FORM2
THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
PROVISIONAL SPECIFICATION
(See section 10; rule 13)
1. Title of the invention. - AN AUTOMATED SYSTEM AND METHOD FOR MEASURING CLOSING OF CONATCT SYSTEM IN MOULDED CASE CIRCUIT BREAKER

2. Applicant(s)
(a) NAME :
(b) NATIONALITY :
(c) ADDRESS :

LARSEN & TOUBRO LIMITED
An Indian company
L & T House, Ballard Estate, Mumbai 400 001. State of Maharashtra, India

3. PREAMBLE TO THE DESCRIPTION
The following specification describes the invention

29 AUG 2008

TITLE OF THE INVENTION
AN AUTOMATED SYSTEM AND METHOD FOR MEASURING CLOSING OF CONATCT SYSTEM IN MOULDED CASE CIRCUIT BREAKER
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an automated system for inspecting the operations of a Moulded Case Circuit Breaker. More particularly, the present invention relates to an automated system that measures the position of the link of the breaker with a specially designed probe and a linear potentiometer, therefore verifying whether the moving contacts have reached to the final position. The final position is important for ensuring the complete angular travel of the drive shaft and hence the contact between, the upper and lower contacts.
BACKGROUND AND THE PRIOR ART
A circuit breaker is an electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit. Unlike a fuse, which operates once and then has to be replaced, a circuit breaker can be reset either manually or automatically to resume normal operation. When supplying a branch circuit with more than one live conductor, each live conductor must be protected by a breaker pole. To ensure that all live conductors are interrupted when any pole trips, a common trip breaker is used. Circuit
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breakers are made in varying sizes, from small devices that protect an individual household appliance up to large switchgear designed to protect high voltage circuits feeding an entire city.
Based on the features of circuit breakers, there are different classifications. The most commonly used being Low voltage (less than 1000 VAC} types which are applied in domestic, commercial and industrial applications. The common LV type circiut breakers are 3 types (i) Miniature Circuit Breaker (MCB), where the rated current not more than 100 A, trip characteristics normally not adjustable and useful for thermal or thermal-magnetic operation; (ii) Moulded Case Circuit Breaker (MCCB), where the rated current up to 10 00 A, trip current being adjustable in larger ratings and also useful for various thermal or thermal-magnetic operations; (iii) Low voltage power circuit breakers that can be mounted in multi-tiers in LV switchboards or switchgear cabinets.
In a Moulded Case Circuit Breaker (MCCB) the moving contacts need to be closed with sufficient pressure to enable current flow. The contact system is driven by a mechanism which is responsible for closing and opening of the contact. In order to ensure desired closing position of the moving contacts, the mechanism needs to move to final closing position. The method of checking the said parameter has been conventionally performed by operating the breaker with very slow speed and
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verifying the travel by physically pushing the link with a screwdriver.
The inventors of the present invention have surprisingly found an automated system that measures and verifies if the moving contacts have reached to the final position, being essential for ensuring closing of the contacts.
OBJECTS OF THE INVENTION
Accordingly, one object of the present invention is to provide an assembly of moving contacts for switching devices.
Another object of the present invention is to provide an automated system comprising an assembly of moving contacts that measures the position of the link of the breaker with a specially designed probe and a linear potentiometer, therefore verifying whether the moving contacts have reached to the final position.
Another object of the present invention is to provide a method involving an automated system comprising assembly of moving contacts for measuring the position of the link of the breaker.
Still another' object of the present invention is to provide an automated system comprising assembly of moving contacts that generates variable data in the
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form of readings that can be used for product improvement and statistical analysis.
Yet another object of the present invention is to provide a method for online positive verification of healthy breaker for contact closing without subjectivity.
SUMMARY OF THE INVENTION
The present invention provides an automated system comprising an assembly of moving contacts, which measures the position of the link of the breaker with a specially designed probe and a linear potentiometer, therefore verifying whether the moving contacts have reached to the final position. The final position of the contacts is detected by measuring the distance between the components of the breaker, when the breaker is in the ON condition.
