Measurement of Arc Properties and Spectrum Intensity in AC Arcs surrounded with Plastics

Abstract

This paper describes the experimental results on the arc quenching properties under plastic-plates surrounded condition found in low-voltage circuit breakers. The alternating current used is from 500 to 1, 100A(rms. ) with 60-Hz frequency. The plastic material investigated here are polymethylpentene(-C₃H₅-), polymethylmethacrylate(-C₅H₈O₂-), polybutyleneterephthalate(C₁₂H₁₄O₄-), polycarbonate(-C₁₆H₁₈O₃-) and PTFE(-C₂F₄-). In conjunction with the usual arc current and voltage measurements, two images of spectrum intensity of 511 and 522nm emitted from copper electrode vapor are detected simultaneously by using two band pass-filters. A high speed digital video technique (4, 500 frames per second) is used for analyzing the transient space movement of copper vapor.
The arc voltage is strongly influenced by the plastic materials rather than the arc current. Especially, in the case of-C₃H₅-, the magnitude of arc current was strongly limited by its high arc voltage. On the other hand, in the case of-C₂F₄-, the arc can't beinterrupted and the arc voltage is the lowest value of all. The arcing period isalso much influenced by the sort of plastic materials (most shortest and longestwere-C₃H₅-and-C₂F₄-, respectively), while it shows almost no change with amplitude of arc current. The spectroscopic images of copper vapor obtained by high speed video for transparent plastics of-C₅H₈O₂-and-C₁₆H₁₈O₃-showed that the vapor expanding speed of the former is considerably faster than that of the latter. The results indicate strongly that the arc quenching property is affectedby the ablation and blast speed of arc-surrounding plastic materials.