IPC분류정보
국가/구분 |
United States(US) Patent
등록
|
국제특허분류(IPC7판) |
|
출원번호 |
US-0463275
(2009-05-08)
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등록번호 |
US-8242649
(2012-08-14)
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발명자
/ 주소 |
|
출원인 / 주소 |
|
대리인 / 주소 |
|
인용정보 |
피인용 횟수 :
12 인용 특허 :
92 |
초록
▼
A low-cost minimal-loss zero-maintenance flywheel battery, to store electric power from a DC power source by conversion to kinetic energy, and regenerate electric power as needed. Its vertical spin-axis rotor assembly is supported axially by repelling annular permanent magnets, and is centered by ce
A low-cost minimal-loss zero-maintenance flywheel battery, to store electric power from a DC power source by conversion to kinetic energy, and regenerate electric power as needed. Its vertical spin-axis rotor assembly is supported axially by repelling annular permanent magnets, and is centered by ceramic ball bearings which have axial preload that prevents vibration and augments axial rotor support. A regenerative multi-pole permanent-magnet motor, controlled by its 2-phase stator current, and connected by power and signal conductors to power interface electronics, is integrated within the flywheel assembly, in a vacuum enclosure supported by a self-leveling structure. Sinusoidal 2-phase stator currents are controlled by high-frequency pulse-width-modulated H-bridge power electronics that draw and regenerate controlled DC current with minimal ripple, responsive to respective 2-phase rotation angle sensors, the DC power voltage, and other settings. The electronics includes logic and over-voltage protection to prevent otherwise possible damaging current and voltage.
대표청구항
▼
1. A flywheel battery, for storing electric power from a DC power bus as kinetic energy and regenerating electric power with minimal losses, comprising: motor/generator means in a flywheel assembly, including poly-phase stator windings for conducting poly-phase sinusoidal currents, the windings form
1. A flywheel battery, for storing electric power from a DC power bus as kinetic energy and regenerating electric power with minimal losses, comprising: motor/generator means in a flywheel assembly, including poly-phase stator windings for conducting poly-phase sinusoidal currents, the windings formed from multi-strand insulated conductors for eddy blocking and bucking, cooperative with a juxtaposed alternated-pole permanent-magnet array affixed to rotor iron for providing radial flux that interacts with said currents, and rotor angle sensors each aligned with a respective stator winding phase, for providing poly-phase feedback signals that vary essentially sinusoidally with rotor angle;power interface electronics, with H-bridges connected to the DC power bus and to the poly-phase stator windings of the motor/generator, said electronics responsive to the rotor angle sensors and to the DC bus voltage, for controlling by pulse-width-modulation poly-phase current through the stator windings so its resultant magnetic field rotates synchronously with the rotor;a flywheel rotor having a vertical spin axis, supported by bearing means comprised of repelling annular axial-field magnets centered by two ceramic ball bearings, including axial preload springs that augment the axial support of said axial-field magnets, the rotor including rotary inertia for storing kinetic energy, plus rotor elements of the motor/generator;a vacuum enclosure, containing mounting therein for the flywheel assembly, and hermetic connections to the power interface electronics outside the enclosure; anda housing and support structure, for the vacuum enclosure and flywheel assembly therein;wherein said bearing means further comprises:a stationary annular permanent-magnet, affixed to a cylindrical support that maintains precise centering around a center shaft, within and supported by the vacuum enclosure, to provide an axial magnetic field uniform with rotor angle, beneath the rotor assembly;a like rotatable annular permanent-magnet, affixed to the rotor assembly and precisely centered around said center shaft by upper and lower ball bearings, this permanent-magnet juxtaposed above said stationary annular permanent-magnet, and having an opposing axial magnetic field so that the two magnets repel each other, to provide a stable axial lift force for supporting the flywheel assembly weight;a first ceramic ball bearing near the top of the rotor assembly, having a slip fit around the center shaft and its inner race, and a slip fit around its outer race with an axial restraint, so that the ball bearing can slide axially with the rotor while it maintains precise rotor centering and augments the rotor axial support;a first axially compressed annular spring to provide axial lift force to the first ball bearing inner race, for providing consistent axial preload and also for providing flexible rotor lift;a second like ceramic ball bearing near the bottom of the rotor assembly, having a slip fit around the center shaft and its inner race, and a slip fit around its outer race with an axial restraint, so that the bearing can slide axially with the rotor while it maintains precise rotor centering and augments the rotor axial support; anda second like annular spring to provide axial lift force to the second ball bearing inner race, for providing consistent axial preload and also for providing flexible rotor lift. 2. The flywheel battery of claim 1, wherein said power interface electronics further comprises: signal processing means, responsive to Hall-effect rotor angle sensors corresponding to each poly-phase stator winding phase, each Hall-effect sensor aligned with a respective stator winding phase so the sensor output signal is in phase with the corresponding stator winding voltage, and responsive to the DC power bus voltage and input commands, for controlling pulse-width-modulated H-bridge power switches; andH-bridge power switches, responsive