F O R M 2
THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)
1. Title of the invention: A CONTACT ARRANGEMENT FOR REDUCING EROSIONS OF CONTACT BUTTONS IN SWITCHGEARS
2. Applicant(s):

(a) NAME : LARSEN & TOUBRO LIMITED
(b) NATIONALITY : An Indian Company
(c) ADDRESS : L & T House, Ballard Estate, Mumbai
400 001, State of Maharashtra, India
3. PREAMBLE TO THE DESCRIPTION
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 an arrangement for substantially reducing erosions of contact buttons during making and/or breaking operations in switchgears which are used in electric transmission and distribution networks. More particularly, the invention is concerned about providing an arrangement in the contacts- of switchgears which ameliorates erosions of the contact buttons thereby providing substantial amount of cost saving. Further the invention relates to an arrangement by which the contact buttons in switchgears are saved both in normal and abnormal condition during making/breaking operation. Further the arrangement of the present invention can be used in a contact system for use in transmission and distribution networks.
BACKGROUND OF THE INVENTION AND PRIOR ART
A Switchgear consist of a outer enclosure made of insulating material in which switching (make/break) takes place, a current path which is connected to the main supply line and makes/breaks electric supply, a mechanism which may be a combination of a number of mechanical links and springs or may be any arrangement which stores energy and releases in mechanical form when required. The current path/conductor of Circuit Breakers is made of highly electric conductive materials to reduce the losses. The current path has a fixed contact and a moving contact which moves . to make/break (Close/open) the

circuit. Due to the breaking of circuit an arc generates because of voltage gradient between fixed and moving contacts. This generated arc erodes fixed and moving contacts and enclosure also. This causes reduced operational life of switchgears.
Switchgear interrupts the high current during abnormal condition. Generally, switchgears comprise of a fixed arm and a moving arm made of conductive material to carry the current. The fixed and moving arm, each consists of silver buttons as the mating or the contacting surface. The silver buttons are exposed to high short circuit current during faults which results in erosion of these buttons.
The present inventors have been into studies of existing prior art but have not found any prior art which provides an idea of a flexible structure providing protection to the contact buttons in molded case circuit breakers(MCCBs). Some teachings on fixed arcing contacts are available in the prior art, however, those have been found not to be effective in saving the contact buttons.
EP 1192628 Bl discloses arcing contact which is operable through a mechanism which makes intermediate contact and arcing contact. The arcing contact mentioned here takes the help of a spring based mechanism for shifting the position of arc from buttons contact position to arcing contact where the final arcing happens. The mechanism

spring applies a force on the moving arm so that the contact position shifts to another position on the fixed contact.
In view of the above, it has been found by the present inventors that there still exists a need and space for providing with an arrangement in the contacts of switchgears which ameliorates erosions of the contact buttons thereby providing substantial amount of cost saving. It has been found that a unique structural component when provide in the contact region of the switchgear provides shifting the place of initiation of the arc while avoiding any other mechanical parts. The inventors have also achieved faster opening of the contact as compared to the prior art because of the absence of time delay.
OBJECTS OF THE INVENTION
One object of the present invention is to overcome the disadvantages / drawbacks of the prior art.
A basic object of the present invention is to provide an arrangement for substantially reducing erosions of contact buttons during making and/or breaking operations in switchgears.
Another object of the present invention is to increase the longevity of the contacts in switchgears.

Another object of the present invention is to provide a cost effective making/breaking operations.
These and other advantages of the present invention will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings.
SUMMARY OF THE INVENTION
The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the present invention. It is not intended to identify the key/critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concept of the invention in a simplified form as a prelude to a more detailed description of the invention presented later.
According to one of the aspect of the present invention
there is provided an arrangement for reducing contact
button erosion in switchgears, said arrangement
comprising:
a fixed contact and a moving contact both having contact
buttons;
a pin means provided on said moving contact wherein said
pin means defines a primary arcing contact;
a structural means located on said fixed contact and
being held by another component means wherein said

