In message
<64D32EE8B9CBDD44963ACB076A5F6ABB0262A557@Mailbox-Tech.lecotech.local>,
dated Wed, 21 Nov 2012, "Kunde, Brian" <[email protected]> writes:
So what a part is rated and how it is protected is often not clear to
me.
I suggest you look at a different approach. What matter is whether there
is a safety issue, not whether some particular current is exceeded. For
example, I recently had an audio amplifier to repair for a friend. It
had caused the supply fuse to operate, but the resistance between the
supply pins on the plug was OK. So I plugged it in and switched on at
the wall socket. The mains switch on the product exploded, due to
previous overheating and carbonization.
The prospective short-circuit current from that outlet is 600 A. The
appliance connector and the mains lead were completely unharmed, showing
no signs even of superficial damage.
So, no safety issue. No worries.
On the other hand, a while back I had a low-power product to assess for
safety which had a F1 A mains fuse but a 20 W mains transformer (some
few products still don't have SMPS). I put a short circuit on the 12 V
DC supply and the product sat there steaming until I took pity on it.
The 1 A fuse was thought to be necessary to prevent operation on inrush
current, but a T100 mA fuse was far more suitable and operated quickly
when the DC supply was short-circuited.
--
OOO - Own Opinions Only. See www.jmwa.demon.co.uk
The longer it takes to make a point, the more obtuse it proves to be.
John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK
-
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