Hi Vic,
> 2710w / 220v = 12.3a + 20% = 14.8 amps. Should I use 15 amp fuses or 20
> amp fuses? I presume that I should choose slow-blow fuses because of the
> peak repetitive current.
Peak repetitive current isn't a problem, because the thermal mass
of the element averages the current.
Slow-blow fuses handle overloads of many cycles, fractions of a
cycle peaks are not a concern with either slow or fast fuse type
when using higher amperage fuses.
Most fuses take a long time to fail at minor overloads. For
example, a 3AB type "fast-acting" 15 ampere fuse requires up to
60 seconds of *constant* overload at 200% to blow. Temperature is
also a problem. The rating on the fuse is for a certain temperature.
Put it in higher ambient, and it blows sooner.
Littlefuse recommends a 25% minimum margin at room
temperature to avoid nuisance blowing from fuse fatigue. That
means a 20 amp fuse in your case.
With a step-start circuit, a slow blow fuse isn't needed.
73, Tom W8JI
w8ji@contesting.com
--
FAQ on WWW: http://www.contesting.com/ampfaq.html
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
Search: http://www.contesting.com/km9p/search.htm
|