0681090-A2 is referenced by 37 patents and cites 7 patents.

An integrated modulator and turbine-generator includes a turbine impeller which is directly coupled by a drive shaft to a modulator rotor downstream from the impeller. The modulator rotor is further coupled by a drive shaft and a gear train to a three phase alternator downstream of the modulator rotor. The modulator stator blades are arranged downstream of and adjacent to the modulator rotor and the alternator is provided with a Hall effect tachometer. The turbine impeller directly drives the modulator rotor and the alternator generates power. The speed of rotation of the modulator rotor is adjusted by reference to the speed of rotation of the alternator as indicated by the tachometer and to a reference frequency.; A control circuit including an electromagnetic braking circuit coupled to the tachometer and the stator windings of the alternator stabilizes the alternator speed and thus the rotor speed and modulates the rotor to obtain the desired frequency of the mudborne pressure wave by selectively shorting the stator windings of the alternator. During periods when braking is not applied, the alternator generates power for control and sensor electronics.

Title
Measurement while drilling tool.
Application Number
EP19950302658 19950421
Publication Number
0681090 (A2)
Application Date
April 21, 1995
Publication Date
November 8, 1995
Inventor
Masak Peter
US
Lerner Daniel
US
Assignee
Schlumberger Services Petrol
FR
Anadrill Int
PA
IPC
E21B 47/00
E21B 47/18
E21B 47/12
E21B 41/00
E21B 47/18
E21B 41/00
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