Claims:We Claim:

1. A connection assembly for a transformer-bus bar connection, wherein the connection assembly comprises:

a. a transformer stud (122) with a threaded section (124);

b. a collet (110) with a threaded (126) central through bore and a conical outer surface (128) with longitudinal slits, wherein

i. the threads (124) on the transformer stud and the threads (126) on the central bore of the collet (110) are complimentary; and

ii. the collet (110) is threaded on the transformer stud (122); and
characterized in comprising,

c. a bus bar (102) which at a first end (104) comprises a through bore with a taper surface (130), wherein

i. the taper surface (130)has the same incline as the conical outer surface (128) of the collet;

ii. the taper surface (130) and the conical outer surface (128) form a tight interface when the bus bar (102) is placed over the collet (110); and

iii. the inclination of the interface increases outwardly towards the transformer side; and

d. ashearoff nut (116)placed on the protruding section of the transformer stud (122) to secure the connection assembly, wherein the shear off nut (116) engages with the Bus bar (102).

2. The connection assembly, as claimed in claim 1, wherein taper angle of the taper surface (130) is in the range of 5 to 10 degree.

3. The connection assembly, as claimed in claim 1, wherein the bus bar (102) at a second end comprises:

a) a heat shrink cable breakout (106) for connecting to networking cables; and

b) Shear head screws (108) to secure the connection to the networking cables.

4. The connection assembly, as claimed in claim 1, comprises an O ring (112) placed on the collet (110)to provide easy installation and an O ring (118) placed on the shear off nut (116) to facilitateproper share head breaking.

5. The connection assembly, as claimed in claim 1, wherein the bus bar (102), the collet (110), the shear off nut (116) and the Shear head screws (108) are made of Aluminium alloy.
6. The connection assembly, as claimed in claim 1, comprises an insulation cover (120) to form a protective cover over the connection assembly.

7. The connection assembly, as claimed in claim 1, wherein the connection assembly is formed by

a. threading the collet (110) on the transformer stud(122) with the wider end of the collet (110) towards the transformer,

b. placing the first end of the bus bar (104) on the collet (110) such that the taper surface (130) in the through bore of the bus bar (102) engages with the inclined outer surface (128) of the collet (110),

c. placing the shear off nut (116) on the protruding part of the transformer stud (122) to engage with the Bus bar (102), and

d. tightening the shear off nut (116) to secure the assembly.

Dated this 28th day of Feb 2022

For SICAME INDIA CONNECTORS PVT LTD
By its Patent Agent

Dr.B.Deepa
IN/PA 1477
, Description:Form 2

THE PATENT ACT, 1970
(39 of 1970)
&
THE PATENT RULES, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)

“TRANSFORMERCONNECTOR FOR LV 1.1KV SIGNAL CORE UNARMOURED CABLE”

in the name of SICAME INDIA CONNECTORS PVT LTD an Indian nationals having address at, S.NO: 473/1 (part), # 96 SIRUNKUNDRAM VILLAGE, CHENGALPET TALUK, KANCHIPURAM DISTRICT-603108, TAMIL NADU, INDIA.

The following specification particularly describes the invention and the manner in which it is to be performed
FIELD OF THE INVENTION:

The present invention relates to the field of mechanical connection assemblies. In particular, the present invention relates to a connection assembly for a transformer-bus bar connection.

