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| UPS FAQ Uninterruptible power supply Frequently Asked Questions |
| See Glossary for additional information about UPS terms |
Users of UPS systems will find here answers to the most popular questions about
Uninterruptible Power Supplies as well as applications of these systems.. This article is
courtesy of Mr.Nick Christenson from Jetcofe.org. Please see details at the end of the article.
Blackout
Complete loss of power. Some literature considers a voltage drop below about 80V to be a
blackout as well since most equipment will not operate below these levels.
Sag or Brownout
Decrease in voltage levels which can last for periods ranging from fractions of a second to
hours. Can be caused by heavy equipment coming on line such as shop tools, elevators,
compressors etc. Also occurs when utility companies deliberately do this to cope with peak
load times.
Spike
A tremendous increase in voltage over a very short period of time often caused by a direct
lightning strike on a power line or when power returns after a blackout.
Surge
A substantial increase in voltage lasting a small fraction of a second, often caused when high
powered appliances such as air conditioners are switched off.
EMI/RFI Noise
Electromagnetic Interference and Radio Frequency Interference. Caused by, inter alia,
lightning, generators, radio transmitters, industrial equipment.
MOV
Metal Oxide Varistors are added to circuits in order to control spikes. These are common in
Power Strips. If you see more than two, you likely have a fairly decent Power Strip. They
look like largish disk capacitors.
Inverter
Circuitry that converts DC battery power to AC power required by most computer equipment.
Surge Protector
Circuitry consisting of MOVs, capacitors, rod-core inductors etc. For suppressing surges
and spikes usually embedded in a power strip.
Line Conditioner
A transformer that attempts to smooth out fluctuations in input voltage to provide near
uniform output voltage or voltage waveform.
Topic: What is a UPS, how does is work, how does it help?
Q: What is a UPS?
A: An Uninterruptible Power Supply is a device that sits between a power supply (e.g. A wall
outlet) and a device (e.g. A computer) to prevent undesired features of the power source
(outages, sags, surges, bad harmonics, etc.) from the supply from adversely affecting the
performance of the device.
Q: Can you give me some more information on the UPS industry?
A: The industry is made up of many manufacturers, and there is a lack of standard terms
within the industry. I think this sometimes borders on deliberate misdirection. (It's a jungle
out there!) [ Note, in recent years the whole industry seems to have gotten better, at least
mostly agreeing on what the terms listed here mean. This is not true everywhere, but things
are getting better. ]
There are basically three different types of devices.
Standby power supply (SPS). In this type of supply, power is usually derived directly from
the power line, until power fails. After power failure, a battery powered inverter turns on to
continue supplying power. Batteries are charged, as necessary, when line power is available.
This type of supply is sometimes called an "offline" UPS.
The quality and effectiveness of this class of devices varies considerably; however, they are
generally quite a bit cheaper than "true" UPSes. The time required for the inverter to come on
line, typically called the switchover time, varies by unit. While some computers may be able
to tolerate long switchover times, your mileage may vary. [ Some articles in the trade press
have claimed that their testing shows that modern PCs can withstand transfer times of
100ms or more. Most UPS units claim a transfer time to battery of about 4ms. Note that even
if a computer can stay up for 100ms, it doesn't mean that 100ms switchover is okay. Damage
can still be done to a computer or data on it even if it stays up. ]
Other features to look for in this class of supplies is line filtering and/or other line conditioners.
Since appliances connected to the supply are basically connected directly from the power line,
SPSes provide relatively poor protection from line noise, frequency variations, line spikes, and
brownouts.
Some SPSes claim to have surge/spike suppression circuitry as well as transformers to
"boost" voltage without switching to the battery if a modest voltage drop occurs. Often, as a
"standby" UPS becomes more feature full it is called a "line interactive" UPS.
Hybrid [or ferroresonant ] systems. I only know one vendor who sells them - Best Power Inc.
[ Now called Eaton Powerware. Note that Powerware also sells line interactive and online
UPSes. ] The theory behind these devices is fairly simple. When normal operating line power
is present, the supply conditions power using a ferroresonant transformer. This transformer
maintains a constant output voltage
even with a varying input voltage and provides good protection against line noise.
The transformer also maintains output on its secondary briefly when a total outage occurs.
Best claims that their inverter then goes on line so quickly that it is operating without any
interruption in power. Other vendors maintain that the transition is less than seamless, but
then again it's not in their best interest to promote Best's products.
[ Note: According to some sources, ferroresonant transformers in an UPS system can interact
with ferroresonant transformers in your equipment's power supply and produce unexpected
results. On the other hand, ferroresonant systems don't kick off a lot of heat, which is
important in some environments. The Moral: Test equipment to make sure it meets your needs
before you buy. -npc ]
What I call "true" UPS systems, those supplies that continuously operate from an inverter.
Obviously, there is no switchover time, and these supplies generally
provide the best isolation from power line problems. The disadvantages to these devices are
increased cost, increased power consumption, and increased heat generation. Despite the fact
that the inverter in a "true" UPS is always on, the reliability of such units does not seem to be
affected. In fact, we have seen more failures in cheaper SPS units. [ Note, though, that given
the same quality inverter,
you'd expect the one that runs least to last longest. These devices are often called "online"
UPSes. ]
Q: How can it help me?
A: UPS has internal batteries to guarantee that continuous power is provided to the equipment
even if the power source stops providing power. Of course the UPS can only provide power
for a while, typically a few minutes, but that is often enough to ride out power company
glitches or short outages. Even if the outage is longer than the battery lifetime of the UPS, this
provides the opportunity to execute an orderly shutdown of the equipment.
Advantages:
Computer jobs don't stop because the power fails.
Users not inconvenienced by computer shutting down.
Equipment does not incur the stress of another (hard) power cycle.
Data isn't lost because a machine shut down without doing a "sync" or equivalent to flush
cached or real time data.
Q: What sort of stuff does a UPS do?
A: UPS traditionally can perform the following functions:
Absorb relatively small power surges.
Smooth out noisy power sources.
Continue to provide power to equipment during line sags.
Provide power for some time after a blackout has occurred.
In addition, some UPS or UPS/software combinations provide the following functions:
Automatic shutdown of equipment during long power outages.
Monitoring and logging of the status of the power supply.
Display the Voltage/Current draw of the equipment.
Restart equipment after a long power outage.
Display the voltage currently on the line.
Provide alarms on certain error conditions.
Provide short circuit protection.
Q: How long can equipment on a UPS keep running after the power goes?
A: That depends on how big a UPS do you have and what kind of equipment it protects. For
most typical computer workstations, one might have a unit that was rated to keep the
machine alive through a 15 minute power loss. If it is important for a machine to survive
hours without power, one should probably look at a more robust power backup solution that
includes a generator and other components.
Even if a UPS powers a very small load, it must still operate its DC (battery) to AC converter
(the inverter), which costs power. A rough extrapolation from APC's documentation, leads
me to guess that its 2000 VA UPS can operate its own inverter (with no extra load) for just
over 8 hours. A 1250 VA UPS could run its converter for about 5. These are very rough
guesses based on information provided by one vendor for one vendor.
Q: Given the same vendor claims, how can I tell a "good" quality UPS from a "poor"
quality UPS?
