kVA (kilovolt-ampere)
1000 volt-amperes

Phase
Load current is drawn from a voltage source

Power range
Generally segmented by low range (below 5 kVA), mid-range (5–20 kVA) and high range (above 20 kVA)

Line-interactive UPS systems
are similar to standby UPS systems but also provide constant monitoring of the integrity of utility power and reduce or provide voltage whenever it should rise too high or fall too low

Modular UPS systems are characterised by their building-block architecture, which allows for space-saving vertical scalability as opposed to (only) horizontal scalability of stand-alone UPS systems

MTTR (mean time to repair)
The average time between a device’s failure and its return to service

Near-zero downtime or outage
The ability to minimise a period of time or a percentage of a time span that a system is unavailable or offline to almost zero

Online UPS systems are suitable for critical loads. They ensure clean and regulated voltage to the load by means of a rectifier

Redundancy in engineering is the duplication of critical components of a system with the intention of increasing reliability, usually in the case of backup or fail-safe components

Scalability
The increase of capacity by simply adding a module

Single-phase power
(typically 120 or 230 VAC depending on the country) is carried between two wires, live and neutral, and sometimes a third (ground) wire for safety. The frequency of AC voltage is 50 or 60 Hz depending on the country

Stand-alone UPS systems
are free-standing systems that operate independently

Standby UPS systems
switch from utility to battery power only when the utility power fails

Three-phase power
An electrical system possessing three different voltage lines with sine waveforms that are shifted by 120 degrees from phase to phase

Transformer
A device used to change the voltage of AC power or to isolate a circuit from its power source

Transformer-based
Traditional technology based on transformers

Transformer-less
Innovative three-phase technology without transformers

UPS – uninterruptible power supply
A general term used to describe any of the various types of standby power