Arc Cross-section Determination of Convection Stabilized Arcs

Convection stabilized high current arcs are found in extinction chambers of AC and DC circuit breakers. Such arcs have a radially flat temperature profile with a sharp drop towards the surrounding cold gas. This is because a large fraction of the emitted radiation is reabsorbed at the edge of the arc column. Therefore, it is reasonable to characterize an arc of this type by its cross-section A. In this contribution, the crosssection of convection stabilized arcs in a model circuit breaker is determined separately by electrical measurements, optical high-speed imaging and the heating chamber pressure drop. The theoretically expected cross-sections increase with current (A ∝ i) and drop with blow pressure (A ∝ p). This was confirmed by all three measurement techniques. However, it became clear that light emitting, electrical and fluid dynamical cross-sections are ambiguous and do not always describe the same physical property.