In article ,
Randy or Sherry Guttery wrote:

John Byrns wrote:

OK, I see we are going in opposite directions on the coupling effect.
If the coupling were perfect when the core is not saturated, then the
light would be as bright as it could get due to the bucking effect of
the two windings.

Right - up to the "as it could get" with the core NOT saturated - then
the coupling is good - the windings buck - bulb dim.

Either we don't mean the same thing by "buck", or we will each have to
go our own way.

When the transformer becomes saturated decreasing the
coupling, the brightness would have nowhere to go but down due the
residual inductance remaining in the two coils.

This is where you go off track - when the core saturates two things
happen - the inductance of the coils drops through the floor - less
inductance - higher current. The coupling also starts to fail as well -
so the bucking effect also decreases - bulb brighter...

This is where your logic goes wrong, in our perfect idealized
"transformer" with the secondaries connected in the "bucking"
configuration, and no DC in the primary, the inductance is already as
low as it can get, how can the inductance be less than zero when the
"transformer" is saturated?

News Flash, I am really liking the theory I advanced a few messages ago
that the "transformer" is not wound like an ordinary transformer, but
instead has one of the secondaries wound on each outside leg of the
E-core.

Not news - this would be common for a saturable reactor.

And not the case anyway as Dave has now posted a picture of his
"transformer" and all three windings appear to be wound on the center
leg.

The reason I am really liking this theory now is that I looked up the
service data for the General Electric E-155 which has the similar
Colorama tuning system, and the "transformer" is constructed exactly as
I speculated in my earlier message. If the S-W "transformer" is built
the same way then it is a whole new ball game.

Why? If in fact (as I've postulated most recently) that reactance is
indeed the greater control factor - then whether one coil of the two is
reversed or not would only effect the linearity of the control, not that
it works.

My belief all along is that the reactance is the control factor, that is
obvious, there is no other way for it to work. The question is how the
windings are actually connected, if they are connected series aiding
then I can understand how it works. If they are connected so they
"buck" then I don't see how a single leg configuration can work very
well, and the control law would seem to be reversed depending on the
connection, although maybe that's the point.


Regards,

John Byrns

--
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