Other

Massachusetts Institute of Technology

Carrier Corporation

Gerald L Wilson

David M Otten

James L Kirtley, Jr

David C Jolly

Tsen-Chung Cheng

A method and apparatus for reforming, by either radially expanding or reducing an electrically conductive tubular workpiece (11). The method of the expansion embodiment comprises the steps of inserting an insulated electrical conductor (21) into the tube; then making up an electrical circuit that includes the portion of the wall of the tube in series or parallel connection with the electrical conductor and a source of electrical power (C and SW), then applying a voltage across the circuit. The current flowing through the conductor and the tube produces a circumferential electromagnetic field between the conductor and the tube. The current in the tube, interacting with the magnetic field, produces a radially directed outward force on the tube. If the force is sufficiently great and of a duration longer than the time required for a sound wave to pass through the tube wall, the tube wall will radially expand and be permanently deformed. The method of the reduction embodiment comprises the additional step of inserting the workpiece in an electrically conductive sleeve (51) and the making up step comprises including the sleeve in the electrical circuit and arranging the workpiece and the conductor in parallel circuit relationship. The respective apparatus of the two embodiments implement the method of the invention. The expansion embodiment of the invention is particularly adapted to the expansion of tubes in plate fin and tube type heat exchangers.

Method and apparatus for reforming a tube

A dc ground fault detector in which ground fault is sensed by noting an imbalance of magnetic flux due to a pair of windings on a toroidal core.

DC Ground fault detector wherein fault is sensed by noting imbalance of

A power angle relay to measure the power angle of a synchronous alternator. The power angle relay receives a reference voltage signal corresponding to a fixed point on a reference voltage waveform (usually a zero crossing) from some point in the power system to which the alternator is normally synchronized and an electric signal representative of the angular position of the shaft of the synchronous alternator and is operable to combine the two to provide an indication representative of the power angle between the direct axis of the synchronous alternator and said fixed point.

Power angle relay to measure and respond to the power angle of a

An electrical insulator composed of one or more electrical insulating skirts or sheds or shells at least some of which skirts or sheds or shells have a plurality of discrete conductive regions at one surface thereof, the discrete conductive regions being appropriately arranged and sufficient in number to intercept an arc in the event of incipient flashover from proceeding radially past the discrete conductive regions, thereby to prevent said flashover.

High-voltage electrical insulator adapted to prevent flashover

A superconducting machine wherein the field winding and associated elements in the cold region of the machine are protected against transients by a flexible, electrically conductive outer shield means that interacts with an inner conductive shell in a way that causes the magnetic field to be compressed between the shield and the shell, thereby to transmit mechanical radial forces between the two.

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Wayland, MA, United States of America

Gerald L Wilson