A: Testing, testing, testing. I can't emphasize this enough. There are many good and bad units
out there that call themselves UPSes. There are many good units that are wrong for your
situation. Caveat Emptor.
Some properties you might look for include:
Sinusoidal power output. In general, the closer the AC output is to a sine wave, the better it is
for your equipment. Many UPS units, especially the cheaper ones, deviate
a great deal from a sinusoidal output. Some of them generate square waves. Waveform
effects are dealt with in section 2.12 of this document.
Does the UPS have a manual bypass switch? If the UPS is broken or is being serviced, can
you pass power through it to your equipment? The last thing you want is for a broken UPS to
be the cause of extra downtime.
The more information about operation you can get from watching the unit itself, the better.
How much power (or percentage load) the equipment is drawing, how much battery life is
left and indications of the input power quality are all very useful.
Some newer UPSes can communicate with their monitoring software via a network
connection and SNMP. This is wonderful if your network is on a UPS. Also, beware, I have
heard of dealers advertising "Network UPS" monitoring where the network is the normal
serial connection.
Does the vendor offer support/maintenance contracts? If they aren't offered, I would suspect
the quality of the equipment.
If you do have a UPS that does not output a sinusoidal waveform, some manufacturers
strongly urge you to not put a surge protector between the UPS and the computer. The surge
protector might mistake the non-sine waveform as a power surge and try to send it to ground.
This could be bad for your UPS, not to mention your equipment. I don't know if this has
happened or not, but I wouldn't chance it.
Q: Should I make sure I have a support/maintenance contract for my UPS systems?
A: Some people strongly recommend this, some don't. It depends on the situation. There are
things that can go wrong with UPSes, and they require periodic maintenance. As with all
support contracts, you're generally spending a little extra money to reduce risk. Whether this
is worthwhile is up to you.
While the electronics are likely to last for quite a while, the batteries will periodically need to be
replaced. This will happen more frequently the more (and deeper) the batteries are cycled.
Replacing the batteries every three years is a pretty typical vendor recommendation (but read
the product details for authoritative information). Any battery that has been in continuous
service for five years probably should be considered suspect until proven otherwise.
Like any other electronic device, a UPS can fail. You need to have a plan for this. If you don't
want to risk having to replace a failed unit at an inconvenient time, you might want to look
into a support contract.
Q: What sort of maintenance can I perform myself?
A: One good thing you might want to do is periodically test the UPSes and their failure modes.
A good time to do this might be right after a periodic level 0 backup. Nobody is logged in and
you've got full backups of the machines. Throw the circuit breaker with the UPS on it to
simulate and outage and see how the transition goes.
Note that in general testing by pulling the plug from the wall is not a good idea. Electronics
like to always have a good ground reference. If you unplug a UPS, it's still powered but now
has what electricians call a "floating ground". Not only can this be bad for electronics, but it
can be quite dangerous as well. It is likely that unplugging just about any UPS for a short
amount of time isn't likely to result in disaster (don't take my word for it, though!), but in all
cases, throwing a circuit breaker would be a better thing to do.
It might be useful to install a GFI (Ground Fault Interrupter) on your UPS-covered outlets to
facilitate this testing without having to throw a breaker, especially if you don't have your UPS
protected machines on an isolated circuit (which you probably should). These are the sockets
found in most modern kitchens and bathrooms with a red and a black button. You push the
latter to cut power and the former to restore power.
Almost all UPSes use lead-acid batteries, like most car batteries. Unlike, say, NiCad
(Nickel-Cadmium) batteries, lead-acid batteries do not have "battery memory". Each "deep
cycle" (running the batteries to very low or even drained levels) will decrease a lead-acid
battery's effectiveness, so this should be avoided. Of course, handling these situations is the
reason you've bought a UPS, but one should not run a UPS down when doing so isn't
necessary.
As a UPS gets older, its battery life will become shorter. Of course there's no way to reliably
test how long it is without running the battery down and you don't want to do that because
they have lead acid batteries. <sigh> All of these are very good reasons to get a support
contract for them that includes periodic battery Replacement at the very least, you can figure
that under a normal workload the batteries will usually still be reasonably good at the end of
the UPS warranty figure, so that's a good place to start guesswork.
Q: How important is the UPS output waveform?
A: That's a good question, and one is worthy of some debate. One school of thought holds
that one should always run equipment on the best approximation of sinusoidal input that one
can, and that deviations produce harmonics which may
either be interpreted as signal if they get through a power supply, or may actually damage the
equipment. Another school holds that since almost all computers use switching-type power
supplies, which only draw power at or near the peaks of the waveforms, the shape of the
input power waveform is not important. Who's right?
I don't know. My opinion is that sinusoidal output is worth the extra money, especially for
on-line UPS systems that continually provide their waveform to the computer. Also, if you
don't know that your equipment has a switching-type power supply, you might want to think
twice before buying a low quality UPS. [ Some of this information from a great article in the
October 1994 issue of LAN Magazine, check it out. -npc ]
Q: Can I really count on a UPS protecting my equipment?
A: This is a tough question. While most UPS systems that you're likely to buy in a store or
computer catalog are likely to help your uptime more than hurt it, these are not intended for
safety or life-critical equipment.
Basically, these devices should be considered to be pieces of consumer electronics The
number one basis on which most of these devices compete with each other is on price, not
quality. I have had UPSes arrive dead from the factory. I have had them fail (taking equipment
down with them) within weeks of first installation. I can't prove it, but I'm willing to bet that
when an old (beyond warranty) line- interactive UPS from a major manufacturer died on me it
fried a machine motherboard, memory, network card, and monitor. In the < 2000 VA range,
cost-effectiveness is more important to UPS vendors (because it appears to be more important
to their customers) than ultimate reliability. If your life depends on computer uptime, you need
a special purpose, online, big, redundant, expensive system. These systems are beyond the
scope of this document. When you buy a UPS at your local computer store, you are not
buying this sort of system.
This is not to say that these things are bad or a waste of money, it's just that they're not a
panacea. In most locations I have worked with most decent UPSes my equipment statistically
has suffered less downtime and lower hardware failure rates when it's protected by a UPS
than when it's not. But these devices are not infallible. When you add one to the mix,
technically it's one more thing that can and sometimes will go wrong. These devices age and
occasionally break. A bad one occasionally slips through quality control. Consider it two steps
forward and one step back. That's still progress.
There are some things you can do to decrease the likelihood that a UPS will trip you up. Here
are some suggestions. This is not an exhaustive list:
Perform regular maintenance on your UPS. This includes changing the batteries periodically.
Don't ever run on bad batteries. Unless your UPS has a bypass feature which allows you to
change batteries without disconnecting the UPS, this means shutting your important server
down on occasion.
Don't deep cycle the batteries any more than is necessary.
Make sure the UPS keeps in contact with its electrical ground at all times.
Don't subject the UPS to temperature or humidity extremes, water, excessive dust, or
excessive static electricity. Keep the area around the UPS clean and dry.
Don't overload the UPS.
If the UPS shows signs of misbehavior or malfunction, remove it from service at
the earliest possible opportunity. Don't put it back into service until it has been examined and
re certified by qualified support personnel.
Q: I think I'd like to build/refurbish/upgrade my own UPS myself. Is this a good idea?
A: My short answer: No, it's not a good idea. Basically, if you're soliciting information from
this document on whether or how to do this, you're not qualified to do this, so don't.
