"Colin Birch" wrote in message
.. .
Hi folks and thanks for the replies. I'm still looking for a bit of basic
info though. I'm confused by the two terms Max AC voltage rating and
Clamping voltage. If the switch mode psu is running off 240V and I want to
limit the input voltage to 250/260V do I need a maximum AC voltage rating
of 260V or a clamping voltage of 260V? Seems a bit confusing for a novice


One of the manufacturers makes life easy by selling 275VRMS MOVs for 240V
mains use, I've found 1100V MOVs in some Nokia monitors.

The more current technology; transorbs might be the way to go, but since
they're more likely to fail S/C you should aim for the highest voltage your
equipment can comfortably survive.

Your first port of call should be the datasheet/appnote area of a
manufacturer's website - ISTR Littlefuse make surge protectors and have at
least acceptable tech info.