FORM2
THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)
1. Title of the invention: IMPROVED MAGNETIC TRIPPING SYSTEM FOR A
CIRCUIT BREAKER.
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 circuit breaker. More Particularly, the present invention relates to an improved magnetic tripping system for a circuit breaker.
BACKGROUND AND THE PRIOR ART
The electric switching devices and circuit interrupters such as circuit breakers, motor starters, motor controllers and other load controllers are used to protect electrical circuitry and equipment from damage due to abnormal condition, such as an overload condition or a relatively high level short circuit or fault condition.
These switching devices typically have two positions corresponding to the status of the separable contacts. For example, these positions would include an ON position, in which the separable contacts are closed, an OFF position in which. the contacts are open. In a few switching device there could be a third state which would include tripped position in which the contacts are tripped open.
One such switching device is a moulded case circuit breaker (MCCB) which is generally used to provide over current protection for various types of electrical equipment. MCCBs have three stable positions - ON, OFF and TRIP in which conditions of contacts as described above. When circuit breaker is in ON condition and a short Circuit fault condition arises, high amount of current flows through the circuit and in which case circuit breaker contacts should separate to open position by sensing the fault condition through short circuit sensing mechanism such as magnetic tripping arrangement. The time taken from a fault condition appearing and the current being limited by circuit breaker determines the let through energy of the circuit interrupter. A circuit interrupter is more efficient when the let through energy is lesser.
The above mentioned short circuit sensing mechanism i.e. magnetic arrangement requires current carrying part to get assembled in the breaker, the connventional method as shown in

Fig. 1 to assemble fixed magnet 2 is with a electrically conductive component 1 where this is assembled in vertical position, 3 being a moving magnet in Fig. 1 as the breaker is working under normal condition the moving magnet is separated by fixed magnet with the help of a torsion spring whose one leg rests on moving magnet and other to some fixed position, as the short circuit fault occur the fixed magnet gives magnetic pull to moving magnet and it gets attracted towards it and trip the breaker by part of moving magnet (it can be a screw) hitting the trip bar. It can be observed clearly from the fig.l that the current carrying part used is having minimum three bending operation which consist of two 90 degree of bending and the amount of material used is also significantly large where major portion of the material is used for assembling a magnetic arrangement only. The limitation of this system is calibration or change of setting during assembly stage requires replacement of components to suit the range.
The force exerted by the fixed magnet on moving magnet depends on
a) Air gap between fixed and moving magnet
b) Spring force (spring placed between fixed and moving magnet)
c) Material of fixed magnet and moving magnet
d) Cross sectional area of fixed magnet and moving magnet
Some of the prior arts in the present field of invention are as follows:
US 6437670 provides a magnetic release system for a circuit breaker, the magnetic release system includes a contact structure; a strap configured to conduct a first level of electrical current and a second level of electrical current; a u-shaped collar having a pole face, the u-shaped collar disposed around the strap; a release lever disposed proximate the pole face, the release lever rotatably mounted on the strap; wherein the release lever is releasably engaged with the contact structure; and wherein the release lever prevents movement of the contact structure at the first level of electrical current and releases the contact structure at the second level of electrical current.