to the signal processing means, connected across the DC power bus, and through series output inductors to respective motor stator windings, including diagonal pairs of switch-mode transistors, for efficient sinusoidal poly-phase stator winding current control, and for exchanging DC current with the DC power bus. 3. The flywheel battery of claim 1, wherein said motor/generator further comprises: poly-phase stator windings, embedded in a stator winding assembly, formed from multi-strand conductors that provide means for blocking and bucking eddy currents therein, for producing torque between the rotor and the stator, and for exchanging electric power with the power interface electronics with minimal eddy current losses;multiple pairs of rectangular motor magnets, supported in the outer cylinder rotor iron, with one magnet of the pair magnetized radially outward and the other magnetized radially inward, to provide a radial magnetic flux pattern which varies substantially sinusoidally with rotor angle, through the cooperative stator winding axial segments in the radial magnetic flux;rotor angle sensors, each aligned with a respective stator winding phase and affixed to the stator winding assembly, responsive to the peripheral magnetic field of the motor magnets, for providing poly-phase feedback signals which vary substantially sinusoidally with rotor angle;an outer cylinder of high-permeability rotor iron, for supporting rectangular magnets affixed therein and for providing an outer magnetic flux return path; andan inner cylinder of high-permeability rotor iron, affixed to the outer cylinder, for providing an inner magnetic flux return path, and for completing through the stator windings a radial magnetic flux pattern which rotates synchronously with the rotor. 4. The flywheel battery of claim 1, wherein said poly-phase stator windings each further comprises a group of conductor strands, each insulated from the others between winding terminal connections, the group spiraled, to equalize, between winding terminal connections, voltage across each strand, and formed so magnetic field from its current does not significantly affect peripheral radial motor magnet field detected by the rotor angle sensors that provide rotor angle feedback signals to the power interface electronics. 5. The flywheel battery of claim 1, wherein said motor/generator has 2-phase stator windings. 6. The flywheel battery of claim 5, wherein said power interface electronics further comprises a circuit for providing four regulated and floating 12 vdc outputs, to reliably power upper H-bridge gate drivers, which control the four upper power switching transistors in the two H-bridges. 7. The flywheel battery of claim 1, wherein said power interface electronics further comprises a circuit for providing regulated +12 vdc, −12 vdc, and +5 vdc supplies to the power interface electronics and +5 vdc to Hall-effect sensors that detect rotor angle. 8. The flywheel battery of claim 1, wherein said power interface electronics further comprises circuits to provide accurate absolute value of respective stator winding current, for negative feedback to minor loops that control pulse-width modulation for H-bridge current control, in motor drive and regeneration modes. 9. The flywheel battery of claim 1, wherein said power interface electronics further comprises over-voltage protection by a transient voltage suppressor that clamps the DC power bus voltage and provides a signal that inhibits power regeneration, in concert and redundant with slower DC voltage feedback control. 10. The flywheel battery of claim 1, wherein said power interface electronics further comprises under-voltage lockout, which inhibits drive to power transistors if voltage supplied to signal-processing circuits is below prescribed levels. 11. The flywheel battery of claim 1, wherein said power interface electronics further comprises switch-mode power transistors in H-bridge configuration, which control motor drive current by pulse-width-modulation switching of diagonal transistor pairs in said H-bridge, wherein turn-off of one transistor in each transistor pair is delayed a time approximating the pulse-width-modulation period, to minimize power lost by the electronics and reduce high-frequency pulse amplitudes at the pulse-width-modulation frequency, and wherein turn-on delay at each mode transition is included to prevent shoot-through currents. 12. The flywheel battery of claim 1, wherein said housing and support structure further comprises self-leveling means having a frame which rests on a liner, the frame from its upper structure supporting two gimbals, the first gimbal having a nominally horizontal axis to accommodate rotation by gravitational force on the flywheel assembly center of mass, is attached to the upper structure, and the second having an axis in a horizontal plane 90 degrees from the first, attached to a rigid cylinder affixed to the top of the flywheel assembly vacuum enclosure, to accommodate rotation about the gimbal axis, to maintain a level vertical spin-axis flywheel assembly within a vacuum enclosure which does not rotate parallel to said spin-axis. 13. The flywheel battery of claim 1, wherein said vacuum enclosure further comprises a sealable cylindrical container having a relatively large space inside, and means for purging internal contaminants by maintaining the enclosure and its flywheel assembly contents in vacuum while at elevated temperature, the enclosure and its contents having a center of mass coincident with its geometric center, to facilitate self-leveling. 