Optimization Design And Performance Analysis Of Combined Direct-driven Submersible Screw Pump Permanent Magnet Motor

Compared with traditional submersible motor,direct-driven submersible screw pump permanent magnet motor with unit-combination has many advantages,such as higher efficiency,higher power factor,smaller size and easier to manufacture and so on.Restricted by outer dimension,the only method to guarantee enough power is to increase the axial length,which leads to its ultra-thin structure that increases the difficulty to manufacture and maintain.The unit-combination structure of motor this paper studies makes it possible match different numbers of unit well with different load,which can reduce the cost of manufacturing a lot.To increase the axial utilization and reduce the broken risk of lifting,the form of unit-combination structure has been improved in this paper.And the motor torque density should be improved in view of the size restriction.Aiming at improving the torque density,the finite element method and taguchi method has been applied in this paper.Structure sizes related to torque density has been optimized by the two methods,and the torque density after optimized has been analyzed.Motor of proper fraction slot with concentrated winding(PFCW)has high torque density and fault tolerance,but it can have a lot of winding magneto motive force harmonics at the same time which will increase the rotor loss and torque ripple.The submersible motor this paper studies uses PFCW.Distribution of harmonics content of winding magneto motive force is given out by the magneto motive force composite method.And double-winding method is applied in this paper to reduce harmonics.Harmonics content after reduced is analyzed by finite element method.To further validate the effect of reducing harmonics,winding factor of each harmonic is calculated in this paper.Problem of torque ripple is serious when submersible motor operates with unit-combination structure.The torque ripple caused by slender shaft torsion deformation and unit-combination operating is analyzed in this paper.And method of minimizing the torque ripple by changing the relative position of adjacent unit motor stator is given out and verified.At last,prototype experiment is described in this paper.The effectiveness of method of minimizing the torque ripple and advantages of direct-driven submersible screw pump permanent magnet motor with unit-combination compared with traditional submersible motor are proved in the experiment.