Vibration Characteristics Of Induction Motors With Supply Containing Low-Order Harmonics

Induction motors have become the main driving equipment for industrial loads such as fans,compressors,and pumps due to their high reliability and easy maintenance.With the widespread application of frequency converters and nonlinear loads,the power supply of the motor contains significant low order harmonics,which in turn leads to increased motor vibration.In order to weaken the adverse effects caused by low order harmonics of the power supply and achieve the goal of high energy efficiency and low vibration of the motor,this article analyzes the vibration characteristics of induction motors when the power supply contains low order harmonics,and studies measures to reduce motor vibration.The main research content is as follows:(1)Using analytical and finite element methods,the electromagnetic force of an induction motor containing low order harmonics in the power supply is analyzed and calculated.Firstly,the analytical expressions for the air gap magnetic density and radial electromagnetic force generated by the cross coupling of various magnetic fields inside the motor are derived,and the order and frequency of the additional radial electromagnetic force generated by the harmonic current are analyzed;Then a finite element simulation model is established to compare and analyze the force wave characteristics of the air gap magnetic density harmonic component and radial electromagnetic force of the motor under two conditions:an ideal sinusoidal power supply and a power supply containing low order harmonics.It is verified that the power supply containing low order harmonics would lead to an increase in the amplitude of the radial electromagnetic force of the motor.(2)To solve the problem of intensified electromagnetic vibration of motors caused by additional electromagnetic forces generated by low order harmonics of the power supply,a winding improvement scheme based on low harmonic winding is proposed from the perspective of motor body design.By comparing and analyzing the air gap magnetic density and radial electromagnetic force distribution characteristics of different winding schemes,the winding design scheme that can most reduce the radial electromagnetic force amplitude of the motor is selected.(3)The electromagnetic vibration characteristics of the motor before and after winding improvement were studied.Firstly,the finite element method is used to conduct modal analysis of the motor,and the vibration mode and natural frequency were calculated;Then,harmonic response analysis is conducted on the motor,and the vibration acceleration of ordinary winding and low harmonic winding motors is compared and analyzed;Finally,a prototype of low harmonic winding is trial-produced and a vibration testing experimental platform is built,verifying the objectivity of voltage harmonics and the effectiveness of using short span low harmonic winding to reduce low-frequency vibration of the motor.