Just as with any other electronics project, it's possible to build one yourself if you know what
you're doing. In the case of a UPS, though, the tolerances are very tight, and the
consequences of building it wrong can be severe. You're working with energies sufficient to
kill a person or start a major fire, the batteries contain hazardous materials, and the serious
possibility exists that something can be hooked up wrong with disastrous results. If the
wrong types of batteries are installed in a UPS very bad things will happen. Unless you really
know what you're doing, you're much better off sticking with equipment that others have
certified rather than trying to save just a few bucks by doing it yourself. Of course, if you
do really know what you're doing, then you don't need (or want) my advice. Definitely leave
this project for the professionals.
TOPIC: UPS monitoring/shutdown software.
Q: If the power is out for a long time, I would like to have my computer automatically
shut itself down gracefully before the UPS batteries die.
Can I do this?
A: Yes. Most manufacturers support software that will do this for some UPSes on at least
some platforms. Ask your UPS vendor for details.
Q: Okay, how about restarting the system for me once power returns?
A: Not all UPS software products do this, but many do. Again, ask your vendor. I do not
know of any freely distributable products that will do this. It doesn't mean that they can't be
built, but vendor software is cheap enough (usually) that it's probably not worth building.
Q: How does this software work? I'm a starving (fill in the blank) who can't afford
software or I have a UPS protecting a computer running an operating system that
nobody supports.
A: Usually, there is a serial port on the back of a UPS that can be used to connect it to just
about any computer. Sometimes these connections are null-modem, sometimes they're not.
The UPS sends information along the serial line as it goes.
If you can decode which pins contain which information, how the information is formatted
and figure out what it wants to hear from the computer side, you're all set.
Here is a skeleton script that outlines a very simple UPS interface provided by Joe Moss,
joe_AT_morton.rain.com. Definitely check this out as a starting point, but don't expect it to
do anything meaningful without some work.
#! /bin/sh
# Shut down system in case of extended power failure
# This should be the serial port to which the UPS is connected
# This port must be set to block on open until the DCD line
# is asserted - many UNIX systems have this determined by
# the minor device number, if not, see if there is some way
# to enable this behavior on your system
PORT=/dev/ttya
# Ok, this should block until there is a power failure
: > $PORT
# If we reach this point, we've lost power
wall << EOF
The sky is falling!! The sky is falling!!
EOF
# call shutdown (or init or whatever)
exec shutdown
Q: Hmmm... that sounds kinda complicated. Has someone already done this?
A: Any solution would almost certainly be vendor specific. However, some brave souls have
provided partial functionality for certain vendors' UPSes. The upsd and upsmon packages are
Open Source software that supports APC UPSes. They are available at:
ftp://ftp.rge.com/pub/admin/upsd/ and ftp://newcorridor.com/pub/upsmon/.
Note: Different UPSes produce different sorts of signals. Some software that works with one
brand or model of UPSes may or may not work with others.
Q: I can't find monitoring software that will work on my configuration. What should I
do?
A: Well, it seems you have a few choices:
Build your own.
Use something freely distributable.
Lean on your UPS vendor to port to your platform.
Try a different vendor that supports your platform.
Q: What other software is out there?
A: Software packages for UPS machines are getting more sophisticated. Most
provide some level of power and status monitoring, but lately there are more GUI's, more
interactive packages, SNMP support, and even call-out paging. See the
software section 05.03 for more info.
TOPIC: How big a UPS do I need?
Q: How are the "sizes" of UPSes determined?
A: Typically, a UPS has a VA rating. The VA rating is the maximum number of Volts * Amps
it can deliver. The VA rating is not the same as the power drain (in Watts) of the equipment.
(This would be true if the load were only resistive or the circuit were DC, not AC).
Computers are notoriously non-resistive. A typical PF (power factor: Watts/VA) for some
computers may be as low as 0.6, which means that if you record a drain of 100 Watts, you
need a power source with a VA rating of 167. Some literature suggests that 0.7 may be a
good conversion factor, but this will depend heavily on the specific equipment. Moreover,
there's really no way to determine these numbers besides measuring them.
Note: Some UPSes can continue to deliver power if the VA rating is exceeded, they merely
can't provide above their VA rating if the power goes. Some can't provide power above their
VA rating at all. Some may do something really nasty if you try.
In any case, I strongly recommend not doing this under any circumstances.
Generally, the rule of thumb seems to be never drawing more VA from an UPS
than about 75% of its rating.
Q: How can I tell what VA rating I need for my equipment?
A: First, when possible, get VA rather than wattage ratings.There are a couple of
ways to evaluate your electrical load:
Direct measurement. You can get equipment to measure the current draw of your equipment
directly. You may or may not have access to this. If you are part of an organization that has
its own facilities/electrical type people, they're likely to be able to do this. They might help you
out if you ask nice. If you're on a budget and don't want to shell out for a high-quality
ammeter, you might want to dry a device called the "Kill A Watt" electric usage monitor made
by P3 International.
Compare notes. If you know someone with the same setup you're using, ask them what they
use and how close they are to the maximum VA rating. Use a chart. Most vendors can help
you out for common equipment. If you have an unusual setup, or mix equipment a lot, this
may be more difficult.
Use the equipment rating. Most pieces of computer equipment have a power rating on some
back panel near where power cord enters the chassis. This number is usually very
conservative, as it is necessary for the manufacturer to play it safe or they'll get sued. Also,
these numbers generally represent a conservative estimate of total draw of the equipment
when it is in its most power-hungry configuration. Typical device configurations may be less
demanding.
Note: Method 1 is by far the best, method 2 and 3 are secondary, method 4 is usually overkill,
but pretty safe. In a pinch, obtaining a UPS whose VA rating is equal or greater than the sum
of all listed electrical load ratings is pretty safe. Don't forget to include headroom for
expansion!
Q: Hmmm... seems like this can be a tough thing to determine.
A: Yeah, it can be. It's also very important. Remember, if you get a UPS that's too big, then
you've overpaid, but your equipment can survive a longer outage. If you get a UPS that's too
small, your equipment might not be protected. Therefore, I recommend that you be
conservative in buying these things. Unfortunately, this costs money.
Q: What else should I consider?
A: It would be nice to know how long your site's typical power outages are. In some places,
with nice weather and a flaky power grid, the power is almost never out for more than 5
minutes, but this could happen quite frequently. In this case, you may as well use a UPS with
a VA rating close to your equipment rating with no extra batteries. If your area has longer
outages, in the half hour or hour range, as is often the case in thunderstorm country, you can
either buy UPSes with multiples of the VA rating of the equipment, since oversizing a VA
rating for a UPS has the effect of lengthening the amount of time your equipment can stay up
in case of a power outage, or you can buy additional battery units for a smaller UPS. You can
probably get away with doing simple math to determine how much longer a larger UPS will
keep your equipment running, but I recommend running a few tests before committing to a
large purchase order. Also, your UPS vendor will almost certainly be glad to help you size the
equipment you need. If all else fails and you guess wrong, or move equipment to a location
with different power status, you may be really, really glad if you bought a UPS that can be
expanded with additional battery units.
Q: How about I use one of these UPS thingies for a laser printer?
