Measurement of arc properties and spectrum intensity in AC arcs surrounded by plastics

Abstract

AbstractThis paper describes experimental results on the arc‐quenching properties under the condition of being surrounded by plastic found in low‐voltage circuit breakers. The alternating current used is from 500 to 1100 A(rms) with 60‐Hz frequency. The plastic materials investigated here are polymethylpentene (C3H5), polymethylmethacryl‐ate (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 522 nm emitted from copper electrode vapor are detected simultaneously by using two bandpass filters. A high‐speed digital video technique (4500 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 the arc current was strongly limited by its high arc voltage. On the other hand, in the case of C2F4, the arc cannot be interrupted and the arc voltage is the lowest value of all. The arcing period is also much influenced by the type of plastic material (the shortest and longest were 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 affected by the ablation and blast speed of arc‐surrounding plastic materials. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 140(1): 38–47, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10002