Metal oxide varistors having thermal protection
First Claim
1. A thermal protection device for a metal oxide varistor (MOV) to prevent thermal runaway of said MOV comprising:
- a) a circular MOV element which heats up when exposed to voltage spikes;
b) a flat thermal fusible, layer upon at least a portion of a surface of said MOV element and directly adhered to such MOV element, said thermal fusible material layer capable of conducting current therethrough and having a predetermined temperature at which it melts and interrupts any flow of current through said thermal fusible material layer;
c) a first conductor having a first end and a second end, said first end coupled directly to a first surface of said MOV element and said second end coupled to a source of current; and
d) a second conductor having a third end and a fourth end, said third end directly coupled to said thermal fusible material layer and said fourth end coupled to said source of current whereby current is permitted to flow through said first conductor, said MOV, said thermal fusible material and said second conductor when said thermal fusible material layer is held below said predetermined temperature and current flow is interrupted when said thermal fusible material layer goes above said predetermined temperature and melts due to the heat provided by said MOV element.
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Accused Products
Abstract
A layer of thermal fusible material is placed on one surface of a metal oxide varistor (MOV) to monitor the heating of the MOV due to applied voltage spikes. The thermal fusible material is part of the electrical circuit which includes the MOV and melts at a predetermined temperature. In the presence of a severe or a number of voltage spikes the MOV heats up and the heat transferred to the thermal fusible material causes it to open the electrical circuit to the MOV to prevent overheating and thermal runaway. In another form, the MOV is separated into two halves and the thermal fusible material layer is placed between the ends of the MOV halves.
46 Citations
14 Claims
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1. A thermal protection device for a metal oxide varistor (MOV) to prevent thermal runaway of said MOV comprising:
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a) a circular MOV element which heats up when exposed to voltage spikes; b) a flat thermal fusible, layer upon at least a portion of a surface of said MOV element and directly adhered to such MOV element, said thermal fusible material layer capable of conducting current therethrough and having a predetermined temperature at which it melts and interrupts any flow of current through said thermal fusible material layer; c) a first conductor having a first end and a second end, said first end coupled directly to a first surface of said MOV element and said second end coupled to a source of current; and d) a second conductor having a third end and a fourth end, said third end directly coupled to said thermal fusible material layer and said fourth end coupled to said source of current whereby current is permitted to flow through said first conductor, said MOV, said thermal fusible material and said second conductor when said thermal fusible material layer is held below said predetermined temperature and current flow is interrupted when said thermal fusible material layer goes above said predetermined temperature and melts due to the heat provided by said MOV element. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A thermal protection device for a metal oxide varistor (MOV) to prevent thermal runaway of said MOV comprising:
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a) a first semi-circular segment MOV element defined by a first straight side surface and a first curved side surface; b) a second semi-circular segment MOV element defined by a second straight side surface and a second curved side surface; c) said first semi-circular segment and said second semi-circular segment generally describing a circular MOV when said first straight side surface is held parallel with said second straight side surface; d) said first semi-circular segment MOV element and said second semi-circular segment MOV element heat up when exposed to voltage spikes; e) said first semi-circular segment having a first front surface and a first rear surface, said second semi-circular segment having a second front surface and a second rear surface; f) a thermal fusible material layer extending between said first semi-circular segment first straight side surface and said second semi-circular segment second straight side surface, said thermal fusible material layer capable of conducting current therethrough and having a predetermined temperature at which it melts and interrupts any flow of current through said thermal fusible material layer; g) a first conductor having a first end and a second end, said first end coupled to one of said first front and first rear surfaces of said first semi-circular segment and said second end coupled to a source of current; and h) a second conductor having a third end and a fourth end, said third end coupled to one of said second front and second rear surfaces of said second semi-circular segment and said fourth end coupled to said source of current whereby current is permitted to flow through said first conductor, said first semi-circular segment, said thermal fusible material layer, said second semi-circular segment and said second conductor when said thermal fusible material layer is held below said predetermined temperature and current flow is interrupted when said thermal fusible material layer goes above said predetermined temperature and melts due to the heat provided by said first and second MOV segments. - View Dependent Claims (12, 13, 14)
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Specification