well.... off the top of my head, transformers convert energy via a magnetic
circuit. In order to convert the energy efficiently, one needs to find out
how much energy can be contained in the core....  then .. with the formulas
relating to the number of turns and current required to produce that so
called "flux", one produces the the primary coil winding. Depending on how
much "coupling" there is between the primary circuit and secondary circuit
(called "k" and is usually a thumbsuck constant, based on density of windings
in bobbin, the kind of material in the core... bla bla bla) you will be able
to detirmine the number of windings to put on the bobbin.

different materials are used as they have different hysteresis curves for the
magnetic flux  and will have different saturation points.

if its a non trivial thing, i suggest you look at the following site and play
with something they produced for a car amplifier. I have used it as a basis
for many of my own projects. The thing to remember, is that  the factor of N
( number of turns) * I ( current through the primary winding)  will produce
the primary exitation flux.... if you remove turns on the primary, the
current will need to increase... vice versa the current.

http://sound.westhost.com/project89.htm


On Tuesday 26 November 2002 09:20 pm, you wrote:
> Can anyone help me with winding a custom inductor/transformer.  The specs
> are as follows:
>    - Input = 29.38 uH, 31.35 mOhms
>    - Output 1 = 0.75 ratio, 54.49 mOhms
>    - Output 2 = 0.23 ratio, 7.64 mOhms
>    - Output 3 = 0.75 ratio, 140 mOhms
>
> Total power output = 20W, current at input winding should be 2A, and freq =
> 100kHz.
>
> How do I go about this?  First, how do I pick a toroidal core, then the
> wire, etc?
>
> I have a link here (
> http://members.tripod.com/~schematics/xform/xformer1.htm ) that explains
> how to wind a custom transformer, but some parameters (like # of lines of
> flux) seem arbitrary, and I feel like I need something more calculated).
> Using the sample lines of flux tells me my primary needs .031 turns of
> wire, etc. Is there a way to determine lines of flux, or another to design
> this transformer.
>
> Cheers,
> -Neil.
>
>
>
>
> ---
> [This E-mail scanned for viruses]

--
Thank-you for your time.

John Ward

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