ItemSolid-State Fault Current Limiting for DC Distribution Protection(2017-06-15) Qi, L.; Pan, J.; Huang, X.; Feng, X.This paper discusses solid-state fault current limiting technologies. Both solid-state fault current limiters and converters can quickly limit DC fault currents and permit other protective devices to perform appropriate fault interruption and/or isolation. Different system protection strategies using solid-state fault current limiters and converters are presented and analyzed. The advantages and disadvantages of different methods are also discussed and compared. ItemExperimental Test bed to De-Risk the Navy Advanced Development Model(2017-06-15) Strank, S; Feng, X; Gattozzi, A; Wardell, D; Pish, S; Herbst, J; Hebner, R.This paper presents a reduced scale demonstration test-bed at the University of Texas’ Center for Electromechanics (UT-CEM) which is well equipped to support the development and assessment of the anticipated Navy Advanced Development Model (ADM). The subscale ADM test bed builds on collaborative power management experiments conducted as part of the Swampworks Program under the US/UK Project Arrangement as well as non-military applications. The system includes the required variety of sources, loads, and controllers as well as an Opal-RT digital simulator. The test bed architecture is described and the range of investigations that can be carried out on it is highlighted; results of preliminary system simulations and some initial tests are also provided. Subscale ADM experiments conducted on the UT-CEM microgrid can be an important step in the realization of a full-voltage, full-power ADM three-zone demonstrator, providing a test-bed for components, subsystems, controls, and the overall performance of the Medium Voltage Direct Current (MVDC) ship architecture. ItemPower Converter Design Options for the 12kVdc Bus System(2017-06-15) Gattozzi, A.L.; Strank, S.M.; Pish, S.P.; Hebner, R.E.; Engelkemeir, F.D.The US Navy’s recent reduction of the dc bus voltage for the new surface combatant, from the original 20 kV to the new target of 12 kV, opens up the design space to a broader range of options than was possible to date. This paper is an attempt to address the opportunities and risks associated with the adoption of multi-level topologies and Silicon-Carbide switches in the design of power converters for the new ships when compared with a more evolutionary innovative path offered by using soft-switching topologies with Silicon switch technology. ItemElectrical and Thermal System Considerations for MVDC Superconducting Distribution on Navy Ships(2017-06-15) Hebner, R.E.; Gattozzi, A.L.; Strank, S.M.; Pish, S.P.; Herbst, J.D.The interest in using a superconducting (SC) distribution grid on a ship designed with a medium voltage dc (MVDC) system is a natural one, because superconductors (SCs) perform at their best under dc power. The potential advantages could be reduced losses, smaller cable plant size, and an electrically stiffer power bus. However, the use of SCs, does not eliminate losses completely and requires additional ancillary equipment. This paper provides an initial assessment of the potential benefits accrued from its adoption compared to any additional overhead, residual losses, and risk associated with a brand new shipboard system. ItemFault Inductance Based Protection for DC Distribution Systems(2016-03) Feng, X.; Qi, L.; Pan, J.The fault protection is a critical element to ensure the reliable and secure operation of DC distribution systems. Most DC distribution systems are tightly coupled systems with low line impedances which may result in fast current increase during a fault. Thus, it is challenging to develop a fast and reliable DC fault protection method. This paper proposes and develops a novel fault inductance based DC protection method without communication between protection units at different locations. The performance of the developed protection algorithm was validated in a Real-Time Hardware-In-the-Loop (RTHIL) test platform. The testing results indicate that the developed inductance based fault location algorithm detects and locates faults with fast speed and high accuracy. Preliminary sensitivity analysis on measurement errors are also conducted to study impacts on accuracy of estimated fault inductance. ItemResearch and Development of High Performance Current Collectors for Homopolar Generators(1985-10) Gully, J.H.; Walls, W.A.Over the past five years three homopolar generators (HPGs) have been operated in our laboratory under a variety of experimental conditions. Two of the machines were routinely used as pulsed power