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I've seen a few transformers on here with four sets of 'big' cores arranged in an 'X' to lower the number of secondary turns. If mine doesn't work, I'll try that myself.
Thanks I will try to find the biggest core I could find , do you happen to have a link to those transformer, I'm trying to find it on the forum but they are so many post, Thanks for the graphics Tony, but as Steve said, I was expecting to see the frequency as part of the variable. But is a good chart I been looking for something like that. thanks,
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
Steve Conner wrote ...
A classic newbie mistake is to try and make a HF transformer of way too high voltage, instead of using a lower voltage transformer with a CW multiplier. (Or building a Tesla coil instead if you really need a HF AC output.)
Even if you got the insulation right to avoid corona, self-capacitance would probably bite you in the backside. You have to drive the transformer at or below its self-resonant frequency, so you have to get that as high as possible, because the drive frequency limits the volts per turn you can get from the core.
I think a practical maximum from a TV flyback-sized core is about 15kV.
Any idea what a 'practical maximum voltage' is for a core with 18cm^2 @~25kHz, Steve? I'm aiming for 20-30VPT & 2000turn secondary, and then feeding the output into a multiplier inside a vacuum chamber, using glass diodes and capacitor plates (aka 'vacuum capacitor'), in order to prevent outgassing.
Am I going the 'wrong way' by trying to keep the frequency down to 25kHz? I assumed the cores would get hotter with increased frequency.
I'm planning on using elliptical pancake secondaries with a circumferance in excess of 200mm.
I downloaded a transformer calculator some time ago, but didn't have sufficient information to input into it to get meaningful results. Maybe I should have another look at it now I have a better idea of the parameters I want.
EDIT:
Andre wrote ...
, do you happen to have a link to those transformer,
I think the last one I saw on here was around a year ago, but I can't be certain. I've seen two or three over the past 2 1/2 years or so, but at the time I didn't realise their significance.
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
Well, I'm not a transformer designer, you are. :p Before buying materials you should put together a spreadsheet that estimates the self-resonant frequency and so on.
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