Calculating magnetic resistance on moving flywheel???
Calculating magnetic resistance on moving flywheel???
(OP)
Given a spinning Iron ring of a certain mass and dimensions (say about 1.5 inch by 8 inch ID and 9 inch OD, if I move magnets closer to this ring they will increasingly resist the ring from spinning....more torque will be required to keep the ring spinning at the same speed (think of magnetinc resistance in an exercise machine).
I'm trying to estimate how large and how powerful my magnets must be and how close they should be from the spinning ring. I took advanced E & M, but really have very little experinece in this area (like none!).
Can someone point me in the right direction? I'm looking for equations, weblinks, etc.
Thanks a whole lot - Barry
I'm trying to estimate how large and how powerful my magnets must be and how close they should be from the spinning ring. I took advanced E & M, but really have very little experinece in this area (like none!).
Can someone point me in the right direction? I'm looking for equations, weblinks, etc.
Thanks a whole lot - Barry





RE: Calculating magnetic resistance on moving flywheel???
Get a big magnet and a steel bar and measure the drag (details of a test fixture left to you). The drag will be dependent on both the magnetic field strength and the velocity. The field strength can be varied by changing the magnetic field gap.
RE: Calculating magnetic resistance on moving flywheel???
<nbucska@pcperipherals DOT com> subj: eng-tips
read FAQ240-1032
RE: Calculating magnetic resistance on moving flywheel???
You are correct; the eddy current drag improves with the conductivity of the disk. Copper is better yet.
RE: Calculating magnetic resistance on moving flywheel???
Thanks.
RE: Calculating magnetic resistance on moving flywheel???
Barry: Voltage is induced -- mass of wheel acts as short circuit so it acts as a shorted dynamo ( "Eddy current" )
<nbucska@pcperipherals DOT com> subj: eng-tips
read FAQ240-1032
RE: Calculating magnetic resistance on moving flywheel???
RE: Calculating magnetic resistance on moving flywheel???
This brings up some interesting design considerations. We would obviously like to keep costs low, but we also want to keep the size of the wheel small. How would steel work? I'm not an electrical guy so forgive me if the answer is obvious. I've never heard of steel wires so I'm thinking maybe steel isn't a good choice.
Also, I need to document some of this stuff for a preliminary report. Anyone have a good link?
RE: Calculating magnetic resistance on moving flywheel???
<nbucska@pcperipherals DOT com> subj: eng-tips
read FAQ240-1032
RE: Calculating magnetic resistance on moving flywheel???
A steel or cast iron rotor will provide a much more effective magnetic path, and more available magnetic flux, but have greater electrical resistance per unit volume.
In practice a thin aluminium disc is typically used in very, small low power light duty applications, and thicker iron/steel disc in large high power applications where considerable heat may be generated and the forces are large.
Both work, it is just a case of deciding which is most suitable for different situations.
RE: Calculating magnetic resistance on moving flywheel???
TTFN
RE: Calculating magnetic resistance on moving flywheel???
RE: Calculating magnetic resistance on moving flywheel???
-Barry
RE: Calculating magnetic resistance on moving flywheel???
My work fax number is (302)831-8525. If you can fax me that info that woould be great. Send it Attn: Barry Pollock
Thanks again - Barry