22P083-R
Observation on Decaying Process C2 molecular spectra in Polymer Ablation
Arcs under Free Recovery Condition
フリーリカバリ状態における高分子材アブレーションアークのC2 分子放射強度の減衰過程観測
Yohei Horikawa, Yasunori Tanaka and Yoshihiko Uesugi
堀川洋平, 田中康規, 上杉喜彦
Kanazawa University, Kakuma-machi, Kanazawa, 920-1192, Japan
金沢大学 〒 920-1192 金沢市角間町
In this report the experimental results were presented on the decaying process of polymer ablation arcs underfree recovery condition. The polymer ablation arcs can be seen in low-voltage circuit breakers and arcing
horns etc. Understanding of polymer ablation phenomena is important to elucidate the current interruption
processes in the above breakers. In the present experiments, PTFE and PA66 were used as polymer materials. Spectroscopic observation was conducted to measure C2 radiation intensity and its time evolution.
Results indicated that PA66 causes a much higher decay of the polymer ablation arcs than PTFE.

1. Introduction
The polymer materials are usually used for polymer moulded case in a moulded case circuit breaker(MCCB), or for a gas flow nozzle in a high-voltage
circuit breaker. These polymer materials were exposedby the arc plasma, which is formed between the electrodes in a circuit breaker during high current interruption process. In this case, the polymer is muchablated, which aﬀects the interruption performance ofthe circuit breaker. Recently, a MCCB and an arcing horn have been developed, which eﬀectively utilize the polymer ablation phenomena to enhance theirinterruption capability. However, the polymer ablation
phenomena are much complicated involving mass, momentum and energy tranfer between the arc plasmaand solid polymer. The contamination of polymer ablated vapors also remarkably changes thermodynamic
and transport properties of the arc plasma.
Until now, the authors have paid attention to development of a polymer ablation model for arc plasmas[1, 2]. This model solves the mass, momentum, energy conservation equations of the arc plasma as wellas mass coservation equation of polymer vapor. The
net polymer ablated flux was also estimated using saturation vapor pressure and the redeposition flux fromthe arc to the polymer surface. Using the developedmodel, we predicted the arc voltage and the ablatedpolymer mass in the steady state condition. These results fairly agreed with the experimental results. However, the arc interruption process is essentially undertransient state. Thus, it is necessay to study transient
process of polymer ablation arcs.
This report describes the experimental results on thedecaying process of the polymer ablation arcs underfree recovery condition. The arc current was changed
stepped down from 50 A to 0 A to study the arc decay-Fig. 1: Arc model.
ing process. The time evolution in the radiation intensity of C2 spectra in polymer vapor were measured for
diﬀerent polymer materials.
2. Observation of an polymer ablation arc underfree recovery condition
Fig. 1 shows a schematic of the polymer ablationarc device. An arc plasma is formed between two ironelectrodes. The diameter of the electrode is 6 mm.
The distance between the electrode is 50 mm. Oneof the electrode is surrounded with a polymer cylindrical tube with inner diameter of 6 mm. The distance
between the electrode surface inside the polymer andthe outlet of the polymer is 30 mm.
Fig. 2 illustrates the experimental circuit. The arcdevice is connected to the dc current source. The experiments were made as follows: An arc plasma wasignited between the electrode using a copper wire fuse.
Through this wire, the electric current of 50 A was
supplied by the dc current source, and then the arc
plasma is established between the electrode. During
the arc forming, there occurs polymer ablation, whichcauses a strong gas flow injection from the polymer
outlet. At 0.2 s after the arc ignition, an insulated gate
bipolar transistor (IGBT) connected parallel to the arc
device were ignited. Then, the arc current decreases
suddenly from 50 A to 0 A.
In this experiment, we have chosen two polymer

]A[t 60ne 40rr
uc20rcA0]V[ 5tysi 4ne 3tni 2notia 1
id 0aR

02040

60

80

100 120 140 160

4060 80 100 120 140 160
Time [µs]C2020Fig. 5: Radiation intensity of C2 in PA66 ablated arc.
Fig. 2: Layout of experimental circuit.
44[x10 ]

630

5

Trot=3,100 K
Tvib=5,900 K

PA66
t = 0.8 s
2nd timeExp.
Calc.

425Calculated emission
coefficient [a.u.]

Radiation intensity [a.u.][x10 ]

203152101504000650]A60t[ner 40rucc 20rA0]V[ 5yit 4snet 3ni 2noit 1aida 0R02040

6080

100 120 140 160
C20204060 80 100 120 140 160
Time [µs]Fig. 6: Radiation intensity of C2 in PTFE ablated arc.

these figures, theoretically calculated C2 spectra werefitted to the experimental results, evaluating the rotaFig. 3: Observed spectra(PA66).
tional and vibrational temperatures. The PA66 vapor
has a lower rotational and vibration temperatures than[x10 ][x10 ]
89the PTFE vapor.
T =4,000 KPTFE
8 t = 0.8 s
T =5,600 K
73.2. Time evolution in C2 radiation intensity
7 2nd time
6Exp.
From this observation results in Figs. 3 and 4 , we
6Calc.
5
selected C2 spectral intensity at 464.6 nm to measure.
544Figs. 5 and 6 presents the current and C2 intensity be3
3fore and after the current was changed down to 0 A.
22The t=0 µs on the vertical axis corresponds to the tim1
1ing of the current down. In case of PA66, the C2 radi00400450500550600650ation intensity was kept until t=20 µs, but it decayed
Wave length [nm]rapidly after that. On the other hand, the C2 radiation
Fig. 4: Observed spectra(PTFE).
intensity hardly changed until t=60 µs for PTFE arc ,materials PA66[−C12 H22 O2 N2 −]n and PTFE[−C2 F4 −]n . and then it gradually decreased with time. CompariSpectroscopic observation was carried out around the son with these figure implies that PA66 provides muchoutlet of the polymer tube. Observation area with a a higher decay of the arc plasma than PTFE. This tendiameter of 5 mm was set around the center axis at dency can be obtained also by numerical approach.
the outlet. The polychromator was used to confirm 4. Conclusion
presence of C2 spectra in polymer vapor ejected unThis report presents the experimental results on theder steady state condition. A monochromator with a decaying process of polymer ablation arcs under freephotomultiplier tube were adopted to measure the time recovery condition. PTFE and PA66 were used as polyevolution in the radiation intensity of specified C2 lines mer materials. Spectroscopic observation was conunder free recovery condition in transient state.
ducted to measure C2 radiation intensity and its time
3. Results and discussions
evolution. Results indicated that PA66 causes a much
3.1. Spectra observed under steady state condition
higher decay of the polymer ablation arcs than PTFE.
Figs. 3 and 4 show the observed spectra at the out- References
let of the polymer tube under steady state condition. [1] Y. Takezawa，et al,The Papers of Tech. Meeting.
Switching & Protect. Eng., IEEJ, ED-10-044，SA-10As seen, C2 Swan system around wavelengths of 450–060，SP-10-011，2010.
550 nm was clearly observed both for PTFE and PA66.
[2] Y. Horikawa, Y. Tanaka, Y. Uesugi,The Papers of Tech.
The C2 molecules are present in polymer vapor acMeeting. Switching & Protect. Eng., IEEJ, ED-11-065.
cording to the calculated equilibrium composition. In
SA-11-038, SP-11-011, 2011.
500550600
Wave length [nm]Radiation intensity [a.u.]

47rotvib

Calculated emission
coefficient [a.u.]450