Optimization Analysis For Damping Performance Of Eddy Current Damper

Modern civil engineering structures are gradually developing towards high flexibility,long span and light weight,and structural vibration problems are becoming increasingly prominent.Eddy current dampers,as energy-consuming components of tuned mass dampers(TMD),are currently playing an important role in solving structural vibration problems.To improve the damping performance of the eddy current damper and promote academic research and practical engineering applications,this paper takes a planar eddy current damper(PECD)widely used in engineering as the research object,because of the low energy dissipation efficiency,low material utilization,inaccurate research methods and performance evaluation indexes,and lack of contrastive analysis of different configurations and magnetic circuits.Then,based on experimentally verified three-dimensional electromagnetic field finite element analysis methods,using intuitive indicators including effective coupling rate of adjacent permanent magnets and equivalent damping coefficient,configuration and magnetic circuit optimization of external and built-in single layer PECD and multi-layer PECD was studied.The main research contents and results include the following 4 parts.(1)A performance index that can directly reflect the coupling effect between adjacent permanent magnets is proposed.The effective coupling rate of adjacent permanent magnets can qualitatively and quantitatively reflect the influence and degree of the coupling effect between permanent magnets on the PECD damping performance,and guide the further optimization of the configuration and magnetic circuit.(2)The optimization of the permanent magnet spacing and arrangement of single-layer PECD is carried out,and the damping performance of external and built-in PECD is compared.The optimal configuration and magnetic circuit of external single-layer PECD should be that conductor copper plate should be supplemented with a magnetically permeable steel plate,and along the relative movement direction of the cutting magnetic induction line of the conductor copper plate,magnetic poles between adjacent permanent magnets are arranged opposite with a spacing being 0.7 time the same size of permanent magnet.While,the optimal configuration and magnetic circuit of built-in single-layer PECD is that along the direction perpendicular to the relative movement direction of the cutting magnetic induction line of the conductor copper plate,magnetic poles between adjacent permanent magnets have the same polarity,and their spacing is as small as possible.In addition,compared with the external single-layer PECD,the built-in single-layer PECD dissipates significantly higher energy,but the amount of permanent magnets and the corresponding cost are also higher.Both have strength and weakness.(3)The configuration and magnetic circuit of single-layer and multi-layer PECD are compared.Then,based on the research of single-layer PECD,the optimal configuration and magnetic circuit of multi-layer PECD is obtained.The permanent magnets on the same layer fixed by non-magnetic material are arranged in an array,and along the relative movement direction of the cutting magnetic induction line of the conductor copper plate,magnetic poles between adjacent permanent magnets are arranged opposite with a spacing being 0.4 time the same size of permanent magnet,while along the direction perpendicular to the relative movement direction of the cutting magnetic induction line of the conductor copper plate,magnetic poles between adjacent permanent magnets have the same polarity,and their spacing is as small as possible.The thickness of permanent magnet is 0.7 times of the length,and copper plate is 8 mm.In addition,under the premise of meeting normal work,magnetic gap should be as small as possible.(4)The energy dissipation efficiency of PECD has a linear positive correlation with layers,and the energy dissipation efficiency of a single conductor copper plate is inversely proportional to layers.With the increase of layers,the equivalent damping coefficient of a single copper plate tends to be stable,and a corresponding calculation formula is obtained,which can be used to guide the design for configuration and magnetic circuit of multilayer PECD according to an established equivalent damping coefficient in actual engineering vibration control.