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27th March 2002, 09:39 AM  #1 
diyAudio Member
Join Date: Dec 2001
Location: Romania

Toroidal transformers calculations
Can anybody tell me where can I see toroidal transformer calculation . I want to built my own transformer for power supply.
Thank you very much ! 
27th March 2002, 12:18 PM  #2 
diyAudio Member
Join Date: Oct 2001

Similar to 'normal' transformer calculation. Make sure the windings are linear distributed around the entire core, both primary and secundary windings, to reach maximum coupling.

27th March 2002, 01:13 PM  #3 
diyAudio Member
Join Date: Jan 2002
Location: Labrador City

I've often considered winding my own transformers but I could never find out how many turns should be used for the primary. Has anyone ever looked into this?
Thanks, Stephen 
27th March 2002, 06:20 PM  #4 
The one and only

It's a complicated enough formula with core characteristics,
AC voltage and Frequency. I have only designed some switching toroids, but the general formula for that is: E = (4.4 x 10^8) * F * N * B * A Where E is the peak voltage F is the frequency N is the number of turns in the winding B is the core flux density A is the cross section of the core A number of books deal with this issue; I pulled this out of Gottlieb's "Power Supplies  Switching Regulators and Converter's" which is not necessarily a highly rated book according to the reader feedback on Amazon, and there are probably better. 
27th March 2002, 08:25 PM  #5 
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Join Date: Dec 2001
Location: Romania

Thank you for answeres !
What kind of material is used for core and the calculations for surface is similar with normal transformers ? I have one core with surface of sections at 12 square centimeters (from an old toridal transformes 800VA 230v/70v) and I want to know how many turns per volt should be used and why. The normal transformers calculations are: Power (VA) = S x S x 0,85 (where S is the surface of sections in sq. centimeters)) In my case will be : 12 x 12 x 0.85 = 122,4VA but is wrong becouse the old transformer was rated at 800VA. The number of turns per volt ( n ) for "normal trafo" is : n = 45/S for 50Hz and 230V ~ AC In my case will be : n = 45/12 = 3,75 turns /volt bit is wrong again becouse the old transformer has 2,1 turns/volt. For me is not a problem to calculate this transformer . I want to know the relations [sections of surface]  [turns/volt] for toroidal transformers . Thank you again ! 
27th March 2002, 08:56 PM  #6 
diyAudio Member
Join Date: Mar 2002
Location: USA

At the web site www.toroid.com/kits.htm, you can find toroidal transformers kits from 80VA750VA (I think). And with each kit the manual is suppose to have info and pictures of how to wound and calculate the primary and secondary voltages. The company is Toriod Corporation of Maryland which is pretty well know.
Also at SDS Labs Audio Design there WAS a how to section with info and pictures of how some one built up one of these toroid kits. The SDS Labs web site can be found in the Directory section below on DIYaudio site under Amplifiers in Projects. I mean WAS cause I have tired to enter the site but I get" Page Not Found" message. Maybe they are updating the site or something. 
28th March 2002, 05:07 AM  #7 
diyAudio Member
Join Date: Dec 2001
Location: Steak and Kidney

He moved! Try http://www.quadesl.com/ (under the DAC section)

28th March 2002, 05:16 AM  #8  
diyAudio Moderator Emeritus
Join Date: Jan 2002
Location: Michigan

Howard W. Sams has it all!
I don't know the availability because I have a 1980 edition, but there is a Howard Sams book on transformers.
"Practical Transformer Design Handbook" by Eric Lowdon First Edition, First Printing  1980 Howard W. Sams & Co., Inc. It's a 240pg soft cover book, and is 81/2" X 11". It starts at "Elementary Electromagnetics" (Chapter 2) and covers through properties, construction, design, applications, examples, and practical issues like buying new or used, and Tests and Measurements (Chapter 16). One drawback is that it only has a few pages on toroids. One quote from the book is: Quote:
Good Luck Rodd Yamashita 

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