I got a very interesting tip today about a technology I didn’t know: Halbach magnetic arrays. Thanks to Nick Schlensky for that.
I’m hoping I can use it to remove the iron cores from my design and make it a lot lighter. But let’s get a clearer notion of what a Halbach array is and how it can help us.I modeled such a creature in FEMM, comparing it to a normal sequence of magnets to see the difference. Here are the photos. In all photos I placed exactly the same 5 cubic magnets, I just changed the orientation of their magnetization field.
As you can see, it is true that the Halbach layout creates a field that is very predominant on one side of the magnet row, and nearly non-existent on the opposite side. Very promising.
Again it is obvious the powerful asymmetry caused by this layout. It would be perfectly possible to make the iron core on top a lot thinner or even remove it altogether without losing performance.
Now let’s see how this behaves when facing another magnet… after all, the interesting point is the interaction with other fields.
Now I’m disappointed!! The Halbach magnet layout seems to improve very much the forces in the direction we don’t care about (radial, here the Y), and makes the ones we do care about (tangential, here the X) a lot smaller.
- X force (tangential in the motor, produces torque): from 46N down to 4 N
- Y force (radial in the motor, produces material stress): from 10N up to 80N