Abstract: The drill string axial vibration attenuator (10) is installed in the bottom hole assembly (BHA) of a drill string to attenuate axial and torsional vibrations of the drill string. The vibration attenuator (10) includes a massive elongate stabilizer (14) installed in a sealed chamber (12) that is, in turn, rigidly installed within the BHA of the drill string. Clearance between the inner wall of the chamber (12) and the stabilizer (14) is provided to preclude frictional interference therebetween. The stabilizer mass (14) is supported from below by a compression spring (18) and a shock absorber or damper (24) at the top to allow movement of the mass (14). The stabilizer (14) substantially reduces or eliminates axial and coupled torsional vibration of the drill string when the mass of the stabilizer (14), the rate of the spring, and the damper stiffness are properly configured.

Abstract: The direct current (DC) side fault isolator for high voltage direct current (HVDC) converters (10) includes a first set of double thyristor switches (12) connected across the line-to-line voltage terminals between first and second phases of alternating current (AC) terminals of a HVDC converter (14), and a second set of double thyristor switches (12) connected across the line-to-line voltage between the second phase and a third phase of the AC terminals of the HVDC converter (14). In use, the first and second sets of double thyristor switches (12) separate the HVDC converter (10) from an external power grid (18) during direct current (DC) side faults by turning on these thyristors (12).

Abstract: The method of converting high voltage AC lines into bipolar high voltage DC systems makes use of the three transmission lines (referred to as the positive pole, the negative pole, and the modulating pole) in an existing high voltage AC system as transmission lines in a bipolar high voltage DC system. When current from the power source is up to the thermal current limit of the transmission lines, the transmission lines operate in two-wire mode, where current is delivered in the positive pole and returned in the negative pole, the modulating pole being open. When power source current exceeds the thermal current limit, operation is in three-wire mode, alternating for predetermined periods between parallel configuration of the positive pole and the modulating pole to divide current for delivery to the load, and parallel configuration of the negative pole and the modulating pole, dividing the return current.

Abstract: The direct current (DC) side fault isolator for high voltage direct current (HVDC) converters (10) includes a first set of double thyristor switches (12) connected across the line-to-line voltage terminals between first and second phases of alternating current (AC) terminals of a HVDC converter (14), and a second set of double thyristor switches (12) connected across the line-to-line voltage between the second phase and a third phase of the AC terminals of the HVDC converter (14). In use, the first and second sets of double thyristor switches (12) separate the HVDC converter (10) from an external power grid (18) during direct current (DC) side faults by turning on these thyristors (12).

Abstract: A telebending tool for conveying a logging tool into a wellbore includes a tool body having a central axis. In addition, the tool also includes a cam housing coupled to the tool body and a nose moveably coupled to the tool body through a pivoting member. Further, the telebending tool includes a compression spring positioned between the nose and the pivoting member, and a camming arm coupled to the nose. The camming arm extends coaxially through the pivoting member to selectively engage a cam pathway of the cam housing. The nose has a first position with a central axis of the nose coaxially aligned with the central axis of the body and a second position with the central axis of the nose oriented at an angle less than 180° relative to the central axis of the body.

Abstract: An apparatus for voltage balancing parallel arranged direct current (DC) voltage source strings in a power generation system includes a string voltage balancing circuit having reverse blocking switches to control a current flow and an output voltage of the DC voltage source strings. Capacitors are connected to a corresponding reverse blocking switch and in series with a corresponding one of the plurality of DC voltage source strings to construct a voltage difference for a corresponding one of the plurality DC voltage source strings. The string voltage balancing circuit adjusts an output voltage of the DC voltage source strings by controlling a current flowing in the plurality of DC voltage source strings to adjust a voltage constructed across corresponding ones of the capacitors to balance the output voltage for the DC voltage source strings to be substantially the same output voltage. Current balancing using differential power processing is also provided.

Abstract: An apparatus for voltage balancing parallel arranged direct current (DC) voltage source strings in a power generation system includes a string voltage balancing circuit having reverse blocking switches to control a current flow and an output voltage of the DC voltage source strings. Capacitors are connected to a corresponding reverse blocking switch and in series with a corresponding one of the plurality of DC voltage source strings to construct a voltage difference for a corresponding one of the plurality DC voltage source strings. The string voltage balancing circuit adjusts an output voltage of the DC voltage source strings by controlling a current flowing in the plurality of DC voltage source strings to adjust a voltage constructed across corresponding ones of the capacitors to balance the output voltage for the DC voltage source strings to be substantially the same output voltage. Current balancing using differential power processing is also provided.

Abstract: A telebending tool for conveying a logging tool into a wellbore includes a tool body configured to couple to a logging tool, wherein the body has a central axis. The telebending tool also includes a cam housing coupled to the tool body and having a cam pathway and a nose moveably coupled to the tool body through a pivoting member, wherein the nose has a central axis. The telebending tool further includes a compression spring positioned between the nose and the pivoting member and a camming arm coupled to the nose. The camming arm extends coaxially through the pivoting member to selectively engage the cam pathway of the cam housing. The nose has a first position with the central axis of the nose coaxially aligned with the central axis of the body and a second position with the central axis of the nose oriented at an angle less than 180° relative to the central axis of the body.

Abstract: A commutation apparatus drives a brushless motor having a stator equipped with a plurality of coils and a rotor. The commutation apparatus comprises a rotatable commutator shaft, two or more conducting rings carried discretely about the shaft, and two or more conducting segments carried discretely about the shaft at staggered positions along or near a plane perpendicularly intersecting the shaft. Each conducting segment is electrically connected to one of the conducting rings. Two or more electrical source contacts are provided for rotatably connecting a power supply across pairs of the conducting rings. A plurality of electrical load contacts is further provided for sequentially, rotatably connecting the conducting segments to discrete coils of the brushless motor.

Abstract: A commutation apparatus drives a brushless motor having a stator equipped with a plurality of coils and a rotor. The commutation apparatus comprises a rotatable commutator shaft, two or more conducting rings carried discretely about the shaft, and two or more conducting segments carried discretely about the shaft at staggered positions along or near a plane perpendicularly intersecting the shaft. Each conducting segment is electrically connected to one of the conducting rings. Two or more electrical source contacts are provided for rotatably connecting a power supply across pairs of the conducting rings. A plurality of electrical load contacts is further provided for sequentially, rotatably connecting the conducting segments to discrete coils of the brushless motor.

Abstract: A commutation apparatus drives a brushless motor having a stator equipped with a plurality of coils and a rotor. The commutation apparatus comprises a rotatable commutator shaft, two or more conducting rings carried discretely about the shaft, and two or more conducting segments carried discretely about the shaft at staggered positions along or near a plane perpendicularly intersecting the shaft. Each conducting segment is electrically connected to one of the conducting rings. Two or more electrical source contacts are provided for rotatably connecting a power supply across pairs of the conducting rings. A plurality of electrical load contacts is further provided for sequentially, rotatably connecting the conducting segments to discrete coils of the brushless motor.

Abstract: A commutation apparatus drives a brushless motor having a stator equipped with a plurality of coils and a rotor. The commutation apparatus comprises a rotatable commutator shaft, two or more conducting rings carried discretely about the shaft, and two or more conducting segments carried discretely about the shaft at staggered positions along or near a plane perpendicularly intersecting the shaft. Each conducting segment is electrically connected to one of the conducting rings. Two or more electrical source contacts are provided for rotatably connecting a power supply across pairs of the conducting rings. A plurality of electrical load contacts is further provided for sequentially, rotatably connecting the conducting segments to discrete coils of the brushless motor.