A Guide to UPS

No, don't think package deliveries from brown trucks. Think delivering your computer system from potential devastation caused by brownouts, power surges, and other power interruptions. A lowdown on choosing a UPS -- uninterruptible power source -- and saving your data through the long, hot summer.
By D.E. Levine

What is a UPS?

As power outages roll across the west coast and rumors abound that there will be similar outages in the east, we take a look at why and how an uninterruptible power source can save your data and your peace of mind. Regardless of which operating systems you're running at the office or at home, and no matter how well you maintain your network, unexpected events can place your data in jeopardy.

UPS stands for uninterruptible power source, a device that sits between a power supply and a device such as computer. The purpose of an UPS is to prevent undesired interruptions of the power source, such as outages and power surges, from adversely affecting your computer or your network.

UPSs help your computers remain temporarily operational when changes to the power supply would otherwise interrupt their function. Having a device that can buy you a bit of "up time" (allow your computers to run temporarily) can prevent damage to or loss of data due to the power loss. The UPS provides time for the operator, administrator, or owner to power the unit down safely without damage to the equipment or data.

UPSs come in different shapes and sizes, ranging from a 9-volt battery to a building-wide backup generator. In this tutorial we'll uncover which of these protective devices can be installed and handled by an administrator and which by a home computer user.

Three different types of devices are commonly referred to as UPSs.

1. Standby power supply (SPS), or an offline UPS. This refers to a supply where power is derived directly from the power line until the power fails. When the power fails with this type of supply, a battery-powered inverter turns on and continues supplying power. The batteries are charged when line power is available.

These devices are cheaper than other solutions. Disadvantages include the switchover time (the time required for the inverter to come online), which varies from one unit to another -- so check this carefully prior to purchase. Another disadvantage is that because the units are generally connected directly to the power line, an SPS provides relatively poor protection from line noise, line spikes, frequency variations, and brownouts.

2. Hybrid or line-interactive UPS systems. These use the power line to condition a ferroresonant transformer. It is this transformer that acts as an automatic voltage regulator (AVR) standing between the AC input and AC output. The AVR maintains a constant output voltage regardless of whether the input voltage varies. In other words, when the voltage falls outside of a particular band, the UPS' microprocessor moves automatically to draw off the battery.

Besides providing good protection against line noise, a major advantage of the hybrid UPS is that the transformer maintains output briefly when a total outage occurs. This type of UPS protects against sags and brownouts that make up 80 percent of all power disturbances. A disadvantage is that the ferroresonant transformer in the UPS can interact with the ferroresonant transformers in your equipment and result in unexpected, and sometimes unfavorable, results.

3. True or online UPSs. These refer to a system that continuously operates from an inverter. This type of UPS provides the highest level of power protection by using a combination of a double-conversion (AC to DC/DC to AC) power circuit with the inverter to continuously power the load.

The upside: no switchover time; digital-quality power not possible with offline SPS systems; and generally the best isolation from power line problems. Disadvantages: cost; more heat generation; and more power consumption.

While you might start questioning the reliability of these units because the inverter is always in use or "on," studies by manufacturers and users show that these UPSs are unaffected by the power usage.

Features of a UPS

Because it has internal batteries, the UPS can provide power (for a limited amount of time) even when the power fails completely. While a few minutes may seem insignificant, if you've ever been in this situation, you know it gives you time to power down and save the data when a major power failure occurs.

Some UPS units or UPS software provide extra features, such as automatic shutdown of equipment for longer power outages, monitoring and logging the status of the power supply, displaying the voltage/current draw of the equpment, automatic restarting of equipment following a power outage, displaying the current voltage on the line, providing alarms on some error conditions, and providing protection against short circuits.

Which UPS is right for you? It depends on the kind of computer you're protecting and the size of the UPS. Generally, the average UPS for a workstation or desktop computer provides 15 minutes of power to the machine.

There are many different manufacturers of UPS units, each offering varying capabilities and prices. Don't be intimidated about approaching with questions. Most of these manufacturers have broad experience with users who have different needs and budgets. But it's a good idea to research each vendor before any purchase.

Remember that all UPS units use software that must be installed and integrated with your operating system. Check to make certain that the manufacturer's unit will work with your version, that there are clear instructions for installation and maintenance, and that the manufacturer is reliable and will support the hardware and software.

Do I Need a UPS? Domestic Power Issues

Do you need a UPS? UPS manufacturer Belkin -- which admittedly has a vested interest in the issue -- provides the following statistics:

1. The average U.S. home or office receives 264 power disturbances a year. Certain areas that are more prone to distubances endure more than 400 disturbances annually. Internationally, those numbers triple, according to IBM.

2. Irregular power due to an under-voltage of line power -- that is, brownouts -- cause four out of five disturbances.

3. The leading causes of data loss are power failure/surge (45.3 percent), storm damage (9.4 percent), fire/explosion (8.2 percent), hardware/software error (8.2 percent), flood & water damage (6.7 percent), earthquake (5.5 percent), network outage (4.5 percent), human error/sabotage (3.2 percent), HVAC failure (2.3 percent), and miscellaneous (6.7 percent).

Costs to protect a home computer will likely fall between $50 and $200. Protection for your network will be higher depending on its complexity.

Ultimately, when determining whether or not you need a UPS, and what type to buy, consider how much an unexpected power failure would impact your business.






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