structural means defines a secondary arcing contact;
wherein
said primary arcing contact is in contact slidably with
said secondary arcing contact while making/breaking
operation of the switchgear during a normal/abnormal
condition and wherein
arcing takes place at the contact point of said primary
arcing contact and said secondary arcing contact.
According to another aspect of the present invention
there is provided a contact system comprising an
arrangement as described herein above for reducing
contact button erosion in switchgears, said system
comprising:
a fixed contact and a moving contact both having contact
buttons;
a pin means provided on said moving contact wherein said
pin means defines a primary arcing contact;
a structural means located on said fixed contact and
being held by another component means wherein said
structural means defines a secondary arcing contact;
wherein
said primary arcing contact is in contact slidably with
said secondary arcing contact while making/breaking
operation of the switchgear during a normal/abnormal
condition and wherein
arcing takes place at the contact point of said primary
arcing contact and said secondary arcing contact.

According to another aspect of the present invention
there is provided a moulded case circuit breaker
comprising contact system as described herein above
wherein said contact system comprising arrangement as
described herein above comprising:
a fixed contact and a moving contact both having contact
buttons;
a pin means provided on said moving contact wherein said
pin means defines a primary arcing contact;
a structural means located on said fixed contact and
being held by another component means wherein said
structural means defines a secondary arcing contact;
wherein
said primary arcing contact is in contact slidably with
said secondary arcing contact while making/breaking
operation of the switchgear during a normal/abnormal
condition and wherein
arcing takes place at the contact point of said primary
arcing contact and said secondary arcing contact.
According to another aspect of the present invention there is provided a switchgear system comprising one or more moulded case circuit breaker comprising contact system as described herein above wherein said contact system comprising arrangement as described herein above comprising:
a fixed contact and a moving contact both having contact buttons;

a pin means provided on said moving contact wherein said
pin means defines a primary arcing contact;
a structural means located on said fixed contact and
being held by another component means wherein said
structural means defines a secondary arcing contact;
wherein
said primary arcing contact is in contact slidably with
said secondary arcing contact while making/breaking
operation of the switchgear during a normal/abnormal
condition and wherein
arcing takes place at the contact point of said primary
arcing contact and said secondary arcing contact.
Other aspects/ advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention.
DETAILED DESCRIPTION OF THE INVENTION
Conventionally literature does mention arcing contacts which are rigid in structure and these contacts come into picture only after an application of force from an external agent other than the contact system i.e. a mechanism. A mechanism which opens the contact itself shifts the contact arm to such a position where only the arcing contacts mate during making and breaking.

This arrangement uses electromagnetic repulsive force for faster breaking of a circuit at a higher current. The contact repels when the current reaches a threshold value thus initiating an arc. The place of initiation of the arc has been changed in the present invention while avoiding any mechanical parts for achieving the same. The faster opening of the contact as compared to prior arts is also achieved in this arrangement because of the absence of time delay induced by the mechanism.
The present invention thus in its one embodiment describes an arrangement for reducing contact button erosion in switchgears. Such arrangement saves the life of the contact button which is generally made of silver and is the most costly material used in a switchgear. The present invention aiming in improving the longevity of the contact buttons also provide for a cost effective making/breaking operation during normal/abnormal conditions. The arrangement comprises a fixed contact and a moving contact which are provided with contact buttons. Normally contact buttons contact buttons are made of silver and in the present invention the contact buttons are also made of silver. Any other expensive conductive metal can be used for making contact buttons and a person skilled in the art may use the same arrangement as described in the present invention for ameliorating erosion of the contact buttons. Such variations would be comprised well within the scope of the present invention

and will be considered as not being a departure from the present scope of the claims.
The moving contact as described above is further provided with a pin means also referred as moving contact pin which acts as primary arcing contact in the present arrangement. In operation the primary arcing contact is in co-operation with a structural means located on the fixed contact and being held by another component means which provides arc runner and magnetic shield both. The structural means define the secondary arcing contact and provides surface for the primary contact to slide while making/breaking operation of the switchgear during a normal/abnormal condition. It is required to be mentioned here that the above arrangement provides shifting of the place of initiation of arc from between the two contact buttons of the fixed and moving contacts to a contact point between the primary arcing contact and said secondary arcing contact.
The structural means as described herein above is in the form of a flexible conducting structure fixed to the fixed contact and have a spring back action in the fixed contact. The said structural means is provided a substantial "S" shaped profile with its substantial horizontal part resting on the fixed contact and substantial vertical part climbing along the deion plates upto a certain height with certain portion of its curvature being disposed in between two deion plates.

