- 22 June, 2005 16:59
We spend thousands of dollars, sometimes tens of thousands, on our electronic equipment -- everything from our computer and connected devices such as scanner, printer, camera, through to home theatre sound systems, video/DVD recorders, widescreen TVs, security system and more -- but we put it all at risk. Every day. Sure, we go to great measures to protect our valuable electronic gear from theft, but we can still lose it all -- without it every leaving our home or office. How? Electrical surges, spikes, blackouts and even brownouts can ruin the lot. Power problems can damage or destroy it bit by bit or all at once. And the sad fact is that most of us don't spare much thought for how to protect our gear -- until, of course, it is too late. The solution is simple -- and relatively inexpensive -- install an Uninterruptible Power Supply, or UPS.
The big risk
The Big Risk
Why a UPS? Because no matter what make, model or size your equipment is, or what features it has, there is one thing it can't do without -- a clean, continuous supply of electricity. Even if your area doesn't have a history of blackouts or surges, there is an ever-present -- and ever-increasing -- risk that one day, one could strike. And it only needs to happen once to cause costly damage. It could happen to you at any second. All it takes is a "blip" in the power supply to your equipment and it can turn off -- instantly. No excuses. No warnings. It could destroy important data files; corrupt your operating system; damage hardware. Even a very brief interruption to your power can be disastrous. To add to the risk there are also the other problems of "dirty" power -- spikes and brownouts -- which can insidiously wear down your system over a period of time, without you knowing -- until, eventually, it fails. So, let's look at how all this can be avoided by installing an appropriate UPS.
So, what is a UPS and why do I need one?
So, what is a UPS and why do I need one?
To understand why you need a UPS we need to tell you a little bit about electrical power. We all know what a blackout is -- a sudden loss of mains (AC) power. But equally dangerous are some things you may be less familiar with, such as spikes, surges, brownouts and blackouts. These terms all have to do with either too much power or too little. Either condition is bad for your systems, and can be prevented by a properly sized UPS. A UPS, in its simplest form, is a battery backup that takes over supplying electricity to your systems in the event of a power loss. Usually, a UPS is a separate box that sits in the power chain between the source of power (eg, a standard power point) and the rest of your systems. The UPS protects every other piece of equipment that is plugged into it. It is designed to prevent spikes, surges, sags and blackouts from reaching your valuable equipment (See "Power Problems" below). Being first in line, the UPS receives electrical current directly from the power outlet. When mains power is present, the UPS provides filtering (frequency regulation) of small fluctuations to ensure that a continuous supply of "clean" power is fed through to your equipment. When AC power fails, the unit uses its internal battery to supply back-up power without interruption. A typical UPS will power your system for 15-30 minutes, depending on its size (capacity) and the amount of equipment connected to it. Many, if not most, blackouts last for under one hour and while a good UPS will give you enough power to gracefully shut of your equipment during the first few minutes of the blackout, a more powerful unit can give you a "run time" long enough to ride through the entire outage. This will cost you more, of course, and you will have to plan your battery capacity appropriately. Some larger units can take extra battery packs to increase their run time.
Without UPS protection, a sudden loss of power turns off everything, instantly -- often with disastrous results. Computers, in particular, don't like to just "have their plug pulled" with no warning. When you tell your computer to shutdown, it executes a series of commands that puts everything away in its rightful place, ready for the computer to be booted up again. It saves any open files or reminds you to do so, then deletes any temporary files that have been in use and are no longer needed. This usually takes only a matter of seconds, but it is vital to the health of your PC. Failing to shutdown properly like this can corrupt data files instantly. But that is only half the story. Giving your electronic equipment too much power can actually "fry" its insides. This power surge gives your systems a burst of more current than they can cope with, and they can burn out -- this can include your not only your internal power supply unit (PSU) but also your computer's memory (RAM), processor, motherboard and even hard drive.
Types of UPS
Types of UPS
Most types of UPS devices fit into the following three categories: Offline (Standby) UPS; Online UPS; and Line Interactive UPS. Offline (Standby) UPS With this type of UPS, the AC line is the primary power source. Any drop in voltage or current is detected by the UPS, which switches over to the backup battery automatically. When AC power is restored, the UPS switches back. The switchover (transfer) time should be no more than about four milliseconds -- which is the tolerance limit of a typical computer power unit. Any longer and the unit will shut down. If you are technically inclined, you can do a simple calculation to be sure this will work. Compare the unit's transfer time to the hold (or holdup) time of your computer's PSU (which indicates how long the PSU can tolerate having its input cut off before stopping. If the transfer time is less than the hold time, you can feel confident the PC won't shut down unexpectedly. A Ferroresonant UPS is an improvement on this basic offline/standby design. It stores energy in the core of the ferroresonant transformer itself, providing an "electricity buffer" to help tide the PSU over during the transfer to battery power. Line-Interactive UPS In this type of system, the separate battery charger, inverter and source selection switch of an offline UPS have been replaced by a combination inverter/converter. This inverter/converter both charges the battery and converts its DC current to AC for the output to protected devices. AC line power is still the primary power source, and the battery is secondary. When the line power is operating, the inverter/converter charges the battery; when the power fails, it operates in reverse. The main advantage of this design is that the inverter/converter unit is always connected to the output, powering the equipment. This gives a faster response to a power failure than an offline/standby UPS. Usually, the inverter/converter also filters out line noise and spikes, and regulates the power output to supply extra power in sags/brownouts and avoiding surges/spikes. The line-interactive UPS gives better protection than the standby UPS, but it still has a transfer time, so is not as good as the online/continuous UPS. Online UPS
Sometimes called a True UPS, the Online UPS is the best type you can buy. Also known as double conversion, or continuous, this is a top-end UPS which operates with the battery backup unit as the primary power source, rather than the secondary source (as with the Offline and Line-Interactive UPS). The big advantage is that power comes via the battery, which is constantly being charged. The double-conversion method converts AC power from the mains to DC for the battery and then through an inverter to transform the DC back to AC for the external devices. So, there's no transfer time (hence, no interruptions in the flow of electricity) in the event of power failure.
