The Center for Electromechanics a t the The University of Texas at Austin (CEM-UT) has completed final assembly and is currently testing a laboratory based, small caliber, electromagnetic launcher and compensated pulsed alternator power supply. The objective of the program is to develop a compact, lightweight test bed capable of accelerating a salvo of three, 32-g masses to 2 km/s at a rate of 10 Hz. The 0.60 caliber, augmented railgun is powered by an 850 kg selfexcited, air-core compulsator which develops 674 MW peak power delivered through a solid state, silicon controlled rectifier closing switch. The incremental test plan is scheduled to bring the system to full power levels during the summer of 1992. This paper presents critical component fabrication and assembly details of the compulsator and supporting subsystems Early system commissioning and test data is presented including low speed (8,000 rpm) tests of the compulsator involving external excltation of the field coil.
One of the more promising electric gun system configurations utilizes a capacitor based pulse forming network to power the launcher, a limited duty, high power alternator to charge the capacitors and a composite flywheel for energy storage. This configuration combines the flexibility of a pulse forming network (PFN) with the high average power of an alternator and the high energy density of a flywheel. The alternator can be designed to directly charge the capacitors without the invertedtransformer typical of battery charged Capacitor systems. Optimization will require trade-offs between energy density, voltage and efficiency. System integration is facilitated by direct coupling of the flywheel/alternator to a turbine or motor and modularity of the components. This paper presents the conceptual design of a system to power an 18 shot, salvo fire 30"railgun. The performance of components was selected to be slightly beyond the state of the art but achievable in the near term. For instance, the baseline PFN utilizes a 935 kJ capacitor bank made up of Aerovox 1.3 Jlg, 2.5 A/J, 80% efficient capacitor technology. It was sized assuming a 33% efficiency from capacitor to launch package. These capacitors would require some development and are based on the 1.5 J/g technology developed under the BTI/Army Pulse Power Module program. The 1.5 J/g technology is based upon high voltage (24 kV), low currenf capacitors. 1.3 J/g is estimated for lower voltage (8 kV) higher current devices. The alternator has a power density of about 12 kWkg. This power density is beyond the state of the art (= 9 kW/kg) [l] but is considered reasonable because the system does not require continuous power providing opportunities between charging cycles for cooling. Compulsators have demonstrated peak powers of 100 kWkg [2] and are being designed to produce 500 kWkg [3]. The energy storage flywheel design is based on the mlnimization of overall system mass. It is mounted integrally wlth the alternator rotor and is enclosed in a containment vessel. Consideration of both the flywheel and containment yields a specific geometry that has minimum mass.
In this paper a method is described that takes the nonlinear dynamic stiffness and damping coefficients for multiple hydrostatic bearings and incorporates them into a rotordynamic FEM model for a rotating machine. A Newton-Raphson iteration scheme is presented that uses updated bearing coefficients at every iteration to the solution. A non-linear computer program was written using the method described which models transient and synchronous response and calculates damped eigenvalues.
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