FORM2
THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)
1. Title of the invention - SHIELDED FLUX SHIFT DEVICE ASSEMBLY 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:

TECHNICAL FIELD OF THE INVENTION
This invention relates generally to a flux shift device henceforth termed as FSD and more particularly to a shielded flux shift device assembly for use in circuit breakers.
BACKGROUND AND THE PRIOR ART
An electrical power system consists of generators, transformers, transmission & distribution lines, machines etc. Short circuit and other abnormal conditions often occur on a power system. The heavy current associated with the short circuits is likely to cause damage to equipment if suitable protective relays and circuit breakers are not provided for the protection of each section of the power system. In a protective system the fault is detected by the device and a command is issued to the circuit breaker to disconnect the faulty element. The unhealthy condition is sensed by the Electronic release and trip command is issued to the circuit breaker. This command is mechanically executed using an electromagnetic device such as FLUX SHIFT DEVICE (FSD), which contains a permanent magnet as a fixed part and a plunger of magnetically permeable material as a moving part. When this device receives an actuating signal (electrical signal) from the electronic release an operating force is developed which is applied on the moving part. This causes the moving part to pop-out (travel) and to trip the breaker. Presently FSD is mounted in the release as shown in the figure1. As seen from the figure 1, a cavity has been provided inside the release box which forms integral part of release box. FSD is placed inside this cavity.
When the circuit breaker design was upgraded for higher breaking capacity, upgrading the FSD to handle high breaking capacity was the biggest challenge. The increase in short circuit current increases the magnetic flux. This higher magnetic flux can react with the magnetic circuit of FSD causing saturation of magnetic circuit and

de-magnetization of the permanent magnet. This ultimately leads to FSD malfunctioning. The FSD without shielding is as shown in figure 2.
Thus there is a need to develop a shield assembly in order to protect the magnetic circuit and permanent magnet from demagnetization without any major change in the existing design of either FSD or release. Therefore, the present invention provides for a shielded flux shift device assembly for use in circuit breakers that would prevent the magnet from demagnetization and would lead to up-gradation of short circuit breaking capacity of the MCCB.
OBJECTS OF THE INVENTION
A basic object of the present invention is to overcome the disadvantages/drawbacks of the known art.
Another object of the present invention is to provide a shielded flux shift device assembly for use in circuit breakers to prevent the magnet from demagnetization.
Another object of the present invention is to up-grade short circuit breaking capacity of the MCCB.
Another object of the present invention is to maintain the same compact size of FSD set.
Another object of the present invention is to form permanent placement of FSD along with shield with least efforts.
Another object of the present invention is to provide the shielded FSD that can be adapted to any circuit breaker.

Yet another object of the present invention is to provide a shield so that the life of the FSD is enhanced.
These and other advantages of the present invention will become readily apparent from the following detailed description read in conjunction with the accompanying drawings.
SUMMARY OF THE INVENTION
There is provided a shielded flux shift device assembly for use in circuit breakers.
According to one embodiment of the present invention, there is provided a shielded flux shift device assembly for use in circuit breakers to prevent the magnet from demagnetization.
Other embodiment of the present invention provides for up-grading short circuit breaking capacity of the MCCB.
Other embodiment of the present invention provides for the same compact size of FSD set.
Other embodiment of the present invention provides for permanent placement of FSD along with shield with least efforts.
Other embodiment of the present invention provides for the shielded FSD that can be adapted to any circuit breaker.
Yet other embodiment of the present invention provides for a shield so that the life of the FSD is enhanced.

In addition, Breaking capacity of the circuit breaker can be upgraded without major redesign thus saving design/tooling and execution cost. Also the existing components can be re-used. The new components are easy to manufacture and process. The shielded FSD can be adapted for any circuit breaker (ready solution for circuit breakers with very high breaking capacity). The life of the FSD is enhanced. The total dimension of the upgraded circuit breaker remains same as earlier.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
In the appended drawings:
FIG 1 illustrates a general arrangement of FSD placed inside the release box.
FIG 2 illustrates FSD assembly.
FIG 3 illustrates an exploded view of FSD componetns placed inside shield.
FIG 4 illustrates a shielded FSD assembly.
FIG 5 illustrates an exploded view of shielded FSD and componetns placement inside release box.
FIG 6 illustrates a shielded FSD and componetns placed inside release box.
FIG 7 illustrates fastners of FSD shield insulated for electrical safety.

DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The following drawings are illustrative of particular examples for enabling methods of the present invention, are descriptive of some of the methods, and are not intended to limit the scope of the invention. The drawings are not to scale (unless so stated) and are intended for use in conjunction with the explanations in the following detailed description.
Reference is first invited to Fig 1 where general arrangement of FSD placed inside the release box. A cavity has been provided inside the release box which forms integral part of release box. FSD is placed inside this cavity.
Fig 2 shows FSD assembly. The FSD assembly shown is without shielding.
Fig 3 shows an exploded view of FSD componetns placed inside shield. The shielded FSD is mounted in the release.
Fig 4 shows a shielded FSD assembly. It shows shield, slot for rivetting and FSD assembly.
Fig 5 shows an exploded view of shielded FSD and componetns placement inside release box. The modified release housing has four slots and counter slots present in the shield.
Fig 6 shows a shielded FSD and componetns placed inside release box. The fasteners are placed inside the shield assembly and the rivets are formed thereby forming a firm joint assembly.

Fig 7 shows fasteners of FSD shield insulated for electrical safety. The insulation on fasteners helps in avoiding flashover failures (electrical fault).
The invented system is thus a shielded flux shift device assembly for use in circuit breakers.
DETAILED DESCRIPTION OF THE INVENTION
Accordingly in the present invention there is provided a shielded flux shift device assembly for use in circuit breakers. The shielded FSD is mounted in the release as shown in the figure 3. The shield assembly covers the FSD, the electromagnetic flux during short circuit travelling from current path to the FSD is encountered with the shield and the shield does not allow the electromagnetic flux to reach the FSD. Thus it protects the magnetic circuit and permanent magnet of FSD from demagnetization at the same time it maintains the same Compact size of FSD set in the release of circuit breaker.
Figure 4 shows a shielded FSD assembly. The material of the shield is chosen such a way that it offers least resistance to flow of electromagnetic flux through it. At the same time the thickness of the shield is chosen to such a value that the shield material does not get saturated during worst case scenario (short circuit condition). A thin insulation tape is wound over the FSD. Over this assembly one turn of thin shim of high conductivity material may be wound. This shim acts as second line of defense in case of saturation of magnetic material of shield. (Thus the thickness of magnetic material can be reduced further by using thin shim of high conductivity material). This assembly is placed inside the shield. The shield from the outer side is insulated with the help of insulation tape. Thus a shielded FSD assembly is ready to be assembled in the release assembly.

The modified release housing has four slots and counter slots are present in the shield. The fasteners are placed inside the shield assembly and the rivets are formed thereby forming a firm joint assembly as shown in figures 5 and 6.
The housing assembly can now be used to assemble the release as usual. This arrangement forms permanent placement of FSD along with shield with least efforts. The rivets after forming are insulated with the help of insulation as shown in figure 7. The insulation on fasteners helps in avoiding flashover failures (electrical fault).
Although the embodiments herein are described with various specific embodiments, it will be obvious for a person skilled in the art to practice the embodiments herein with modifications. However, all such modifications are deemed to be within the scope of the claims.
It is also to be understood that the following claims are intended to cover all of the generic and specific features of the embodiments described herein and all the statements of the scope of the embodiments which as a matter of language might be said to fall there between.

WE CLAIM:
1. A flux shift device (FSD) for use in circuit breakers, said device comprising:
a shield being mounted in a conventional release assembly adapted to prevent electromagnetic flux reaching FSD wherein said shield being insulated from outside by means of insulation tape.
2. Device as claimed in claim 1 comprising at least a turn of thin shim of high conductive material wound on the FSD to trap the electromagnetic flux reaching the FSD after saturation of shield thereby reducing the thickness of the shield.
3. Device as claimed in claim 1 and 2 wherein said shield having a thickness such that it does not get saturated during short circuit condition or the like.
4. Device as claimed in claim 1 and 2 wherein said shield comprising plural slots so as to get fastened with said release assembly.
5. Device as claimed in claim 3 wherein the fasteners are insulated with the help of insulation.
6. Device as claimed in claim 1 wherein said tape means is a thin insulation tape.
7. A flux shift device assembly for use in circuit breakers as herein substantially described and illustrated with reference to the accompanying drawings.