Coil Winding: How to Layer Coil Turns

[StephenD420]

Hello everyone

I have a quick question on how to wind overlapping layers of magnet wire around a coil form. How do you layer coil turns for a coil? Do you just start at the top of the coil form and then coil over the top of the previous coil in the same direction and then just twist the two endings together for the leads at the top and bottom of the coil?

Thanks.
Stephen

 

[Danger]

Hi, Stephen.
Your question confuses me. By mentioning a "coil form", you imply that this is some sort of established technique for which there should be instructions, or at least parameters.
I've used everything from pencils to toilet paper cores as "coil forms". (Okay, not everything; that would just be sick... Enticing concept, though... hmmm...)
I think of it as one would an open-face fishing reel, where the line is guided from side to side as it returns. While I don't know whether or not it is acceptable to the real scientists here, I like to lay down a coat of white glue (LePage's here; probably Elmer's in the US) over each layer of wire (you don't need to let it dry between layers.) That's just a precaution against slippage after the core is removed.
Anyhow, the winding is just to and fro until you build up enough layers. Only after the last winding do you remove a section of enamel from the wire to connect electricity to it. While it's handy to have the beginning and end wires in the same place, it certainly isn't mandatory.

 

[StephenD420]

A coil form is a core, for my coils either an iron rod or steel rod as I do not know where to get or really have a lot of money to spend to get some sort of ferrite core. If you guys know of a place or a really good ferrite core that I could use, as I would really like to get as close to 1 Tesla in my coils for the stator,please let me know.

As for winding, wind one layer with two leads on each end and then cut the wire and start again at the top and wind the same direction as the first layer and then cut the wire for the ending lead and then twist the two layer's ending lead of wire together? Or do you just start winding back up the core from the first layer of windings, so you do not cut the wire, it is just winding down and then back up? Adding layers of windings it does increase the magnetic field produced by the coil, right?

Thanks so much for your help and advise. I really appreciate it.
Stephen

 

[Trisha07]

Thanks, i had always been curious about this as well!

 

[Danger]

Well, Stephen, it seems to me that you need a particular shape of coil; otherwise, your use of steel rods would be just fine. Your mention of "core" indicates that the piece is to remain in place while the coil is in use. I was thinking of something that you would just build your core around and then remove.
As for finding cores... my most serious recommendation is to snaggle all of the transformers, generators, motors, etc. that you can lay your mitts on. They all have ferrite cores. If none of them are the right shape for you, maybe you can grind/pound/drill/machine/weld one of them to your liking.
Your attempt at describing your winding technique has given me a massive headache. All that I ever use is single-strand enameled bell wire. Just wind it up, then connect one end to positive and one to negative.

 

[superflex]

The magnetic field is proportional to the current in the coil and the number of turns of the coil. More turns means a greater magnetic field. It would probably be better to make all the layers of the coil from one continuous length of wire.

Wikipedia article for Solenoid

 

[sophiecentaur]

I have a feeling that you may be unduly worried. The only really essential thing about winding your coil is that all the turns should be either clockwise or counterclockwise (sorry if this is blindingly obvious but . . . ). Also, any core should go through all the turns of the coil. Sometimes the windings can be arranged to minimise the voltage between adjacent turns (where high voltages and tight packing are necessary). In a Tesla transformer, for instance, the windings need to be just one layer.

 

[StephenD420]

So once I finish winding the magnet around the core once say 100 turns then I just start coiling back up the core, going over the first windings, just backward? Wouldn't that cancel out the magnetic field?

Thanks.
Stephen

 

[sophiecentaur]

Clockwise is clockwise, wherever the turn happens to be on the core.

 

[StephenD420]

ok so I got a small rod of steel from Homedepot, got 24 magnet wire from RadioShack and round 100 turns on the rod of steel, super glueing the first and last turn as tape is so messy. But when I hooked up the top and bottom leads to a 3amp 12V DC power supply I bought from RadioShack, the steel did not become an electromagnet. It did not appear to be magnetic at all. What am I doing wrong??

Thanks.

Stephen

 

[Delta Kilo]

ok so I got a small rod of steel from Homedepot, got 24 magnet wire from RadioShack and round 100 turns on the rod of steel, super glueing the first and last turn as tape is so messy. But when I hooked up the top and bottom leads to a 3amp 12V DC power supply I bought from RadioShack, the steel did not become an electromagnet. It did not appear to be magnetic at all. What am I doing wrong??

According to http://en.wikipedia.org/wiki/American_wire_gauge your wire has resistance 84mOhm/m. I guess you used a few (less than 10) meters of it. So your coil resistance is less than an Ohm. Applying 12VDC to it would produce more than 12Amps. My guess is when you connected it to your power supply, short-circuit protection kicked in (assuming it had one, otherwise it just packed up). Even if you do manage to get enough amps (like from a car battery), the power dissipated in the coil will be >150W, expect burning smell, smoke and sparks and bits of molten copper flying around.

