Browsing by Subject "armature"
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Item A 10-MJ Active Rotary Flux Compressor for Driving Xenon Flashlamps(1983-04) Morgan, C.A.; Bird, W.L; Weldon, W.F.Item An Actively Switched Pulsed Induction Accelerator(IEEE, 1991-01) Ingram, M. W.; Andrews, J. A.; Bresie, D. A.A coaxial accelerator which will launch a 45 mm diameter, 225 g-mass to 2000 m/s is described. The launcher is a true induction device, as no current feed to the armature is provided. The armature is a multiturn design, which forces a uniform current density and prevents excessive heating at the rear of the armature. To meet the 450 kJ launch goal, the accelerator is composed of 47 separate stages. Each stage has its own capacitor power supply, which is discharged on the arrival of the armature. The system uses a sense and switch approach to ensure correct timing of the power supply discharges. In-bore armature position is detected using fiber optics; the necessary signals are fed into a programmable controller, which determines the velocity. Using the calculation, the controller determines the ideal time to fire the next stage and initiates the discharge at the appointed time. The accelerator described is roughly 38% efficient (kinetic energy/stored energy) with a bore diameter of 45 mm. Simulations indicate efficiencies over 55% are possible with al 60 mm bore launcher and continue to increase with larger bore sizes. The launcher and armature designs, power supply, and controls are discussed. Predicted performance of a five-stage launcher currently being built is presented. Experimental results from single-stage tests are presented and compared to simulated results. Solid (monolithic) and multiturn (wound) armature tests are also describedItem Applying a Compensated Pulsed Alternator to a Flashlamp Load for NOVA-Part II(1979-06) Bird, W.L.; Mayhall, D.J.T; Weldon, W.F; Rylander, H.G; Woodson, H.H.The compensated pulsed alternator (compulsator) has been proposed as a possible alternative to capacitor banks for driving xenon flashlamps for pumping neodymium glass laser amplifiers for NOVA. An algorithm for sizing rotor diameter and angular velocity as a function of flashlamp impedance, peak current, and delivered energy is described. It is shown that the armature inductance variation is a major consideration when matching the pulsed alternator to the load. Finally, conceptual design parameters of a four pole, laminated rotor compulsator are presented.Item Armature Design for Coaxial Induction Launchers(IEEE, 1991-01) Andrews, J. A.; Devine, J.It has been demonstrated that, in a coaxial induction accelerator, multiturn armatures offer significant advantages over monolithic solid sleeves. The overall armature temperature rise can be reduced by over an order of magnitude, and efficiency can be increased from around 15% to over 40%. Solid armature support structures appear to offer more promise than annular designs, since they can tolerate 41% more magnetic field. However, solid structures require shorting the armature leads to each other on the armature surface, rather than on the centerlineItem Coilgun Structures(IEEE, 1993-01) Andrews, J.A.;Research on coilguns at the Center for Electromechanics at the University of Texas at Austin (CEM-UT) has yielded considerable insight into the optimal design of coilgun structures. This research has indicated that the structural requirements are strong functions of launcher classification as well as acceleration mode. As a result, CEM-UT has built and tested the DC coaxial accelerator (DCA) coilgun, which is a multistage pulsed induction launcher that makes extensive use of composite material technology. The author presents analytical techniques (closed-form and numerical) used to make structural design calculations in the DCA launcher. The evolution of the multiturn wound DCA armature design is discussed. In addition, measured plastic deformation of this armature after a high-energy experiment is compared to that predicted by finite element analysisItem Coilgun Technology at The Center for Electromechanics, The University of Texas at Austin(IEEE, 1993-01) Bresie, D.A.; Ingram, S.K.The engineering trade-offs performed on a coilgun design are described. The concept used was that of a collapsing field accelerator. This concept was chosen because of its passive operation, and because it lent itself to existing power supplies. The trade-offs described concern stress, maximum temperature rise in conductors, efficiency, time constants of the energy storage element, and weight. An example of such a trade-off concerns the mass of coilgun armatures. The more massive an armature, the greater its ability to absorb resistive losses and the higher its time constant. However, larger armature lower payload efficiency. Another trade-off concerns the fraction of armature weight that is devoted to structure. More highly stressed armatures have more attractive electrical performance at the expense of parasitic weightItem Composite Solid Armature Consolidation by Pulse Power Processing: A Novel Homopolar Generator