Dennis Pavlik

Direct and Quadrature Models for High Energy Pulsed Alternators

Rotating machinery can be used to store kinetic energy and convert it to high current electrical energy in the millisecond time frame required by pulsed loads such as electromagnetic launchers. Machines used in these applications, called pulsed alternators, often require nonstandard features, such as low impedance, more than three phases, or compensating windings inside or conductive shields outside the machine. Design and analysis of systems utilizing pulsed alternators require accurate transient modeling. We present a direct and quadrature (DQ) representation of the system dynamics for nonstandard electric machines used in pulsed power applications, which can be used to construct efficient simulation models. Simulation results using the resulting model are presented and compared to an existing model, which has been validated with test data.

A series wound air core homopolar generator: SWAC for tactical armor applications

The results of a study on generator design for a pulsed electromagnetic (EM) railgun launcher for a 10-shot low-repetition-rate mobile tactical system are presented. A novel design for a series-wound air-core (SWAC) homopolar generator is discussed. A number approaches to the problems associated with multiple-shot operation and high power density are presented. Specifically, designs for a spiral coil group, segmented current collection, active cooling and optimized rotor kinetic energy are addressed. The most significant features of the design are conventional water cooling, low rotational stored energy, and demonstrated materials and fabrication techniques. The resulting power supply consists of two counterrotating SWAC machines with a net energy density of 10 kJ/kg, 60-MJ total stored energy per shot, 2.50 mA peak current at 320 V, and significantly reduced eddy current losses. >

Balancing the current distribution in the current collectors of homopolar machines using induced voltage gradients

This paper presents the results of a study conducted at the Westinghouse Electric Corporation Research Center for minimizing the current imbalance in sliding contact current collector assemblies. The results suggest that the conventional approach to achieving current balance in these assemblies provides a less than optimal distribution and that significant improvements can be made. The optimum situation for minimizing current imbalance is not necessarily one where a constant potential is maintained along the current collector, but one where a voltage gradient is induced from inboard to outboard end of the collector. Described is a calculation procedure for determining the optimum voltage profile within the collector as well as the leakage field needed to induce this required voltage gradient.