An Uninterruptible Power Supply (UPS) is an electrical device that automatically provides emergency power to a load, without delay, when the input power source fails.
A UPS provides immediate protection from power interruptions by supplying energy stored in batteries. The protection time is limited but sufficient for starting a stand-by power source or properly shuts down the equipment.
To name few of the basic elements, an UPS contains a battery that will generate power when the device senses a loss of power from the primary source, a charger and an inverter used in three alternative topologies: off-line (standby), online (no break) and line-interactive. The inverter eliminates the noise and distortion from the output wave.
An Uninterruptible Power Supply is typically used to protect computers, data centers, Media & Telecommunication equipment, elevators or other electrical equipment from power disruptions that may cause injuries or data loss.
In case the computer that you are using is protected by an UPS, it will notify you of the power loss, thus you have time to save the data and to shut it down before the buttery from the UPS runs out.
When all power runs out, any data in your computer’s random access memory (RAM) is erased. When power surges occur, a UPS intercepts the surge so that it doesn’t damage the computer.
For safety reasons and due to increased power shortage, UPSs are used for elevators in all buildings, from residential to offices, from commercial centers to entertainment parks and become a key element in the safety procedures. In the event of an electricity failure the UPS automatically senses power failure and generates power from the batteries within few second only.
HOW IT WORKS?
An UPS converts incoming Alternating Current (AC) to Direct Current (DC) through a rectifier, and converts it back with an inverter.
Batteries or flywheels store energy to use in case of a power failure. A bypass circuit routes power around the rectifier and inverter, running the IT load on incoming utility or generator power.
When power fails the batteries drive the inverter, which continues to run the information technology (IT) load. When power is restored the rectifier delivers Direct Current (DC) to the inverter and simultaneously recharges the batteries.
Utility input is completely isolated from the output, and bypass is only used for maintenance safety or if there’s an internal electronics failure. Since there is no break in the power delivered to the IT equipment, vacuum fault interrupter (VFI) is generally considered the most robust form of UPS. Most systems synchronize the output frequency with the input, but that’s not necessary, so it still qualifies as frequency independent.
Every power conversion incurs a loss, so the wasted energy has historically been considered the price of ultimate reliability. The newest VFI systems claim better than 96% efficiency at nearly all loads.