DIY Power trafo Kit for toroidal power trafo

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So I started making bifilar transformer wire by combining 2 spools of 32ga. onto one...lotsa experements that need bifilar...ok started winding that on big ferrite core and got about 150 turns 'til one broke...had a beer...tried winding with thicker wire; no problem-- think its 20 ga. wound 3 coils of 120 turns each. before i put it down and went to bed I did a sweep 1:2 and 2:1 50ohm generator 10M (?) analog scope: real flat from 100hz to 100k, 5 volts on scope.

Was thinking like 500-600 turns for primary to get 3 coils at approx 25 volts with 120 mains.


Does the primary of a pwer xfmr go outside/over the secondary? Will the ferrite saturate too soon to use 60hz primary? This kit thing pucho posted looks like secondary is wound last, and has steel core...I don't have a tranny to disect.


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so i wound 170 turns of primary...18 ga i think. it sucks at 60hz. works well at 700k resonance though. Below 100 hz waveform is distorted with more than a 10 or 20 volts on either side. this ferrite core won't do for a power tranny...at really low levels (.5 volts) it is exceptionally flat from 60 up to hundreds of Khz with sine - and only slight ringing with square wave


so does anybody know if 50-60hz toroid power xfmrs are always steel coil cores? and if the primary should be wound first or second?

xfmrs i have look like the primary is wound last

I will try this with 34 ga. bifilar when I feel really patient and see if a good 1:1 audio trans can be had.
 
so does anybody know if 50-60hz toroid power xfmrs are always steel coil cores? and if the primary should be wound first or second?

If you ask if there are Ni-core power toroids around, the answer is no. For power toroids, iron is nearly always used. There are two different grades if toroid-core iron available - A-grade and B-grade. A-grade is cores wound with one continous piece if iron sheet, B-grade are wound from cutoff's of all sizes (leftovers from production of "A"s).

A-grade is more transfer-efficient and has higher A(l) - but B-grade behaves a bit like a gapped transformer, allowing a tiny bit of DC current before acting up, making it more usable for some of our audio experiments. But B-grade will need more turns to acheive the same inductance, thus might run into problems with winding capacitance.

Cheap toroids are nearly always B-grade, as the price difference in core material is significant.

The mains-part of the toroid power transformers, the primary winding, is located as the inner winding in 99% of the cases (that is, wound first) - probably to protect from mains-power-hazards in case of mechanical damage to the winding.

This makes it relatively easy to unwind or cut the secondary(s), and rewind to what you need.

Jakob E.
 
Thank you gyraf, Upon further inspection I see the winding structure of the xfmrs I have to be consistent with what you say concerning windings...

The core I was using for diy was a powdered ferrite...I will use these for inductors I guess, or someday build a switching p.s.


So as you say all one needs to do is modify the exterior winding of an existing xfmr to get the desired V out.

very helpful, thank you
 
Interesting. That silicon steel is expensive.
We had a dumpster outside the core cutting machine where I worked chopping lams.
Used to fill it up with ends and bits every year.
Then they would reycle it.
The copper bin from the winder's f'ups was worth a lot more, which took the heat off me. :thumb:
 
i might check it out, i had success adding a phanthom power winding to a xfmr last weekend.

http://www.electronicsurplus.com/commerce/ccp75172-universal-toroid-core-829-0080-40156.htm
 
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