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: SLOT MOTOR ASSEMBLY FOR CIRCUIT BREAKERS
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 circuit breakers and particularly relates to a contact system in molded case circuit breakers. More particularly the present invention relates to a contact system with a slot motor assembly for the molded case circuit breakers to exert a magnetic pull on a moving contact.
B) BACK GROUND OF THE INVENTION
[0002] Circuit breakers are the mechanical switching devices capable of making, carrying and breaking currents under normal circuit conditions and also making, carrying for a specified time and breaking currents under specified abnormal conditions. A circuit breaker basically consists of a pair of separable contacts and an interrupting medium. The function of the contacts is to conduct the electrical current, when the breaker is closed and to withstand the arcs while interrupting. Generally the electrical contacts have a stationary part and a moving part. By bringing the moving contact to touch the stationary contact, an electric current flows and the breaker is closed. By driving the moving contact away from the stationary contact an electric arc is developed and by quenching the arc, the electrical current flow is stopped and the breaker is opened.
[0003] In the existing technique, the circuit breakers are extensively used in the power distribution systems to provide a protection for an electrical equipment from the electrical fault conditions such as current overloads, short circuits and abnormal level voltage conditions. The short circuit capacity of any circuit breaker is governed by the performance of an arc quenching chamber in the circuit breakers. Further in the existing technique, the circuit breakers consist of the arc chamber assembly which when subjected to a short circuit current of few kilo amperes quench the arc with long

arcing times. The long arcing times leads to create a stress on the downstream equipments due to a large amount of let through energy. Further this is caused due to the inability to channelize the arc and hot gases effectively during the high fault conditions in the circuit breakers.
[0004] In the existing techniques, the circuit breaker does not include a slot motor or the existing slot motor is underutilized thereby creating a detrimental effect on the arc root movement towards the arc chamber. Further the circuit breakers consisting of the slot motor in the existing technique are inefficient in terms of a faster contact movement and do not have an optimum speed of separation of the moving contact. Further in the existing techniques, the limbs of the circuit breakers are extended up to the lower contact assembly to create a negative pull on the arc root movement.
[0005] Hence there exists a need to provide a slot motor assembly in the molded case circuit breakers to provide a magnetic pull on the moving contact to enhance the separation of the moving contact. Further there is a need to provide a contact system with an optimized slot motor assembly that enhances the circuit breakers breaking capacity by the effective utilization of a magnetic field generated by a slot motor assembly.
[0006] The above mentioned shortcomings, disadvantages and problems are addressed herein and which will be understood by reading and studying the following specification.
C) OBJECT OF THE PRESENT INVENTION

[0007] The primary object of the present invention is to provide a slot motor assembly to enhance a magnetic pull on a moving contact in the circuit breakers.
[0008] Another object of the present invention is to provide a slot motor assembly in which the speed of the moving contact in the molded circuit breaker is enhanced during the short circuit conditions.
[0009] Yet another object of the present invention is to provide a slot motor assembly in which the total arcing time and a let through energy is reduced.
[0010] Yet another object of the present invention to provide a slot motor assembly in which the contact opening time is reduced.
[0011] Yet another object of the present invention to provide a slot motor assembly having a plurality of slot laminations with an optimal length to reduce a negative pull on the arc.
[0012] Yet another object of the present invention to provide a slot motor assembly in the circuit breaker provided with a release assembly and a knob.
D) SUMMARY OF THE INVENTION
[0013] The various embodiments of the present invention provide a circuit breaker with an arc chute assembly, a moving contact, a fixed contact and a slot motor assembly. The slot motor assembly is provided with a plurality of slot motor laminations to generate a magnetic field to enhance a magnetic pull on the moving contact to increase a contact separation speed.

[0014] According to one embodiment of the present invention, the plurality of slot motor laminations is U-shaped.
[0015] According to one embodiment of the present invention, the plurality of slot motor laminations is designed with a defined length and cross-sectional area to create a maximum pull on the moving contact.
[0016] According to one embodiment of the present invention, the slot motor assembly comprises a slot motor housing and a slot motor cover.
[0017] According to one embodiment of the present invention, the plurality of slot motor laminations is made up of a highly permeable magnetic material.
[0018] According to one embodiment of the present invention, the plurality of slot motor laminations are inserted in the slot motor housing and the slot motor cover is placed over the plurality of slot motor laminations to electrically isolate the slot motor assembly from an arcing region.
[0019] According to one embodiment of the present invention, the slot motor assembly is adapted to pull an arc towards the arc chute assembly during the short circuit conditions thereby reducing an arc running time.
[0020] According to one embodiment of the present invention, the slot motor assembly is designed in such a way that a maximum pull is created on the moving contact assembly.

[0021] According to one embodiment of the present invention, the plurality of slot laminations is provided with an optimal length so as to reduce a negative pull on the arc.
[0022] 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.
E) BRIEF DESCRIPTION OF THE DRAWINGS
[0023] 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:
[0024] FIG. 1 illustrates the cross sectional view of the molded case circuit breakers according to one embodiment of the present invention.
[0025] FIG.2 illustrates the front side perspective view of the molded case circuit breaker without cover according to one embodiment of the present invention.
[0026] FIG.3 illustrates the isometric view of the slot motor assembly in molded case circuit breakers, according to one embodiment of the present invention.
[0027] FIG.4 illustrates an exploded view and an assembled side view of the slot motor assembly in molded case circuit breakers, according to one embodiment of the present invention.
[0028] Although the 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
[0029] In the following detailed description, a 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.
[0030] The various embodiments of the present invention provide a circuit breaker with an arc chute assembly, a moving contact, a fixed contact and a slot motor assembly. The slot motor assembly is provided with a plurality of slot motor laminations to generate a magnetic field so as to enhance the magnetic pull on the moving contact to increase the contact separation speed.
[0031] FIG. 1 illustrates the cross sectional view of the molded case circuit breakers according to one embodiment of the present invention, while FIG.2 illustrates the front side perspective view of the molded case circuit breaker without cover according to one embodiment of the present invention. With respect to the FIG.l and FIG.2, the molded case circuit breaker includes an arc chute assembly 102, a front vent 104; a back vent 106, a moving contact 108, a fixed contact 110, a housing 112, a release assembly 114, a knob 116 and a slot motor assembly 118.

