Calculation And Analysis Of Mechanical Loss And Electromagnetic Parameter In Magnetic Isolated Segment For Submersible Motor

As the drive part of submersible pump set, submersible motor is a kind of vertical three-phase asynchronous motor, working in very special situation , the bottom of oil well , thousands of meters under ground. The stator and rotor are slender and separated; the gap is full of special lube oil. The rotor includes several cage-type rotor units; there is bearing between every two units; corresponding to the rotor bearing, there are magnetic isolated segments in the stator core. Obviously, common calculation method for general three-phase asynchronous motor is not completely suitable for submersible motor, but till now there is not a design method inside or outside of China that can perfectly consider the special structure and working situation. Traditional design method for general asynchronous motor is used in most occasions, the error is big and the practical accuracy requirement is hard to be satisfied in engineering practice.According to nowadays international study status of submersible motor, the problems exist in present design method are analyzed. For the pivotal technology problems in design, combined with its structure character, electromagnetic field theory, liquid theory and etc. are applied to thoroughly and concretely study the design method of submersible motor, and the high accuracy design method is formed.When the gap is full of special lube oil, the influence to the mechanical loss of the submersible motor is studied; the oil friction loss formed by lube oil with rotor as the motor revolves with high speed is analyzed emphatically; hydromechanical theory and empirical formula for friction loss of thrust bearing shoe, static block and rotor bearing under working condition of the motor are adopted, the accurate calculation method of mechanical loss of submersible motor is acquired, and the effectiveness of this method has been proved by experiments and calculations of example.The leak magnet influence of magnetic isolated segment to the performance parameter of submersible motor is analyzed, and the concept of leakage reactance in magnetic isolated segment is defined. The 3D FEM model of magnetic isolated segment is set up, and the leakage reactance is achieved by solving the stored energy of the model. It is proved by experiment that the influence of leakage reactance in magnetic isolated segment to the performance parameter of the motor is clear and must be considered in the design of the motor.Meanwhile, under the premise of guaranteeing the calculation result is right, the nonlinearity of magnetic conductivity of the stator core and rotor core is simplified and the additive loss in rotor bearing is calculated by FEM model. For the submersible motor with steel outer space rotor bearing, the influence of additive loss to the efficiency of motor is analyzed. It is studied that, when new type alloy material with big resistivity and without magnetic permeability is used to produce the outer space rotor bearing, the loss is reduced obviously and the influence to the motor efficiency can be ignored.As the characteristic of submersible motor with small diameter and big length that traditional skewed slot is hard to be adopted. In this dissertation, the angle between the line of rotor slot centre and the line of key centre is designed with some special degree. Front and back of iron sheet are used separately when making the rotor iron core, and different rotor cores are formed and installed at the two sides of the rotor bearing, so the function of skewed slot is attained for the whole motor.Two sets of simulated experiment simulated model are developed, not only the studied problems are considered when designing the sample motor, but also the structure shall be easy to be manufactured. For the two sets of model, the same electro-magnetic design scheme but different structure designs are used. The sample has two sections, output power 6kW, voltage 290V, the length of the whole assembled motor is 1.6m. For one sample, magnetic isolated segment and rotor bearing are installed at the subsection of the stator and rotor; for the other one, no rotor bearing is installed at the subsection but circlip to fix.After the samples are completed, the additive loss in rotor bearing and mechanical loss are theoretically calculated by the method stated above. The related experiment equipments are purchased and the experiments are carried out for the two samples, two groups of test data are analyzed and the experimental values of additive loss in rotor bearing and mechanical loss are acquired. At last, comparing the calculation value with the experimental value of the related parameters, it shows that, the calculation result which considers the parameters raised in this dissertation can reach the experimental values closer. The correctness of the study content is proved directly. The theoretical calculation method is testified with very high accuracy by indirect experiment of leakage reactance in magnetic isolated segment of samples.Based on the reserch above, the universality research of leakage reactance in magnetic isolated segment of submersible motor is carried out. It is studied profoundly that how the leakage reactance in magnetic isolated segment changes with the motor power rate, the width of magnetic isolated segment, the quantity of magnetic isolated segment and the relative position of rotor bearing and the near two section of rotors. For each power rate of now available submersible motor, large amount of calculations of leakage reactance in magnetic isolated segment under different width of magnetic isolated segment have been done, and the leakage reactance curve group of submersible motor is achieved, which will provide reliable foundation for submersible motor design in future.Research achievement of this dissertation provided the reference for the design of submersible motor. Considering batch production of the product in future, the universal property, flexibility and reliability design of the motor structure is provided. The provided method and study achievement not only have theoretical significance but also very high practical value.Submersible Motor.