FORM 2


THE PATENTS ACT, 1970
(39 of 1970)
As amended by the Patents (Amendment) Act, 2005
&
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2006
COMPLETE SPECIFICATION (See section 10 and rule 13)
TITLE OF THE INVENTION
A busbar and a method of manufacturing the same
APPLICANTS
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company
Inventor
Ghosh Baidyanath, Crompton Greaves Limited, S2, Switchgear Division, A-3 MIDC, Ambad, Nashik 422010, Maharashtra, India, an Indian National
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the nature of this invention and the manner in which it is to be performed:


FIELD OF THE INVENTION
This invention relates to a busbar and a method of manufacturing the same.
BACKGROUND OF THE INVENTION
Busbars are electrical connectors used in electrical applications / electrical industry to electrically connect electrical components, devices or equipments. A busbar comprises a conductor usually copper or aluminium and an electrical insulation provided on the conductor, usually a PVC (polyvinyl chloride) sleeve. A busbar may be straight or bent and is made by inserting the PVC sleeve over the conductor and heat shrinking the PVC sleeve on the conductor. Heat shrinking is generally carried out in an electric oven. Due to thickness variations of the sleeve along the length thereof and non-uniform heat in the oven, a uniform and tight fit or skin fit of the sleeve along the entire conductor length is rather difficult. As a result, the insulation properties of the busbar are reduced. Air also gets trapped between the conductor and the sleeve during insertion of the sleeve over the conductor, especially at the bents or corners of bent bus bars and during the heat shrinking operation the sleeve bulges out at the locations of air entrapment. During working of
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the busbar, the air gets heated up due to development of heat in the conductor as a result of flow of current and the insulation develops cracks at such locations and often burst open leading to insulation failure. As a result, the life of the busbar is reduced. In order to remove entrapped air, secondary operation is required by way of pressing out the air bubbles. This is cumbersome and difficult to carry out and inspite of this, air still gets trapped. Due to thickness variations and climensional inaccuracies, the ends of the sleeve insulation are not often uniform. Therefore, while joining the busbars it will become necessary to straighten the ends by cutting. This is also inconvenient and cumbersome to carry out.
OBJECTS OF THE INVENTION
An object of the invention is to provide a busbar which has uniform and even adhesion between the insulation and conductor throughout so as to improve the insulation properties of the busbar.
Another object of the invention is to provide a busbar which avoids entrapment of air between the conductor and the insulation and increases the life of the insulation.
Another object of the invention is to provide a busbar which is simple in construction.
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Another object of the invention is to provide a method of making a busbar, which method ensures even and uniform adhesion between the insulation and conductor throughout so as to improve the insulation properties of the busbar.
Another object of the invention is to provide a method of making a busbar which method avoids entrapment of air between the conductor and the insulation and increases the life of the insulation.
Another object of the invention is to provide a method of making a busbar which method is simple and easy and convenient to carry out.
DETAILED DESCRIPTION OF THE INVENTION According to the invention there is provided a busbar comprising a conductor and an electrical insulation comprising a flame retardant low smoke (FRLS) thermoplastic material coating of 1.00 to 1.25 mm thickness applied on the conductor.
According to the invention there is also provided a method making a busbar comprising degreasing a conductor with dilute hydrochloric acid and applying a coating of 1.00 to 1.25 mm thickness of a flame retardant
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low smoke (FRLS) thermoplastic material on the surface of the conductor after preheating the conductor to the melting point of the flame retardant low smoke thermoplastic material and curing the coated conductor.
Preferably, the flame retardant low smoke (FRLS) thermoplastic material comprises FRLS grade SPL-FRLA-BW and SPL-PVC Type A and the conductor is preheated to 300 to 350°C. Preferably, the conductor comprises aluminium or copper and the coating thickness is 1 mm.
The conductors are degreased by dipping them in dilute hydrochloric acid and the conductors are preheated to the melting point of the flame retardant low smoke thermoplastic material, preferably, in an electric oven. The preheated conductors are coated with the flame retardant low smoke thermoplastic material by applying the material on the preheated conductor surface. Due to degreasing, the conductor surface is free from all foreign particles and smooth and clean and is activated. Due to preheating of the conductors to the melting point of the flame retardant low smoke thermoplastic material, the material melts and adheres to the surface of the busbar evenly and uniformly so as to give a uniform coating of the insulation on the surface of the conductor and improve the electrical properties of the busbar. During coating there is no possibility of air entrapment and air entrapment is avoided, especially at the bents or
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corners of bent bus bars. Therefore, development of cracks in the coating or bulging of the coating is prevented and life of the busbar is increased. There is no need for any secondary operation to remove the air entrapment The busbar is simple in construction and it is easy and convenient to make it. The ends of the insulation coating will remain uniform. Therefore, joining of the busbar is easy and convenient. The method of the invention is also simple and easy and convenient to carry out. The coated busbars are cured by leaving them in the ambient conditions for 1 to 2 hrs.
Figs 1 and 2 of the accompanying drawings show isometric views of a straight and a bent busbar of the invention, respectively. The busbar 1 of Fig 1 comprises a conductor 2 and a flame retardant low smoke thermoplastic material insulation coating 3 on the conductor. Mounting holes of the bulbar are marked 4. The busbar 5 of Fig 2 comprises a conductor 6 ancl a flame retardant low smoke thermoplastic material insulation coating 7 on the conductor. Mounting holes of the busbar are marked 8.
Comparative studies were carried out with busbars comprising copper conductors and PVC sleeve insulation and flame retardant low smoke (FRLS) thermoplastic material grade SPL-FRLA-BW and SPL-PVC
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Type A insulation according to the invention. The test results were as
shown in the following Table 1:

