61 research outputs found
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Pulsed magnetic flux compression power supplies for hypervelocity powder deposition
After reviewing the process of hypervelocity plasma deposition using augmented railgun technology, the paper presents several new concepts of pulsed rotating electric generators designed to power, on an almost continuous basis, the laboratory system designed and built at The University of Texas Center for Electromechanics (UT-CEM), which successfully validated the method and conducted proof-of-principle experiments. The two different rotating, repetitive pulsed power supplies described in the paper are: (1) an actively compensated flux compressor-alternator (actively compensated compulsator) and (2) a dc machine with series excitation, which so far did not have any application as a generator but proves, due to its self-excitation particularities, to be an almost ideal power source for the railgun. It needs to be emphasized that the augmented railgun and the actively and passively compensated compulsators represent almost mature technologies due to the continuous development of electromagnetic launch technology by the U.S. Department of Defense and especially by the U.S. Army – ready to be applied to many advanced civilian applications as it is the case with the hypervelocity powder railgun accelerators for surface conversion.Center for Electromechanic
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25 GW Homopolar Generator Experiment
Early in the design iterations for the Balcones 60 MJ power supply different options were considered, from a single machine to modular homopolar generators (HPGs).[1] A multiple machine option was chosen to provide greater system flexibility. Envisioned uses for the power supply were to weld up to 100 in.2 of metal, heat a 100 lb steel billet to forging temperature in 2 to 4 s, and conduct high level electromagnetic gun experiments.[2] A study involving detailed computer optimization compared drum type HPGs to disk type machines. For fixed location (such as large proof of principle laboratory experiments) the higher energy transfer efficiency and lower cost perjoule delivered made the drum configuration more attractive. The compact disk design was better for mobile applications where minimum mass is the primary consideration.[3] The six drum HPGs installed in the underground hexagonal pit in the Balcones lab are shown in figure 1.Center for Electromechanic
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Hypervelocity Powder Deposition using Pulsed Power Magnetic Flux Compression Devices
This paper outlines two original concepts which, in combination, can bring fundamental advances to both manufacturing and materials technologies and the pulsed power approach to them, and describes a laboratory system already built which has conducted proof-of-principle experiments. The first novel concept uses a hypervelocity accelerator for a new thermal spray process using electromagnetic forces to accelerate powder particles to velocities of 2 km/s or higher, more than twice that of the powder velocities of about 1 km/s used by the existing state-of-the-art thermal spray processes (HVOF, D-gun, plasma spray) which are limited by their reliance on the thermodynamic expansion of gases. The second original concept is a pulsed power supply, a new electrical machine-flux compressor with precisely controllable output capable of matching ideally the powder spraying hypervelocity accelerator at any moment of time. Due to the compensation systems, the compulsators are low internal impedance machines designed for pulsed duty and capable of providing large current pulses, with a rapid rise time (in our case, less than 25 /spl mu/s to 80 MW pulsed power) to a low impedance load-a hypervelocity square bore railgun accelerator (SBA) assuring an almost continuous process. After describing the results of some experiments confirming system modeling and performance, the paper concludes with future directions of this research.Center for Electromechanic
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Nine-Phase Armature Windings Design, Test, and Harmonic Analysis
A nine-phase armature winding was developed for a large generator. Alternative methods for interconnecting the pole-phase groups were examined. An alternate-pole connection scheme was adopted and a prototype induction motor was constructed to confirm the winding scheme. Since only a three-phase power source was available for testing, the induction motor was tested by using three, three-phase winding sections, one at a time. Air-gap harmonic fields produced some unusual results. These test results and harmonic analyses to explain them are presented herein. The tests confirmed the nine-phase winding scheme that was adopted. The harmonic analyses revealed that the complete nine-phase winding exhibited a very low harmonic content, a distinct advantage of a nine-phase winding for future applications.Center for Electromechanic
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Hypervelocity Electromagnetic Gun Development at CEM-UT
Interest in railguns at the Center for Electromechanics at The University of Texas at Austin (CEM-UT) was the result of a visit to the railgun facility at the Australian National University (ANU) at Canberra in 1979. Soon after that visit the concept of a Distributed Energy Store (DES) railgun was invented and the first injected railgun was tested at CEM-UT. When railguns were introduced into the defense community in 1980, the technology started to grow in the United States. With the announcement of the Strategic Defense Initiative (SDI), electromagnetic launcher research took another quantum step. Today CEM -UT is actively testing state-of-the-art launchers on the pulsed power supplies developed at CEM- UT over the past twelve years. In addition, CEM-UT is preparing for the future with the installation of the Balcones Homopolar Generator Power Supply and by maintaining programs in state-of-the-art rep- rated power supply development and hypervelocity launch. A detailed description of the CEM- UT facility is presented in Appendix A at the end of the text.Center for Electromechanic
