FORM 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 SWITCHGEAR
10 ARRANGEMENT WITH REDUCED REPULSION
THRESHOLD AND IMPROVED ARC QUENCHING
2. Applicant(s)
(a) NAME : LARSEN & TOUBRO LIMITED
15 (b) NATIONALITY : An Indian Company.
(c) ADDRESS : L & T House, Ballard Estate, P.O. Box 278,
Mumbai 400 001, State of Maharashtra,
India
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3. PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in
which it is to be performed:
25
2
TECHNICAL FIELD OF THE INVENTION
The present invention relates generally to electric switchgears used in electric
transmission and distribution networks. More particularly, the present invention
provides an arrangement which reduced the repulsion threshold 5 and improved arc
quenching in switchgear threshold.
BACKGROUND AND THE PRIOR ART
Switchgears are used for protection of electric network/circuit and equipments. A
Switchgear consist of a outer enclosure made of insulating material in which
10 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
15 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. Most of
20 switchgears use repulsion type of construction in which a repulsion force
generates between fixed and moving contact because of the direction of flow of
electric current.
It is required to interrupt the fault current rapidly in one or more circuit’s paths
upon the occurrence of an over current in any one circuit path so as to minimize
25 damage to the installation resulting from thermal and mechanical stresses.
Existing available invention uses the arrangement of various components in such a
manner that electric flux generated by the current will be concentrated around
very close to the moving contact (also called the slot motor effect ) with the help
of ferromagnetic material components. Which are arranged in a special manner
3
very close to moving contact with the help of a component called arc shied made
of any ablative material. This increase amount of concentrated flux interacts with
the flux of the fixed contact which is already in opposite direction of the moving
contact flux because of the opposite direction of current flow.
According to the ampere’s force law these opposite flux repels 5 each other and
repulsion force increases proportionally with the amount of flux. Since this
arrangement increases the flux around the moving contact the repulsion force will
also be high depending on the flowing electric current thus achieves a faster
opening of the circuit. so the electromagnetic and mechanical stresses will be less.
10 In these existing systems three different components are used for all three tasks.
Which are flux concentration, arc confinement and ablative action. Sometimes arc
confinement and ablation are combined. At that time also min two components
required. Because of this the ferromagnetic material is not at proper required
closeness with moving contact also the shield is not so close to arc to confine the
15 arc in minimum space and give better ablative action.
EP1956624 disclosed an arrangement having a ferromagnetic material in the form
of strips of U-shape. And another piece of slot motor formed with linear strips.
Which are placed in some two molded material housings. . The final effect is
achieved by combining the two pieces of strips together.
20 US6831536 disclosed an arrangement of slot motor in which a different shape of
housing to hold the ferromagnetic material strips used. The design has narrow and
wide paths. The wide path locks near the fix contact to form loop.
The following points make the present invention significantly better than the prior
art:
25 1. The arrangement shown in above said two prior arts has the open portions
at side in first patent and at side and front directions of arc which are more
prone to come in direct contact with arc. That can cause erosion and loss
of ferromagnetic properties of the material. While the present invention
4
has the open portion at the back side and the direct arc is not allowed to
come in contact.
2. The above said two prior arts don’t have any arrangement to confine the
arc in particular region. Some other arrangement is required to do the
same. Otherwise arc is free to move in any direction and 5 can have reduced
life of other components like braids and shaft because of arc. The present
invention covers the maximum escape areas of arc and allows moving it in
forward direction.
3. The above said two prior arts don’t have any means to increase the
10 pressure inside the arc chamber. Because of this arc takes higher time to
move in de ion plates and higher time to extinguish which causes the faster
erosion of contacts. The present invention has the advantage of ablative
properties of material for faster arc movement.
Both of two prior arts have higher no of components which demands for higher
15 manufacturing cost and higher assembly time compare to present invention.
The present invention provides an arrangement which arranges the ferromagnetic
material, ablative material, and arc shield at an intended closeness with the
moving contact and arc with the help of single component. This arrangement
provides better performance with comparatively less cost addition
20
OBJECTS OF THE INVENTION
A basic object of the present invention is to overcome the
disadvantages/drawbacks of the known art.
25 Another object of the present invention is to provide an arrangement for reducing
repulsion threshold and improving arc quenching in switchgear.
Another object of the present invention is to provide a secondary chamber action
which confines the arc in particular region and allows moving in intended
direction thus stresses on outer housing reduced
5
These and other advantages of the present invention will become readily apparent
from the following detailed description read in conjunction with the
accompanying drawings.
SUMMARY 5 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
10 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.
