On Sun, 23 Sep 2012 11:12:22 -0700, Cross-Slide wrote:

I remember reading a book about motors, and one of the more interesting
ones was referred to as a "Printed Pole Motor" IIRC.

This motor had multiple salient poles on the rotor, and they could be
re-magnetized as they passed one location of the stator.
This allowed the pole count of the rotor to be dynamically changed by
re-printing some of the salient poles to create larger or smaller groups
of North or South poles in succession around the rotor.

I think they were intended for very large motors for ball mills or some
large mining operations, of low speed, and thus many poles around the
rotors.
Also, it was suggested that since the poles could be re-written as the
motor ran, there could be theoretically non-integer numbers of poles
around the rotor, as they could be dynamically printed to match the
required speed.

Google cannot find any information on this...

Did I forget the actual name of this class of motor?

Sounds wacky; I've never heard of it.

Dunno how it'd work with rare earth magnets -- you'd need a honkin
powerful magnetic field at the "printer", and it'd need to be fast -- and
those two don't go together well.

I suspect that as a PM motor technology it probably made sense if the
best magnet material you had was AlNiCo (which is really easy to
demagnetize and remagnetize), but with rare earths (which aren't) you get
a huge efficiency advantage from the magnet's strength, and a huge
increase in difficulty of remagnetizing the thing, so the net result may
be that it's not worth it.

For a Really Honkin' Big motor it may make sense to have a bunch of poles
on the rotor, made with rare earth magnets, that can be mechanically
flipped, and a bunch of servoes to mechanically flip them under control
from some smart algorithm -- but that's not "printing".

--
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com