Planar stator configurations for axial flux machines
In some embodiments, two or more different types of stator structures may be disposed within a gap of an axial flux machine. Such arrangements may be advantageous, for example, for producing a machine optimized for multiple modes of operation, such as mechanical torque generation, conversion of mechanical torque to electrical power, and/or dissipation of mechanical power. Further, in some embodiments, an axial flux machine may include a planar stator having a winding arranged to be positioned within the machine's active region, and may further include at least one switch configured to be selectively closed to establish an electrical connection between respective ends of the winding at a time that the winding is not coupled to an external power source.
1. An apparatus, comprising:
a rotor configured to rotate about an axis of rotation, the rotor including one or more magnets that generate first magnetic flux in an active region;
a first conductive sheet positioned within the active region so that generation of eddy currents within the first conductive sheet imposes a drag force on the rotor;
a stator structure including at least a first winding positioned within the active region;
at least first and second terminals connected to different portions of the first winding so that (A) application of current between the first and second terminals causes the first winding to generate a second magnetic flux in the active region or (B) flux linkage between the first winding and the one or more magnets while the rotor is rotating generates voltage between the first and second terminals;
at least a first switch configured and arranged to selectively couple one or more circuit components between the first and second terminals, thereby regulating a flow of current through the first winding; and
control circuitry configured to adjust a manner in which the first switch is operated to selectively couple the one or more circuit components between the first and second terminals and thereby selectively supplement or selectively counteract the drag force on the rotor.
2. The apparatus of claim 1 , wherein:
the stator structure has a generally planar shape; and
the apparatus is an axial flux machine in which the one or more magnets generate the first magnetic flux, generally parallel to the axis of rotation, within a gap in which the stator structure is positioned.
3. The apparatus of claim 2 , wherein:
the one or more circuit components include a power source; and
the control circuitry is configured to operate the first switch to selectively couple the power source between the first and second terminals of the first winding to a power source such that, during at least a first mode of operation of the axial flux machine, the first winding generates the second magnetic flux generally parallel to the axis of rotation.
4. The apparatus of claim 2 , wherein:
the one or more circuit components include an energy storage element; and
the control circuitry is configured to operate the first switch to selectively couple the energy storage element between the first and second terminals such that, during at least a first mode of operation of the axial flux machine, the energy storage element receives power generated by the first winding in response to rotation of the rotor.
5. The apparatus of claim 2 , wherein:
the one or more circuit components include a conductor; and
the first switch is configured and arranged to be selectively closed to establish an electrical connection between the first and second terminals via the conductor at a time that the first winding is not coupled to an external power source.
6. The apparatus of claim 5 , wherein:
the control circuitry is further configured to cause the first switch to be modulated to control a time average conductivity between the first and second terminals.
7. The apparatus of claim 2 , wherein:
the one or more circuit components include at least one dissipative element; and
the first switch is further configured and arranged to selectively couple the at least one dissipative element between the first and second terminals.
8. The apparatus of claim 7 , wherein:
the control circuitry is further configured to cause the first switch to be modulated to control a time average conductivity between the first and second terminals.
9. A method of operating the apparatus of claim 2 , comprising:
using the control circuitry to operate the first switch in a first manner to supplement or counteract the drag force on the rotor by a first amount; and
using the control circuitry to operate the first switch in a second manner to supplement or counteract the drag force on the rotor by a second amount different than the first amount.
10. The method of claim 9 , further comprising:
adjusting a position of the first conductive sheet relative to the active region to alter the drag force.
11. The method of claim 9 , wherein:
the one or more circuit components include a power source;
using the control circuitry to operate the first switch in the first manner comprises using the control circuitry to operate the first switch to selectively couple the power source between the first and second terminals so that the first winding generates a first amount of the second magnetic flux generally parallel to the axis of rotation; and
using the control circuitry to operate the first switch in the second manner comprises using the control circuitry to operate the first switch to selectively couple the power source between the first and second terminals so that the first winding generates a second amount of the second magnetic flux generally parallel to the axis of rotation, the second amount being different than the first amount.
12. The method of claim 9 , wherein:
the one or more circuit components include at least one dissipative element;
using the control circuitry to operate the first switch in the first manner comprises using the control circuitry to modulate the first switch to selectively couple the at least one dissipative element between the first and second terminals such that a first time average conductivity is established between the first and second terminals; and
using the control circuitry to operate the first switch in the second manner comprises using the control circuitry to modulate the first switch to selectively couple the at least one dissipative element between the first and second terminals such that a second time average conductivity, which is different than the first time average conductivity, is established between the first and second terminals.
13. The apparatus of claim 1 , wherein:
the one or more circuit components include a power source; and
the control circuitry is configured to operate the first switch to selectively couple the power source between the first and second terminals such that, during at least a first mode of operation of the apparatus, the first winding generates the second magnetic flux.
14. The apparatus of claim 1 , wherein:
the one or more circuit components include an energy storage element; and
the control circuitry is configured to operate the first switch to selectively couple the energy storage element between the first and second terminals such that, during at least a first mode of operation of the apparatus, the energy storage element receives power generated by the first winding in response to rotation of the rotor.
15. The apparatus of claim 1 , wherein:
the one or more circuit components include a conductor; and
the first switch is configured and arranged to be selectively closed to establish an electrical connection between the first and second terminals via the conductor at a time that the first winding is not coupled to an external power source.
16. The apparatus of claim 15 , wherein:
the control circuitry is further configured to cause the first switch to be modulated to control a time average conductivity between the first and second terminals.
17. The apparatus of claim 1 , wherein:
the one or more circuit components further include at least one dissipative element; and
the first switch is further configured and arranged to selectively couple the at least one dissipative element between the first and second terminals.
18. The apparatus of claim 17 , wherein:
the control circuitry is further configured to cause the first switch to be modulated to control a time average conductivity between the first and second terminals.
19. A method of operating the apparatus of claim 1 , comprising:
using the control circuitry to operate the first switch in a first manner to supplement or counteract the drag force on the rotor by a first amount; and
using the control circuitry to operate the first switch in a second manner to supplement or counteract the drag force on the rotor by a second amount different than the first amount.
20. The method of claim 19 , further comprising:
adjusting a position of the first conductive sheet relative to the active region to alter the drag force.