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: SHIELDING OF FLUX SHIFT DEVICE
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 electrical assemblies, particularly to shielding of the flux shift device. The present invention more particularly relates to up-gradation of the short circuit breaking capacity of the molded case circuit breakers.
B) BACKGROUND OF THE INVENTION
[0002] An electrical power system consists of generators, transformers,
transmission & distribution lines, machines and the like. 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.
[0003] Typically in the 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 issues a trip command to the circuit breaker. The command is mechanically executed by using an electromagnetic device such as a 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 FSD 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 and to trip the breaker.
[0004] The upgradation of the flux shift device to handle high breaking
capacity is the biggest challenge when the circuit breaker design is upgraded for the higher breaking capacity. The increase in short circuit current

increases the magnetic flux. The higher magnetic flux reacts with the magnetic circuit of the flux shift device causing saturation of the magnetic circuit and de-magnetization of the permanent magnet. This ultimately leads to flux shift device malfunctioning.
[0005] None of the prior art discloses a method for shielding flux shift device in molded case circuit breaker. Hence there is a need to develop an improved, more reliable and high performance solutions for shielding flux shift device.
[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 INVENTION
[0007] The primary object of the present invention is to develop an improved shielding for a flux shift device.
[0008] Another object of the present invention is to develop an
improved method for protecting the magnetic circuit and the permanent magnet from demagnetization.
[0009] Another object of the present invention is to develop a compact
shielding method for flux shift device.
[0010] Yet another object of the present invention is to develop an improved shielding for flux shift device to defense in case of saturation of the magnetic material of the shield.

[0011] Yet another object of the present invention is to develop a method for fixing a shielding for flux shift device without changing the overall dimensions of the release box.
[0012] 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
[0013] The above mentioned shortcomings, disadvantages and problems are addressed herein and which will be understood by reading and Studying the following specification.
[0014] The various embodiments of the present invention provide a shield for the flux shift device. The shield is designed to protect the magnetic circuit and the permanent magnet from demagnetization without any major change in the existing design of either flux shift device or release. The shield is designed such that the shield covers the flux shift device. The electromagnetic flux during short circuit travelling from current path to the flux shift device is encountered with the shield and the shield does not allow the electromagnetic flux to reach the flux shift device. Thus it protects the magnetic circuit and permanent magnet of flux shift device from demagnetization at the same time it maintains the same compact size of flux shift device set in the release of circuit breaker.
[0015] According to an embodiment of the present invention, the material of the shield is adapted to provide least resistance to flow of electromagnetic flux through it. The thickness of the shield is selected such that the shield material does not get saturated during fault currents, for

instance during short circuit condition. The flux shift device further includes a thin insulation tape wound over the flux shift device.
[0016] According to one embodiment of the present invention, the shield is provided with at least one turn of a thin copper/aluminum shim wound over the insulation tape. The copper/aluminum shim provides for a second line of defense in case of saturation of magnetic material of shield. The thickness of the magnetic material is thus reduced by using thin shim of copper/aluminum. The shield from the outer side is insulated with the help of an insulation tape.
[0017] According to an embodiment of the present invention, the cavity holding for flux shift device is removed with the help of extra operation like milling. The plain cavity within the release box is now used to accommodate the shield. This provides to avoid any new tooling investment and to reuse the existing component.
[0018] According to another preferred embodiment, the shielded flux shift device is placed inside the release box. Further, the wings on the shield are bent. After bending, the wings are insulated using an insulation placed on the wings of the shield. The arrangement forms permanent placement of the flux shift device along with shield with least efforts.
E) BRIEF DESCRIPTION OF THE DRAWINGS
[0019] 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:
[0020] FIG. 1 is a prior art diagram illustrating a flux shift device placed inside the release box without a shield mechanism.

[0021] FIG. 2 illustrates the flux shift device without the shield according to one embodiment of the present invention.
[0022] FIG. 3 illustrates the flux shift device with the shield according to another embodiment of the present invention.
[0023] FIG. 4 illustrates the shielded flux shift device placed inside the release box with the wings on the shield in a bend condition, according to an embodiment of the present invention.
[0024] FIG. 5 illustrates the shielded flux shift device placed inside the release box and insulated wings on the shield according to yet another embodiment of the present invention.
[0025] 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
[0026] 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.