supplies, the third machine is an experimental facility for the development of HPG components. Because of the Center for Electromechanics at The University of Texas at Austin (CEM-UT) recent move into a new facility, all three of the machines have been disassembled and inspected offering a wealth of information on the performance of high-slip-speed, high current- density current collectors. Wear rates of sintered, copper-graphite brushes running on steel slip rings as a function of current density and slip speed will be presented along with effects of slip-ring surface finish, using the brushes as a switch to close the electrical circuit and direction of current transfer. Funding for this research has been provided by the U. S. Army Research and Development Command (ARDC), Defense Advanced Research Projects Agency (DARPA), National Science Foundation (NSF), and the Texas Atomic Energy Research Foundation (TAERF). ItemHomopolar Pulse Welding of Rail(1983-11) Aanstoos, T.A.; Weldon, J.M.The homopolar pulse welding process uses a single unidirectional, high current electrical pulse from a homopolar generator to heat the interface between two workpieces in solid contact. When the interface reaches an optimum temperature, forging pressure is applied, and the workpieces coalesce without melting and without use of either a flux or a filler. The weld is completed in from 1 to 2 s. Because current distribution and heat generation can be made uniform throughout the workpiece section, irregular sections such as rails can be welded. Ninety lbm/yd rail has been welded with the process using a 10 MJ homopolar generator. The welds were excellent metallurgically, but there were fixturing problems with mechanical clamping, alignment, and current delivery. A through-feeding fixture for welding pipe has been designed and built that successfully addresses these fixturing problems, and electrical contacts and clamps for welding rails are presently being designed. A compact system that could serve as the power supply for an in-track rail welding system has recently become commercially available. ItemTransient Overvoltages on Rotary Flux Compressor/Compensated Pulse Alternator Windings(1983-06) Pratap, S.B.; Brown, D.R; Bird, W.L. ItemDesign, Fabrication, and Testing of a Liquid Nitrogen-Cooled Aluminum Inductor(1983-06) Zowarka, R.C. ItemElectromagnetic Thrust Bearing for a Homopolar Machine: Experimental Implementation(1974-05) Islam, Z.; Driga, M.D; Rowberg, R.E; Woodson, H.H.Development of large, inertial pulsed power supplies is essential to the success of the controlled thermonuclear research program. A very attractive candidate for this supply is the homopolar motorgenerator which can produce the large current pulses (~lOOKA) necessary for the confinement and compression magnetic fields needed on the large fusion feasibility experiments. For a radial current flow, axial magnetic field configuration, the machine rotor is unstable to movement in the axial direction. Therefore a large mechanical thrust bearing is normally used which adds to the frictional losses and reduces the machine's efficiency. However, these losses could be reduced substantially by replacing the mechanical bearing with an electromagnetic thrust bearing. This report discusses the experimental implementation of an electromagnetic thrust bearing on the 0.5MJ homopolar machine presently in operation at The University of Texas at Austin. A control system describing the electromagnetic thrust bearing is formulated and the system stability is determined. The circuitry is then described which produces the required differential field current and monitors the position of the rotor. The latter is done by a position sensing unit consisting of an LED and a phototransistor. The former is done with an operational amplifier circuit that generates equal and opposite voltages which drive the two SCR field supplies in a manner to create the required differential current. For a static rotor, test results show that a restoring force is generated and that the rotor can be stabilized against the axial forces. ItemAssembly and Testing of a Compact, Lightweight Homopolar Generator Power Supply(1983-06) Gully, J.H. ItemThe Design of a Pulsed Homopolar Generator Power Supply for a High Current Laboratory(1983-06) Bird, W.L.; Morgan, C.A; Floyd, J.E; Aanstoos, T.A.; Weldon, W.F. ItemThe Rebuilding and Testing of an Active Rotary Flux Compressor(1983-04) Spann, M.L.; Bird, W.L; Weldon, W.F; Woodson, H.H. ItemDesign of a Compact Inductor Matched to a Homopolar Generator(1983-04) Gully, J.H.; Pratap, S.B; Spann, M.L; Weldon, W.F; Woodson, H.H.