Uninterruptible Power Source
From Unofficial BOINC Wiki
[edit] General
A source of emergency power that is used when the main supply of power is interrupted. In function it serves the same purpose as does an Standby Power Source (SPS). The main difference is that the Uninterruptible Power Source is always connected to the protected system. There is no delay between the detection of the interruption or other disturbance on the input side before the Uninterruptible Power Source provides power to the protected system. Like a SPS, the Uninterruptible Power Source stores energy in batteries and uses them to create the power during a disturbance, recharging them after the disturbance has ended. Also like the SPS, the main goal is not to provide long-term power replacement, but is to bridge the gap between the disturbance of power until other alternative power sources can be brought on-line or the protected systems can be shut–down in an orderly manner. Usual endurance for the Uninterruptible Power Source to provide power are about 10 to 15 minutes.
This provides sufficient protection to insure the minor disturbances can be bridged without compromising the availability of the computer system. Because of their constant presence on–line at all times, spikes and other short–term power disturbances are filtered out and the protected system is always getting a clean and stable source of input power. For very delicate systems this filtering is a requirement and therefore the Uninterruptible Power Source is used instead of the SPS. For systems of this nature, the Uninterruptible Power Source will bridge the gap between the loss of primary power and the bringing on–line of some sort of local generator.
When I worked on a radar system for the US Air Force the transmit site had a standby dam to provide power if the first dam broke. The computer systems (28 VAX Machines) had a SPS system that used a room full of car batteries and they had 2 diesel electric generators (in case one failed or was down for maintenance).
A "true" Uninterruptible Power Source costs more than an SPS of equivalent capacity. Most "Uninterruptible Power Source" systems sold to the low end of the market (that is you and me as private individuals) are in–fact only an SPS.