[0027] The various embodiments of the present invention provide a shield for a flux shift device. The shield is adapted to protect the magnetic circuit and the permanent magnet from demagnetization without any major change in the existing design of either flux shift device or release. The shieJd covers the flux shift device and the electromagnetic flux during short circuit travelling from current path to the flux shift device is encountered with the shield and prevents the electromagnetic flux from reaching the flux shift device. The shield protects the magnetic circuit and permanent magnet of flux shift device from demagnetization and also maintains the same compact size of flux shift device set in the release of circuit breaker.
[0028] FIG. 1 is a prior art diagram illustrating a flux shift device placed inside the release box without a shield mechanism. As shown in FIG. 1, a cavity 3 is provided inside the release box 1 which forms integral part of release box 1. A flux shift device 2 is placed inside the cavity 3. During short circuit condition, the increase in short circuit current increases the magnetic flux. This higher magnetic flux reacts with the magnetic circuit of flux shift device 2 causing saturation of magnetic circuit and de-magnetization of the permanent magnet. This ultimately leads to flux shift device 2 malfunctioning.
[0029] FIG. 2 illustrates a flux shift device without the shield according to one embodiment of the present invention. FIG. 3 illustrates the flux shift device with the shield according to another embodiment of the present invention. The flux shift device assembly 2 is as shown in FIG. 2. The material of the shield 4 is chosen such a way that it offers least resistance to the flow of electromagnetic flux through the shield. The thickness of the shield 4 is chosen to such a value that the shield material does not get saturated during short circuit condition. A thin insulation tape is wound over the flux shift device assembly 2. Over this flux shift device

assembly 2 one turn of thin copper/aluminum shim is wound. The copper/aluminum shim acts as a second line of defense in case of saturation of magnetic material of shield 4. The thickness of magnetic material can be further reduced by using a thin shim of copper/aluminum. The flux shift device assembly 2 is placed inside the shield 4. The shield 4 from the outer side is insulated using an insulation tape 6 as shown in FIG. 3.
[0030] FIG. 4 illustrates the shielded flux shift device placed inside the release box and the wings on the shield are bent according to yet another embodiment of the present invention. FIG. 5 illustrates the shielded flux shift device placed inside the release box and the wings on the shield after bending are insulated according to yet another embodiment of the present invention. The cavity 3 holding the flux shift device 2 is removed with the help of extra operation like milling. The plain cavity 3 within the release box 1 can be used to accommodate the shielded flux shift device 301.
[0031] The shielded flux shift device 301 is placed inside the release box 1 and the wings 5 on the shield 4 are bent as shown in FIG. 4. The arrangement forms permanent placement of flux shift device 2 along with shield 4 with least efforts. The wings 5 after bending are insulated using insulation 7 placed on the wings 5 of the shielded flux shift device 301 assemblies as shown in FIG. 5. The insulation on wings helps in avoiding flashover failures (electrical fault).
G) ADVANTAGES OF THE INVENTION
[0032] The present invention provides a shield for a flux shift device. The shield makes the device compact enough, easy to assemble and highly reliable since existing components are re-used. The components for shielding

the flux shift device are easy to manufacture and process. Also the shielded flux shift device can be adapted for any circuit breaker.
[0033] The breaking capacity of the circuit breaker is upgraded without any major redesigning. The existing components are re-used thereby saving design/tooling and execution cost. The shielded FSD can be adapted for any circuit breaker and provides for high breaking capacity.
[0034] With the present invention the life of the flux shift device is
enhanced and the total dimension of the upgraded circuit breaker remains same as earlier.
[0035] 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.
[0036] 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 shield for a Flux Shift Device (FSD) comprising:
a sheet metal; and
an insulation material placed on the sheet metal; Wherein the shield is provided with a preset profile to enclose the FSD such that the shield encounters an electromagnetic flux during a short circuit from a current path to the FSD thereby preventing the electromagnetic flux to reach the FSD.
2. The shield according to claim 1, wherein the sheet material of the shield is chosen so as to offer least resistance to flow of electromagnetic flux.
3. The shield according to claim 1, wherein of a thickness of the sheet metal is chosen to such a value that the shield material does not get saturated during short circuit condition.
4. The shield according to claim 1, further comprising a thin insulation tape is wound over the flux shift device.
5. The shield according to claim 4, wherein one turn of a thin copper
shim is provided over the flux shift device with the thin insulation
tape such that the copper shim acts as second line of defense in case
of saturation of magnetic material of the shield.
6. The shield according to claim 4, wherein one turn of a thin
aluminum shim is provided over the flux shift device with the thin
insulation tape such that the aluminum shim acts as second line of
defense in case of saturation of magnetic material of the shield.

7. The shield according to claim 1, wherein the shielded flux shift device is placed inside a cavity within a release box.
8. The shield according to claim 1, wherein the cavity holding for the
flux shift device in the release box is removed by milling to reuse the existing component.
9. The shield according to claim 6, wherein the sheet metal includes
least two wings so as to bend the sheet metal for fixing the shield inside the release box firmly.
10. The shield according to claim 8, wherein the wings are insulated
using an insulation placed on the wings of the shield after
bending the wings on the release box.