| 摘要 |
A measurement-while-drilling mud pulser and a method for controlling a measurement-while--drilling mud pulser. The mud pulser includes a brushless DC motor that hydraulically controls a main restrictor valve that the mud pulser uses to generate mud pulses. Back EMF signals generated in the stator windings of the brushless DC motor are monitored and are used as the basis for commutating the brushless DC motor. The phase transitions in the back EMF signals can be used in governing stator energizations of the brushless DC motor to thereby govern its rotation.. Relying on back EMF signals for commutation allows commutation to be performed without Hall Effect or other kinds of sensors, which can thereby reduce cost of the mud pulser and further increase reliability of the mud pulser by decreasing the number of high pressure sealings needed due to wires from Hall effect sensors, which are prone to develop leaks.
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