74 / 2024-04-10 15:22:27

Numerical Simulations of Arc Plasma Interaction with Polymer Wall during Decaying Process of Polymer Vapor Contaminated Arc

atmospheric air, polymer ablation, decaying process

In the process of current interruption in low-voltage circuit breakers (CBs), arc characteristics and interrupting performance are significantly affected by contaminants within the arc plasma. This situation arises when metals from the electrodes and polymeric materials from the arc extinguishing chamber vaporize and mix into the arc column, resulting in the arc igniting in a complex gas mixture rather than in pure air. To date, we have consistently calculated the thermodynamics and transport properties of polymer vapor, based on its particle composition, and have conducted numerical simulations to investigate both the arc ignition process and steady-state arc behavior. This paper aims to elucidate the impact of polymer vapor contamination on the arc decaying process, which is critical in determining the thermal interrupting performance of CBs.

Initially, we calculated the thermodynamic and transport properties of polymer vapors, focusing on polyamide-6 (PA6), polyacetal (POM), and polytetrafluoroethylene (PTFE). These polymers are commonly used in the nozzles and arc interruption chambers of CBs. Utilizing these properties, we performed electromagnetic thermofluid simulations on a one-side flow outlet model. The model's electrode configuration includes a pair of iron (Fe) electrodes, each with a diameter of 6 mm, and a polymer cylinder with an inner diameter of 6 mm. Simulations were first run for the arc in a steady state and then for the transient state by reducing the current to 0 A.



In our model, polymer vapor is ablated from the inner wall of the cylindrical polymer by the arc plasma's contact, contaminating and being exhausted into the outer space in the steady state. During the arc decaying process, just after the current down to 0 A, the rate of polymer ablation rather increases temporarily. This is because the high-temperature arc plasma, previously constricted by electromagnetic forces, spreads near the wall. The influx of air from the external environment decreases the concentration of polymer vapor inside the cylinder, gradually lowering the arc temperature. Intriguingly, during this period, the air influx occurs in a pulsating manner due to the repeated cycles of polymer ablation and subsequent cooling within the cylinder.