Varistor comprising an electrode having a protruding portion forming a pole and protection device comprising such a varistor

• US 8,378,778 B2
• Filed: 04/08/2011
• Issued: 02/19/2013
• Est. Priority Date: 04/09/2010
• Status: Active Grant

• Current Assignee: Abb France (ABB Ltd.)
• Original Assignee: Abb France (ABB Ltd.)
• Inventors: Lagnoux, Alain, Duval, Michael
• Primary Examiner(s): LEE, KYUNG S
• Application Number:
  US13/083,041
• Publication Number:
  US 20110248816A1
• Time in Patent Office: 683 Days
• Field of Search: 338/20
• US Class Current: 338/20
• CPC Class Codes: H01C 7/126 Means for protecting against excessive pressure or for disconnecting in case of failure

Abstract

An exemplary varistor is disclosed which includes at least two poles; a non-linear block; a conductive plate arranged on a main face of the block and having a protruding portion forming one of the poles; and an electrically insulating coating applied to the main face of the block. The part forming the connection pole emerges from the electrically insulating coating and has a braze surface extending above the electrically insulating coating; and the protruding part forming the connection pole is connected to the rest of the plate over at least half of the perimeter thereof.

Claims

1. A varistor, comprising:

at least two connection poles;

a block having a non-linear electrical resistance whose value will vary as a function of voltage applied to the two connection poles;

a conductive plate forming a contact electrode with the block, said conductive plate being arranged on a main face of the block and having a protruding portion forming one of the two connection poles; and

an electrically insulating coating applied to at least an assembly formed by said main face of the block and the conductive plate arranged on said main face of the block, wherein;

said protruding portion forming the one connection pole emerges from the electrically insulating coating and has a braze surface for electrical connection, said braze surface extending above the electrically insulating coating; and

said protruding portion forming the one connection pole is connected to the conductive plate over at least half of a perimeter thereof.

2. The varistor according to claim 1, wherein said protruding portion forming the one connection pole is connected to the plate over at least 80% of its perimeter.

3. The varistor according to claim 1, wherein said protruding portion forming the one connection pole is formed by drawing of the conductive plate.

4. The varistor according to claim 1, wherein said braze surface is situated at least 0.1 mm above the electrically insulating coating.

5. The varistor according to claim 1, wherein said protruding portion forming the one connection pole is situated inside an imaginary circle centered on said main face of the block and having a diameter equal to 75% of a diameter of the circle inscribed on the main face of the block.

6. The varistor according to claim 1, wherein the conductive plate is centered on said main face of the block.

7. The varistor according to claim 1, wherein a remainder of the conductive plate around the protruding portion forming the one connection pole is solid.

8. The varistor according to claim 1, wherein a surface of the conductive plate in contact with said main face of the block has an area that is at least half an area of the main face of the block.

9. The varistor according to claim 1, wherein the braze surface is parallel to said main face of the block.

10. The varistor according to claim 1, wherein the electrically insulating coating completely coats the varistor to form a coating through which an other of the two connection poles, or other connection poles, emerge.

11. The varistor according to claim 1, in combination with at least one other varistor to form a set of varistors assembled in a compact mass, wherein the two varistors are electrically connected to each other and have a shared pole, the set of varistors being completely coated with the electrically insulating coating through which connection poles of the varistors emerge.

12. The varistor according to claim 1, in combination with a protective device for protecting an electrical installation from voltage surges, comprising:

a thermal disconnector, comprising a mobile contact suitable of moving from a closed position to an open position to disconnect the varistor;

wherein the mobile contact is kept in the closed position by a thermofusible braze fastening the mobile contact on the braze surface of said protruding portion forming the one connection pole of the varistor, the thermal disconnector being provided for making the mobile contact go to the open position when the thermofusible braze melts, and

wherein the mobile contact is provided for moving from the closed position to the open position, parallel to said main face of the block of the varistor and away from the electrically insulating coating of the varistor.

13. The varistor according to claim 12, wherein the protective device comprises:

at least two terminals for connecting the device to an electrical installation and wherein the mobile contact is a contact blade extending primarily in a plane parallel to said main face of the block of the varistor and mainly opposite said main face, the contact blade and one of the connection terminals being part of a single, common piece.

14. The varistor according to claim 13, wherein the piece to which the contact blade and said one of the two connection terminals belong has an IACS conductivity greater than or equal to 70%.

15. The varistor according to claim 13, wherein the part of the contact blade maintained on the braze surface of said protruding portion forming the one connection pole is connected to a remainder of the contact blade by a local restriction of a section of the contact blade to concentrate heat when given off by the varistor at the thermofusible braze.

16. The varistor according to claim 12, in combination with a cartridge comprising:

a case,

the protective device for protecting an electrical installation from voltage surges; and

pins for connecting the protective device to an electrical installation to be protected,

wherein the protective device is housed in the case and the pins protrude outside the case, the case defining a parallelepiped inner volume in which the protective device is housed, an inner volume having maximum dimensions of 15×

42×

43 mm.

17. The varistor according to claim 1, wherein said protruding portion forming the one connection pole is connected to the plate over its entire perimeter.

18. The varistor according to claim 1, wherein said braze surface is situated at least 0.3 mm above the electrically insulating coating.

19. The varistor according to claim 13, wherein the piece to which the contact blade and said one of the two connection terminals belong has an IACS conductivity greater than or equal to 90%.

20. The varistor according to claim 13, wherein the piece to which the contact blade and said one of the two connection terminals belong has an IACS conductivity greater than or equal to 95%.