Uninterruptible Power Supplies - Cisco Wide Area Virtualization Engine 274 Hardware Installation Manual

Using Power Protection Devices
Line Conditioners

Uninterruptible Power Supplies

Cisco Wide Area Virtualization Engine 274 and 474 Hardware Installation Guide
B-8
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.
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.
Appendix B Maintaining the Wide Area Virtualization Engine
OL-17739-01