Uninterruptable Power Systems
An uninterruptible power supply (UPS) is an electrical apparatus that provides emergency power to a load when the input power source or mains power fails. The on-battery run-time of most uninterruptible power sources is relatively short (only a few minutes) but sufficient to start a standby power source or properly shut down the protected equipment. It is a type of continual power system.
A UPS is typically used to protect hardware such as computers, datacenters, telecommunication equipment or other electrical equipment where an unexpected power disruption could cause injuries, fatalities, serious business disruption or data loss. UPS units range in size from units designed to protect a single computer) to large units powering entire data centers or buildings.