Arc root commutation from moving contacts in low voltage devices

Abstract

Abstract-This paper focus on the arc commutation from a moving contact and in particular on the anode motion of a high current arc in low voltage current limiting circuit breakers. Recent investigations have observed that the anode arc root motion is affected by arc chamber geometry. It was previously assumed that cathode root motion was the dominant process. The study uses a flexible test apparatus with a solid state high speed imaging system. The experimental results presented show the influence of arc chamber venting, current level, current polarity and contact velocity on arc motion. Particular emphasis is made to the anode motion. The physical process occurring in the anode root are discussed and related to the observed motion. The results show that the anode root is retarded at the tip of the moving contact and that this is primarily related to the venting process in the arc chamber.

Experimental study on the influence of vent aperture size and distribution on arc motion and interruption in low-voltage switching devices

“…The arc images (light intensity) inside the quenching chamber are recorded by using the AIS linked to a flexible test apparatus (FTA) [2], [5], [6]. The FTA is designed as the quenching chamber of a MCB and it is used to record arc motion under controlled test conditions.…”

“…Therefore, an understanding of detailed arc motion depending on the venting condition is important to design a product and improve switching performance. McBride et al conducted experimental studies of the influence of the vent size on the arc root time (the time period that the arc root remains in the contact region) by measuring arc motion in a miniature circuit breaker (MCB) through high speed optical imaging system [2]. They found that the arc root time decreases as the vent size increases.…”

Optical fiber imaging for high speed plasma motion diagnostics: Applied to low voltage circuit breakers

“…Fig.1. shows an example test chamber, used to investigate the relationship between contact opening velocity and the cathode and anode arc root dynamics as the arc transverses the arc chamber, [6][7][8][9]. The arc chamber is mounted in the horizontal plane, and is designed to simplify the geometry of a typical chamber.…”

“…An established method of arc root plotting allows for the definition of parameters, for example the time taken for the arc root to transfer from the moving contact to the fixed runner; such that physical variables, for example the materials used in the chamber can be investigated and compared, [4][5][6][7][8][9]. The method is based on an intensity based position averaging technique over selected fiber positions near the surface of the runners (shaded fibers in Fig 1).…”

“…In [3], gas analysis, pressure measurements, and post currentzero breakdown voltages were used to rank arc chamber wall material according to breakdown voltage. A previous optical 2 fiber based imaging system was developed in the early 1990's and was used in studies of arc motion, [4][5][6][7][8][9]. The system was limited to 500MHz sampling over a 8ms duration with 6 bit light intensity resolution.…”