New Arc Stability Index for Industrial AC Three-Phase Electric Arc Furnaces Based on Acoustic Signals

Abstract

This research proposes a new index to evaluate the stability of the melting process, in three-phase electric arc furnaces (EAFs), based on the acoustic signals generated during the different stages of the casting. The proposed stability index is obtained by characterizing the time and frequency domain of the acoustic signals. During EAF monitoring, acoustic signals were acquired using a microphone coupled to an NI USB-9234 acquisition system. To validate the results, the voltage and current signals were measured with the aid of a Circutor AR6 power analyzer for three-phase electrical networks. The results showed that the acoustic signal energy in the frequency range of 1 to 12 kHz can be used as an indicator of the process stability in the EAF. Finally, the validity of the proposed stability index is evaluated from the process characterization using the harmonic distortion analysis methods and the dynamic U-I characteristics of the arc voltage and current signals. The results obtained demonstrated the effectiveness of the proposal and constitute a starting point for advances in the automatic control of the process in the EAF, from the acoustic signals.

Arc Quality Index Based on Three-Phase Cassie–Mayr Electric Arc Model of Electric Arc Furnace

“…Conversely, stable arcs enable higher power output, resulting in shorter tapping times, higher productivity and steel quality [15]. Various methodologies have been used to evaluate arc stability, including analysis of secondary-side transformer voltages or line currents [14][15][16] and the evaluation of acoustic signals [17]. An important stability indicator in the frequency domain is the THD of the voltage or current signal [16].…”

“…Martell et al [15] introduced a stability index based on the RMS voltage between virtual neutral voltage of the EAF delta transformer and ground voltage. In addition, arc stability can be evaluated by analyzing acoustic signals, where a stability index is derived by examining both the time and frequency domain of these signals [17]. Arc stability is not only a reflection of the electrical behavior in the furnace, but also a crucial process variable that, together with the specific heat stage, determines the EAF's operational power level.…”