On 01/15/2010 02:21 PM, Terry Blanton wrote: > On Fri, Jan 15, 2010 at 1:18 PM, Stephen A. Lawrence <[email protected]> wrote: >> I've been trying to get my head around the interactions of moving >> magnets, toroidal magnets, and toroidal cores. As I understand it, we >> have a situation like this: >> >> 1) Toroidal magnetic core has a non-toroidal field when current is off. >> Another magnet will be attracted to the core. > > I don't recall that we know anything about the core except it is > present in demo 2 Orbo and absent in demo 2 Pulse Motor. I don't > recall anyone saying the core was magnetic, only ferromagnetic.
Really! My mistake, then -- I thought I had read that the cores used were actually (statically) magnetized. For the last couple weeks I've been wondering about those "magnetic" cores. So if the cores aren't magnetic, then the mechanism for making the motor go around is presumably that the ferromagnetic cores are attracted to a magnet when the power is off, but when the power is on they're saturated, with an internal field which is entirely toroidal, and they don't respond to an external magnet. That would also make sense, I and I suspect it still falls to the same analysis: The cores will get warmer when there's no load. (I *think*.) If I have time on my hands (hah hah!) I may redo my handwaving analysis with the assumption that the cores are non-magnetized, and try to work out all the field directions to see if the energy transfer comes out in the right direction for the "less warming" hypothesis to be correct. [NB -- However the motor works, the nonlinearity of the cores at saturation must be entering into it. Otherwise it's very hard to see how toroidal coils could be interacting with the passing magnets at all, since their fields are entirely contained within the toroid.] > Of > course, it could become magnetic due to remanence. Or it could be a > high permeability metal with lots of nickel and little remanence, a > super-mumetal. > > T > >
