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Recent uninterruptible power supply (UPS) systems, in the medium power range (a few 100 kW), are based on a three-power stage topology including a rectifier, an inverter, and a dc-dc converter. The dc-dc converter ensures the charger/discharger function necessary for battery management. The monolithic intercell transformer (ICT) described in this paper is dedicated to such a charger/discharger, of which the nominal power is 137 kW. This dc-dc converter is comprised of eight interleaved cells that are interconnected by the ICT. The first part of this paper briefly presents the full UPS system and the topology of the eight-cell charger/discharger arranged around the eight-phase monolithic ICT. The second part suggests a model and emphasizes the design specificities of the monolithic ICT. The final design is provided by an optimization routine, checked in the end by different 2-D and 3-D finite-element simulations, both electromagnetic and thermal. The third part describes the construction of the ICT prototype. It is then placed in a test bench that reproduces the conditions of future operations and provides current balance conditions. Finally, the experimental results obtained for the 137-kW nominal power validate design parameters and confirm the interest of the ICT solution. [ABSTRACT FROM AUTHOR]

Efficiency of high-power uninterruptible power supplies (UPSs) is a fundamental criterion regarding the permanent use of such a device. A state of the art on soft switching over constraint of UPS application has been made. The principle of auxiliary resonant commutated pole using autotransformer has been identified as the most interesting way to increase efficiency or switching frequency. Its application for multilevel converters has been studied. A simplified resonant pole has been proposed for a three-level rectifier used as power factor corrector. The design criteria have been discussed. A single phase of a 200-kVA three-level rectifier has been realized and qualified in switching mode. To assess the gain of this principle, the switching losses have been measured on the prototype in both hard and soft switching. The switching losses have been divided by two. [ABSTRACT FROM AUTHOR]