i was running I could have used much less primary turns than 18.

Enough work for today,

Marko

Dr. Dark Current

Sun Dec 09 2007, 04:30PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

Do you think this design will work with the "mini SSTC" driver (antenna feedback)? If so I have all parts on hand.

Marko

Sun Dec 09 2007, 06:30PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

I don't see why wouldn't it work with any driver scheme which worked with air cored transformer.

Things like flyback transformers have too high ratio, so you need to wind your own winding.

Dr. Dark Current

Sun Dec 09 2007, 06:46PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

I just tried with 30(?):300 transformer on a flyback core. At very low powers it kinda worked, the antenna was getting some feedback. As I upped the power, my impedance matching transformer started sparking over. Hmm, there had to be several kV on its output while the tesla secondary was hardly making any spark.

What I think did happen is that the circuit tuned to the resonant frequency of the matching transformer's secondary winding, this also explains the relatively very high voltage on its output
.
I need to find a way to make the circuit tune to the resonant frequency of the TC secondary, but I really have no idea how to do this...

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