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Induction from coiled up leads???

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  • kjbllc
    replied
    ac current and maybe pulsing dc will make a magnet with an aluminum core, the cheap relays use this, also the meter on your house has an aluminum wheel not steel that turns and makes the dials turn.

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  • Bodybagger
    replied
    A reel doesn't have a lot of mass relatively speaking. I mean most of the space inside the coil is still air. It does increase it, though. Now if you wrap it around something solid, like steel wheel weights or 6" round bar stock, now you're talking!

    If you think there's a good deal of inductance there, find a Ham radio guy with a MFJ-259 and analyze the inductance. Try it again wrapped around a steel wheel weight.

    The reason I say it's a waste of time is because it won't make enough inductance to affect your welds. It takes bigger, purpose-built inductors for that.
    __________

    I came back to add these links...

    http://sci-toys.com/scitoys/scitoys/...lculating.html

    http://info.ee.surrey.ac.uk/Workshop/advice/coils/mu/

    The first one describes in simple terms how the amount of air vs. the amount of iron inside of a core affects the permeability of the core, and thus the inductance.

    The second one discusses the non-linear nature of permeability and how the core is affected by "saturation." (as in magnetic flux density saturation)

    It's complicated and I felt like I didn't explain well enough why an aluminum reel doesn't "look" much different than a steel reel from the perspective of the magnetic field. I hope this helps a little.
    Last edited by Bodybagger; 02-01-2009, 04:06 PM.

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  • acustomfabricatorcom
    replied
    Inductance

    Been a long time but what was all that in science class about winding copper wire around an "iron" core? Are you absolutely positive that there isn't enough difference between a steel reel and an aluminum one to bother changing it? Like I said when I started this thread. A pipe welder with about 30 years was able to get enough root reinforcement but it didn't want to tie in. I just wonder if it was because my leads are wound up on a steel spool versus his on aluminum. I would ask him but I have taken up so much of his time and he never reply's to my e-mails.

    I just found some interesting stuff as it relates to electromagnets that might be relevant. It would seem to me that I\we would want to do all I\we can to make a poor electromagnet. The paragraph below was taken from this link http://education.jlab.org/qa/electromagnet.html

    Hints to Make Your Electromagnet Stronger

    The more turns of wire your magnet has, the better. Keep in mind that the further the wire is from the core, the less effective it will be.

    The more current that passes through the wire, the better. Caution! Too much current can be dangerous! As electricity passes through a wire, some energy is lost as heat. The more current that flows through a wire, the more heat is generated. If you double the current passing through a wire, the heat generated will increase 4 times! If you triple the current passing through a wire, the heat generated will increase 9 times! Things can quickly become too hot to handle.

    Try experimenting with different cores. A thicker core might make a more powerful magnet. Just make certain that the material you choose can be magnetized. You can test your core with a permanent magnet. If a permanent magnet is not attracted to your core, it will not make a good electromagnet. An aluminum bar, for example, is not a good choice for your magnet's core.
    Last edited by acustomfabricatorcom; 01-31-2009, 11:59 PM. Reason: forgot some stuff

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  • Bodybagger
    replied
    It would not be worth the time because almost all of the inductance is caused by the wound up leads. The reel is negligible.

    I wouldn't bother with it.

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  • acustomfabricatorcom
    replied
    Inductance

    Do you think it would be worth the time to convert from a steel reel to an aluminum one?

    Also, I currently keep my leads tied to each other for their full length of about 125' and have to disconnect my leads from the reel if I want to change length. I was thinking about making two aluminum reels facing each other and have them insulated from each other with pvc pipe (about 5" diameter) to wind the leads on and have the current run through the bearings on each one. This way the leads are always hot. Any problems with this idea?

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  • Miller John
    replied
    Yes, coiled up cables will affect the welding arc. It depends what type of metal and quantity they are coiled around, how tight the coils are and how many turns there are. These factors determine the amount of inductance and will affect the responsiveness of the arc. While adding inductance may be good or bad for arc performance depending on what you are doing, it will hurt arc starts.
    There is a lot of good feedback from the responses that pretty much say the same thing. Playing around with it is the best way to see what it does for you.

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  • Bodybagger
    replied
    The reel is negligible.

    125' of cable wrapped in a 12" loop 6" wide (would be about 40 turns) is going to add 500 microhenries of inductance, or .0005H.

    I doubt that will cause you problems. More inductace results in a more stable current. However, if this is located next to your welder, you could be putting a large magnetic field into it that will mess up the control circuitry.

    If you wind it one way for half its length, then wind it the other way, the opposite magnetic fields will cancel each other out. Well, almost anyway, since I doubt they'd be EXACTLY equal and opposite.

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  • Bweldtec
    replied
    electrical current, regardless of what it passes through, will create magnetic field when running through coils... which will impede itself coils = bad hehe

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  • cruizer
    replied
    Well, no, even if they were invisible, your still going to have an cable indused magnetism in the air gap.

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  • FusionKing
    replied
    Originally posted by davedarragh View Post
    Fusion: You talkin' the cables or the reels?

    Dave

    The reels

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  • davedarragh
    replied
    "Pragmatic Magnet"

    Originally posted by FusionKing View Post
    I wonder if there is a material you could make them from that would eliminate it entirely?
    Fusion: You talkin' the cables or the reels?

    Dave

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  • cruizer
    replied
    Well, you could make the arc cables out of premium copper that was electrically treated with irridium, mind you that would probably cost about $10grand for a couple hundred feet.

    So no, not too economic

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  • FusionKing
    replied
    I wonder if there is a material you could make them from that would eliminate it entirely?

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  • cruizer
    replied
    Even with the welding wrap coiled on the ground there is a magnetic air gap, though it's tough to get a tight coil when you plunk your cables on the ground but it's still there to some degree.

    Say if you have a reels with a steel core, like the home mades, or even Shel-ryn, or Swishco you have a large magnetic inductance happening which effects circuit board operated machines depending on where your reels are located in position with those internal boards. Even in non circuit board machines, that magnetic inductance can cause arc blow.

    True Aluminum reels with a Aluminum not steel core, act like a air gap where there is a diffused magnetic inductance, but not enough to effect much.
    Last edited by cruizer; 01-15-2009, 12:30 PM.

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  • Vicegrip
    replied
    ? DC makes good electromagnets. You don't need to be inducing elec energy into other things or shifting the direction or amps to make a strong magnetic field with a large coil of wire. The magnetic field impinges on itself.

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