Abstract
Transfer switches for future HVDC systems can be based on passive oscillation principle to create a current zero crossing. The principle relies on a negative differential arc resistance of the mechanical switch. Present investigation aims to understand and quantify under which conditions the is negative. For this, results from electrical arc measurements are compared to results from a 1D arc model. Based on this, the authors conclude that ablation is not the reason for non-negative . In fact it is rather the location of the smallest arc radius which determines the negative characteristic. As soon as the turbulent shear layer is thick enough compared to the total arc diameter that it influences the temperature at the arc center, the turns negative. The current at which this happens scales with p 2/3, can be influenced by the nozzle shape and is rather insensitive to the chosen type of blowing gas.
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