Transformer winding technique - 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 6th December 2008, 05:46 PM   #1
simingx is offline simingx  Singapore
diyAudio Member
 
Join Date: Mar 2005
Location: 0117.5319' N, 10348.2319' E
Default Transformer winding technique

Hi,
From what I've read here (and elsewhere), for minimum leakage inductance I should wind the power transformer of a SMPS like this:

(1/2 primary)(secondary)(1/2 primary).
That is, if I need 20 turns on the primary and 10 turns on the secondary, it'll be:
(10 primary)(10 secondary)(10 primary).
However, in Marty Brown's "Power Supply Cookbook", he shows the winding as (primary)(secondary)(primary). Thus, following my above example, the winding would be:
(20 primary)(10 secondary)(20 primary)
with the primaries connected in parallel. I've attached the figure from the book (He uses a 38 turn primary).

Is this right?
Attached Images
File Type: jpg page.jpg (36.6 KB, 746 views)
  Reply With Quote
Old 8th December 2008, 02:08 PM   #2
winny is offline winny  Sweden
diyAudio Member
 
Join Date: Sep 2007
Yes.

What you are trying to do is interleave the windings (n=2). The leakage inductance does is in theory reduced by a factor n^2 where n is the number of "interleavings" in your sandwich. (Bad english)

If you want minimum leakage inductance, you could do primary-secondary-primary-secondary-primary (n=3) in order to get even lower inductance. The capacitance and losses due to proximity do go up however with each level of interleaving.
  Reply With Quote
Old 8th December 2008, 10:34 PM   #3
dtproff is offline dtproff  United States
diyAudio Member
 
Join Date: Oct 2008
Location: Plano, TX, USA
The ideal construction is single layer primary, single layer secondary, single layer primary, etc...

The goal is for the primary/secondary coupling to see the same voltage potential all the way across the transformer windings.

The split winding technique does work and I do indeed use it when the other winding method can't work. This is usually because my winding window is not wide enough l(i.e. when you use RM or PQ cores).

I hope that helps.

Tony
  Reply With Quote
Old 10th December 2008, 12:10 PM   #4
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
the more layers you use the more insulation required and the less room for copper. Compromise.
__________________
regards Andrew T.
  Reply With Quote
Old 10th December 2008, 07:40 PM   #5
diyAudio Member
 
megajocke's Avatar
 
Join Date: Jan 2003
Even though interleaving decreases the space available for copper losses will actually go down if wires are thicker than about half a skin depth! You need to look out for proximity effect losses when you are starting to approach the skin depth of the conductor. For SMSP transformers of more than maybe a few tens of watts this is almost always.

If you have a single layer primary and secondary and they both are thicker than a skin depth then current will effectively only flow on *one side* of the windings. The commonly shown picture of current flowing in a shell that gets thinner for higher frequencies is only true for a coaxial cable or similar arrangement. In a SMPS transformer it gets much worse the more layers per section.

Interleaving "splits up the middle section".

Here is a very good explanation:
http://focus.ti.com/lit/ml/slup197/slup197.pdf

The math might be a bit advanced but the pictures are pretty clear

If the frequency is high enough (>50kHz or so I guess) then that transformer in your picture will have lower loss if thinner wire is used for the primary winding so that the wire fits in one layer per portion! The foil must be pretty thin too.
  Reply With Quote
Old 11th December 2008, 02:06 AM   #6
diyAudio Member
 
Join Date: May 2007
What is the switching freq? What is the thickness of foil?
How will you wind the 2 strands of primary- Are they in parallel in 2 layers or bifilar?
  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
DIY Transformer Winding GlidingDutchman Parts 14 13th February 2012 06:00 AM
Transformer Winding microsim444 Power Supplies 4 3rd February 2009 09:58 PM
winding technique of current sense transformers zilog Power Supplies 7 19th February 2007 05:32 PM
high freq ETD core transformer winding technique sss Power Supplies 9 18th January 2007 01:35 PM
Winding a Transformer punchpeanut Solid State 8 1st December 2003 02:48 PM


New To Site? Need Help?

All times are GMT. The time now is 08:20 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