Seeing this and searching for those TI app notes brought up this PIclist pa= ge ... https://piclist.mit.narkive.com/2psUD8wg/ee-utterly-superb-ti-magnetic-desi= gn-resources which mentions a large number of them and some others besides. -----Original Message----- From: piclist-bounces@mit.edu On Behalf Of Sean B= reheny Sent: 18 March 2019 07:13 To: Microcontroller discussion list - Public. Subject: Re: [EE] transformer winding direction Manu, I am having trouble picturing this transformer. What is the core material a= nd shape? Are all the windings on the same part of the core, or is it an E-= I core or E-E core and some windings are one one "leg" and others on anothe= r "leg"? Given the low turns count, I'm guessing that this is a transformer for a sw= itching power supply. Power transformers in the 10s or 100s of kHz use very= different winding techniques than 50/60Hz transformers. It is very common = to use several layers of turns in parallel for each winding and to interlea= ve them. The reason is not mainly to get better coupling - it is to reduce = losses. Think of it this way - the principal path which the flux takes is t= hrough the core material, but for a transformer, the flux is rather small b= ecause most of the flux from the primary is cancelled by the flux from the = secondary. The remainder is only what is needed to produce the voltage acro= ss the transformer terminals. So, in the space between the primary and seco= ndary windings, there is higher flux than elsewhere - each layer of primary= winding increases the flux and then the next layer of secondary decreases = it. If you put all the primary together and THEN all the secondary, you wou= ld have a high! er flux in the region where the primary layers end and the secondary layer= s begin. This would create larger eddy currents in the copper of those near= ly winding layers (eddy currents in the copper). The TI-Unitrode seminars (available online in PDF form) are a very good gui= de to this, although I found some technical errors in them. The ones most r= elevant to this are the PDFs named: slup126.pdf slup171.pdf slup197.pdf slup200.pdf slup205.pdf You can just search for these filenames and download them directly from TI Sean On Sun, Mar 17, 2019 at 10:44 AM Manu Abraham wrote: > Replying to my own post, > > On second thoughts the interleaved layering would cause an imbalance,=20 > since not all layers are linked withe same amount of flux, which=20 > brings me to: > > L #1 100T Sec > L #2 6T Pri > L #3 100T Sec > L #4 6T Pri > > That said, 2 questions again: > #1. Should the Primary be in Layer #1, or is it better to start with=20 > the Secondary ? > #2. Both the Primary and Secondary should be would in the Clockwise=20 > direction itself ? (I hope so) > > Thanks, > Manu > > > On Sun, Mar 17, 2019 at 3:45 PM Manu Abraham > wrote: > > > > Hi, > > > > Looking at a transformer, primary 12T secondary 200T, step-up > > > > The primary is split in two, the secondary in 3, to reduce leakage > inductance. > > > > ie, > > 1. L1. Secondary 50T > > 2. L2. Primary 6T > > 3. L3. Secondary 50T > > 4. L4. Secondary 50T > > 5. L5. Primary 6T > > 6. L6. Secondary 50T > > > > > > L1 and L3 (secondary) are at opposite sides of the secondary. > > > > In which case isn't the direction of the flux changing ? > > So, when L1 is wound clockwise, shouldn't L3 be wound in a=20 > > counter-clockwise fashion ? > > > > Am I thinking right, or thoughts in the wrong direction ? > > > > Apart from the original questions, any thoughts on a better=20 > > methodology to reduce leakage inductance ? > > > > Any thoughts ? > > > > Thanks, > > Manu > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive=20 > View/change your membership options at=20 > http://mailman.mit.edu/mailman/listinfo/piclist > -- http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/chang= e your membership options at http://mailman.mit.edu/mailman/listinfo/piclis= t --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .