Loosely coupled transformer windings

I would like to wind a transformer with one "closely-coupled" secondary and
one "loosely-coupled" secondary, for current-limiting. I understand that
increasing the air gap in the centre leg of an E-core will decrease the
coupling co-efficient, but how do I do it for only one winding? If I use an
E-core with a gap and wind two windings on top of each other on one side,
will they be more closely coupled than a winding on the opposite side of the
core and can I then vary the coupling of the secondary by varying the
air-gap, while maintaining closer coupling between the primary and the
feedback windings? (As you can tell, I'm a relative newbie to fluoro
inverter design, but I'm willing to learn.)
(I've posted a drawing on my website, (12.5K JPEG):-
http://www.dolevoiceaustralia.com.au/question.html )

This is for a complementary drive rapid-start fluoro inverter. I want a high
voltage, ~1kV, to get things started, then under load or reduced frequency
I want
the voltage to drop heaps to one or two hundred volts.

Any help would be appreciated.

.... Steve




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Relevant Pages

  • Re: Loosely coupled transformer windings
    ... will they be more closely coupled than a winding on the opposite side of the ... core and can I then vary the coupling of the secondary by varying the ... Steve, the way you show it is generally the way it is done, except that the center leg of the core is often a separate chunk of core with an air gap at each end, that is slid between the primary and secondary sides of the outer core. ...
    (sci.electronics.design)
  • Re: UL or CFB plate curves
    ... >>> Then caps can be placed from anode winding to cathode winding ... giving more capacitance and closer coupling. ... The UL screen connection is an application of NFB imho. ...
    (rec.audio.tubes)
  • Re: Loosely coupled transformer windings
    ... My drawing probably wasn't too clear, but there was an air gap in the middle ... leg. ... I figure that I can wind the 3 windings, ... then increase the air gap to reduce the coupling to the secondary until, ...
    (sci.electronics.design)
  • Re: UL or CFB plate curves
    ... >> Then caps can be placed from anode winding to cathode winding ... giving more capacitance and closer coupling. ... floating power supplies replacing bifilar winding. ... >Arguably the screen connection should not be called feedback ...
    (rec.audio.tubes)
  • Re: Variable inductor
    ... winding and the winding should cause fields that cancel in the ... middle leg. ... Actually "no coupling" is a bit of an overstatement. ...
    (sci.electronics.design)
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