Suppression Of Mechanical Vibration For Three-phase Induction Motor

Three-phase induction motor is favored by washing machine manufacturers at home and abroad because of its advantages of simple structure,reliable operation,light weight and low cost.As the core component of washing machine,the noise and vibration of motor are the key indicators of washing machine manufacturers.The performance,noise and vibration of the motor directly affect the customer’s experience when using the washing machine.The three-phase induction motor of WL Motor Company ranks first among the defects of production line and customers,which requires immediate improvement to reduce customer complaints.In this paper,the preliminary analysis of defective products through power-on/off verification concluded that mechanical factors cause 90% of the noise and vibration defects,and the research direction is initially locked to the mechanical system of the motor.Through the noise and vibration detection to analyze the spectral characteristics,it is confirmed that the mechanical vibration frequency is mainly concentrated in the first and second octave.The vibration direction is mainly in the axial direction of the motor as well as tangential and radial direction.According to the test results,one and two-fold frequencies are studied as two sub-topics from the principle of the excitation force generated by them.By reviewing the literature and conducting relevant experiments,the principle of dynamic balance amount affecting one-frequency and the characteristics on vibration frequency and direction are introduced in detail,and it is concluded that the excitation force of one-frequency vibration mainly comes from the dynamic balance amount of rotor.Cross-validation is used to verify that the rotating parts affect the doubling frequency vibration,and with reference to the characteristics of bearing damage frequency in equipment failure analysis,some factors affecting the doubling frequency vibration are sorted out through simulation and experiments.A rotor shaft bending model was proposed and derived to cause the difrequency vibration excitation force,and the correctness of the model was verified by software simulation and physical inspection,and the actual cause of the difrequency vibration excitation force was deduced to be the deviation of the whole rotor in the motor running centerline,and the problem of bearing installation eccentricity was also proved simultaneously.Based on the conclusion of theoretical analysis and verification,a new standard of permissible dynamic balance was proposed for the suppression of doubled frequency vibration,and the process design of the new standard was completed,so that the improvement measures could be implemented.At the same time,we completed the design of a plan to improve the bending of the rotor shaft,and developed a new process for the processing of the rotor shaft to achieve the suppression of doubled frequency vibration.We also completed the improvement of bearing damage and poor roundness of rotor shaft,and improved the suppression of small probability of occasional octave vibration.As a result of the improvement,the vibration defective situation has been improved in the feedback from the customer for nearly three months and in the internal production for nearly one year,and the single machine can better meet the requirement of vibration ≤120 d B at 200 Hz and 400 Hz,and the overall primary defective rate has been reduced to less than 1%.