Fuse link

Abstract

A fuse link used in alternate current medium- or high-voltage systems with a current frequency of 50 Hz includes a spring-type striker pin and is designed for the protection of electrical devices against consequences of short circuits and overloads. A porcelain housing with a star-core, external end caps closed by plugs, star-core end caps with a ring-shaped first tap designed to ensure electric contact between the star-core end cap and the external end cap of the fuse link is also included. A spring-type striker pin is positioned along the axis of the star-core. Each of the end caps of the star-core is provided with an additional second tap designed to centre the star-core relative to the axis of the fuse link. The spring-type striker pin is centred along the longitudinal axis of the fuse link.

Claims

1. A fuse link comprising a porcelain housing with a star-core with wound fuse-elements, external end caps closed by plugs, star-core end caps with a ring-shaped first tap designed to ensure electric contact between the end cap of the star-core and the external end cap of the fuse link, and a spring-type striker pin positioned along the axis of the star-core, characterised in that each of the star-core end caps is provided with a second tap that is designed to centre the star-core relative to the axis of the fuse link and is located on the circumference of the star-core end cap at an obtuse angle () relative to the first tap, measured in a plane perpendicular to the axis of the fuse link, wherein said first and the second taps extend radially outward and axially away from a first edge of said star-core end cap and are provided with spring contacts bent inwardly from a second edge of said star-core end cap towards the direction of the longitudinal axis of the fuse link and in electrical contact with the wound fuse elements, and the spring-type striker pin is radially centred along the longitudinal axis of the fuse link by tongues of a disc spring that is mounted in one of the plugs closing the fuse link on the side where the spring-type striker pin is positioned.

2. The fuse link according to claim 1, characterized in that the taps are provided with a profile plate extending from the star-core end cap which is rim-shaped, wherein the profile pate has an arc shape of a tap rim, that is attached to the edge of the external end cap.

3. The fuse link according to claim 2, characterized in that the profile plate is provided with a longitudinal finger that is bent from the profile plate toward the axis of the tap rim.

4. The fuse link according to claim 1, characterised in that the plug closing the fuse link on the side opposite to the position of the striker pin in the fuse link is provided with a cavity formed in the external lateral surface of the plug used to equalize pressure inside the fuse link with external pressure.

5. The fuse link according to claim 1, characterised in that the external edges of the plug closing the fuse link on the side opposite to the position of the striker pin in the fuse link are in contact with a pressboard spacer for separating a coolant filling an internal space of the porcelain housing and said external end cap from a bottom of the plug.

6. The fuse link according to claim 1, characterised in that it comprises a first seal that is applied along the contact surface between the plug, the disc spring and a housing of the striker pin.

7. The fuse link according to claim 6, characterised in that it comprises a second seal that is applied along the contact surface between the external end cap and the porcelain housing, and is positioned on the external side of the porcelain housing and the internal side of the end cap on the external edges of the porcelain housing.

8. The fuse link according to claim 7, characterised in that it comprises a third seal that is applied along the contact surface between the external end cap and the porcelain housing, and is positioned on the internal side of the housing and the internal side of the end cap on the internal edges of the porcelain housing.

9. The fuse link according to claim 8, characterised in that it comprises a fourth seal that is applied between the plug and the external end cap.

10. The fuse link according to claim 9, characterised in that it comprises a fifth seal that is applied around a clamping sleeve, an insulating bead and a metal housing of the striker pin.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The fuse link according to the present invention, used to protect oil transformers, is shown in an exemplary embodiment in the drawing where:

(2) FIG. 1shows the fuse link in its longitudinal section,

(3) FIG. 2shows the spring-type striker pin in its longitudinal section,

(4) FIG. 3shows the end caps of the star-core positioned at the ends of the star-core, in a longitudinal section,

(5) FIG. 4shows the end cap of the star-core in an isometric projection,

(6) FIG. 5shows the end cap of the star-core with the star-core in a front view,

(7) FIG. 6shows the plug in a front view,

(8) FIG. 7shows the disc spring in an isometric projection,

(9) FIG. 8shows the detail D from FIG. 6 in a front view,

(10) FIG. 9shows the detail A from FIG. 1, in a longitudinal section,

(11) FIG. 10shows the detail B from FIG. 1, in a longitudinal section,

(12) FIG. 11shows the detail C from FIG. 1, in a longitudinal section.

