Raychem Limited

Justin N Chiang

John A Midgley

Hugh Duffy

Paul Becker

Mark S Thompson

Philip J Jones

Lawrence J White

Brian Thomas

A Brian Macknick

Electrical circuit protection arrangements with PTC devices and mechanical switches. The combinations of this invention permit the use of mechanical switches and PTC devices to switch voltages and currents in normal circuit operations, wherein the voltage and/or current ratings of the mechanical switches and PTC devices are much less than the normal operating voltages and currents of the circuits. This feature permits the use of smaller and less expensive mechanical switches and PTC device than would otherwise be required in such circuits. The arrangements of switches and PTC devices also permit the PTC devices to limit the magnitude of the fault current passed to the circuit.

Overcurrent protection circuits comprising combinations of PTC devices

An electrical protection system which uses a ground fault interrupter (GFI) to protect a circuit from (A) ground faults and (B) overcurrents and/or overvoltages. For overcurrent protection, a control element may be coupled in series with the line or return input to the GFI, and a bypass element may be coupled in parallel with the control element and the GFI. In case of an overcurrent, the control element causes current to be diverted through the bypass element, thereby creating a current imbalance in the GFI circuitry causing the GFI to open the circuit. For overvoltage protection, a bypass element (e.g. a varistor) may be coupled between, e.g., the line sense input of the GFI and the return sense input of the GFI. In case of an overvoltage, the bypass element conducts current, thereby creating a current imbalance in the GFI circuitry causing the GFI to open the circuit.

Circuit protection arrangements using ground fault interrupter for

A liquid crystal display comprises (a) a first transparent base; (b) a plurality of first picture electrodes on the first transparent base; (c) a plurality of data lines for supplying electrical signals to the first picture electrodes; (d) a second transparent base, parallel to and spaced apart from the first transparent base; (e) a plurality of second picture electrodes on the second transparent base; (f) a plurality of varistor elements made of a varistor material comprising zinc oxide as a primary metal oxide and cobalt and praseodymium oxides as additive metal oxides, in amounts of between 0.1 and 8.0 atom % cobalt and between 0.08 and 8.0 atom % praseodymium, one varistor element being associated with and in electrical contact each second picture electrode; (g) a plurality of scan lines for supplying electrical signals to the second picture electrodes via the respective associated varistor elements; and (h) electrooptically active liquid crystal material between the first and second picture electrodes. In a preferred embodiment, the plurality of varistor elements is in the form of a varistor array comprising an integral body of varistor material having two major opposing faces, one of the opposing faces having an array of indentations thereon, each indentation defining a varistor element.

Varistor driven liquid crystal display

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Newark, CA, United States of America

Justin N Chiang