"There was a HUGE argument between marketing
people and engineers relating to "UPS". Marketing called them
uninterruptable power sources (UPS) and engineers demanded they be
called Stand-By power sources(SPS). All the things you buy today are
really stand-by power sources. They have a real mechanical relay that
switches from the power line to battery source. A real UPS will cost
many hundreds to many thousands of dollars. They continually supply
power from batteries and the AC just keeps the batteries charged. An
electronic circuit keeps the internally generated AC synchronized to
the external power frequency. The marketing people finally won the
battle. Guess it was the money, not the truth."
One very knowledgeable cohort of mine used to speak of them as real UPS's and
During that time, I was project manager on a couple of large UPS installations,
both on PBX plants.
One was a 4000 line PBX and the other was 2000 line. They were Lorraine Electric
uninterruptible in every sense of the word, with huge lead-acid batterys. As I
recall the batts in
the 4000 line unit were sized for nominally 24 hours.
No, it isn't. A "true" GPS, be it motor-gen or otherwise, is not the genuine
animal unless it's
output is being generated constantly whether commercial power is present or not.
A motor-gen UPS
would not be fit the true GPS definition unless the generator ran constantly
from its source of
power, battery or commercial. In the "true" GPS, switching is implemented only
in the event of
primary power failure; and then only to interrupt or restore primary power to
the batteries charging
Robert Swinney wrote:
In my working days in radio telcomm. UPS was composed of battery bank,
motor-generator set and control(switching) unit. I don't recall we ever
suffered radio link outage. This is true UPS.
SSR's generally use SCR's, which have the property that they don't turn
off until the current is interrupted. Normal 60 Hz power turns off 120
times a second. But, when you tell the thing to turn off during a
surge, it will totally ignore the command because the current is still
Really high-end UPS's do use fancy devices like back-to-back giant
IGBT's, but most probably just use an electro-mechanical relay, and are
designed to supplement dropped line power, not protect the load. There
are "on line" UPS's that only use electromechanical relays to bypass a
failed inverter, and otherwise all connection from input to output is
through the DC battery bank. These are usually pretty expensive
(thousands of $ for a small one) noisy and waste a lot of power, too.
Note the microseconds. Relays take thousands of microseconds to
Here's a traditional answer:
TV repairmen used them to make hot-chassis sets safer to work on. I
have one but use a UPS instead.
On Sat, 20 Mar 2010 10:57:42 -0700 (PDT), Jim Wilkins
What you need to make working on a hot chassis safer is an isolation
Many power conditioners use one, but electronic service technicians
usually use a Variac, which is an isolation transformer that has a
variable output control. Useful for "bringing up" voltage gradually
for various purposes, in addition to the safety it provides.
or as an alternative:
The Variac is available with higher current capability than the B&K,
so it is preferred by people who work on big TV's and commercial sound
often,the "protected" parts are faster to blow than the protection device.
there are specs on how fast such protection has to operate.
It's a few nanoseconds.
also,how much energy)in joules) that it must be able to shunt or absorb.
Often,the strike is way more than the device can tolerate.
I've seen MOVs that has absorbed a lightning strike and blew apart,yet the
power supply itself survived.All it needed was a new fuse and cleaning the
blown MOV's metal deposits off the PCB.
The standard protectors are tested against is the so-called 8/20 surge,
the 8 means an 8 MICROSECOND rise time. So, the current rises to it's
peak value in 8 us, then decays in 20 us after that. Relays take many
milliseconds to react, and a lightning surge will just jump right over
the open contacts, anyway. So, totally FORGET anything using relays.
Either you buy a protector that will somehow absorb all that
energy. Or you buy protectors based upon how it was done even 100
years ago. Protection is always about where energy dissipated.
Either that energy remains outside the building. Or that energy is
inside hunting for earth ground destructively via appliances.
Adjacent protectors simply give surges even more potentially
destructive paths through adjacent appliances.
An effective surge protector means even the protector remains
functional. A minimal 'whole house' protector starts at 50,000 amps.
