Analysis On Unbalanced Magnetic Forces And Shaft Deflection Of Low Speed Permanent Magnet Synchronous Submersible Motor

Currently,the proportion of heavy oil wells in oil production is increasing.A kind of lower speed screw pump is used to extract heavy oil.Due to the diameter limitation of the conventional submersible motor,the number of stator slots should not be chosen too much,which makes submersible motor difficult to increase the number of poles and reduce the speed through electromagnetic design.Therefore,it is necessary to use a matching reducer,which causes problems such as low reliability and low system efficiency of the oil production system.Permanent magnet submersible motor(PMSM)with fractional slot concentrated windings(FSCW)has received more and more attention in the production of heavy oil wells,due to PMSM with FSCW can achieve the purpose of more poles by fewer slots through a reasonable electromagnetic design scheme.Due to the use of sliding bearings,the slender low-speed PMSM has inherent defect of uneven air gap,leads to large unbalanced magnetic forces(UMF),which causes problems such as vibration and bearing eccentric wear.This thesis studies the electromagnetic design and mechanical structure design of a PMSM with FSCW.The main work of this thesis is as follows:Firstly,compare the effects of different pole-slot combinations on the winding coefficient and cogging torque,and choose the best solution.A PMSM is designed according to the solution.The rationality of the solution was verified by finite element method(FEM).Secondly,through theoretical analysis and research,it is concluded that the eccentricity of the rotor will cause a UMF(EUMF),and the asymmetry of the stator topology will cause the pole-slot combinations will cause a UMF(PSUMF)as well.This thesis has derived three expressions of EUMF,PSUMF and UMF.The expression of the traditional deflection calculation is improved.This improvement provides theoretical support for the structural design of PMSM with FSCW.Finally,the problem of deflection measurement is studied,and a method is proposed to analyze the problem of deflection by converting the problem of shaft deflection into the problem of stator vibration.The FEM is used to simulate the electromagnetic vibration of the stator caused by the UMF of the motor model when the deflection is a critical value.Determine whether the deflection is within a reasonable range by measuring the stator vibration.