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Attempt at an A-Field Motor

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  • Lester
    Greetings to all.

    Can somebody please help my understanding: What's the difference between the A-field and the regular magnetic field of a (electro) magnet? I am asking for help and at the same time trying to do some experiments. If the A-field is beyond the context of this forum then please let know.

    Thank you.
    Last edited by Lester; 11-11-2012, 08:39 PM.

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  • Lester
    started a topic Attempt at an A-Field Motor

    Attempt at an A-Field Motor

    Greetings to all.

    I wanted to build an A-field motor but didn't want to end up frustrated again so rather than build the motor and hope for the best, I just wound a rectangular, elongated coil. I intend to gain more understanding before I actually build the motor.

    This is the coil I made: Quadrifilar, AWG#32, wound on a wooden core (no iron insert) approximately 1" x 2" with the windings spanning a length of 1.5". This took 7 layers of windings to make about 300 turns total.

    I then took this coil and hooked it up to the circuit shown below. I wanted to see how a coil behaves with fast DC pulses. The coil is drawn as a transformer and P1 is actually 3 wires of the quadrifilar coil. S1 is the 4th winding. I adjusted the pot (formed by R2 & R3 in the diagram) until I got it to oscillate and here are my observations.
    ================================================== ============================
    9v supply, current draw is ~200mA once it starts to oscillate, kept on adjusting the pot then the neon bulb (across C-E, not shown) lights up at ~400mA.

    I can adjust the pot some more and the current will increase proportionately, up to some point then it stops oscillating.

    Adjusting the pot also lowers the freq of oscillation. Freq is higher when the current is ~200mA, then goes down to ~1.6kHz at 800mA. (Yes it makes a faint sound and I can hear it)

    I placed a ferrite magnet at one end of the coil (outside the coil and not facing the air core) and it seems that nothing is happening with the magnet (weak repulsion) until I adjust the pot and the current goes beyond 1A, at which point the magnet is thrown off the coil. I repeated this several times ending up with the same result each time.

    With the oscillator driving the coil I can now "feel" around the coil and try to imagine what the magnetic field looks like. I held a magnet between my fingers and made mental notes of the relative field strengths at different locations on the coil. After much feeling around I finally came to the conclusion that the magnetic field in this coil (being driven with pulses) "looks" very similar to the field of a regular magnet. N pole on one end and S pole on the other, with a null right in the middle (is this the Bloch wall?)

    I failed to see any evidence of the A-field "curl" being any different from the regular magnetic fields of an electro-magnet.

    Am I missing something here or is the A-field just another word to call the magnetic field of a magnet? I can still make a motor out of this but that is not the point of this exercise.

    Thanks for your inputs & comments.

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