Further the structural means comprises a substantially rectangular shaped window profile which provides frames as surfaces for the moving contact pin to be in contact with the secondary arcing contact and slide. It is to be appreciated that though the present inventors have provided the structural means with a substantial "S" shaped profile having some predetermined curvature to meet the allowable space constraints and/or any design limitations and be in contact with the primary contact during operation, a person skilled in the art may opt for some minor variations in the profile of the structure and achieve the same result as in the present invention. Such variation will also be considered well within the scope of the present invention.
In another embodiment the present invention describes a contact system comprising the arrangement as described herein above for reducing contact button erosion in switchgears. It is considered that a person skilled in the art would very well be aware of components/constructional features of a contact system and therefore the same is not required to be elaborated herein.
In a further embodiment the present invention describes a moulded case circuit breaker (MCCB) which comprises a contact system provided with the arrangement as described herein above. It is considered that a person skilled in the art would very well be aware of

components/constructional features of a MCCB and therefore the same is not required to be elaborated herein. As regards, providing the arrangement which has been described in this document in a MCCB, the setup and configuration will be known to a person skilled in the art and therefore no further elaboration is required.
In another embodiment of the present invention the moulded case circuit breaker comprising a contact system comprising the arrangement as described herein forms one of the protection equipments in a switchgear system. Such design setup of a switchgear system comprising the arrangement of the present invention can be understood by the person skilled in the field and he can derive such switchgear systems well into practical applications with description of the arrangement as provided herein and his knowledge skills. Further elaboration of a switchgear system with conventionally known parts/components is not required.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The following drawings are illustrative of particular examples for enabling methods of the present invention, are descriptive of some of the methods, and are not intended to limit the scope of the invention. The drawings are not to scale (unless so stated) and are intended for use in conjunction with the explanations in the following detailed description.

Figure 1 illustrates the arrangement and the contact system of the present invention.
Figure 2 illustrates full view of Configuration 1
Figure 3 illustrates cross sectional view of Configuration 1
Figure 4 illustrates fixing of the structural means using arc runner.
Figure 5 illustrates the contact system in Configuration 2 when the breaker is carrying the rated current.
Figure 6 illustrates the contact system in Configuration 2 during break operation.
Persons skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and may have not been drawn to scale. For example, the dimensions of some of the elements in the figure may be exaggerated relative to other elements to help to improve understanding of various exemplary embodiments of the present disclosure.
Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures.

DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention as defined by the claims and their equivalents. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope and spirit of the invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.
The terms and words used in the following description and claims are not limited to the bibliographical meanings, but/ are merely used by the inventor to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration purpose only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.
It is to be understood that the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

By the term "substantially" it is meant that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those of skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide.
Figure 1 describes the arrangement of the contact system used in this invention. Figure 1 shows a moving contact arm (2) and fixed contact arm (1), moving contact button (4), fixed contact button (5), Deion plate (8) for attracting the arc initiated during making and breaking operation. The arc runner and magnetic shield (3) has been implemented in a single component. The S-shaped Structure (6) is held on the fixed contact by using this arc runner cum magnetic shield. Moving Contact pin (7) is fixed with moving contact which acts as an arcing contact. Moving contact is hinged at a position by the use of a moving contact hinge pin (9).
The object behind this invention is saving silver which is generally the costliest part in a molded case circuit breaker.
Arcing contacts have been implemented by use of a conductive pin fixed (7) in the moving contact and a S shaped secondary contact in the form of a flexible

