Core lamination

[TonyTecson]

if i am not mistaken, peter has a preference for "c" cores....

 

[gorgon53]

Does anyone have extensive technical data on the magnetic properties of amorphus cores?
On what i found so fare, i am unable to say how they would compare to traditional core materials if used in a audio OPT. I saw advantages claimed in uses ranging from low to high power high frequency applications to multi-MVA distribution transformers. There migth be some advantages also in audio use, i would like to find out more about this.

 

[gorgon53]

Toni,
since C-cores have the grains aligned optimally there is no question that they outperform stamped laminations. I never said stamped core lamination split magnetic path is advantagous over a C-core single magnetic path option. It propable is not, but that was not the issue.
The issue is that i can only get a 6:1 window ratio AND a split magnetic path with E-Es.
Pieter said he disagree on the advantages of the split magnetic path over the single one.

I can not see why pieter thincks one magnetic path would be of advantage over a split magnetic path. Just as one coil is not advantagous over the 2 split coils of the single core, the single magnetic path is not of advantagous over the split magnetic path of 2 cores.

As pieter simply states "I disagree" i would like to hear why he thincks otherwise.

 

[BudP]

I have privately been asked to contribute to this thread. Not entirely certain why, but here is what I will say.

Pay attention to Pieter. He has a subtle understanding of the interrelationship between the coils he winds, the materials he uses in those coils and the core choices he makes. He chooses to use the core he does because the trade offs he wants to utilize, in the parts he supplies, are best suited by those materials. Under no circumstances should you think that merely by knowing what core he chooses you will understand what he understands. He uses the very same formulas to design his audio transformers that a typical magnetician uses to design his power transformers. This does not indicate that the power transformer designer can match Pieter's skills in audio transformer design.

I choose to use ordinary E/I core. As Pieter will vouch for, my audio transformers are quite good. I have only heard Pieters input splitter toroid, but from that I can tell you he is working at the absolute limits of performance in magnetic design. I understand some subtle things about E/I core that other folks haven't discovered yet, but even if I told you all that I know, you still would not understand how to use the information, though Pieter certainly would.

For anyone to design and build audio transformers, you have to do so. You must work on your own education in music reproduction as provided through audio transformers. Spend considerable time thinking about what you hear from any given audio transformer experiment you have constructied and what it teaches you about what you are doing incorrectly. I guarantee you, you will not end up at the place Pieter, or Dave Slagle, or Per Lundahl or Brian Sowter or a couple more whose names I don't yet know, have ended up. There isn't one answer here. You must learn to trade off the 116 or so divergent variables ( a number provided by one of my early teachers) to arrive at a construct that pleases you musically, or impresses you with "Audio" characteristics you like and then hope that others are also interested in your choices.

Spend some money, purchase some materials, read the RDH4, contemplate Langford Smiths subtle hints. Explore Dr Partridges printed works. Decide what materials you want to work in and make some things. Learn from them. Figure out your own path and join those of us who have spent our life time investigating these fascinating items. Don't ask Pieter to tell you his "secrets", they will not do you one bit of good.

Bud

 

[TonyTecson]

Hey BudP,

thanks for your inputs......i have learned a lot from you.......i agree, one will have to learn what those other guys are not saying, though job but something you learn by doing...

i have built some of my own based on your suggestions and i can they definitely say they really work good to my ears.....i have used Z11's and RM18's both are 0.35mm thick with good results...

i know that Z11 is M6, but RM18, do you know what that is?

i have yet to see Dr. Patridges writings, do you have links?

thanks and regards..

 

[BudP]

Here are three that I have studied. If you cannot find them PM me.

Distortion in Transformer Core N. Partridge The Wireless World June 1932

The Inductance of Iron-cored Coils having an Air Gap G.F. Partridge The London, Edinburgh and Dublin Philosophical Magazine and Journal of Science Vol 22 October 1936 No. 148

Diverse Transformer Loading Problems of Multiple-Speaker Installations N. Partridge The Wireless World February 23rd, 1939

Bud

 

[iko]

I understand some subtle things about E/I core that other folks haven't discovered yet, but even if I told you all that I know, you still would not understand how to use the information, though Pieter certainly would.

