DELL WorkStation 210 ユーザーズマニュアル

ページ / 234
Maintaining the System
D-9
6XUJH3URWHFWRUV
Surge protectors are available in a variety of types and usually provide a level of pro-
tection 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.
/LQH&RQGLWLRQHUV
Line conditioners go beyond the overvoltage protection of surge protectors. Line con-
ditioners 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.
8QLQWHUUXSWLEOH3RZHU6XSSOLHV
Uninterruptible power supply (UPS) systems offer the most complete protection 
against variations in power because they use battery power to keep the system run-
ning 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.