Sizing a motor to drag magnets around a steel plate

[vc66]

Hi All-

I don't work with magnetism very often, so I'm not really sure where to begin to work this out.

I have a motor with a shaft that's attached to a circular plate. This circular plate has ~30 magnets screwed into it. This plate will be rotating at a particular speed at a certain parallel distance away from a steel plate.

How would I go about finding what the drag torque would be due to these magnets? I just needing a starting point, if anyone can help.

Thanks in advance.

Victor

V

 

[MagMike]

Do you have any conductive material between the magnets and the steel? If yes, then you are describing an eddy current coupling. If no, then you are descriving a hysteresis coupling.

Either coupling is difficult to design analytically, unless you have an existing design and are just scaling up/down.

I'd suggest looking at the webpages of suppliers of eddy current/hysteresis couplings and see if they have anything in your size range. That'll give you an approximate torque.

Otherwise, finite element analysis is the most accurate way to start. The dynamic interplay between the magnetic field and the steel/conductor is very complex.

Mike

 

[vc66]

It's not really a coupling (although I suppose the same rules would apply).

The parallel steel plate, isn't moving.

V

 

[IRstuff]

No, but your magnets are, so the same principles apply.

TTFN

FAQ731-376