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Old 16th March 2013, 09:50 PM   #421
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maybe cathode feedback here would not be appropriate anyway as it would be a very high % feedback .. way too much anyway ?
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Old 17th March 2013, 01:03 AM   #422
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btw, i am using a cathode feedback in my upcoming 6c33 pp build...

note that cathode feedback winding is also part of the plate winding wrt to turns ratio with secondary.....again phasing is important....

using cathode feedback will require higher drive voltages otherwise, so depending on what you are trying to achieve with your circuit, the decision to use them depends on what your driver circuitry is capable of...

Quote:
some of Pat Turner's winding arrangements have only two layers in their primary sections.
as a designer you are limited only by your imagination, that is why i said earlier on OPT design and building is more an art than science...

generally having more interleavings, (more primary/secondary sections) decreases leakage reactance but also increases shunt capacitance...

if you read the book by Wolpert, simply splitting the primary section in two increases bandwith....

there are subtle techniques used by winders and they are not even mentioned in books, you will only see them once you dismantle a traffo and rewind them...
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Old 19th March 2013, 09:03 PM   #423
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Great thread, Tony. And beautiful work on the transformers - quite inspiring!

Thank you for the practical information and examples you share with the community so freely.

Best regards!

~ Sam
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Old 24th March 2013, 11:43 PM   #424
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I did read this thread, and where a bit puzzled by some, in my view, misconceptions.
May I point out that coreflux is highest in an UNLOADED transformer.
If the secundary is loaded offcourse strayflux increases but coreflux actually decreases.
I thougth this is worth pointing out because it seemed to me that even Tony, otherwise very knowledged in the subject, shared this misconception.
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Old 25th March 2013, 12:28 AM   #425
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Someone also asked what to do with leftover windingspace. In a SMPS or OPT you can get a evenly distributed H-field by spreading the winding evenly.
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Old 25th March 2013, 12:35 AM   #426
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Quote:
Originally Posted by gorgon53 View Post
I did read this thread, and where a bit puzzled by some, in my view, misconceptions.
May I point out that coreflux is highest in an UNLOADED transformer.
If the secundary is loaded offcourse strayflux increases but coreflux actually decreases.
I thougth this is worth pointing out because it seemed to me that even Tony, otherwise very knowledged in the subject, shared this misconception.
thanks for chiming in...a graph or a chart will surely help...while i have built many traffos before, i must admit that i am not that strong with magnetics theory...
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Old 25th March 2013, 12:40 AM   #427
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As to the max power of any transformer there are, in my view, mainly strayflux and temperature-issues that are setting the limits of what can be reasonable done .
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Old 25th March 2013, 01:22 AM   #428
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Quote:
Originally Posted by Tony View Post
thanks for chiming in...a graph or a chart will surely help...while i have built many traffos before, i must admit that i am not that strong with magnetics theory...
Hi Tony,
to me, primarely selfeducated and more of a philosopher, it is all very simple really. If I look at a unloaded transformer all I can see is a chunck of iron and the primary coil. An induktor merely. If we put a voltage to the primary a certain flux will be set up in the core. The max coreflux will be the highest at this point because the Rdc/ac and current dependend voltageloss will be the lowest.
If we load the transformer coreflux will decrease simply because the currentdependend voltageloss in the primary now increases.

Last edited by gorgon53; 25th March 2013 at 01:25 AM.
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Old 25th March 2013, 08:52 AM   #429
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there are two ways to saturate a transformer primary...one is to load the secondary so that the resulting flux density goes over the knee of the magnetization curve, and the other impress more voltage than what was designed for....these two assumed same frequency of impressed voltage...

the third way is to impress the same voltage but at much lower frequency say from 60hz to 20hz...this much i understand....
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Old 26th March 2013, 02:33 AM   #430
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Hi Tony

I hope you where not trying to tell me that loading the secundary would
would lower the frequency?

Now to the flux-thingy, as I see it, please correct me if you thinck I am wrong.
If we connect a load to the secundary this will cause a current to flow. This current produces a secondary fluxfield that OPPOSES the primary fluxfield, therefore it CANCELS some of the primary fluxfield. Since now LESS flux is surrounding the primary the counter emf is reduced and more current is drawn from the source. In other words, the current taken by the primary increases and generates more flux, ALMOST reastablishing the original flux BUT IT CAN NEVER EXCEED IT. Therefore, the highest flux is when the secundary is unloaded.

Last edited by gorgon53; 26th March 2013 at 02:41 AM.
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