Abstract: An active magnetic thrust bearing, acting on only a single axial side of a rotor, while also having an efficient permanent magnet bias for linearized and highly amplified control, uses two concentric ring poles that axially face a ferromagnetic axial surface of the rotor, creating two annular axial air gaps. A permanent magnet in the stator drives a bias flux through a first path including two radially spaced concentric ring poles and their air gaps, and an annular region of the rotor axially aligned between the two ring poles. The permanent magnet also drives flux through a second high-reluctance flux path in the stator, by-passing the rotor. An electromagnetic coil in the stator drives a control flux in a circuit including the second path, both ring poles and axial air gaps, and the shunt. The bias and control fluxes are therefore superposed in the axial air gaps for amplified response.

Abstract: A wind turbine for generating electrical power from wind energy includes a turbine rotor mounted for rotation in wind, and having multiple blades for converting energy in the wind into rotational energy. A generator is coupled with said turbine rotor such that said turbine rotor drives said generator. The generator has a stationary air core armature that is located in a magnetic airgap between two generator rotor portions. The generator rotor portions have circumferential arrays of multiple alternating polarity permanent magnets attached to ferromagnetic back irons such that the permanent magnets drive magnetic flux back and forth between each rotor portion and through the stationary air core armature. The stationary air core armature has multiple phase windings of multiple individually insulated strand conductor wire that is wound with two separate portions including an active length portion and an end turn portion.

Abstract: A flywheel energy storage system for preventing power interruptions to a load from interruptions of primary power includes a flywheel supported for rotation about an axis on a bearing system, and a motor-generator having a rotor coupled with the flywheel, and having a stator with multiple armature windings and a field coil. The field coil generates flux that passes through the armature windings as the rotor rotates to produce torque for accelerating the flywheel during charging, and produces electrical power from the flywheel during discharge. The armature windings are energized by a DC buss that is supplied by a rectifier connected to primary power. The flywheel system provides instantaneous full power capability along with output control for extracting more energy from the flywheel. The field coil is oversized and is powered in standby operation to produce an armature back emf that is at least 75% of the DC buss voltage.

Abstract: A flywheel energy storage system having magnetic bearings that are preferably homopolar, that is, the magnetic fields do not alternate polarity around a given circumferential location. This significantly increases efficiency, reduces heating in the evacuated flywheel environment and reduces power requirements of the electronics. The magnetic bearings are also preferably permanent magnet biased. Permanent magnets provide bias flux in the magnetic bearings which produces several benefits. The bias flux linearizes and amplifies the response of the magnetic bearings for much easier and simpler control. Compared with designs using electromagnetic bias, permanent magnet bias results in lower power consumption and increased linearity in force to displacement response due to the large reluctance offered by the permanent magnets. Permanent magnet bias also allows use of only one amplifier per axes instead of two. This greatly reduces the costs and increases reliability.

Abstract: Accordingly, the invention provides a speed control for a flywheel energy storage system that provides accurate and reliable speed control for long-term operation. The speed control uses a current limiting means that safely limits the acceleration current to the motor for accelerating flywheel, and a rate controller that digitally switches the acceleration current on and off to maintain the desired steady state speed. The rate controller turns the acceleration current off when the flywheel speed is above the desired steady state speed and then turns the acceleration current back on when the flywheel speed falls below the desired steady state speeds. The digital type speed control can be made both more accurate and reliable by using straightforward on/off control about the desired steady state operating speed.

Abstract: A combination mechanical and magnetic support system for a flywheel power supply for storing and retrieving energy in which said power supply includes a flywheel that spins about an axis of rotation inside an evacuated chamber, and an attached motor/generator for accelerating and decelerating the flywheel for storing and retrieving the energy. One or more rolling element bearings and at least one magnetic bearing are mounted in bearing housings attached to the chamber for providing radial and axial support for the flywheel in the chamber. A wire metal mesh spring damper between portions of the rolling element bearings and the bearing housings provide both radial damping and radial centering stiffness to the wheel. The support system has a radial stiffness that allows a cylindrical rigid body resonance of said flywheel to occur at a speed less 30% of the normal operating speed.

