Experimental Research On Alternating-current Inductive Arc Characteristics

During the relay breaking process, the arc contaminates the area around the contacts, which seriously affects the reliability of the relay, especially in power system applications. It may even cause fires and other serious consequences. Therefore, studying on the characteristics of the arc is of great necessity. As a matter of fact, in the actual relay application environment, the loads of the circuits are mostly Alternating-Current(AC) inductive. AC inductive arc is more destructive compared with resistive arc. Therefore, studying on characteristics of AC inductive arc is the key breakthrough for the guidance to solve relay’s reliability problem.This paper summarizes and analyzes factors which would influence the AC inductive arc characteristics. Besides the load voltage and load current, the effects of the contact gap and breaking speed also need to be investigated. Therefore, this article designs a mechanical device to adjust the contact gap and breaking speed. Utilizing experimental method, characteristics of AC inductive arc at different voltages, different currents, different speeds and different contact gaps are worked out.In this article, by using a high-speed camera, the arc motion process is photographed. Through the image processing and analyzing software, the arc characteristics such as movement track, arc length and arc duration are extracted. At the same time, the arc voltage and current waveforms at both ends of the contacts are acquired through signal acquisition system, and the arc energy is calculated. Through the analysis of arc duration, arc energy, arc length and arc image characteristics of AC arc, Taguchi DOE optimization method is used to optimize the best contact gap and breaking speed for inhibiting AC inductive arc.Finally, according to the analysis result, the mechanical structure of the original relay is optimized based on the current structure, in order to achieve the optimal contact gap and breaking speed. Relay samples are produced, and experiments are carried out to verify the optimization result.