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Design, Analysis, and Fabrication of Two Lightweight, High L’ Railguns
Design, analysis, and fabrication of two railguns with 90 and 30 mm bores utilizing a laminated containment structure are discussed. Laminations are insulated from each other by layers of sheet adhesive, and a composite overwrap is applied to the laminations for longitudinal stiffness. The 90 mm-bore gun is being fabricated for testing as the 9 MJ range gun. Performance specifications for the 90 mm-bore gun are 3.2 MA peak current, 4.0 km/s maximum velocity, and 12 MJ muzzle energy. The 30 mm-bore gun is a one-third scale version of the 90 mm-bore gun, built to develop construction techniques and verify performance. It is designed to be operated at 1 MA with a maximum muzzle energy of 400 kJCenter for Electromechanic
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Induction motor performance testing with an inverter power supply, part 1
The development of high-power density electrical machines continues to accelerate, driven by military, transportation, and industrial needs to achieve more power in a smaller package. Higher speed electrical machines are a recognized path toward achieving higher power densities. Existing industry testing standards describe well-defined procedures for characterizing both synchronous and induction machines. However, these procedures are applicable primarily to fixed-frequency (usually 60 or 50 Hz) power supplies. As machine speeds increase well beyond the 3600-rpm limitation of 60-Hz machines, a need for performance testing at higher frequencies is emerging. An inverter power supply was used to conduct a complete series of tests on two induction motors (0.5 and 1.0 MW) with speeds up to ~5000 rpm. The use of a nonsinusoidal power supply with limited power output capability required the development of measurement techniques and testing strategies quite different than those typically used for 60/50 Hz testing. Instrumentation and techniques for measuring voltage, current, and power on harmonic rich waveforms with accuracies approaching 1% are described. Locked-rotor and breakdown torque tests typically require large kVA input to the motor, much higher than the rated load requirement. An inverter sized for the rated load requirements of the motor was adapted to perform locked-rotor and breakdown torque tests. Inverter drive protection features, such as anti-hunting and current limit that were built into the inverter had to be factored into the test planning and implementation. Test results are presented in two companion papers. This paper (Part 1) correlates test results with the results of an algorithmic induction motor analysis program. Part 2 presents the test results compared with a Matlab simulation program and also provides a comprehensive discussion of the instrumentation that was essential to achieve testing accuracy. Correlating test results with calculated valu- es confirmed that the testing techniques developed during this testing program are useful for evaluating high-speed, high-power density electrical machineryCenter for Electromechanic
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Electromagnetic and Structural Analyses of an Integrated Launch Package
In this paper, detailed three-dimensional (3D) transient electromagnetic (EM) analyses with temperature-dependent material properties were performed using a state-of-the-art analysis tool to calculate current densities, body force densities, and temperature distribution in launch package and rail conductors. The body force densities, temperature distribution, and package accelerations generated by the EM model were then provided to a 3D multiple-step nonlinear static structural model for detailed mechanical analyses. The combined 3D EM and structural analyses can be used to accurately predict the EM launching performance and launch package structural integrity. Furthermore, armature optimization and package survivability enhancement can also be achieved with the help of these analysesCenter for Electromechanic
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Pulsed Power Accelerators at CEM-UT
An overview of four accelerator programs utilizing pulsed power is presented. The goals of each project, a description of the power supplies and launchers utilized and test results from each program are provided. The four projects presented illustrate a variety of uses for electromagnetic (EM) launchers and the potential advantages and disadvantages of four different launcher systems. Included in the paper are micrometeorite impact studies of 50 to 500 μm diameter glass beads accelerated up to 11 km/s with plasma armatures and 2.5- kg solid armature packages launched at 2.6 km/s (a record 8.1 MJ of muzzle energy). A compact rep-rateable augmented rail launcher and compulsator system weighing less than 1,100 kg is also described. Finally a skid mounted rep-rateable launcher system capable of providing 9 MJ of muzzle energy is discussed.Center for Electromechanic
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Rotordynamics Design and Test Results for a Model Scale Compulsator Rotor
The model scale compulsator is a high speed (12000 rpm), high energy rotating machine. The rotor is a highly optimized pulsed power electrical machine consisting of electrical windings, slip rings, and highly pre-stressed composite bandings. This paper describes the design of this machine from the standpoint of rotordynamics. The rotor is supported on oil-lubricated hybrid ceramic duplex ball bearings, which in turn are supported on compliant squeeze film dampers. Test results are presented for both mechanical checkout runs and full energy discharge experiments. Also described is experience gained from low speed balancing on a commercial balancing machine, followed by high speed in situ balancingCenter for Electromechanic
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