Jim Yanik wrote:
"William Sommerwerck" wrote in
:

"Cydrome Leader" wrote in message
...
William Sommerwerck wrote:
Many years ago, PC and/or Byte (I forget which) used to test
suppressors.
If they failed to provide suppression, I assume the mag would have
said
so.

Hilarious, PC magazine is your source for the lowdown on surge
supression
devices?
It was, 20 years ago. I don't think you get the point, though.
So what is the point? John Dvorak wrote a story about surge
supressors and how they worked with his Cumulus 386 laptop and his
CompuAdd 486sx tower?
The point is that they were performing lab tests on the suppressors.
These tests included determining the clamping voltage. (I don't
remember if they were tested to destruction.) The tests were
presumably performed in accordance with industry-accepted standards.




"clamping" is a misuse of the word WRT surge protectors.
It misleads people,as in "david" s post.

"trigger voltage" might more accurate.

MOVs have a smooth, but nonlinear, curve from not conducting at low
voltage to high conduction current at higher voltages. They do not
"trigger" like a neon light. And the voltage across the MOV does not
suddenly decrease, like it would in a neon light (you probably didn't
say it did). "Clamping" is a widely used term, including the wiki
article on MOVs. (Gas discharge tubes are like a neon light, and do
trigger.)

One of the parameters for a MOV is MCOV (maximum continuous operating
voltage) which is the voltage at which the current is 1 mA. The
increase in current is smooth (but very non-linear) above the MCOV, just
like it was smooth (and non-linear) below the MCOV.

(When the MCOV for a MOV decreases 10% it is the defined end of life for
a MOV - referred to in the wiki article.)

A MOV is very much like back-to-back Zener diodes, but does not clamp as
sharply. But MOVs have huge current capacity in a small package.

The clamp voltage that is usually cited is the UL let through voltage
(UL calls it something a little different). This is the voltage at a
specified test surge current. If the surge current goes up, the let
through voltage will be higher (in a non-linear way).

--
bud--