Abstract: A magnetic bearing system for support of a body, such as an energy storage flywheel, for rotational about a substantially vertical axis of rotation through its center of mass. The bearing system includes a rotating portion and a stationary portion on each axial side of the center of mass. Two or more concentric axially magnetized ring poles on an axial surface of the rotating body are constructed of multiple individual permanent magnet pieces, arranged in rigs inside a containment cup in the end face of the rotor with radially adjacent rings having alternating magnetic polarities. On the stationary portion, two or more concentric axially magnetized pole rings of permanent magnet material cooperate with the rotating ring magnets to produce both an axial attractive force and a radial centering force.

Abstract: A device for preventing power interruptions to a DC bus includes a flywheel supported on bearings for rotation inside a chamber having a drag reducing atmosphere within a container. During charging, the flywheel is driven by an integral brushless permanent magnet excited motor/generator for storing energy, and during retrieval of the stored energy, the flywheel drives and is decelerated by the same motor generator. A closed loop operated synchronous inverter delivers synchronous electrical power to the armature coils of the motor/generator for accelerating the motor/generator. A rectifier connects the armature coils of the motor/generator to the DC bus. Upon an interruption of primary utility power, the motor/generator supplies unregulated voltage power to the DC bus through the rectifier, and the voltage of the unregulated voltage power to the DC bus falls as the flywheel slows during discharge of useable energy from the flywheel through the motor/generator to the DC bus.

Abstract: A flywheel energy storage system that allows high-speed operation with use of mechanical rolling element bearings for radial support of a vertical axis flywheel while they allow it to be mechanically free or unrestrained in the axial direction. Magnetic bearings are used to carry the flywheel weight axially. The axial unconstraint by the mechanical bearings allows the flywheel to freely grow or shrink in axial length from Poisson Effect contraction that occurs when rotating to very high speeds and stress levels as well as from thermal expansions from motor/generator heating or other sources, and also insures that the magnetic bearing carries all of the flywheel weight, thus greatly extending the life of the mechanical bearings. Radially compliant elements mechanically in series with the mechanical bearings provide for a lower radial stiffness, which allows the flywheel to traverse its rigid body resonance at a low speed.

Abstract: A flywheel energy storage system includes an energy storage flywheel supported on a bearing system for rotation about a substantially vertical axis inside in an evacuated chamber enclosed within a sealed container. A motor and a generator accelerates and decelerates the flywheel for storing and retrieving energy. A tilt sensor detects if the orientation of the axis of rotation is outside of tolerance limits from vertical and triggers a signal to signal appropriate system functions to protect the system from damage.

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 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 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: 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 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 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.