An Online UPS System That Eliminates the Inrush Current Phenomenon While Feeding Multiple Load Transformers

Numerous industrial facilities involve the installation of load transformers with their respective loads. As these loads are engaged and disengaged, their transformers are also energized and de-energized, respectively. An inrush current, which typically occurs when a transformer is energized, can easily be observed for an online uninterruptible power supply (UPS) system feeding such loads. This paper proposes an online UPS system that eliminates the inrush current phenomenon caused by the switching-in of the load transformers. The UPS inverter specifically utilizes a fast acting current control scheme which enables it to regulate the load current during all energizing conditions of the load transformer connected to the UPS system. Experimental results are provided to validate the effectiveness of the proposed UPS system.