Abstract: Transformers (14) inject test voltage signals of know frequency to each phase of the load side of an electrical distribution circuit (15). Processor (32) waits for a delay period to allow transient effects of the injected signals to settle, and then accepts the sampled test current signals provided by current transformers (12) through conditioning circuit (16). This process is repeated by injecting test voltages at different frequencies, which are selected by processor (32) based on stored instructions. Processor (32) uses the sampled signals to determine a representative current for the load side of the distribution circuit (15) and then compares the representative current with a predetermined current threshold value stored in non-volatile memory (40). If the current is above this threshold, processor (32) provides a lockout signal to the fault lockout device (48) and fault lockout flag (50).

Abstract: A sensor for a power distribution system includes: a conductor; a core proximate the conductor; and a reed switch adjacent the core, the reed switch in electrical communication with an electronic trip unit. A power distribution system includes: an upstream circuit breaker including an electronic trip unit; a downstream circuit breaker in electrical communication with the upstream circuit breaker; a first sensor positioned downstream from the downstream circuit breaker, the first sensor includes: a conductor in electrical communication with the downstream circuit breaker; a core located proximate the conductor; and a reed switch adjacent the core, the reed switch in electrical communication with the electronic trip unit.

Abstract: A current limiting device for protecting electrical circuits has a case and a pair of separable electrodes disposed within the case. Each electrode has a plurality of openings with an ablative member abutting the openings at an outer surface of the electrode. A spring is disposed between each ablative member and the case for urging the electrodes together. When the electrical current exceeds a predetermined setpoint the electrodes separate and an arc is created between the electrodes. The arc heats the ablative member causing expulsion of gasses which further increase the gap resistance and cool the arc to thereby quenching the arc. In a second embodiment of the current limiting device, one of the electrodes is a fixed electrode. The ablative member is disposed about a surface of the moveable electrode with a plurality of legs passing through a plurality of openings of the moveable electrode and in contact with an inner surface of the fixed electrode.

Abstract: An alternating current circuit breaker having an extended fin cantilevered from its housing. A portion of the fin along its extended length is magnetized so that the fin flutters in the magnetic field generated by the alternating current conducted through the breaker. The resulting magnetic resonance vibration establishes forced, convective heat transfer which assists cooling of the breaker.

Abstract: An electric arc extinguishing mechanism is provided for an electric current switching apparatus of the type having a pair of contacts which selectively engage to complete an electric circuit. The mechanism includes a plurality of splitter plates located adjacent to the contacts and formed of electrically conductive material. Each splitter plate has a body of electrically conductive material, and a casing with a pair of planar portions on opposite sides of the body and connected by the curved edge portion. The edge portion is adjacent the contacts with the planar portions extending from the edge portion in an open loop having a gap. Any arc introduced between adjacent splitter plates moves around the open loop before being extinguished thereby not residing in one spot long enough to cause gross melting and associated erosion of the splitter plate.

Abstract: A thick solid steel slot motor is disposed adjacent a movable conductor to apply a contact closing force on the conductor, augmenting the contact pressure spring, under steady state current conditions, and to reduce the force under high rate of current rise conditions to enhance dynamic separation of the movable conductor from a stationary conductor, reducing the strength requirement of the contact pressure spring.

Abstract: A solenoid trip unit is electrically connected in parallel with a current limiting polymer element in series with circuit breaker contacts to function as a shunt resistance for the polymer element, becoming energized by transition of the polymer element to its high resistive state, for tripping the breaker contacts open upon such transition. The solenoid may be particularly wound with a resistive wire.

Abstract: A linear motor of the type used to control the radial position of a write/read transducer relative to a rotating data storage disk comprises an elongated tubular-shaped permanent magnet which concentrically surrounds and is spaced, by an air gap, from an elongated pole piece of highly permeable material (e.g. steel). A selectively energizable coil, concentrically arranged between the magnet and pole piece, is adapted to move axially in response to an applied current. According to the invention, the pole piece supports a plurality of "shorting rings" made of high conductivity, low permeability material. The shorting rings are embedded in the pole piece so as to be coextensive with the surface thereof. The spaced shorting rings function as a "shorted turn" which operates to reduce the rise time of current applied to the coil without significantly reducing the magnetic flux in the air gap through which the coil is linearly driven.

Abstract: Method and devices for erasing and writing on magnetic particle oriented media are described. Erasure is caused by moving a magnetic field which enters and exits the media at a finite angle but stays parallel to the media in some region. A magnetic stencil comprising regions of dissimilar permeabilities is described. The magnetic stencil can be used in conjunction with the erasure means to simultaneously create alternating fields parallel and normal to the media thereby permitting information to be written over any previously recorded information without requiring a seperate erasure step.

Abstract: In situations such as the checkout of library books and video cassettes issued by video rental stores, it is desirable to indicate the date by which these materials are due. This patent describes a method and means for displaying the due date by using an erasable and rewritable media affixed to the issuable material. Device for writing/erasing this media is described. Furthermore, method and device for simultaneous reading of bar codes, writing the due date and altering the detectability state of a programmable magnetic strip are disclosed.

Abstract: A resonant AC circuit includes a network of switching elements (e.g., power field-effect transistor) by which the direction of current flow through a coil can be selectively switched at each time in the current cycle, when the current amplitude is substantially zero. Such circuit is particularly advantageous and useful in magneto-optic recording systems for switching the polarity of a magnetic field enabling the direct-overwriting of information on a previously recorded magneto-optic recording element at a high data transfer rate.

Abstract: An axial magnet actuator is disclosed in which a member formed of a magnetic material is movable relative to a frame along an axis. Electromagnets are positioned along the axis at spaced locations. In order to keep the mass of the movable member as small as possible, no magnetic elements are located on the member. An annular permanent magnet is located along the axis between the electromagnets and functions with the electromagnets to move the member, keep the member suspended in an axial direction, and hold the member in a selected position when the electromagnets are not energized.

Abstract: An exposure control device is disclosed in which a member formed of a magnetic material is movable relative to a frame along a predetermined path to control the passage of light along an optical axis. Electromagnets are located on the frame at opposite ends of the path. In order to keep the mass of the movable member as small as possible, no magnetic elements are located on the member. Permanent magnets are located on opposite sides of the path and function with the electromagnets to move the member, keep the member suspended in a direction transverse to the direction of movement, and hold the member in one of two positions when the electromagnets are not energized.

Abstract: A magnetic actuator is disclosed in which a member formed of a magnetic material is movable relative to a frame along a predetermined path. Magnets are located on the frame at opposite ends of the path. In order to keep the mass of the movable member as small as possible, no magnetic elements are located on the member. Permanent magnets function with the magnets at opposite ends of the path to move the member, support the member along one degree of freedom, and hold the member in a rest position.

Abstract: A shutter is disclosed for use as a high-speed shutter in a camera or an electronic device. The shutter comprises a planar aperture blade which is mounted for reciprocative movement. The aperture blade includes a coil which is part of an electromagnetic actuator. A permanent magnet is mounted adjacent the blade for interaction with a magnetic field produced by the coil. In order to provide for a low-friction support, the aperture blade is supported on flexible connectors located on opposite sides of the blade. A current of one polarity is supplied to the coil to move the aperture blade in one direction, and the polarity of the current is reversed to move the blade in the opposite direction.