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Winding your own ferrite transformer

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Thomas W

Fri Aug 05 2011, 04:50PM

Registered Member #3324 Joined: Sun Oct 17 2010, 06:57PM
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Posts: 1276

EDIT:

ok ive found myself on this page:

ive been looking at 50ALL 102-57-25-0000

but is this a good option?
or have i choosen the worst core out of the page?

thanks,
Tom

Patrick

Sat Aug 06 2011, 04:00PM

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

Tom Williamson wrote ...

EDIT:

ok ive found myself on this page:

ive been looking at 50ALL 102-57-25-0000

but is this a good option?
or have i choosen the worst core out of the page?

thanks,
Tom

i like the 50ALL but it sacrifices the H value to get the flat response.

I cant advise you on this matter, as I dont know what your planning. But Id get that core, sooner or later youll want the biggest core you can find for one project or another. ive been trying to follow this thread...

Ash Small

Sat Aug 06 2011, 05:18PM

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

You might find this program useful:

,locale=en.html

It's only applicable to EPCOS cores, though.

I've these EPCOS cores:

and I think the program said I need around 260 turns on the primary for 2.5kW @ 340V DC (Rectified 240V AC) @ 25kHz (the most efficient frequency for these cores), but I don't know if I input all the correct information.

The cores you mention above are apparently more efficient than the ones I have. There is some more information in this thread:

Thomas W

Sat Aug 06 2011, 08:12PM

Registered Member #3324 Joined: Sun Oct 17 2010, 06:57PM
Location:
Posts: 1276

im finding it hard to use the datasheet with the calculator and working out the turns per volt, im thinking of going for 50Kv

because if i can wind that then i can wind anything below that, it may also come in use for running CWs and other misc, the entire plan is just to test myself to see how well i can acctualy make somthing.. im babling on again :P

i plan on making a multi-use driver powered by a Fullbridge and one of my Function Generator IC's

Tom Williamson

Adam Munich

Sat Aug 06 2011, 08:46PM

Registered Member #2893 Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242

Just so you know guys, TSC is backlogged ATM due to many power failures that destroyed a few thousand dollars worth of cores. It'll take a month to ship anything out.

Ash Small

Sat Aug 06 2011, 09:18PM

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

Tom Williamson wrote ...

im finding it hard to use the datasheet with the calculator and working out the turns per volt, im thinking of going for 50Kv

because if i can wind that then i can wind anything below that, it may also come in use for running CWs and other misc, the entire plan is just to test myself to see how well i can acctualy make somthing.. im babling on again :P

i plan on making a multi-use driver powered by a Fullbridge and one of my Function Generator IC's

Tom Williamson

That's pretty much exactly what I'm doing, Tom. I'm using a signal generator for all my preliminary testing, though. I'm not sure yet whether I'll use IC's though for the final design. I might just use an astable multivibrator built from discretes to drive the GDT, but otherwise my aims are identical, 50kV, multi-purpose supply.

Thomas W

Sat Aug 06 2011, 09:31PM

Registered Member #3324 Joined: Sun Oct 17 2010, 06:57PM
Location:
Posts: 1276

cool want to work together on it? :D

Ash Small

Sat Aug 06 2011, 11:57PM

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

Tom Williamson wrote ...

cool want to work together on it? :D

Sure, no probs. Just wish I could get down to Poole this weekend for the Hamfest, my truck's off the road at the moment.

First job is to choose your ferrite cores, though. Patrick and JPSmith are using the ones mentioned above, so is the 'four core' thread (I forget who posted it, I've had a drink or three).

I'm trying to work out the 'volts per turn' thing myself. Patrick said he'd help in PM, but I'd prefer it was done in the forum.

I might end up switching to those cores myself, but I 'picked up' these EPCOS cores, so I feel there is some merit in doing a comparison.

I know Patrick and JP will help, and so will others, We should probably start a new thread on the subject.

Thomas W

Sun Aug 07 2011, 12:12AM

Registered Member #3324 Joined: Sun Oct 17 2010, 06:57PM
Location:
Posts: 1276

yeh good idea, do you want to do the honors of starting it?

Ash Small

Sun Aug 07 2011, 10:46AM

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

Tom Williamson wrote ...

yeh good idea, do you want to do the honors of starting it?

On second thoughts (Now that I've sobered up), this thread should suffice, at least for now, anyway.

I'm currently reconsidering my bobbin design after JP pointed out the problems of HV capacitative coupling to the core. I've even considered using several smaller cores with the secondaries connected in series to overcome this, but I already have the EPCOS cores I mentioned above, so I'll try them first. I have two sets, I'm aiming for 25kV per core. The most efficient frequency for these cores is 25kHz, so that decision has already been made for me. Initially I'll probably use oil for insulation, as it enables wire to be re-used if necessary , where as potting in silicon or epoxy pretty much precludes this option (I had initially hoped to get away with no insulation, but I now think this will just complicate things).

I'm currently playing around with some preliminary circuits with the intention of developing them into gate driver curcuits, and I've found some pretty cheap IGBT's from RS that look like they will be suitable for the H-bridge.

I'm also well underway with a 'monster' rectifier to rectify the 240V mains supply (which I'll also use for DC welding, I blew my last one up, so I've gone a bit over the top with this one). I'll be posting more on this soon.

Working out the 'volts per turn' is the biggest challenge remaining. I've had a quick look at the EPCOS program I mentioned above (I think it was 2Spoons who first posted the link on here), but I've not yet gone into it in sufficient detail to be able to have any confidence in my initial results.

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