In an aspect of the present invention, there is provided an arrangement for
reducing repulsion threshold and improving arc quenching in switchgear, said
arrangement comprising;
15 a arc shield component comprises atleast two slot(s)(12 ,13) for
accommodating at least two member(23); said component having side
wall(s)(6, 7, 10, 11) providing support to said member(23) to from an
assembly and inner wall(s)(2, 4, 5, 8, 9) of said component forming a
cavity for movement of a moving contact; back wall(s)(17, 18, 19 ) of said
20 component connecting with a fixed contact(33);
an arc chute assembly connected to said arc shield component for
restricting the arc movement in lateral direction;
wherein said arrangement increases the flux around said moving contact,
therefore increasing the repulsion force to facilitate high speed contact
25 opening with respect to the increasing fault current in said switchgear(s).
Other aspects, advantages, and salient features of the invention will become
apparent to those skilled in the art from the following detailed description, which,
6
taken in conjunction with the annexed drawings, discloses exemplary
embodiments of the invention.
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 5 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, 2 and 3 illustrates the ablative arc shield component of the arrangement.
10 Figure 4 and 5 illustrates the ferromagnetic material component.
Figure 6, 7 and 8 illustrates the assembly of arc shield and ferromagnetic
component.
Figure 9 and 10 illustrates the assembly of arc shield and de ion plates assembly.
Figure 11 and 12 illustrates the sectional view of invented arrangement with
15 various components.
Figure 13 and 14 illustrates the complete switchgear assembly with one side of
outer housing.
Figure 15 illustrates the sectional view of complete switchgear assembly with one
side of outer housing.
20 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.
25 Throughout the drawings, it should be noted that like reference numbers are used
to depict the same or similar elements, features, and structures.
7
DETAILED DESCRIPTION OF THE INVENTION
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 5 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
10 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
15 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.
20 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
25 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.
Accordingly, present invention provides an arrangement which increases the
repulsion force between fixed and moving contacts or reduces the repulsion
8
threshold. At the same time forms a confined chamber for arcing thus improving
arc quenching.
The present invention is a cost effective arrangement to be used in switchgears
mainly in molded case circuit breakers to improve its performance. This
arrangement provides high speed contact opening with respect 5 to the increasing
fault current. This whole arrangement works on the phenomenon of ampere’s
force law about the two current carrying conductors. In this arrangement the force
between conductors increased by increasing flux concentration around conductors
with the help of specially arranged ferromagnetic material components. And arc
10 quenching improved by providing a secondary chamber and ablative properties
with the help of unique components said arc shield.
The component used for holding the ferromagnetic material called arc shield
works as a secondary arc chamber at the time of arcing. This shield confines the
arc movement and allows the arc only to move in one intended direction towards
15 the de-ion plates. The material of arc shield has the ablative properties which
produces high amount of gases when comes in contact with arc. These gases
increases pressure inside the chamber and force the arc to move quickly. Because
of this arrangement the moving contact opens up rapidly as the fault current
crosses the threshold value and forces the arc quickly in the intended direction
20 because of increased pressure. Thus fault current and arc both flows for a very
small period of time. Due to this stresses on the primary chamber (outer housing)
and erosion of fixed and moving contacts reduces thus improved safety of
downstream equipments and increased life of switchgear achieved.
The arrangement is shown in figure (Fig 13 and Fig 14). It consists of a
25 component 1 (Fig 1, 2, 3) which is called arc shield. The component 1 is made of
any type of arc resistant and temperature withstands ablative material. This
component has a unique design which holds components 23 (Fig 4, 5) which is a
ferromagnetic material. The component 23 sits at two places of component 1
touching the surfaces 12 and 13 with the surface 27 (Fig 6, 7, 8). Side walls 6,7,10
9
and 11 provide the side support to component 23 and form the assembly 28. These
side walls also acts as a barriers and prevent the arc movement towards back side
where braids 32 and shaft 30 are fixed (Fig 11, 12). The inner walls 2, 4, 5, 8 and
9 form the cavity where moving contact 31 moves. The back view of component 1
(Fig 2) has the walls 17,18 and 19 which cover the fixed contact 5 33 as shown in
Figs 13,14. The walls 15 and 16 sit inside the arc chute assembly 29 (Fig 9,10 )
and restrict the arc movement in the lateral direction.as shown in Fig 11 the walls
15 and 16 go deep into Deion plates of arc chute assembly 29 and cover them to
form a chamber. It can be seen from the Fig 11 and 12 that the ferromagnetic
10 material 28 is placed very close to moving contact 31 and covers the whole path
of its movement. it concentrate the flux both side of the moving contact in a loop
exactly at the location where the direction of current in fixed contact 33 reverses.
As a result higher amount of repulsion force generated. Also the component 1
covers moving button 35 fixed on contact 31 and fixed button 34 fixed on contact
15 33 and forms a chamber like structure. This chamber has the ablative properties
which produces gases when comes in contact with arc. These gases increase the
pressure inside the chamber and push the arc outside through opening bent which
is towards the Deion plates as the all remaining openings are covered by
component 1. The whole arrangement shown in Fig 11 and 12 sits inside the outer
20 chamber/housing 36 (Fig 13, 14, 15). The fixing of the assembly 28 in outer
chamber 36 is much simpler and time saving comparing to the existing methods.
