Wirelessly transferring power within an electric machine having AC and DC rotor coils
A stator defines multiple stator poles with associated stator windings. A rotor defines multiple fixed rotor poles with associated teeth with a ferromagnetic material. The fixed rotor poles have associated rotor windings configured to be energized substantially by the stator. Each of the rotor windings is associated with the tooth. Each of the rotor windings includes an alternating current (AC) coil (or auxiliary coil) configured to carry an AC current induced by an AC current flowing in the stator. A direct current (DC) coil (or primary coil) defines a rotor field energizable by magnetic fields produced by the stator windings to produce relative forces between the rotor and the stator. The DC coil is at least partially powered or controlled by the AC coil.
1 . A field wound synchronous electric machine comprising:
a stator including stator windings configured to be energized to define stator poles;
a rotor including rotor windings configured to be energized to define fixed rotor poles with associated teeth comprising a ferromagnetic material and including a winding portion and a cap, where the fixed rotor poles interact with the stator poles to produce relative forces between the rotor and the stator, each of the rotor windings is associated with a respective at least one tooth of the teeth, and each of the rotor windings comprises:
an auxiliary coil configured to carry a first current induced by an AC current flowing in the stator, and
a primary coil configured to carry a second current that defines a respective one of the fixed rotor poles; and
a rectifier electrically coupled to the auxiliary coil and the primary coil of a first rotor winding of the rotor windings, the rectifier being configured to receive the first current induced in the auxiliary coil of the first rotor winding and to generate the second current in the primary coil of the first rotor winding from the first current induced in the auxiliary coil;
wherein a D-axis of the primary coil of the first rotor winding in a synchronous reference frame extends radially outward from a rotor shaft through the rotor pole of the rotor winding, and
wherein a D-axis of the auxiliary coil of the first rotor winding in the synchronous reference frame is
(i) substantially perpendicular to the D-axis of the primary coil of the first rotor winding in the synchronous reference frame, and the auxiliary coil extends through a first channel of the cap of a first tooth of the teeth and a second channel of a trunk of the rotor or the first tooth, or
(ii) substantially aligns with the D-axis of the primary coil of the first rotor winding in the synchronous reference frame, and the primary coil and the auxiliary coil of the first rotor winding are wrapped around a winding portion of the first tooth of the teeth.
2 . The field wound synchronous electric machine of claim 1 , further comprising a controller configured to:
drive the stator windings to induce the first current in the rotor windings; and
drive the stator windings to generate magnetic fields that provide a magnetomotive force that interacts with fixed rotor poles of the rotor to move the rotor relative to the stator.
3 . The field wound synchronous electric machine of claim 1 , wherein the rectifier comprises a passive rectifier.
4 . The field wound synchronous electric machine of claim 1 , wherein the rectifier comprises an active rectifier comprising one or more gates.
5 . The field wound synchronous electric machine of claim 1 , wherein the rectifier comprises a resonance capacitor and a voltage regulator configured to regulate a voltage across the resonance capacitor.
6 . The field wound synchronous electric machine of claim 1 , wherein the rectifier comprises a secondary inductor on a DC side of the rectifier.
7 . The field wound synchronous electric machine of claim 1 , wherein the auxiliary coil of each rotor winding is a first auxiliary coil, and wherein each rotor winding further comprises a second auxiliary coil, wherein the first auxiliary coil and the second auxiliary coil of each rotor winding have different D-axis alignments in a synchronous reference frame.
8 . The field wound synchronous electric machine of claim 7 , wherein the first auxiliary coil and the second auxiliary coil of each rotor winding each have a D-axis in a synchronous reference frame different from a primary coil D-axis of each rotor winding in the synchronous reference frame.
9 . The field wound synchronous electric machine of claim 1 , further comprising a spacer between the auxiliary coil and primary coil.
10 . The field wound synchronous electric machine of claim 1 , wherein an AC voltage within the auxiliary coil of each rotor winding is at least 5 times more than a voltage within the primary coil of the rotor winding, and wherein a DC current within the primary coil of each rotor winding is at least 5 times more than a current within the auxiliary coil of the rotor winding.