[0032] The slot motor assembly 118 is provided with a plurality of slot motor laminations to generate a magnetic field which in turn enhances the magnetic pull on the moving contact 108. The slot motor assembly 118 is located in the molded case circuit breaker in such a way that the speed of the moving contact 108 is enhanced during the short circuit conditions.
[0033] The design of the slot motor assembly 118 is optimized in such a way that a maximum pull on the moving contact 108 is created. The optimum use of the slot motor assembly 118 reduces the arc running time which in turn reduces the total arcing time.
[0034] The slot motor assembly 118 in the circuit breakers enhances the magnetic pull on the moving contact 108 and does not create a negative effect on the arc root movement. This reduces the contact opening time and also the arc running time. The lower arcing time reduces the total let through energy which in turn reduces the stress on the one or more equipments in the electric system.
[0035] F1G.3 illustrates the isometric view of the slot motor assembly in molded case circuit breakers, according to one embodiment of the present invention, while FIG.4 illustrates the exploded view of the slot motor assembly in molded case circuit breakers, according to one embodiment of the present invention. With respect to FIG.3 and FIG.4. the slot motor assembly 118 includes a slot motor housing 302, a slot motor cover 304, and a plurality of laminations 306.
[0036] The slot motor assembly ll8 includes the plurality of slot motor laminations 306 stacked one above the other in a slot motor housing 302. The pluralities of slot motor laminations 306 are U-shaped. The no. of slot motor laminations 306 defines the required magnetic pull on the moving contact 108. The

plurality of slot motor laminations 306 is inserted into the slot motor housing 302 and the slot motor cover 304 is placed over the top to electrically isolate the slot motor assembly 118 from an arcing region.
[0037] The pluralities of slot motors laminations 306 in the slot motor assembly 118 generate the magnetic field to enhance the magnetic pull on the moving contact 108 and to increase the contact separation speed. The circuit breakers breaking capacity is enhanced by the effective utilization of a magnetic field generated by the plurality of slot motor laminations 306 in the slot motor assembly 118.
[0038] The cross sectional area and the length of the plurality of slot motors laminations 306 are optimized in such a way that the arc root movement is not altered. The optimization of the cross sectional area and length of the plurality of slot motors laminations 306 leads to a faster contact separation and to reduce a total arcing time and a let through energy.
[0039] The plurality of slot motor laminations 306 is designed with a defined length and cross-sectional area to create a maximum pull on the moving contact 108. The plurality of slot motor laminations 306 is provided with an optimal length to reduce a negative pull on the arc. This increases the arc velocity which in turn reduces the arcing time and the let through energy.
G) ADVANTAGES OF THE INVENTION
[0040] The various advantages of the present invention are that the optimum use of slot motor assembly in the molded case circuit breaker reduces the arc running time and the total arcing time. The slot motor assembly enhances the magnetic pull

on the moving contact without creating a detrimental effect on the arc ro. movement. The blow-out field on the arc towards the arc chute assembly reduces th contact opening time and also increases the arc velocity. The plurality of slot moto laminations is provided with an optimal length so as to reduce a negative pull on the arc. This increases the are velocity which in tum reduces the arcing time and the let through energy.
[0041) 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.
[0042J It is also to be understood that the following claims are intended to cover all 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.

CLAIMS
What is claimed is:
1. A contact assembly of a molded case circuit breaker comprising:
an arc chute assembly;
a moving contact;
a fixed contact; and
a slot motor assembly;
Wherein the slot motor assembly is provided with a plurality of slot motor
laminations to generate a magnetic field so as to enhance a magnetic pull on
the moving contact to increase a contact separation speed.
2. The contact assembly according to claim 1, wherein the plurality of slot motor laminations are U-shaped.
3. The contact assembly according to claim 1, wherein the plurality of slot motor laminations is designed with a defined length and cross-sectional area to create a maximum pull on the moving contact.
4. The contact assembly according to claim 1, wherein the slot motor assembly comprises a slot motor housing and a slot motor cover,
5. The contact assembly according to claim 1, wherein the plurality of slot motor laminations are made up of a highly permeable magnetic material.
6. The contact assembly according to claim 1, wherein the plurality of slot motor laminations are inserted into the slot motor housing and the slot motor cover is placed over the plurality of slot motor laminations to electrically isolate the slot motor assembly from an arcing region.
7. The contact assembly according to claim 1, wherein the slot motor assembly is adapted to pull an arc towards the arc chute assembly during short circuit conditions thereby reducing an arc running time.
8. The contact assembly according to claim 1, wherein the slot motor assembly is designed in such a way that a maximum pull is created on the moving contact assembly.

9. The contact assembly according to claiml, wherein the plurality of slot laminations is provided with optimal length so as to reduce a negative pull on the arc.
10. The contact assembly according to claim 1, further comprises a release assembly and a knob.