Selective alignment of stators in axial airgap electric devices comprising low-loss materials
An axial gap dynamoelectric machine comprises first and second stators disposed coaxially with an intermediate rotor. The stators are selectively aligned with an axial offset between the positions of their respective teeth and slots. The stators comprise toroidal cores having laminated layers composed of a material selected from the group consisting of amorphous and nanocrystalline metals and optimized Fe-based alloy. Optionally, the machine further comprises misalignment means for adjusting the offset of the stators. Adaptive adjustment permits the machine to be operated to in a mode that reduces the back EMF of the motor, allowing constant voltage to be maintained as speed is increased. Reducing back EMF also allows a wider range of operating speed, especially in combination with use of high pole counts. Alternatively, the machine can be operated, e.g. at lower speed, in a constant torque mode. The machine may exploit the high pole count achievable by use of improved soft magnetic materials. Also provided are techniques for reducing torque ripple during operation, and also for using the stator offset in combination with a dual full wave bridge rectifier arrangement.
1. A method for operating an axial air-gap machine system, comprising:
(a) providing an axial air-gap electric machine comprising a first stator having a plurality of teeth and a first set of windings positioned thereon; a second stator having a plurality of teeth and a second set of windings positioned thereon; and a rotor disposed for rotation about an axis, the rotor being disposed axially between the stators, and wherein the stators comprise toroidal cores having laminated layers composed of a material selected from the group consisting of amorphous and nanocrystalline metals and optimized Fe-based alloy;
(b) providing a power electronics means for interfacing and controlling the machine;
(c) operably connecting the power electronics means to the machine;
(d) selectively aligning the second stator with respect to the first stator such that the teeth of the second stator are offset by an offset amount from the teeth of the first stator;
(e) wherein the machine further comprises misalignment means for adjusting the offset amount, and the method further comprises selecting the offset amount to reduce the torque ripple of the machine and adjusting the offset amount using the misalignment means to maintain a substantially constant voltage characteristic and adaptively controlling the adjustment of the offset amount using a signal transmitted from the power electronics means to the misalignment means.
2. The method of claim 1 , wherein the machine is polyphase.
3. The method of claim 1 , wherein the misalignment means comprises at least one of: a two position solenoid; a voice coil motor; a piezoelectric actuator; a stepper or other motor with a gear or lead screw; a vacuum cylinder; an air pressure cylinder; a hydraulic cylinder; and a linear motor.
4. The method of claim 3 , wherein the misalignment means comprises a stepper motor and lead screw.
5. The method of claim 1 , wherein the laminated layers are composed of amorphous metal.
6. The method of claim 1 , wherein the laminated layers are composed of nanocrystalline metal.
7. The method of claim 1 , wherein the laminated layers are composed of optimized Fe-based alloy.
8. The method of claim 1 , wherein the rotor comprises a plurality of rotor magnets composed of a rare earth-transition metal alloy.
9. The method of claim 8 , wherein the rotor magnets are SmCo or FeNdB magnets.
10. The method of claim 1 , wherein the axial air-gap machine has a slot per phase per pole ratio that ranges from about 0.25 to 4.0.
11. The method of claim 10 , wherein the slot per phase per pole ratio ranges from about 0.25 to 1.
12. The method of claim 10 , wherein the slot per phase per pole ratio is 0.50.
13. The method of claim 1 , wherein the axial air-gap machine has at least 16 poles.
14. The method of claim 1 , wherein the axial air-gap machine has at least 32 poles.
15. The method of claim 1 , wherein the axial air-gap machine is run with a commutating frequency ranging from about 500 Hz to 3 kHz.
16. The axial air-gap machine of claim 15 , wherein the commutating frequency ranges from about 600 to 1000 Hz.