Analysis On Arcing Characteristics And Experiments Of Electrical Contacts In Automobile Relays

Automotive relays are widely used in the low voltage electrical system to make and break electrical current. The quality and operational behavior greatly influence the reliable performance and safety of the whole automobile system.The research on arc characteristics, especially the arc duration is one of the most important work in the field of electrical appliance and electrical contact. This thesis summarized the rules between arc duration and its influencing factors, such as current, supply voltage, circuit time constant, materials, opening speed. Moreover, arc characteristics on low voltage switches are analyzed, the physical process in the arc region is explained.The thesis carried out a new mathematical model of the dynamic V-I characteristics of the breaking arc to calculate the arc duration of contacts.In order to examine the validity of this model, a set of direct current source is designed, which uses the technique of three-phase bridge semi-control. A PC-DAQ data acquisition system is built with the technique of LabVIEW virtual instrument. The system is applied to sample, display and store the current waveforms obtained from the contact tests. The electrical contact tests were performed under the resistive, inductive and lamp load at 14VDC with the contact meterials, AgSnO2, AgNi10, AgNi0.15, respectively. After the tests, breaking arc duration is extracted from breaking current waveforms.As a result, the simulation results are in good agreement with the test results. The mathematical model well revealed the tendency of arc duration with the supply voltage increasing.Due to the limitation of the mathematical model, it is pointed out that achievement of wider dynamic arc V-I characteristics is vital for the arc characteristics, and it should be focused on in the further research.