Theories And Experiment Research On Electric Motor Of Pumping Unit

Rod pumping is the most widespread traditional extraction method at present and holds great proportion at home and abroad. Its principle is to pumping oil through the up and down movement of oil pump plunger dragged by the sucker rod. The pumping unit drags sucker rod and oil column to move upward during up-stroke and the load is comparatively large. On the other hand, the pumping unit is dragged by sucker rod to move downward during down-stroke and the load is small. Therefore, the load fluctuation of the pumping unit is large and it needs to be balanced. But the effect of present commonly used mechanical equilibrium way is not very well, existing great torque fluctuation and negative torque. So, the torque fluctuation of pumping unit is large and has overspeed phenomenon, causing low efficiency of electrical motor.Because of the reason that electrical motor's rotate speed can be reduced and the operating efficiency can be obtained by increasing the moment of inertia. From the point of changing the motor's inertia, the effect to the motor's efficiency by increasing the motor's inertia has been researched in both theoretical side and experimental side.According to the structural features of the pumping unit, the movement and mechanical analysis mathematical model are established, the variation relationship of speed and acceleration of the suspending point with the crank angle are computed. Taking the pumping unit's crank as the equivalent rotation component, the equivalent rotation inertia of pumping unit in one cycle is calculated. Functions have been established based on the relationship between motor's torque and rotation speed. Using the differential method, the variational situations of the torque and rotation speed around the increasing of the rotation inertia are solved. And according to the relationship curves between motor's torque and rotation speed, the influence to the motor's efficiency by increasing the rotation inertia has been researched.Based on the result of theoretical analysis, the design proposal of the pumping unit's electrical motor energy-balanced equipment with the principle of increasing the rotation inertia by flywheel is proposed and two kinds of flywheel balancing equipments have been developed. The indoor simulation test indicates that along with the change of pumping unit's load and frequency of stroke, the balancing effect are different. The comparative test of four oil pumps on the spot shows that pumping unit balance equipment No. CNB-II has ideal energy balancing effect with average combined electrical saving rate 17.5% and the maximum power reduces 29%.