Typically, transformers are wound with the primary closest to the core.=20
This aids the flux entering the core with the most strength, and
therefore, providing the most coupling between windings and inproving
efficiency.

Also, it depends on the use of the transformer as to which way the
secondaries are wound.  Generally, they are all wound in the same
direction.  However sometimes they are wound counter to the primary, or
each other in some cases.  Usually the start of a winding will have a
dot at thst point on the schematic.
And if it is wound counter, the voltage out will be 180 degrees out of
phase with the primary.

Hope this helps.

Regards,

Jim

> -------- Original Message --------
> Subject: Re: [EE] transformer winding direction
> From: Manu Abraham <abraham.manu@gmail.com>
> Date: Sun, March 17, 2019 9:39 am
> To: "Microcontroller discussion list - Public." <piclist@mit.edu>
>=20
>=20
> Replying to my own post,
>=20
> On second thoughts the interleaved layering would cause an imbalance,
> since not all layers are linked withe same amount of flux, which
> brings me to:
>=20
> L #1 100T Sec
> L #2 6T Pri
> L #3 100T Sec
> L #4 6T Pri
>=20
> That said, 2 questions again:
> #1. Should the Primary be in Layer #1, or is it better to start with
> the Secondary ?
> #2. Both the Primary and Secondary should be would in the Clockwise
> direction itself ? (I hope so)
>=20
> Thanks,
> Manu
>=20
>=20
> On Sun, Mar 17, 2019 at 3:45 PM Manu Abraham <abraham.manu@gmail.com> wro=
te:
> >
> > Hi,
> >
> > Looking at a transformer, primary 12T secondary 200T, step-up
> >
> > The primary is split in two, the secondary in 3, to reduce leakage indu=
ctance.
> >
> > ie,
> > 1. L1. Secondary  50T
> > 2. L2. Primary  6T
> > 3. L3. Secondary  50T
> > 4. L4. Secondary  50T
> > 5. L5. Primary  6T
> > 6. L6. Secondary 50T
> >
> >
> > L1 and L3 (secondary) are at opposite sides of the secondary.
> >
> > In which case isn't the direction of the flux changing ?
> > So, when L1 is wound clockwise, shouldn't L3 be wound in a
> > counter-clockwise fashion ?
> >
> > Am I thinking right, or thoughts in the wrong direction ?
> >
> > Apart from the original questions, any thoughts on a better
> > methodology to reduce leakage inductance ?
> >
> > Any thoughts ?
> >
> > Thanks,
> > Manu
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