Mark, Brian et al,
Without trying to deal with all of the issues that this question
raises, I would like to comment on just one aspect from my experience.
In the North American distribution system the short circuit current
that can be expected from the usual 115V domestic & commercial outlet is on
the order of 7000A. Because of this fuses and circuit breakers providing
protection for these circuits must comply with a 10,000A breaking capacity.
In my other life I remember testing a current measurement product
subjected to this 10kA current which produced a surprising failure that
provided ionized/arcing fire from the front panel which ate up the 3AG
instrumentation fuse proposed along with the panel connector and several
inches of the lead wire coming into the product. Needless to say the design
engineer then recognized the inadequacy of the small fuse and designed the
product to accommodate the proper breaking capacity fuse (which was quite a
bit larger). Experience is a great teacher; unfortunately we sometimes
forget too fast.
br, Pete
Peter E Perkins, PE
Principal Product Safety & Regulatory Consultant
Tigard, ORe 97281-3427
503/452-1201 fone/fax
[email protected]
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