I have built an electromagnet in a shape that can be described as a gapped toroid. The core is 1008 LCS of .070" diameter. The diameter of the ring is 1.5" The gap is .200" The coil was wound by hand so I am unsure of the number of turns however it is 36 gage at 10 ohms, one layer. I believe there is approximately 800-1000 turns. I apply a voltage of 5V. The poles face each other and are ground flat. I have noticed a problem where the South pole is orders of magnitude stronger than the north pole. If the current is reversed through the coil, the opposite pole (now the south pole)is now much stronger. I expected there to be fringing involved with the coil but assumed the poles would still be relatively close in magnetic strength. My assumption is the magnetic flux is traveling through the coil, exiting the south pole but not making a connection to the opposite pole. Is the gap too large? Should the pole faces have a different shape? What other cause and solutions are there to this problem? Thanks for any help!
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Flux leakage
- Thread starter Mech133
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I have a gauss meter that I can get rudimentary readings from that confirm the lopsided strength, however the probe is fairly large so it is difficult to zero in on the pole without getting interference from the other. Basically I noticed the significantly stronger pole by hanging a magnetic non-polarized rod above each pole. Even when the rod is almost directly above the North pole, it will still be attracted to the south pole. touching the rod to the south there is a noticeable magnetic effect, touching it to the north pole and there is hardly any attraction at all. This is reversed when the current changes.
Gauss probes will display a difference depending on which side is up. The hall element is not perfectly centered.
Perhaps the bench or surroundings are influencing the field shape.
Or perhaps the ends are not cut quite the same. The core is pretty small in diameter. It might be difficult to see if the ends are the same. That would certainly change the result with a larger core.
Mike
Perhaps the bench or surroundings are influencing the field shape.
Or perhaps the ends are not cut quite the same. The core is pretty small in diameter. It might be difficult to see if the ends are the same. That would certainly change the result with a larger core.
Mike
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Thanks for the insight, the coil does have some non-symmetries as I shaped it by hand and ground the ends on a grind wheel. I could chalk it up to those facts but then I assumed that one side would always be weaker, not reverse with the polarity. At any rate I guess I was looking to see if there was some fundamental or theoretical reason for this phenomena, I am at least happy to hear that my assumptions for how it SHOULD be working seem reasonable.
Compositepro
Chemical
If your problem switches poles when you reverse polarity then the problem is not in your magnet but with what you are using to measure the field strength. Obviously your magnet geometry does not change with polarity.
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