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US 7,433,169 B2Granted
Overvoltage protection devices including wafer of varistor material
AssigneeRaycap, S.A.
InventorsSherif I. Kamel, Zafiris Politis, Konstantinos Samaras
Life of this patent
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Abstract
An overvoltage protection device includes first and second electrically conductive electrode members, a varistor member formed of a varistor material and electrically connected with each of the first and second electrode members, and an electrically conductive, meltable member. The meltable member is responsive to heat in the device to melt and form a current flow path between the first and second electrode members through the meltable member.
Claims31
An overvoltage protection device comprising:
- a) first and second electrically conductive electrode members;
- b) a varistor member formed of a varistor material and electrically connected with each of the first and second electrode members;
- and
- c) an electrically conductive, meltable member, wherein the meltable member is responsive to heat in the device to melt and form a current flow path between the first and second electrode members through the meltable member;
- wherein the varistor member is adapted to generate heat from ohmic losses in the varistor member when the varistor member is in an end of life mode, and the meltable member is responsive to heat generated from ohmic losses in the varistor member when the varistor member is in its end of life mode to melt and form the new current flow path to prevent catastrophic destruction of the device due to thermal runaway.
2 more elements
A method for providing overvoltage protection, the method comprising:
- providing an overvoltage protection device including:
- first and second electrically conductive electrode members;
- a varistor member formed of a varistor material and electrically connected with each of the first and second electrode members;
- and
- an electrically conductive, meltable member;
- directing current through the varistor member responsive to an overvoltage event;
- directing current through the varistor member while the varistor member is in an end of life mode such that heat is generated in the varistor member from ohmic losses and;
- responsive to the heat in the device from ohmic losses, melting the meltable member to form a new current flow path between the first and second electrode members through the meltable member that inhibits at least some electrically induced heating of the device.
5 more elements
An overvoltage protection device comprising:
- a) first and second electrically conductive electrode members;
- b) a varistor member formed of a varistor material and electrically connected with each of the first and second electrode members;
- and
- c) an electrically conductive, meltable member, wherein the meltable member is responsive to heat in the device to melt and form a new current flow path between the first and second electrode members through the meltable member to inhibit at least some electrically induced heating of the device;
- wherein the varistor member is adapted to generate heat from ohmic losses in the varistor member when the varistor member is in an end of life mode and subjected to an extended overcurrent event, and the meltable member is responsive to heat generated from ohmic losses in the varistor member when the varistor member is in its end of life mode and subjected to an extended overcurrent event to melt and form the new current flow path to prevent catastrophic destruction of the device due to thermal runaway;
- and
- wherein the meltable member has a melting point that is greater than a prescribed maximum standard operating temperature, wherein the prescribed maximum standard operating temperature is the greatest temperature expected in the meltable member during normal operation but not during operation which, if left unchecked, would result in thermal runaway of the device.
4 more elements
A method for providing overvoltage protection, the method comprising:
- providing an overvoltage protection device including:
- first and second electrically conductive electrode members;
- a varistor member formed of a varistor material and electrically connected with each of the first and second electrode members;
- and
- an electrically conductive, meltable member, wherein the meltable member has a melting point that is greater than a prescribed maximum standard operating temperature, wherein the prescribed maximum standard operating temperature is the greatest temperature expected in the meltable member during normal operation but not during operation which, if left unchecked, would result in thermal runaway of the device;
- directing an extended overcurrent through the varistor member while the varistor member is in an end of life mode such that heat is generated in the varistor member from ohmic losses;
- and
- responsive to said heat from ohmic losses in the varistor member, melting the meltable member to form a new current flow path between the first and second electrode members through the meltable member that inhibits at least some electrically induced heating of the device.
5 more elements
Dependencies are inferred from the claim text.