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The different Uninterruptible Power Supply topologies provide varying degrees of protection. There are several factors that determine which one will best fit your customers’ needs, including the level of reliability and availability they require, the type of equipment being protected and the application or environment in question. While the three most common topologies outlined below all meet the input voltage requirements for IT equipment, there are key differences in how they work as well as in the frequency and duration of demands on the battery.

Passive standby topology (off-line) is used for protecting PCs against power failure, power sag and power surge. In normal mode, the UPS supplies power to the application directly from the mains, filtered but without active conversion. The battery is charged from the mains. In the event of a power cut or fluctuation, the UPS delivers stable power from the battery.

This topology is low cost and provides sufficient protection for office environments. Passive standby topology is not suitable in cases where the power supply is of low quality (for example, on industrial sites) or subject to frequent disruptions.

Line interactive topology is used for protecting enterprise network and IT applications against power failure, power sag, power surge, under voltage and over voltage. In normal mode, the device is controlled by a microprocessor that monitors the quality of the supply and reacts to fluctuations. A voltage compensation circuit is enabled to boost or reduce the supply voltage in order to compensate for fluctuations. The main advantage of line-interactive topology is that it enables compensation for under- and over voltage without using the batteries.

Double-conversion topology (on-line) is a basis for Modular UPS designed for continuous power protection of critical equipment against all nine of the common power problems . It ensures a consistent quality of power supply regardless of disturbances in the incoming mains. The output voltage is entirely regenerated by a sequence of AC to DC conversion by DC to AC conversion in order to create power supply without any electrical interference. Double-conversion UPS   can be used with any type of equipment as there are no transients when changing over to battery power.