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: AN IMPROVED ARRANGEMENT AND METHOD FOR IMPROVING RELIABILITY AND ELECTRICAL DURABILITY OF ARRANGEMENT FOR REVERSING APPLICATION USING ELECTROMAGNETIC SWITCHES & CONTACTORS
2. Applicants):

(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 improved circuit arrangement. Particularly, the present invention relates to method used for method used for forward and reversing application of Motor control. More particularly, the invention relates to an improved circuit arrangement and method for forward-reverse control of Induction motors for the purpose of improved reliability and electrical durability.
BACKGROUND AND PRIOR ART OF THE INVENTION
Fig-1 discloses the Prior-art method of circuit diagram. The forward and reverse contactor coils are wired in series with NC (Normally closed contacts) of other contactors respectively i.e. forward contactor coil is wired in series with NC(Normally closed contacts) contact of reverse contactor and vice versa.
Sequence of operation of the prior art circuit as shown in fig 1:
Start-1 push button 93-94 is pressed.
This give closed path for forward contactor to close and motor is given particular
phase sequence to ensure forward rotation.
Start push button is left and circuit remains closed through 23-25, i.e. NC
(Normally open contacts) of forward contactor.
After certain duration, supply to forward contactor is cut-off and start-2 is pressed.
This give closed path for reverse contactor to close and motor is given reverse
phase sequence (2 phases interchanged) to ensure reverse rotation.
Start push button is left and circuit remains closed through 23-25, i.e. NC
(Normally open contacts) of reverse contactor.
Fig 2 shows what each cycle comprises of in the form of block diagram.
The typical normal cycle would look like as shown in fig 3.
The prior art arrangement keeps working till there is no overlap in time line while
forward contactor drops-off and reverse contactor picks-up.

However, successful closing of each next, either forward or reverse contactor depends on complete drop-out of previously closed contactor and sufficiently delayed closing of next contactor to close.
The major drawbacks of this circuit arrangement as in fig 1:
Based on variations in pick-up and drop-off times of contactors, overlap results in simultaneous closing of next contactor and hence short circuiting of 2 phases. This further leads to damage to electromagnetic switch/contactors. This reduces the useful life span of electromagnetic devices/contactors and need for frequent replacement/maintenance.
In view of the above there is a need to provide an improved circuit arrangement and method that ensures overall reliability of the forward-reverse circuit arrangement and also improves useful life of such arrangements.
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 improved circuit arrangement for forward-reverse control of Induction motors for the purpose of improved reliability and electrical durability.
Another object of the present invention is to provide an improved circuit method for forward-reverse control of Induction motors for the purpose of improved reliability and electrical durability.
Yet another object of the present invention is to provide an improved arrangement and method that is able to add inherent delay while giving closing command to next contactor to be closed.

Yet another object of the present invention is to provide an improved arrangement and method that previously closed contactor switch has fully dropped out and even arcing time has been taken care off.
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 the system is provided an improved arrangement for improving reliability and electrical durability of electromagnetic switches, contactors, said arrangement comprising:
plurality of contact arrangement comprises TK1 and TK2 , said arrangement has NC(Normally open contacts) and NC(Normally closed contacts) on same block;
a forward contactor;
a reverse contractor; and
an interposing contractor;
wherein said interposing contractor closes such that either forward contractor or reverse contactor closes and shows inherent time delay of few milliseconds,

wherein said interposing contractor provides an inherent delay to closing of either reverse contractor or forward contractor.
According to another the aspect of the present invention there is provided an improved method improving reliability and electrical durability of electromagnetic switches, contactors, said method comprising steps of:
An improved method improving reliability and electrical durability of electromagnetic switches, contactors, said method comprising steps of:
closing of a contact arrangement so as to closing the path for an interposing
contactor to close the interposing contractor;
closing of reverse path to close the reverse contactor, such that interposing
contactor remain closed till reverse contactor is also closed;
pressing of another contact arrangement to close forward contactor;
opening ofreverse path resulting in opening of interposing contactor; and
closing of forward path to close forward contactor;
such that one cycle is completed.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to an improved circuit arrangement and method that introduces inherent time delay of few milliseconds resulting in closing of next, i.e. either forward or reverse contactor only and only if Inter-posing contactor has closed. This ensures that only when one particular contactor drops out fully, then next contactor gets closing command. This improves overall reliability of the forward-reverse circuit arrangement and also improves useful life of such arrangements.
According to the first embodiment of the present invention there is provided an improved arrangement for improving reliability and electrical durability of

