Communications – electrical: acoustic wave systems and devices – Wellbore telemetering
Patent
1992-08-21
1993-08-17
Eldred, J. Woodrow
Communications, electrical: acoustic wave systems and devices
Wellbore telemetering
367 83, 367 84, 175 40, 175 45, H04R 900
Patent
active
052375404
ABSTRACT:
A LWD tool is disclosed comprising, an encoder for generating a signal in the borehole fluid flowing therethrough, a brushless DC motor coupled to the encoder, a position sensor coupled to the motor for sensing the rotational position thereof, motor drive electronics coupled to motor for driving the motor, a microprocessor coupled to the position sensor and to the drive electronics for controlling the drive signals to the motor based on the actual and desired positions of the motor, and a magnetic positioner which is coupled to one of the drive shafts of the system. By controlling the drive signal to the motor, the speed of the motor is controlled, thus effecting changes in frequency and/or phase of the signal. The magnetic positioner, includes inner S magnets extending in a first arc, inner N magnets extending in a second arc, outer S magnets extending in a third arc, and outer N magnets extending in a fourth arc, where the inner magnets rotate with the drive shaft. The magnetic positioner is provided to force the rotor of the encoder into an open position relative to the stator in the case of loss of power. The magnetic positioner is also used to aid in the decelaration and acceleration of the encoder during phase shifting.
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Eldred J. Woodrow
Gordon David P.
Kanak Wayne I.
Ryberg John J.
Schlumberger Technology Corporation
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