Braking Force from Eddy Currents on a Rotating Disk

[Michael Sofroniou]

Hello! I'm currently working on a project that will utilize the phenomena of eddy currents to apply a braking force to a rotating disk. Some background on this project: My team was tasked to create a physical therapy training device to train patients in wheelchair propulsion at resistances lower than resistances experienced on level ground. We plan on doing this by supporting a wheelchair above the ground so wheels don't touch the ground. Our goal is to use natural magnets on either side of a large rotating metal disk (replacing the original wheels of the chair) and adjusting the distances the magnets are from each disk to vary the applied resistance.

I'm not well versed in magnetic force application and was wondering if there is any general equation that roughly approximates the braking force eddy currents apply on this rotating disk. I imagine a few parameters this problem would depend are as follows:

- magnetic field generated by each magnet
- angular velocity/angular acceleration of the rotating disc
- volume of rotating disc
- mass of rotating disc
- some magnetic property of the metal disc
- distance the magnets are from the rotating disc
- point of application of eddy forces in relation to the center of rotation

I've done some preliminary literature review however some of the studies seemed to be a bit over my head. Any help would be greatly appreciated!

 

[anorlunda]

You should start here https://en.wikipedia.org/wiki/Eddy_current_brake

Then follow the links in the references at the bottom of the article.

I'm afraid that Maxwells Equations, which are at the heart of the problem take a bit of work and good calculus skills to learn. There is not simple formula to use with a calculator. However, here is an earlier thread here on PF that discusses your questions.

https://www.physicsforums.com/threa...tude-of-eddy-currents-retarding-force.822714/