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 AUTOMATED SYSTEM AND A METHOD FOR
MEASURING CONTACT GAP AND MAGNET GAP
FOR CONTACTORS
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 :

FIELD OF THE INVENTION
The present invention relates to an improved automated system for measuring contact gap and magnet gap for contactors. More particularly, the invention relates to an improved automated system for measurement of distances at which the contacts change their status and the total travel of the contactor bridge. The invention also relates to a method for high precision measurement of contact and magnet gaps of contactors.
BACKGROUND AND THE PRIOR ART
A contactor consists of a magnetic circuit comprising a fixed core, a moveable armature and one or more air gaps; an electrically energizeable actuating coil; one or more sets of contacts; and springs for returning the armature to its unenergized position. When the contactor coil is energized, the bridge starts moving and during its travel the contacts change its condition and finally bridge stops.
GB2112213 discloses an improved electromagnetic contactor incorporating a magnetic flux sensing device. However, it was not known that the distances at which the contacts change their status and the total travel of the bridge can be measured by introducing automation in the system and achieving accurate, reliable and precise measurement.
US2003036300 discloses a contactor comprising at least two spaced-apart fixed contacts and an at least sectionwise electrically conductive, movable contact bridge having at least two contact points which are associated with said fixed
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contacts, said contact bridge being adapted to be moved to a switched position by a switching force which is produced by an actuating means and to a rest position by a pretensioning force which is produced by a pretensioning means and which substantially counteracts the switching force, one contact being arranged between the other contact and a point where the pretensioning force acts on the contact bridge. However, it was not known that the distances at which the contacts change their status and the total travel of the bridge can be measured by introducing automation in the system and achieving accurate, reliable and precise measurement.
The conventional system available in the market uses a method where bridge is pushed mechanically using a motorized or pneumatic device. Further there is no graphical representation of measured parameters, no provision for data storage and analysis of historical data
The conventional method of measurement of contact gap and magnet gap were time consuming, inconsistent reading, poor reliability and operator dependent.
Thus there is a need to provide for an improved automated
system and method for measurement of distances at which the
contacts change their status and the total travel of the
contactor bridge.
The present inventors have found that improved measurement of contact gap and magnet gap can be achieved and historical trend and analysis of the measured parametric values maintained for contactors s and the like by way of a system and a method for interfacing sensor outputs and contactor contacts thereby determining the required parameters.
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OBJECTS OF THE INVENTION
According to one object of the present invention is to overcome the disadvantages of the prior art.
Another object of the present invention is to provide a system to measure the contact gap and magnet gap for contactors accurately.
Another object of the present invention is to provide a method for measuring the contact gap and magnet gap for contactors accurately.
SUMMARY OF THE INVENTION
According to one aspect of the present invention there is provided an automated system to measure the contact gap and/or magnet gap for contactors, said system comprising:
sensing means mounted on the contactor which contact gap
and/or magnet gap to be measured;
converter means being operatively connected to said sensing
means, said converter means adapted to receive inputs from
said sensing means,
data acquisition means for sampling of all signals received
from converter means, said data acquisition means having high
sampling frequency; and
processing means receiving the sampled data from the data
acquisition means wherein the sampled data is processed and
analyzed to get desired parameter values.
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According to another aspect of the present invention there is provided a method for measuring contact gap and/or magnet gap for contactors, method comprising steps of:
Sensing of position changes of contactors in form of resistance changes when said contactors are energized; converting said resistance changes into potential changes by means of converter means and communicating the same to a data acquisition means for sampling wherein all potential changes are sampled; and
analyzing said sampled data in processing means so as to extract required information on contact gap and/or magnet gap for the contactors.
The other objects and advantages of the present invention will be apparent from the detailed description and the description provided hereinbelow with reference to the accompanying figures.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to an automated system for measurement of contact gap and/or magnet gap for contactors it is known that bridge of contactors comprise a moving part having moving contacts. When the contactor coil is energized the bridge starts moving and during its travel the contacts change its condition (i.e. normally closed (NC) contacts open and normally open contact (NO) closes) and finally bridge stops. Total Travel and Over travel are two very important parameters deciding the life of contactor. Considering manufacturing process variations in the components used in the assembly of contactor it is required to check this parameter for achieving final functionality.
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The system of the present invention facilitates measurement of distances at which the contacts change their status and the total travel of the bridge. The system of the present invention comprises a sensing means mounted on the bridge of the contactor. The sensing means is a linear potentiometer which is preferably spring loaded mounted such that in the OFF condition it is pre-compressed by at least a distance greater then total travel expected to be measured. The distance traveled is measured in the form of change in resistance of potentiometer. When the contactor is energized the potentiometer follows the bridge of contactor. Sensing means may be contact less or a contact type sensor depending on the contactor type. For contact less measurement, the potentiometer is replaced with a laser sensor. The laser sensor is implemented for small frame size contactor to eliminate effect of spring force on the measurement.
The system comprises a converter means which is a signal conditioning module which measures the resistance change of potentiometer in the form of potential change. The contactor continuity signal is also converted into potential change. The system further comprises a high speed data acquisition card which receives the data output from the said sensor and contactor contacts on distance traveled by the contactor bridge in the form of potential changes. The data acquisition card used in the present invention has sample frequency upto 100 KHz where each signal is sampled by 10 KHz. However, this sample frequency is not to be considered as restricting the scope of the present invention and any other data acquisition card with high order or lower order of sample frequencies can be used and still the invention can be performed.
The processing means of the present invention receives the sampled data output from the data acquisition means. The
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captured data is analyzed adopting a computer program. Total travel and over travel for each contact is derived and displayed. Graphical display of all channels is also available to analyze the signal manually. Additional parameters Like Bounce time and Number of bounce can be also derived from this by software.
Data captured is stored in the database for analysis on product and processes. The reference values are also stored in the database, actual values are compared with reference value and OK / not OK decision also given by the software.
Another embodiment of the present invention describes a method for measuring contact gap and/or magnet gap for contactors. The position changes of contactors are sensed in form of resistance changes when said contactors are energized. The acquired information/data on the contactor travel or position change measured in the form of change in resistance of the potentiometer is then converted into potential changes by means of converter means and communicated to a data acquisition means for sampling wherein all potential changes are sampled. The sampled data/information are then analyzed in a processing means so as to extract required information on contact gap and/or magnet gap for the contactors
Advantages :
• The measurement of the parameters is done in a manner that, there is no physical device pushing the bridge. So the measurement is true reflection of actual operation.
• System utilizes graphical representation of Bridge
movement. Bridge movement and contacts status are made
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available on screen. Graphical representation helps in debugging the problems easily.
• Test results are stored in a database. Results are compared with pre set limits and result are displayed as to whether passed or failed in the said test.
• Historical trend and analysis possible for selected parameters.
• Additional information like number of contact bounced and bounce time and speed can also be made available.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 illustrates a block representation of the system of the present invention.
DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 shows the system of the present invention which comprises sensor (1), signal conditioning Module (2), high speed Data Acquisition card (3) and processing means (4) .
The invention has been described in a preferred form only and many variations may be made in the invention which will still be comprised within its spirit. The invention is not limited to the details cited above. The components herein described may be replaced by its technical equivalence and yet the invention can be performed. The structure thus conceived is susceptible of numerous modifications and variations, all the

