Simulation of arc-circuit instability in a low current DC automotive switching application

The dynamic arc produced in a switch breaking an inductive load sometimes interacts with the rest of the circuit to produce a highly nonlinear response characterized by growing, high frequency oscillations, current chopping and transient overvoltages. System simulation, therefore, requires an approach that includes switch arc behavior. A technique for employing a well-known equation from power circuit breaker design to analyze such arc-circuit interaction for switch arcs of less than 2 mm in length is described. The so-called Mayr arc equation provides a basis for accurate modeling of arc-circuit instability after one recognizes that the drawn switch arc exists in two distinct phases, for which the mechanisms of arc erosion and instability are effectively decoupled. This approach provides a technique for predicting instabilities in switched automotive electrical systems that could result in either radiofrequency interference to vehicle electronics, or potentially damaging high voltage transients