The Study On Dynamic Mathematical Model Of Low-voltage AC Contactor Arc And Simulation Of Temperature Field

Low-voltage AC contactor is an important component in low-voltage electrical appliances. It is widely used in all departments as a basic kit component. When low-voltage AC contactor is closed or breaking electric loops, electric arc will be generated between the contact terminals. Once the switching arc of low-voltage AC contactor reaches high temperature during arcing, the attributes of low-voltage AC contactor will be greatly infected, the reliability will be down-graded, and the useful life will be shortened. This dissertation mainly focuses on the diameter changes of the switching arc of low-voltage AC contactor during arcing, the temperature changes and distributing orders of the electric arc, and the simulation calculation of the switching arc of low-voltage AC contactor. The research results of this dissertation can help improve the contact terminal material, polish up the structure of electrical appliances, and provide support for uplifting of electrical attributes of low-voltage AC contactor.In this dissertation, array CCD camera based high-speed image collection system for the switching arc of low-voltage AC contactor is adopted, to collect the series of arcing images from burning to vanishing. Self-adaptive median filter is applied to de-noise the images of low-voltage AC contactor arcing. Laplacian sharpening method is used to sharpen the edges of arcing images and relevant detail information. Besides, based on the optic features of the high speed image collection system for the switching arc of low-voltage AC contactor, the system is demarcated, the arc diameter during arcing is calculated with accordance with it, and the arcing movement rules are analyzed. Temperature is one of the important physical features of electric arc. Thus, the study on temperature changes and distribution orders of low-voltage AC contactor arc during arcing is of crucial importance. This dissertation analyzed non-contact temperature measurement; studied the relationship between arc energy radiation and the pixel gray value of collected CCD image based on the hereinabove analysis; designed the dual-wavelength arc radiation image collection device; demarcated the collection device by blackbody furnace; re-constructed projection temperature field, by dual-wavelength radiation image projection during electric arc arcing, based on the theories of dual-wavelength color-comparison temperature measurement.In addition, this dissertation has considered the features of switching arc of low-voltage AC contactor, established radioactive transfer model of arc and the testing system model, and designed radiation pick-up device for the switching arc of low-voltage AC contactor. With the application of the pick-up device, switching arc under the condition of inductive load was recorded. By computer assisted level-analytical re-construction calculation, three-dimensional temperature field in arcing was re-constructed. And different from the traditional re-construction calculation, this dissertation included projection equation as a constraining term into object optimization. It also recommended a re-construction calculation with constrained least squares estimation. Upon this kind of calculation, the re-constructed three-dimensional temperature field of switching arc of low-voltage AC contactor, can exhibit the distribution of arc radiation energy field and temperature field.Last but not least, this dissertation made detailed theoretical analysis on the interrupting process of low-voltage AC contactor, and proposed the chain dynamic mathematical model for switching arc of low-voltage AC contactor. Chain-arc three-layer physical structure was established on the basis of traditional arc path model. Movement speed of arc was investigated into with classical shock theory. Arc energy balance equation was determined through the analysis on arc plasma energizing process. The distribution of arc temperature field is calculated by finite volume method along the arc radial. Various kinds of physical parameters of arc are calculated upon the distribution of arc temperature field.The subject of this dissertation received National Natural Science Funding (60675014 Motion Mechanism and Simulation Research on Low-voltage Electrical Switching Arc).