| The vacuum contactor is one of the key basic component for electrical power systems,which is mainly used for switching frequently on and off the AC and DC main circuit as well as large-capacity control circuit.When the contactor is operated,the bouncing of the moving contacts,the collision between the armature and static core and the ablation of the arc will greatly reduce the lifetime of the contactor.Electromagnetic mechanism is the most important factor which influences performance of the vacuum contactor,mechanical lifetime and electrical lifetime.The design of vacuum contactor integrates disciplines of mechanics,electricity,magnetic,thermal and so on.It not only needs a long period of designing and studying,but also needs the higher cost.Therefore,it has important theoretical and practical significance to study and optimize the vacuum contactor electromagnetic mechanism based on computer-aided technology and finite element.The thesis is based on the model of Schneider’s medium voltage vacuum contactor with two-coils.The static and dynamic analysis on electromagnetic mechanism which is combining experiments and simulations was carried on.And optimizing design for the electromagnetic mechanism increased the lifetime of contactor.Firstly,the 2D finite element model of the vacuum contactor electromagnetic lifmechanism was established in Maxwell,and the variation trend of the magnetic flux density in the 2D static magnetic field was analyzed.It showed that the magnetic flux density increased as the working air gap decreased.The 3D model of electromagnetic mechanism was established by using Solidworks,and imported it intoMaxwell for 3D static simulation analysis.According to the result,the trend of magnetic flux density was the same as 2D simulation.Under different voltage,the static magnetic force and spring force were analyzed at different working air gaps.It showed that the electromagnetic force was inversely proportional to the working air gap when the voltage was constant,and vice versa.And the electromagnetic force was greater than the spring force under 85% and 100% rated voltage.Secondly,according to the comprehensive analysis of magnetic field equations,circuit equations and mechanical equations,the dynamic mathematical model of electromagnetic mechanism was established.Based on the analysis of the static characteristics,the dynamic characteristics of the electromagnetic mechanism were simulated and analyzed,and the relationship of the velocity,displacement and current under different voltage is studied.It was found that with the increase of voltage,the higher the starting current,the faster the closing speed,the shorter the closing time.Furthermore,the orthogonal experiment design method was used,including several variable factors such as the core radius,the coil turns,armature depth and so on.It is the key to reach the goal of optimizing closing speed,closing time of vacuum contactor by seeking the the optimal combination.Through the range analysis,the significance of the factors influencing the dynamic characteristics was determined,and the best solution was found as A1B3C3D3.The dynamic simulation results showed that the speed of the armature was reduced by 2.5% and the closing time was shortened by 0.2%.Finally,the experimental prototype was designed with the optimized parameters.Results of the experiment conformed to the enterprise standards,it showed the trend of characteristic curve was approximately coincident with the simulation result and the error value was less than 20%.Research provided certain references for contactor development. |
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