FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)
1. Title of the invention. - AN IMPROVED ELECTROMAGNETIC RELEASE
FOR USE IN CIRCUIT BREAKERS.
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 electromagnetic release for use in circuit breakers. More particularly, the invention is concerned about an improved electromagnetic release for use in circuit breakers for faster contact opening.
BACKGROUND OF THE INVENTION
Miniature circuit breakers (MCBs) are used in industrial and domestic applications to provide the protection against overload and short circuit currents .MCB works on the concept of current limiting which means limiting the value of current in case of short circuit fault to a lower value as compared to its prospective value.
In a typical MCB construction, effective current limiting is achieved by opening the circuit breaker contacts by means of electromagnetic release which is also known as solenoid .The release normally has a movable component that either pushes or pulls the MCB contact under fault conditions.
Under short circuit fault conditions it is of utmost importance to open the contacts early because if the contact opening is delayed then it results in high let - through energy being passed to downstream devices thereby causing severe thermal and mechanical stresses.
In an electrical installation, miniature circuit breakers are employed to provide the protection against overload and short circuit fault conditions. From system safety point of view, the effective current limiting achieved and let through energy delivered by MCB to downstream devices shall be maintained as low as possible which calls for reduction in the total ON Time. ON time is the time elapsed between the instant of occurrence of an electrical fault to the instant the breakers comes to final isolation state. In a typical MCB, the contact opening time is one of the main constituent of total ON Time.

US 5894257 discloses an electromagnetic trip for an electrical switch apparatus for protecting against short circuits, including a magnetic yoke, a tubular nonmagnetic coil form with axis X-X', open at both ends, a control coil wound around the form, a fixed core and a movable core which are housed in the respective ends of the form, the movable core having an upper end projecting outside the form, characterized in that the form, the coil, the fixed core and the movable core constitute a pre-assembled electromagnetic sub-assembly intended to be introduced into the magnetic yoke.
US 6577217 discloses a magnetic sub-assembly for modular electrical equipment of the circuit-breaker type includes a yoke having a leg at least partially integrated inside the inner volume of an induction coil so that a range of axial dimensions of the coil is allowed by the yoke, and one end of the coil is oriented so that its attachment to a fixed contact also allows the range of axial dimensions.
US 7528690 discloses an electrical switching device, having a thermal release, an electromagnetic release, and a switching mechanism with a latching point. A contact base for moving a contact member is located between the thermal release and the electromagnetic release. The thermal release is coupled to a release lever by means of a connecting rod passing over the contact base so that both the thermal release and the electromagnetic release open the latching point in the event of an over current and/or short-circuit current.
US 20080018422 discloses a switching equipment comprising a housing, at least one contact point that has a fixed and mobile contact part and an electromagnetic trip device comprising a trip coil and a trip armature. Said equipment is wherein the trip armature is configured from a material with magnetic shape memory properties. According to the invention, when a short-circuit occurs, the trip armature is deformed by the influence of the magnetic field of the trip coil, thus causing the contact point to open.

The disadvantages of the conventional release is such that there is a limitation of achieving early contact opening at the time of short circuit fault because there is a single moving core responsible for contact opening at low magnetic tripping currents as well as at short circuit currents.
Thus, there is a need to overcome the problems of the prior art. Therefore, present inventors have developed an improved electromagnetic release for use in circuit breakers for faster contact opening.
OBJECTS OF THE INVENTION
An object of the present invention is to overcome the problems/disadvantages of the prior art.
Another object of the present invention is to provide an improved electromagnetic release for use in circuit breakers.
These and advantages of the present invention will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings.
SUMMARY OF THE INVENTION
The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the present invention. It is not intended to identify the key/critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concept of the invention in a simplified form as a prelude to a more detailed description of the invention presented later.
The present invention relates to an improved electromagnetic release for use in the circuit breakers for faster opening of the contacts.

According to one aspect of the present invention, there is provided an improved electromagnetic release mechanism for use in circuit breakers, said mechanism comprising:
a frame means;
a hollow component provided inside said frame means wherein said hollow
component being adapted to maintain all other internal components of the said
release mechanism in alignment with each other;
plural movable core means comprising a first moving element and a second
moving element located in proximity to each other having a predetermined space
between them
a substantially cylindrical element being fixed to said frame means in a manner
that said cylindrical element is stationary;
wherein said first moving element being adapted to trip the mechanism
wherein said second moving element comprising a hole axially located in it;
means for contacting said moving element 2 with moving contact of the said
circuit breaker, said means for contacting being movably disposed inside said
axial hole;
priming means located between said first moving element and said second moving
element
wherein during magnetic tripping an attraction force is generated between said
moving element 1 and said moving element 2 due to flux flow working against
said priming means subsequently causing movement of said moving element 1
thereby giving a tripping signal to the circuit breaker
wherein during short circuit tripping, an attraction force is produced between the
moving element 2 and the stationary element due to flux flow which subsequently
causes instant opening of the moving contact by transmitting the force through the
said contacting means.

