Manufacturing my own transformers

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Martin Shahi
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Manufacturing my own transformers

Post by Martin Shahi » Tue Oct 08, 2013 6:50 pm

Hi everyone.
I am wondering where I can get 11 AWG gauge copper wire for winding my own transformers, as I can't seem to find any on eBay.
Also if anybody has any experience winding their own transformers then any tips or tricks would be greatly appreciated.

Thanks.

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Rich Feldman
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Re: Manufacturing my own transformers

Post by Rich Feldman » Tue Oct 08, 2013 9:17 pm

Hi Martin.
Are you looking for magnet wire?
An ebay search turned up some 11 gauge right away, at a starting price of less than $7/lb.
http://www.ebay.com/itm/MAGNET-WIRE-11- ... 0915064726
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Have you considered tweaking your design to accomodate 10 or 12 gauge wire?
If you only need a little bit, such as for the primary of a high frequency switcher, I can give you some.

You could also replace the 11 AWG with, say, three strands of 16 AWG or five strands of 18 AWG.
That's getting down to sizes found at craft stores, beading stores, etc.

I've wound some transformers, but there isn't room here to tell about it.
There are some excellent references on the Internet for the DIY approach,
both for mains frequency (with laminated steel cores) and HF (with ferrite cores).

[edit[ here's a smaller quantity from another vendor.
http://www.ebay.com/itm/Magnet-Wire-11- ... 1085722906
And you could use regular (non-ebay) searches to find magnet wire manufacturers and distributors.
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Chris Bradley
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Re: Manufacturing my own transformers

Post by Chris Bradley » Wed Oct 09, 2013 10:41 am

What sort of frequency are you planning to operate the transformer at?

You need more wire (more turns) at lower frequencies. At higher frequencies you need fewer turns but you hit the skin effect.

10~12 AWG is only good for a 2~4 kHz transformer.

For 20 kHz AC, 20 AWG is the biggest wire before you hit skin effect, if you are using copper or Al wire (forget using any other wire). For square wave 20 kHz you need finer wire than that, as it has higher frequency components in too.

To get to around 1 mOhm/ft resistance (as per 10AWG) you would be better running 10 strands of 20 AWG (10 mOhm/ft).

Martin Shahi
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Re: Manufacturing my own transformers

Post by Martin Shahi » Wed Oct 09, 2013 5:59 pm

Rich Feldman wrote:Hi Martin.
Are you looking for magnet wire?

Have you considered tweaking your design to accomodate 10 or 12 gauge wire?
If you only need a little bit, such as for the primary of a high frequency switcher, I can give you some.
Thanks Rich, I feel like a bit of a fool for not spotting that it's called magnet wire but at least I've learnt from my mistake. Thanks
for offering to give me some wire, but I live in the UK so that's probably not an option (I'm assuming you live in the US).
Also you mentioned about laminated steel cores and ferrite cores. I was planning to buy this: http://uk.farnell.com/ferroxcube/u126-9 ... dp/2103420
to use as my core but is that not possible as I am going to be using mains frequency? Also in regards to steel cores, I can't seem to find any of those either without having to buy a fully assembled transformer and disassembling it.

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Chris Bradley
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Re: Manufacturing my own transformers

Post by Chris Bradley » Wed Oct 09, 2013 6:20 pm

You've still not mentioned the application. Would you not think the usefulness of the information you get depends somewhat on being clear what it is for?

Try http://www.sowter.co.uk

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Rich Feldman
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Re: Manufacturing my own transformers

Post by Rich Feldman » Wed Oct 09, 2013 10:48 pm

Hi Martin.
Yes, I think most E-I cores used by amateur transformer winders are obtained by taking apart an existing transformer.
I think the laminations are being re-used in this youtube video:
http://www.youtube.com/watch?feature=pl ... QCBI#t=883
It's one of the rare cases where one or two parts will usually, and acceptably, be left over when the rest go back together. :-)

You should learn how to calculate the required number of turns per volt (or volts per turn), which depends on frequency and core size and core material.
Ferrite materials need 3 to 6 times more turns than steel (for same voltage, frequency, and size), so they're hardly ever used for mains frequency.
The balance tilts to ferrites at high frequency, because steel is electrically conductive and gets large eddy current losses even in thin laminations.
Transformer steel alloys contain silicon because it's an economical way to drive up the electrical resistivity, without much compromising the mechanical and magnetic properties.

Here's one well-illustrated article about DIY transformer rewinding.
http://ludens.cl/Electron/trafos/trafos.html

Here's a series of articles with all the theory and formulas you will need. Reading it through will be less work than making your first good transformer.
http://sound.westhost.com/xfmr.htm
http://sound.westhost.com/xfmr2.htm
http://sound.westhost.com/articles/xfmr3.htm
All models are wrong; some models are useful. -- George Box

Martin Shahi
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Re: Manufacturing my own transformers

Post by Martin Shahi » Thu Oct 10, 2013 4:02 pm

Thank you very much Rich. Sorry Chris I should have made that clear. It is for a full neutron producing fusor.

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Chris Bradley
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Re: Manufacturing my own transformers

Post by Chris Bradley » Thu Oct 10, 2013 5:13 pm

Martin Shahi wrote:Sorry Chris I should have made that clear. It is for a full neutron producing fusor.
'Fraid your information is still slightly less useful than a chocolate tea pot.

I was asking what is the input voltage, current and waveform type/frequency you want to put into it, and what do you want to get out of it?

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