DC Arc Properties in a DC Magnetic Field

The effect of a transverse magnetic B-field on the arcing properties of a 10A
_dc
arc in a 380V
_dc
system was investigated. ANSYS MHD software was used to compare the simulation results of the arc (i.e. plasma) with and without an external transverse magnetic field applied. The model revealed that convective cooling was the primary mechanism for arc cooling, but while the model showed dual vortices in the convective flow pattern, the experimental results showed a more turbulent flow pattern. The experiment consisted of copper rails and fuse wire used to replicate switching contacts. A circuit at 380V
_dc
was used to create a 10A
_dc
arc between the ends of the rails. Arc voltage and arc clearing time were measured with and without an externally applied transverse magnetic field. Comparisons with the model indicate that convective forces created turbulence that led to lower arc conductivity and subsequently faster clearing times when a magnetic field was applied to the arc. A 50mT transverse magnetic field applied to a 10A
_dc
arc between copper rails resulted in average clearing times of about 4ms as compared to an average clearing time greater than 150ms without a magnetic field applied. These results can be used to guide the development of new DC arc protective switches.