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...
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...
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...
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...
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.
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...
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.
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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....
the third way is to impress the same voltage but at much lower frequency say from 60hz to 20hz...this much i understand....
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.
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.
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of course not.....
some explanation here... Magnetic Hysteresis Loop including the B-H Curve
An externally hosted image should be here but it was not working when we last tested it.
magnetic field strength relies on the current flowing in the coils, since the number of turns is fixed, the magnetic path length is likewise fixed, so that the only varialble left is the current in the coils....
when i make my traffos, i make sure that i operate well below the knee of the magnetization curve, when unsure of the quality of the iron i have on hand, i operate at 0.6T, when using M6 i go to as high as 1T, this is so that i can avoid saturation conditions....
yes, those values are for highest grade materials, but even then i still will not use them as such...
truth is, there are more than a dozen ways to build your transformers, it is entirely up to you....there are guidelines and they are not set in stone.....
Patrick Turners' writings are what i really consider seriously...there is also Norman Crowhurst and the RDH3 and 4....
more than the numbers crunched in these write-ups, there are bits and pieces to be gleaned, you just need to alert about these....
and if you have been building traffos, you will recognize them as you see them...
Commercial considerations
Tony, I really respect your work and all of the transformer projects that you have shared in this thread. If I ever get the bug to take on another obsession, it will surely be winding transformers!
I will add that commercial vendors probably push their cores to the limit - especially the "less expensive" transformers available commonly on eBay. I have seen numerous references to transformers running "warmish", and based on your descriptions I really do suspect the manufactured products (especially the lower-cost versions) tend to load up the transformers with little or no margins.
I have experienced this myself with simple EI core transformers that, when run for long periods, get unreasonably hot when loaded anyway near the rated outputs.
The custom designs you create take advantage of the experience you've learned (no doubt the hard way
), and I really do respect your giving generous margins on the designs. After all, if a person is going to invest the hours and hours of labor to wind their own transformers why take the cores to the limit? You are certainly not doing it to save money, especially on a production line - but rather to get EXACTLY the worry-free performance you want in your designs!
Please keep inspiring us with your designs and knowledge - your skill is in danger of becoming a "lost art" and it's dedicated folks like yourself that keep important aspects of the electronics world alive!
~ Sam
Tony, I really respect your work and all of the transformer projects that you have shared in this thread. If I ever get the bug to take on another obsession, it will surely be winding transformers!
I will add that commercial vendors probably push their cores to the limit - especially the "less expensive" transformers available commonly on eBay. I have seen numerous references to transformers running "warmish", and based on your descriptions I really do suspect the manufactured products (especially the lower-cost versions) tend to load up the transformers with little or no margins.
I have experienced this myself with simple EI core transformers that, when run for long periods, get unreasonably hot when loaded anyway near the rated outputs.
The custom designs you create take advantage of the experience you've learned (no doubt the hard way
), and I really do respect your giving generous margins on the designs. After all, if a person is going to invest the hours and hours of labor to wind their own transformers why take the cores to the limit? You are certainly not doing it to save money, especially on a production line - but rather to get EXACTLY the worry-free performance you want in your designs!Please keep inspiring us with your designs and knowledge - your skill is in danger of becoming a "lost art" and it's dedicated folks like yourself that keep important aspects of the electronics world alive!
~ Sam
strip wound C cores and toroids can be run as high as 1.7T with regular iron.
losses are relative
thanks for the heads up, as i said i work with mostly surplus cores, the new virgin cores available here are the lowest grade steel there is, that is why i run them at 0.6T up to about 0.9T depending on applications...
while C cores are to be found here, without knowing the source it is is hard to say they can do 1.7T so i always assume they can not....
Tony, I really respect your work and all of the transformer projects that you have shared in this thread. If I ever get the bug to take on another obsession, it will surely be winding transformers!
I will add that commercial vendors probably push their cores to the limit - especially the "less expensive" transformers available commonly on eBay. I have seen numerous references to transformers running "warmish", and based on your descriptions I really do suspect the manufactured products (especially the lower-cost versions) tend to load up the transformers with little or no margins.
I have experienced this myself with simple EI core transformers that, when run for long periods, get unreasonably hot when loaded anyway near the rated outputs.
The custom designs you create take advantage of the experience you've learned (no doubt the hard way
Please keep inspiring us with your designs and knowledge - your skill is in danger of becoming a "lost art" and it's dedicated folks like yourself that keep important aspects of the electronics world alive!
~ Sam
thanks, back in the 70's i wanted to have a made to order power traffo for a simple ss amp, since tubes were still very much in season then, the shops i went to, said they could not do it and thought i was crazy.....that started me in the traffo making hobby.....
DIY'ers are not concerned with the same issues as commercial offerings, that of engineering economics and profits.....
btw, i have enlisted the hep of my wife, she stacks E-I's for me nowadays...
Attachments
might have been Lundahl, but I read somewhere that you can damage a trafo simply by trying meaure with digital ohm meter
extremely high permeability cores with 0 airgap would inreversible detoriate whit the the slightest trace of dc magnetisation