抄録
A number of study on the transport and thermodynamic properties have been reported on the SF6 gas arcs for high voltage, high current circuit breakers with including the impurity contamination of Cu vapor, Al vapor or PTFE (-C2F4-) vapor. Until now, there are few study for the general plastic vapor contamination. This paper describes the transport, thermodynamic and wall-stabilized arc properties of air contaminated with plastic vapors found in arc-chamber of low-voltage but considerably high-current circuit breakers. Total 31 chemical species were took into account in the calculation of plastic vapor contaminated air, which were produced by chemical interactions between mixed particles such as OH, CO, NH, CN, etc.. The plastic material considered here is polymethylpentene (-C3H5-), polybutylene (-C4H8-), polymethylmethacrylate (-C5H8O2-), polybutyleneterephthalate (-C12H14O4-) and polycarbonate (-C16H18O3-). Calculation results showed that the electrical conductivity σ below 7, 000 K is decreased by the plastic vapor contamination compared to the pure air, especially, in the case of plastic material having no oxygen atom. The thermal conductivity κ is, on the contrary, increased by the plastic vapor contamination, especially at around 3, 600K, where κ takes three-times larger value compared to the pure air due to H2 and OH dissociation reactions. Based on the transport and the thermodynamic properties thus obtained, transient characteristics of the wall-stabilized air arc were calculated for the current decreasing ratio di/dt of the alternating current 1, 000 A (rms.) around the current zero. The time-dependent decaying properties of the temperature distribution and the arc conductance were disenssnd for plastic contaminated conditions.