I went back in this thread and could find nobody asking you or Peter to say all that you know, or even one little secret. It may be that many of us wouldn't understand some of the subtler things that you have found about transformer design, but some would. However, why don't you say it straight, that you and Peter aren't very open about those subtle things because someone else may gain from that information. And that is fair, to protect your livelihood.

I bought cores from alphacoredirect to try and wind a few chokes and possibly transformers for my own use (I have a day job and no ambition to go into a transformer business; too much trouble, I find). But the offerings of alphacoredirect are somewhat limited. I was wondering about Peter's sources, but he chooses to be silent. I'm fine with that. However, IMHO it's a sad day when one considers a place to buy cores from a secret to be guarded.

For anyone to design and build audio transformers, you have to do so. You must work on your own education in music reproduction as provided through audio transformers. Spend considerable time thinking about what you hear from any given audio transformer experiment you have constructied and what it teaches you about what you are doing incorrectly. I guarantee you, you will not end up at the place Pieter, or Dave Slagle, or Per Lundahl or Brian Sowter or a couple more whose names I don't yet know, have ended up.

Yes, we hear you loud and clear. We're on our own, you got no other advice than to go and do it on our own, as you did. Fair enough.

Don't ask Pieter to tell you his "secrets", they will not do you one bit of good.

With all due respect, you don't know what good it would do to anyone. If you were entirely sure that it would not do anyone any good than you wouldn't be afraid to tell all you know, right? But yes, we will refrain from asking Peter and you for your "secrets."

Thanks for the Partridge references; that, in my opinion, was the only real input you provided, and that is appreciated.

 

[pieter t]

..... I was wondering about Peter's sources, but he chooses to be silent. I'm fine with that. However, IMHO it's a sad day when one considers a place to buy cores from a secret to be guarded.

Silent not so much to guard a secret, but because IMO you guys don't seem to make much efforts to find the sources yourself like I did years ago. You know it is not that difficult, but just plain asking on a forum is still easier it seems.
Actually quite amazing that I pointed someone from the USA in the direction of Alpha cores because he was looking for c-cores, whereas a bit of searching the www will yield plenty "sources".

 

[iko]

Your assumption is wrong. I've been searching for core sources for weeks and could find no other place that sells small quantities other than alphacoredirect. I've even asked privately some of the members here, but nothing so far. I personally loath this kind of attitude; do you really think that you're dealing with little children who need to be taught how to make an effort in life? Never mind your sources. I'd rather spend a few more weeks searching for other sources than have them from you. I feel better knowing that your secret is safely guarded.

God forbid I ask you or BudP for formulas or pointers where to start designing chokes or transformers. 🙂

 

[TonyTecson]

C Core Transformer-C Core Transformer Manufacturers, Suppliers and Exporters on Alibaba.com
Transformer Used Core Lamination-Transformer Used Core Lamination Manufacturers, Suppliers and Exporters on Alibaba.com
http://www.transformercore.com/crgo.htm
Transformer components*-*Core laminations*-*Waasner core laminations, type UI and 3 UI *-*E-Coilwinding, worldwide supplier for all your materials, machines and tools

 

[BudP]

Inductance with gaped core and DC current and ungaped core without DC current:

3.2 X ( Np) squared X ((core square area)X 0.92) X permeability / mean path length X 10 to the eighth

Permeability with gaped core:

1/ (1/ permeability + total gap length / mean path length)

Flux density generated by DC current in Gauss:

0.6 X Np X DC current / full gap width

 

[gorgon53]

I have privately been asked to contribute to this thread. Not entirely certain why, but here is what I will say.