Application in EML Technology(IEEE, 1989-01) Persad, C.; Peterson, D.R.; Zowarka, Jr, R.C.Graded electrical resistance and assured sliding contact are among the desirable characteristics for the solid armatures used in railguns attainable through the use of composite materials. Metal-metal, metal-ceramic, and metal-polymer composites are generic types of potential solid armature materials. The authors describe the production of these composites by a novel experimental approach that uses a homopolar generator in a pulse-powered materials consolidation system. The processing of copper-tungsten and aluminium-alumina composites is used to demonstrate versatility of the homopolar generator as a materials processing tool. Powder metallurgy and laminate bonding approaches have been utilized. Composite solid armature materials have been consolidated with subsecond high-temperature exposure. Densification in the solid state proceeds by a warm/hot forging mechanism, and fully dense composites are obtained by a combined application of pressure and a controlled energy inputItem Design and Testing of Large-Bore, Ultra-Stiff Railguns(IEEE, 1989-01) Price, J.H.; Fahrenthold, E.P.; Peterson, D.R.; Weldon, W.F.; Zowarka, R.C.; Fulcher, C.W.; Ingram, M.W.As part of an EM (electromagnetic) gun technology demonstration program, a systematic design approach targeted at identifying critical gun design constraints affecting hypervelocity projectile performance has been pursued. Results of the study led to a laboratory-based EM gun design that provides bore straightness and tolerances characteristic of light-gas guns, dynamic bore deformations comparable to those of conventional guns, the ability to change and test rail/sidewall insulator materials quickly, and superior in-bore performance diagnostics. A high-stiffness, easily maintained, precision-bore 9-MJ EM launcher has been designed and fabrication is virtually complete. A half-scale prototype of this hydraulically prestressed EM gun design has been fabricated and successfully tested. The authors discuss the railgun design approach and performance parameters, the analytical and empirical railgun structured simulation techniques used to validate the full scale gun design, and the fabrication status and initial performance test resultsItem Design and Testing of Solid Armatures for Large-Bore Railguns(IEEE, 1989-01) Price, J.H.; Fulcher, C.W.; Ingram, M.W.; Perkins, D.E.; Peterson, D.R.; Zowarka, Jr, R.C.; Pappas, J.A.A solid metal railgun armature called the Fishbone has been designed and tested at significant velocity, in both square- and round-bore configurations. The name `fishbone' describes a structure consisting of multiple, independent, compliant contacts. Primary measures of success are low muzzle voltage and post-shot bore integrity. Experiments at armature velocities in excess of 1.9 km/s have resulted in smooth muzzle voltage traces with peak values of 50 to 100 V and negligible bore damage. Design and performance issues important to the successful launch of a solid armature and the features of the Fishbone that address them are discussed. These issues include contact maintenance and gun stiffness, armature compliance, wear, thermal and structural integrity and materials selection. Shot data included are current, velocity, muzzle voltage, and post-mortem physical analysisItem Design of a Reluctance Accelerator(IEEE, 1991-01) Bresie, D. A.; Andrews, J. A.The design of a reluctance accelerator is described, and the methods used in its design are discussed. The methods of control of the accelerator and its predicted performance are also discussed. Because this device contains iron, and is therefore very nonlinear, it was necessary to use a finite element (FEA) code (TEXMAP) in order to determine the forces developed by the accelerator and to determine the inductance of the windings at various stroke positions. Results of the analysis show that the true performance of a reluctance launcher varies considerable from that predicted by classical closed-form flux analysis. It is shown that although the reluctance accelerator has some limitations in maximum force for a given bore area, predicted efficiency is relatively good when compared with air-core induction machinesItem Design of a Rising Frequency Generator/Coaxial Accelerator(IEEE, 1993-01) Weeks, D.A.; Pratap, S.B.The Center for Electromechanics at the University of Texas at Austin (CEM-UT), has designed a high efficiency, low mass and volume, matched rising frequency generator (RFG), and coaxial accelerator system to launch a 22-MJ projectile at 1000 m/s. The RFG produces variable frequency voltage by utilizing a novel variable frequency field excitation scheme. The matched system is designed to accelerate a 44-kg launch package to 1000 m/s in a 5-m-long, 15-stage accelerator, with an average-to-peak acceleration of 0.68 and armature mass-to-launch package mass ratio of 0.25. The RFG is designed for 40-GW peak power at 800 Hz and features a power gain of 26 (output power/field power)Item Design of a Self-Excited, Air-Core Compulsator for a