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re: cable sizes
15 mar 1997
redwood kardon wrote:
>> >>us wire gauge metric mm^2 fusing current
>> >>------------- ------------ copper tin
>> >> 6 13.3 668 amperes 107
>> >> 8 8.4 472 76
>> >> 10 5.3 333 53
>> >> 12 3.3 235 38
>> >> 14 2.1 166 27
>> >> 16 1.3 117 19
>> >> 18 0.82 83 13
>fusing currents is a new term for me. am i correct to assume a "fusing
>current" is the amperage that will rupture a particular gauge? is this a
>common term in the pv world?
i've heard a 15 amp glass fuse will "rupture" (breaking the glass envelope)
at about 25,000 amps.
the itt book says
the current i in amperes at which a wire will melt can be calculated from
i = k d^1/2, where d is the wire diameter in inches and k is a constant
that depends on the metal concerned. table 39 gives the fusing curents in
amperes for 5 commonly used types of wire. owing to the wide variety of
factors that can influence the rate of heat loss, these figures must be
considered as only approximations.
they give k=10244 for copper, 7585 for aluminum, 3148 for iron and
1642 for tin. no mention of lead wire, which is still used for fuses
in france. supermarkets sell little cards with a few inches of 5 amp,
10 amp and 15 amp wire. when a "fuse" blows in an old house, you go
downstairs, flip off the main switch and attach some more fuse wire
between the binding posts. france started out with 110v years ago, and
when people wanted more power, edf doubled the voltage to 220 :-)
nick
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