Research On Suppression And Fault Diagnosis Of Vibration In Asynchronous Motor

The vibration of AC motor can be divided into electromagnetic vibration,mechanical vibration and aerodynamic vibration,in which electromagnetic vibration and mechanical vibration are the main components.For high-power motor,serious vibration will produce strong vibration and noise,and cause damage to the motor structure.For small and medium-sized power motor,although the absolute value of motor vibration and noise is not too high,but in the quiet environment,the human ear is very sensitive to the vibration and noise in the middle and high frequency range.It will put forward the vibration and noise of motor higher requirements.At present,the vibration and noise of AC motor has become one of the hot topics in this field.In view of the vibration and noise problems of AC asynchronous motor,the harmonic of variable frequency power supply,the optimization design of motor structure and the fault diagnosis based on motor vibration signal are studied and analyzed.(1)In order to effectively reduce the vibration and noise of AC motors from PWM power supply,a random pulse width modulation(RPWM)selective harmonic elimination method is proposed.The harmonic in the power supply is one of the causes of motor vibration and torque ripple.The torque ripple will further aggravate the vibration and further cause the vibration of the motor drive mechanism.The high-order harmonics in the variable-frequency power supply are mainly related to the switching frequency of the inverter,which is usually concentrated near the switching frequency and its multiples.Especially when the harmonic frequency is close to the natural frequency of the system,the vibration will be further aggravated and cause strong resonance.In this paper,a random PWM selective harmonic elimination method is proposed for AC asynchronous motor with variable frequency power supply.The method of canceling the front and rear terms of PWM pulse Fourier series is used to selectively eliminate the specific harmonics which are easy to cause vibration and noise of the motor,so as to suppress the vibration and noise of the motor.On the basis of analyzing the harmonic output under the condition of open circuit fault of inverter,the inverter can continue to operate stably with faulty through fault-tolerant control method,and the vibration of asynchronous motor under fault-tolerant operation condition is analyzed.The two-level and multilevel fault-tolerant method are included.(2)From the perspective of the motor,the low-order harmonic content of the radialmagnetic density is weakened to effectively reduce the radial electromagnetic force and improve the vibration and noise of the motor with the optimized design of the structure of the motor.(3)Aiming at the non-stability of vibration signal of motor bearing,the characteristics of inaccurate signal are extracted.This paper presents a fault diagnosis method based on the feature extraction method of set empirical modal decomposition and energy moment,and the combination of fault recognition by self-organizing feature mapping network.Firstly,the original vibration signal is decomposed into a series of IMF with different characteristic time scales by using EEMD,and the energy moment of each order of IMF is calculated to construct the fault eigenvector.On this basis,the self-organizing feature mapping network method is used for fault diagnosis of motor rolling bearing.There are 106 pictures,21 tables and 208 references in this paper.