Being more complex, it generally costs more than an offline UPS. It is also less efficient and tends to have higher running costs and higher operating temperature. It is generally used only in larger and mission-critical installations. A Delta-conversion online UPS is an improvement on the standard online UPS, which has lower running costs. In this design, the battery charger is replaced with a "delta converter". Instead of the battery providing all the output (which is relatively inefficient), some of it is also provided directly by the delta converter from the AC input. In an outage, the delta converter stops and the UPS works like a normal online/double-conversion unit.
The smarter UPS
The Smarter UPS
Computer technology is advancing at a great rate, but our supply of power is essentially unchanged. Power problems are a major cause of PC and server downtime. Good UPS-linked power management software is vital to prevent data corruption. When used with computer systems, a UPS will usually connect to your PC (via serial or USB cable) and, in the event of a power problem, tell your computer to start its shutdown procedure. It then continues to provide clean, constant battery power to the PC and other connected equipment so this procedure can be completed. The power management software is usually provided with the UPS, and often comes in more than one version, to provide compatibility with multiple operating systems (OS) such as various flavours of Windows and Linux or Macintosh machines. Be sure that whatever UPS you choose has an appropriate communication port (eg, serial or UPS) and comes with management software that is compatible with your type and version of OS.
Data line protection
Data line protection
Even those who appreciate the risk of power surges often overlook electrical surges (also known as transients) on data lines, which can destroy computing and electronic equipment at work and at home. A good basic UPS will usually have several battery-backup protected power outlets and a couple of surge suppression-only power outlets, plus at least one data-line surge suppression outlet.
What about large installations?
What about large installations?
A UPS is designed to provide battery backup for relatively short periods to allow proper shutdown of protected equipment. But as installations grow larger, the capabilities of batteries are more limited. In any case, they are only a short-term strategy. To support large numbers of equipment for longer periods, a power generator is required. Thus, most large IT installations will also have generators to ride through longer power outages. In a mission critical environment, where no downtime is acceptable, heavy duty UPS systems are backed by power generators, set up in redundant failsafe configurations to never allow the power to be interrupted. Your home or small business setup may not warrant the expense of going all-out with this type of system, but the dangers are the same and the solution is essentially the same -- it is just a matter of scale.
Selecting a UPS
Selecting a UPS
The choice of UPS for your equipment depends on several factors: the type of equipment you have; the number and size of equipment pieces to be protected (each possibly drawing a different amount of current); the features you require (eg, communication port and smart software); and the length of "uptime" you want in the event of an outage. Sizes and specifications of various units vary tremendously, so you need to carefully consult the specifications for each make/model you are considering, taking into account the amount of power your combined equipment will draw and the time that this equipment needs to be supported. Allow a generous safety margin. Thankfully, these calculations have been made a lot easier by several UPS manufacturers, which provide online guides using databases of real Volt-Amps and Watts (or Wattage)requirements of typical devices. Simply consult the relevant Web site and fill in an interactive sizing guide with your requirements to find a type of UPS that suits (see "Sizing it up", below). Choose the right UPS technology for your situation; for simple power outage protection, off-line is the most economical type of system, and online is recommended for larger system applications. While a UPS is a good idea for almost any computer system, for many household and small business applications which don't require a powered shutdown, such as entertainment systems, a UPS could be seen as overkill. In these cases, a device that provides surge protection, line filtering (and possibly telephone/data line protection) may be adequate.
Sizing it up
Deciding what type and size of UPS best suits your needs has been made a lot easier by the following manufacturers, simply by visiting their Web sites (listed below) and filling in your requirements.
APC Systems -- sizing/type selector
Opti International Corp
Powerware (incorporating Sola Australia)
Other reference links:
MGE UPS Systems -- Apple Mac section
MGE UPS Systems -- Open Source section
Power On Australia
Natural Power Solutions
MLA Power Systems
What's the cost
What's the cost?
A UPS will vary widely in price depending on its size and feature set. But, it is no longer a luxury item. As a guide, a basic (offline) UPS (the cheapest kind) to protect a standard sort of system such as a PC, monitor and printer, you can expect to pay $100-$200, depending on capacity. The cost of a UPS can climb quickly however, as you add extra devices such as scanner, external hard drive or even additional computers, network hub/switch, router, file server, tape backup system and so on, as you will need to buy a larger UPS to provide sufficient current for the extra devices (or multiple smaller UPSs). But for those who consider that time is money, a UPS can pay for itself the first time the lights go out. Remember, there's not just the outage time to consider (which could be only a second, to over an hour) but the time to recover from lost files, corrupted systems and damaged hardware.
It is almost impossible to get natural "clean" power all the time. Following are some of the problems that can plague (and destroy) our valuable data and equipment:
This guide was last updated June 2005