Research On The Characteristics Of Arc And Erosion Under Magnetic Field

Switching apparatus is widely used as a control unit in many fields of civil economy and national defense, and its reliability is of great importance. For switches with contacts, the key factor which decides its lifespan is the arc between the contacts when breaking and closing the circuit. The mechanisms of the arc and erosion are extremely complicated. As the arc and erosion characteristics take on strong randomness, it is pretty difficult for theoretical study. Therefore, it is of great practical value to design a fully functioned arc experiment platform. This paper studies about the effect of the magnetic field on break arc and erosion characteristics with the arc experiment platform, which promotes the development of magnetic field arc blowing technique.An arc experiment system is designed based on high-speed photographing with the contacts break with a constant speed by collision. During the arcing process, the arc images are photographed with a high-speed camera, and the contact voltage and current waveforms are acquired with a USB data acquisition card, both of which are transferred to the computer. Arc experiments can be carried out with different contact materials, arc chamber atmosphere, break velocity, break power and magnetic fields.The arc image series are processed with different methods for image enhancement and edge detection, and the processing method most fit for switching arc is decided. Arc parameters such as arc diameter, extinction length, arc root position and velocity are extracted. Based on the theory of three-color temperature measurement, the arc temperature distribution is acquired. The arcing time information including arc duration, metallic phase duration and gaseous phase duration is extracted from the contact voltage waveform. The contact erosion information is studied with the help of the electrical balance and optical microscope.Based on the arc experiment platform, the arc characteristics under magnetic fields are investigated when the Ag/SnO₂ contacts break 28V/5A inductive load and 28V/25A resistive load respectively. The relationships between the flux density and such parameters as arcing time, arc diameter, arc root position and mass variation are given. The results can be applied in the design of switching apparatus with permanent magnetic field blowing arc technique.