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About making flybacks as Uzzors2k(Eirik), Steve Ward et al. describe.

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Patrick

Tue Mar 16 2010, 06:36AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

approx 100- maybe..200khz. ferrox cube 3c94 if im not to drunk to remember.

Steve Conner

Tue Mar 16 2010, 11:19AM

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

Hey, this is a serious forum, try not to post when you're hosed! :P

McCluskyCustom: Thanks for that useful post.

Oil has about 6 times the dielectric strength of air, so you can have E-fields 6 times higher. You still need to be careful about winding design, just 6 times less careful. You also need to be careful at places where high voltage conductors pass through the surface of the oil, this is a natural point of high stress because of the different dielectric constants of oil and air.

A rotary vane pump of the kind used for servicing AC systems is fine. Tesla used to just boil his transformers in their oil tanks to drive the air out, he didn't pull a vacuum on them at all, but vacuum is better. If you suck all the air out of the container, I don't see how veggie oil could go rancid.

Dr. Dark Current

Tue Mar 16 2010, 01:22PM

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

100kV at 200kHz AC?

If you really achieved this, I think you'd get a huge air discharge on the output, like you'd expect from a Tesla coil running at CW.

Steve Conner

Tue Mar 16 2010, 01:38PM

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

Yes, and what's more, a solid-state Tesla coil would probably be the best kind of generator to make it with.

GeordieBoy

Tue Mar 16 2010, 01:46PM

Registered Member #1232 Joined: Wed Jan 16 2008, 10:53PM
Location: Doon tha Toon!
Posts: 881

>> i will begin making a 100Kv, 1KVA flyback this week.

> Yes, and what's more, a solid-state Tesla coil would probably be the best kind of generator to make it with.

Agreed, a flyback converter sure wouldn't be my method of choice!

-Richie,

jpsmith123

Tue Mar 16 2010, 04:18PM

Registered Member #1321 Joined: Sat Feb 16 2008, 03:22AM
Location:
Posts: 843

I thought you were going to say 20 to 30 kHz or so.

It seems to me that your requirements would be impractical if not impossible to meet with a ferrite core type transformer. You're definately in the realm of a tesla coil, IMO.

Patrick

Tue Mar 16 2010, 05:19PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

shit, im sober now.

[geeordie boy] yes a flyback trfmr would not use the core effectivly, i am merely examining others construction techniques, my trfmr will be ferrite with a normal turns ratio and no air gap for the core. as you said flyback topology is too undesirable for high power. and i will use both a Bflux+ swing and a Bflux- swing hence the AC output. EC snelling's book soft ferrites is of great help.

[steveMconnor] are you suggesting i use a TC or that others could use such a device for a STTC?and yes about the 6x field intensity explanation is well taken, will remeber.

[jpsmith123]i will start at 100khz fair-rite type 77 u cores, then increase or decrease freq from there. eventually i will switch to ferrox cube material 3c94.

i need the high freq to keep the volt/turns high , if i can get this to work i will post it in the projects forum with detailed explanations of how i aqttemted this and lessons learned.

also its for a Deseversky ionocraft, so a TC type wave form wont work, the trasnsformer will see 100khz but the squarewave AC will be like 6khz (167uS) +kv then (167uS) -kv while the 100khz (5+5uS) pulse train inside the those (167uS) pulse trains. its all very convuluded ill admit that , and it might notbe possible and maybe the ionocraft idea is not practicall for real aircraft/spacecraft. but for my Phd, EE i will attempt this.

but this thread was meant to explore vacuum conditions related to insulation cronstruction...plz return to that topic. and lets continue ,this thread especially arcstarter and mcclusky's comments have been useful.

-Patrick

Steve Ward

Wed Mar 17 2010, 07:00PM

Registered Member #146 Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055

Id be willing to bet some money that you cannot construct a ferrite-cored transformer to run 100+ KHZ at 100kVpk. Your stray inductance and self-capacitance of the winding will keep the resonant frequency well below 100khz, probably a few khz really. And, in case you didnt know, driving a transformer *above* its resonant frequency is just an exercise in futility, its got too much impedance to get much use out of it.

Patrick

Fri Mar 19 2010, 11:59PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

I was afraid of those stray factors, L and C making this frequency a problem. i chose this 100khz frequency for the high volt per turn, which i need. i need to ask you (Steve ward)about two things.

first, about your method of vacuum potting, how is it you do it? i need advice !

second, i need tosend you a DXF file and text doc. that show you my idea for a "Modified Cross-section Transformer" (MCT) which may allow very few secondary turns and ultra high power density, at VERY high Voltage.

Can i send you steve a PM? or what?

also, your site is particullary useful to many of us.

-Patrick

Patrick

Tue Mar 23 2010, 11:34PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

i hope this doesnt count as a double post as i have new info.

many of you have advised me to forget the ferrite and just build a tesla coil, is it possible to get high (10Kw per Kg) power density from a TC? i need 100kv or so at kilowatt levels for my ionocraft PhD thesis.

also, since the TC would be part of a complete power supply system, is it possible to shield and enclose the coil, (E fields and M fields) and shield other logic stuff from radiating fields? (without a single turn short appearing)since an aircore doesnt act to confine the magnitism in the way ferrite would.

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