Research On Motor Phase Fault Detection Based On Self-mixing Grating Interferometer

As an inseparable electrical equipment in people's production and life,the normal operation of the motor guarantees the normal operation of the entire production and life systems.Online monitoring of the motor is very important.In the motor fault detection method,the stator current method is a common method for monitoring the motor.However,under some faults,the main characteristic frequency may be similar to the fundamental frequency,and the characteristic frequency cannot be distinguished,resulting in the failure characteristic of the motor is not obvious.The motor will vibrate in different degrees during normal operation and faults,and its vibration amplitude and spectrum components are different.Almost all motor faults are displayed through vibration,so vibration can objectively reflect motor faults and is more suitable for monitoring motor faults.In order to improve the anti-interference ability of the measurement technology,this paper proposes SMGI vibration measurement based on the differential technology based on SMGI(self-mixing grating interference technology).And the technology is applied to the electrical fault measurement of the motor to solve the problem that the motor is greatly interfered by the environment during detection,and improve the accuracy of fault diagnosis,which has certain application value.The main research contents of this paper are as follows:First of all,the electrical fault types,detection methods and fault diagnosis mechanism of the motor are analyzed.Through the analysis of the stator winding inter-turn fault mechanism,the rotor broken bar faults mechanism analysis and the phase faults operation faults mechanism analysis,the motor fault vibration detection technology is studied.Then,using the theoretical model of the three-mirror Fabry-Perot(FP)cavity,the mathematical model of SMI(self-mixing interference)is analyzed,and the frequency formula and power equation of SMI are obtained,from which the motion related to the target object information is derived.In order to reduce the influence of external temperature changes on the measurement accuracy,the grating is introduced into the SMI measurement device.The mathematical model of SMGI is analyzed,and it is theoretically proved that the fringe resolution of this method is related to the pitch of the grating.It is proved by simulation and experiment that a fringe change of SMGI corresponds to a grating pitch.Secondly,in order to make the signal have higher quality and signal-to-noise ratio,SMGI vibration measurement technology based on differential technology is proposed.Two PDs are used to receive and monitor changes in output optical power.A part of the light is reflected back to the internal cavity of the laser through the grating and is received by the internal detector PD1 of the laser.The other part of the light undergoes second-order diffraction through the grating and is received by the external detector PD2.The signals received by the two PDs are differentially processed to obtain interference signals after noise cancellation.Theoretical analysis and experiments show that the differential signal can eliminate the common mode noise in the signal,and can improve the signal-to-noise ratio and signal quality of the signal.Finally,the motor electrical fault detection device is established,and the SMGI vibration measurement technology based on the differential technology is applied to the motor electrical fault detection.The inter-turn faults of the stator windings,the rotor broken bar faults and the phase-deficient operation faults were tested separately to conduct the electrical fault detection technology experiment of the motor.The experimental results confirm the feasibility of applying this method to motor fault measurement.