FORM 2
The Patents Act 1970
(39 of 1970)
&
The Patent Rules 2003
COMPLETE SPECIFICATION
(See Section 10 and rule 13)
TITLE OF THE INVENTION:


RATING ERROR PREVENTING DEVICE FOR DRAWOUT FEEDER UNITS OF MOTOR CONTROL CENTER
SWITCHBOARDS

APPLICANT:
LARSEN & TOUBRO LIMITED
L&T House, Ballard Estate, P.O. Box No. 278,
Mumbai, 400 001, Maharashtra . INDIA.
PREAMBLE OF THE DESCRIPTION:
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED


A) TECHNICAL FIELD
[0001] The present invention generally relates to switch boards and particularly to draw out unit in motor control center (MCC) switchboards. The present invention more particularly relates to a rating error preventor in full width draw out feeder units of the MCC switchboards.
B) BACKGROUND OF THE INVENTION
[0002] Generally, every module of draw out feeders has a particular predefined rating value. Similar modules with same rating can only be inserted together to achieve a specific task. A rating error prevention device ensures that modules such as the draw-out feeders of matching rating only get fully inserted in a cradle.
[0003] A motor control center (MCC) is a modular assembly specifically designed to plug in motor control units. The MCC is supplied by a common bus, usually straight from the switchboard. A MCC consists of one or more vertical metal cabinet sections with power bus and provision for plug-in mounting of individual motor controllers. Very large controllers may be bolted in place but smaller controllers can be unplugged from the cabinet for testing or maintenance. Each motor controller contains a contactor and overload relays to protect the motor, fuses or a circuit breaker to provide short-circuit protection, and a disconnecting switch to isolate the motor circuit. The insertion of similar feeders of different rating into unwarranted
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feeder units of MCC switchboards causes an unpredictable functioning or damage of the downstream load connected to the feeder unit or, associated assembly.
[0004] The trend in modern draw out switchboard feeders is to have less number of frames in the entire range. This means that more than one rating is accommodated in one frame size. This results in common spare components that a user is required to store. However, this can also lead to a situation where modules of different ratings are assembled for a particular feeder. For example, if draw out feeders of 630A, 800A, and 1000A have a common frame, then static and moving units of these ratings are of the same size. Hence, it must be ensured that a moving unit of 630A is assembled onto a static unit of 630A only and not of any other ratings. This is a quite significant as the protection of the downstream equipment is affected by mismatch in static and moving units ratings. If a moving unit of 1000A is assembled onto a static unit of 630A in any circumstance, then the module may not trip on overload corresponding to 630A. This may lead to damage on the cable/links in the system and apparatus to be protected. On the other hand, if a moving unit of 630A is inserted in a static unit of 1000A, it results in nuisance tripping.
[0005] In order to avoid such eventualities, different rating mismatch prevention methods exist. One such method first permits a wrong moving unit to be inserted in the static unit and only after some travel, forbids further racking in of the moving unit. However, excessive pressure is applied at this stage, it leads to damage occurring. None of the currently available devices disclose a simple but effective rating error preventing mechanism for switch boards.


[0006] Hence, there is a need for a simple but effective rating error preventing mechanism and a method to avoid an error arising out of insertion of similar feeders of different rating into unwarranted feeder units of motor control center switchboards.
[0007] The abovementioned shortcomings, disadvantages and problems are addressed herein and will be understood by reading and studying the following specification.
C) OBJECT OF THE INVENTION
[0008] The primary object of the present invention is to provide a rating error preventing device to avoid an error arising out of insertion of similar feeders of different rating into unwarranted feeder units of motor control center switchboards.
[0009] Another object of the present invention is to provide a rating error preventing device with the same type of preventor block for both moving and stationary units.
[0010] Yet another object of the present invention is to provide the rating error preventing device in maintaining the correspondence between the current rating of a particular feeder and a load connected to it.


