Abstract--Performance testing of the model-scale CPA was recently completed at the University of Texas Center for Electromechanics. A major part of the project was the development of design and simulation codes that would accurately represent the performance of pulsed alternators. This paper discusses the components of the system and its operational sequence. Details of the performance simulation model are presented along with test data. The test result is compared to the predicted data.

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Flywheel energy storage systems employing high speed composite flywheels and advanced electric motor/generators are being evaluated by the Department of Defense (DoD), NASA [1], and firms [2,3] 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 3 , 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 modes.

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Fabrication of a high-speed, self-excited air-core rotor for a field based compulsator has begun and 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 qre shielded from the excitation field by water cooled copper sleeves. The rotor features separate windings for selfexcitation and railgun firing, and a two-pole configuration for pulse length considerations. The rotor is designed to store 210 MJ at 8,600 rpm, 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 wire. The rotor is approximately 75% assembled; the metal shafts, the excitation winding with its output conductors completed, and several flywheel rings assembled. The main armature has been preformed on a mandrel and is ready for assembly onto the rotor.A detailed description of the compulsator rotor with design considerations and fabrication techniques are reviewed in this paper, and the current status of the project is discussed. The compulsator stator is being constructed in parallel with the rotor and is discussed in a companion paper presented at the 6th EML conference [l]. ELECTRICAL DESIGN AND PERFORMANCECompulsators are excellent power supplies for railguns because power system functions of energy storage, electrical pulse generation, and pulse preconditioning prior to delivery to the gun are combined in a single device [2,31. This results in a high efficiency system that is able to recover the inductive energy in the gun before the projectile exits the muzzle. Furthermore, burst firing is possible because sufficient energy can be stored in the rotor for multiple shots, allowing prime power to be averaged over several shots and substantially reducing system peak power requirements. Other important advantages of compulsators include a naturally occurring current zero at projectile exit, pulse shaping capability, and high energy and power densities The work was supported by U.S. Army ARDEC, contract no. DAAA21-86-C-0215.relative to other power supply options. For this particular mission a two-pole, self-excited air-core machine was selected based on weight and size constraints. Also, to accommodate relatively low projectile acceleration limits a selectively-passive compensation scheme [4,5] is incorporated in the design which results in a flat current wave form ( fig. 1) from the compulsator into a railgun load. The selectively-passive compensation scheme results in a peak projectile acceleration of 980,000 m/s2 (100 kgees). A crosssection of the rotor is shown in fig. 2 and...