Eccentric Unbalanced Magnetic Pull And Vibration Characteristic Analysis Of Permanent Magnet Direct Drive Wind Turbines

Permanent magnet direct-drive generator is a kind of driven directly by the wind generator,the generator using multipole motor directly connect with the impeller to drive way,from the traditional gear box parts.Due to the gear box is currently in the megawatt wind turbine is easy to overload and premature failure rate is higher,therefore,there is no direct drive gear box type wind power engine,with low wind speed when the high efficiency,low noise,high life,reduce the unit volume,reduce operation maintenance cost,and many other advantages.This paper is to study nonlinear magnetic generator under eccentric tension calculation,eccentric and unbalanced magnetic pull on the generator rotor and generator stator and rotor system dynamic properties of influence;And in a nonlinear system,alveolar different resonance frequency may cause.Firstly introduces the basic principle of permanent magnet synchronous generator,mainly including the structure characteristic of permanent magnet synchronous generator.According to the structure characteristics of generators,static uneven air gap and dynamic imbalance caused by uneven air gap magnetic force characteristics were analyzed.Based on vibration eccentricity and eccentric mass condition,by solving the air gap permeance,fundamental magnetomotive force and air gap flux density,Maxwell stress method was employed to reinforce the generator rotor surface integral,finally it is concluded that unbalanced magnetic pull on the horizontal and vertical direction of the nonlinear expression,and the solution is the establishment of dynamic model for the following and provide strong support.Secondly according to the results of the calculation of unbalanced magnetic pull,the application of the theory of vibration mechanics,the generator rotor vibration is decomposed into horizontal and vertical directions,starting motor rotor dynamics model is established,and lists the dynamics equation.Model of the rotor of the generator in the presence of nonlinear damping and unbalanced magnetic pull power three items of three different case calculation and analysis the natural frequency,it is concluded that unbalanced magnetic pull on the natural frequencies of the rotor system;Also got under nonlinear vibration amplitude and the natural frequency of the relationship.After again upon the forced response analysis of rotor system,study the influence of nonlinear term on amplitude-frequency curve.Again,the unbalanced magnetic pull consider for nonlinear elastic force,the stator and rotor is connected as a whole.Analysis of such an internal force of the stator and rotor system internal influence.Finally,considering the low speed,this kind of generator frequency is low,does not cause the characteristics of resonance,so emphatically analyzes the external incentive for alveolar resonance frequency and the harmonic frequency may cause.Radial force calculation alveolar frequency,and establish the cogging frequency radial force under the action of rotor system dynamic model.Respectively analyzed the resonance,primary resonance,super harmonic resonance and harmonic resonance.