Low-speed Permanent-magnet Submersible Motor’s Design And Structural Analysis

Electric submersible screw pump(ESP)technology is more intelligent than the traditional mechanical oil production technology,the application of ESP has simplified the oil extraction equipment,meanwhile,the application scope of ESP has been extended and it’s especially suitable for shallow heavy oil field mining operations.The ESP is powered by submersible motor.In order to improve the recovery factor of heavy oil and the work efficiency of the electric submersible screw pump,and the screw pump can be direct drived by the submersible motor,the main purpose of this paper is to design a high torque submersible permanent magnet synchronous motor with low speed.Compared with the conventional induction motor,the submersible motor belongs to unconventional motor.As the design method of the submersible motor is different from the conventional motor,the electromagnetic formula is derived on the base of the basic electromagnetic relation which is for permanent magnet synchronous motor at the first of the paper,besides,some problems which should be paid attention in the general designing of low speed submersible motor is analyzed,and provides methods to solve these problems,finally,a relevant finite element simulation of the design structure is given.Due to the limitation of the size of wellheads,the submersible motor is a slender structure.In order to meet the low speed and high torque performance of submersible motor,the fractional slot winding is adopted in this paper.For the threading manufacture method of submersible motor is more complicated,in order to increase the filling rate of submersible motor and limit the quantity of conductors in per slot,the parallel groove structure is adopted by stator.In this paper,a composite analysis of two motors designed with different combinations of slots and poles is obtained,and the motor with better performance is selected as the design structure at the beginning.To improve the performance of the motor,the researcher had made a partly improvement of original part structure of the motor in this paper,and give the changes and performance analysis of permanent magnet torque under different eccentricity,which analyzed the influence of permanent magnet motor change on the air gap flux density and eddy loss.In order to reduce the motor loss and improve the efficiency of the motor,the gap density of the motor is improved by changing the slot size,so as to reduce the motor loss and improve the efficiency.Finally,the optimal scheme of the motor is determined by the above structure.Finally,the finite element simulation of the final motor design on Ansoft Maxwell verified the rationality of the optimal scheme.