Abstract: This article describes the design considerations and performance analysis of a new single-phase to three-phase online uninterruptible power supply (UPS) with reduced number of breakers. The proposed topology uses only 5 active switches reducing the system cost compared to traditional 10 switch topologies. The proposed UPS consists of a single-phase rectifier/charger, a two-phase/three-phase inverter connected to the load, a battery bank, a DC link capacitor and an AC inductor. The detailed operation and analysis of the circuit as well as simulation results to verify its feasibility are also presented.Keywords-Uninterruptible Power Supply (UPS); Single-phase to three-phase conversion; Reduced switchesI. INTRODUCTIONThe introduction should provide general context and a review of the article or work done by other engineers in the field. It should also contain a literature review, the objective and purpose of the document. Leave a space between two paragraphs (do not indent paragraphs). Uninterruptible power supplies (UPS) are nowadays indispensable equipment for providing energy to critical and sensitive loads. They protect sensitive loads from many disturbances existing in the utility network such as voltage variations, transients and harmonics. Applications of UPS systems include medical facilities, life support systems, data centers, emergency equipment, telecommunications and industrial processing systems. Ideally, a UPS should provide clean, uninterrupted power to the load and at the same time absorb a sinusoidal power factor, close to unity. current from the input power supply. Furthermore, static UPSs must be able to switch between service and storage batteries as alternative energy sources. This step must occur in zero or minimal time... halfway through the document...", 0-7803-7262-X/02/$10.00 Q 2002 IEEE.[20] M. Niroomand, H.R. Karshenas, " Review and Comparison of Control Methods for Uninterruptible Power Supplies,” Power Electronics and Drive Systems and Technologies Conference, PEDSTC2010, January 2010.[21] H.W. van der Broeck and J.D. van Wyk, “A Comparative Investigation of a Voltage-Minimized Inverter-Fed Three-Phase Induction Machine Drive with Different Control Options,” IEEE Trans. Ind.Appl., vol. IA-20, No. 2, pp. 309–320, March/April. 1984.[22] M. Niroomand; H. R. Karshenas, "Design and implementation of a new hybrid learning control strategy for three-phase UPS", Electrical Machines and Systems, 2008. ICEMS 2008. International Conference on, vol., no. , pp.1732-1737, 17-20 October 2008. [23] A. Emadi, A. Nasiri, SB Bekiarov. "Uninterruptible power supplies and active filters" 2005 by CRC Press LLC.