conducting structure having a spring back action in the fixed contact. There are two configurations possible in this arrangement.
Figure 2 describes the first configuration when the moving contact button and the fixed contact button as well as the moving arm contact pin is in direct contact with the S shaped arcing contact.
This provides the current two parallel paths for its conduction. While making/breaking at a normal/abnormal condition it is the S shaped structure which makes first and breaks last. The Moving contact conductive pin slides over the S-shaped structure because of its flexible nature. The spring-back characteristic of S-shaped contact helps the structure regain its original position. Arcing takes place at the point of contact of S shaped structure and the moving contact pin instead of moving contact and fixed contact button. In this configuration even the rated current is carried by the arcing contacts.
In configuration 2 shown in fig (5) the rated current is not carried by the arcing contact. While breaking in this configuration as the moving contact repels, the contact between moving contact pin and S- shaped structure takes place initiating the arc at this surface and vice versa during making.

WE CLAIM:
1. An arrangement for reducing contact button erosion
in switchgears, said arrangement comprising:
a fixed contact and a moving contact both having
contact buttons;
a pin means provided on said moving contact wherein
said pin means defines a primary arcing contact;
a structural means located on said fixed contact and
being held by another component means wherein said
structural means defines a secondary arcing contact;
wherein
said primary arcing contact is in contact slidably
with said secondary arcing contact while
making/breaking operation of the switchgear during a
normal/abnormal condition and wherein
arcing takes place at the contact point of said
primary arcing contact and said secondary arcing
contact.
2. Arrangement as claimed in claim 1 wherein said pin
means of the moving contact projects out of said
moving contact on both sides to remain slidably in
contact with said structural means.

3. Arrangement as claimed in claim 1 wherein said structural means is substantially S shaped profile.
4. Arrangement as claimed in claim 1 or 3 wherein said structural means comprising a substantial horizontal part resting on the fixed contact and substantial vertical part climbing along the deion plates upto a certain height with certain portion of its curvature being disposed in between two deion plates.
5. Arrangement as claimed in claim 1 or 3 wherein said structural means comprising a substantially rectangular window along its curvature allowing contact of the said moving contact pin and slidable movement of said primary arcing contact over the secondary arcing contact.
6. Arrangement as claimed in claim 1 or 3 wherein said structural means is a flexible conductive structure.
7. Arrangement as claimed in claim 1 further comprising a single component acting as arc runner and magnetic shield.
8. A contact system comprising an arrangement as claimed in claims 1 to 7 for reducing contact button erosion in switchgears, said system comprising:

a fixed contact and a moving contact both having
contact buttons;
a pin means provided on said moving contact wherein
said pin means defines a primary arcing contact;
a structural means located on said fixed contact and
being held by another component means wherein said
structural means defines a secondary arcing contact;
wherein
said primary arcing contact is in contact slidably
with said secondary arcing contact while
making/breaking operation of the switchgear during a
normal/abnormal condition and wherein
arcing takes place at the contact point of said
primary arcing contact and said secondary arcing
contact.
9. A moulded case circuit breaker comprising contact system as claimed in claim 8 comprising arrangement as claimed in claims 1 to 7, said breaker comprising:
a fixed contact and a moving contact both having
contact buttons;
a pin means provided on said moving contact wherein
said pin means defines a primary arcing contact;
a structural means located on said fixed contact and
being held by another component means wherein said

structural means defines a secondary arcing contact;
wherein
said primary arcing contact is in contact slidably
with said secondary arcing contact while
making/breaking operation of the switchgear during a
normal/abnormal condition and wherein
arcing takes place at the contact point of said
primary arcing contact and said secondary arcing
contact.
10. A switchgear system comprising one or more moulded case circuit breaker as claimed in claim 9 comprising contact system as claimed in claim 8 comprising arrangement as claimed in claims 1 to 7, said switchgear system comprising:
a fixed contact and a moving contact both having
contact buttons;
a pin means provided on said moving contact wherein
said pin means defines a primary arcing contact;
a structural means located on said fixed contact and
being held by another component means wherein said
structural means defines a secondary arcing contact;
wherein
said primary arcing contact is in contact slidably
with said secondary arcing contact while
making/breaking operation of the switchgear during a
normal/abnormal condition and wherein

arcing takes place at the contact point of said primary arcing contact and said secondary arcing contact.