CEM Conference Proceedings

Permanent URI for this collectionhttps://hdl.handle.net/2152/29971

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A 10-MJ Active Rotary Flux Compressor for Driving Xenon Flashlamps
(1983-04) Morgan, C.A.; Bird, W.L; Weldon, W.F.
A 2 MW Flywheel for Hybrid Locomotive Power
(2003-10) Thelen, R.F.; Herbst, J.D; Caprio, M.D.
The University of Texas at Austin Center for Electromechanics (UT-CEM) is currently developing an Advanced Locomotive Propulsion System (ALPS) as part of the Next Generation High-Speed Rail program sponsored by the Federal Railroad Administration (FRA). The ALPS consists of a gas turbine and synchronous alternator, combined with an induction motor coupled flywheel energy storage system (FESS). The prime power and FESS are coupled through a DC power link, as is the conventional AC traction drive system. The energy system includes auxiliary support systems to provide thermal management, bearing systems, controls, and power conversions. The energy exchange capacity of the flywheel is 360 MJ (100 kWhr). This paper presents the requirements, considerations, and design of the integrated turbine and flywheel power system. Significant development efforts have gone into the high-speed synchronous alternator, the flywheel power converter, the highspeed induction machine for the flywheel, the flywheel itself and its magnetic bearings. The fabrication status of these components and testing progress is also reported.
A 2-MW Motor and ARCP Drive for High-Speed Flywheel
(IEEE, 2007-02) Thelen, R.F.; Gattozzi, A.L; Wardell, D; Williams, A.S.
A high-speed induction motor and soft-switching electronic drive are selected to transfer energy between a flywheel and the other power components of prototype hybrid locomotive power system. The motor-generator operates in direct coupling at 14,000 rpm (233 Hz) with the composite flywheel. The motor drive rating is 2 MW (2600 hp) over the operating frequency range of 125 to 250 Hz. The power-frequency range and harmonic heating considerations have lead to a auxiliary resonant commutation pole (ARCP) soft-switching design. The drive and motor have been tested over the full speed range. Unique requirements of energy storage and transfer are also presented.
25 GW Homopolar Generator Experiment
(IEEE, 1991-06) Zowarka, R.C.; Kajs, J.P.
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.
9 MJ/Pulse Air Core Compulsator
(1987-06) Pratap, S.B.; Manifold, S.M; Walls, W.A; Spann, M.L; Weldon, W.F.
One of the most critical issues in taking electromagnetic gun technology from the laboratory to field applications is the compactness and portability of very high energy, pulsed power supplies. The air core compulsator which is under development at CEM-UT addresses these requirements. The rotor of this machine is made from fiber reinforced epoxy composites and spins at a tip speed of 500 m/s which is substantially higher than is possible with a ferromagnetic rotor. The higher tip speed greatly increases the energy density of the rotor thus reducing the size of the prime power source. The special structural features of this machine, the electrical design, and the cooling system design are discussed.
Active suspension technology development for high performance off-road vehicles
(2001-09) Beno, J.H.; Weeks, D.A.
An initial laboratory proof-of-principle demonstration project, two critical technology development projects, and vehicle demonstration projects were conducted at The University of Texas at Austin Center for Electromechanics on a HMMWV and a transit bus. This document describes the technology developments and HMMWV demonstration project.
Adaptive Mesh Refinements in Magnetic Field Calculation
(1976-06) Pillsbury, R.D.; Becker, E.B.
A method for determining regions of a finite element method to be refined is presented. The calculation of the residual in the governing differential equation for each element is used as a criterion. Numerical examples are given.
Advances in homopolar welding of API linepipe for deepwater applications
(1997-10) Carnes, R.W.; Hudson, R.C; Nichols, S.P.
The University of Texas at Austin Center for Electromechanics is conducting a research program to study homopolar welding of line pipe for J-Lay applications. In 1995, the third year of the five year research program, process improvements increased Charpy V-Notch impact toughness properties to near parent metal values, while maintaining acceptable strength. After demonstrating repeatable performance, research focused on real world effects including evaluating the effect of poor fit up resulting from misalignment and rough and wavy interfaces. During the final year of the research program, the pipe welding program has scaled up to 12-inch nominal line pipe, a sevenfold increase in cross-sectional area. The paper will cover basics of homopolar welding, mechanical properties, weld upset profile, HPW metallurgy, and the studies of real world effects. Results from homopolar welding of 12-inch pipe will also be presented.
