Re: [PSUBS-MAILIST] motor seals

["Paul Suds" <paul_suds@hotmail.com>]

Let me wade in on the magnetic coupling concept. I researched this for a 
long time before abandoning it. The reason I never pursued it is because of 
the lack commercial viability. The loss of efficiency is not that bad 
depending on design. There are two basic designs, one uses rare earth 
magnets on both sides. The other uses rare earth magnets on the motor or 
drive side and an induction source on the other, otherwise known as a 
hysteresis disk. This can be a steel can type of arrangement with copper 
disks or rings in the steel or iron can. The reason for the can is that it 
increases surface area without increasing the diameter of say, two plates. 
This is beneficial because the larger the diameter, the stronger the solid 
seal must be. Since you want the greatest flux density that you can get, you 
want the seal to be thin. The best design for this is a can and insert 
configuration, especially where external pressure is involved. Methyl 
acrylate (acrylic) would work good because of it's low elongation 
properties, but I would use a thermoset instead.
Remember, electromotive force, EMF (voltage) is comparable to magnetomotive 
force, MMF; Resistance is an equivalent parameter to Reluctance, and Current 
is equivalent to magnetic Flux. Magnetic "circuits" can be treated similarly 
to electric circuits for design purposes.
I've always been amazed that today's rare earth magnets Nd-Fe-B 
(Neodymium-Iron-Boron)can be up to 60 times stronger than a AlNiCo magnet, 
that we are all used to.
I've got a good book on calculus based magnetic principles, but I have found 
that experimenting is the best way to go.
if you need me to look up any calcs, let me know. Good luck,
Suds
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