w_tom wrote:
In the meantime, a microsecond (and destructive) transient
has already damaged electronics while in-line fuses take
milliseconds to blow? There is no inline fuses on plug-in
protectors to disconnect the appliance. Furthermore fuses
don't protect from transients.
In the 80s I had modems protected only by tiny fuses that blew very
fast. I quit blowing fuses when I got a good plug-in suppressor.
I don't know about every surge protector, but a standard simple design
has a fuse, a shunting MOV, an inductor, and the load. If the MOV blows
the fuse, the load is disconnected. Meanwhile, the inductor blocks transients.
Fuses disconnect damaged electronics from the AC mains for
human safety - so the house does not burn down. That is also
the function of a fuse on surge protector circuits. Fuse
disconnects a vaporized or shorted protector; while appliance
remains fully connected and exposed to the transient. Fuse
only disconnects the MOV - not the appliance. (This MOV fuse
should not be confused with the larger 15 amp breaker.)
I have one surge protector which instantly disconnects the load with
even tiny transients. It crashes my computer several times a month.
Another suppressor of mine has five MOVs, six diodes, two glass fuses,
two special-purpose fuses, two resistors, a transistor, a transistor
wired as a diode, and a capacitor.
A plug-in protector puts no fuses in series with the load.
And those inductors? Application notes from MOV manufacturers
recommend those inductors only to protect the MOVs. Smaller
MOV then can withstand slightly more energy. Those inductors
are ... well again the numbers ... are insufficient inductance
as load protection. Furthermore, an electronic appliance
already has a superior line filter inside its power supply -
to meet FCC requirements. The inductor in a power strip
protector - if it even exists - is not for appliance
protection.
How much inductance does it take to protect an appliance from a
1-microsecond transient? Are you saying the FCC requires lightning protection?
Previously cited was a damaged TV and stereo; and an
undamaged damaged computer. Assumed was that all had equal
internal protection. The TV need only meet the 600 volt
standard (posted previously). Computer power supplies must
withstand voltages in excess of 1000 volts - as even demanded
by Intel specs. So a transient large enough to overwhelm 600
volt protection inside a TV could not overwhelm the 1000 volt
protection in a computer power supply. Where does that
damage prove a computer protector with too few joules did
anything? It does not. And again, with or without the
plug-in protector, the computer was connected directly to AC
mains. More likely, the computer protected itself.
I don't have an Intel computer. Where would I find the requirements for
*my* computer?
BTW, also mentioned was a grounded receptacle. No earth
ground exists at that wall receptacle. Wire impedance (and
other electrical concepts) means a receptacle has all but no
earth ground. Another critical expression was posted that
examples the concept - 'less than 10 foot' connection to earth
ground. Wire distance and other factors inside wall wires
conspire to make that receptacle safety ground not an earth
ground. No earth ground is why plug-in protectors are not
effective.
Wrong. A whole-house protector won't ensure that the ground at each
receptacle in a house will stay at the same potential when lightning
strikes. OTOH, whether or not you have a whole-house protector, if all
computer equipment that's connected together is supplied through the
same plug-in surge protector, it will all have the same ground when
lightning strikes.
I can appreciate why you might think the plug-in protector
effective. But principles of junior high school science
apply. A fact must be proven both theoretically and
experimentally. Your example contradicts well proven theory.
And numbers for internal appliance protection explain why one
appliance may be damaged while the other not damaged. You
example does not demonstrate the plug-in protector did
anything effective.
My example contradicts well proven theory? Then the well proven theory
must be that a computer plugged into a surge protector will blow and a
TV plugged directly into an outlet won't blow.
In the meantime, protectors are for destructive transients
that occur in microseconds - transistor protection. Fuses and
circuit breakers are for milliseconds events and longer -
human protection. Transistor protection means the protector
is only as effective as its earth ground which is why one
'whole house' protector is so effective.
I had whole-house protection when my TV and stereo blew.
In the meantime, none of this would solve or address the
strange light flickering.
I talked to people from a fourth house on our transformer. They weren't
home at the time, but they had to reset everything when they got home.
I also talked to the lineman. He likes whole-house protectors, but he
says a lightning arrester is more important. For a small fee the power
company will hook one to your meter. You can tell at a glance if it's okay.
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