Came across this motor, never heard of these before.
 wonder if the same idea could be used to generate power.

quote from ThinGap Announcement

ThinGap
developed a patented technology, which replaces the
iron core and wire windings of conventional motors
with a precision-machined copper sheet. This has
eliminated such issues as hysteresis, iron losses,
and cogging torque, while substantially reducing the
impact of eddy currents and back emf. The copper
sheets allow higher copper density and a higher
copper to total volume ratio, making ThinGap a
performance leader in high efficiency and power
density motors.

DC Ring Motor Powers 600-lb. Thrust Ducted-Fan
VENTURA, CA – April 20, 2010 – ThinGap LLC, a leader in high power density DC motors, today
announced a TG14090 Brushless DC Ring Motor that delivers 122 kW of shaft power, allowing a
ducted-fan to generate 600 pounds of thrust, depending on the fan blade design. The motor
provides an exceptional power to weight ratio – 6.4 HP per pound; a compact package that fits
the control inside the motor and low thermal load characteristics.


“ThinGap’s 14-inch electric ring motor allows a ducted fan to develop as much thrust as with a
gas engine, which is a game-changing milestone,” said Rean Pretorius, president, ThinGap, LLC.
“At 6.4 HP per pound, its power to weight ratio has not been achieved by any electric motor
currently in production and exceeds the aerospace engineering threshold of 5 HP per pound. The
advantage is much quieter operation for stealth, and less weight, which can be critical for UAV
surveillance and close support tactical applications.”


http://www.thingap.com/pdf/technologypaper.pdf

http://www.thingap.com/pdf/tg14090motor45clean.pdf

http://www.thingap.com/pdf/tg14010ds.pdf

Often air core motors were first used for stepper and servo
motor applications where rotor momentum was a factor.

These techniques are meant for very powerful motors that requires
lots of current as well as high voltages. For lower voltages the
P=E*I requirements would start to become unbalanced and
you would not be able to achieve the required driver device
efficiency specifications to drive the motor coils.

But I will say that very often air-core wound motors and
overunity operation seem to go hand in hand. Also as airstriker
says there is inductive field collapse back-emf and then there
is rotor momentum mechanical back-emf and these are really
separate issues but are treated the same by oversimplified
models because they are physical analogs but in different
systems.

:S:MarkSCoffman

Earth is a Hot air core planet. Float a heavy magnet.