Investigation of Temperature Fluctuation of Diode-Rectified Multiphase AC Arc by High-Speed Visualization

Manabu Tanaka,Takayuki Watanabe,Yuta Kugimiya,Hiroki Maruyama,Tsugio Matsuura,M Shimada

doi:10.1051/matecconf/202133303005

Abstract

An innovative multiphase AC arc was drastically improved by diode-rectification technique with bipolar electrode. Temperature fields and arc behaviour of the diode-rectified multiphase AC was successfully visualized on the basis of the high-speed camera technique with appropriate band-pass filter optics. Arc temperature was measured by Boltzmann plot method with two line emissions from atomic argon at 675.2834 nm and 794.8176 nm. Arc temperature fluctuates in the range from 7,000 to 13,000 K. The arc temperature near the cathode was higher than 13,000 K, while that near the anode was about 10,000 K. Arc temperature in the centre region in the furnace was about 7,000–9,000 K, which is sufficiently high to melt and evaporate the refractory metals or ceramics. Obtained results suggested the diode-rectified multiphase AC arc is a promising thermal plasma source for material processing at high productivity.

Highlights

A multiphase AC arc (MPA) is one of the most attractive thermal plasma sources due to its advantages such as higher energy efficiency compared with conventional thermal plasmas
Arc behaviour in Diode-rectified MPA (DRMPA) was observed by high-speed camera system without band-pass filters
The results indicated that the temperature of the both MPA and DRMPA were fluctuated in the range of 7,000 K to 13,000 K

Summary

Introduction

A multiphase AC arc (MPA) is one of the most attractive thermal plasma sources due to its advantages such as higher energy efficiency compared with conventional thermal plasmas. Appropriate properties for cathode and anode in arc discharge are different. Low work function and high melting point are important cathode properties for stable electron emission. High thermal conductivity is required for anode as electron recipient. There is a lack of appropriate electrode material which satisfies required properties at both cathodic and anodic periods. Tungsten based electrode are commonly used as AC electrode for stable thermionic emission, the thermal conductivity is insufficient. This fact led to severe erosion in conventional single-phase AC arc (Hinata et al, 1993) and MPA (Hashizume et al, 2015)

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