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Toroidal Core Winding Help

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bwsparxz

Tue May 08 2012, 11:22PM

Registered Member #1928 Joined: Mon Jan 12 2009, 01:51PM
Location: Reidsville, NC
Posts: 10

When winding a 1 " to 2" ferrite or powdered iron toroid core, Is there a way to get the windinds to lay flat and tight to the core? Been trying with 12, 14, and 16 ga magnet wire. Nothing I tried worked very well. Wire ended up wavy looking and really loose. I realize that its not going to look as good as machine wound. But would like something rather close. Any advise?

Antonio

Tue May 08 2012, 11:25PM

Registered Member #834 Joined: Tue Jun 12 2007, 10:57PM
Location: Brazil
Posts: 644

Fix the wire with adhesive tape as you wind it.

bwsparxz

Tue May 08 2012, 11:41PM

Registered Member #1928 Joined: Mon Jan 12 2009, 01:51PM
Location: Reidsville, NC
Posts: 10

That I did. The thick wire just forms a circle. Do I use soft jaw pliers to flatten against core?

Forty

Wed May 09 2012, 12:00AM

Registered Member #3888 Joined: Sun May 15 2011, 09:50PM
Location: Erie, PA
Posts: 649

If you've got enough room, if you could slightly bend the wire away from the core, it will lay more flat against it after you wind it over.

I haven't had much problems with 16awg (although it is hard on the hands) but I can definitely understand trouble with 12-14awg.

I suppose using pliers could help. Just wrap them in a couple layers of electrical or duct tape so that you don't damage any insulation, and don't use too much force so that you don't break the core (I've broken 1" OD cores with just my hands, so be careful)

Sulaiman

Wed May 09 2012, 03:03AM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3141

Using pliers etc. makes scratching the insulation likely and shorted turns are bad

Putting a lot of mechanical stress on the core can alter its magnetic properties

Other than cosmetic there is no problem with circular instead of square turns

Consider using several thinner wires lightly twisted together instead of one thick wire
- easier to wind and better at high frequencies.

P.S. if you haven't discovered it yet, its easier to start with the middle of the wire and wind two halves rather than starting from one end.

bwsparxz

Wed May 09 2012, 04:54AM

Registered Member #1928 Joined: Mon Jan 12 2009, 01:51PM
Location: Reidsville, NC
Posts: 10

I had not thought of trying that. Was always strarting from the end. Will give it a shot.

Dr. Slack

Thu May 10 2012, 07:30AM

Registered Member #72 Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659

It doesn't actually help with the original question of round or square turns lying on the core, but if you respond to the issue of whether to wind from the end or the middle of the wire, then there may be a tip I can help with.

It sounds like you are making the the turns by poking the wire through from the ends. This is OK for a few turns, but once it gets into double figures, there is a huge problem from simply managing the length of the wire, and repeated scuffing as the same bit gets pulled through the core again and again.

For anything more than a few turns, I wind a toroidal core like a machine does (without the fancy mechanics). That is, estimate how much wire the winding will consume, and add 10% for safety. First the loading stage. I pass one end through the core, and tape it back to itself to make the first turn through the core, about a 1ft diameter circle (or larger or smaller depending on taste, ease of handling, size of core, length of wire, but 300mm is not bad). Now rotate this first turn through hole in the core, picking all of the wire turn by turn. It's a good idea that every (say) 2/3rds of a turn put a bit of tape round the bundle to keep them together. When the machine does this, it's winding them onto a former that's split so it can pass through the hole. Re-reading, it's obvious to me what's going on, but if you've not seen it, it may be hard to visualise. It really needs a video. There may be some on youtube, "how does a toroidal winding machine work?"

At the end of this first stage, all of your wire is now in a loose coil 1ft in diameter, passing through the hole in the toroid.

Now wind your toroid. As you make each turn, feed a bit more wire onto the toroid from the coil, and rotate the coil, taking off each piece of tape as you need to free its turn. The beauty of this method is that passing the wire through the toroid hole is done as a seperate step to making neat turns. It largely avoids scuffing, and it manages the length of wire.

Taping a bit of chamois leather to the inside of pliers jaws gives you a tool that can boss wire around without damaging it.

klugesmith

Thu May 10 2012, 08:47PM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

Dr. Slack wrote ...
... It really needs a video. There may be some on youtube, ...

Yup. Here's one I often turn to.

Looks like youtube also has some home-made toroid winding machines.

And all manner of other winding processes.
This 4700-HP motor stator has to be flipped over at the halfway point (just after 2m30s).

bwsparxz

Fri May 11 2012, 01:44AM

Registered Member #1928 Joined: Mon Jan 12 2009, 01:51PM
Location: Reidsville, NC
Posts: 10

Thanks for all the replies. Each built towards an idea that I'm going to try out this weekend.

Newton Brawn

Tue May 15 2012, 01:41AM

Registered Member #3343 Joined: Thu Oct 21 2010, 04:06PM
Location: Toronto
Posts: 311

Hi bwsparxz !

You may wind 2 or 3 layers of masking tape in the pliers jaws, so you can handle the thick wire without damage insulation.

Avoid use # 16 and thicker wire, it is almost impossibe to wind such wire in 25- 50mm toroids. Use 2 or 3 or 4 wires in parallel.

If you need a coil with #14 AWG wire you may use 2 wires # 17 AWG, or 4 wires #20AWG in parallel. The rule is when you go up 3 gauges in the AWG scale you get half of the cross section. (and going 10 gauges up you get 1/10 of cross section)

Winding #12 AWG, you may use two #15 AWG in parallel, or 4 wires #18 in parallel.

In this way you avoid mechanical stress in the insulation and magnetic core.

Regards

EDIT >>> The AWG scale cross section increments are (10)^(1/10).

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