An Application Guide for Compulsators

Focus toward advanced mobile tactical configurations for railgun power supplies has resulted in the evolution of five compulsator generations in the past 15 years. Unfortunately, the rapid maturation of the technology has tended to dilute the relative importance and application base of previous generations. Technical variance between generations has been significant, including air-core or iron-core, rotating armature or field, single- or multiphase, solid rotor or shell, and externally excited or self-excited. It is useful, therefore, to review and classify the important distinctions between the generations of machines, thus allowing proper selection of the one best suited for a given application. This paper provides an overview of the evolution of compulsators developed at The University of Texas at Austin Center for Electromechanics. Features of past and present configurations are discussed, such as machine topology, method of excitation, basic switching methods, discharge pulse shapes, and potential energy and power densities. A list of potential applications is generated for all disciplines within the armed forces. This information is used to create an application guide that can be used to select appropriate compulsator options for the mission given. An extensive list of references is also provided.Center for Electromechanic

Brush/Slip Ring Current Collector Performance and Anomalies During Compulsator Commissioning

During recent tests associated with a model scale compulsator development program at The University of Texas at Austin Center for Electromechanics (UT-CEM), the performance of severe duty trailing arm brush current collectors was evaluated. The original material of choice for the brush slip ring design was 70075-T6 aluminum to minimize machine mass and simplify slip ring assembly on the rotor shaft. The slip rings have a nominal diameter of 5.5 in. The combination of CM1S copper, trailing arm brushes, and aluminum slip rings performed well up to about 80% full speed, although the design did not appear to be very damage tolerant. As testing continued at higher speeds, one of the slip rings began to exhibit small shallow arc pits in the brush track on the slip ring outer diameter. This was observed on only one slip ring and had no apparent affect on machine performance. Left unchecked, this shallow arc damage can cause a high speed brush to “bounce” excessively during a run and cause more severe damage, as well as increase the circuit impedance from the arcing. This paper presents a general description of the observed brush performance during normal and fault conditions. It also includes a description of mechanical analysis and field strength measurements done around the brushes in an effort to explain the “one brush” bouncing. Brush and slip ring design upgrades (including a reinforced brush actuator for increased brush down-force and a newly implemented two-layer aluminum and steel slip ring design) are discussedCenter for Electromechanic

Rotating Machine Development at The University of Texas

The Center for Electromechanics at The University of Texas at Austin (CEM-UT) is specialized in the development of high power, pulsed rotating machines for a variety of applications including fusion experiments, directed energy devices, and electrothermal and electromagnetic accelerators. For many of these applications, compulsators have emerged as viable power supplies. These machines are low impedance alternators which use flux compression to shape the discharge pulse and increase peak power and, to date, have been constructed from ferromagnetic materials. In the past several years, tremendous gains in energy and power densities have been predicted based on the use of composite materials. Glass, graphite, boron and Kevlar reinforced epoxy systems have the advantage of superior strength and stiffness, and are much lighter when compared to their metal counterparts. Two major efforts in which composite based (air-core) compulsators are being developed are now coming to fruition. Additionally, conceptual designs of several advanced concepts covering a wide range of pulse lengths and applications have been performed. The purpose of this paper is to report on the status of the machines currently being fabricated and describe the next generation of high performance compulsators.Center for Electromechanic

Single and Multiphase Compulsator System Architectures: A Practical Comparison

The Center for Electromechanics at the University of Texas at Austin (UT-CEM) has designed, built, and tested three generations of iron-core and air-core compensated pulsed alternators (CPA). These include the iron core, small caliber, cannon caliber, and model scale compulsators. Early CPA were single-phase machines that were optimized for a specific load and desired performance. The most recent machine, the model-scale CPA, is a multiphase alternator coupled to the load through a rectifier. This paper includes a discussion of the requirements and capabilities of both single-phase and multiphase systems, a point design for each system type, and a comparison of system performance in driving a cannon caliber launcherCenter for Electromechanic

Single Shot Switch Performance on the Cannon Caliber Electromagnetic Gun Program

Analyzer (DMA) tests. Also documented in this paper will be the results from specialized viscoelasticity tests performed on representative composite windings to determine preload loss versus time, temperature, and stress. Also, in collaboration with the Army Research Laboratory, a nested cylinder code is being developed to predict viscoelasticity induced preload losses.Center for Electromechanic

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

Compulsator Rotor Assembly Methods

High energy density requirements for fieldable electric gun applications have led to the development of air-core compulsators which utilize hybrid metal/composite rotor designs. In addition to supporting the required generator windings, these rotors also must store large amounts of kinetic energy. To satisfy energy density requirements, the tip speeds of the electric gun class compulsator rotor are appreciable with typical values exceeding 500 m/s for near term designs. High performance composites are utilized in the rotor structures and large amounts of radial pre-load is required to hold the rotor structure and electrical windings together at the tip speeds required.Center for Electromechanic

Operating Modes for Compulsator Based Electromagnetic Launcher Systems

The compensated pulsed alternator (compulsator) is a versatile power supply capable of interfacing with the electromagnetic launcher in various ways. The method that has been explored at length with several systems is the single phase option. Several variants of this option, some using advanced pulse shaping techniques, have been discussed in prior publications [I-3]. Besides this basic single pulse method of operating there are several other methods each with its pros and cons. The multi-phase option is discussed in this paper. Within the broad class of multi-phase systems there are further sub-classes, namely alternating current drive and unidirectional current drives. Thus the branching of these operating modes gives rise to a variety of operating modes. Each one of these operating modes is described and simulation results are presented.Center for Electromechanic

Malaria vectors in the Brazilian Amazon: Anopheles of the subgenus Nyssorhynchus

Various species of Anopheles (Nyssorhynchus) were studied in the Amazon with the objective of determining their importance as malaria vectors. Of the 33 known Anopheles species occurring in the Amazon, only 9 were found to be infected with Plasmodium. The different species of this subgenus varied both in diversity and density in the collection areas. The populations showed a tendency towards lower density and diversity in virgin forest than in areas modified by human intervention. The principal vector, An. darlingi, is anthropophilic with a continuous activity cycle lasting the entire night but peaking at sunset and sunrise. These species (Nyssorhynchus) are peridomiciliary, entering houses to feed on blood and immediately leaving to settle on nearby vegetation. Anopheles nuneztovari proved to be zoophilic, crepuscular and peridomiciliary. These habits may change depending on a series of external factors, especially those related to human activity. There is a possibility that sibling species exist in the study area and they are being studied with reference to An. darlingi. An. albitarsis and An. nuneztovari. The present results do not suggest the existence of subpopulations of An. darlingi in the Brazilian Amazon

Genetic divergence in mitochondrial DNA of Anopheles nuneztovari (Diptera: Culicidae) from Brazil and Colombia

In the present study, we have examined the variability in Anopheles nuneztovari mitochondrial DNA of three populations from the Brazilian Amazon and one from western Colombia (Sitronela), using four restriction endonucleases (BclI, ClaI, HindIII, SstI). The haplotype diversity (h) was slightly elevated in all populations (0.5000 to 0.6765), whereas the nucleotide diversity (π) was lower in the Sitronela population (0.0029) and higher in populations from the Brazilian Amazon (0.0056 to 0.0098). The degree of sequence divergence (δ) estimated within the Brazilian Amazon and that in Sitronela (0.0329 to 0.0371) suggests that these geographic populations of A. nuneztovari may eventually constitute separate species. The low sequence divergence values among the three Brazilian Amazon populations (0.0012 to 0.0031) indicate that these populations are genetically similar. These results are consistent with those recently reported for allozymes of these same populations