Analysis Of Operating Characteristics Of Permanent Magnet Motor For Direct Drive Screw Pump Under High Temperature Difference

The permanent magnet direct drive screw pump drive technology has become the mainstream of current oilfield applications.Compared with the traditional beam pumping unit,the permanent magnet direct drive screw pump oil production technology has remarkable features such as no stroke,high oil recovery efficiency and convenient adjustment.The geographical location of Daqing Oilfield is special,and the extreme temperature difference is large.When designing the permanent magnet motor for direct drive screw pump drive,the influence of temperature is considered,and the performance of the motor is improved from the selection of the pole groove and the selection of the heat load.The temperature in Daqing Oilfield has changed dramatically.The high temperature is high but the duration is short,the low temperature is low and the duration is long,and the annual average temperature is low.Because of the low speed,the permanent magnet motor for direct drive screw pump can only adopt the natural cooling method,which makes it difficult to select the thermal load of the permanent magnet motor.The higher temperature difference will cause the output capacity of the permanent magnet motor under high temperature environment.Therefore,the influence of the heat load value on the temperature rise of the permanent magnet motor for the direct drive screw pump is analyzed.In terms of load,the influence of extreme ambient temperature changes on the load capacity of the motor is analyzed.The effect of high temperature difference environment on the temperature distribution of crude oil in oil wells was studied.It was found by fluid field analysis that under the low temperature environment of minus 30°C,the temperature of crude oil near the wellhead is lower,which is closer to the freezing point of wax,which is easy to form wax.In turn,the motor load is increased.Under the premise of satisfying the maximum load condition,reducing the amount of winding material used further improves the economic performance of the motor.The pole slot fits the selection aspect.The radial force wave distribution,cogging torque,torque ripple and air gap flux density distribution of common q-value motors are compared and analyzed.In the design of the magnetic pole structure,the surface-mounted magnetic pole structure composed of a rectangular permanent magnet and a single curved metal magnetic conductive block is used to study the influence of the shape of the metal magnetic conductive block on the sinusoidality of the air gap magnetic flux density waveform.On the basis of the analysis,a thermal load of about 1400A~2/(cm·mm~2)was selected,and a permanent magnet motor for 18.5kW direct drive screw pump was designed.The thermal analysis software was used to analyze the steady temperature field of the motor.The prototype was tested on the test bench and the oil field.The test results show the excellent performance of the new magnetic pole structure and the economical practicability of the motor temperature optimization design.