electromagnetic switches, contactors. The arrangement comprises plurality of contact arrangement, a forward contactor, a reverse contractor and an interposing contractor.
The contact arrangement comprises TK1 and TK2 where the arrangement has NC (Normally open contacts) and NC (Normally closed contacts) on same block
The interposing contractor closes such that either forward contactor or reverse contactor closes and shows inherent time delay of few milliseconds,
The interposing contractor provides an inherent delay to either reverse contractor or forward contractor.
The interposing contact provides an inherent delay of about 40 to 50 mSec. The Normally open contacts of interposing contactors close first for completing the electrical control circuit of either forward or reverse contactor to be closed, both of them cannot close.
According to the second embodiment of the present invention there is provided an improved method improving reliability and electrical durability of electromagnetic switches, contactors. The method comprises steps of closing of a contract arrangement so as to closing the path for an interposing contactor to close interposing contactor, closing of reverse path to close the reverse contactor, such that interposing contactor remain closed till reverse contactor is also closed , pressing of another contact arrangement to close forward contactor , opening of reverse path resulting in opening of interposing contactor, and closing of forward path to close forward contactor so that one cycle is completed.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
The above and other aspects, features, and advantages of certain exemplary embodiments of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings in which:

Figure 1 illustrates prior-art method of circuit diagram.
Figure 2 illustrates block diagram of prior art cycle.
Figure 3 illustrates prior art cycle graph.
Figure 4 illustrates prior art cycle graph with its drawback.
Figure 5 illustrates the improved circuit arrangement.
Figure 6 illustrates improved cycle graph.
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 DRAWING
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.
Fig 5 discloses the improved circuit of the present invention.
Note L: TK1 and TK2 are nothing but contact arrangement of NO (Normally open contacts) and NC (Normally closed contacts) (Normally closed contacts) in same block(can be operated simultaneously with single lever leading to opening of NC(Normally closed contacts) - Normal closed contacts first and then closing of NC(Normally open contacts)-Normally open contacts)
Working of present improved arrangement:
TK1 is closed.
This closes the path for C- contactor.
C closes.
R path closes - This closes the reverse contactor.
C remains closed till R is also closed.
Press TK2, this is required to close forward contactor.
R path opens resulting in opening of C also.

F path closes.
F closes.
This completes one cycle.
It is seen that unless contacts of C, i.e. Normally open contacts of Interposing contactors close first for completing the electrical control circuit of either forward or reverse contactor to be closed, both of them can not close. This ensures certain minimum time delay in closing command to next contactor, i.e. either forward or reverse contactor to be closed.
Hence, new improved cycle is shown in fig 6, where inherent delay of 40-50 mSec is added due to introduction of interposing contactor, resulting in delayed closing of next contactor, i.e. either forward or reverse.
Features:
• This new arrangement is able to add inherent delay while giving closing command to next contactor to be closed.
• This ensures that previously closed contactor switch has fully dropped out and even arcing time has been taken care off.
• This improves overall reliability of the forward-reverse circuit arrangement.
• This also improves useful life of the forward-reverse arrangement.

WE CLAIM:
1. An improved arrangement for improving reliability and electrical
durability of electromagnetic switches, contactors, said arrangement
comprising:
plurality of contact arrangement comprises TK1 and TK2 , said arrangement has NC (Normally open contacts) and NC (Normally closed contacts) on same block;
a forward contactor (F);
a reverse contractor (R); and
an interposing contractor (C);
wherein said interposing contractor (C) closes such that either forward contractor (F) or reverse contactor (R) closes and shows inherent time delay of few milliseconds,
wherein said interposing contractor (C) provides an inherent delay of either reverse contractor (R) or forward contractor (F).
2. Arrangement as claimed in claim 1 wherein said interposing contact provides an inherent delay of about 40 to 50 mSec.
3. Arrangement as claimed in claim 1 wherein said Normally open contacts of Interposing contactors close first for completing the electrical control circuit of either forward or reverse contactor to be closed, both of them can not close.
4. An improved method improving reliability and electrical durability of electromagnetic switches, contactors, said method comprising steps of:

dosing of a contract arrangement (TK1) so as to cYosing the path for an
interposing contactor(C); to close interposing contactor (C)
closing of reverse path to close the reverse contactor (R), such that
interposing contactor (C) remains closed till R is also closed
pressing of another contact arrangement (TK2)to close forward contactor
(F);
opening of reverse path resulting in opening of interposing contactor also;
and
closing of forward path to close forward contactor;
such that one cycle is completed.
5. Method as claimed in claim 1 wherein said interposing contractor (C) providing an inherent delay of about 40 to 50 mSec.
6. An improved arrangement for improving reliability and electrical durability of electromagnetic switches, contactors as herein substantially described and illustrated with the accompanying drawings.
7. An improved method for improving reliability and electrical durability of electromagnetic switches, contactors as herein substantially described and illustrated with the accompanying drawing-