BEST MODE FOR CARRYING OUT THE INVENTION

(13) The fuse link 1 used in medium- or high-voltage systems comprising a porcelain housing 2 that contains an insulation star-core 3 with fuse-elements 4 helically wound around it and connected to electrically conductive star-core end caps 5. The star-core end caps 5 are positioned at the ends of the star-core 3 and pressed against the star-core by spring contacts 6 shown in detail in FIG. 4. The star-core end cap 5 is provided with the first tap 7 and the second additional tap 7. The star-core end cap 5 is rim-shaped and the rim is provided on its one front side with spring contacts 6 that are located around the circumference of one of the edges of the rim and directed towards the centre of the rim. The first tap and the second additional tap 7 are attached to the other side of the rim. Each tap is provided with a profile plate 7a with the profile of an arc attached to the other edge of the rim. Each profile plate 7a is provided with a longitudinal finger 7b that is bent towards the axis of the rim and is designed to ensure electric contact. The taps 7, 7 are located on the circumference of the rim at an obtuse angle , depending on the shape of the star-core 3. The spring-type striker pin 8 is positioned at one end of the fuse link and contains a metal housing 9 with a graded diameter. The fuse link is closed on its both sides using the first metal plug 10a and the second metal plug 10b. The plug 10b contains the centrally positioned striker pin 8. The external end caps 11 are attached to the housing 2 whose internal space is filled with a coolant that is not depicted in the Figure. The section of the metal housing 9, which may be in the form of a sleeve, characterised by a larger diameter contains an axially positioned internal sleeve 12 whose ends are shaped as flanges 12a and 12b of which the flange 12a is bent towards the centre of the sleeve and located on the contact surface of the sleeve 12 with the plug 10. The second flange 12b is bent to the outside of the sleeve 12 and rests on an internal projection formed in the housing 9 in its section where the housing tapers to a smaller diameter. The housing 9 is provided with an external flange bent to the outside of the section characterised by a larger diameter and the flange is connected to the plug 10.

(14) Inside the sleeve 12 and inside the section of the housing characterised by a smaller diameter of the metal housing 9, a tension spring 13 is mounted whose one end rests on the auxiliary washer 14 positioned inside the sleeve 12 next to the flange 12a. The purpose of the washer 14 is to ensure correct support for the thermal washer 15 used to hook on it the internal wire 16 that maintains the stretched state of the spring 13 and is attached at its one end to the tension spring 13 and at its other end to the clamping sleeve 17 that is positioned on the insulating bead 18 that is attached to the end of the metal housing 9.

(15) The plug 10a is formed as two rings with various diameters of which the ring with a smaller diameter is closed using the bottom 19a. The plug 10b is formed as two rings with various diameters of which the ring with a smaller diameter is closed using the bottom 19b with a concentric opening for the striker pin 8 which is not depicted in the Figure. Inside the plug 10b, the disc spring 20 is mounted with the shape of a conical sleeve 20b containing tongues 20a located along the circumference of the conical sleeve 20b characterised by a larger diameter. The disc spring 20 is pressed on one side by the edges of the opening in the sleeve 20b with a smaller diameter against the bent section of the housing 9, and on the other side is pressed by the tongues 20a to the internal walls of the larger ring of the plug 10b. The external walls of the larger ring of the plug 10a have a cavity 21 used to equalize the internal pressure inside the fuse link and the external pressure. The external edges of the larger ring of the plug 10a are in contact with the pressboard spacer 22 separating the coolant from the plug 10a.

(16) The fuse link 1 is provided with seals 23 made from adhesive sealant. The first seal 23a is applied along the contact surface between the bottom 19b, the disc spring 20 and the housing 9 of the striker pin 8. The second seal 23b is applied along the contact surface between the external end cap 11 and the porcelain housing 2 on the external side of the housing 2 and on the internal side of the end cap 11 on the external edges of the housing 2. The third seal 23c is applied along the contact surface between the external end cap 11 and the porcelain housing 2 on the internal side of the housing 2 and on the internal side of the end cap 11 on the internal edges of the housing 2. The fourth seal 23d is applied between the plug 10a and the external end cap 11. The fifth seal 23e is applied around the clamping sleeve 17, the insulating bead 18 and the metal housing of the striker pin 9, as depicted in FIG. 2. The purpose of the adhesive sealant is to prevent external substances from penetrating the internal space of the fuse link.

(17) The current circuit of the fuse link consists of the external end cap 11, the tap 7, the star-core end cap 5, the fuse-elements 4, the star-core end cap 5, the tap 7 and the external end cap 11. The operation of the fuse link 1 consists in switching off and limiting short-circuit or overload currents by blowing the fuse-elements 4 of the fuse link 1, and then by blowing the internal wire 16 of the spring-type striker pin 8 which releases the tension spring 13 and consequently pushes out the sleeve 12 of the spring-type striker pin 8 and breaks the current circuit. The protruding sleeve 12 of the striker pin 8 also provides a signal of fuse link actuation and may be used to actuate a switch that is not depicted in the Figure.

(18) A List of Marks Used in the Figure.

(19) 1Fuse link 2Porcelain housing 3Star-core 4Fuse-elements 5Star-core end caps 6Spring contacts 7Tap, 7 Additional Tap (7aprofile plate, 7bfinger) 8Spring-type striker pin 9Metal housing of the striker pin 10Plug (10a, 10b) 11External end caps 12Slidable internal sleeve of the striker pin (sleeve flanges 12a, 12b) 13Tension spring 14Auxiliary washer 15Thermal washer 16Internal wire 17Clamping sleeve 18Insulating bead 19Bottom of the plug (19a, 19b) 20disc spring (20a spring tongue, 20b conical sleeve) 21Cavity in the plug 22Pressboard spacer 23Seal (23a, 23b, 23c, 23d, 23e)