Winding Coils Question

Yes that's the way it is done generally, But depending on requirement one can choose to put an interlayer insulation( paper ,plastic or cloths). And beside that, in closed sided formers one should insulate the starting end adequately with some sleeve, so that it don't get any contact with the various layers of windings.If one fail to do so,there is very high chance of short circuit between starting end and top layer of winding.

http://www.youtube.com/watch?v=hnCa4ZSbo_Y

and any number of such videos are available. As Rakesh says, you need to insulate the first turn (the lead-in wire with which you start) very well, since the full voltage will be available across the first and last turns.

This isn't the same project you were working on in 2009, is it?

Be very careful about the insulation. Don't crack or scratch it or you'll have problems.

I think maybe you should tell us what sort of coil you are trying to wind. Are you looking at a small voltage & current or are we talking a large transformer?

The principles are somewhat the same but the applications can be very different & so the answer will vary accordingly.

I have seen small acutating coils that are randomly wound with the only inter-turn insulation being the enamel coating on the wire. Then take a large power transformer - the method, the accuracy & the insulation are considerably different.

So, tell us a bit about what it will do, what is the wire insulation, the voltages etc and then a logical answer can be provided.

Also, even if it were a very small coil I would not simply twist the ends together, solder or crimp them - you tend to get far less open circuit issues later on.

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

I replied to this same post in another thread that you seem to have started on the same project. Please refer to and respond.

Hi Stephen,

To answer your first question, start at the top and uniformly wrap your #24 AWG magnet wire in one direction (either clockwise of counter clockwise, it just reverses the north/south field polarity) making sure to not nick the insulation on the wire. When you get to the bottom start back up again continuing to wind in the same direction (again trying not to nick the insulation on the wire). When you reach 100 turns, do not twist the start and finish ends together (this shorts the coil windings and prevents any current from passing through the wire needed to create the magnetic field). Use molten solder or a flame and sandpaper to remove the insulation from the insulated magnet wire ends so you can hook them up to your power supply.

Secondly, since the magnetic field strength is related to the ampere-turns (AT) of the coil you have created, measure the resistance of the coil windings. For example 100 turns of #24 AWG copper magnet wire (about .020" dia.) around a 1" dia. rod should be around .7 ohms. Note: if you hooked this up to your 12V, 3A power supply it will overload because the coil wants to draw about 17 amps! Either you will blow the supply's fuse or breaker, or if it has overload protection it will decrease the 12V output to almost 0 to prevent burning up the power supply. Either way, you would not create current in the coils and therefore not magnetize the steel rod. Even if you hook up this coil to a 12V, 20A power supply to get the full potential current (17A) and magnetic field (1700 AT) you will burn up the #24 magnet wire because it is rated to carry only 3.5A!

So using the above example (1" dia. rod), you would want 3A max. at 12V or a coil resistance of about 4 ohms. (the core & coil may still be too hot to handle) Since your #24 wire is about 26 ohms/1000', you need to use about 154' of wire (about 580 turns). This would give you about (3A X 580 turns) 1740 AT. If your core size is other than the 1" dia. example I used, adjust the turns until the total coil resistance is 4 ohms or greater.

Third, if you are looking for .5-1 Tesla, your trial may be in the ball park depending on the diameter and reluctance (magnetic resistance) of the steel rod or simply it's ability to have a magnetic field induced into it. May I also suggest that this experiment be used for educational purposes only. Based on your limited knowledge you should not try to directly apply this to an industrial 3 phase real life application without the strict guidance of a qualified electrician or engineer.