Tony's latest traffo DIY build - Page 45 - diyAudio
Go Back   Home > Forums > Amplifiers > Power Supplies

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 4th April 2013, 09:37 PM   #441
diyAudio Member
 
Join Date: Nov 2006
Quote:
Originally Posted by Tony View Post
of course not.....



some explanation here... Magnetic Hysteresis Loop including the B-H Curve
Click the image to open in full size.

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....
Flux and field strength are not the same thing, offcoure H field goes up when you load the secundary wheras fluxdensity B (depending on the resistance of the windings) sligthly decreases.
In a OPT with M6 iron at 0.8T givs the highest inductance. I strive for at most 0.8T at 20Hz (guarantees 0.4T above 40Hz).Below 0.4T is something worth to strive fore. Why? Simply because distortion really starts to increase above levels of 0.4T wheras at levels below 0.4 T is does not decrease by much. For the same reason it is important to me to have the best possible balanced tubes in a PP amp, I would not be very happy to have things f...d up by a unnecessary addional Bdc. Keep Btot below 0.4T above 40hz (where most of the action is) and you are a step closer to have something worth listen too. This way, according to a guy that knew a thing or two bout transformers, additional transformer distortion will stay below 0.04%

Last edited by gorgon53; 4th April 2013 at 10:03 PM.
  Reply With Quote
Old 4th April 2013, 09:46 PM   #442
diyAudio Member
 
Join Date: Nov 2006
In case anyone is interrested, the guy I reffered to was either Sowter or Partridge, sorry I can not remember wich of the gentlemans, both deceased times ago, but they knew stuff long forgotten since and propable not yet rediscovered
  Reply With Quote
Old 4th April 2013, 10:13 PM   #443
diyAudio Member
 
Join Date: Nov 2006
Quote:
Originally Posted by tinitus View Post
might have been Lundahl
I know at least Beyer used some true zero-airgap cores, does Lundahl too?
  Reply With Quote
Old 4th April 2013, 10:25 PM   #444
AJT is offline AJT  Philippines
diyAudio Moderator
 
AJT's Avatar
 
Join Date: May 2003
Location: Palatiw, Pasig City
Quote:
Originally Posted by existenz View Post
Hey guYs, sorry for the off topic, could you please tell how I could detect if a traffo is burnt or not? i mean without put power on it. Theres some test with DMM i can do on it?
Thanks for any help!
nick
burnt traffo smells......when end-bells are removed, you can see the charred paper layers, even the coppers turned black....
__________________
the best advertisement for a good audio design is the number of diy'ers wanting to build it after all the years....never the say so of so called gurus....
  Reply With Quote
Old 4th April 2013, 11:57 PM   #445
diyAudio Member
 
Join Date: Feb 2013
I didnt know that dc from DMM could damage transformers, although i don't think that mine Are a zero air gap core...
I wonder, with a continuity test, testing Primary leads together should be open right? I ask that because i have same old trafo and doing continuity test some are buzzing and other don't..so i'm afraid to connect to 230v things shorted!
there's some minimun ohmic value i should read both on primary leads and secondary leads according to different output values? Ie 230v to 12-18-24v
Thanks for your patience, i'm new on the matter! I know, These are maybe stupid questions for you guys!
  Reply With Quote
Old 5th April 2013, 09:08 AM   #446
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Mains transformers will not be damaged by applying DMM test probes to the leads.

They were talking about signal transformers that are VERY sensitive to DC offset currents.
__________________
regards Andrew T.
  Reply With Quote
Old 5th April 2013, 03:05 PM   #447
diyAudio Member
 
Join Date: Feb 2013
Quote:
Originally Posted by AndrewT View Post
Mains transformers will not be damaged by applying DMM test probes to the leads.

They were talking about signal transformers that are VERY sensitive to DC offset currents.
Ah ok ok thanks Andrew for the clarification!
  Reply With Quote
Old 9th April 2013, 12:53 AM   #448
diyAudio Member
 
Join Date: Nov 2006
Quote:
Originally Posted by AndrewT View Post
How does one measure the thickness of the lamination in a toroid when it is completely hidden from view?

How can one be sure that 1T and 1.5T are the best performance targets for the two thicknesses that you quote?

