A UPS (uninterruptible power supply) is a continual power system. This electrical apparatus provides emergency power to a load when the input power source or mains power fails. It differs from an auxiliary or emergency power system or standby generator in that it will provide near-instantaneous protection from input power interruptions by supplying energy stored in batteries, supercapacitors or flywheels.
A UPS is typically used to protect hardware such as computers, data centres, telecommunication equipment or other electrical equipment in situations 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 without a video monitor to large units powering entire data centres or buildings. The various components of a UPS are crucial for the stable operation of the power supply.
A wide variety of UPS accessories are available, including alarm beacons, battery packs, bypass switches, door switch sensors, network cards, replacement battery cartridges, temperature sensors and vibration sensors.