Pay attention to Pieter. He has a subtle understanding of the interrelationship between the coils he winds, the materials he uses in those coils and the core choices he makes. He chooses to use the core he does because the trade offs he wants to utilize, in the parts he supplies, are best suited by those materials. Under no circumstances should you think that merely by knowing what core he chooses you will understand what he understands. He uses the very same formulas to design his audio transformers that a typical magnetician uses to design his power transformers. This does not indicate that the power transformer designer can match Pieter's skills in audio transformer design.

I choose to use ordinary E/I core. As Pieter will vouch for, my audio transformers are quite good. I have only heard Pieters input splitter toroid, but from that I can tell you he is working at the absolute limits of performance in magnetic design. I understand some subtle things about E/I core that other folks haven't discovered yet, but even if I told you all that I know, you still would not understand how to use the information, though Pieter certainly would.

For anyone to design and build audio transformers, you have to do so. You must work on your own education in music reproduction as provided through audio transformers. Spend considerable time thinking about what you hear from any given audio transformer experiment you have constructied and what it teaches you about what you are doing incorrectly. I guarantee you, you will not end up at the place Pieter, or Dave Slagle, or Per Lundahl or Brian Sowter or a couple more whose names I don't yet know, have ended up. There isn't one answer here. You must learn to trade off the 116 or so divergent variables ( a number provided by one of my early teachers) to arrive at a construct that pleases you musically, or impresses you with "Audio" characteristics you like and then hope that others are also interested in your choices.

Spend some money, purchase some materials, read the RDH4, contemplate Langford Smiths subtle hints. Explore Dr Partridges printed works. Decide what materials you want to work in and make some things. Learn from them. Figure out your own path and join those of us who have spent our life time investigating these fascinating items. Don't ask Pieter to tell you his "secrets", they will not do you one bit of good.

Bud

Bud,

all i asked piet was to giv me the reasoning behind his "disagree"
with my simple statet fact that a split magnetic path is advantagous over the single path.....well, i am still waiting...

Instead (you could have simply admitted to the facts, case closed, and we could have proceeded from there) you choose to launch an attack based on assumptions about me. Trying to disguese your real reason , giving me "advice" ( i never asked fore) to the path of gaining the subtle knowledge i possible could not have...come on, who are you trying to fool?

It was not my intention to threath your or piets or anyone elses commercial interrests.

What i know i share freely here amongst DIY-folk.
If you or piet or anyone does not choose to do so, fine, but do it in a honest way please (as piet did).

I admit i was naive in presuming everything discussed here is purely on a technical level and that the possible outcome of it could in one form or an other adversely affect someones busnes. I am aware of the threat of intellectual property theft, but come on guys, we are talking about theoretical stuff regarding transformers. From there, it is as you well know,
a long way to the finished product. I thinck i would not be the only one here who would gladly buy such a product if it where made by combing all the knowledge we have.

I made my living in a broad field of electronics since the begin of the 60th
but i gladly never earlier in my life have i been confronted with the level of arrogance, hiding mostly behind a screen of smoke, as nowdays.

I am glad at least piet did not feel he has to go the path BudP choosed, and as i do not want to cause any more ambaressement here i will end in piets words, i wont discuss the above matter any further, case closed.

 

[BudP]

Usage for the three charts has the following caveats.

The initial perm shown on the commercial iron charts is what you use for 1 vac & 120 Hz.

The max perm shown is for minimum DC permeability, you can expect up to as much as 60% better performance, but no worse. All depends upon the mfg and how well they match the chemicals and annealing on any given day.

The nickle perm charts are for AC. Nickle struggles with DC and can easily self saturate in incremental amounts.

The Hi B chart is for M6. The only interesting squiggle is the vertical oriented hump that shows perm in AC, up the frequency bandwidth. Very important to understand this performance difference between AC and DC permeability. AC permeability begins at the top of the DC flux density.