[0011] These and other objects and advantages of the present invention will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings.
D) SUMMARY OF THE INVENTION
[0012] The various embodiments of the present invention provide a rating error preventing device to avoid an error arising out of insertion of similar feeders of different rating into unwarranted feeder units of motor control center switchboards. According to one embodiment of the present invention, a rating error preventing device for switch boards is provided with a moving unit which is slided into a stationary unit. Both the units are provided with a vertical side wall. A first set of blocks is provided at the back side of the vertical side wall in the moving unit. A second set of blocks is provided at the front side of the vertical side wall in the stationary unit. The first set of blocks and the second set of blocks provided respectively in the moving unit and the stationary unit are complementary set of blocks so that the first set of blocks in the moving unit are guided through the gap between the second set of blocks in the stationary unit when a moving unit with a proper rating is inserted into the stationary unit. The first set of blocks in the moving unit is stopped by the second set of blocks in the stationary unit when the moving unit with an improper rating is inserted into the stationary unit,
[0013] The number of first set of blocks mounted on the moving unit depends on the rating of the feeder module. The number of second set of blocks mounted on the
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stationary unit depends on the rating of the feeder module. The moving unit is a feeder module. The stationary unit is attached to the structure of switch board.
E) BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The other objects, features and advantages will occur to those skilled in the art from the following description of the preferred embodiment and the accompanying drawings in which:
[0015] FIG. 1 illustrates a side perspective view of a rating error preventor with a correct matching of preventor blocks of both moving and stationary units in the case of insertion of similar feeders of same rating according to one embodiment of the present invention.
[0016] FIG. 2 illustrates side perspective view of a rating error preventor with a mismatching of preventor blocks of both moving and stationary units in the case of insertion of similar feeders of different rating according to one embodiment of the present invention.
[0017] Although specific features of the present invention are shown in some drawings and not in others. This is done for convenience only as each feature may be combined with any or all of the other features in accordance with the present invention.


F) DETAILED DESCRIPTION OF THE INVENTION
[0018] In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which the specific embodiments that may be practiced is shown by way of illustration. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments and it is to be understood that the logical, mechanical and other changes may be made without departing from the scope of the embodiments. The following detailed description is therefore not to be taken in a limiting sense.
[0019] The various embodiments of the present invention provide a rating error preventing device to avoid an error arising out of insertion of similar feeders of different rating into unwarranted feeder units of motor control center switchboards. According to one embodiment of the present invention, a rating error preventing device for switch boards is provided with a moving unit which is slided into a stationary unit. Both the stationary and the moving units are provided with a vertical side wall. A first set of blocks is provided at the back side of the vertical side wall in the moving unit. A second set of blocks is provided at the front side of the vertical side wall in the stationary unit. The first set of blocks and the second set of blocks provided respectively in the moving unit and the stationary unit are complementary set of blocks so that the first set of blocks in the moving unit are guided through the gap between the second set of blocks in the stationary unit when a moving unit with a proper rating is inserted into the stationary unit. The first set of blocks in the moving


