Re: About leakage inductance in transformers

MassiveProng wrote:
On Tue, 06 Mar 2007 16:14:01 +1300, Terry Given <my_name@xxxxxxxx>
Gave us:


why do you think windings are interleaved? not to maximise coupling to the core, but to maximise coupling to *each other*.



Not all transformers have "STACKED" windings. Interleaved is an
entirely incorrect term, dope.

look harder.

stacked <> interleaved.

and not all stacked windings are interleaved.


I have several designs that use a segmented bobbin, and the primary
is at one end, and the secondary spans the rest of the bobbin. The
reason is isolation as well as the fact that some 1700 plus secondary
turns were required. If you know anything about transformers, you
would know that the number of turns that can be safely nested together
is limited by the breakdown strength of the insulation on the mag
wire. Typically a max of a few hundred. That is why one will see a
layer of secondary windings, covered by tape, and then another layer
wound over that one. It is even referred to as a "layered build".

indeed.


If one places too many turns on one bobbin segment, the longevity of
the transformer is in serious jeopardy as the voltage differential
from the first turn to the last is so high that breakdown is likely.

hence, for example, progressive- or jumble-winding. zig-zag winding is exactly wrong for this purpose (and serves to maximise end-to-end winding capacitance)

There are even transformers where the primary and secondary are on
separate bobbins on opposite sides of the core.

Philips/ferroxcube used to make a 2-part ETD29 bobbin, for much the same reason (its not in the 2000 ed of MA02). one bobbin fit entirely inside the other, so creepage & clearance was very high.

Nowadays one would simply use TIW, unless its an HV transformer.


SO YES, it is the
core that passes the energy, you stupid dip***.

all these types of transformers have poor coupling.

I suspect your experience is limited to HV transformers, where dielectric breakdown, corona etc considerations dominate, and you just have to live with poor coupling.

for non-HV applications, its all about maximising coupling.


how about this then: Assuming I can live with the resistive losses, the amount of power I can bung thru a transformer is NOT limited by the core.

You still havent responded to my challenge.

Cheers
Terry
.