A: Generally, this is not a good idea. If you ever measured the current draw of a Laser printer
during startup (and during printing) you'd likely be stunned at what it pulls. UPS manufacturers
generally recommend that you not do this. Some UPSes are available that are specifically
inteded for use with laser printers, but most don't.
At the very least, don't do this unless you have carefully sized your equipment and your UPS
vendor has committed to supporting this particular configuration.
Q: So, what sorts of UPS sizes do you use on your equipment?
A: BIG DISCLAIMER. I disclaim everything about these figures. At best, they are very, very
rough. Heck, I may be lying. Don't trust them. Here they are anyway.
Most PC ATX power supplies these days seem to be running in the 300 W range.A typical
CRT monitor tends to draw about 1 Amp (~120 W), an LCD monitor of the same size a bit
less. Peripherals like speakers and small networking equipment tend to draw little power.
Figuring on 450 VA for a typical desktop computer setup is pretty conservative. For a single
machine plus small associated networking equipment (for example, a DSL/Cable
modem/router, wireless access point, etc.), buying a 600 VA UPS is often pretty reasonable.
Buying a bigger UPS will allow you to protect more equipment going forward.
Another word of warning, don't assume that power requirements scale with compute power
and number of peripherals, ESPECIALLY if they are different architectures. Sometimes older
equipment is less efficient and draws more power than more recent gear. This is especially
true with things like monitors, disks, etc..
On the other hand, as compute power increases, often power consumption does too. The
current crop of Pentium 4s draws much more power than, say, an old 386 did. This can be
seen in the fact that contemporary PC power supplies are usually more powerful than the
same devices were a few years ago. The big lesson to learn is that there's no replacement for
direct measurement.
TOPIC: Specific manufacturer's information.
Q: What vendors are there and what do they produce?
A: Here is a very incomplete list
UPS Hardware (and software) manufacturers:
American Power Conversion : APC is the largest manufacturer of small UPSes (<2000 VA)
and has a whole line of UPS systems (mostly line interactive), software, and power system
accessories which can be purchased directly from them or via many retail outlets around the
United States and overseas.
Belkin : Belkin makes a lot of computer connectivity products, including UPSes.
Clary Corporation : Clary sells UPS products and specializes in emergency,
military, and life support systems. They also sell management software and
accessories.
Controlled Power Company : Controlled Power produces UPS systems, power
conditioners, voltage regulators and transformers. Equipment can be ordered direct.
Eaton Powerware : Eaton Powerware includes the product line that was formerly
Best Power, Inc.. They produce many types of UPS systems. more advanced line interactive
systems, and ferroresonant line interactive systems as well as software, PDUs, and power
system accessories.
Emerson Electronics : Emerson is a big electronics conglomerate. It's claim to fame in the
UPS world is that it's the parent company to Liebert.
Energy Technologies, Inc. Energy Technologies provides power devices (including UPSes)
for physically demanding customers, including military and vehicle uses. Most if their UPS
systems seem to fall in the 600 to 6000 VA range.
Exide Electronics : One of the bigger players in the data center sized UPS system industry,
Exide also makes more modest sized on-line and line interactive systems. Exide products can
be purchased direct or from their distributors.
Gamatronic Electronic Industries, Ltd. I'm told these guys are the largest UPS
manufacturer in Israel and the Middle East. Their product line runs the gammut rom 1000 VA
to 150 kVA systems.
General Electric Industrial Systems : Yup, GE makes UPSes from 300 VA up to MVA
systems.
IntelliPower, Inc. : Intellipower sells on-line UPS systems and management software.
Liebert : A subsidiary of Emerson Electronics (see above), Liebert is probably the largest
manufacturer of large (10 kVA +) UPS systems. Also well known for their other data center
products including power distribution units and HVAC products.
They also make smaller UPS systems (300 VA on up), but these are not nearly as popular.
MGE UPS Systems MGE UPS Systems sells UPS systems from 300 VA to the very large
and additional power equipment.
Mitsubishi Electric Automation : Mitsubishi Electric Automation seems to specialize in
larger (> 5 kVA) UPSes, but they make them as small as 1 kVA.
Oneac : Oneac sells line interactive and online UPS systems with software in the US and UK.
They were acquired by the Chloride Group (see Chloride Power, below) in 1998.
OPTI-UPS : OPTI-UPS makes standby, line-interactive, and online UPS systems ranging
from 375 VA to 8000 VA.
Philtek : Philtek makes inverters and other similar power system components.
SL Waber : SL Waber sells mostly UPS systems including the Tripp Lite brand name as
well as a wide assortment of surge suppression and other power accessories.
Toshiba : Toshiba sells a lot of things, including UPSes. They sell online UPSes from 1400
VA to the 300 kVA range. One of Toshiba's product lines are UPSes specially designed to
automatically configure themselves to work with both US (60 Hz) and European (50 Hz)
power.
P3 International : P3 International makes a number of cool consumer electronics devices,
but as far as this document is concerned, the most interesting is an easy-to -use and relatively
inexpensive power monitoring device called "Kill A Watt". When you can't or don't want to
use a good break-out cable and ammeter, this device is a good choice for measuring power
consumption.
Power Innovations International, Inc. : Power Innovations sells online UPS systems
ranging from 500 VA to 400 kVA.
Chloride Power : Chloride Power is a relative newcomer to the U.S. market but has much
more experience and is better known in Europe. For the US market Chloride produces online
UPS from the 700 VA to 3000 kVA range, and what look like they might be standby systems
from 300 VA to 650 VA.
There are a lot of companies in this space, and there's no way that I can list all of them. I try
to include most of the best known companies along with a few niche players that might be of
interest to the readers of this document. Let me know if there are important companies that I
haven't included.
TOPIC: Bibliography
There are many good references and review articles on UPS information. Some of the best
sources can be found in vendor information. There is great reference material woven into their
propaganda. Some other good sources are:
"The Dranetz Field Handbook for Power Quality Analysis", 1991, Dranetz Technologies, 1000
New Durham Rd., Edison, NJ 08818, 1-908-287-3680.
"National Electrical Code Handbook",
1993, National Fire Protection Association, One Batterymarch Park, P.O. Box 9101, Quincy,
MA 02269, 1-617-770-3000.
"Grounding and Shielding in Facilities",1990, by Ralph Morrison and Warren H. Lewis, John
Wiley & Sons, New York, ISBN 0-471-83807-1.
"Battling Power Problems", by Alan Frank, LAN Magazine, October 1994, pp 65-72, Miller
Freeman, Inc..
"UPS Chart",
by the LAN staff, LAN Magazine, October 1994, pp 74-84, Miller Freeman, Inc..
Hewlett-Packard has a White Paper on selecting a UPS. You may be able to get them to send
it to you. A shortened version appeared as an article in the January 9, 1995 issue of Electronic
Engineering Times.
One critical source of information on power protection is the IEEE "color book" series,
especially the following:
The Emerald Book, IEEE Recommended Practice for Powering and Grounding Electronic
Equipment, Std. 1100-1999, 1999.
The Gold Book, IEEE Recommended Practice for the Design of Reliable Industrial and
Commercial Power Systems, Std. 493-1997, 1997.
The Green Book, IEEE Recommended Practice for Grounding of Industrial and Commercial
Power Systems, Std. 241-1990, 1990.
