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winding your own transformer




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From:  Tabbal [SMTP:bigboss-at-inquo-dot-net]
Sent:  Tuesday, February 03, 1998 4:15 AM
To:  Tesla List
Subject:  Re: winding your own transformer



On Tue, 3 Feb 1998, Tesla List wrote:

> The ETD-34 toroidal ferrite core is a Magnetics core
> part no. P-43434-EC-00/P-43434-EC-XX where
> XX is the desired core material listed as numbers 20, 21,
> 22, or 23 - depending on the desired core material.
> 
> No. 20 - AL = 135
> No. 21 - AL = 195
> No. 22 - AL = 285
> No. 23 - AL = 410

Toroidal?? Hmmm.. the pic I saw looked like the typical square shaped
transformer.. are they build from multipule cores? And what material would
I want for this thing? 

> 4 Turns center-tapped primary with 16 turns center-tapped
> secondary sounds like a transformer operating in a push-pull
> configuration or possibly a current driven inverter operating
> at approximately 300 kHz.  As far as the windings being Cu
> foil - yes they need to be foil based on the guesstimation that
> this transformer is operating at 300 kHz and using a fairly high
> current with the necessity of having a low impedance as possible.
> As far as insulation is concerned - it really depends on whether
> the core comes as a insulated core and the windings lengths as
> to whether insulation is required between the primary and secondary.
> That would be difficult to answer without further information on the
> original transformer.  If you'd be so kind as to provide a little more
> input as to the project, this would immensly aide in answering your
> question.

I believe it is used in a push-pull config. It's driven by 12VDC input and
the circut connects it to an IC that is handling the power conversions..
I'd give the part number but I don't have the schematic with me. It's to
be used in an audio amplifier, as the main power transformer. 

I had a reply on here about winding the coils in two parts, each would the
opposite direction from the other with the center tap being the inside
connection of both sides and the two parts wound in opposite directions. I
assume since I'm dealing with bare copper here I need some kind of
turn-to-turn insulation. And something for the primary-to-secondary
windings. 

All my info on this is comming from plans and I don't have an orriginal to
look at or I'd just take it apart and figgure it out as I went. :) I'm not
too fammiliar with transformer theroy, I asked on here as Tesla Coils are
just big transformers. :) (OK, over-simplified)

Any info you can provide would be welcome as I'm just taking shots in the
dark here. :)

Travis