An Uninterruptible Power Supply (UPS) is a battery backup device used to save computer components from damage due to power problems such as power failures, spikes, and sags. Computer systems require a steady supply of electricity. Interruptions in that power can cause your systems to fail. All UPSs:
1) Switch to battery power when the input power goes higher or lower than a speciﬁed range, or use battery power to supply 2) power to connected devices and use line voltage to charge those batteries.
3) Can be conﬁgured to respond accordingly when there is a power failure.
4) Keep the computer powered up long enough for a graceful shutdown rather than an abrupt and unexpected halt.
5) Have a method for testing that the UPS works properly.
6) Must be matched to the power requirements of the connected equipment.
An online UPS supplies power to your systems from its batteries at all times. Power from the normal electrical system is used to constantly charge the batteries. Online UPSs usually supply more clean battery power than standby UPSs. However, the batteries usually do not last as long as standby UPS batteries. Online UPSs generally ﬁlter power to reduce or remove power spikes. Because online UPSs supply power from the battery at all times, they can prevent power sags or brownouts.
A standby UPS (SUPS) uses a battery to supply power when a power problem occurs. At times of normal power operation, power is supplied from the normal electrical system. This method places minimal burden on the batteries and power inverters in the UPS, leading to longer UPS life. These UPSs are rated on their switching time because their batteries are in use only when the regular power is unavailable.
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