Now you need to think about the coil. Keep in mind that these are antennas signaling each other within the ferrous boundary of the window. The core is just along for the ride and regardless of the type, it is getting in the way.

Bud

 

[BudP]

Alright Gorgon, here is your answer. Neither is better. Either will provide ultimate audio performance.

Bud

 

[TonyTecson]

so it all boil down to preference....me, i use EI's because i have access to those cores, i have done a torroid only once, core materials are hard to get....so with C cores......

@gorgon53, i asked BudP to join the discussions here as he has been very helpful to me in ways that you would not know...........i will never have the guts to ask him nor peter or any other member for a specific transformer design............but he has given a lot of information in other threads...i guess i am too proud to be spoon-fed...

keeping these guys talking and reading them between the lines is good enough for me.........needless to say, the rest is up to me....

 

[BudP]

E/I core is fine.

Your obstacles are eddy currents and a distinct latency to release from B/H saturation polarity. The eddy currents come primarily from magnetostriction in the leg adjacent to the E/I gap, in alternate lamination patterns, eg 1X1, 2X2, 3X3 etc. A single large gap is plagued by lateral flux transfer and subsequent non linear flux transform across the gap. This is all you need to realize, to think your way to a solution to this problem. Your major plus is that commercial E/I core is all done transferring power at from 250Hz to 440 Hz, M50 to M3 respectively. After that it only determines the rise time of the many planar magnetic fields created within the window.

C core has it's own pluses and minuses and amorphous C core has subtly different minuses and the same pluses. Minuses are a single planar field in the gap, so discontinuities in the gap are a serious problem and power transfer holds on into higher frequencies, with amorphous core being troublesome out to 28k Hz. This forces some choices about how you wind your coils. Pluses are extraordinary to unreal magnetic field rise time and a complete lack of eddy currents and the magnetostriction that causes them.

Double C core provides two planar magnetic fields to disturb with gaps It also divides the coil into two sectors, which can be quite useful when coil factors are in conflict with core permeability, such as you find in amorphous core.

All of these can provide extraordinary performance, once you have thought and practiced your way through solutions to their drawbacks. The end user will have their own music reproduction learning disabilities, at any given time and will prefer one over another. This usually leads to absolute statements about "better".

Bud

 

[Kay Pirinha]

Thank you for your comments, very helpfull.
Is there/was there larger sizes than MD 102 made?

For not to forget your question: No, there aren't. The biggest standardized core is MD102b, which is 54 mm (2 1/4") high, consists of 154 sheets/laminations, each .35 mm thick, and is good for 320 VA as a power transformer.

Best regards!

 

[gorgon53]

Alright Gorgon, here is your answer. Neither is better. Either will provide ultimate audio performance.

Bud

Well Bud, i wont disagree on that (alltough i find "ultimate" exaggregated)
I never said that one TYPE OF TRANSFORMER is preferable over the other.

What i said is: a split magnetic path has advantages over the single path
just as a split coil has advantages over the single coil.

the most basic advantage of the split magnetic path is (given equal Afe, window dimensions, a.s.o) Mfe, the mass of the core, will be considerable less (about 20% with a 3:1 window ratio)

the most basic advantage of the split coil is (given equal Afe, window dimension a.s.o.) lcu, the average length per turn will be considerable less.

We can make a transformer combining the worst, that is a single magnetic path with a single coil.
Unfortunally, we cannot combine the best of both world, a split magnetic path and a split coil.

to avoide any necessary quibble, by split coil i mean one coil on each leg.
And yes, i am aware lme is sligthly different in the cases above wich is not eaxactly to the disadvantage of the split core either. If you want to go into matters like hysteresis loss, first pulse accuracy, airgap, ferrostriction,propagation delay and stuff like that, i am listening

but please, dont disagree on stuff clearcut as the above

 

[gorgon53]

Tony, nothing broken that cannot be fixed

 

[gorgon53]

lme in the above stands for the mean magnetic path length lfe