Research On Fault Diagnosis Method Of Motor Bearing Based On Electrical Characteristic Analysis

As an important electrical equipment,asynchronous motor is widely used in agriculture,commerce,industry and other fields.As an important component of motor,the running state of rolling bearing will not only affect the motor,but also affect the performance of the whole system.Bearing faults account for about 40% of asynchronous motor faults,while the outer raceway,as the support of the whole bearing,accounts for about 70% of all kinds of bearing faults.Therefore,it is particularly important to diagnose the initial fault of asynchronous motor bearing.Firstly,the fault features of bearing failure are analyzed in this paper,deeply and thoroughly.Secondly,a series of novel detection schemes are presented creatively.Furthermore,this paper proposes a new fault diagnosis method of asynchronous motor bearing outer raceway.a novel diagnosis method of rolling bearing outer raceway fault based on the rotating frequency multi-modulated components in stator current signal is proposed for the first time;Finally,the validity and feasibility of the above-mentioned detection schemes has been verified by a great deal simulation and experiment results.The distinguished contributions of this paper are listed in details as the following.(1)Firstly,the air gap change model of bearing fault is introduced,the expression of air gap length in the case of outer raceway fault is deduced in detail.Then the mechanism of rotor mixed eccentricity in the case of bearing fault is described.According to that,the fault characteristic frequency generated by eccentric fault in stator current signal is applied to bearing fault diagnosis.(2)The continuous subdivision Fourier transform and Hilbert demodulation technique are used for bearing fault diagnosis.The experiments show tha t both methods can only diagnose effectively when the asynchronous motor runs at full load and the bearing has serious fault.Compared with the continuous subdivision Fourier transform method,the Hilbert demodulation technique is more concise in the spect ral distribution components,which can directly find the fault frequency components of the signal,and improve the efficiency and accuracy of the fault diagnosis process.(3)Aiming at the problem that the published diagnosis method s based on motor current signal analysis(MCSA)is not able to diagnose the mild fault of rolling bearing outer raceway,or is no longer effective while the motor operates with no load or slight load,a novel diagnosis method of rolling bearing outer raceway fault based on the rotating frequency multi-modulated components in stator current signal is proposed.This method focuses on the influence of the fault on the rotating frequency multi-modulated components.And thus,it can diagnose effectively the mild fault of rolling bearing outer raceway,even the motor is operating with no or light load.