| UPS FAQ 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 UPS 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, all of which are occasionally
passed off as UPSes.
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 ] UPS 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 UPS 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 UPS 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 UPS 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 of the UPS 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 a UPSes 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 UPS 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 in a UPS 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 UPS 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 an UPS 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 e
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 UPS 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 UPS 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, all of which are occasionally
passed off as UPSes.
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 ] UPS 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 UPS 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 UPS 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 UPS 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 of the UPS 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 a UPSes 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 UPS 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 in a UPS 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 UPS 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 an UPS 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 e
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 UPS 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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