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Modern AC Flyback Transformers

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Fiddy

Mon Sept 01 2014, 11:32AM

Registered Member #8817 Joined: Mon Dec 17 2012, 05:16AM
Location: Australia
Posts: 110

G'day,

So i have an abundance of DC flybacks but no AC flybacks!

Anyway i have been talking to transformer manufactures and i have got them to wind a sample one on the biggest flyback core they could.

It features:

No diodes for true ac output.

No primary coils at all.

Insulating bobbin on-core for your own primary

Large gap between secondary and primary for your own primary winding.

3000 turns of 28AWG secondary

Potted and insulated secondary

Would anyone be interested in modern day AC flyback transformers?

Flyback1

Note this production sample has a really short HV output lead, this will be a lot longer if i get a batch made.
Flyback2

Its a bit bigger than your average DC flyback :)
Flyback3

If you are interested reply and state how many you where thinking about owning.

Interested List:

First Run COMPLETED

Fiddy:2
Sigurthr: 1
Alex1M: 1
...: 2
Dago: 5
Rod-on: 2
loneoceans: 1
mbd: 4
hen918:2
Ash Small: 1
jpsmith123: 1
Polonium210: 2
Artlav: 1

Total:25

------------------------------------- -------

Second Run

Fiddy x1
woodchuck x2
Kizmo x2
TwirlyWhirly555 x1
GrantX x2
Avi x1
Thomas W x2
StevenRS x4
Adam x4
LouiseHV x4
Green Hornet x2

Confirmed:21
Unconfirmed:4

Total: 25

Thanks for looking!

Fiddy.

Dr. Slack

Mon Sept 01 2014, 11:57AM

Registered Member #72 Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659

Sounds a really neat bulk-buy component.

What's the rating for the AC output insulation, peak voltage?

Fiddy

Mon Sept 01 2014, 12:12PM

Registered Member #8817 Joined: Mon Dec 17 2012, 05:16AM
Location: Australia
Posts: 110

Sure is, with a induction heater style ZVS ive put more than ~20A at 24VDC into this flyback and its handled it.

With a 10 turn primary, 22VDC loaded @ 17A it was putting out 13.2kVAC RMS @ 28mA and has capacity for more!

Erlend^SE

Mon Sept 01 2014, 02:29PM

Registered Member #1565 Joined: Wed Jun 25 2008, 09:08PM
Location: Norway
Posts: 159

Very nice.

I have some negative output flybacks.

Who did you order the transformer from?

Patrick

Mon Sept 01 2014, 06:07PM

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

Fiddy wrote ...

Sure is, with a induction heater style ZVS ive put more than ~20A at 24VDC into this flyback and its handled it.

With a 10 turn primary, 22VDC loaded @ 17A it was putting out 13.2kVAC RMS @ 28mA and has capacity for more!

I like AC flybacs too, as theres no guessing the ratings on diodes, diodes to fail, or bizarre resistors and pots hanging off the sides. But, how do you know it's 13.2kVAC and 0.028A ? This would equate to 370 watts.

If so, 13,200 v / 3,000T = 4.4 V per turn.
And 22 V / 10T = 2.2 V per Turn.

so your gaining twice as much output voltage as the turns would allow in a conventional topology. Generally i like Flybacks, as we gain winding advantage, but lose on power transfer. Though in a ZVS mode maybe there's not so much power lost.

With 3000 turns with a 1 inch diameter means Pi x D = C and 3.14 x 1 = 3.14 in x 3,000T = 9,420 in of 28 awg.
28 awg = .213 ohms per meter,
9,420 in to meters = 239 meters.
239m x 0.213 ohm = 51 ohms.

so, if .028A x 51ohms = 1.4 real volts dropped by current (non reactive) 1.4 VAC x 0.028A = 0.04 watts heating in that secondary, so thats good.

have you run it long enough to judge ferrite heat accumulation?

Sigurthr

Mon Sept 01 2014, 11:04PM

Registered Member #4463 Joined: Wed Apr 18 2012, 08:08AM
Location: MI's Upper Peninsula
Posts: 597

The circuit he's using uses bipolar ZVS drive iirc so it would be +- 22V seen by the primary. Oh and he said he's inputting 374W. 40mW waste in the secondary sounds really good. As it's ZVS the primary would see only resistive losses too.

I'm definitely interested in at least one.

Patrick

Mon Sept 01 2014, 11:25PM

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

So how much? Does it come with a datasheet?

Alex M

Tue Sept 02 2014, 02:11AM

Registered Member #3943 Joined: Sun Jun 12 2011, 05:24PM
Location: The Shire, UK
Posts: 552

Hi Fiddy, I would be interested in these.

What sort of costs are we looking at?

Fiddy

Tue Sept 02 2014, 02:14AM

Registered Member #8817 Joined: Mon Dec 17 2012, 05:16AM
Location: Australia
Posts: 110

I have run it for a while and it doesnt ge very hot at all

I do not have a datasheet for the sample but have requested one.

Not too sure on price as of yet, it maybe around $40USD it all depends on the bulk factor.

Ash Small

Tue Sept 02 2014, 12:37PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

Fiddy wrote ...

Not too sure on price as of yet, it maybe around $40USD it all depends on the bulk factor.

Then there is postage from Australia.

ZVS runs in push-pull mode, not flyback mode. You don't usually need an air gap for push-pull mode.

Patrick wrote ...

so your gaining twice as much output voltage as the turns would allow in a conventional topology.

If run in flyback mode output voltage should be higher. Flyback mode doesn't depend on turns ratio. The only factor that depends on turns ratio in flyback mode is the reflected voltage seen by the primary (and the switch).

The energy stored in the airgap pushes the voltage up to whatever the load (and current) dictates. The higher the impedance of the load, the higher the voltage. A flyback (in flyback mode) is a coupled inductor, not a transformer.

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