<p>In this paper, the optimal design procedure for a high-efficiency three-phase four-wire large-capacity 500&#xa0;kW uninterruptible power supply using large-capacity silicon carbide power semiconductor modules in the power conversion part of the rectifier and inverter is presented. In order to use large-capacity silicon carbide power semiconductor modules most effectively in the power converters, an optimal design that combines the electrical design stage that determines electrical performance and the heat dissipation design stage that determines the thermal stability and operation reliability is essential. Hence, the optimal design procedure is presented that considers the interrelated parameters between the electrical design stage to determine the filter performance of uninterruptible power supply and optimal driving parameters of the silicon carbide power semiconductor module and the thermal design stage to determine the optimal heatsink shape. According to the proposed optimal design procedure, a three-phase, four-wire large-capacity 500&#xa0;kW UPS is designed to satisfy the given design target specifications as a case study. In order to verify the validity of the proposed design procedure, the current ripple factor of filters and heat distribution on the heatsink are preliminary verified by the simulation softwares. Also, 500&#xa0;kW prototype UPS designed according to the proposed design procedure is produced and experimentally verified by measurements of electrical characteristics, overall system efficiency and heatsink temperature.</p>