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10256results 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.
Owner:HEARTWARE INC

Disk drive comprising a spindle motor having a windings shield for reduced disk voltage coupling

A disk drive is disclosed comprising a disk, a head actuated over a surface of the disk, and a spindle motor for rotating the disk. The spindle motor comprises a ring-shaped stator having a plurality of stator teeth each wound with a winding. The spindle motor further comprises a hub having a plurality of magnets for interacting with the stator teeth to rotate the hub about the shaft when the windings are energized. A ring-shaped shield is disposed in a vertical gap between the windings and the hub to reduce a voltage coupled from the windings to the surface of the disk.
Owner:WESTERN DIGITAL TECH INC

Internal thermal management for motor driven machinery

A motor driven assembly includes a motor having a motor shaft mounted for rotation about a rotational axis and a rotor radially located about the shaft. The motor drives a compressor that receives air from the motor, compresses the air, and circulates the compressed air to a space. The motor includes a first cooling flow passage and a second cooling flow passage that each receive air to provide internal cooling of the motor. A portion of the air compressed in the compressor is diverted from the compressor to a heat exchanger. The heat exchanger cools the compressed air from before the air circulates into the first cooling flow passage to cool the motor. The second cooling flow passage receives air from the environment surrounding the motor driven assembly to further cool the motor.
Owner:HAMILTON SUNDSTRAND CORP
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