FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
As amended by the Patents (Amendment) Act, 2005
AND The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2005
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION
Pre-insertion Resistor in circuit breakers
APPLICANTS
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company
INVENTOR
RAO SUDHENDRA of Crompton Greaves Ltd, Switchgear R&D, A3 MTDC 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 the field of circuit breakers.
Parti cuiariy, this invention relates to the field of'mteirupters in circuit breakers.
Still particularly, this invention relates to pre-insertion resistors in circuit breakers.
Background of the Invention:
Breakers used for high voltage systems like 400kV and above are provided with a pre-insertion resistor (PIR) in order to damp the inrush currents which occur when the line is switched on. These pre-insertion resistors are kept in parallel to the main interrupting unit and mechanically arranged in such a way that when the breaker is closed on-line, the pre-insertion resistor comes in contact earlier than the interrupting unit. This pre-insertion resistor damps the inrush current by dissipating the heat in the resistors.
This pre insertion resistor is not needed after the main contact touches as the stable current now will flow from the interrupting unit due to lOW resistance. This makes PIR contact useless to keep in contact.
During opening the pre insertion resistor has to be opened first as it does not have any capacity to break the current.

Objects of the Invention:
An object of the invention is to provide electrical and mechanical shock absorbing feature to main interrupter contacts of a circuit breaker.
Another object of the invention is to provide a mechanism which closes before main interrupter contacts.
Yet another object of the invention is to provide a mechanism which opens before the interrupting unit in order to avoid malfunction in breaker in case of arc in PIR.
Still another object of the invention is to provide a mechanism which closes first interrupter contacts and immediately opens once main interrupter contacts open.
An additional object of the invention is to provide a mechanism which avoids inrush of current and bouncing.
Yet an additional object of the invention is to prevent damage to the main interrupting unit and contacts by dissipating heat through a pre-resistor before the main interrupting unit is engaged.
Prior Art:
CA1113140 describes the Design of PIR operating in parallel with main interrupter but all in same chamber. Here, in main chamber the disc are exposed to hot gases too during arc interruption. This may damage the disc or reduce its life.

The working principle of CA1113140 is that PIR contact are placed in little advance of the main contact. This enables it to close first during closing operation before the main contacts. As the stroke comes to end these PIR contacts stops and remaining stroke is used to compress the spring inside. Here in closed condition the PIR still remains in closed condition. During opening since the overlap in PIR contact is less than main contact it opens first and then main contact opens. At the end of opening operation there is some arrangement which pushes the contact a little so as to achieve the initial condition.
The arrangement as described in CA1113140 uses some type of cam and leaf spring arrangement. This makes a more complexity in design. Also assembly of such components in the same chamber makes it more difficult. Reliability of such design also gets affected as PIR contacts, discs, are assembled in the same chamber where their lot of arcing activity going on. The high temperature gases can affect the performance of the springs; hence affecting performance of PIR.
Summary of the Invention:
According to this invention, there is provided a pre-insertion resistor mechanism adapted to damp motion of a parallely placed main interrupter actuated by a primary actuating shaft, said mechanism being operated by said primary actuating shaft, and said mechanism comprises:
a. first shaft which includes a telescopic shaft adapted to telescope in and out
of said first shaft;
b, moving contact adapted to be placed at the operative outer tip of said
telescopic shaft;

c. stationary contact adapted to be placed in a spaced apart configuration from,
but collinear with said moving contact;
d. deformable rhombus means adapted to control the movement of said moving
contact, said deformable rhombus comprising:
e. pair of long links placed adjacent each other with a first joint between each
other;
f. pair of short links placed adjacent each other with a second joint between
each other;
g. spring adapted to be placed between third joint and fourth joint of said
deformable rhombus between said pair of long links and said pair of short
links;
h. thereby forming a toggle mechanism to toggle the links in a first operative horizontal direction and then in a second operative horizontal direction and finally again in the first operative vertical direction under the influence of said spring; and
i. secondary actuating shaft, placed parallel to said first shaft, adapted to translate motion of said primary actuating shaft towards actuating said deformable rhombus.
Typically, said secondary actuating shaft includes said first joint at operative distal. end of said secondary actuating shaft, thereby attaching one end of said deformable rhombus means i.e. attaching one end of said long links to secondary actuating shaft.
Typically said secondary actuating shaft includes said second joint at an operative distal end of said moving contact, thereby attaching other end of said deformable rhombus means i.e. attaching one end of said short links to said moving contact.