What if the thickness is other than the two you quote.

I am trying to find a method that is fairly simple that can confirm that the correct number of turns have been wound onto the core.
You do not need to know the thickness of the lamination if you have a coil on the iron. If there is no coil you will have to wind one and then find the volts per turn that gives the highest no load impedance. The highest inductance is with M6 at around 0.8T. In a OPT use 0.8T as maximum at your lowest desired frequency. In a M6 mains transformer 0.8T gives best iron loss efficiency and low magneto striction (mechanical noise). It also limits the B to maximal 1.6T during switch on. It comes with a cost, relative copper losses go up, over all efficiency will go down. If the measured highest impedance is at at a higher calculated B than 0.8T then your iron is something better than M6, if lower than it is a lower quality iron. If you want the highest power for a given iron you can increase your V/turn up to a max of 2 times of the value where you measured the highest no load impedance. 2 times is the about the max, so with allowance for 10% over voltage this would be 1.46T at the nominal input voltage. With M6 iron 1.4-1.5T is what most professional transformer manufacturers would use in order to be able to compete with other products that are maxed out for power and overall efficiency. The above is for EI, UI and M iron in the sizes we use in audio. With a toroid or C core somewhat higher induction can be used.

Last edited by gorgon53; 9th April 2013 at 01:23 AM.
  Reply With Quote
Old 9th April 2013, 02:32 AM   #449
diyAudio Member
 
Join Date: Nov 2006
Also, there is no such thing as "correct number of turns". There are only designer choices that have to be made. A transformer designer/manufacturer may choose the highest B he can get away with because he wants the highest power with as little costs as possible. On the other hand, Tony for instance, uses a comparable low B to make sure his transformers perform well in his audio projects.
I remember a case when a 10kVA transformer where "upgraded" to 16kVA just by stamping 3x400V (instead of the 3x380V he used earlier) and temperature class "F". Same iron, same coils, all that changed was a few pieces of higher temp class isolation sleeves and a new "licence plate" and price tag. The customer had to pay twice for this new invention, first the higher purchase and over the years the additional energy cost due to higher losses and he got also rewarded with lousier regulation and shorter life expectancy.
There is no correct number of turns, power rating a.s.o, only different choices that can be made

Last edited by gorgon53; 9th April 2013 at 02:39 AM.
  Reply With Quote
Old 9th April 2013, 04:10 AM   #450
AJT is offline AJT  Philippines
diyAudio Moderator
 
AJT's Avatar
 
Join Date: May 2003
Location: Palatiw, Pasig City
Quote:
Originally Posted by gorgon53 View Post
Also, there is no such thing as "correct number of turns". There are only designer choices that have to be made. A transformer designer/manufacturer may choose the highest B he can get away with because he wants the highest power with as little costs as possible. On the other hand, Tony for instance, uses a comparable low B to make sure his transformers perform well in his audio projects.
I remember a case when a 10kVA transformer where "upgraded" to 16kVA just by stamping 3x400V (instead of the 3x380V he used earlier) and temperature class "F". Same iron, same coils, all that changed was a few pieces of higher temp class isolation sleeves and a new "licence plate" and price tag. The customer had to pay twice for this new invention, first the higher purchase and over the years the additional energy cost due to higher losses and he got also rewarded with lousier regulation and shorter life expectancy.
There is no correct number of turns, power rating a.s.o, only different choices that can be made
i am glad that you made this comment, it is obvious that those who do not make transformers are unaware of this, i have been giving this hint for a long time now.........
__________________
the best advertisement for a good audio design is the number of diy'ers wanting to build it after all the years....never the say so of so called gurus....
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
tony's 6LU8 push-pull power amp build AJT Tubes / Valves 22 23rd February 2013 06:21 AM
Trinium, my latest build Mark.Clappers Multi-Way 18 17th July 2012 07:07 PM
My latest CHR-70 build tresch Full Range 8 6th December 2011 12:34 AM
My Latest DIY Draft (Beta) Build - Resurrected Sansui AU-111 LinuksGuru Tubes / Valves 0 27th December 2010 10:59 PM
My latest build SS 23W smithy666 Subwoofers 6 14th April 2009 11:50 AM


New To Site? Need Help?

All times are GMT. The time now is 03:26 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2