Source
This presentation contains major items from the full version number 2.3 dated March 6,2003,
which can be accessed at Jetcafe.org
The excerpts from the original document are presented here without alterations or comments.
Uninterruptible Power Supplies as well as applications of these systems.. This article is
courtesy of Mr.Nick Christenson from Jetcofe.org. Please see details at the end of the article.
Blackout
Complete loss of power. Some literature considers a voltage drop below about 80V to be a
blackout as well since most equipment will not operate below these levels.
Sag or Brownout
Decrease in voltage levels which can last for periods ranging from fractions of a second to
hours. Can be caused by heavy equipment coming on line such as shop tools, elevators,
compressors etc. Also occurs when utility companies deliberately do this to cope with peak
load times.
Spike
A tremendous increase in voltage over a very short period of time often caused by a direct
lightning strike on a power line or when power returns after a blackout.
Surge
A substantial increase in voltage lasting a small fraction of a second, often caused when high
powered appliances such as air conditioners are switched off.
EMI/RFI Noise
Electromagnetic Interference and Radio Frequency Interference. Caused by, inter alia,
lightning, generators, radio transmitters, industrial equipment.
MOV
Metal Oxide Varistors are added to circuits in order to control spikes. These are common in
Power Strips. If you see more than two, you likely have a fairly decent Power Strip. They
look like largish disk capacitors.
Inverter
Circuitry that converts DC battery power to AC power required by most computer equipment.
Surge Protector
Circuitry consisting of MOVs, capacitors, rod-core inductors etc. For suppressing surges
and spikes usually embedded in a power strip.
Line Conditioner
A transformer that attempts to smooth out fluctuations in input voltage to provide near
uniform output voltage or voltage waveform.
Topic: What is a UPS, how does is work, how does it help?
Q: What is a UPS?
A: An Uninterruptible Power Supply is a device that sits between a power supply (e.g. A wall
outlet) and a device (e.g. A computer) to prevent undesired features of the power source
(outages, sags, surges, bad harmonics, etc.) from the supply from adversely affecting the
performance of the device.
Q: Can you give me some more information on the UPS industry?
A: The industry is made up of many manufacturers, and there is a lack of standard terms
within the industry. I think this sometimes borders on deliberate misdirection. (It's a jungle
out there!) [ Note, in recent years the whole industry seems to have gotten better, at least
mostly agreeing on what the terms listed here mean. This is not true everywhere, but things
are getting better. ]
There are basically three different types of devices.
Standby power supply (SPS). In this type of supply, power is usually derived directly from
the power line, until power fails. After power failure, a battery powered inverter turns on to
continue supplying power. Batteries are charged, as necessary, when line power is available.
This type of supply is sometimes called an "offline" UPS.
The quality and effectiveness of this class of devices varies considerably; however, they are
generally quite a bit cheaper than "true" UPSes. The time required for the inverter to come on
line, typically called the switchover time, varies by unit. While some computers may be able
to tolerate long switchover times, your mileage may vary. [ Some articles in the trade press
have claimed that their testing shows that modern PCs can withstand transfer times of
100ms or more. Most UPS units claim a transfer time to battery of about 4ms. Note that even
if a computer can stay up for 100ms, it doesn't mean that 100ms switchover is okay. Damage
can still be done to a computer or data on it even if it stays up. ]
Other features to look for in this class of supplies is line filtering and/or other line conditioners.
Since appliances connected to the supply are basically connected directly from the power line,
SPSes provide relatively poor protection from line noise, frequency variations, line spikes, and
brownouts.
Some SPSes claim to have surge/spike suppression circuitry as well as transformers to
"boost" voltage without switching to the battery if a modest voltage drop occurs. Often, as a
"standby" UPS becomes more feature full it is called a "line interactive" UPS.
Hybrid [or ferroresonant ] systems. I only know one vendor who sells them - Best Power Inc.
[ Now called Eaton Powerware. Note that Powerware also sells line interactive and online
UPSes. ] The theory behind these devices is fairly simple. When normal operating line power
is present, the supply conditions power using a ferroresonant transformer. This transformer
maintains a constant output voltage
even with a varying input voltage and provides good protection against line noise.
The transformer also maintains output on its secondary briefly when a total outage occurs.
Best claims that their inverter then goes on line so quickly that it is operating without any
interruption in power. Other vendors maintain that the transition is less than seamless, but
then again it's not in their best interest to promote Best's products.
[ Note: According to some sources, ferroresonant transformers in an UPS system can interact
with ferroresonant transformers in your equipment's power supply and produce unexpected
results. On the other hand, ferroresonant systems don't kick off a lot of heat, which is
important in some environments. The Moral: Test equipment to make sure it meets your needs
before you buy. -npc ]
What I call "true" UPS systems, those supplies that continuously operate from an inverter.
Obviously, there is no switchover time, and these supplies generally
provide the best isolation from power line problems. The disadvantages to these devices are
increased cost, increased power consumption, and increased heat generation. Despite the fact
that the inverter in a "true" UPS is always on, the reliability of such units does not seem to be
affected. In fact, we have seen more failures in cheaper SPS units. [ Note, though, that given
the same quality inverter,
you'd expect the one that runs least to last longest. These devices are often called "online"
UPSes. ]
Q: How can it help me?
A: UPS has internal batteries to guarantee that continuous power is provided to the equipment
even if the power source stops providing power. Of course the UPS can only provide power
for a while, typically a few minutes, but that is often enough to ride out power company
glitches or short outages. Even if the outage is longer than the battery lifetime of the UPS, this
provides the opportunity to execute an orderly shutdown of the equipment.
Advantages:
Computer jobs don't stop because the power fails.
Users not inconvenienced by computer shutting down.
Equipment does not incur the stress of another (hard) power cycle.
Data isn't lost because a machine shut down without doing a "sync" or equivalent to flush
cached or real time data.
Q: What sort of stuff does a UPS do?
A: UPS traditionally can perform the following functions:
Absorb relatively small power surges.
Smooth out noisy power sources.
Continue to provide power to equipment during line sags.
Provide power for some time after a blackout has occurred.
In addition, some UPS or UPS/software combinations provide the following functions:
Automatic shutdown of equipment during long power outages.
Monitoring and logging of the status of the power supply.
Display the Voltage/Current draw of the equipment.
Restart equipment after a long power outage.
Display the voltage currently on the line.
Provide alarms on certain error conditions.
Provide short circuit protection.
Q: How long can equipment on a UPS keep running after the power goes?
A: That depends on how big a UPS do you have and what kind of equipment it protects. For
most typical computer workstations, one might have a unit that was rated to keep the
machine alive through a 15 minute power loss. If it is important for a machine to survive
hours without power, one should probably look at a more robust power backup solution that
includes a generator and other components.
Even if a UPS powers a very small load, it must still operate its DC (battery) to AC converter
(the inverter), which costs power. A rough extrapolation from APC's documentation, leads
me to guess that its 2000 VA UPS can operate its own inverter (with no extra load) for just
over 8 hours. A 1250 VA UPS could run its converter for about 5. These are very rough
guesses based on information provided by one vendor for one vendor.
Q: Given the same vendor claims, how can I tell a "good" quality UPS from a "poor"
quality UPS?
A: Testing, testing, testing. I can't emphasize this enough. There are many good and bad units
out there that call themselves UPSes. There are many good units that are wrong for your
situation. Caveat Emptor.
