This International Standard applies to movable, stationary and fixed electronic uninterruptible power systems (UPS) that deliver single or three-phase fixed frequency a.c. output voltage not exceeding 1 000 V a.c. and that incorporate an energy storage system, generally connected through a d.c. link.This standard is intended to specify performance and test requirements of a complete UPS and not of individual UPS functional units. The individual UPS functional units are dealt within IEC publications referred to in the bibliography that apply so far that they are not in contradiction with this standard.The primary function of the UPS covered by this standard is to ensure continuity of an a.c.power source. The UPS may also serve to improve the quality of the power source by keepingit within specified characteristics. UPS have been developed over a wide range of power, fromless than hundred watts to several megawatts, to meet requirements for availability andquality of power to a variety of loads. Refer to Annexes A and B for information on typicalUPS configurations and topologies.This standard also covers UPS test and performance when power switches form integral part of a UPS and are associated with its output. Included are interrupters, bypass switches, isolating switches, and tie switches. These switches interact with other functional units of the UPS to maintain continuity of load power.