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Registered Member #1512
Joined: Fri May 30 2008, 01:16AM
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Posts: 4
I've never seen a microwave oven transformer, so I am uncertain. However, I do know one thing: an essential component of eddy current levitators (which is what an aluminum or copper levitator is) is the requirement that there be (at least) two currents, and that the two currents be out of phase with each other. For instance, one type of levitator described in Propulsion Without Wheels involves levitating an aluminum sphere. To achieve this, the author recommends two methods. In the first, one coil is placed inside another, and the two are separated by some sort of iron ring or pipe (to concentrate the field). These two coils are then powered by different legs of a 3-phase supply, giving you two coils that are 120 degrees out of phase.
A variation on this (also described in the book) is where you have the same setup, with the difference being that the inner coil is replaced with a piece of very thick, solid (i.e. not split) copper pipe. In this case, current is induced in the copper pipe by virtue of the magnetic field generated by the first coil. So you still have some sort of phase difference between the outer coil (powered by AC) and the inner "coi", a.k.a. the pipe, which is "powered" by eddy currents.
Either one of these setups is used to levitate a small aluminum sphere.
A variation on this involves levitating a piece of aluminum shaped something like a dish or pie pan. This is described in Meiners' Physics Demonstration Experiments book. However, this one requires 3-phase power.
So I don't know about the MOTs- all I know is that there would need to be some sort of phase difference between different windings. Also, from my research, the shape and size of the object to be levitated is fairly critical, depending on your setup. That is, the sphere levitator described above will only levitate spheres of a specific size- it will not levitate discs, sheets, toroids, or whatever else. So I don't know what shape an "MOT levitator" would be best suited for, either.
Registered Member #2529
Joined: Thu Dec 10 2009, 02:43AM
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Posts: 600
FWIW a few months back I built a maglev set up using a combination of permanent magnets for the lift and a spinning aluminium disk giving the electrodynamic levitation for the stability. Air gap was about a centimeter.
I did some measurements of the drag on the aluminium from the magnets and it was only about 50-100 mN, so the overall lift power seems to be about a watt per kilogram, or so, and I could probably get it a lot lower.
Technically it was only pseudo levitation in the actual demo version, because I had to tether it laterally against the electrodynamic drag- my final version works like a train, so it will be pulled along by a propulsion system (probably a linear motor) rather than the tether.
Registered Member #26228
Joined: Tue Jun 25 2013, 12:22PM
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Posts: 1
I know this is an old thread, but I am trying to build a magnetic levitator and I am a self taught electronics hobbyist (noob). Currently I have a working levitator, but it becomes quite unstable if it is disturbed at all. I am hoping to implement the feed forward circuit in the first post, but I am unfamiliar with OPAMPs. How am I supposed to power it? does it require a negative voltage?
Any comments, suggestions, or ideas would be greatly appreciated!
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Magnetic levitation
