Dell Precision WorkStation 210, Руководство пользователя

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Maintaining the System D-9
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Surge protectors are available in a variety of types and usually provide a level of
protection commensurate with the cost of the device. Surge protectors prevent
voltage spikes, such as those caused during an electrical storm, from entering a
system through the electrical outlet. Surge protectors, however, do not offer
protection against brownouts, which occur when the voltage drops more than
20 percent below the normal AC line voltage level.
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Line conditioners go beyond the overvoltage protection of surge protectors. Line
conditioners keep a system’s AC power source voltage at a fairly constant level and,
therefore, can handle brownouts. Because of this added protection, line conditioners
cost more than surge protectors—up to several hundred dollars. However, these
devices cannot protect against a complete loss of power.
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Uninterruptible power supply (UPS) systems offer the most complete protection
against variations in power because they use battery power to keep the system
running when AC power is lost. The battery is charged by the AC power while it is
available, so once AC power is lost, the battery can provide power to the system for a
limited amount of time—from 15 minutes to an hour or so—depending on the UPS
system.
UPS systems range in price from a few hundred dollars to several thousand dollars,
with the more expensive units allowing you to run larger systems for a longer period
of time when AC power is lost. UPS systems that provide only 5 minutes of battery
power let you conduct an orderly shutdown of the system, but are not intended to
provide continued operation. Surge protectors should be used with all UPS systems,
and the UPS system should be Underwriters Laboratories (UL) safety-approved.