Robin07, this is starting to make more sense to me in
certain aspects now that you've elucidated a bit concerning
the electro-mechanical aspects of the system.
Previously I was a bit confounded not entirely so much
by what you'd described, but by what you hadn't mentioned.
I didn't recall that you had mentioned any kind of
mechanical or electrical switching relating to stator currents,
and since you apparently didn't want the field coil current
circulation to reverse, (i.e. when the rotor flux was
waning in the field coils) I thought that either I or you
was perhaps missing something rather essential, or that
I was just badly misunderstanding some
geometric / engineering aspect of your conception.
I'm now of the impression that you're essentially
talking about a DC motor operating in the inverse
('DC' generator) sense in that you're seeking to generate
strictly clockwise circulation (let's say) of eddy currents
in stator 'coils' mechanically in front of the
rotational path of a permanent magnet rotor's pole piece.
Thus there is mechanical drive (mutual repulsion)
from the mutual approach of the stator eddy coil
and rotor pole piece. Given a relativistic
point of view one could say the rotor moves and drives
the stator 'around', or the 'stator' shell moves relative
to a 'fixed' rotor and drives the inner rotor around.
In reality it's a mutual effect given Newton's law,
and either one can be viewed as in motion relative to the
other and the physics are still the same.
We're more used to seeing motors with inner
rotors and fixed casings rather than semi-free casings
being affected by the dynamics of inner / kinetic
rotor systems perhaps with the exception of toy gyroscopes.
Electro-mechanical switching analogous to a DC motor's
terminates the stator coil current when the rotor pole is
a bit before T.D.C (top dead center -- like a car's piston
when the spark fires in the combustion cycle)
alignment with the (eddy) stator coil
position.
Of course in a DC permanent magnet motor (or in an AC motor,
for that matter), it's a rotating magnetic field which rotates
in sync with and just positionally ahead of the mechanical rotor
that causes the rotor motion, but relative to the field
the rotor doesn't move at all, and all that's going on are
a couple of 'static' magnets attracting each other, the fact
that they're both rotating relative to some unrelated
shell is immaterial.
So in the case of interest to you, it's a 'DC' motor
(generator) where the rotor drives the 'rotation' of the
stator at the expense of rotor angular momentum w.r.t. the stator.
I don't see anything physically amiss about those general
engineering conceptions, and a half-efficient half-wave-AC
generator (disconnected during the rotor recession w.r.t.
the stator pole) certainly does the same thing.
Indeed as you may be aware common exercise bicycles
use eddy current based braking to generate
variable levels of mechanical resistance to the
human power driven rotor, not wholly unlike what you've
sometimes referred to.
w.r.t. coils and a bus bar, yes, I agree, doing the coils
of multitudes of thin wires isn't likely in your best interest
w.r.t. manufacturing. If you wanted a few score of
coils you could just use PCB traces on flexible substrates,
or a metal shell laminated to an insulating shell and C.N.C
mill insulating trenches in the formerly solid metal layer,
or use a laminated layer stack of 'rings' as a laminated
toroidal core might, metal deposition and resist patterning,
et. al.
Of course that's assuming you need numerous discrete coils
which may not be the case at all as far as I see it. . .
Of course you'd need a couple of bus bars, not just
one tangential one to provide a couple of points to
switch the stator loop current, so it'd be more of an 'C' or
OMEGA rather than a 'Q' with a single perpendicular bus bar
which couldn't be used to interrupt circumferential
loop current.
My apologies for the confusing acronym use and
rhetorical asides in my previous post(s), in part I was
also responding in the thread and context of berkeman's
post and explaining to him and other viewers what my
interpretations were with respect to what I thought
you were trying to conceptually express, since he'd
expressed some confusion about things you'd expressed
that I thought I could elucidate.
AFAIK = "As Far As I Know",
and "OP" is "Original Poster", yourself, in this case, though
just a common referential acronym to use in forum posts
when multiple parties are discussing aspects of a thread
that someone has started when discussion diverges to
include topical commentary between 3rd party
respondents.
With respect to the difficulty of the task of switching
coil circuits with respect to the kinetic and geometric
dynamics of a rotor in 3d, it's certainly not difficult
at all given the scales of speed and size you're talking
about. Such switching is not particularly different
that what you'd do in a stepper motor, and there's
no reason you can't use a 'position encoder' and
'state machine' (e.g. control logic circuit) to get
and process the information you need about when to switch,
just as in a brush-less DC motor controller.
Tell me, have you ever heard of Maxwell's Demon? That's
probably the ultimate abstraction of one aspect
of what you're trying to do, and at least in these
macroscopic speed/size scales there isn't a problem with respect
to getting the needed information concerning the available
(kinetic/magnetic) energy source...
The principles of reversibility and relativity are also
helpful in analyzing these sorts of problems.
W.r.t. the physics, concepts, and some conceivable applications,
this all encompasses subject areas I've been familiar with
and interested in for several years.
Your terminology / expression confused me for a while making
me think that perhaps you were talking about different kinds
of apparatus.
