Coupling of Magneto–Hydrodynamics and Structural Models to Predict Wall Deformation due to Arcing

Electric arc discharges in low–voltage (LV) or medium–voltage (MV) power distribution devices can cause significant pressure rise. For example, a high amplitude pressure peak can damage the housing of a LV circuit breaker initiating cracks during short circuit interruption. In case of larger deformations or creation of additional gaps, the impact of the geometric changes on the pressure rise cannot be neglected. This article describes a new three–codes–coupling approach, wherein a magneto–hydrodynamics (MHD) model consisting of a fluid–flow solver and an electromagnetic solver are coupled with a structural dynamics solver to build a complex co–simulation model. This model can predict the deformation of structures under the influence of arcing pressure. The applicability of the model was tested with a setup, where an electric arc is ignited inside an arc chamber that has a flexible plate on one side. Predicted pressure rise and displacement results are in good agreement with test data. In a more complex setup, this approach was applied to model the bending of a flexible baffle plate in the venting path of a LV circuit breaker during short circuit interruption. Additional challenges such as contact motion and pre–stress analysis were resolved.