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4180results about "Synchronous machines with stationary armatures and rotating magnets" patented technology

Method and apparatus for controlling brushless DC motors in implantable medical devices

Methods and apparatus for controlling a polyphase motor in implantable medical device applications are provided. In one embodiment, the polyphase motor is a brushless DC motor. The back emf of a selected phase of the motor is sampled while a drive voltage of the selected phase is substantially zero. Various embodiments utilize sinusoidal or trapezoidal drive voltages. The sampled back emf provides an error signal indicative of the positional error of the rotor. In one embodiment, the sampled back emf is normalized with respect to a commanded angular velocity of the rotor to provide an error signal proportional only to the positional error of the motor rotor. The error signal is provided as feedback to control a frequency of the drive voltage. A speed control generates a speed control signal corresponding to a difference between a commanded angular velocity and an angular velocity inferred from the frequency of the drive voltage. The speed control signal is provided as feedback to control an amplitude of the drive voltage. In one embodiment, an apparatus includes a brushless DC motor and a commutation control. The commutation control provides a commutation control signal for a selected phase of the motor in accordance with a sampled back electromotive force (emf) of that phase. The back emf of the phase is sampled only while the corresponding drive voltage for the selected phase is substantially zero, wherein a frequency of a drive voltage of the motor is varied in accordance with the commutation control signal.

Light weight rotor and stator with multiple coil windings in thermal contact

A lightweight engine-driven generator set including a stator having at least first and second windings (preferably three-phase) and a rotor having a soft magnetic core and a plurality of high energy product permanent magnets, separated by consequence poles, disposed proximate the stator such that relative motion of the rotor and stator causes magnetic flux from the rotor to interact with and induce current in the stator windings. The first winding includes a predetermined number of turns corresponding to a first predetermined voltage output; and the second winding includes a predetermined number of turns corresponding to a second predetermined voltage output, the respective windings being grouped together as a unit and wound about the core such that the respective winding coils are wound in continuous close thermal contact with each other. The first winding generates a relatively high voltage, low amperage signal, and the second winding generates a relatively low voltage, high amperage signal; and a switch provides for selection of the desired output. Preferably the rotor is a hollow cylinder mounted on the engine shaft for rotation about the stator and such that the proper gap distance between rotor and stator is maintained during rotation of the rotor without bearings external to the engine. The low voltage, high amperage winding (or winding group) may be tapped to provide a selectable voltage output. Suitable rectifiers and inverters may be provided to effect selective DC and AC output signals.

Motor generator including interconnected stators and stator laminations

An axial field motor/generator having a rotor that includes at least three annular discs magnetized to provide multiple sector-shaped poles. Each sector has a polarity opposite that of an adjacent sector, and each sector is polarized through the thickness of the disc. The poles of each magnet are aligned with opposite poles of each adjacent magnet. Metal members adjacent the outermost two magnets contain the flux. The motor/generator also has a stator that includes a stator assembly between each two adjacent magnets. Each stator assembly includes one or more conductors or windings. Although the conductors may be formed of wire having a round, uniform cross-section, they may alternatively be formed of conductors having a tapered cross-section that corresponds to the taper of the sectors in order to maximize the density of the conductor in the gap between axially adjacent poles. The conductors may also alternatively be formed of traces in a printed circuit, which may have one or more layers. Each stator assembly may be removably connectable to another stator assembly to provide modularity in manufacturing and to facilitate selection of the voltage at which the motor/generator is to operate. Electrical contacts, such as pins extending from the casing, may removably connect the conductors of adjacent stator assemblies. A magnet may be dynamically balanced on the shaft by hardening a thin ring of cross-linked resin between the magnet and the shaft while the shaft is spun, using ultraviolet light to polymerize the resin.
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