14 research outputs found
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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
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Applications of Lightweight Composite Materials in Pulsed Rotating Electrical Generators
Center for Electromechanic
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Structural properties and testing of a composite banding used in high-speed rotors
The use of high-strength structural composite bandings is essential for high-speed rotors. In addition to bandings designed for maximum stiffness and strength, there is also a need for bandings that exhibit a controlled radial growth during operation. Controlling the radial growth rate of rotor bandings to match the growth of other rotor components maximizes the structural integrity of the rotor by minimizing reaction forces between parts during operation. This paper presents the structural material properties and strain-to-failure of a composite banding built with a nontraditional layup consisting of high-strength IM7 hoop filament windings and a combination of T700 tape laid at 0deg and plusmn45deg. The analysis and structural test results used to determine the strength of a composite banding with this layup is discussedCenter for Electromechanic
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Compulsator Rotordynamics and Suspension Design
High speed compulsator rotors utilizing high strength composite bandings pose unique problems from a rotor-dynamic standpoint. This article describes the basic design approach for rotordynamics used at The University of Texas at Austin Center for Electromechanics at (UT-CEM). As an example, the CCEML compulsator rotor-dynamic design is presented. The key considerations are seen to be: (1) mass and stiffness properties of the fully assembled rotor, (2) selection of rotor support bearings, (3) bearing supporting structure, (4) proper placement of rotor critical speeds, (5) adequate attenuation of rotor response at all speeds, and (6) bearing load capacity to react large discharge forces. Due to large mechanical and thermal shocks which occur during discharge, a primary design goal is to maximize tolerance to rotating imbalance. Another primary design goal is avoidance of destructive whirling instabilities which can occur with high speed rotors possessing large amounts of damping within the rotating assemblyCenter for Electromechanic
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Fabrication of a Rotor for a Field Based, Self-Excited Compulsator Power Supply for a 9 MJ Railgun Demonstrator
Fabrication of a high-speed, self-excited air-core rotor for a field based compulsator is well under way. The compulsator is to be used as a power supply for firing 9 MJ projectiles from a skid mounted electromagnetic launcher (railgun). The rotor flywheel is made of fiber reinforced epoxy composite and is supported with high-strength metal stub shafts which are shielded from the excitation field by water-cooled copper sleeves. The rotor features separate windings for self-excitation and railgun firing, and a two-pole configuration for pulse length considerations. The rotor is designed to store 210 MJ at 8600 r/min, with a rating of 3.2 MA peak current and 20 GW peak power into a 9 MJ railgun load. The concentric fiber-reinforced epoxy composite rings that make up the rotor flywheel are filament wound on steel mandrels, cured, and interference fit together. The main and excitation armatures and output conductors leading from the armatures to the shaft conductors are constructed of epoxy-impregnated aluminum and copper Litz wireCenter for Electromechanic
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Field coil insulation testing for pulsed power alternators
Current pulse power alternator designs operate at high speeds and high current densities. The field coil insulation systems for pulse power alternators must provide sufficient stand-off voltage while limiting the amount of thermal resistance for actively cooled designs, and also withstand the strain excursions experienced at full operating speed. Repetitive cycling of the strain excursion overtime may induce cracks in the surrounding field coil matrix. The primary insulation surrounding the field coil conductors must be able to stop crack propagation that may develop in the surrounding matrix material and provide voltage hold-off. Thermally conductive thermoplastics are currently being investigated for the field coil matrix materials where decreased thermal resistance is necessary for actively cooled field coil designs. In order to evaluate conductor insulation and thermoplastic matrix filler quickly, small coupon motorettes were developed per previous designs. The motorettes simulate the hoop strain the conductors would experience due to rotor growth at high rotational speeds. Once the motorettes had been mechanically loaded, the coupon was hi-potted to verify insulation integrity under strain. This paper will discuss the design and testing of these motorettes to evaluate thermally conductive thermoplastics as filler material for the field coil matrixCenter for Electromechanic
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End-of-Life Design for Composite Rotors [Flywheel Systems]
The University of Texas Center for Electromechanics (UT-GEM) is developing flywheel energy storage systems for combat and commercial vehicles and also leads the major US Flywheel Safety and Containment Program, a consortium effort of several leading flywheel developers. Safety for high performance composite flywheel systems on combat vehicles presents special challenges that impact the design of all flywheel components, especially the composite rotor and the bearings. This paper presents an overview of the issues and discuss design strategies and solutions applicable to the combat vehicle environment, using the flywheel energy storage system design recently completed under the Defense Advanced Research Projects Agency (DARPA) Combat Hybrid Power System (CHPS) Program as a case study. In particular, the paper will trace basic design and safety strategy, fatigue cycle development, lifetime design approach, and the resulting design marginsCenter for Electromechanic
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9 MJ/Pulse Air Core Compulsator
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.Center for Electromechanic
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Design, Fabrication, and Testing of 10 MJ Composite Flywheel Energy Storage Rotors
Flywheel energy storage systems employing high-speed composite flywheels and advanced electric motor/generators are being evaluated by the Department of Defense (DoD), NASA, and firms to replace electrochemical battery banks in satellites and manned space applications. Flywheel energy storage systems can provide extended operating life and significant reduction in weight and volume compared to conventional electrochemical systems. In addition, flywheels can provide momentum or reaction wheel functions for attitude control. This paper describes the design, fabrication, and spin testing of two 10 MJ composite flywheel energy storage rotors. To achieve the demonstrated energy density of greater than 310 kJ/kg in a volume of less than 0.05 m?, the rotors utilize flexible composite arbors to connect a composite rim to a metallic shaft, resulting in compact, lightweight, high energy density structures. The paper also describes the finite element stress and rotordynamics analyses, along with a description of the fabrication and assembly techniques used in the construction of the rotor. A description of the experimental setup and a discussion of spin testing of the rotors up to 45,000 rpm (965 m/s tip speed) are also presented. Accurate measurements of rotor centrifugal growth made with laser triangulation sensors confirmed predicted strains of greater than 1.2% in the composite rim. Due to the weight penalty associated with flywheel designs requiring containment structures, there is a strong need to develop flywheel systems which operate safely in space, preferably without dedicated containment structures. A future paper will describe results of a 28,600 rpm composite rotor burst test performed in a containment structure as a step towards understanding composite rotor failure modesCenter for Electromechanic
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Subscale Rotor Spin Testing for Compulsator Component Development
The maturation of pulsed rotating machines has evolved to the stage where a greater degree of basic research is required to further increase the energy and power density of advanced compulsators. The University of Texas at Austin Center for Electromechanics is studying the combined mechanical and electrical aspects of very high speed compulsator rotor designs for the next generation of compact pulsed rotating machines. This paper describes the design, construction and testing of three scaled composite rotors. Performance specifications included hoop stresses of 1.7 GPa (250 ksi) in the outer banding and strain excursions of 0.4% in the field coil region. Results from the three studies are reviewed in detail. Techniques developed at the Center for Electromechanics for determining composite rotor performance are also discussedCenter for Electromechanic