unit is stopped by the second set of blocks in the stationary unit when the moving unit with an improper rating is inserted into the stationary unit.
[0020] The number of first set of blocks mounted'on the moving unit depends on the rating of the feeder module. The number of preventor blocks mounted on the stationary unit depends on the number of units to be used with the single stationary unit. The moving unit is a feeder module. The stationary unit is attached to a switch board.
[0021] According to one embodiment of the present invention, a rating error preventor has s set of units that are a stationary unit and a moving unit. The stationary unit comprises of a top cross piece, a bottom cross piece and a side plate. Both the top cross piece and the bottom cross piece are arranged in parallel. The side plate is mounted in between the bottom and top cross pieces.
[0022] The side plate has a number of preventor blocks depending on a requisite number of different modules covered under the rating error prevention mechanism. For example, the number of preventor blocks in the side plate ranges from two to four in case of 140mm height and from two to five in case of 280mm height of module. The moving unit has a set of preventor blocks mounted at different positions on the side walls of the moving unit (feeder module) in all the cases.
[0023] As the full-width module pertaining to a particular current rating is pushed inside the corresponding feeder compartment, the set of preventor blocks in the
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moving unit meets the complementing (correct) set of blocks in the stationary unit and the preventor blocks of the moving unit traverse further through the gaps provided in between the preventor blocks of the stationary unit. Thereby, the feeder module is allowed to be inserted fully inside the preventor blocks of the stationary unit. Any other feeder modules of same size but different rating have a different combination of preventor blocks. Hence, the preventor blocks in the moving unit hit against the preventor blocks in the stationary unit thereby preventing the insertion of impertinent module inside the feeder compartment.
[0024] The maximum number of module combinations is derived from the following derivation:
{N+2}C2 where N is the number of preventor blocks mounted on the stationary unit. For example, if N = 4, then the maximum possible number of module combinations is {4+2}C2=6C2 = 15.
[0025] FIG. 1 illustrates a side perspective view of a rating error preventor with a correct matching of preventor blocks of both moving and stationary units in the case of insertion of similar feeders of same rating according to one embodiment of the present invention. With respect to FIG. 1, the rating error preventor has a set of units called as a stationary unit and a moving unit. The stationary unit includes four numbers of preventor blocks 1, a side plate 2, a top cross piece 4, and a bottom cross piece 5. The side plate 2 is mounted in between the top and bottom cross pieces 4 and 5. The four numbers of preventor blocks 1 are protruding out from the inner of the side plate 2. The moving unit has a set of preventor blocks 3 protruding out from the
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side walls of the moving unit (feeder module) in all cases. During insertion of similar modules of same rating with the corresponding feeder compartment, the set of preventor blocks 3 in the moving unit meets the complementing the four numbers of preventor blocks 1 in the stationary unit. The set of preventor blocks 3 of the moving unit traverse further through the gaps provided in between the four numbers of preventor blocks 1 of the stationary unit. Thereby, the module is allowed to be inserted fully inside the feeder.
[0026] FIG. 2 illustrates side perspective view of a rating error preventor with a mismatching of preventor blocks of both moving and stationary units in the case of insertion of similar feeders of different rating according to one embodiment of the present invention. With respect to FIG. 2, feeder modules of same size but different rating have a different combination of preventor blocks. Hence, the set of preventor blocks 3 in the moving unit hits against the preventor blocks 1 in the stationary unit during the insertion of similar modules of different rating with the feeder compartment. Thus, the insertion of impertinent module inside the feeder compartment is prevented.
G) ADVANTAGES OF THE INVENTION
[0027] Thus the various embodiments of the present invention provide a method to avoid an error arising out of insertion of similar feeders of different rating into unwarranted feeder units of motor control center switchboards. A rating error preventor is achieved by using a single type of preventor block design for both
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moving and stationary units. The rating error preventor helps in maintaining the correspondence of current rating of a particular feeder and a load connected to it.
[0028] Although the invention is described with various specific embodiments, it will be obvious for a person skilled in the art to practice the invention with modifications. However, all such modifications are deemed to be within the scope of the claims.

RAKESH PRABHU
Patent Agent
[0029] It is also to be understood that the following claims are intended to cover ail of the generic and specific features of the present invention described herein and all the statements of the scope of the invention which as a matter of language might be said to fall there between.
Date: March 30, 2009 Place: Bangalore.

CLAIMS
What is claimed is:
1. A rating error preventing device for switch boards, the device comprising:
a moving unit;
a first set of blocks provided on the moving unit;
a stationary unit: and
a second set of blocks provided on the stationary unit;
wherein the first set of blocks and the second set of blocks provided
respectively in the moving unit and the stationary unit are complementary set
of blocks so that the first set of blocks in the moving unit are guided through
the gap between the second set of blocks in the stationary unit when a moving
unit with a proper rating is inserted into the stationary unit.
2. The device according to claim 1, wherein the first set of blocks in the moving unit are stopped by the second set of blocks in the stationary unit when the moving unit with an improper rating is inserted into the stationary unit.
3. The device according to claim 1, wherein the number of first set of blocks mounted on the moving unit depends on the rating of the moving unit.
4. The device according to claim 1, wherein the number of second set of blocks mounted on the stationary unit depends on the number of rating units to be used with the single stationary unit.
5. The device according to claim 1, wherein the moving unit is a feeder module.


6. The device according to claim 1, wherein the stationary unit is attached to a switch board.
7. The device according to claim 1, wherein the stationary unit has a vertical side wall.
8. The device according to claim 1, wherein the second set blocks are provided at the front portion of the vertical side wall in the stationary unit.
9. The device according to claim 1, wherein the moving unit has a vertical side wall.
10. The device according to claim 1, wherein1 the first set blocks are provided at the back portion of the vertical side wall in the moving unit.

RAKESH PRABHU
Patent Agent,
ALMT Legal,
#2, Lavelle Road, Bangalore -560 001
To,
The Controller of Patents. The Patent Office, Mumbai
Dated this the 30th day of March 2009