Research On Arcing Characteristics Of Breaking Contacts And Electrical Lifetime Extension Control Strategy Of AC Contactors

Alternating current(AC)contactors are a type of electrical switching apparatus that is frequently used in operating making-breaking processes to switch long distance electrical circuits.They are widely used in a great number of fields.Electrical lifetime of AC contactors is far less than their mechanical lifetime,so improving the electrical life of AC contactors is an important topic in electrical.One of the important factors affecting the electrical lifetime of AC contactors is arcs occurring in contact breaking processes,since the breaking arcing characteristics are tightly associated with the electrical lifetime of an AC contactor.Therefore,for the study of the electrical lifetime of AC contactors,test platform and phase selection controller are designed in this dissertation.Experiments have been executed by using LC1D80 of AC contactors and a large number of experimental data has been obtained.Finally,arcingcharacteristics and laws occurring in contact breaking have been studied based on statistics in this dissertation.Studies have shown that there is diversity between two arcs even though the breaking phases are the same for that there is complex conversion between electrical,magnetic,mechanical and other energy types.Hence,investigating one or a small number of arc specimens cannot fully reflect arcing characteristics of AC contactors.Therefore,the arcing characteristics of a large number of breaking processes from a statistical point of view are investigated in this dissertation.Arcing energy,duration and power under different arcing phases are computed in this dissertation.It is concluded that there is a best breaking phase range that has minimum impact on electrical lifetime of AC contactors.An AC contactor lifetime test platform based on statistical analysis has been set up in this dissertation.Test conditions such as the turn on time,time interval and load parameters of the test platform has been set up.A multi-channel data acquisition system is used to capture and store current waveforms of the main circuit and voltage waveforms between contacts.MATLAB is used to analyze the collected data based on statistical methods.Meanwhile,the dissertation has realized the precise control of breaking current phase.The dissertation designs a breaking and closing phase control device,including the circuit design of phaseselection and software design.The device can precisely control breaking phases from 0° to 360°with errors smaller than 1°.The dissertation has carried out the following tests using the phase selection control device: maximum arcing energy breaking,minimum arcing energy breaking,medium arcing energy breaking,the best arcing energy breaking and random phase breaking.The dissertation compares arcing characteristics between those from the best and the random breaking phase schemes,and proves that the proposed scheme effectively improves the electrical lifetime of AC contactors.