Kapanadze Cousin - DALLY FREE ENERGY

[itsu]

Nick,

i have setup a similar circuit as you have, here on my bench (your TL494, push-pull MOSFETs, yoke, inductor and grenade with a 40W/220V load bulb
I have used the mentioned procedure to calculate an RC snubber and installed it on my MOSFETs.

My RC snubber calculated to be a 176 Ohm resistor in series with a 10nF capacitor to minimize the 820Khz ringing i had.

I am left with a spike on MOSFET turnoff time, but these spikes (268 and 232Vpp) are within the used MOSFETs specs (500V / 132A).
In your case (IRFP260 = 200V) you should need some extra protection via a varistor or TVS diode across the drain / sources if your spikes are similar.

I was running the wima cap / inductor in resonance pulling 24V @ 5A from the batteries.
No heatsinks are used on the MOSFETs as they don't run hot.

The screenshot shows the both MOSFETs drain / gate signals and the spikes at turnoff time.
Yellow / purple are drain/gate signals MOSFET 1
Blue / green    are drain/gate signals MOSFET 2

Video here:  https://www.youtube.com/watch?v=uBCAmXzmgkg

After a W10 upgrade to its latest level the youtube videos are crap in IE, so i use Chrome to play HD video's!!


Hope this shows that it is possible to run your setup for where you want to use it for.
Off course there are other options like mentioned here in the thread.

Itsu

[AlienGrey]

Nick,

Video here:  https://www.youtube.com/watch?v=uBCAmXzmgkg

After a W10 upgrade to its latest level the youtube videos are crap in IE, so i use Chrome to play HD video's!!


Hope this shows that it is possible to run your setup for where you want to use it for.
Off course there are other options like mentioned here in the thread.

Itsu

Have you tried adding some c across where the drains connect on the toroid 10 to 50 pf and watching on the scope? mine are irf150m i don't get all that over heating or frying to night probs of huge amp draw.
Allen

[NickZ]

  OK, thanks again.
  I'll watch your video now as I've been busy at work.
   I've got some caps to try out for the snubber, and I'll try them out later tonight.
I'm trying out the 103, 222, 472M, and others, I'll show some scope shots soon.
I don't have a 1.5ns, the 222 is the closest one to it. But the 103's are 2000v.

[T-1000]

Yes, i experimented with this it was brilliant and also produced other duplication of frequency harmonics easily, however, I don't understand why you are using so many turns and so high a voltage I had excellent results using a good quality toroid and 8+8 t and only 12v. did you have to double the 4 turn wind to 8 turns and the 28t to 58 turns to get any thing to work as i suspect it would cause a huge damping down and suppress any self-resonance oscillations  ?

WIth 24V setup instead of 12V the amp draw is less in expense of higher voltage so there is also less heating on push-pull MOSFETs. Also I am using PWM so the duty cycle for tuning is between 8-35%
And the main trick wih bifilar winding having center tap is, the BEMF is always positive which is exactly what transistors can handle without power losses.

Cheers!

[itsu]

OK, thanks again.
  I'll watch your video now as I've been busy at work.
   I've got some caps to try out for the snubber, and I'll try them out later tonight.
I'm trying out the 103, 222, 472M, and others, I'll show some scope shots soon.
I don't have a 1.5ns, the 222 is the closest one to it. But the 103's are 2000v.

Nick,

ok, try the 222 (2.2nF) it could work, but as can be seen in the linked procedure, lateron you need a cap between 4 to 10 times of 1/3th of that 2.2nF cap. (if that really halfs the ringing)
1/3th of 2.2nF = 733pF          4x 733 = 2.9nF      10x 733 = 7.3nF,  so a C between 2.9 and 7.3nF

https://www.maximintegrated.com/en/app-notes/index.mvp/id/3835


Anyway, will work that out when you are ready.

Itsu