BACKGROUND OF THE INVENTION:
Electrical transformers are typically used to distribute electrical power from main utility lines for secondary distribution. The transformer connects to the main utility line on the primary side of the transformer and distributes the power from a secondary side of the transformer, namely the LV (low voltage) side of transformer. An electrical step-down is provided by the transformer so as to provide for the proper secondary distribution of electrical power for residential and commercial use.
Threaded copper studs extend from the secondary side of the transformer from which secondary distribution is provided. Multiple tap connections, connected to the threaded studs, provide for distribution of power to the end user. In order to connect the connections to the stud, a bus bar is employed. These bus bars are elongate, electrically conductive members which are inserted over the copper stud extending from the LV side of the transformer. The transformer-bus bar connection is enabled through a connection assembly.
In the prior art, typically the bus bar is bolted to the transformer stud. The screw-on version has an internal thread in the connector matching the thread on the transformer stud and is installed by rotating the connector onto the threaded stud. Since the stud is of considerable length, a large number of revolutions of the connector are required to seat and lock the connector on the stud. This will result in random orientation at the end of installation or may result in sliding between bus bar and transformer stud.
Alternatively, the connection can be of a slip-fit type. The slip fit has an oversized hole compared to the stud diameter. The bus bar is installed by sliding the oversized connector over the threaded stud and tightening a jam screw from the top side of the connector to force the internal and external threads to mesh. The contact area is less than a perfect fit since the diameters do not match and the threads between the stud and connector do not completely seat. Moreover, the contact between the stud and the connector occurs only along a very narrow strip along the bottom of the stud. Also, as a result of the limited interface, the connector has a tendency to pivot when pressure is applied to the outer end of the connector. This has a potential to loosen the connection and cause a failure.
Hence a transformer-bus bar connection which overcomes these drawbacks and provides a tight fit with easy installation is required. Moreover obtaining the desired orientation of the bus bar is also important for safe alignment of the tap connections at the LV side of the transformer.
OBJECTIVE OF THE INVENTION

The main objective is to develop a connection assembly for a transformer-bus bar connection with minimum resistance of contact and maximum performance.
Another objective is to develop the connection assembly for a transformer-bus bar connection with less losses and less failure of joints, while enabling easy manufacturing and installation

SUMMARY OF THE INVENTION

The present invention discloses a connection assembly for a transformer-bus bar connection. The connection assembly comprises of a bus bar which at a first end comprises a taper, a collet with a threaded central bore and a conical outer surface, and a transformer stud with a threaded section wherein the threads on the transformer stud and the central bore of the collet are complimentary. Further, the conical outer surface of the collet is of the same incline as that of the taper at the first end of the bus bar. The connection assembly further comprises a shear off nut to secure the connection assembly.

LIST OF FIGURES

Figure 1 illustrates anexploded view of the connection assembly for a transformer stud-bus bar connection as an embodiment of the present invention.

Figure 2(a) illustrates a profile view of the connection assembly for a transformer stud-bus bar connection as an embodiment of the present invention.

Figure 2(b) illustrates a profile view of the connection assembly for a transformer stud-bus bar connection as an embodiment of the present invention.

Figure 3 illustrates a collet in (a) front view and (b) side view as an embodiment of the present invention.

Figure 4illustrates a sectional view of the connection assembly for a transformer stud-bus bar connection as an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention discloses a connection assembly for a transformer stud-bus bar connection.

At a low voltage side of a transformer, transformer studs are provided. In order to connect a networking cable, bus bars are used with at one end are connected to the transformer stud and at another end connect to the networking cable for power transfer from the transformer to the networking cables. The sturdiness of the connections is important for the efficient power transmission and prevention of failure.

A transformer is provided with transformer studs at the low voltage side for tapping power. The transformer studs may be made of copper or any other conducting material. Further, the transformer stud has a threaded portion which is to be used for making the connection. The transformer stud is the commonly available stud in the prior art.

The present invention discloses a bus bar which at a first end connects to the transformer stud. The first end has a through opening with a tapering cross section. The first end of the bush bar is fixable on the transformer stud oriented with the narrow opening away from the transformer end and the wide opening towards the transformer. The taper angle is in the range of5 to 10 Degree.