DETAILED DESCRIPTION OF THE INVENTION
According to the invention there is provided an improved electromagnetic release for use in circuit breakers. The present invention describes the concept of an improved electromagnetic release in miniature circuit breakers. More precisely this invention uses a dual moving core construction of electromagnetic release which provides early contact opening in miniature circuit breakers and subsequently minimizes "let through energy". In the present invention, the magnetic tripping and short circuit tripping is achieved by adapting a dual moving core construction. One moving core is only responsible for magnetic tripping and the other is responsible for providing impact force on moving contact of breaker in short circuit fault condition. Further fast contact opening velocity is achieved by utilizing the impact force of one moving part over the other. This also ensures minimum damage to the circuit breaker because of reduction in thermal and mechanical stresses inside the breaker and hence increasing the life of MCB. The present invention is equally suitable for MCB constructions that employ single break or multi break contact systems.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Other features as well as the advantages of the invention will be clear from the following description.
In the appended drawings:
Fig. 1 illustrates a cut view of electromagnetic release for fast contact opening.
Fig. 2 illustrates a cut view of electromagnetic release in normal current condition.
Fig. 3 illustrates a cut view of electromagnetic release in case of magnetic tripping.

Fig. 4 illustrates a cut view of electromagnetic release in case of short circuit tripping.
DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS
In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and illustrate the best mode presently contemplated for carrying out the invention. Further functioning of the mechanism has been discussed below to describe the way the mechanism operates. However, such description should not be considered as any limitation of scope of the present unit. 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.
According to a preferred embodiment of the invention, there is provided an improved electromagnetic release for use in circuit breakers. Figure 1 shows a cut view of electromagnetic release for fast contact opening.
Figure 2 describes the initial open condition of the release in case of rated circuit breaker current flowing through the coil (5) .Here with low value of current the electromagnetic force produced in moving core 1 (1) is low in magnitude as compared to the resetting force of compression spring(7). Also force acting on moving core 2 (2) is not sufficient to move it against the opposition force offered by circuit breaker contact. Hence, in case of rated current flow or in case of healthy circuit conditions both the moving cores will remain stationary so circuit breaker contacts will continue to carry load current.
Figure 3 describes the state of release in case of magnetic tripping current. International Circuit breaker standards define the magnetic tripping currents of circuit breakers. In case of magnetic tripping, an attraction force is developed between moving core 1 (1) and moving core 2 (2) due to flux flow which works

against the resetting spring(7) and cause subsequent movement of moving core 1 (1). This gives a tripping signal to mechanism for circuit breaker mechanism delatching. In this condition the opposition force on moving core 2 (2) is high enough to restrict any movement of it.
Figure 4 illustrates a cut view of electromagnetic release in case of short circuit tripping. In case of short circuit a high amount of current flows through the breaker, hence release coil (5) is also energized with this high current, causing a high amount of flux passing through the magnetic circuit of release. In this condition, moving core 1 (1) and moving core 2 (2) both has sufficient force developed and movement of moving corel (1) and moving core (2) starts. Since pin (8) is in direct contact with moving core 2 (2) because of interlock (10), pin (8) movement and hence circuit breaker contact separation starts at the same instant. This results in early contact opening without any effect on circuit breaker tripping in case of magnetic tripping.
In case of conventional release, there is only one moving core and mechanism tripping in case of low current calls for a gap between the moving core and pin. In case of short circuit tripping this gap is to be covered by moving core before it pushes pin to cause contact opening .So the disadvantage with conventional release is the inherent delay. In the improved design, the gap is maintained between moving core 1 (1) and pin (8) to facilitate mechanism tripping at low currents and at the same time early contact opening under short circuit fault condition is achieved through the movement of moving core2 (2) and transferring the force to moving contact of circuit breaker by utilizing an interlock (10) and a pin (8).
Working example:
A FEA analysis of this improved release and conventional release has been carried out. A significant improvement wrt the time at which contacts start opening is observed in the present invention.