The automated system is programmed for data acquisition of the tests and thereby of testing the 'No Final Stop' and measuring the 'Reset Force' of the breaker. The breaker is placed in the fixture in trip condition and. operated by the operating mechanism at the specified speed.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig 1 shows schematically the testing fixture according to the present invention.
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Fig 2 shows the breaker mechanism in RESET condition.
Fig 3 shows the breaker mechanism in ON condition and the probe for measuring the depth of the pivot pin.
Fig 4 shows the screen of the HMI for the test bench.
Fig 5 shows the screen of the online control charts.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The present invention describes an automated system comprising an assembly of moving contacts for inspecting and verifying the operations of a switching device.
When the breaker is reset and closed the breaker does not closed properly i.e. the drive shaft of the breaker does not rotate enough to close the breaker. This is the final stop problem where the contacts have two stops. The contacts come up after closing.
Final stop is to make sure that the breaker is properly switched "on". In some cases when the breaker . is switched "on" the drive-shaft does not rotate the angular movement it is supposed to (rotation varies from breaker to breaker) and hence if we apply some extra force the drive-shaft rotates forward which shows that the contact between the lower and upper contacts is not proper which shows that breaker is not properly switched "on". This problem is called No 'Final Stop'.
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'Final stop' is very important to be achieved as if it is not there then it will lead to a number of problems. When 'final stop' is not there that means the drive shaft has not traveled the full distance which it is supposed to, due to which the pressure exerted on the lower contact is not as much as it should be resulting in a weak contact between the lower and upper contact there are even chances of some of the components getting damaged due to this. One of the after effects of not having a final stop is not having continuity. Therefore it becomes very essential to check No-Final Stop of the breakers.
The automated system comprising -
(i) an Operating mechanism for operating the breaker -The operating mechanism is a lead screw (1) arrangement that is driven by a 3-Phase induction motor (8). The speed of this motor can be changed by varying the frequency of the electric power supplied to the motor through VFD [Variable Frequency Drive]. The "C" shaped jaw is always engaged with the extension knob of the breaker (7).
(ii) at least one Loadcell (2) for operating force measurement -
This loadcell (2) is for measuring the force for resetting the breaker. The loadcell gives analogue output continuously to PLC [Programmable Logic Controller] through the amplifier (12). The maximum
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value of force is captured from the TRIP position to the RESET position of the breaker. This is taken care by PLC (10).
(iii) at least one LVDT (4) for measuring the depth of the pivot pin -
The depth of the pivot pin is measured with respect to the top surface of the breaker housing. Similar to loadcell the LVDT also gives the analogue output continuously which required to be captured when the extension rod (3) coupled to the probe of LVDT rests on the Pivot pin. This is taken care by PLC program. The LVDT and the extension rod can be raised and lowered by pneumatic cylinder (5).
(iv) at least one Barcode scanner (30) -
It scans the bar code and the test results are stored against the barcode of the breaker. This kind of data acquisition helps in better traceability in case of any customer complaint.
The present invention further describes a method involving an automated system comprising assembly of moving contacts for measuring the position of the link of the breaker.
The method consists of the following procedural steps to be performed:
(a) loading the molded case circuit breaker (6) into the fixture in TRIP condition and ensuring
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the scanning of operator barcode by the
scanner; (b) pressing the "Start Test" button on the screen,
which starts the "AUTO CYCLE"; {c} undergoing necessary tests of the breaker and
saving the data against the barcode of the
breaker; (d) displaying the test result by 'OK' and 'NOT OK''
lamps on the control panel.
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Flowchart of "No-Final Stop" checking cycle
Load the breaker sub assay without cover and with extended knob and in trip condition into the setup
Operator
Reset the breaker
Switch ON the breaker.


Rejected:Unload the breaker

No

Yes
1st, 2nd cycle- switch 'OFF" the breaker, In 3rd Cycle TRIP' the breaker.


Dated this 29th day of August 2008

Saloni Rastogi
Of S. Majumdar&Co.
(Applicant's Agent)

29 AUG 2008

10