AU2004232163B2

AU2004232163B2 - Pressure relief for current limiter

Info

Publication number: AU2004232163B2
Application number: AU2004232163A
Authority: AU
Inventors: Glenn R. Borchardt
Original assignee: S&C Electric Co
Current assignee: S&C Electric Co
Priority date: 2003-03-25
Filing date: 2004-03-18
Publication date: 2009-03-19
Anticipated expiration: 2024-03-18
Also published as: WO2004095491A2; CN100466143C; WO2004088811A2; KR101043517B1; CA2520116A1; WO2004088811A3; CA2520116C; KR20050115296A; AU2004232163A1; CN1771576A; WO2004095491A3

Description

PRESSURE RELIEF FOR CURRENT LIMITER Background of the Invention Field of the Invention The present invention relates generally to the field of current-limiting fuses for electrical power distribution systems and more particularly to an improved current limiter that provides pressure relief of internal pressures during operation of the current limiter.

Description of Related Art Various current-limiting fuse arrangements are known in the prior art, e. g. see U. S.

Patent Nos: 5,604, 475 and 5,502, 427.

Object of the Invention It is the object of the present invention to substantially overcome or ameliorate one or more of the disadvantages of the prior art.

Summary of the Invention The present invention provides a current-limiting device, said device developing internal heat and pressure during operation thereof, said current-limiting device including: a housing, said housing defining an interior and an exterior, a contact terminal for electrical connection between the interior and the exterior, and a pressure relief arrangement adapted to communicate the interior to the exterior when predetermined high-current fault conditions are experienced, the pressure relief arrangement comprising: a passage formed through the contact tenninal, and a fusible material disposed within the passage, said fusible material being adapted to melt in response to a predetermined internal temperature resulting from said predetermined high-current fault conditions.

Preferably, the current-limiting device further includes an adjoining exhaust section and the contact terminal extends into the adjoining exhaust section.

AH21(1980479 I :INK Brief Description of the Drawings A preferred embodiment of the present invention will now be described, by way of an example only, with reference to the accompanying drawings wherein: s FIG. 1 is an elevational view of the current limiter of the present invention with parts removed for clarity; FIG. 2 is a partial, enlarged view of the current limiter of FIG. 1; and FIGS. 3-5 are respective front, bottom and right-hand elevational views of a contact terminal of the current limiter of FIGS. 1 and 2.

I0 Detailed Description of the Preferred Embodiments In an illustrative embodiment of the present invention and with reference to FIGS. a limiter 17 in accordance with the present invention and of the general type as shown in U. S.

Patent Nos. 5,604, 475 and 5,502, 427, includes pressure relief provisions to relieve the internal pressure of the limiter 17 during operation thereof.

The limiter 17 includes a fusible element 14 positioned about a predetermined circuitous path tluough a housing 19 of the limiter 17. In the illustrative embodiment, the limiter 17 includes an exhaust/venting section 21 with controlled exhaust at 23 formed integrally as part of the limiter 17. As shown in U. S. Patent No. 5,502, 427, the exhaust/venting section 21 interfits with a fuse tube assembly (not shown) at 25 to form a low-current section of an overall fuse limiter. The low-current section is electrically connected in series with the limiter 17 via a contact terminal 27 best seen in FIGS. However, this should not be interpreted in any limiting sense since the present invention may be practiced without an integral exhaust/venting section 21, e. g. as shown in U. S. Patent No.

5,604, 475. During current-limiting operation at high-current fault conditions, high internal pressures and temperatures are developed within the limiter 17 which is sealed firom the exterior environment.

To improve the withstand of the limiter 17 during high-current fault conditions, internal pressure relief is provided at 26 for the limiter 17 via venting to the exterior of the limiter 17, e. g. via provisions providing a passage at 29 through the contact tennrminal 27 in the illustrative embodiment that are operative in response to high-temperature conditions within the limiter 17. In a specific illustrative embodiment, a passage 31 in the portion of the contact terminal 27 within the interior of the limiter 17 communicates with the passage 29 that AH21(1980479 II:INK continues through the contact terminal 27 to the interior of the exhaust/venting section 21.

Fusible material at 33 is provided within the passage 31 such that under normal conditions the communication through passages 31 and 29 are sealed to the exhaust/venting section 21.

When the limiter 17 operates under high-current fault conditions, the terminal 27 is heated and the AH21(1980479 I):INK WO 2004/095491 PCT/US2004/008017 3 fusible material at 33 is melted and the internal pressures are vented into the exhaustlventing section 21 and out to the external environment. In a specific embodiment, the fusible material at 33 is a low melting-point solder. Thus, with the pressure relief provisions at 26, the present invention provides increased withstand of the limiter 17 to high-current fault conditions to achieve either higher ratings or reduced requirements on the housing 19.

In a specific embodiment, the passage 29 is arranged in a predetermined configuration through the contact terminal 27, e.g. sloped from one end to the other so as to appropriately interface with a contact (not shown) of the fuse tube assembly of U.S. Patent No. 5,502,427 as discussed hereinbefore. In this manner, the opening 35 of the passage 29 at the exterior end of the contact terminal 27 does not interfere with a preferred contact area at this exterior end of the contact terminal.

While there have been illustrated and described various embodiments of the present invention, it will be apparent that various changes and modifications will occur to those skilled in the art. Accordingly, it is intended in the appended claims to cover all such changes and modifications that fall within the true spirit and scope of the present invention.

Claims

1. A current-limiting device, said device developing internal heat and pressure during operation thereof, said current-limiting device including: a housing, said housing defining an interior and an exterior, a contact terminal for electrical connection between the interior and the exterior, and a pressure relief arrangement adapted to communicate the interior to the exterior when predetermined high-current fault conditions are experienced, the pressure relief arrangement comprising: a passage formed through the contact terminal, and a fusible material disposed within the passage, said fusible material being adapted to melt in response to a predetermined internal temperature resulting from said predetermined high-current fault conditions.

2. The current-limiting device of claim 1 further including an adjoining exhaust section and wherein the contact terminal extends into the adjoining exhaust section.

3. A current limiting device substantially as hereinbefore described with reference to the accompanying drawings. Dated 26 February 2009 S C Electric Company Patent Attorneys for the Applicant/Nominated Person SPRUSON FERGUSON AH21(1980479 I):INK