# DC arc flash calculator

#### Electrode Material

Currently, the online DC arc calculator is limited to copper electrodes only. It was found that, when current is not too low, voltage of an arc in open air with copper electrodes is determined by the anode, cathode drops of approx 30V, and positive column voltage drop of the order of 10V/cm. Consider ARCAD DC Arc Flash Analysis and Labeling Software capable to solve arc flash equations for a variety of different electrode materials including copper, aluminum, steel and their combination.

#### Gap between Electrodes

Distance between electrodes. It determines voltage drop across positive column. The voltage drop across the positive column is proportional to its length, a few volts per centimeter. Leave this field blank if gap value is not known or spacing between anode and cathode is anticipated to increase by the separation of the contacts. If this field has been left blank, the calculator will determine maximum energy that can be released by an arc for given circuit parameters and calculate incident energy and flash protection boundary based on it.

#### Circuit Time Constant

Measure of DC circuit inductance. Circuit Time Constant is used to determine arc duration based on circuit protective device time-current characteristics under DC transient conditions. Published fuse time-current characteristics show the time required for a fuse to clear the fault under different RMS load currents. However, under DC short circuit conditions, the effective RMS current is much different from the instantaneous current under DC short circuit conditions and the published fuse AC time-current characteristics cannot be used for DC applications. The time current characteristic curve that will apply for a specific DC application depends on the specific time constant. When circuit time constant is specified within 0 to 50 milliseconds range, the calculator will take care of converting a time current curve to DC curve and determine arc duration based on it and on the amount of arcing current.

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10/15/2015

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11/23/2014

10/16/2014

09/23/2014