Some properties you might look for include:
Sinusoidal power output. In general, the closer the AC output is to a sine wave, the better it is
for your equipment. Many UPS units, especially the cheaper ones, deviate
a great deal from a sinusoidal output. Some of them generate square waves. Waveform
effects are dealt with in section 2.12 of this document.
Does the UPS have a manual bypass switch? If the UPS is broken or is being serviced, can
you pass power through it to your equipment? The last thing you want is for a broken UPS to
be the cause of extra downtime.
The more information about operation you can get from watching the unit itself, the better.
How much power (or percentage load) the equipment is drawing, how much battery life is
left and indications of the input power quality are all very useful.
Some newer UPSes can communicate with their monitoring software via a network
connection and SNMP. This is wonderful if your network is on a UPS. Also, beware, I have
heard of dealers advertising "Network UPS" monitoring where the network is the normal
serial connection.
Does the vendor offer support/maintenance contracts? If they aren't offered, I would suspect
the quality of the equipment.
If you do have a UPS that does not output a sinusoidal waveform, some manufacturers
strongly urge you to not put a surge protector between the UPS and the computer. The surge
protector might mistake the non-sine waveform as a power surge and try to send it to ground.
This could be bad for your UPS, not to mention your equipment. I don't know if this has
happened or not, but I wouldn't chance it.
Q: Should I make sure I have a support/maintenance contract for my UPS systems?
A: Some people strongly recommend this, some don't. It depends on the situation. There are
things that can go wrong with UPSes, and they require periodic maintenance. As with all
support contracts, you're generally spending a little extra money to reduce risk. Whether this
is worthwhile is up to you.
While the electronics are likely to last for quite a while, the batteries will periodically need to be
replaced. This will happen more frequently the more (and deeper) the batteries are cycled.
Replacing the batteries every three years is a pretty typical vendor recommendation (but read
the product details for authoritative information). Any battery that has been in continuous
service for five years probably should be considered suspect until proven otherwise.
Like any other electronic device, a UPS can fail. You need to have a plan for this. If you don't
want to risk having to replace a failed unit at an inconvenient time, you might want to look
into a support contract.
Q: What sort of maintenance can I perform myself?
A: One good thing you might want to do is periodically test the UPSes and their failure modes.
A good time to do this might be right after a periodic level 0 backup. Nobody is logged in and
you've got full backups of the machines. Throw the circuit breaker with the UPS on it to
simulate and outage and see how the transition goes.
Note that in general testing by pulling the plug from the wall is not a good idea. Electronics
like to always have a good ground reference. If you unplug a UPS, it's still powered but now
has what electricians call a "floating ground". Not only can this be bad for electronics, but it
can be quite dangerous as well. It is likely that unplugging just about any UPS for a short
amount of time isn't likely to result in disaster (don't take my word for it, though!), but in all
cases, throwing a circuit breaker would be a better thing to do.
It might be useful to install a GFI (Ground Fault Interrupter) on your UPS-covered outlets to
facilitate this testing without having to throw a breaker, especially if you don't have your UPS
protected machines on an isolated circuit (which you probably should). These are the sockets
found in most modern kitchens and bathrooms with a red and a black button. You push the
latter to cut power and the former to restore power.
Almost all UPSes use lead-acid batteries, like most car batteries. Unlike, say, NiCad
(Nickel-Cadmium) batteries, lead-acid batteries do not have "battery memory". Each "deep
cycle" (running the batteries to very low or even drained levels) will decrease a lead-acid
battery's effectiveness, so this should be avoided. Of course, handling these situations is the
reason you've bought a UPS, but one should not run a UPS down when doing so isn't
necessary.
As a UPS gets older, its battery life will become shorter. Of course there's no way to reliably
test how long it is without running the battery down and you don't want to do that because
they have lead acid batteries. <sigh> All of these are very good reasons to get a support
contract for them that includes periodic battery Replacement at the very least, you can figure
that under a normal workload the batteries will usually still be reasonably good at the end of
the UPS warranty figure, so that's a good place to start guesswork.
Q: How important is the UPS output waveform?
A: That's a good question, and one is worthy of some debate. One school of thought holds
that one should always run equipment on the best approximation of sinusoidal input that one
can, and that deviations produce harmonics which may
either be interpreted as signal if they get through a power supply, or may actually damage the
equipment. Another school holds that since almost all computers use switching-type power
supplies, which only draw power at or near the peaks of the waveforms, the shape of the
input power waveform is not important. Who's right?
I don't know. My opinion is that sinusoidal output is worth the extra money, especially for
on-line UPS systems that continually provide their waveform to the computer. Also, if you
don't know that your equipment has a switching-type power supply, you might want to think
twice before buying a low quality UPS. [ Some of this information from a great article in the
October 1994 issue of LAN Magazine, check it out. -npc ]
Q: Can I really count on a UPS protecting my equipment?
A: This is a tough question. While most UPS systems that you're likely to buy in a store or
computer catalog are likely to help your uptime more than hurt it, these are not intended for
safety or life-critical equipment.
Basically, these devices should be considered to be pieces of consumer electronics The
number one basis on which most of these devices compete with each other is on price, not
quality. I have had UPSes arrive dead from the factory. I have had them fail (taking equipment
down with them) within weeks of first installation. I can't prove it, but I'm willing to bet that
when an old (beyond warranty) line- interactive UPS from a major manufacturer died on me it
fried a machine motherboard, memory, network card, and monitor. In the < 2000 VA range,
cost-effectiveness is more important to UPS vendors (because it appears to be more important
to their customers) than ultimate reliability. If your life depends on computer uptime, you need
a special purpose, online, big, redundant, expensive system. These systems are beyond the
scope of this document. When you buy a UPS at your local computer store, you are not
buying this sort of system.
This is not to say that these things are bad or a waste of money, it's just that they're not a
panacea. In most locations I have worked with most decent UPSes my equipment statistically
has suffered less downtime and lower hardware failure rates when it's protected by a UPS
than when it's not. But these devices are not infallible. When you add one to the mix,
technically it's one more thing that can and sometimes will go wrong. These devices age and
occasionally break. A bad one occasionally slips through quality control. Consider it two steps
forward and one step back. That's still progress.
There are some things you can do to decrease the likelihood that a UPS will trip you up. Here
are some suggestions. This is not an exhaustive list:
Perform regular maintenance on your UPS. This includes changing the batteries periodically.
Don't ever run on bad batteries. Unless your UPS has a bypass feature which allows you to
change batteries without disconnecting the UPS, this means shutting your important server
down on occasion.
Don't deep cycle the batteries any more than is necessary.
Make sure the UPS keeps in contact with its electrical ground at all times.
Don't subject the UPS to temperature or humidity extremes, water, excessive dust, or
excessive static electricity. Keep the area around the UPS clean and dry.
Don't overload the UPS.
If the UPS shows signs of misbehavior or malfunction, remove it from service at
the earliest possible opportunity. Don't put it back into service until it has been examined and
re certified by qualified support personnel.
Q: I think I'd like to build/refurbish/upgrade my own UPS myself. Is this a good idea?
A: My short answer: No, it's not a good idea. Basically, if you're soliciting information from
this document on whether or how to do this, you're not qualified to do this, so don't.