details may furthermore be replaced with elements having technical equivalence. In practice the materials and dimensions may be any according to the requirements, which will still be comprised within its true spirit.
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WE CLAIM
1. An automated system to measure the contact gap and/or
magnet gap for contactors, said system comprising:
sensing means mounted on the contactor which contact gap
and/or magnet gap to be measured;
converter means being operatively connected to said
sensing means, said converter means adapted to receive
inputs from said sensing means,
data acquisition means for sampling of all signals
received from converter means, said data acquisition
means having high sampling frequency; and
processing means receiving the sampled data from the data
acquisition means wherein the sampled data is processed
and analyzed to get desired parameter values.
2. System as claimed in claim 1, wherein the sensing means comprises a potentiometer.
3. System as claimed in claim 2, wherein the sensing means is preferably spring loaded potentiometer.
4. System as claimed in claims 1 to 3, wherein the potentiometer is pre-compressed by a distance greater than total travel expected to be measured.
5. System as claimed in claims 1 to 4, wherein the sensing means is optionally a contact less sensor.
6. System as claimed in claim 5, wherein the contact less sensor is a laser sensor.
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7. System as claimed in claim 1, wherein the converter means comprises a signal conditioning module.
8. System as claimed in any of the preceding claims adapted to additionally measure bounce time and number of bounce.
9. A method for measuring contact gap and/or magnet gap for
contactors, method comprising steps of::
sensing of position changes of contactors in form of
resistance changes when said contactors are energized;
converting said resistance changes into potential
changes by means of converter means and communicating the
same to a data acquisition means for sampling wherein all
potential changes are sampled; and
analyzing said sampled data in processing means so as to
extract required information on contact gap and/or magnet
gap for the contactors.
10. Method as claimed in claim 8 further comprising steps of converting contactor contact continuity signal to potential change.

Dated this 26th day of March 2008

Abhishek Sen
Of S. Majumdar & co.
(Applicant's Agent)

ABSTRACT
AN AUTOMATED SYSTEM AND A METHOD FOR MEASURING CONTACT GAP AND MAGNET GAP FOR CONTACTORS
The present invention relates to an automated system to measure the contact gap and/or magnet gap for contactors. The system comprises sensing means (1) mounted on the contactor, converter means (2), data acquisition means (3) and processing means (4) . The converter means is adapted to receive inputs from the sensing means and the data acquisition means samples all signals received from the converter means. Sampled data is received by processing means where the sampled data is processed and analyzed to get desired parameter values. The invention also relates to a method for measuring contact gap and/or magnet gap for contactors.
Figure 1
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