Skid-Mounted, Repetitive Fire 9 MJ Railgun System(IEEE, 1989-01) Walls, W.A.; Spann, M.L.; Pratap, S.B.; Bresie, D.A.; Brinkman, W.G.; Kitzmiller, J.R.; Herbst, J.D.; Liu, H-P.; Manifold, S.M.; Rech, B.M.The design of a lightweight, compulsator-driven 9-MJ electromagnetic (EM) launcher has been completed and is in the fabrication phase. Scheduled for initial field testing in early 1989, the system will be capable of firing a salvo of nine rounds in three minutes at muzzle velocities between 2.5 and 4.0 km/s. Prime power for the compulsator is supplied by a 5000-hp gas turbine engine through a gearbox and clutch arrangement, and auxiliary power is provided by a small 750-hp turbine. Electrical power generation and pulse conditioning for the launcher are performed by the compulsator, which features a self-excited, air-core magnetic circuit and selectively passive armature compensation designed to minimize peak projectile acceleration. Peak power from the machine is 27 GW, and a total of 30 MJ is extracted from the rotor during each firing of the gun. System mass, including gun, compulsator, prime power, and auxiliary systems, is less than 22 tons and will be mounted on a 36-ton concrete slab which simulates the mass of an armored vehicle on which the system will eventually be integratedItem The Design of Homopolar Motor-Generators for Pulsed Power Applications(1975-11) Weldon, W.F.; Driga, M.D; Rylander, H.G; Woodson, H.H.The need for inexpensive pulsed power for fusion research is becoming more intense as the size of these experiments rapidly increases. Nearly all experimental investigations now proposed require energy stores of hundreds of megajoules and some proposed reactors are in the gigajoule range. An engineering feasibility study at the University of Texas at Austin in 1972 suggested the use of a Faraday disc or homopolar machine for inertial energy storage. Such a machine can use a single rotor as the motor and generator armature as well as the flywheel at a considerable cost saving relative to separate units. A number of machines using this principle have been designed by the Energy Storage Group at the University of Texas at Austin and two have been built and tested. Both the 0.5 megajoule and 5 megajoule homopolar machines, built at the University of Texas at Austin, have exceeded their original performance goals. Initially the main advantages of such homopolar machines appeared to be the geometric simplicity of the field coil windings, the use of a rotor without windings, and the resultant low cost. At present another advantage seems to overshadow these in that rotors without windings can be rapidly accelerated to high speeds and can be discharged rapidly with an electrical release of virtually all of the inertial energy in time periods down to milliseconds. Present design studies and experimental research are concentrating on producing low inductance, low resistance, high speed machines with short current diffusion times. Current collectors for use at high speed (up to 450 m/sec) are under experimental investigation in a separate brush test facility. These studies and tests are summarized in a form to facilitate determining the compatibility of homopolar machines and specific loads.Item Design of the Armature Windings of a Compensated Pulsed Alternator Engineering Prototype(1979-06) Gully, J.H.; Bird, W.L; Bullion, T.M; Rylander, H.G; Weldon, W.F; Woodson, H.H.The design of the armature winding& of a 6 kV, 70 kA compensated pulsed alternator engineering prototype now under construction at The Univeraity of Texas at Austin is presented. Electromagnetic forces acting on the windings and the resulting mechanical and electrical stresses placed on the armature insulation are given. Test results of a program to select the ground plane insulation system are described. Finally, fabrication methods, tooling, and problems encountered during construction are discussed.Item Electromagnetic Induction Launchers(IEEE, 1986-11) Driga, M. D.; Weldon, W. F.; Woodson, H. H.The electromagnetic launcher consists of a system of stator coils producing a traveling field which accelerates an armature carrying currents induced by the traveling field (induction accelerator [1,2]) or persistent currents supplied from otner sources (synchronous accelerator [2,10]). The fact that their armature has no electrical contact with the stator, essentially riding on the crest of a traveling magnetic wave, makes induction accelerators very attractive for a large number of applications. This paper is devoted exclusively to the accelerator of the induction type. Efficiency considerations require that the traveling wave should accelerate at approximately the same rate as the projectile. This can be achieved either using variable (increasing) winding pitch or a continuously increasing power supply frequency or a combination of both. A new dimension was added to the induction coaxial accelerator technology with the definition at the Center for Electromechanics at The University of Texas at Austin (CEM-UT) of a new electrical machine, the Rising Frequency Generator (RFG) representing