Typically, said mechanism includes angle restrictor means adapted to be placed at said first joint, between said pair of long links, adapted to restrict the movement of the deformable rhombus at its first joint.
Typically, said mechanism includes means to actuate said rhombus links in toggle condition so as to loosen the contact once main contact is made.
Typically, said mechanism includes a stopper arrangement adapted to bring toggled condition of said deformable rhombus to its initial condition.
Brief Description of the Accompanying Drawings:
The invention will now be described in relation to the accompanying drawings, in which:
Figures 1 and 2 illustrate layout of main interrupter with pre-insertion resistor
(PIR);
Figure 3 illustrates a schematic of the PIR; and
Figures 4 to 16 illustrate various stages of opening and closing of PIR.
Detailed Description of the Accompanying Drawings:
According to this invention, there is provided a pre-insertion resistor adapted to damp motion of a parallely placed main interrupter. Typically, main interrupter

includes a moving contact adapted to mate with a stationary contact in an operative horizontal fashion. The movement of the main interrupter is actuated by means of a primary actuator shaft (110) suitably connected to said moving contact.
Figures 1 and 2 illustrate layout of main interrupter (100) with pre-insertion resistor (PIR) (200);
Figure 3 illustrates a schematic of the PIR (100); and
Figures 4 to 16 illustrate various stages of opening and closing of PIR.
Typically, the pre-insertion resistor of this invention is adapted to be placed operatively above said main interrupter. The pre-insertion resistor is adapted to be actuated by said primary actuator shaft.
In accordance with an embodiment of this invention, there is provided a first shaft (6) which includes a telescopic shaft (5) adapted to telescope in and out of said first shaft. Typically, said first shaft acts as a stopper for movement of said telescopic shaft.
In accordance with another embodiment of this invention, there is provided a moving contact (4) adapted to be placed at the operative outer tip of said telescopic shaft.
In accordance with yet another embodiment of this invention, there is provided a stationary contact (8) adapted to be placed in a spaced apart configuration from, but collinear with said moving contact.

In accordance with still another embodiment of this invention, there is provided a deformable rhombus means adapted to control the movement of said moving contact.
Typically, said deformable rhombus means includes a pair of long links (2) placed adjacent each other with a first joint between each other.
Typically, said deformable rhombus means includes a pair of short links (3) placed adjacent each other with a second joint between each other.
In accordance with an additional embodiment of this invention, there is provided a secondary actuating shaft (1) adapted to translate motion of said primary actuating means towards actuating said deformable rhombus. Typically, said secondary actuating shaft is located parallel to said first shaft.
In accordance with yet an additional embodiment of this invention, there is provided a spring (7) adapted to be placed between third joint and fourth joint of said deformable rhombus i.e. between said pair of long links and said pair of short links.
Typically, said first joint is at an operative distal end of said secondary actuating shaft, thereby attaching one end of said deformable rhombus means i.e. attaching one end of said long links to secondary actuating shaft.

Typically, said second joint is at an operative distal end of said moving contact, thereby attaching other end of said deformable rhombus means i.e. attaching one end of said short links to said moving contact.
In accordance with yet another additional embodiment of this invention, there is provided an angle restrictor (9) adapted to be placed at said first joint, between said pair of long links, adapted to restrict the movement of the deformable rhombus at its first joint.
Figure 4 shows start of closing operation. As the primary actuator shaft moves to operate the main interrupter, simultaneously, the secondary actuator shaft is actuated. The tension in the spring, at this point of time is Tl.
Figure 5 shows middle of closing operation. The telescopic shaft telescopes out of said first shaft. The tension in the spring is still Tl, as the deformable rhombus maintains its stance.
Figure 6 shows the moving contact in touching condition with stationary contact, i.e. in closed condition. The mechanism is still moving in the right direction pressing the contacts together. The tension in the spring is still Tl, as the deformable rhombus maintains its stance.
Figure 7 shows that as mechanism moves forward towards right and since contacts have touched each other, the links, and hence, the deformable rhombus gets deformed, as shown. This causes the joints of short links moved away from each other and causing the spring to expand. The tension in the spring is now T2.