Air Core Compensated Pulsed Alternators
(IEEE, 1989-06) Pratap, S. B.; Spann, M. L; Walls, W. A; Driga, M. D.
A compensated pulsed alternator is a generator capable of delivering high power energy pulses with current waveform flexibility. This versatile machine has applications in various fields where power density is at a premium. Recent advances in applying fiberIepoxy composites to rotating electrical machinery (1) have greatly enhanced the power density capabilities of this machine. A characteristic of these new machines is an absence of ferromagnetic material in the magnetic circuit, and they are therefore referred to as >air-core> compulsators. This paper discusses the topological considerations and the capabilities of the family of machines called the air-core compulsators.
Air-Core Compensated Pulsed Alternators
(IEEE, 1989-06) Pratap, S.B.; Spann, M.L; Walls, W.A; Driga, M.D.
A compensated pulsed alternator is a generator capable of delivering high power energy pulses with current waveform flexibility. This versatile machine has applications in various fields where power density is at a premium. Recent advances in applying fiber/epoxy composites to rotating electrical machinery [l] have greatly enhanced the power density capabilities of this machine. A characteristic of these new machines is an absence of ferromagnetic material in the magnetic circuit, and they are therefore referred to as >air-core'' compulsators. This paper discusses the topological considerations and the capabilities of the family of machines called the air-core compulsators.
An alternative architecture and control strategy for hexapod positioning systems to simplify structural design and improve accuracy
(2010-07) Beno, J.H.; Booth, J.A; Mock, J.
Hexapod systems (6 legged Stewart Platforms), offer advantages in accuracy over other positioning systems and are finding applications in numerous telescopes. However, instruments with increased sophistication for modern telescopes continue to grow in size and required positioning accuracy. This paper details an alternative hexapod configuration and design approach, particularly focused on relatively large, high precision hexapod systems supporting high mass payloads. The new configuration improves accuracy, reduces actuator mass, simplifies design, and reduces system cost but requires modest additional control algorithm sophistication.
Alternator Power Conditioning for Launchers
(1998-06) Singh, H.; Eccleshall, D.; McNab, I.; Pappas, J.
A high-energy pulse-discharge is needed to drive an electromagnetic (EM) or an electro-thermal-chemical (ETC) launcher. Various pulse power generators have been examined and used. Capacitor-based power supplies are convenient for laboratory launchers, but supplies based on rotating machines-alternators and homopolar generators-are generally more weight efficient and practical for storing, generating and shaping pulses for multi-shot, fieldable launchers. Alternators are the most flexible of the rotating machines, are better matched to the variable impedance of the launcher, and avoid the use of opening switches which are difficult to implement for repetitive and reliable operation. Also, a single pulse generator can be used to power several lethality and survivability platforms. Several alternator configurations are possible, each involving different pole geometries, numbers of poles and output phases. These configurations are in turn associated with a power converter system. The switch requirements can be met for small-caliber EM railguns and for ETC guns of all caliber by near-term silicon thyristors. For large caliber EM railguns, triggered vacuum switches are viable, although they may have to be augmented with diodes or other devices to ensure their recovery after each cycle. In the long term, thyristors based on silicon carbide offer the most promise for all applications because they can operate at 3 to 5 times the current density and electric field intensity of silicon devices.
Analysis of Fault Events in MVDC Architecture
(IEEE, 2009-04) Ouroua, A.; Beno, J.H; Hebner, R.E.
Effective interruption of load currents under both normal and fault conditions presents major challenges in medium-voltage DC distribution systems. In a highly-integrated DC power system, the preponderance of power converters connecting several loads with power ranging from (W) to (MW) levels rises additional concerns about the effects of a DC fault on other loads connected to the same bus or adjacent buses. Equally critical are the interactions between these power converters during the fault isolation and clearance process. In order to address some of these issues a basic but relevant model has been constructed to study the behavior and effects of DC faults in an MVDC power system for an all-electric ship. Results of the analysis are presented.
