Research On Rotor Friction Loss Of Permanent Magnet Synchronous Motor For Submersible Pump

At present,asynchronous motors are widely used in submersible pumps,but their efficiency is low,resulting in large volume of the pump and high power consumption.Compared with asynchronous motors,permanent magnet synchronous motors have the advantages of large power factor,high efficiency,high power density,simple structure,and easy maintenance.Therefore,using a permanent magnet synchronous motors as the driving device of the submersible pumps can reduce the volume of the unit,which can improve the efficiency of the motor,and respond to the national call for "energy saving and emission reduction".As a kind of submersible motor,the permanent magnet synchronous motor for submersible pumps is immersed in water wells for many years to work,so the design of permanent magnet synchronous motors for submersible pumps is different from that of ordinary dry motors.The rotor rotates in water,and the bearing of the motor is also a water-lubricated sliding bearing,which leads to a large loss of the rotor.To accurately design the motor,it is necessary to accurately calculate the friction loss of the motor rotor when it runs in water.In this thesis,taking the general permanent magnet synchronous motor for submersible pump as an example,the law of rotor friction loss and bearing friction loss of submersible motor is obtained,and then the calculation method is improved to make the calculation of friction loss of submersible motor more accurate.Then,on this basis,a permanent magnet synchronous motor for submersible pump is designed,and the electromagnetic calculation and temperature field simulation of the motor are carried out.The main contents include the following three aspects:Firstly,the water friction loss of the permanent magnet synchronous motor rotor for the submersible pump is calculated.The interior of the permanent magnet synchronous motor for submersible pumps is filled with water.During the rotation of the motor,the surface of the rotor will produce severe friction with water,resulting in loss.Therefore,the friction loss of water generated by the permanent magnet synchronous motor for submersible pumps accounts for a large part of the total loss.In this thesis,the fluid friction loss is calculated by the analytical method,and then the water friction loss of the rotor is calculated by Fluent based on the theory of heat transfer and tribology.The factors affecting the friction loss of the permanent magnet synchronous motor for submersible pumps are analyzed,and the rules are found.Secondly,the friction loss of the permanent magnet synchronous motor for submersible pumps is not only reflected in the rotor,but also the friction loss of the thrust bearing at the bottom of the motor.This thesis studies the calculation method of the friction loss of the stepped thrust bearing,according to the principle of fluid lubrication,Fluent software is used to calculate the friction loss of the thrust bearing,as well as the pressure peak and the bearing capacity of the stepped thrust bearing.And the law of bearing capacity and friction loss under different influence factors is analyzed.Finally,a 30 k W permanent magnet synchronous motor for submersible pump is designed,and the parameters such as the winding distribution,the number of magnetic pole pairs,the number of coil turns,and the size of the motor are calculated in the actual design process.And using electromagnetic software to carry out two-dimensional modeling and simulation of permanent magnet synchronous motor to analyze the performance of the motor.At the same time,modeling software is used to build a three-dimensional model of the motor,and finite element software is used to simulate the temperature field.Finally,the prototype experiment is used to verify that the designed motor meets the requirements.