a more attractive integrated power source for induction accelerators which had previously been forced to conform to constant frequency power supplies. This paper outlines the principles of design and shows two applications of induction coaxial launchers; a half-scale aircraft launcher in which the system also acts as an electromagnetic brake, stopping the shuttle and driving it in the opposite direction, and a high performance, 18-m long launcher capable of accelerating a 1-kg aluminum projectile to a velocity of 10 km/s at an average acceleration of 250,000 G.Item Experimental Results from CEM-UT's Single Shot 9 MJ Railgun(IEEE, 1991-01) Hayes, R.J.; Zowarka, Jr, R.C.A 10-m-long, 90-mm bore railgun has been designed and fabricated. During the test program, a number of solid armatures and projectile packages have been tested in a 50-m-deep vertical test range. The experiments are powered by six homopolar generator (HPG) charged inductive stores, sequentially staged to provide the desired acceleration profile. Prior to testing, computer simulations are run to determine the preferred current profile and predict system performance. During projectile flight, high-speed films, X-rays, muzzle volts, and velocity/acceleration profiles are recorded along with power supply operating parameters. Postshot diagnostics include bore wear analysis and armature and target recovery. Comparisons of predicted and recorded shot performance are also made. On selected tests, an energy balance is performed to determine efficiencies of the various components. A summary of all 90-mm gun shots is presented along the critical data collected from selected testsItem Induction Launcher Design Considerations(IEEE, 1989-01) Driga, M. D.; Weldon, W. F.Research, prompted by increased interest in induction accelerators for space and for military applications has shown that their advantages (contactless armature, high theoretical efficiency) with respect to their railgun counter parts are balanced by strong requirements on their power supply characteristics. In fact at each moment, the stator barrel, the projectile and the power supply mst form a carefully tuned system, capable of achieving a uniform and efficient electromechanical energy conversion with no contacts or feedback control.Item Large and Small Caliber Railgun Solid Armatures: Experimental Results(IEEE, 1991-01) Price, J. H.; Ingram, M. W. ISolid/transitioning armature performance results of two railgun programs is reported. Solid armature experiments continue for 15 and 90 mm bore guns. These armatures have been accelerated to over 2300 m/s. For the armatures tested, typical muzzle voltage measurements show the armature drop remains less than 50 V for velocities under 1000 to 1200 m/s; at velocities above 1000 m/s to 1200 m/s, the contact forms a hybrid armature. Armature performance data presented include muzzle voltage, gun current, armature resistance, total energy deposited in the armature, launch velocity, launch package muzzle kinetic energy, peak armature action, armature contact wear, and physical examination of recovered armatures. These data are separately summarized for each gun type and demonstrate armature survival at high current densities, bore pressures, and specific actionItem Limitations on the Minimum Charging Time for the Field Coil of Air Core Compensated Pulsed Alternators(IEEE, 1991-01) Pratap, S. B.;Air core compensated pulsed alternators (compulsators) are being developed for a variety of field-based applications in relation with electromagnetic launchers. Since these applications are essentially field portable, minimizing system mass is of great importance. It is also desirable to use a room temperature field coil, since carrying cryogens (such as liquid nitrogen or liquid helium) onboard a vehicle has logistic problems. These requirements have led to the use of a self-excitation scheme using a room temperature field coil. A discussion is presented of the eddy currents induced in the shield of the passive compulsator and the circulating current induced in the compensating winding of a selective passive compulsator during the charge-up of the field coil. It is shown that reducing the charging time of the field coil greatly enhances the efficiency. In some cases the rate of charging may be the determining factor on whether the field coil is room temperature or cryogenic and whether it needs active cooling. There is, however, an optimum charging rate. Increasing the charging rate beyond this limit does not result in proportional benefitsItem Limits to the Velocity of Solid Armatures in Railguns(IEEE, 1989-01) Long, G. C.; Weldon, W. F.Velocity limits of a solid armature in a railgun are the result of temperature and internal forces which surpass the yield strength of the material. A two-dimensional finite-element model for the magnetic and temperature fields in a railgun is presented for several rail and armatures designs. Copper rails and a molybdenum armature are identified as candidates for future solid armature testing. All simulations are performed for a 1/2-inch-square-bore railgun