Analysis of Performance of Rail Gun Accelerators Powered by Distributed Energy Stores
(1980-06) Marshall, R.A.; Weldon, W.F.
It has been established that centimeter sized projectiles weighing several grams can be accelerated by electrical forces to velocities in excess of five kilometers per second in a classical railgun. The technologies required to do this are adequately understood, at least in the case where a single energy store is connected to the breech end of the gun. There are two disadvantages to using a single energy store. It is generally desirable to keep gun current as nearly constant as possible and this is difficult to achieve with a single store without making the store excessively large. Rail resistance also becomes a dominating factor as higher velocities are reached because higher velocities require greater gun lengths and correspondingly larger gun resistances. One way to by-pass these limitations is to distribute energy stores along the length of the gun. Not only does this reduce the average rail resistance by reducing the length of rail that carries current at anytime, but it permits inductive energy to be usefully transferred down the gun rather than allowing it to dissipate resistively in the rails. This paper shows how the performance of such a gun may be simulated, by computing the instantaneous rate of change of current in each energy store and by using these values to obtain projectile acceleration. Two specific rail gun systems are examined, the first being a >scientific railgun> designed to propel a three gram projectile to a speed of 20 kilometers per second, and the second being a >space-launch railgun> to accelerate one metric ton to 7.5 kilometers per second.
Analysis of the Power Quality Impact of Multiple Directed Energy Loads on an Electric Ship Power System
(2010-06) Hebner, R. E.; Gattozzi, A. L; Cohn, K. R; Colson, W. B.
The electrical power system of an all-electric ship has been modeled in Simulink for the case of a ship supporting several high power directed energy loads, among which are a Free Electron Laser (FEL), an Active Denial System (ADS), and a Laser Weapon System (LaWS). Starting from a load centered approach, and a physical description of the components of the various loads, individual models of each load plus a combined model for a system supporting simultaneously one instance of all loads have been developed. Sample case studies are presented corresponding to expected operational scenarios for a US Navy ship and to potential emergency conditions. The models have been designed to be interactive, allowing the operator to change key settings dynamically while the simulation is running, thus mimicking an actual operation of the power system on a ship in real time. A preliminary graphical user interface has also been developed to demonstrate the ability of these models to be converted into top-level training tools for Navy personnel supported by a realistic representation of the ship power system.
Analytical Description of the Commutation Process in an Auxiliary Resonant Commutated Pole (ARCP) Inverter
(2006-08) Gattozzi, A.L.; Williams, A.S.
Application of a Friction Model to Electromagnetic Launchers
(1986-09) Zowarka, R.C.; Weldon, W.F.
Application of Homopolar Pulsed Power to Metals Joining
(1983-04) Aanstoos, T.A.; Keith, R.E; Weldon, W.F.
Homopolar generators (HPGs) presently being developed at the Center for Electromechanics are capable of delivering megampere pulses of electric current in a controllable manner. One application for these machines is as the power supplies for an industrial welding process. During the past five years, several research projects have been carried out to explore the welding capabilities of HPGs. Among the materials that have been welded are carbon and low alloy steels, several varieties of stainless steels, tool steels, nickel-base and molybdenum-base alloys, aluminum, and several dissimilar-metal couples. Among the shapes that have been welded are bars, sheets, plates, tubes, pipe, angle sections, and rails. The largest cross sections that have been welded to date are 9 in. 2 (2.9 tm2), and the smallest have been less than 0.3 in. (0.58 cm). Welding is accomplished in times approximating a second. Unique advantages of the homopolar pulse welding process are that it can be scaled upward to indefinitely large cross sections and that it does not impose a sudden load on the mains.
Application of Pulse Power Technology to Induction Accelerators
(IEEE, 1991-06) Bresie, D.A.
Induction accelerators have potential as drivers for a variety of applications, from tactical weapons to earth-orbit launchers. This paper describes how pulsepower techniques have been used on several projects at the Center for Electromechanics at The University of Texas in Austin (CEM-UT) to advance induction accelerator state of the art. Use of capacitor energy discharge and power switching are two pulse-power methods described. Also described are fiber optic sensor control and digital feedback.
Application of Rotating Electrical Machinery for Charging Capacitive Loads
(1983-04) Bird, W.L.; Brown, D.R; Pratap, S.B; Weldon, W.F.

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