In order to fix the first end of the bus bar on the transformer, the present invention discloses a collet which comprises a threaded internal through bore. The collet comprises an inclined outer surface. The part of the collet, which is subjected to engagement, is split into longitudinal slits to allow better engagement between the collet and the stud. The incline of the outer surface of the collet is same as the taper in the opening in the first end of the bus bar. Hence, the collet fits in the opening at the first end of the bus bar. Further, the threaded internal through bore of the collet has threads which match with the threads on the threaded portion of the transformer stud.
Hence, the collet can be threaded down the length of the transformer stud.
Therefore, in order to fix the bus bar on the transformer stud, the collet is threaded down the length of the transformer stud and the bus bar is placed to seatthe taper surface on the outer surface of the collet. A shear off nut is placed on the bus bar such that the shear off nut engages with the bus bar. On tightening the shear off nut, the bus bar and the collet are locked in a wedge clamping mechanism along their interface. The engagement of the bus bar and the collet produces a corresponding engagement pressure on the stud through the collet.

List of features:
1. Bus bar (102)
2. a first end of bus bar (104)
3. heat shrink cable breakout (106)
4. shear headscrewfor conductor(108)
5. collet (110)
6. O ring (112)
7. a plastic lock (114)
8. a shear off nut for bus bar(116)
9. O ring (118)
10. insulation cover (120)
11. transformer stud (122)
12. threaded outer surface of transformer stud (124)
13. threaded inner surface of collet (126)
14. inclined outer surface (128)
15. taper surface (130)

Figure 1 illustrates an exploded view of the connection assembly for a transformer stud-bus bar connection as an embodiment of the present invention. A bus bar (102) at a first end (104) comprises a through opening with a tapering cross section. At a second end a heat shrink cable breakout (106) is provided for connecting to the networking cables. Typically the heat shrink cable breakout (106) is made of a thermoplastic material. Shear head screws(108) are provided to secure the connection to the networking cables. A collet (110) is positioned in the opening at the first end (104). The collet (110) has a through hole with a threaded inner surface. An O ring (112) is placed on the collet (110) to provide a holding during installation for easy installation. Further, a plastic lock (114) configured to fit on the collet (110) to provide proper alignment of collet (110).A shear off nut (116) is used for tightening the connection with the transformer stud and an O ring (118) is provided to facilitate proper shear head breaking. An insulation cover (120) is provided to form a protective cover over the connection assembly. The transformer stud is not shown in this figure.

In an embodiment of the present invention, the bus bar (102), the collet (110), the shear off nut (116)and the Shear head screws (108) are made of Aluminium alloy. The O rings (112) and (118) are made of an elastomer. The plastic lock (114) is made of a thermoplastic material. The insulation cover (120) is made of PVC.The insulation cover (120) is removable and provided with color identification for phase. The insulation cover (120) prevents directly exposure of the connection assembly to the atmospheres.

Figure 2(a) illustrates a front profile view of the connection assembly for a transformer stud-bus bar connection as an embodiment of the present invention. The insulation cover (120) covers the connection assembly. The shear off nut (116) is screwed on to secure the connection assembly. Figure 2(b) illustrates a side profile view of the connection assembly for a transformer stud-bus bar connection as an embodiment of the present invention. The transformer stud is not shown in this figure.

Figure 3 illustrates a collet in (a) front view and (b) side view as an embodiment of the present invention. The collet (110) has an inclined outer surface (128). The part of the collet, which is subjected to engagement, is split into longitudinal slits.

Figure 4illustrates a sectional view of the connection assembly for a transformer stud-bus bar connection as an embodiment of the present invention.The transformer stud (122) has a threaded outer surface (124). The collet (110) has a through bore with a threaded inner surface (126). The threads of the inner surface (126) of the collet (110) are complimentary with the threads on the outer surface (124) of the transformer stud (122).The collet (110) is threaded on the transformer stud (122). The collet (110) has an inclined outer surface (128) which has the same incline as the taper (130) of the through bore in the bus bar (102). Hence, when the bus bar (102) is placed over the collet (110), the surface (128) and the surface (130) form a tight interface. The inclination of the interface increases outwardly towards the transformer side. The shear off nut (116) is finally placed to engage with the bus bar (102). On tightening the shear off nut (116), the surface (128) and the surface (130) develop sufficient torque to form a secure connection. The bush bar (102) through bore radially compresses the collet (110) and the friction developed between the surface (128) and the surface (130) creates a tight fit which is sturdy against any external loads. The radial compression on the collet (110) further creates a frictional force in the threaded joint between the collet (110) and the transformer stud (122) which may result in marginal deformation on the threads to force fit into a strong threaded joint. Ashear off head of the shear off nut (116)allows application of precise torque values which will prevent incorrect installation.

