UPS Working Principle and Block Diagram
UPS
UPS is a device that provides backup power when utility power fails, either long enough for critical equipment to shut down gracefully. So that no data is lost, or long enough to keep required loads operational until a generator comes online. Conditions incoming power so that all-too-common sags and surges don’t damage sensitive electronic gear.
Classification of UPS
There are mainly three varieties of UPS Systems:
- Single-conversion UPS systems
- Double-conversion UPS systems
- Multi-mode UPS systems
UPS Working Principle
1. Single-conversion UPS systems: In Single-conversion UPS systems, these feed incoming utility AC power to IT equipment. If the AC input supply falls out of predefined limits, the UPS utilizes its inverter to draw current from the battery. It also disconnects the AC input supply to prevent back-feed from the inverter to the utility. The UPS stays on battery power until the AC input returns to normal tolerances or the battery run out of power, whichever happens first.
- Standby UPS allows IT equipment to run off utility power until the UPS detects a problem, at which point it switches to battery power. Some Standby UPS designs incorporate transformers to provide limited power conditioning as well.
- Line-interactive UPS regulates input utility voltage up or down as necessary before allowing it to pass through to protected equipment. However, like standby UPSs, they use their battery to guard against frequency abnormalities.
2. Double-conversion UPS systems: The double-conversion UPS isolates critical loads from raw utility power completely, ensuring that IT equipment receives only clean, reliable electricity. In normal operation, a double-conversion UPS continually processes power twice. If the AC input supply falls out of predefined limits, however, the input rectifier shuts off and the output inverter begins drawing power from the battery instead. The UPS continues to utilize battery power until the AC input returns to normal tolerances or the battery run out of power, whichever occurs sooner. In case of a severe overload of the inverter, or a failure of the rectifier or inverter, the static switch bypass path is turned on quickly, to support the output loads.
