Design of a Passive Cooling System for a Solid-State 15kV / 100kVA Intelligent Universal Transformer

As the use of alternative energy sources increases globally, there exists a need for a smart grid system to handle the increased power capacity. As part of this new power grid, a new type of intelligent universal transformer (IUT) has been developed to enhance power quality, throughput and efficiency to tackle green initiatives and enable distribution automation based on a control system. Using solid-State technology, specifically the SGTO module developed by the Electronic Power Research Institute (EPRI) and Silicon Power Corporation (SPCO), the IUT has the capacity to better optimize the existing transmission system while simultaneously delivering reliable diverse power, such as 400Hz service, DC service for hybrid-electric (plug-in) vehicles and three-phase power from a single phase line. This paper explores the thermal challenges associated with the design of the intelligent universal transformer, specifically designing for a high system heat load of 6 kW in an ambient temperature of 50°C. The system must use natural convection to prevent the use of mineral oils in a forced convection case such that there is no ecological concern. The system must also meet weight constraints, sufficiently handle a common household current draw of 110A and uphold its structural integrity. The high system heat load is applied using IcePak and a sufficient design is solved for numerically using FLUENT.