Presence of an Uninterruptible Power Supply (UPS)

From Electrical Installation Guide

The electrical power from a UPS is supplied from a storage unit: batteries or inertia wheel. This system allows us to avoid any power failure. The back-up time of the system is limited: from several minutes to several hours.
The simultaneous presence of a back-up generator and a UPS unit is used for permanently supply loads for which no failure is acceptable (Fig. D17). The back-up time of the battery or the inertia wheel must be compatible with the maximum time for the generator to start up and be brought on-line.
A UPS unit is also used for supply power to loads that are sensitive to disturbances (generating a “clean” voltage that is independent of the network).
Main characteristics to be considered for implementing a UPS:

• Sensitivity of loads to power interruptions,
• Sensitivity of loads to disturbances.

The presence of a UPS unit is essential if and only if no failure is acceptable.

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Fig. D17: Example of connection for a UPS