In message <BE4DD94CEBC14A02A9E892663A919837@lashko>, dated Tue, 12 Mar
2013, =?iso-8859-1?Q?H. K=F6ster?= <[email protected]> writes:
A lightning stroke does not know if a unit with 3pole plug (with PE) or
with 2pole plug (without PE) is connected to the wall outlet.
Indeed, but indirect lightning-induced surges are **common-mode** - they
occur simultaneously and equally on L and N. So if such a test is
required, L and N must be connected together. The test is not realistic
if it applied to L alone or N alone.
So in my opinion this surge test between L and PE and between N and PE
should be done in any case also for such class 2 power supply units
with double insulation as evidence for a certain degree of immunity.
Even if the test is applied to L and N connected together, it's not
realistic, for most Class II products, to stand them directly on an
earthed metal plate. A spacing of a metre from a ground plane would be
more realistic.
--
OOO - Own Opinions Only. See www.jmwa.demon.co.uk
SHOCK HORROR! Dinosaur-like DNA found in chicken and turkey meals
John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK
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