Carriage bolt spark gap equation

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Original poster: "Rothman, Aric by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Aric.Rothman-at-Honeywell-dot-com>

In the course of hi-pot testing some capacitors, I also took the
opportunity to measure the DC breakover potential for
the 1/4" thread carriage bolt safety gaps which protect the capacitors.  I
used a hi-pot testing station which generates
DC voltages to 35kV.  Over the range of 4500V to 20,000V, the relationship
of gap spacing to voltage was very linear.

The equation I derived from the data is:

 gap spacing (inches) = 1.338 V + 0.0257, for Voltages from 4500V to 20,000V


Perhaps this equation will prove useful for those who use these types of
carriage bolts for building safety gaps and the
like.

Aric