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Registered Member #10
Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424
Was reorganising my web site and looking at magnetic levitation stuff so thought I'd try a few things.
Here is an air cored coil out of a defibrillator output circuit. Don't know number of turns but the inductance is 10mH (I think). It is drawing 6.5 A at 100V AC to get the lift of about 1/2 inch off a 1/4 inch copper plate. It is tethered like a conventional lifter.
I did try levitating a MOT with the E section opened and facing down but really needed a better winding. Hence I tried a non cored coil.
Registered Member #10
Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424
uzzors wrote ...
Nice. Have you tried lifting anything with it?
Here is the 284g coil lifting a 217g solder reel (total 500g). Current was a bit higher and distance off the base was 1/4 inch compared with 1/2 inch before. There is a world of difference with an electrostatic lifter where the lift is (mostly) independent of the proximity of the ground and is far smaller.
Registered Member #64
Joined: Thu Feb 09 2006, 06:25AM
Location: Southampton, UK
Posts: 68
very nice Peter, I think i got a bit of an understanding why this works... something to do with eddy currents in the base copper plate? what i'm trying to get my head around is the AC, DC thru a coil would make the coil an electromagnet and it would repell off a magnet giving lfit, but AC? Does the base plate have a repelling magnetic force because of eddy currents induced by the coil? if so would a ring shaped base plate (same shape as the coil) give a better lift for less power?
Registered Member #64
Joined: Thu Feb 09 2006, 06:25AM
Location: Southampton, UK
Posts: 68
could be diamagnetism, copper is slightly diamagnetic i've got a kilo of bismuth shot around somewhere (bismuth is 15x more diamagnetic than copper)... something to try tomorrow :)
Registered Member #70
Joined: Thu Feb 09 2006, 08:19AM
Location:
Posts: 43
It not diamagnetism as the most diamagnetic material on Earth (pyrolytic graphite) can only float mere millimeters above grade N50 neodymium super magnets and barely lifts its own weight.
It is eddy current repulsion from AC being feed to the coil.
Care to give more infomation on this TDU? frequency? power? whoops, I read though the posts quickly and missed that part ^^
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