Study On Vibration Analysis And Vibration Reduction Method Of Permanent Magnet Synchronous Motor For Marine

In this thesis,a marine permanent magnet synchronous motor is used as the research object,and the vibration and vibration optimization of the motor is studied.The electromagnetic,mechanical and structural have been analyzed,calculated and optimized to reduce the vibration caused by the electromagnetic force of the motor.Firstly,the vibration of the motor is analyzed from the electromagnetic and the vibration The electromagnetic vibration of the motor is analyzed from five aspects: magnetostriction force,radial force,tangential force,ripple torque and cogging torque.The radial force which occupies the dominant position of electromagnetic vibration is calculated by Maxwell tensor method,and the expression of radial force in the load and no load state.Then the main frequency vibration causing by radial force is determined by finite element simulation analysis.By changing the electromagnetic parameters of the motor,optimizing the shape of the permanent magnet and changing the size of the slot-openning,the radial force in the motor is optimized with the minimum air gap magnetic density total harmonic distortion rate(THD),which reduces the electromagnetic vibration of the motor.Then according to the literature from the mechanical aspects of the motor vibration analysis,the stator mechanical structure has been changed to reduce the vibration grade of the motor.According to the theory of thin shell theory,the vibration formula and the formula of modal parameters of mechanical structure of motor are deduced.The influence of mechanical structure parameters on the modal parameters and vibration of thin shell is analyzed.Then the finite element model of the motor is modified and analyzed by means of experimental method.Finally,the modified finite element model is used to analyze the influence of the stator structure on the vibration and modal frequency with different structural parameters under the excitation of the same electromagnetic force,and the conclusion that the thick yoke,short tooth and narrow tooth structure is beneficial to reduce the vibration.Secondly,through the optimization design of the motor housing and housing shape to reduce the motor vibration.The modified finite element model is used to observe the effect of these changes on the vibration of the motor by changing the shape of the reinforced ribs of the chassis and changing the shape of the motor chassis.According to the finite element simulation calculation,when the motor casing adopts the circular cooling rib and the ribless frame,the vibration of the motor in the direction perpendicular to the machine seat surface will be weakened,and the average vibration level will be reduced.Finally,the current harmonic introduced by PWM switching frequency is optimized to reduce the vibration of the motor.Based on the theoretical research,the distribution of radial force of the motor under PWM power supply is analyzed,and the high harmonics near the switching frequency are weakened by increasing the inductance value of the motor and the random switching frequency PWM technology based on the 2 state Markov chain.