Just as with any other electronics project, it's possible to build one yourself if you know what
you're doing. In the case of a UPS, though, the tolerances are very tight, and the
consequences of building it wrong can be severe. You're working with energies sufficient to
kill a person or start a major fire, the batteries contain hazardous materials, and the serious
possibility exists that something can be hooked up wrong with disastrous results. If the
wrong types of batteries are installed in a UPS very bad things will happen. Unless you really
know what you're doing, you're much better off sticking with equipment that others have
certified rather than trying to save just a few bucks by doing it yourself. Of course, if you
do really know what you're doing, then you don't need (or want) my advice. Definitely leave
this project for the professionals.
TOPIC: UPS monitoring/shutdown software.
Q: If the power is out for a long time, I would like to have my computer automatically
shut itself down gracefully before the UPS batteries die.
Can I do this?
A: Yes. Most manufacturers support software that will do this for some UPSes on at least
some platforms. Ask your UPS vendor for details.
Q: Okay, how about restarting the system for me once power returns?
A: Not all UPS software products do this, but many do. Again, ask your vendor. I do not
know of any freely distributable products that will do this. It doesn't mean that they can't be
built, but vendor software is cheap enough (usually) that it's probably not worth building.
Q: How does this software work? I'm a starving (fill in the blank) who can't afford
software or I have a UPS protecting a computer running an operating system that
nobody supports.
A: Usually, there is a serial port on the back of a UPS that can be used to connect it to just
about any computer. Sometimes these connections are null-modem, sometimes they're not.
The UPS sends information along the serial line as it goes.
If you can decode which pins contain which information, how the information is formatted
and figure out what it wants to hear from the computer side, you're all set.
Here is a skeleton script that outlines a very simple UPS interface provided by Joe Moss,
joe_AT_morton.rain.com. Definitely check this out as a starting point, but don't expect it to
do anything meaningful without some work.
#! /bin/sh
# Shut down system in case of extended power failure
# This should be the serial port to which the UPS is connected
# This port must be set to block on open until the DCD line
# is asserted - many UNIX systems have this determined by
# the minor device number, if not, see if there is some way
# to enable this behavior on your system
PORT=/dev/ttya
# Ok, this should block until there is a power failure
: > $PORT
# If we reach this point, we've lost power
wall << EOF
The sky is falling!! The sky is falling!!
EOF
# call shutdown (or init or whatever)
exec shutdown
Q: Hmmm... that sounds kinda complicated. Has someone already done this?
A: Any solution would almost certainly be vendor specific. However, some brave souls have
provided partial functionality for certain vendors' UPSes. The upsd and upsmon packages are
Open Source software that supports APC UPSes. They are available at:
ftp://ftp.rge.com/pub/admin/upsd/ and ftp://newcorridor.com/pub/upsmon/.
Note: Different UPSes produce different sorts of signals. Some software that works with one
brand or model of UPSes may or may not work with others.
Q: I can't find monitoring software that will work on my configuration. What should I
do?
A: Well, it seems you have a few choices:
Build your own.
Use something freely distributable.
Lean on your UPS vendor to port to your platform.
Try a different vendor that supports your platform.
Q: What other software is out there?
A: Software packages for UPS machines are getting more sophisticated. Most
provide some level of power and status monitoring, but lately there are more GUI's, more
interactive packages, SNMP support, and even call-out paging. See the
software section 05.03 for more info.
TOPIC: How big a UPS do I need?
Q: How are the "sizes" of UPSes determined?
A: Typically, a UPS has a VA rating. The VA rating is the maximum number of Volts * Amps
it can deliver. The VA rating is not the same as the power drain (in Watts) of the equipment.
(This would be true if the load were only resistive or the circuit were DC, not AC).
Computers are notoriously non-resistive. A typical PF (power factor: Watts/VA) for some
computers may be as low as 0.6, which means that if you record a drain of 100 Watts, you
need a power source with a VA rating of 167. Some literature suggests that 0.7 may be a
good conversion factor, but this will depend heavily on the specific equipment. Moreover,
there's really no way to determine these numbers besides measuring them.
Note: Some UPSes can continue to deliver power if the VA rating is exceeded, they merely
can't provide above their VA rating if the power goes. Some can't provide power above their
VA rating at all. Some may do something really nasty if you try.
In any case, I strongly recommend not doing this under any circumstances.
Generally, the rule of thumb seems to be never drawing more VA from an UPS
than about 75% of its rating.
Q: How can I tell what VA rating I need for my equipment?
A: First, when possible, get VA rather than wattage ratings.There are a couple of
ways to evaluate your electrical load:
Direct measurement. You can get equipment to measure the current draw of your equipment
directly. You may or may not have access to this. If you are part of an organization that has
its own facilities/electrical type people, they're likely to be able to do this. They might help you
out if you ask nice. If you're on a budget and don't want to shell out for a high-quality
ammeter, you might want to dry a device called the "Kill A Watt" electric usage monitor made
by P3 International.
Compare notes. If you know someone with the same setup you're using, ask them what they
use and how close they are to the maximum VA rating. Use a chart. Most vendors can help
you out for common equipment. If you have an unusual setup, or mix equipment a lot, this
may be more difficult.
Use the equipment rating. Most pieces of computer equipment have a power rating on some
back panel near where power cord enters the chassis. This number is usually very
conservative, as it is necessary for the manufacturer to play it safe or they'll get sued. Also,
these numbers generally represent a conservative estimate of total draw of the equipment
when it is in its most power-hungry configuration. Typical device configurations may be less
demanding.
Note: Method 1 is by far the best, method 2 and 3 are secondary, method 4 is usually overkill,
but pretty safe. In a pinch, obtaining a UPS whose VA rating is equal or greater than the sum
of all listed electrical load ratings is pretty safe. Don't forget to include headroom for
expansion!
Q: Hmmm... seems like this can be a tough thing to determine.
A: Yeah, it can be. It's also very important. Remember, if you get a UPS that's too big, then
you've overpaid, but your equipment can survive a longer outage. If you get a UPS that's too
small, your equipment might not be protected. Therefore, I recommend that you be
conservative in buying these things. Unfortunately, this costs money.
Q: What else should I consider?
A: It would be nice to know how long your site's typical power outages are. In some places,
with nice weather and a flaky power grid, the power is almost never out for more than 5
minutes, but this could happen quite frequently. In this case, you may as well use a UPS with
a VA rating close to your equipment rating with no extra batteries. If your area has longer
outages, in the half hour or hour range, as is often the case in thunderstorm country, you can
either buy UPSes with multiples of the VA rating of the equipment, since oversizing a VA
rating for a UPS has the effect of lengthening the amount of time your equipment can stay up
in case of a power outage, or you can buy additional battery units for a smaller UPS. You can
probably get away with doing simple math to determine how much longer a larger UPS will
keep your equipment running, but I recommend running a few tests before committing to a
large purchase order. Also, your UPS vendor will almost certainly be glad to help you size the
equipment you need. If all else fails and you guess wrong, or move equipment to a location
with different power status, you may be really, really glad if you bought a UPS that can be
expanded with additional battery units.
Q: How about I use one of these UPS thingies for a laser printer?
A: Generally, this is not a good idea. If you ever measured the current draw of a Laser printer
during startup (and during printing) you'd likely be stunned at what it pulls. UPS manufacturers
generally recommend that you not do this. Some UPSes are available that are specifically
inteded for use with laser printers, but most don't.