US 3936780 provides a device that comprises means for detecting, respectively, overcharges, by means of bimetallic strips and short-circuiting,/ by means of mobile magnetic plates effecting independently from each other the controlling of the switching off of a circuit-breaker for the protection of a circuit. The thermal safety means operate through a mechanical power amplifier comprising a cage with uprights, a rotating catch dependent on the thermal phase-detectors and a plunger transmitting power of a spring to effect the switching off.
US 4316163 relates to circuit breakers of a particular class, namely, the type in which a toggle is manually erected to drive a "heart" as a unit for closing the circuit breaker. The "heart" includes a contact arm, an actuator, and overcurrent releasable latch means which collectively form a normally latched unit. Under excess-current conditions, the latch means releases the actuator, and contact arm then opens the circuit. The latch means includes a conventional bimetal fixed at one end to the contact arm. The bimetal carries a pivoted latch lever, and is surrounded by a core-and-armature unit adjacent its secured end, for operating the latch lever in response to high overcurrents. High magnetic trip sensitivity is achieved in a construction wherein the whole electromagnet moves with the contact arm, without resort to a current-carrying coil for the electromagnet.
With the conventional method there is a restriction in use of magnetic tripping system for higher rating because it requires thick current carrying part and bending of that much thick current carrying part will be difficult as well as costlier process. These and other limitations and needs of the conventional magnetic arrangement necessitate an improved magnetic arrangement system. Such an arrangement has been disclosed here which overcomes the limitations and additionally provides a better flexible arrangement.
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 an improved magnetic tripping system for a circuit breaker.
Another object of the present invention is to provide Variable magnetic tripping,
Yet another object of the present invention is to reduce the copper usage by providing a compact assembly.
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 an improved magnetic tripping system for a circuit breaker.
According to one embodiment of the present invention, there is provided an improved magnetic tripping system for a circuit breaker comprising atleast one fixed magnet (2) connected to a link (1) with a screw (9); atleast one moving inagnet (3) hinged with said fixed magnet using a pin (10), other end of said moving magnet connected to said pin (10) through a pair of extension springs (5) and a pair of sockets (6); atleast one screw (7) to adjust position of said moving magnet thereby substantially varying an air gap; and atleast one trip bar for tripping said circuit breaker.
BRIEF 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.

Fig 1 illustrates the conventional magnetic system
Fig 2 illustrates the magnetic system in accordance with the present invention.
Fig 3 illustrates the exploded view of the front arrangement.
Fig 4 illustrates the side view of the arrangement. It shows no fault condition
Fig 5 and 6 illustrates side and general view of the fault condition, i.e. when the short circuit fault occur the current flowing in the circuit increased to a very high level,
Fig 7 illustrates the top view of the magnetic system.
Fig 8 illustrates the moving magnet (3) controlled with the help of knob (11). By varying the position of the knob the knob presses the moving magnet (3) thereby reducing the air gap between fixed and moving magnets. Thus the magnet can be actuated at different current levels by changing the position of the knob. Thereby offering variable magnetic setting to the user.
DETAILED DESCRIPTION OF THE INVENTION
Accordingly in the present invention an improved magnetic tripping system for a circuit breaker is provided. Magnetic system disclosed herein is shown in Fig 2. It consist of a fixed member of the magnetic system, fixed magnet 2, which is connected to the link 1 with the help of screw 9 . The moving magnet 3 is on the other side of the link hinged with fixed magnet with the help of pin 10 and other end of the moving magnet is connected to the pin 10 via two extension spring 5 and two sockets 6. Screw 7 is to adjust the position of the moving magnet to maintain specific air gap. Screw 8 is to provide proper load to the to the extension spring which will further decide at what current value fixed magnet attract moving magnet.

Fig. 2 shows the 3D view of the arrangement with link 1 as current carrying part; Fig. 3 shows the exploded view of the arrangement front, Fig. 4 shows side view of the arrangement.
The working of the invention is shown in fig. 4, 5 and 6. The same is explained below. Fig. 4 shows the normal assembled condition i.e. no fault condition. The extension spring (5) helps the moving magnet to be in that condition.
The spring load is set with the help of screw 8, as the screw rotates it pulls or pushes the socket which is not free to rotate because of its profile so it undergo linear motion and change the spring force.
As the breaker is in ON condition and the current flow through the conducting link (1), magnetic flux generates due to virtue of flow of current, but for normal current, the density of magnetic flux is not enough to provide a magnetic pull which will overcome the spring force due to spring (5), as the current increases flux density increases and when it reaches to a certain level moving magnet (3) starts attracting towards fixed magnet (2). On the moving magnet (3), a screw (7) is connected; the part of the screw (7) is connected to the trip bar, the movement of moving magnet hits the trip bar which in turn trips the circuit breaker.
The amount of current required to attract the moving magnet towards fixed magnet depend upon factors like air gap between both the magnets which will depend upon the screw 7 , as the screw turn the gap changes, it also depend upon the thickness of both moving as well as fixed magnet, as the cross section of fixed magnet increase reluctance gets decrease and attraction of fixed magnet occur early with less current, the cross section of the magnet is fixed during the design stage only so the attraction force exerted by the magnets can be varied by changing the load exerted by counter springs (5) and the dependency is highly on the force given by the extension spring (5) i.e. if the force given by spring is increased the current required to trip the breaker will also get increased so this arrangement can be used for wide range of breaker by changing the pre extension of spring.

