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Transformer winding, how to?

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neazoi

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Hi I have built this in a single core

View attachment 158580

https://www.allaboutcircuits.com/uploads/articles/out-of-phase-dc-control-windings.jpg

It is from the page https://www.allaboutcircuits.com/te...ent/chpt-9/special-transformers-applications/

To build the primary I took a piece of 20cm wire, then bent it at the middle (10cm) and fold it back so I can have a bifilar wire. Then I wound this bifilar winding on the primary. So the winding starts from the start of one of the wire ends, and then ends to the folded point, then continues backwards into the other wire end. The two wire ends are the connection points of the primary. The folded point is left unconnected.

Do I make this right?
 
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If I understand right, you are trying to build a saturable reactor. The type shown in the first link can't be build on a single core. Sending current back forth through the bifilar winding has just just zero effect.
 

The diagram is a saturable reactor (as described in the linked article). (AKA magnetic amplifier.) The dots indicate orientation of the windings. The DC side (control side) has its windings oriented so as to suppress AC induced in them from the AC side (power side).

Seems as though you wound the DC turns correctly. The article states you can have a single core despite the diagram showing two separate cores.

This phasing of control windings can be accomplished with two separate reactors as shown, or in a single reactor design with intelligent layout of the windings and core.

out-of-phase-dc-control-windings.jpg

Evidently the two halves of the AC cycle (positive & negative) allow proper flux building and collapsing, as well as the effect within the windings.
 

If I understand right, you are trying to build a saturable reactor. The type shown in the first link can't be build on a single core. Sending current back forth through the bifilar winding has just just zero effect.

I thought so. But I read these "Ferristor" scans and they show the control windings onto the same core. That is weird.
 

you need an EI core at least with wdgs on the outer legs - as well as the central leg ...
 
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    FvM

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you need an EI core at least with wdgs on the outer legs - as well as the central leg ...

I think you are right. It can't be done in a single toroid. How about a binocular, using it as an ei core??
 

Yes, using 2 x toroids is possible - just a bit untidy looking ...
 

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