At the very least, don't do this unless you have carefully sized your equipment and your UPS
vendor has committed to supporting this particular configuration.
Q: So, what sorts of UPS sizes do you use on your equipment?
A: BIG DISCLAIMER. I disclaim everything about these figures. At best, they are very, very
rough. Heck, I may be lying. Don't trust them. Here they are anyway.
Most PC ATX power supplies these days seem to be running in the 300 W range.A typical
CRT monitor tends to draw about 1 Amp (~120 W), an LCD monitor of the same size a bit
less. Peripherals like speakers and small networking equipment tend to draw little power.
Figuring on 450 VA for a typical desktop computer setup is pretty conservative. For a single
machine plus small associated networking equipment (for example, a DSL/Cable
modem/router, wireless access point, etc.), buying a 600 VA UPS is often pretty reasonable.
Buying a bigger UPS will allow you to protect more equipment going forward.
Another word of warning, don't assume that power requirements scale with compute power
and number of peripherals, ESPECIALLY if they are different architectures. Sometimes older
equipment is less efficient and draws more power than more recent gear. This is especially
true with things like monitors, disks, etc..
On the other hand, as compute power increases, often power consumption does too. The
current crop of Pentium 4s draws much more power than, say, an old 386 did. This can be
seen in the fact that contemporary PC power supplies are usually more powerful than the
same devices were a few years ago. The big lesson to learn is that there's no replacement for
direct measurement.
TOPIC: Specific manufacturer's information.
Q: What vendors are there and what do they produce?
A: Here is a very incomplete list
UPS Hardware (and software) manufacturers:
American Power Conversion : APC is the largest manufacturer of small UPSes (<2000 VA)
and has a whole line of UPS systems (mostly line interactive), software, and power system
accessories which can be purchased directly from them or via many retail outlets around the
United States and overseas.
Belkin : Belkin makes a lot of computer connectivity products, including UPSes.
Clary Corporation : Clary sells UPS products and specializes in emergency,
military, and life support systems. They also sell management software and
accessories.
Controlled Power Company : Controlled Power produces UPS systems, power
conditioners, voltage regulators and transformers. Equipment can be ordered direct.
Eaton Powerware : Eaton Powerware includes the product line that was formerly
Best Power, Inc.. They produce many types of UPS systems. more advanced line interactive
systems, and ferroresonant line interactive systems as well as software, PDUs, and power
system accessories.
Emerson Electronics : Emerson is a big electronics conglomerate. It's claim to fame in the
UPS world is that it's the parent company to Liebert.
Energy Technologies, Inc. Energy Technologies provides power devices (including UPSes)
for physically demanding customers, including military and vehicle uses. Most if their UPS
systems seem to fall in the 600 to 6000 VA range.
Exide Electronics : One of the bigger players in the data center sized UPS system industry,
Exide also makes more modest sized on-line and line interactive systems. Exide products can
be purchased direct or from their distributors.
Gamatronic Electronic Industries, Ltd. I'm told these guys are the largest UPS
manufacturer in Israel and the Middle East. Their product line runs the gammut rom 1000 VA
to 150 kVA systems.
General Electric Industrial Systems : Yup, GE makes UPSes from 300 VA up to MVA
systems.
IntelliPower, Inc. : Intellipower sells on-line UPS systems and management software.
Liebert : A subsidiary of Emerson Electronics (see above), Liebert is probably the largest
manufacturer of large (10 kVA +) UPS systems. Also well known for their other data center
products including power distribution units and HVAC products.
They also make smaller UPS systems (300 VA on up), but these are not nearly as popular.
MGE UPS Systems MGE UPS Systems sells UPS systems from 300 VA to the very large
and additional power equipment.
Mitsubishi Electric Automation : Mitsubishi Electric Automation seems to specialize in
larger (> 5 kVA) UPSes, but they make them as small as 1 kVA.
Oneac : Oneac sells line interactive and online UPS systems with software in the US and UK.
They were acquired by the Chloride Group (see Chloride Power, below) in 1998.
OPTI-UPS : OPTI-UPS makes standby, line-interactive, and online UPS systems ranging
from 375 VA to 8000 VA.
Philtek : Philtek makes inverters and other similar power system components.
SL Waber : SL Waber sells mostly UPS systems including the Tripp Lite brand name as
well as a wide assortment of surge suppression and other power accessories.
Toshiba : Toshiba sells a lot of things, including UPSes. They sell online UPSes from 1400
VA to the 300 kVA range. One of Toshiba's product lines are UPSes specially designed to
automatically configure themselves to work with both US (60 Hz) and European (50 Hz)
power.
P3 International : P3 International makes a number of cool consumer electronics devices,
but as far as this document is concerned, the most interesting is an easy-to -use and relatively
inexpensive power monitoring device called "Kill A Watt". When you can't or don't want to
use a good break-out cable and ammeter, this device is a good choice for measuring power
consumption.
Power Innovations International, Inc. : Power Innovations sells online UPS systems
ranging from 500 VA to 400 kVA.
Chloride Power : Chloride Power is a relative newcomer to the U.S. market but has much
more experience and is better known in Europe. For the US market Chloride produces online
UPS from the 700 VA to 3000 kVA range, and what look like they might be standby systems
from 300 VA to 650 VA.
There are a lot of companies in this space, and there's no way that I can list all of them. I try
to include most of the best known companies along with a few niche players that might be of
interest to the readers of this document. Let me know if there are important companies that I
haven't included.
TOPIC: Bibliography
There are many good references and review articles on UPS information. Some of the best
sources can be found in vendor information. There is great reference material woven into their
propaganda. Some other good sources are:
"The Dranetz Field Handbook for Power Quality Analysis", 1991, Dranetz Technologies, 1000
New Durham Rd., Edison, NJ 08818, 1-908-287-3680.
"National Electrical Code Handbook",
1993, National Fire Protection Association, One Batterymarch Park, P.O. Box 9101, Quincy,
MA 02269, 1-617-770-3000.
"Grounding and Shielding in Facilities",1990, by Ralph Morrison and Warren H. Lewis, John
Wiley & Sons, New York, ISBN 0-471-83807-1.
"Battling Power Problems", by Alan Frank, LAN Magazine, October 1994, pp 65-72, Miller
Freeman, Inc..
"UPS Chart",
by the LAN staff, LAN Magazine, October 1994, pp 74-84, Miller Freeman, Inc..
Hewlett-Packard has a White Paper on selecting a UPS. You may be able to get them to send
it to you. A shortened version appeared as an article in the January 9, 1995 issue of Electronic
Engineering Times.
One critical source of information on power protection is the IEEE "color book" series,
especially the following:
The Emerald Book, IEEE Recommended Practice for Powering and Grounding Electronic
Equipment, Std. 1100-1999, 1999.
The Gold Book, IEEE Recommended Practice for the Design of Reliable Industrial and
Commercial Power Systems, Std. 493-1997, 1997.
The Green Book, IEEE Recommended Practice for Grounding of Industrial and Commercial
Power Systems, Std. 241-1990, 1990.
Source
This presentation contains major items from the full version number 2.3 dated March 6,2003,
which can be accessed at Jetcafe.org
The excerpts from the original document are presented here without alterations or comments.
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