某核电厂主给水泵电动机轴向振动故障诊断

Fault Diagnosis of Axial Vibration of Main Feed Pump Motor in Nuclear Power Plant

某型主给水泵电动机运行时,多次出现相似的轴向振动高缺陷,影响到设备安全。针对此问题,结合该型电动机结构特点,建立两侧球轴承支承的简易转子动力学模型。当球轴承自动调心功能不佳时,理论分析得知:转子两侧端部气隙会出现混合偏心、轴颈承力中心线与轴承座中心线不重合等缺陷;在不平衡磁拉力与不平衡离心力耦合作用下会激发与径向振动特征相似的轴向振动;当气隙混合偏心距以静偏心为主时,轴向振动的频谱以二倍转子旋转频率为主,振幅与等效偏心距成比例;提高转子平衡精度降低等效偏心距的新方法可同时降低径向振幅与轴向振幅。通过改善球轴承工作状态、优化气隙超差情况及动平衡试验彻底解决了该类共性缺陷,验证了理论分析的正确性。

There are several similar defects of high axial vibration happened during the operation of main feed pump motors in a nuclear power plants,which affect the safety of the equipment.Combined with the structural characteristics of this type of motor,a simple rotors dynamic model supported by spherical bearing on both sides is established.When the self-aligning function of the ball bearing is not good,a mixed air gap eccentricity on both sides of the rotor will appear,and the center line of the journal bearing force will not coincide with the center line of the bearing seat and so on.Under the coupling action of unbalanced magnetic pull and unbalanced centrifugal force,axial vibration similar to radial vibration will be excited.When the mixed air gap eccentricity is dominated by static eccentricity,the frequency spectrum of axial vibration is dominated by twice the rotor rotation frequency,and the amplitude is proportional to the equivalent eccentricity;the amplitude of radial vibration and axial vibration can be simultaneously decreased by the new method of improving the rotor dynamic balance accuracy and reducing the equivalent eccentricity.By improving the working state of ball bearing,optimizing the air gap out of tolerance and balance test of rotor,this common defect is thoroughly dealt with,and the correctness of theoretical analysis is verified.