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Coil Winding Orientation and Pattern...

  1. May 11, 2016 #1
    OK, so imagine you have a wire coiling over itself, in a near concentric spiral. When you get to the outer most edge, such as 10 or 100 wrappings depending on thickness, you then bend the wire so it's one diameter of the wire over and then start spiraling inward, till you get to the smallest diameter, then bend again, spiral the coil back to the largest diameter, and repeat this sequence.

    While the wrapping style of this coil configuration is very different from the standard spool, of slinky one wrap along a parallel line slowly working left, then stopping, followed by wrapping it slowly right, then reversing, until the total wrappings are complete,

    I really want to know if the magnetic field properties are different between these two? Do the magnetic fields bulge out more in method one, or do they have different properties than method 2? Method 2 is the standard method.

    Essentially, while the amount of magnetic wire is the same, the electricity is pulsing in and out, and gradually working left to right,

    while in method 2, the electricity appears to pulse left to right, while gradually working from in to out.

    So does coil configuration really matter? After all, the left hand rule says the direction of the magnetic effect, such as for a solenoid, is going to stay the same if both are wrapped in the same direction.
     
  2. jcsd
  3. May 11, 2016 #2

    berkeman

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    Staff: Mentor

    You have the same number of Amp-Turns, so you should get the same magenetizing inductance Lm, IMO. But your parasitics will be quite different, with a higher leakage inductance Lk and parasitic capacitance Cww. Can you say why Lk and Cww will go up with this winding technique? :smile:
     
  4. May 11, 2016 #3
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    here's 3 crude Images to explain what I mean by method 1. Each coil connects to the second coil, but they swap connecting points from inside to outside to inside repeatedly from one disk to the next.
     
  5. May 11, 2016 #4
    I do not understand what Lk and Cww means so i have no idea if they will go up. I was wondering though if there were any pros to match whatever cons the alternative coiling method might have, and how the magnetic field lines would look different. :)
     
  6. May 11, 2016 #5

    berkeman

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    Staff: Mentor

    I don't see any pros offhand, and the higher Lk and Cww are definitely bad things.

    The reason they go up is that each winding is adjacent to a winding that is "far away" from its neighbors, so the voltage difference seen between side-to-side windings is larger, which increases the effective winding-to-winding capacitance, Cww. And the flux linkage is worse because of the same reason, so Lk goes up.
     
  7. May 11, 2016 #6

    Baluncore

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    Science Advisor

    If you are winding an electromagnet that will be operated on DC, then each turn of the winding will carry the same current. It is the distribution of all those single turns in space and about the core that determines the magnetic field. For DC, winding configuration does not change the magnetic field.

    There is a voltage drop across each turn and each layer due to the resistance of the wire. The wire is insulated. Voltage has no effect on the magnetic field. But the order of winding the coil determines which turns are adjacent to which other turns. That has insulation implications. It is normal to wind a coil so as to keep difference voltages between near windings to a minimum as that will reduce the volume of insulation required. More insulation would reduce the space for copper so the resistive losses would increase, or the outer size of the winding might increase, resulting in changes to the magnetic field.

    The implications of coil winding configuration become more important for AC excitation. As the frequency rises there are many effects that start to come into play. When the total length of wire in the winding approaches one tenth of a wavelength the coil may need to be treated more like a transmission line than an inductor.
     
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