11 . The field wound synchronous electric machine of claim 1 , further comprising a plurality of rectifiers and the rectifier is a first rectifier of the plurality of rectifiers, each rectifier of the plurality of rectifiers being associated with a respective rotor winding of the rotor windings, being rotationally fixed to the rotor, being electrically coupled to the auxiliary coil and to the primary coil for the respective rotor winding, and, for the respective rotor winding, being configured to receive the first current induced in the auxiliary coil and to generate the second current in the primary coil from the first current induced in the auxiliary coil.
12 . The field wound synchronous electric machine of claim 1 , wherein the primary coil is positioned on a major D-axis in a synchronous reference frame, and the auxiliary coil is positioned on a minor D-axis in the synchronous reference frame.
13 . The field wound synchronous electric machine of claim 1 , wherein the auxiliary coil is configured to further receive data signals wirelessly transmitted by the stator.
14 . The field wound synchronous electric machine of claim 13 , wherein control circuitry is configured to:
detect the data signals by monitoring the first current for frequency, magnitude, or phase modulations that encode data, and
decode the frequency, magnitude, or phase modulations.
15 . The field wound synchronous electric machine of claim 1 , further configured to send data signals through the auxiliary coil to communicate with the stator, wherein the data signals provide control information for the field wound synchronous electric machine, the control information including rotor speed, current level, temperature, or other state information.
16 . The field wound synchronous electric machine of claim 1 , further comprising:
a major D-axis that is used for torque production, and
a minor D-axis that is used for wireless power transfer between the stator and rotor, data communication between the stator and rotor, or both wireless power transfer and data communication between the stator and rotor.
17 . The field wound synchronous electric machine of claim 1 , wherein a perturbation is applied to the D-axis, a Q-axis, or a Z-axis of the auxiliary coil to generate a field excitation for power transfer.
18 . A method of operating for a field wound synchronous electric machine, the method comprising:
carrying, by an auxiliary coil of a first rotor winding of a plurality of rotor windings of a rotor of the field wound synchronous electric machine, a first current induced by an AC current flowing in a stator of the field wound synchronous electric machine, the stator including stator windings configured to be energized to define stator poles and the rotor windings configured to be energized to define fixed rotor poles with associated teeth comprising a ferromagnetic material and including a winding portion and a cap;
receiving, by a rectifier, the first current induced in the auxiliary coil, the rectifier being rotationally fixed to the rotor and electrically coupled to the auxiliary coil and to a primary coil of the first rotor winding;
generating, by the rectifier, a second current from the first current induced in the auxiliary coil; and
carrying, by the primary coil, the second current from the rectifier, the second current defining a fixed rotor pole of the fixed rotor poles that interacts with the stator poles to produce relative forces between the rotor and the stator,
wherein a D-axis of the primary coil of the first rotor winding in a synchronous reference frame extends radially outward from a rotor shaft through the rotor pole of the rotor winding, and
wherein a D-axis of the auxiliary coil of the first rotor winding in the synchronous reference frame is
(i) substantially perpendicular to the D-axis of the primary coil of the first rotor winding in the synchronous reference frame, and the auxiliary coil extends through a first channel of the cap of a first tooth of the teeth and a second channel of a trunk of the rotor or the first tooth, or
(ii) substantially aligns with the D-axis of the primary coil of the first rotor winding in the synchronous reference frame, and the primary coil and the auxiliary coil of the first rotor winding are wrapped around a winding portion of the first tooth of the teeth.
19 . The method of claim 18 , further comprising:
driving, by a controller, the stator windings to induce the first current in the rotor windings; and
driving, by the controller, the stator windings to generate magnetic fields that provide a magnetomotive force that interacts with fixed rotor poles of the rotor to move the rotor relative to the stator.
20 . The method of claim 18 , wherein the rectifier comprises an active rectifier, and the method further comprising:
controlling one or more gates of the active rectifier to rectify the first current induced in the rotor windings.
21 . The method of claim 18 , further comprising:
regulating, by a voltage regulator, a voltage across a resonance capacitor of the rectifier.