Analysis on motor output characteristics and influencing factors of oscillating valve mud pulser

The oscillating valve pulser is a better choice for high-speed mud pulse transmission due to its capability of generating a higher frequency carrier. Great difficulties are brought to the research on the motor output characteristics due to the complex load moment and its numerous influencing factors during the operation. Using the dynamic balance equation for the motor operating in underground coal mine, the position angle and output current data of the oscillating valve motor under the Max Torque per Ampere (MTPA) control mode were obtained by measurement in the water cycle experiment. Then, the output torque and output power of the motor operating in underground coal mine was calculated, and its influencing factors were comprehensively analyzed. The research results show that under the influence of inertia torque, elastic torque and dynamic hydraulic torque, the output torque of the motor has different characteristics in different working frequency bands. Specifically, the variation amplitude of motor output torque decreases but the output power increases slowly with the increasing carrier frequency in the low frequency band. Besides, the output torque and output power of the motor are relatively stable in the intermediate frequency band, with little variation. However, both of the output torque and output power of motor increase rapidly with the increasing frequency in the high frequency band. The motor output in the high frequency band can be reduced by increasing the stiffness coefficient of the torsional spring and decreasing the moment of inertia of oscillating swing valve rotor shaft, so as to ensure that the motor can control the oscillating valve under rated torque and rated power to achieve rapid oscillating at high frequency in the well, thereby generating the mud pulse pressure waveform under stable and high carrier frequency to achieve the purpose of high frequency carrier, which guarantees the high speed transmission of measurement while drilling (MWD) data.