Break arc study for the new electrical level of 42 V in automotive applications

In order to fulfil increasing need for electric power in automobiles, satisfy environmental requirements and decrease car weight, the supply must change from 14 V to 42 V. In this work using 42 V, we studied arc parameters such as break arc duration and extinction gap for different materials, contact opening speeds and circuit loads (correlated with circuit time constant L/R). We found that these main arc parameters are greatly enhanced compared to the 14 V arc. In the case of inductive or resistive load, it was found that there are two domains: a low current domain where the material has no significant effect, and a high current domain where some materials (primarily AgSnO/sub 2/) induce high arc durations and large extinction gap. In addition, increasing opening speed reduces arc duration in all cases. The increased opening speed can however increase the extinction gap for inductive loads and decrease it for resistive circuits. We found that reducing arc duration is always beneficial with regards to erosion, but in some cases it may increase the extinction gap. At 42 V, erosion and material transfer from cathode to anode are similar to that found at low extinction gaps (<1 mm) at 14 V. At large extinction gap, however, these transfer phenomena are considerably modified by a new mechanism that induces erosion of the cathode and anode. It was found that classification of material behavior versus erosion is different at this voltage. For example AgSnO/sub 2/, which is claimed as a best compromise at 14 V for all loads, cannot be used at 42 V as it exhibits high erosion and requires a larger contact gap to ensure successful break.