Tuesday, April 15, 2014

Time Dependent Materials in CST STUDIO SUITE 2014

Our powerful time domain solver has long been one of our key strengths. In order to improve our transient simulation capabilities even further, CST STUDIO SUITE 2014 adds a new feature: time-dependent conductivity materials.

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.


  1. Hello,

    Now that this new feature of time-dependent conductivity has been added (regarding MWS transient solvers I presume), can models from EM Studio (with their static E field results) be imported into MWS so that the transient fields resulting from switching of the charged conductors can be simulated?

  2. Hello, Thanks for your comment. It would be best to ask this question via our official support channels: https://www.cst.com/Support/Login

  3. Can I know how did you make the spark gap?

    1. I wonder how did you use the time dependent function to generate this simulation

  4. I am hoping that CST will publish a whitepaper, application note, example problem or whatever, on their web site, which will explain in detail the use of this new feature to model the switching of charged conductors using a spark gap.

    I would like to know whether results from EMS (electrostatic fields of charged conductors) can now be imported into MWS as an initial condition, with the charged conductors then switched to ground for example.

    (BTW here is a full text paper (freely available) which discusses another approach to simulate switching of charged conductors: http://www.jpier.org/PIERM/pierm16/08.10102505.pdf)