14. The flywheel battery of claim 1, further comprising fail-safe backup means for said bearing means, including: a stationary annular axial and radial backup bearing, having a sliding surface beneath the rotor, to restrict downward rotor excursions, which does not normally make contact, and a sliding surface surrounding the rotor near its bottom, to restrict radial excursions, which does not normally make contact; anda stationary annular axial and radial backup bearing, having a sliding surface above the rotor, to restrict upward rotor excursions, which does not normally make contact, and a sliding surface surrounding the rotor near its top, to restrict radial excursions, which does not normally make contact. 15. The flywheel battery of claim 1, wherein said power interface electronics further comprises display means to visually present flywheel rotor speed, DC power bus voltage, external power exchange with the DC power bus, and flywheel system idling power. 16. The flywheel battery of claim 1, wherein said power interface electronics further comprises automatic shut-down means responsive to an accelerometer mounted to the flywheel assembly, to initiate a command to reduce rotor speed level if excess vibration is detected. 17. The flywheel battery of claim 1, wherein said two ball bearings are axially positioned the furthest practical distance from each other, cooperative with a rotor assembly having a maximum practical axial-to-diameter dimension ratio, to minimize radial loads on the ball bearings caused by precession torque on the spinning rotor due to Earth rotation about its axis. 18. A flywheel battery, for storing electric power from a DC power bus as kinetic energy and regenerating electric power with minimal losses, comprising: motor/generator means in a flywheel assembly, including poly-phase stator windings for conducting poly-phase sinusoidal currents, the windings formed from multi-strand insulated conductors for eddy blocking and bucking, cooperative with a juxtaposed alternated-pole permanent-magnet array affixed to rotor iron for providing radial flux that interacts with said currents, and rotor angle sensors each aligned with a respective stator winding phase, for providing poly-phase feedback signals that vary essentially sinusoidally with rotor angle;power interface electronics, with H-bridges connected to the DC power bus and to the poly-phase stator windings of the motor/generator, said electronics responsive to the rotor angle sensors and to the DC bus voltage, for controlling by pulse-width-modulation poly-phase current through the stator windings so its resultant magnetic field rotates synchronously with the rotor;a flywheel rotor having a vertical spin axis, supported by bearing means comprised of repelling annular axial-field magnets centered by two ceramic ball bearings, including axial preload springs that augment the axial support of said axial-field magnets, the rotor including rotary inertia for storing kinetic energy, plus rotor elements of the motor/generator;a vacuum enclosure, containing mounting therein for the flywheel assembly, and hermetic connections to the power interface electronics outside the enclosure; anda housing and support structure, for the vacuum enclosure and flywheel assembly therein;wherein said power interface electronics further comprises switch-mode power transistors in H-bridge configuration, which control motor drive current by pulse-width-modulation switching of diagonal transistor pairs in said H-bridge, wherein turn-off of one transistor in each transistor pair is delayed a time approximating the pulse-width-modulation period, to minimize power lost by the electronics and reduce high-frequency pulse amplitudes at the pulse-width-modulation frequency, and wherein turn-on delay at each mode transition is included to prevent shoot-through currents. 19. A flywheel battery, for storing electric power from a DC power bus as kinetic energy and regenerating electric power with minimal losses, comprising: motor/generator means in a flywheel assembly, including poly-phase stator windings for conducting poly-phase sinusoidal currents, the windings formed from multi-strand insulated conductors for eddy blocking and bucking, cooperative with a juxtaposed alternated-pole permanent-magnet array affixed to rotor iron for providing radial flux that interacts with said currents, and rotor angle sensors each aligned with a respective stator winding phase, for providing poly-phase feedback signals that vary essentially sinusoidally with rotor angle;power interface electronics, with H-bridges connected to the DC power bus and to the poly-phase stator windings of the motor/generator, said electronics responsive to the rotor angle sensors and to the DC bus voltage, for controlling by pulse-width-modulation poly-phase current through the stator windings so its resultant magnetic field rotates synchronously with the rotor;a flywheel rotor having a vertical spin axis, supported by bearing means comprised of repelling annular axial-field magnets centered by two ceramic ball bearings, including axial preload springs that augment the axial support of said axial-field magnets, the rotor including rotary inertia for storing kinetic energy, plus rotor elements of the motor/generator;a vacuum enclosure, containing mounting therein for the flywheel assembly, and hermetic connections to the power interface electronics outside the enclosure; anda housing and support structure, for the vacuum enclosure and flywheel assembly therein;wherein said housing and support structure further comprises self-leveling means having a frame which rests on a liner, the frame from its upper structure supporting two gimbals, the first gimbal having a nominally horizontal axis to accommodate rotation by gravitational force on the flywheel assembly center of mass, is attached to the upper structure, and the second having an axis in a horizontal plane 90 degrees from the first, attached to a rigid cylinder affixed to the top of the flywheel assembly vacuum enclosure, to accommodate rotation about the gimbal axis, to maintain a level vertical spin-axis flywheel assembly within a vacuum enclosure which does not rotate parallel to said spin-axis.
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