Design And Research Of High-power Vehicle-mounted Permanent Magnet Drive Motor For Fracturing Pump

Fracturing is one of the important steps in the exploitation of shale gas.In recent years,the electric fracturing system has gradually replaced the traditional diesel fracturing system with advantages of high efficiency,low pollution,and high power density.In this paper,the permanent magnet drive motor for a 5500 HP type fracturing pump is taken as the research object.The design requirements and output characteristics of the motor are determined according to the characteristics of fracturing work and the load characteristics of fracturing pump.The motor is designed on the basis of the working characteristics and design requirements.The optimization design of the motor's high efficiency area is studied with emphasis.The specific work is as follows:Firstly,the overall structure of the electric fracturing system and the process of fracturing work are introduced.The design requirements of the permanent magnet drive motor for high-power on-board fracturing pumps is determined according to the characteristics of the fracturing work.The load characteristics of the fracturing pump is analyzed.The appropriate design power of the motor is selected on the basis of the load characteristics and technical parameters of the fracturing pump.The feasibility of motor design power selection is demonstrate through temperature rise analysis.Then,the permanent magnet drive motor for fracturing pump is designed on the basis of the working characteristics and design requirements.A suitable voltage level is selected according to the overall economy and practicability of the motor,frequency converter,and connecting cable.According to the fracturing working condition,a certain fault tolerance is required and the average load rate is low.The multi-phase motor is selected and the number of phases is determined.Suitable rotor structure is selected according to the requirement of high torque density.The effect of the ratio of length to diameter of the motor on the weight of the effective material and the amount of copper are analyzed.The main dimensions of the motor are determined by considering the weight of the effective material,the amount of copper,the moment of inertia of the motor and the height of the shaft.The air gap length of the motor is selected with the objective of minimizing the volume weight,without significantly affecting the harmonics of the motor.The number of motor poles,slots and the winding structure are determined with the goal of high power density and high efficiency.The permanent magnet material and dimensions are determined with the aim of increasing the utilization of permanent magnets as much as possible and ensuring motor performance.Finally,the way to maximize the high efficiency zone of the permanent magnet drive motor for fracturing pump and to make the high efficiency zone of the motor and the longterm continuous working zone of the fracturing pump overlap as much as possible is studied.Use of inhomogeneous air gap can significantly reduce the no-load air gap magnetic density harmonics,no-load back-EMF harmonics and core loss of the motor.The influence of different electromagnetic loads on the distribution of the motor's high efficiency zone is analyzed,and the appropriate electromagnetic load is selected.In order to improve the overall efficiency of the motor and take into account the limitations of the electromagnetic load of the motor,the volume and weight of the motor and the weak magnetic capacity,a suitable no-load back-EMF is selected.