My suggestion, try it with a battery first, a single AA- or C-cell will do. The battery will not last very long and things will get hot, but it should produce some effect. What are you trying to accomplish exactly?

PS: Did you scratch the insulation off the ends?

 

[StephenD420]

Thanks I will try that in the morning.

I am trying to make a three phase stator ring with six coils that produce a rotating magnetic field. However, because I am in the US my house does not get three phase power so I got a variable frequency drive that would simulate three phase ac from single phase ac, but it only gives out 4 amps. So do you guys know how I could use three single phase ac lines and capacitors to change the phase so the second ac line is 120 degrees and the third ac line is 240 degrees out of phase with the first ac line? I know if I used two ac single phase lines and put a capacitor in series with one of the legs then that line would be 90 degrees out of phase with the first ac line. Would this be enough to create a rotating magnetic field around the inside of the stator, or would it just pulsate, as I really want to research rotating magnetic fields. I have looked in many physics and engineering books and I have read that three phase is the best ac source for a rotating magnetic field. So how do I get my single phase ac line to a three phase that would give me a strong rotating magnetic field?

Pictures to follow.
Thanks.
Stephen

 

[Danger]

I have no idea as to your circumstance, so this might be inappropriate, but what I suggest is that you talk to your friendly neighbourhood mechanic or machine shop. Ask if they will let you set up your equipment in an area that already has real 3-phase mains. (Or if you're ridiculously wealthy, your local power company will install 3-phase in your home.)

 

[sophiecentaur]

I have no idea as to your circumstance, so this might be inappropriate, but what I suggest is that you talk to your friendly neighbourhood mechanic or machine shop. Ask if they will let you set up your equipment in an area that already has real 3-phase mains. (Or if you're ridiculously wealthy, your local power company will install 3-phase in your home.)

You are joking, of course. Would you seriously suggest that anyone using this forum for such info should hook up to the mains 'just like that'? Theory is one thing but power engineering on the strength of some chatty posts? Risk assessment is the most important thing here.

 

[Danger]

You are joking, of course. Would you seriously suggest that anyone using this forum for such info should hook up to the mains 'just like that'? Theory is one thing but power engineering on the strength of some chatty posts? Risk assessment is the most important thing here.

As your entire post demonstrates, things are vetted here. I would certainly trust information on PF over something in Wiki or on U-Tube, because experts monitor the posts and correct faulty information. Note that I prefaced my suggestion by pointing out that it might not be appropriate because I am unaware of OP's situation. S/he seems to know a lot more about electricity in general than I do, but I used to build stuff all of the time at the sign shop where I worked and never had a problem. We were running 3-phase, and it cost us a small fortune to have it installed. I caught a couple of tingles from a malfunctioning power strip once, but was otherwise unscathed.

 

[sophiecentaur]

How "friendly" would a local Machine Shop have to be to let you in off the street and make a 3 Phase connection to their supply? It needs more than a 13A mains plug - probably a hard wired connection via a 3Phase circuit breaker. Then what about the transformer? Or is all this going to be operating directly at mains volts? Yikes.

IMHO, this is what PF would refer to as 'potentially dangerous' so it shouldn't be encouraged and why wait for a moderator to point it out?

With a moniker like Danger, you may have nine lives but H&S don't expect most people to be that 'lucky' unless they are seriously well qualified.

 

[Delta Kilo]

Danger, can you just imagine for a second what is going to happen when someone like Stephen plugs his handcrafted coil contraption into 3 phase mains AC? :shock:

Stephen, please, whatever you do, DO NOT MESS WITH MAINS POWER. Stick to small batteries and isolated short-circuit protected power supplys.

 

[StephenD420]

I am a student at GA Tech so I do know how to handle lab equipment and do my research safely. Unfortunately, Tech doesn't let you do your own research without a professor helping.

 

[sophiecentaur]

Of course they don't. Their arses are on the line if you kill yourself!

 

[Delta Kilo]

Well, you do not experiment with mains power, period. You *design* stuff that you plug in. This means you have a pretty good idea of what impedances, voltages, currents, power dissipation to expect *before* you plug it in otherwise bad things will happen. Sorry but the kind of questions you ask here sort of hints that you are not there yet.

For example, you said you have a 3 phase inverter rated at "only" 4 amps but you didn't mention the voltage so that does not really mean anything at all. Say, 3 phase x 4 amps x 110V is quite a lot.

On the other hand, experimenting with low-voltage protected power supplies is OK. Just how much power do you think you need?