Is it okay to make transformer windings out of flat cable? - Page 1
Forum section: electronics / beginners

author: hkBattousai
author_rank: Regular Contributor
timestamp: July 03, 2014, 02:14:05 pm
content: I'm going to design a transformer which has many (10) secondary windings. It will look messy and space-consuming. How about I make the secondary winding with a flat cable? Would it be inefficient? I have never seen a similar design; so I'm asking this to make sure of it.(Note: My transformer core is not the one in this picture. Actually, I haven't selected one yet. It will be much smaller; probably its window height will be the same with the flat cable width.)

author: mariush
author_rank: Super Contributor
timestamp: July 03, 2014, 02:25:20 pm
content: I think the thicker insulation and the spacing between the individual wires will mess up the calculations (number of turns to reach that current and voltage). You also have to be careful about the core temperature, some of those ribbon cable pvc insulation is only rated for 85c which may be exceeded inside the transformer.I wonder why you're not considering using a toroidal core, seems like it would be better for this kind of transformer with so many secondary turns. (aaah just noticed the 20kHz note in the attached picture).

author: hkBattousai
author_rank: Regular Contributor
timestamp: July 03, 2014, 02:29:08 pm
content: Quote from: mariush on July 03, 2014, 02:25:20 pmOf course, the toroidal type core is also a choice. E-core is not my final decision.

author: Richard Crowley
author_rank: Super Contributor
timestamp: July 03, 2014, 02:31:25 pm
content: Quote from: hkBattousai on July 03, 2014, 02:14:05 pmSure. There's nothing magic about the shape of the wire.QuoteHuh? Do you mean 10 layers of turns? 10 turns is trivial. "Many turns" would be 1000 or 10000 turns.QuoteWHY? 10 turns seems trivial. What exactly prevents you from simply hand-winding 10 turns around the bobbin. It can be be done easily. Many of us have done it.QuoteIt would be grossly inefficient because of the thickness of the insulation. Note that proper "magnet" wire has ultra-thin insulation consisting of only a layer of enamel (or equivalent).QuoteIn addition to the gross inefficiency from the insulation, there is the matter of handling all those terminations. If you just put flat windings of the ribbon cable on the bobbin, how to you access the wires at the inside end of your coil?Not to mention that the kind of wire and insulation used to make that ordinary gray ribbon cable will make your transformer very fragile and incapable of handling ANY temperature rise. Most ribbon cable would be a terrible choice for transformer winding because is completely the wrong kind of wire.Particularly for power-transformer application, I think using ribbon cable to wind transformers is a horrible idea and I wouldn't give it a second thought.Now, if you wanted to apply all 10 secondary windings at the same time (or 5 at a time, or even 2 at a time) it is not uncommon to apply the windings in parallel to save time, etc. But if you are only making a one-off DIY project, setting up to do that is more time than its worth.

author: grumpydoc
author_rank: Super Contributor
timestamp: July 03, 2014, 02:40:46 pm
content: QuoteI think he actually means 10 secondarywindings, if you look at the diagram.Doesn't make ribon cable a better idea though.

author: hkBattousai
author_rank: Regular Contributor
timestamp: July 03, 2014, 02:43:26 pm
content: Quote from: Richard Crowley on July 03, 2014, 02:31:25 pmNo, not "10 turns", but "10 windings". I wrote it incorrectly in my message. I corrected it. Sorry.Quote from: Richard Crowley on July 03, 2014, 02:31:25 pmWhat is the reason of the inefficiency when the insulator is too thick? As far as I know, permeability of the core material is the major factor in the calculations. Does this kind of insulators have very high permeability?Quote from: Richard Crowley on July 03, 2014, 02:31:25 pmThank you for your message. I think I will give up this idea.

author: Richard Crowley
author_rank: Super Contributor
timestamp: July 03, 2014, 02:47:41 pm
content: Quote from: hkBattousai on July 03, 2014, 02:43:26 pmNo it is SPACE efficiency. Magnet wire has very thin insualation so we can get maximum number of turns into the space available. Using wire with very thick insulation (like ribbon cable) wastes a huge amount of space. That means that either you can't get all your windings on the transformer, or you have to use a very large transformer to accommodate the thick wire windings.