Figure 8 shows that the short links are deformed such that they are vertical and the PIR mechanism stroke is just reaching the end. The mechanism moves the secondary actuating shaft a little further so that the short links are toggled. The tension in the spring is now T3.
The mechanism stops after the short link position is toggled. The spring which is now expanded presses these short links a little more towards right so that contact between the moving contact and stationary contact is made. The angle restrictor prevents the angle formed by the connected long links at the first joint to reduce, thereby preventing further deformation of the deformable rhombus.
After this instance, the main interrupter contacts make contact. Their impact is controlled due to the PIR, as the PIR contacts absorb the shock lent by the primary-actuating mechanism.
The PIR contact can be removed from circuit which is achieved as shown in figure 8. The tension in the spring is releases, thus changing from T3 to Tl, at this instance.
Now next challenge is to achieve the same condition at the end of opening i.e. it should be ready to close once again. This is achieved as shown below.
Figure 9 illustrates the start of the retracting mechanism of the PIR. The mechanism is moving towards left and the moving contact which has already separated will move with it towards left The tension in the spring is Tl.

Figure 10 shows the OIT in middle of closing operation. The tension in the spring is Tl. The contacts are away from each other.
Figure 11 shows the opening operation where telescopic shaft is telescoped in the first shaft. The deformable rhombus is still in its deformed condition. The tension in the spring is Tl.
Figure 12 shows that the moving contact is stopped by the telescopic shaft hitting the first shaft. Here, the mechanism continues to move towards left. This will cause the link to expand against the spring. The tension in the spring is still Tl.
Figure 1 shows that the link is beginning to expand against the spring. The tension in the spring is now T2.
Figure 2 showsanded to its maximum, with spring tension as T3. The mechanism is about to end its stroke. that the link is now vertical and about to cross dead center. Spring is now exp
Figure 3 shows that the mechanism has stopped and as link position gets toggled the spring pushes back the link towards right. Hence the initial position is achieved. The tension in the spring is renewed to Tl.
Since at the start of opening the gap is present between the two contacts this PIR has already opened before the main contacts of the interrupter has started to move. Hence this will ensure the gap in PIR will always be higher than the main contacts thus avoiding arcing.

The working principle of the current invention is that during the closing operation of the pre-insertion resistor (PIR), contact will close first due to smaller gap between the PIR chamber contacts than main (interrupter) contacts. Once the PIR contact gets closed, the spring is expanded bringing the two small links to vertical condition. As the main contacts touches this links than get toggled and the PIR contacts opens as spring gets released. Hence, in closed condition, PIR contacts get opened. Hence, during opening operation, the gap between PIR contacts will always be more as it has already opened at the end of closing.
The current invention uses links and a tension/compression spring. The assembly is also very easy as it is done in separate chamber and components are easy to manufacture and assemble. There is no question of hot gases and temperature effect for springs; hence, performance will not be affected by arcing.

We claim,
1. A pre-insertion resistor mechanism adapted to damp motion of a parallely placed main interrupter actuated by a primary actuating shaft, said mechanism being operated by said primary actuating shaft, and said mechanism comprising:
a. first shaft which includes a telescopic shaft adapted to telescope in and out
of said first shaft;
b. moving contact adapted to be placed at the operative outer tip of said
telescopic shaft;
c. stationary contact adapted to be placed in a spaced apart configuration from,
but collinear with said moving contact;
d. deformable rhombus means adapted to control the movement of said moving
contact, said deformable rhombus comprising:
e. pair of Jong links placed adjacent each other with a first joint between each
other;
f. pair of short links placed adjacent each other with a second joint between
each other;
g. spring adapted to be placed between third joint and fourth joint of said
deformable rhombus between said pair of long links and said pair of short
links;
h. thereby forming a toggle mechanism to toggle the links in a first operative horizontal direction and then in a second operative horizontal direction and finally again in the first operative vertical direction under the influence of said spring; and
i. secondary actuating shaft, placed parallel to said first shaft, adapted to translate motion of said primary actuating shaft towards actuating said deformable rhombus.

2. A mechanism as claimed in claim 1 wherein, said secondary actuating shaft includes said first joint at operative distal end of said secondary actuating shaft, thereby attaching one end of said deformable rhombus means i.e. attaching one end of said long links to secondary actuating shaft.
3. A mechanism as claimed in claim 1 wherein, said secondary actuating shaft includes said second joint at an operative distal end of said moving contact, thereby attaching other end of said deformable rhombus means i.e. attaching one end of said short links to said moving contact.
4. A mechanism as claimed in claim 1 wherein, said mechanism includes angle restrictor means adapted to be placed at said first joint, between said pair of long links, adapted to restrict the movement of the deformable rhombus at its first joint.
5. A mechanism as claimed in claim 1 wherein, said mechanism includes means to actuate said rhombus links in toggle condition so as to loosen the contact once main contact is made.
6. A mechanism as claimed in claim 1. wherein, said mechanism includes a stopper arrangement adapted to bring toggled condition of said deformable rhombus to its initial condition.