PERMANENT MAGNET MACHINE WITH CONICAL STATOR
A permanent magnet machine includes a stator, a rotor configured to coaxially rotate with respect to the stator and having a plurality of permanent magnets coupled thereto, and an air gap between the stator and the rotor having a magnitude that is continuously adjustable. The air gap may be adjusted to optimize torque, minimize back EMF, or optimize any characteristic of the permanent magnet machine during rotation.
1 . A permanent magnet machine comprising:
a stator;
a rotor configured to coaxially rotate with respect to the stator and having a plurality of permanent magnets coupled thereto; and
an air gap between the stator and the rotor;
wherein the magnitude of the air gap is continuously adjustable.
2 . The permanent magnet machine of claim 1 , wherein the stator has a generally tapered inner surface, the rotor has a generally tapered outer surface, the air gap is defined by the inner surface of the stator and the outer surface of the rotor.
3 . The permanent magnet machine of claim 2 , wherein the inner surface of the stator and the outer surface of the rotor are both generally conical and concentric.
4 . The permanent magnet machine of claim 3 , wherein the rotor is configured to translate axially within the stator.
5 . The permanent magnet machine of claim 4 , wherein the ratio of axial translation to change in magnitude of the air gap is between about 2.9 and 5.75.
6 . A stator for a permanent magnet machine comprising:
a plurality of surface-mount magnets defining an outer surface;
wherein the outer surface is generally tapered and configured to translate axially within a matching rotor.
7 . The stator of claim 6 , wherein the outer surface is conical.
8 . The stator of claim 7 , wherein the outer surface is defined by a cone having a ratio of base to height of between approximately 0.25 and 3.0.
9 . A method for operating a permanent magnet machine, comprising:
providing a stator;
providing a rotor configured to coaxially rotate with respect to the stator and having a plurality of permanent magnets coupled thereto, wherein an air gap is defined between the stator and the rotor;
adjusting the position of the rotor with respect to the stator, during rotation, to adjust the magnitude of the air gap.
10 . The method of claim 9 , wherein the stator has a generally tapered inner surface, the rotor has a generally tapered outer surface, the air gap is defined by the inner surface of the stator and the outer surface of the rotor.
11 . The method of claim 10 , wherein the inner surface of the stator and the outer surface of the rotor are both generally conical and concentric.
12 . The method of claim 11 , wherein the rotor is configured to translate axially within the stator.
13 . The method of claim 12 , wherein the ratio of axial translation to change in magnitude of the air gap is between about 2.9 and 5.75.
14 . The method of claim 1 , further including continuously adjusting the air gap during rotation while monitoring a property of the permanent magnet machine to optimize that property.
15 . The method of claim 14 , wherein the property is torque.
16 . The method of claim 1 , further including continuously adjusting the air gap to minimize back EMF.