Overload protected solid state varistors
First Claim
Patent Images
1. A solid state varistor having thermal overload protection, comprising:
- a metal oxide varistor; and
leads connected to the semiconductor device, at least one of the leads having a fusible link between separated portions of the at least one lead, the fusible link being meltable when heated to a predetermined temperature creating an open circuit between the separated portions, anda heat sensitive elastic member formed around the fusible link to further separate the separated portions as the fusible link melts.
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Abstract
A fail-safe varistor includes either a fail-short or a fail-open device. Both devices include a fusible, electrically conductive material that melts before the varistor fails due to overvoltage. In the fail-open device, the fusible, electrically conductive material joins separated portions of the leads. The material also may join at least one of the leads directly to a ceramic disk of the varistor. Upon reaching the predetermined temperature, the varistor melts causing a circuit including the varistor to open. In the fail-short device, the material melts creating a short between the leads. This short causes a fuse or a breaker to open the circuit.
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Citations
11 Claims
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1. A solid state varistor having thermal overload protection, comprising:
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a metal oxide varistor; and leads connected to the semiconductor device, at least one of the leads having a fusible link between separated portions of the at least one lead, the fusible link being meltable when heated to a predetermined temperature creating an open circuit between the separated portions, and a heat sensitive elastic member formed around the fusible link to further separate the separated portions as the fusible link melts. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A solid state varistor having thermal overload protection, comprising:
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a metal oxide varistor having first and second surfaces; a first lead electrically connected to the first surface; a fusible link electrically connected to said second surface; and a second lead electrically connected to said second surface through said fusible link, said fusible link being enclosed in a containment material such that as said fusible link melts within said containment material, an open circuit is formed between said second lead and said second surface.
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11. A solid state varistor having thermal overload protection, comprising:
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a metal oxide varistor; and leads connected to the metal oxide varistor, at least one of the leads having a proximal portion and a distal portion, the proximal portion having a proximal straight portion and a proximal bend portion, the distal portion having a distal straight portion and a distal bend portion, the proximal bend portion and the distal bend portion being electrically connected by a fusible link, the fusible link being meltable as heated to a predetermined temperature creating an open circuit between the proximal bend portion and the distal bend portion.
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Specification