Abstract: A flywheel power source having a flywheel supported by a bearing system for rotation inside an evacuated container. A brushless motor and generator is coupled to the flywheel for accelerating and decelerating the flywheel for storing and retrieving energy. The generator has a rotor coupled to the flywheel, and a stationary stator wound using multiple-strand individually insulated conductor wire coils. A heat energy transfer system passively cools the stator by heat transfer from the stator to an unpumped liquid coolant surrounding the coils and in intimate contact with the conductors in the coils. The stator is mounted in a stator coolant vessel that is partially filled with the coolant. The liquid coolant limits the maximum temperature of the coils during discharging of the flywheel power source.

Abstract: An in-situ curing filament winding process for making high quality flywheel rims at low cost, and the rims made by the process, and also an apparatus for performing the process, continuously cures resin during the filament winding process. A lower winding process temperature is used along with a lower cure temperature and inherently higher toughness epoxy resin system allows for the rim to be wound continuously, using a conservative radial deposition rate of approximately ¼-½ inch per hour. Multiple types of fibers can be used in a rim where they best serve the strength and stiffness requirements of the structure. The winding temperature can be kept at approximately 55° C.-80° C., providing low thermal residual stresses. Aliphatic amine or ether amine curing agents with epoxy resin generally work well to reduce the winding temperature and allow low viscosity, but other resin systems that provide similar characteristics can be used.

Abstract: A flywheel uninterruptible power supply includes a solid steel cylindrical flywheel levitated for rotation about a vertical axis at tip speeds greater than 250 m/s on magnetic bearings in a low pressure housing. The cylindrical flywheel has a length L and a diameter D, wherein L/D≧1.0. A motor/generator attached to said flywheel accelerates the flywheel and maintains it at operating speed for storage of energy, and decelerates the flywheel for retrieval of the stored energy. The flywheel inertia section operates with a maximum stress of greater than 60% and less than 80% of the material yield stress when spinning at fully charged operating speed. The flywheel is constructed from steel with an ultimate strength greater 150 ksi and a toughness greater than 100 ksi (in){circumflex over ( )}1/2. The flywheel is a solid steel cylinder that is hardened to centerline structure throughout the axial thickness of the large diameter portion that is greater than 40% martensite.

Abstract: A vacuum management and regeneration apparatus and method for operating an energy storage flywheel system having a flywheel supported by a bearing system inside an evacuated chamber enclosed within a container. A motor/generator stores and retrieves energy by accelerating and decelerating the flywheel. A vacuum is maintained in the container with a vacuum level sufficient to reduce the aerodynamic drag on the flywheel, typically between 10−1 Torr to 10−3 Torr depending on the flywheel construction and its operating tip speed. The vacuum management system, including a vacuum pump and a timer, maintains the vacuum level in the container. The timer periodically enables operation of the vacuum pump, such as a mechanical vacuum pump or a getter pump, to reduce the pressure in the container.

Abstract: A flywheel system for storing and delivering on demand electrical energy includes a flywheel supported for high speed rotation on bearings in a vacuum enclosure, and a motor-generator for spinning the flywheel up to speed and then for converting the rotational inertia in the flywheel back to electrical power. The flywheel includes a solid steel hub and a rim having only two rings press-fit on the hub with an interference fit. The rings are filament wound construction made primarily from standard modulus carbon fiber/epoxy. The steel hub stores between 40% and 60% of the energy in the flywheel. The press-fitting of the rings on the hub creates radial interference pressure between the hub and each of the composite rings that is greater than 5 ksi when at rest. The outer carbon fiber/epoxy ring is radially thinner than the inner ring, and both the hub outer diameter and the inner diameter of the assembled composite rim are tapered with the same angle.

Abstract: A composite flywheel rotor includes a flywheel hub having tapered outer surface and an axis of rotation and a flywheel rim having an axis of rotation coinciding with the hub axis of rotation. The flywheel rim has multiple rings axially press-fit together to precompress the rings to form a composite flywheel rim. Each ring is made of approximately equal radial thickness and the entire non-dimensionalized radial thickness ratio of the assembled rim should be between approximately 0.38 to 0.48. The rim is optimally made up of four or five individual rings, each of which rings has tapered inner and outer diameters, preferably tapered at small angles to produce large radial forces when the rings are pressed onto each other and the hub by pressing axially, resulting in a high radial compressive preload in the assembled rim. A taper angle of 1-5° is suitable.

