Uninterruptible Power Supply (UPS)
An uninterruptible power supply (UPS) maintains power to critical loads during mains failures, sags, surges and other disturbances by drawing on stored energy, usually from VRLA or lithium-ion batteries. In a double-conversion (online) UPS, a rectifier converts incoming AC to DC, charging the battery and feeding an inverter that continuously regenerates clean AC, so there is no transfer time when the mains fails; a static bypass supplies the load during overloads or internal faults. Line-interactive and offline (standby) topologies are simpler and switch to the inverter only when the mains is lost. IEC 62040-3 specifies UPS performance classification and test methods. Selection parameters include rated output in kVA and kW, output power factor, topology, battery autonomy at the expected load, input and output voltage, efficiency, redundancy configuration (N+1, 2N) and parallel capability.
Examples
- Online double-conversion UPS for a server room
- Parallel redundant UPS system for process control
- Industrial UPS backing up DCS and safety systems