ADVANTAGES OF THE INVENTION
1. Early contact opening without affecting magnetic tripping.
2. Reduction in cut off current and let through energy
3. Increase in breaker life due to lower thermal and mechanical stresses
Constructional Elements:
1. Moving Element/Core 1 (1) : It is the first moving element of release having cylindrical shape and which performs the function of mechanism tripping at magnetic tripping current and facilitate faster contact opening in the event of short circuit fault
2. Moving Element/Core2 (2): It is the second moving element of release, having cylindrical shape and an axial hole for passage of pin (8). It is connected to the moving contact of circuit breaker via a pin (8) and applies force on moving contact of breaker in case of short circuit fault.
3. Fixed Core (3): It is the stationary cylindrical element of release.
4. Frame (4): A substantially C-shaped frame is used for providing easy path for flux flow which provides advantage in terms of material saving and process cost as compared to commonly used D -shaped construction
5. Coil (5): A conductive coil is used to generate strong magneto motive force in the event of overcurrent.
6. Bobbin (6): It is a cylindrical hollow component provided to keep all internal components of the release in line to each other. The basic function of this component is to provide a channel for the movement of all movable parts of release. The other function of this bobbin is to act as a stopper for moving core 1(1) and moving core 2 (2).

7. Priming means/Spring (7): A compression spring is placed between
moving core 1 (1) and moving core2 (2) which resets the moving core 1
(1) when coil gets de energized in case fault is cleared by circuit breaker.
8. Pin (8): It transmits the force produced in moving core2 (2) to the moving contact of circuit breaker.
9. Stopper (9): It is a light weight component placed between the moving core 1 (1) and moving core 2 (2). The main function of this component is to maintain a higher air gap between moving core 1(1) and moving core 2
(2) so that the total force on moving core 2 (2) is in the direction to assist
contact opening throughout the travel of moving core 2 (2).
10. Interlock (10): It is the integral part of the pin. It is in continuous contact
with moving core 2 (2). The movement of pin and of contact of circuit
breaker in case of movement of moving core 2 (2) is achieved by keeping
interlock in contact with moving core 2 (2)

WE CLAIM:
1. An improved electromagnetic release mechanism for use in circuit
breakers, said mechanism comprising:
a frame means;
a hollow component provided inside said frame means wherein said
hollow component being adapted to maintain all other internal components
of the said release mechanism in alignment with each other;
plural movable core means comprising a first moving element and a
second moving element located in proximity to each other having a
predetermined space between them
a substantially cylindrical element being fixed to said frame means in a
manner that said cylindrical element is stationary;
wherein said first moving element being adapted to trip the mechanism
wherein said second moving element comprising a hole axially located in
it;
means for contacting said moving element 2 with moving contact of the
said circuit breaker, said means for contacting being movably disposed
inside said axial hole;
priming means located between said first moving element and said second
moving element
wherein during magnetic tripping an attraction force is generated between
said moving element 1 and said moving element 2 due to flux flow
working against said priming/charging means subsequently causing
movement of said moving element 1 thereby giving a tripping signal to the
circuit breaker.
wherein during short circuit tripping, an attraction force is produced
between the moving element 2 and the stationary element due to flux flow
which subsequently causes instant opening of the moving contact by
transmitting the force through the said contacting means.

2. Mechanism as claimed in claim 1 wherein said frame means is substantially C shaped.
3. Mechanism as claimed in claim 1 wherein said hollow component is substantially cylindrical providing channel means for movement of all movable components/parts of said release mechanism.
4. Mechanism as claimed in claim 1 wherein said hollow component additionally acts as stopper for moving element 1 and moving element 2.
5. Mechanism as claimed in claim 1 wherein said means for contacting said moving element 2 with moving contact comprising a pin means.
6. Mechanism as claimed in claim 1 wherein said pin means comprising an integrated interlocking means in continuous contact with moving element 2.
7. Mechanism as claimed in claim 1 further comprising coil means.
8. Mechanism as claimed in claim 1 wherein said priming/charging means comprising a spring means.
9. Mechanism as claimed in claim 8 wherein said spring means is a compression spring.
10. Mechanism as claimed in claim 1 wherein said cylindrical element is a fixed core.
11. Mechanism as claimed in claim 1 further comprising a stopper means
adapted to maintain a higher air gap between moving element 1 and
moving element 2 such that the total force on moving element 2 is in the
direction to assist contact opening throughout the travel of moving element
2.

12. An improved electromagnetic release mechanism for use in circuit breakers as herein described and illustrated with respect to the accompanying drawings.