Design of downhole turbine alternator for measurement while drilling and its performance analysis

The design principles and constraint conditions to design the turbine with measurement while drilling(MWD) technique were proposed on the basis of the classical two-dimensional design theory of turbine.A mathematic model of alternator was built for analyzing the electromagnetic characteristics with vector analysis method.The internal impedance model of alternator was used to analyze the relation between the exterior voltage characteristics or voltage regulation rate and the armature reactance with numerical calculation.The research results demonstrated that the internal impedance of alternator had both current and power factor angle feedback characteristics,which improved the voltage regulation rate to a certain extent.Additionally,an optimal variation range of the armature reactance,in which there was less voltage regulation rate,was put forward.The characteristic parameters of the MWD turbine were computed and analyzed based on the experimental data of the downhole MWD turbine alternator,the theoretical analysis of the alternator electromagnetic characteristics and turbine design theory.