OT: Eddy current brake

["arnaud_westenberg" <arnaud@xxxxxxxxxx>]

Hi all,

First of all I have to apologize for this off-topic posting, hope you
don't mind.

I'm a ME (so please be gentle:-)) student and for a low budget project
at school I need to build an eddy current brake for use as a
combustion engine dynamometer. The brake would simply consist of a
rotating round alu plate and a stationary electromagnet.

My problem is that I can't find the relevant (analytical) equations to
determine coil properties with respect to the required braking torque.
It comes down to the missing relation between magnetic field strength
and the resulting force in the rotating plate.

All I could find are two course (inaccurate) approximations of the
above relationship. The first is by Smythe and second by Wouterse.
Besides the errors produced by the assumption of degree of saturation
they contain some unknown factors.

My question is, which equations should I use to determine the required
coil properties for a certain braking torque and the feedback control
model? I'd prefer to stay away from numerical methods.

Thanks in advance for any suggestions!!

Regards,

Arnaud