Just for interest,
I'm sure it will create some interesting debate.
Output Transformers
Regards
M. Gregg
I'm sure it will create some interesting debate.
Output Transformers
Regards
M. Gregg
Some of his explanations are a bit clumsy, but it's also not an article for instruction in design (there's "Wolpert's" for that). One thing he mentions is the use of small OPTs for cheapness. What he doesn't mention is that this also helped suppress 60Hz hum in cheap radios that operated straight off the AC mains (using 34W4s or 35Z5s for the DC rail) with very inadequate PS filtering. If the low frequency -3.0db point is 200Hz, you don't hear as much hum. Of course, these things sounded hideous then and now (and should never be used without an iso PTX). The whole thing was designed for cheapness, not just the OPT.
Tinitus,
He said that because of blind faith in old methods, transformers are still made that way instead of using new materials .....
I think the article is a good introduction for those new to the output transformer. It is not meant as a design instruction, no figures are given. RDH4 etc. give design procedures, often loosing newbies in the detail.
I have one problem however - perhaps those using the modern means can comment. I disagree that better 'filling' of the former is achieved by 'layerless' winding. Especially when using thin wire it is impossible in practice to wind in layers without using interleaving - the end result is invariably somewhat random winding, with eventually more space wasted in wires crossing one another than with neat interleaved winding. Also, I find it hard to calculate the final result with that kind of winding - which to my knowledge is done with most transformers these days (I possibly stand to be corrected).
I also wonder about the previous 'unsafety' of wire insulation. Nowhere is there a large potential between layers, only between sections - and there the section insulation withstands the voltage, not the wire insulation. I also wind my own transformers, mainly because local winders refuse to layer-wind (with interleaving) any more. More time-consuming possibly, but then I know what I have, closely corresponding with calculations.
As an aside, I (also?) found that with more than 3 - 4 secondaries, capacitance becomes the h.f. limiting factor, not leakage reactance (depending of course), particularly when splitting/interleaving primary into sections for improved coupling required in class-AB.
He said that because of blind faith in old methods, transformers are still made that way instead of using new materials .....
I think the article is a good introduction for those new to the output transformer. It is not meant as a design instruction, no figures are given. RDH4 etc. give design procedures, often loosing newbies in the detail.
I have one problem however - perhaps those using the modern means can comment. I disagree that better 'filling' of the former is achieved by 'layerless' winding. Especially when using thin wire it is impossible in practice to wind in layers without using interleaving - the end result is invariably somewhat random winding, with eventually more space wasted in wires crossing one another than with neat interleaved winding. Also, I find it hard to calculate the final result with that kind of winding - which to my knowledge is done with most transformers these days (I possibly stand to be corrected).
I also wonder about the previous 'unsafety' of wire insulation. Nowhere is there a large potential between layers, only between sections - and there the section insulation withstands the voltage, not the wire insulation. I also wind my own transformers, mainly because local winders refuse to layer-wind (with interleaving) any more. More time-consuming possibly, but then I know what I have, closely corresponding with calculations.
As an aside, I (also?) found that with more than 3 - 4 secondaries, capacitance becomes the h.f. limiting factor, not leakage reactance (depending of course), particularly when splitting/interleaving primary into sections for improved coupling required in class-AB.
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