Optimization Design And Performance Analysis Of Combined Submersible Permanent Magnet Motor

With the oilfield development entered the later period, water content of the oil wellproduced fluid is higher and higher. Sewage treatment increased the cost of production.Oil-water separation system can separate the oil and water in the well, Lift the raw petroleumto the wellhead, and inject the water directly into the other layer. In this paper, an oil-waterseparation system with direct drive combined submersible permanent magnet motor isdesigned. Submersible motor works in oil well casing pipe, the size of which is5.5inch. Sothe outer diameter of the motor is limited, the length of the motor needs to be larger to achievethe rated torque. The slenderness ratio of the motor can be50, and it is hard to processing andmaintenance. Combined submersible permanent magnet motor consists of several unit motor.Unit motor manufacture is relatively easy. Unit motor is connected by key joint. Inverterpower supply in parallel is adopted. The number of unit motors is flexible to match the needsof different load.The motor needs higher torque density for the limited space in the well, so the motortorque density is selected as the optimization goal. Slenderness ratio is selected as the mainoptimization variable. Consider other basic performance parameters as the constraint condition.Hybrid Taguchi Genetic Algorithm is applied into the optimal design of the motor, and theideal electromagnetic scheme is obtained. The program of Hybrid Taguchi Genetic Algorithmis compiled. Use the finite element software for validation, and modify calculating program.In order to balance the motor internal and external pressure, lubricating oil is injected intothe submersible motor. Crude oil flows also outside the enclosure, cooling conditions underthe well is complicated, so motor temperature rise calculation is needed. In this paper, thecombined submersible motor steady state losses are calculated, the equivalent coefficients ofthermal conductivity of motor parts are also calculated. The influence of heat dissipation onlubricating oil between stator and rotor, and the influence of heat dissipation on crude oiloutside the enclosure is analyzed. Three-dimensional steady temperature field simulationanalysis is carried out, and the three-dimensional steady state temperature distribution of themotor is obtained.The vibration of the motor will not only reduce the efficiency of the machine, also will accelerate the bearing wear, shorten the service life of bearing. Electromagnetic vibration isone of the main causes of motor vibration, which is the result of motor radial electromagneticwave. So the radial electromagnetic force wave of the motor is analyzed and the frequency andamplitude of the principle force which probably causing electromagnetic vibration is given.Magnetic solid coupling analysis is carried out on the motor, and the distribution of thevibration response is derived. Influence of motor structure parameters on the electromagneticvibration is analyzed, as to provide theoretical basis for reducing motor electromagneticvibration. The modal analysis of the submersible motor shaft is carried out; natural frequencieson different length of the motor shaft are obtained, providing the basis for determining thebiggest serial number of unit motors.At last, the load test, drag test, temperature rise test are carried out. Comparing the testresults and the calculation results, verifies that, the motor design method and the performanceanalysis method are scientific and accurate.