Abstract: A full levitation magnetic bearing system with passive magnetic bearings that affords increased radial stiffness and load capacity includes two passive permanent magnet magnetic bearings, one each located on each side of the center of mass of the rotor to be levitated. An active axial magnetic bearing provides control for stable levitation. The magnetic bearing system provides increased radial stiffness and load capacity by the reduction or elimination of the unstable tilting moments generated by the individual passive permanent magnet magnetic bearings. The bearings are constructed so that they are concave toward the center of the rotor, with a radius approximately equal to the distance between the magnetic bearing and the central point about which tilt rotation would tend to occur. The individual magnetic air gaps are preferably constructed to be perpendicular to the axis of rotation.

Abstract: A high-speed steel flywheel for a flywheel uninterruptible power is constructed by stacking several unpierced steel discs together. Each disc is heat treated prior to assembly. Thin axial thickness of each disc enables complete rapid quenching to attain a fully hardened condition and development of high tensile strength. The individual discs are machined or ground to shape and assembled to form an axially thicker flywheel capable of storing several kilowatts of energy or more. The discs are attached together by welding, brazing, soldiering, bonding or an interference assembly. The stacked disc configuration minimizes chances of catastrophic failure of the flywheel due to initiation of a crack in a single disc by restricting axial crack propagation to that single disc, and supporting the cracked disc by one or more adjacent discs until the flywheel can be safely decelerated.

Abstract: A composite flywheel rotor includes a flywheel hub having tapered outer surface and an axis of rotation and a flywheel rim having an axis of rotation coinciding with the hub axis of rotation. The flywheel rim has multiple rings axially press-fit together to precompress the rings to form a composite flywheel rim. Each ring is made of approximately equal radial thickness and the entire non-dimensionalized radial thickness ratio of the assembled rim should be between approximately 0.38 to 0.48. The rim is optimally made up of four or five individual rings, each of which rings has tapered inner and outer diameters, preferably tapered at small angles to produce large radial forces when the rings are pressed onto each other and the hub by pressing axially, resulting in a high radial compressive preload in the assembled rim. A taper angle of 1-5° is suitable.

Abstract: A flywheel uninterruptible power source has a charging system that uses a high frequency pulse width modulated inverter inside the motor drive with a very low frequency, line commutated converter that regulates by switching the alternating current from the utility power at frequencies under 200 Hz and 60 Hz. The placement of the motor power regulation switching is moved from the motor drive preferably to the input AC line current that provides power to charge the flywheel system. The switching is preferably done using natural commutation so that the devices are turned off when the current passes through zero for very low loss and device stresses. Preferable devices for switching include thyristors or triacs. The turn on switching can be accomplished using phase angle firing or in one embodiment zero cross over switching is employed to reduce harmonic distortion and radio frequency interference to the primary source.

Abstract: An in-situ curing filament winding process for making high quality flywheel rims at low cost, and the rims made by the process, and also an apparatus for performing the process, continuously cures resin during the filament winding process. A lower winding process temperature is used along with a lower cure temperature and inherently higher toughness epoxy resin system allows for the rim to be wound continuously, using a conservative radial deposition rate of approximately ¼-½ inch per hour. Multiple types of fibers can be used in a rim where they best serve the strength and stiffness requirements of the structure. The winding temperature can be kept at approximately 55° C.-80° C., providing low thermal residual stresses. Aliphatic amine or ether amine curing agents with epoxy resin generally work well to reduce the winding temperature and allow low viscosity, but other resin systems that provide similar characteristics can be used.

Abstract: A flywheel system for storing and delivering on demand electrical energy includes a flywheel supported for high speed rotation on bearings in a vacuum enclosure, and a motor-generator for spinning the flywheel up to speed and then for converting the rotational inertia in the flywheel back to electrical power. The flywheel includes a solid steel hub and a rim having only two rings press-fit on the hub with an interference fit. The rings are filament wound construction made primarily from standard modulus carbon fiber/epoxy. The steel hub stores between 40% and 60% of the energy in the flywheel. The press-fitting of the rings on the hub creates radial interference pressure between the hub and each of the composite rings that is greater than 5 ksi when at rest. The outer carbon fiber/epoxy ring is radially thinner than the inner ring, and both the hub outer diameter and the inner diameter of the assembled composite rim are tapered with the same angle.