winding your own transformer
From: davmckin [SMTP:davmckin-at-ix-dot-netcom-dot-com]
Sent: Tuesday, February 03, 1998 4:04 AM
To: Tesla List
Subject: Re: winding your own transformer
Tesla List wrote:
> From: Tabbal [SMTP:bigboss-at-inquo-dot-net]
> Sent: Monday, January 26, 1998 4:00 AM
> To: Tesla List
> Subject: Re: winding your own transformer
> > I've had quite a bit of experience with transformers. I've worked with
> > tesla coils for about 18 yrs. now and have been a High Voltage, High
> A question for the Transformer experts out there... Why do we center-tap
> them? I just haven't been able to figgure out what this does.
> Also, I have a project I'm looking at that calls for the following custom
> 4 turns, center-tapper primary, 16 turns, center-tapped secondary; 5-mil
> copper foil wound on a Ferroxcube ETD-34 core.
> So, the center-tap question applies here, but do they want the actual
> windings to be copper foil? Seems like an odd matterial to use for a
> Transformer. I assume it must be insulated by me with paper or something.
> Would Polyethelene work? It's for lower voltages, should peak at about
> If it is to be wound with foil, the tap could just be a wire soldered on
> at the middle of the winding, right?
Dear Travis & all,
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
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
David L. McKinnon
High Voltage / Transformer Engineer