There is no requirement of any fixing hardware or adhesive materials. The
movement of assembly 28 is arrested by arc chute assembly 29 in one direction
and by the wall 37 of the housing 36 in other direction. Wall 37 is tangential to
25 walls 4, 5, 6 and 7 of assembly 28 and restricts its movement because of slop. The
wall 37 doesn’t allow the assembly 28 to move towards the shaft thus ensures
sufficient clearance between assembly 28 and shaft 30. The movement of
ferromagnetic component 23 is also restricted by wall 37 (Fig 15) and the walls of
component 1. There is no requirement of any additional process for fixing of
30 component 23 inside the component 1. Someone has to just place component 23
inside the component 1 and mount the whole arrangement in outer housing 36.
10
As soon as the current goes up to the specified valued, the repulsion force
between contacts 31 and 33 increases. Due to the higher flux concentration around
contact 31 force is higher compare to existing methods. Because of higher force
contact buttons 34 and 35 start separating rapidly and arc produced. This arc
trapped in a secondary chamber which forces to move it towards 5 the deion plates
by generating gas pressure.so the arc moves quickly in deion plates and get
extinguished.
NOVEL FEATURES:
1. The invention can be used in all kind transmission and distribution switchgears
10 having various size, shapes and current carrying capacities work on the principle
of repulsion force.
2. The arrangement provides higher flux concentration very close to and a proper
path to moving contact so comparatively higher force can be archived.
3. The arrangement can be used for switchgears having any number of
15 poles/phases.
4. The arrangement can be used for switchgears having n- number of current
break system.
5. The arrangement has the secondary chamber action which confines the arc in
particular region and allows moving in intended direction thus stresses on outer
20 housing reduced.
6. The ablation action takes place in very close vicinity of the arc thus the
improved effect of phenomenon achieved.
7. Hardware free and adhesive free fixing of arrangement.
8. The arrangement doesn’t require any secondary process to make it with any
25 switchgear thus reduced cost and assembly time.
11
9. The ferromagnetic material of any shape, size and form like strips , solid etc.
can be used in this arrangement for reduced losses and improved performance.
5
10
15
20
12
WE CLAIM:
1. An arrangement for reducing repulsion threshold and improving arc
quenching in switchgear, said arrangement comprising;
a arc shield component comprises atleast two slot(s)(12 ,13) for
accommodating at least two member(23); said component 5 having side
wall(s)(6, 7, 10, 11) providing support to said member(23) to from an
assembly and inner wall(s)(2, 4, 5, 8, 9) of said component forming a
cavity for movement of a moving contact; back wall(s)(17, 18, 19 ) of said
component connecting with a fixed contact(33);
10 an arc chute assembly connected to said arc shield component for
restricting the arc movement in lateral direction;
wherein said arrangement increases the flux around said moving contact,
therefore increasing the repulsion force to facilitate high speed contact
opening with respect to the increasing fault current in said switchgear(s).
15 2. The arrangement as claimed in claim 1, wherein said member are
ferromagnetic material.
3. The arrangement as claimed in claim 1and claim 2, wherein said
ferromagnetic material concentrating the flux both side of said moving
contact, when current in said fixed contact is reversed, thereby generating
20 repulsion force for high speed contact opening(s).
4. The arrangement as claimed in claim 1 and claim 3, wherein repulsion
force increased between said moving contact and said fixed contact, when
current increased above a specified value causing high flux concentration
around said moving contact, thereby generating a higher force.
25 5. The arrangement as claimed in claim 4, wherein said secondary chamber
facilitate movement of arc towards the deion plate(s) for quenching , when
said force button(s)(34, 35 ) separating rapidly due to increased force,
therefore producing arc in said switch gear(s).
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6. The arrangement as claimed in claim 1, wherein said moving contact and
said fixed contact comprises a force button (34, 35) connecting to said
component forming a chambered structure.
7. The arrangement as claimed in claim 1, wherein said chambered structure
increases pressure and pushing arc outside of said 5 chamber through an
opening bent towards a deion plate(s), during arcing
8. The arrangement as claimed in claim 1, wherein arc quenching is
improved by providing a secondary chamber by connecting the wall(15, 16
) of said aid component to said deion plate(s) of arc chute assembly
9. The arrangement as claimed in claim 1, wherein movement of said
component (28)is restricted by said arc chute assembly (29) in one
direction and by a wall (37) of the housing of switch gear (36) in other
direction.
10. The arrangement as claimed in claim 1, wherein side wall(s)(6, 7, 10, 11)
15 preventing the arc movement towards a braids (32) and a shaft (30) of said
switch gear(s).
11. The arrangement as claimed in claim 1, wherein said component is made
up of an arc resistant and temperature withstands ablative material.