The University of Texas System

The United States of America As Represented by the United States

Herbert H Woodson

William F Weldon

John S Hsu

Glen C Long

Mircea D Driga

A method and apparatus for improving the performance of polyphase AC machines. The polyphase AC machines are excited both with a fundamental frequency and with an odd harmonic of the fundamental frequency. The fundamental flux wave and the harmonic flux wave will travel at synchronous speed in the air gap. This facilitates redistributing the flux densities in the machine and thereby increasing the total flux per pole in the machine.

Method and apparatus for improving performance of AC machines

An electromagnetic railgun having a layer of low conductivity material along the rails to interface with the armature as the armature is propelled along the rails. The low conductivity material has been found to permit rapid current penetration between the layer and armature, thereby inhibiting undersirable high current density formation along the trailing edge of the armature. Advantageously, inhibiting the high current density formation permits use of a solid armature at velocities exceeding on kilometer per second. Preferably, the layer is composed of graphite or a graphite/copper mixture. A layer of copper or other high conductivity material is preferably laminated to the low conductivity graphite layer to reduce the overall railgun circuit resistance. In the preferred embodiment, the layer of low conductivity material increases in thickness from the breech to the muzzle to decrease railgun circuit resistance.

Method and construction for control of current distribution in railgun

A method and apparatus for improving the performance of polyphase AC machines. The polyphase AC machines are excited both with a fundamental frequency and with an odd harmonic of the fundamental frequency. The odd harmonic flux wave is phase controlled so as to interact with otherwise waste harmonic flux waves generated by the rotor. The interaction of the harmonic flux waves enhances the pull-out torque, power factor, and efficiency of the polyphase AC machine.

A method and apparatus for improving the performance of polyphase AC machine is provided. The machines are excited with both a fundamental frequency and with an odd harmonic of the fundamental frequency so that a fundamental flux wave and an odd harmonic flux wave travel at a synchronized speed within the air-gap of the machine. The phase angle between the fundamental and odd harmonic excitation is controlled to increase the magnetic loading of one portion of the machine, while reducing the magnetic loading of the another portion of the machine. In this manner, redistribution of the flux densities is effected to more efficiently use the various components of the machine to increase torque.

An electromagnetic railgun having a layer of low conductivity material along the rails to interface with the armature as the armature is propelled along the rails. The low conductivity material has been found to permit rapid current penetration between the layer and armature, thereby inhibiting undesirable high current density formation along the trailing edge of the armature. Advantageously, inhibiting the high current density formation permits use of a solid armature at velocities exceeding one kilometer per second. Preferably, the layer is composed of graphite or a graphite/copper mixture. A layer of copper or other high conductivity material is preferably laminated to the low conductivity graphite layer to reduce the overall railgun circuit resistance. In the preferred embodiment, the layer of low conductivity material increases in thickness from the breech to the muzzle to decrease railgun circuit resistance.

A current limiting device for use with a circuit breaker in an electric power system utilizes mutual inductance variation between movable windings to limit current to safe levels. In the device, first and second coil windings are electrically connected for current flow therethrough and magnetically linked for mutual inductive coupling. The effective inductance of the connected coil windings is functionally related to the relative physical positioning of the coil windings. The coil windings are movable relative to one another, so as to provide for variation in the effective inductance of the two coils. Structure is provided for disposing the coils in an initial relative positioning, the structure being yieldable to a force produced between the coils due to a predetermined magnitude of current flow through the coils. The force produced between the coils acts to change the relative positioning of the coils, increasing the effective inductance, and thereby limiting the current therethrough. In an alternative arrangement, movement of the coils to designated positions of relative placement due to a predetermined magnitude of current flow therethrough may be utilized to open a set of electrical contacts or to trigger a conventional circuit breaker interrupting the circuit.

Current limiting device for overcurrent protection

This invention relates to an electromechanical energy converter with inertial energy storage. The device, a single phase, two or multi-pole alternator with stationary field coils, and a rotating armature is provided. The rotor itself may be of laminated steel for slower pulses or for faster pulses should be nonmagnetic and electrically nonconductive in order to allow rapid penetration of the field as the armature coil rotates. The armature coil comprises a plurality of power generating conductors mounted on the rotor. The alternator may also include a stationary or counterrotating compensating coil to increase the output voltage thereof and to reduce the internal impedance of the alternator at the moment of peak outout. As the machine voltage rises sinusoidally, an external trigger switch is adapted to be closed at the appropriate time to create the desired output current from said alternator to an external load circuit, and as the output current passes through zero a self-commutating effect is provided to allow the switch to disconnect the generator from the external circuit.

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Austin, TX, United States of America

Herbert H Woodson