These materials are really useful for situations where the system undergoes a switching action or a breakdown, such as a spark gap switch. In this switch, the two poles are separated by a short gap – when the voltage across the poles becomes great enough, an arc forms and the switch closes. The path of the arc itself can be modeled as a material with time-dependent conductivity – before the spark forms, its conductivity is essentially zero, while after ionization, its conductivity is massive.
In previous versions of CST STUDIO SUITE, this system would be modeled by treating the air gap as a lumped element switch in a transient/circuit co-simulation. Time-dependent conductivity materials offer an alternative approach, with several additional capabilities beyond those of lumped elements. For one thing, the switching response can be modeled. The arc doesn’t simply come into being suddenly, it forms over a time of about 300 ps. This effect is captured by the time-dependent conductivity material.
Modeling the spark gap in 3D also means that its actual shape – for example, the radius of the arc – can be taken into account. This means that the physics of the switch can be modeled more accurately by the simulation.
|A spark-gap switch, closed at 2000 ps.|