Direct lightning strikes are typically 20,000 amps. Yes, the
protector must be sized to even earth direct lightning strikes and
remain functional. And that means the connection to earth must be
additional requirements - short ('less than 10 feet) to earth, no
sharp wire bends, no splices. all protectors meet at (again 'less than
10 feet to') the single point earth ground, ground wires separated
from other non-ground wires, not inside metallic conduit, etc.
Protection is always about where energy dissipates. If those
hundreds of thousands of joules dissipate in earth, then no damage.
This is how it was done even 100 years ago.
But somehow a magic box next to the appliance will absorb all those
joules? Always view the tech specs. Plug-in protectors rates at
hundreds of joules will somehow make hundreds of thousands just
disappear? That is what they claim. In analysis, we even traced
surges earthed destructive through a network of powered off computers
because the surge was permitted inside the building. And because a
surge on the black (hot) wire was connected directly to the
motherboard by the protector. The protector bypassed protection
inside the computer's power supply.
Telcos do not waste money on protectors adjacent to electronics.
That switching center must never suffer damage. A switching center,
connected to overhead wires all over town, may suffer 100 surges with
each thunderstorm - and no damage. Why? Each protector connects
short to the single point earth ground. And the protector is up to 50
meters separated from electronics. That separation increases
No protector is protection. None. The only effective protectors
make that short connection to single point earth ground. Ineffective
protectors (a $3 power strip with some ten cent protector parts
selling for $25 or $150) are profit centers. The NIST (US government
research agency) discusses those ineffective protectors by describing
what every protector must do:
The NIST describes plug-in protectors as "useless". Obviously. It
does not even claim protection in its numeric specs. Find those spec
numbers that list each type of surge and protection from that surge?
No plug-in protector makes protection claims. They are a profit
Protection is always about where energy dissipates. IOW why
facilities with effective protection both meet and exceed post 1990
National Electrical code. Where does energy dissipate? A protector
is only as effective as its earth ground - which no plug-in protector
has and therefore will not discuss. Effective 'whole house' protectors
come from General Electric, Keison, Intermatic, Siemens, Square D, and
Leviton. An effective Cutler-Hammer solution sells in Lowes and Home
Depot for less than $50.
How bout a surge from downed power lines? Ours got knocked down from
ice on trees falling on the main lines into the house 4am Christmas
eve. Started a fire (12" flames) on the Belkin UL approved spike/
surge protector right next to the christmas tree & plasma TV! Could
never get an answer as to why this happened. Knocked out a couple
other surge strips including a plug in CO2 detector.
Thank god thats all that happened.
Must be something to do with the end of the power- where it
While I was staying in a motel in Southington, CT an
empty room burned.
Smoke detector started the fire. Melted & dripped flaming plastic
on the bed ....
(Had central wiring back to the office & was poorly
A friend suffered a 33,000 volt fault to the local distribution. As
a result, hundreds of electric meters were blown from their pans. At
least 100 clear plastic meter covers in pieces 10 meters from the pan.
Many neighbors suffered damaged electronics and protectors similar
to yours. Fortunately, no fires. At least one neighbor had a
destroyed 20 amp circuit breaker.
But my friend knows someone who knows this stuff. He only had a
'whole house' protector installed. Therefore he had no damage other
than an exploded meter. Even the 'whole house' protector remained
Just another reason why informed consumers earth one 'whole house'
protector and do not made money on plug-in protectors. That Belkin
does not even claim protection in its numeric specs.
BTW, electric company was not responsible for any damage (as
expected). Many electric customers had their meter pans completely
replaced due to the explosive power in that 33,000 volt fault.
I have not noticed that w is a reliable source of what happens. Perhaps
you could provide a newspaper article?
MOVs are the basic protection components for virtually all power circuit
surge suppressors. A MOV that can easily handle a 33,000V surge for 100
microseconds is rapidly burned out by a crossed power line ("temporary
overvoltage", not a "surge"). Suggesting that a service panel suppressor
will provide protection is idiocy.
Provide a spec from any manufacturer that their suppressor protects from
crossed power lines.
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