Test Parameters Busbar with PVC insulation Busbar with FRLS
thermoplastic
insulation
Insulation thickness 1 mm/ side 1 mm/ side
Insulation test by 2000 V DC Megger 1 OOGega ohms 1 OOGega ohms
Di- Electric test at 05 kV / 60 sec conducted on 50kV / 25 mA High Voltage test set up Withstood OK, leakage current less thanlOmA Withstood OK, leakage current less than 10 mA
Di- Electric test at 10 kV / 60 sec conducted on 50kV / 25 mA High Voltage test set up Withstood OK? leakage current less than 10mA Withstood OK, leakage current less than 10mA
Di- Electric test at 15 kV / 60 sec conducted on 50kV / 25 mA High Voltage test set up Withstood OK, leakage current less than 10 mA Withstood OK, leakage current less than 10 mA
Di- Electric test at 16 kV / 60 sec conducted on 50kV / 25 mA High Voltage test set up Withstood OK, leakage current less thanlOmA Withstood OK, leakage current less thanlO mA
Breakdown voltage 23 kV 24 kV
Table 1 shows that the electrical properties of the busbars of PVC insulation and FRLS thermoplastic insulation were comparable. Table 1 also shows that the breakdown voltage of the busbar of the invention was in fact better.
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We claim :
1) A busbar comprising a conductor and an electrical insulation
comprising a flame retardant low smoke (FRLS) thermoplastic material
coating of 1.00 to 1.25 mm thickness applied on the conductor.
2) The busbar as claimed in claim 1, wherein the conductor comprises aluminium or copper and the flame retardant low smoke (FRLS) thermoplastic material coating comprises FRLS grade SPL-FRLA-BW and SPL-PVC Type A.
3) The busbar as claimed in claim 1 or 2, wherein the coating thickness is 1 mm.
4) The busbar as claimed in anyone of claims 1 to 3, which is straight or bent.
5) A method making a busbar comprising degreasing a conductor with dilute hydrochloric acid and applying a coating of 1.00 to 1.25 mm thickness of a flame retardant low smoke (FRLS) thermoplastic material on the surface of the conductor after preheating the conductor to the melting point of the flame retardant low smoke thermoplastic material and curing the coated conductor.
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6) The method as claimed in claim 5, wherein the conductor is aluminium or copper and is coated with FRLS grade SPL-FRLA-BW and SPL-PVC Type A material after preheating the conductor to 300 to 350°C.
7) The method as claimed in claim 5 or 6, wherein the flame retardant low smoke thermoplastic material coating thickness is 1 mm.
8) The method as claimed in anyone of claims 5 to 7, wherein the conductor is straight or bent.
Dated this 6th day of March 2009

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