FORM2
THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)
1 Title of the invention AN ELECTROMECHANICAL INTERLOCKING
ARRANGEMENT FOR INTERLOCKING AT LEAST THREE POWER SOURCES
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:

TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electromechanical interlocking arrangement for connecting at least three power sources. More particularly, the invention is concerned about an interlocking arrangement for at least three Power sources using two mechanically interlocked Contactors being uniquely integrated and interconnected with each other.
BACKGROUND OF THE INVENTION
It is known and also popular to have interlocking arrangement for two power sources to ensure that only one of the power sources is supplying power at a time, Auto Mains Failure Schemes used in Generators make wide use of such schemes. When one source fails, other takes over and load is transferred to that. Existing range of 4 pole Contactors suitable for changeover applications are available with single deck construction, i.e. they have 4 NO contacts rated to carry the normal load current. Two such contactors are taken and mechanically interlocked either using base plate version or side mounted Mil KITs also electrically interlocked using NC of each contactor wired in series with coil of another contactors. This contemporary art provides effective change over schemes between two power sources, e.g. Utility supply and DG (diesel generator) supply.
US 5621254 document teaches an uninterruptible power switching method for use with an overlap-type change-over switch which performs switching between two different power supplies without interruption after concurrent connection for a predetermined period of time. However, the present invention is provided with a change over switch which performs switching among at least three or more different power supplies.
CN 2800461 document teaches the utility model relates to a rapid automatic change-over switch which comprises two alternating current contactors

connected together through mechanical interlocking components, wherein one alternating current contactor is connected with a general power supply and the other alternating current contactor is connected with a spare power supply. An intermediate relay and two self lock buttons are arranged, and an actuating coil of the intermediate relay is connected in parallel with an actuating coil of the alternating current contactor connected with the general power supply and then is connected with a general power supply through one self lock button. The actuating coil of the alternating current contactor connected with a spare power supply is connected in series with a normally closed contact of the intermediate relay and then is connected with a spare power supply through another self lock button. Since the utility model uses the double protection of the electric interlock and the mechanical interlock, the simultaneous electric supply of the two power sources can be avoided and the interphase short circuit can not be generated. The rotary speed is high, and the conversion time of the two TJ40 alternating current contactors is from 30 to 40 ms. The service life is long, and the service life can reach 50 ten thousand times. The electronic interference of electromagnetics is not generated, and the performance-price ratio is high. The cost of the utility model is from one third to one second compared with the cost of the general automatic change-over switch. However, this is the prior art prevailing in market and it teaches about rapid change over between two power sources and not three sources as mentioned in the present invention.
In case of momentary power cuts of few minutes or even few hours it may not be viable to start the DG sets and also time taken to build DG voltage and load transfer may not be acceptable to telecom market. In case to improve reliability need arises to give change over schemes / products suitable for interlocking and effective, reliable change over arrangement for at least three power sources. In the prior art, change over switches are available for effective change over between two sources. However the present invention is provided with change over switch which performs switching among three or more sources. Prior art has only power rated NO, whereas the present invention has a Double deck

construction with Power rated NO (4 contacts) in bottom deck and Power rated NC ( 4 contacts) in top deck and vice versa.
ADVANTAGES OF THE INVENTION
a) Frequent starting of generator can be avoided in case of frequent power failure.
b) Reduction in load transfer time can also be added advantage.
c) In case of power loss for longer duration, generator can be set to start after preset time delay (should be lower than inverter standby time).
d) Cater the need of Telecom Market wherein Electromechanical Interlocking arrangement is needed for three sources. Only one source at a time will be able to supply the load in case of three power sources. However, more combinations are also possible.
OBJECTS OF THE INVENTION
One of the basic objects of the present invention is to overcome the problems/disadvantages of the prior art.
Another object of the present invention is to provide an electromechanical interlocking arrangement for connecting at least three power sources.
Another object of the present invention is to provide a four pole contactor / switch with additional power rated NC deck.
Another object of the present invention is to provide an arrangement of NO / NC contacts in change over switch / contactors which would help to get change over schemes between 3 or more different power sources.

SUMMARY OF THE INVENTION
According to one aspect of the present invention there is provided an electromechanical interlocking arrangement for connecting at least three power sources, said arrangement comprising: two contactors wherein each of the said contactors having double deck construction defining bottom deck and top deck; wherein said bottom deck having Power rated NO and said top deck having Power rated NIC, optionally, said bottom deck having Power rated NC and said top deck having Power rated NO; and connecting means operatively connecting said contactors with said at least three power sources.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig 1 illustrates Electromagnetic Contactors with Mechanical Interlock.
Fig 2 illustrates Contactors/switches with power rated NO in bottom deck and power rated NC in top deck
DESCRIPTION OF THE INVENTION
The present invention is an electromechanical interlocking arrangement for the three or more power sources (S1, S2 and S3) (selectively DG, Utility, inverter and combination thereof) using two mechanically and electrically interlocked 4 pole contactors or specially designed changeover switch (1). The present invention is provided with unique wiring arrangement (W-i) to get interlocking of at least three power sources (S1, S2 and S3) using only two contactors (1). Each contactor (1) has a double deck construction comprising top deck (2) and bottom deck (3). The top deck (2) in the contactors comprises power rated NC (2a) and the bottom deck (3) in the contactors comprises power rated NO (3a) and vice versa for carrying full load current (5). The present invention has a Double deck

cbnstruction with power rated 4 NO contacts in bottom deck (3) and Power rated 4 NC contacts in top deck (2) and vice versa.
Existing methodology of Mechanical and Electrical interlocking schemes as shown in Fig 1, ar£ NO DECKS of both the contactors would be wired in series
load.
Following combinations would be possible.
Load will get Contactor/ Contactor/
Supply frorr1 Switch I Switch II
Source-I ON OFF
Source-II OFF ON
Source-III OFF OFF
The present invention is provided an electromechanical interlocking arrangement for connecting at least three power sources in different combinations such as Utility supply, DG supply and UPS—Uninterruptible Power Supply as one combination or Utility supply, DG-1 supply and DG-2 supply as another combination.

WE CLAIM
1. An electromechanical interlocking arrangement for connecting at least
three power sources, said arrangement comprising:
two contactors wherein each of the said contactors having double deck
construction defining bottom deck and top deck;
wherein said bottom deck having Power rated NO and said top deck
having
Power rated NC, optionally, said bottom deck having Power rated NC and
said
top deck having Power rated NO; and
connecting means operatively connecting said contactors with said at
feast three power sources.
2. The electromechanical interlocking arrangement as claimed in claim 1, wherein the connecting means comprises unique wiring arrangement.
3. The electromechanical interlocking arrangement as claimed in claim 1, wherein the power sources are selectively DG supply, Utility supply, inverter and combinations thereof.
4. The electromechanical interlocking arrangement as claimed in claim 1, wherein said bottom deck having Power rated 4 NO contacts.
5. The electromechanical interlocking arrangement as claimed in claim 4, wherein said bottom deck optionally comprises Power rated 4 NC contacts and

6. The electromechanical interlocking arrangement as claimed in claim 1, wherein said top deck having Power rated 4 NC contacts.
7. The electromechanical interlocking arrangement as claimed in claim 6, wherein said top deck optionally comprises Power rated 4 NO contacts.
8. The electromechanical interlocking arrangement as herein substantially described and illustrated with the accompanying drawings.