Research On Induction The Feature Of Motor Bearing Fault Based On Harmonic Injection

Three-phase induction motor plays an important role in the field of industrial productions.As the main component of motor,bearing has a high incidence of malfunction.Researching on the monitoring of bearing faults is of great significance.Considering the deficiency of the Blodt model,in this thesis,the vibration form of the single point fault is studied from the dynamic point of view.This thesis builds a dynamic model of a single point of failure of the bearing outer ring.Through the digital calculation and analytical calculation with Matlab,this thesis presents a detailed analysis of the vibration characteristics of bearing fault further derives relation between the vibration form,vibration frequency and attenuation coeffcient.Then this thesis obtains the expression of the friction torque when single points bearing failure and the new model of the load torque caused by bearing fault cause.On this basis,the expression of the stator current of induction motor under the condition of bearing fault is deduced in detail,and the results show that the amplitude of the characteristic frequency in stator current varies with the width of the fault and the speed of the motor.Through the simulation experiment of Matlab,the current spectrum of different fault widths and different speeds are compared and analyzed.The simulation results verify the correctness of the theoretical derivation.The friction torque of the bearing tested by the bearing dynamic friction test platform verifies the theoretical derivation.According to the actual detection of induction motor,weak characteristics signals of bearing fault is easy to be submerged in the high background noise,which is not conducive to the bearing fault detection.With the help of the harmonic injection induction motor bearing fault experimental platform,the bearing fault characteristic frequency and harmonic injected high frequency phase modulation can improve the fault feature’s recognition.The experimental results verify the theoretical derivation.In actual bearing fault diagnosis of induction motor,it is necessary to consider the influence of bearing fault width and motor speed,which provide an effective theoretical basis for correctly judging the occurrence and severity of the bearing fault.