Resrarch On Cogging Torque And Temperature Of Low Speed And High Torque Permanent Magnet Synchronous Motor For Oilfield

The petroleum industry is an important energy backup for China's economic development and progress.With the development and progress of industrial technology,the exploitation of most oil fields in China has entered the middle and late stages.The drive system of traditional asynchronous motor acceleration and deceleration box has complex structure.When the motor runs at low speed,it needs more poles,and its efficiency and power factor will become very low,which can not realize the real large torque drive.The magnetic circuit of permanent magnet motor is relatively simple,compared with that of permanent magnet motor.The asynchronous motor has the advantages of low energy consumption and high efficiency,which is easy to use multi-pole structure to achieve low speed and large torque and directly drive load operation.In this dissertation,the cogging torque and temperature field of a 30 kW low speed and high torque permanent magnet synchronous motor are studied.Based on the basic theory of electromagnetic field in the motor,the finite element calculation model of low-speed and high-torque permanent magnet motor is established,the magnetic field distribution of the motor is studied,the harmonic content of radial air gap flux density is analyzed,the distribution characteristics of magnetic field in different regions of the motor stator core are analyzed,and several important electromagnetic parameters of the motor are simulated and processed,which lays the foundation for the later research.Aiming at the special cogging torque problem of permanent magnet motor,the generating principle of cogging torque is analyzed,the analytical formula of cogging torque is deduced from the angle of energy,and the influencing factors of cogging torque of low-speed and high-torque permanent magnet motor are studied.The motor models with different pole-slot combinations and pole-arc coefficients are simulated and calculated respectively.The results show that the cogging torque of low-speed and high-torque permanent magnet motor decreases with the increase of the minimum common multiple of the pole-slot number,and the optimal pole-arc coefficients which can weaken the cogging torque are determined.Based on the research of the magnetic field distribution inside the motor,the losses of low-speed and high-torque permanent magnet motors are calculated,and the core loss,stator winding copper loss and permanent magnet eddy current loss under different load conditions are studied,which provides a basis for solving the temperature field of the motor.A three-dimensional temperature field model of low-speed and high-torque permanent magnet motor is further established.The temperature field of the motor is simulated and calculated according to the calculated loss value.The temperature distribution characteristics of the stator winding,permanent magnet and stator core of the motor are analyzed respectively.Five typical locations are selected on the stator core with complex temperature changes to study the rules of temperature distribution along the axis of the motor.Law.It provides a basis for the design and research of the same type of motor.