Variac

[Bob Groh WA2CKY]

Three comments here:
1.  Placing a fuse in series with the capacitor implies connecting the fuse in a high voltage dc circuit and that would, at a minimum, require a special kind of fuse - one rated for the appropriate dc voltage and capable of handling the required fault current. Breaking a DC circuit (more than 30 VDC or so) requires special arc quenching mechanisms. Not always easy or desirable.

2.  As someone else noted, a fuse in the transformer primary circuit will achieve the same purposes.

3.  In any event, a failing  capacitor might not cleanly fail in a 'shorted' condition but might simply go to a low impedance state (i.e. pull extra current) which will not necessarily blow a fuse but will, given enough time, fry the transformer.  Again don't ask how I know this but I have a fried transformer to prove it happens!

Bob Groh

----- Original Message ----
From: Jim Bowman <jimbowman at SEANET.COM>
To: BOATANCHORS at LISTSERV.TEMPE.GOV
Sent: Friday, February 1, 2008 3:37:41 PM
Subject: Re: [BOATANCHORS-TEMPE] Variac


I 
have 
wondered 
of 
it 
is 
possible 
to 
insert 
a 
fuse 
of 
some 
kind
(slo-blo?), 
that 
would 
handle 
the 
normal 
surge, 
in 
series 
with 
the 
caps
connections 
so 
that 
the 
fuses 
would 
blow 
if 
the 
caps 
ever 
shorted, 
and
would 
prevent 
damage 
to 
the 
transformer, 
etc?

73,

Jim 
W7HPK






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