It is to be noted that during the assembly, there is no change in the orientation of either the transformer stud (122) or the bus bar (102). Hence the orientation of the networking cable is not disturbed when placing the bus bar (102) and tightening the assembly using the shear off nut. The connection assembly ensures a secure connection electrically and mechanically against any external loads.

In an example implementation of the present invention, a transformer of 630 – 990 KVA capacity is tapped at the low voltage side. A 990 KVA rating 500 sq. mm round cables is used for the networking. The current rating is 1600 Amps. A 4 runs bus bar M30 is used. The networking cables are inserted through the heat shrink cable breakout and fixed to the bus bar using the Shear head screws with a force of 40 +/- 2 NM. The bus bar has a dimension of 157 mm in length and 85 mm in width. An O ring is placed on the collet and the plastic lock is placed. The collet is then threaded down the transformer stud. The first end of the busbaris placed on the collet such that the taper surface in the through bore of the bus bar engages with the inclined outer surface of the collet. The shear off nut along with an O ring is placed on the protruding part of the transformer stud to engage with the collet. The shear off nut is tightened to create the necessary torque to secure the assembly. The shear off nut torque was 90 +/- 4.5 NM.

The resultant connection assembly was found to be sturdy against any axial or rotational displacement under external loads. Further, the orientation of the networking cable was not disturbed during the assembly.

In a preferred embodiment, the present invention discloses a connection assembly for a transformer-bus bar connection, in which the connection assembly comprisesa transformer stud with a threaded section; a collet with a threaded central through bore and a conical outer surface, where the threads on the transformer stud and the central bore of the collet are complimentary; and the collet is threaded on the transformer stud; a bus bar which at a first end comprises a through bore with a taper surface, and the taper surface has the same incline as the conical outer surface of the collet with the taper surface and the conical outer surface forming a tight interface when the bus bar is placed over the collet; and the inclination of the interface increases outwardly towards the transformer side; and a shearoff nut to secure the connection assembly, wherein the shearoff nut engages with the collet.According to the invention, the taper angle of the taper surface is in the range of 5to 10 Degree. As per the present invention, the bus bar at a second end comprises a heat shrink cable breakout for connecting to networking cables; and Shear head screws to secure the connection to the networking cables.

In addition, the present invention discloses an O ring placed on the collet and an O ring placed on the shear off nut to provide sealing. Further, the bus bar, the collet, the shear off nut and the Shear head screws are made of Aluminium alloy. An insulation cover is provided to form a protective cover over the connection assembly.

Further, the present invention discloses that the connection assembly is formed by threading the collet on the transformer stud with the wider end of the collet towards the transformer, placing the first end of the bus bar on the collet such that the taper surface in the through bore of the bus bar engages with the inclined outer surface of the collet, placing the shear off nut on the protruding part of the transformer stud to engage with the bus bar, and tightening the shear off nut to secure the assembly.

Certain modifications and improvements will occur to those skilled in the art upon a reading of the foregoing description. The above-mentioned details are provided to serve the purpose of clarifying aspects of the invention and it will be apparent to one skilled in the art that they do not serve to limit the scope of the invention. All modifications and improvements have been deleted herein for the sake of conciseness and readability but are properly within the scope of the present invention. It is understood that the foregoing detailed description is given merely by way of illustration and that modification and variations may be made therein without departing from the spirit and scope of the invention.