Fig. 5 and 6 shows side and general view of the fault condition, i.e. when the short circuit fault occur the current flowing in the circuit increased to a very high level, as the current increased flux density also increase and it will provide magnetic pull to the moving magnet, it attracts towards the fixed magnet against the extension spring. As the moving magnet moves, the screw on the other side of the moving magnet is connected to the trip plate which further hit the trip plate and will trip the MCCB.
Within same frame various ranges of Circuit breakers are offered. In such case various parameters like air gap, spring, material cross section etc is varied to offer different ranges in same frame size circuit breakers. This invention discloses the method by which all the components used will be standardized. The air gap can be varied using the screw (7). The force can be varied by varying the tension on springs (5), these springs are connected to moving magnet (3) with the help of roller (3) and screws (8). As the screws are tightened or loosen, the tension on springs can be varied. Thus by adjusting the calibration screws (7) & (8), the threshold level at which the magnetic release will operate can be varied. Thus same components can be used for different rating circuit breakers thus standardizing the components.
For variable magnetic release in which the customer can change the setting of the magnetic release, In such releases, the position of the moving magnet (3) can be controlled with the help of knob (11) as shown in fig 8. By varying the position of the knob the knob presses the moving magnet (3) thereby reducing the air gap between fixed and moving magnets. So the tripping threshold can be changed. The control of the knob remains with the customer so the customer gets variable magnetic system.
The said invention is easy to calibrate in the factory at the same time multiple magnet assemblies can be placed together and tested simultaneously (pre-calibration) thus minimizing overall calibration and testing time.

In present invention the variable magnetic tripping feature is configured with ease by only tightening the screw and changing the spring force. The components required to achieve the magnetic tripping are simplified to a great extent.
Thus the above disadvantages of the prior methods can be avoided as the usage of copper is reduced, manufacturing time get reduced, assembly becomes easy, calibration become easy, and magnetic arrangement can be used for wide range of application without doing much changes and all this happens with reduction in dimensions and weight of the entire system.
ADVANTAGES:
1. Overall reduction in copper usage and hence green concept. The concept can be applied oh the bar type conductor (the conductor does not calls for any bending operation thereby reducing the length of the conductor size).
2. Factory Calibration is possible.
3. Simplified components construction.
4. Variable magnetic tripping, the air gap is adjusted by tightening the screw only.
5. Manufacturing time and cost will get reduced because of no bending operation of current carrying part.
6. Variable magnetic tripping by changing the air gap with a turn of knob (screws).
7. This magnetic arrangement will be used for higher rating of breaker also since it avoid bending of thick current carrying part which is otherwise a difficult process.
8. Overall ease of assembly and calibration
9. Simultaneous calibration of multiple magnets thus, minimizing overall calibration and testing time.
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. An improved magnetic tripping system for a circuit breaker comprising:
atleast one fixed magnet (2) connected to a current carrying link (1) with a screw (9);
atleast one moving magnet (3) hinged with said fixed magnet using a pin (10), other end of said moving magnet connected to said pin (10) through a pair of extension springs (5) and a pair of sockets (6);
atleast one screw (7) to adjust position of said moving magnet thereby substantially varying an air gap; and
atleast one trip bar for tripping said circuit breaker.
2. System as claimed in claim 1 wherein said screw (8) adapted to provide load to an extension spring thereby changing spring force.
3. System as claimed in claim 1 wherein said springs (5) are connected to said moving magnet through a plurality of sockets (6) and screws (8).
4. System as claimed in claim 1 wherein said screw (7) are can vary the air gap between fixed magnet (2) and moving magnet (3).
5. System as claimed in claim 1 wherein said screws are adapted to control threshold level for operating a magnetic release.

6. System as claimed in claim 1 further comprising a knob (11) adapted to control said moving magnet.
7. An improved magnetic tripping system for a circuit breaker as herein described and illustrated with respect to accompanying drawings.