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 MAGNETIC TRIPPING SYSTEM FOR CIRCUIT PROTECTION
DEVICE
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 tripping system and more particularly to an improved magnetic tripping system for circuit protection device for instantaneous tripping done magnetically with minimum usage of copper.
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 equipments 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 condition of contacts is 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 conventional method as shown in Fig. 1 to assemble fixed magnet 2 is with a electrically conductive component 1 (heater) 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 plate, it can be observed clearly from the fig. 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.
US 6437670 discloses 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 discloses a device 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 the power of a spring to effect the switching off.
US 4316163 discloses 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 over-current. 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.
The disadvantages of the conventional methods are such that 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.
Thus, there is a need to overcome the problems of the prior art. Therefore, the present invention provides for an improved magnetic tripping system for circuit protection device which would reduce the copper usage and manufacturing time.
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 an improved magnetic tripping system for circuit protection device.

Another object of the present invention is to provide for instantaneous tripping done magnetically with minimum usage of copper.
Another object of the present invention is to provide for less manufacturing and assembly cost.
Yet another object of the present invention is to provide for a simplified magnetic tripping.
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 circuit protection device.
According to one embodiment of the present invention, there is provided an improved magnetic tripping system for use in circuit breakers, said system comprising:
a link means;
a fixed magnet screwably or permanently engaged to said link means on its one side;
a moving magnet being located proximal to said link means on its other side defining a desired air gap;
a pin means so as to define a linkage between said moving magnet and a trip bar;

wherein said moving magnet communicates with said link means by means of plurality of guiding means
wherein said guiding means being loaded with biasing means such that moving magnet is movable towards and away from said link means and wherein during short circuit condition movement of said moving magnet corresponding to increased magnetic field trips the circuit breaker.
Other embodiment of the present invention provides for less manufacturing and assembly cost.
Yet other embodiment of the present invention provides for a simplified magnetic tripping.
In addition, the present invention provides for easy calibration and assembly, variable magnetic tripping and reduced manufacturing time. Also the 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 thus making it compact. The invention disclosed here is a green product concept.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
In the appended drawings:
Fig 1 illustrates a conventional method of circuit breaker arrangement.
Fig 2 illustrates a 3D view of an arrangement.
Fig 3 illustrates a front view of a normal assembled condition.

Fig 4 illustrates an exploded view of an arrangement.
Fig 5 illustrates a front view of the fault condition.
Fig 6 illustrates a general view of the fault condition.
Fig 7 illustrates a variable magnetic release of the arrangement.
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 the conventional method of circuit breaker arrangement is shown. It shows conducting link (1), fixed magnet (2) and moving magnet (3).
Fig. 2 shows a 3D view of the arrangement. It shows all the components namely conducting link (1), fixed magnet (2), moving magnet (3), rivets (4), compression spring (5), a pin (6), part of pin connected to the trip bar (7), screw {8) and the knob (9).
Fig 3 shows the normal assembled condition i.e. no fault condition. The compression spring (5) in that condition has only the load of moving magnet (3) with no magnetic pull.
Fig 4 shows the exploded view of the assembly as discussed in fig 2 and 3.

Fig 5 shows the working of the assembly during fault condition. In this figure only the front view of the assembly is shown.
Fig 6 shows the general view of the fault condition. As the moving magnet moves it compress the spring, the pin on the other side of the moving magnet is connected to the trip plate which further pulls the trip plate and will trip the breaker.
Fig 7 shows the variable magnetic release of the arrangement. 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 9 above the moving magnet.
The invented system is thus an improved magnetic tripping system for circuit protection device.
DETAILED DESCRIPTION OF THE INVENTION
Accordingly in the present invention there is provided an improved magnetic tripping system for circuit protection device. Figure 2 shows magnetic system consist of a fixed member of the magnetic system, fixed magnet 2, which is connected to the link 1 with the help of a screw 8 . The moving magnet 3 is on the other side of the link guided by two pins or screw 4 and the compression spring 5 in between them such that it will remain at constant distance from link under normal condition. The moving magnet is connected to the pin 6 which is further connected to the trip bar. Figure 2 shows the 3D view of the arrangement with link 1 as current carrying part, figure 3 shows front view of the arrangement and figure 4 shows the exploded view of the arrangement.
The working of the invention is shown in figures 5 and 6. Figure 3 shows the normal assembled condition i.e. no fault condition. The compression spring (5) in that condition has only the load of moving magnet (3) with no magnetic pull. The force

given by compression spring (5) is more than that of the weight of moving magnet (3) so the spring push the moving magnet above and it will move up and rest on the pin (8) where pin is also acting as a stopper for moving magnet in addition to guide it.
As the breaker is in ON condition and the current flows through the conducting link (1), magnetic field generates due to virtue of flow of current. For normal current, the intensity of magnetic field is not enough to provide a magnetic pull which will overcome the spring force due to spring (5). As the current increases magnetic field intensity increases and when it reaches to a certain level moving magnet (3) starts attracting towards fixed magnet (2). On the moving magnet (3), a pin (6) is connected; the part of the pin (7) is connected to the trip bar, the movement of moving magnet results into pulling of trip bar which in turn trips the circuit breaker.
The amount of current required to attract the moving magnet towards fixed magnet depend upon many factors like air gap between fixed magnet and moving magnet. The air-gap depends upon the free length of the compression spring (5), as the free length of the spring decrease the gap between fixed and moving magnet will decrease and attraction will occur in low current value so the free length of spring will decide the current level in which the short circuit protecting device will activate and trip the breaker, in this case the compression spring is of constant rate so the air gap can be adjusted by the movement of moving magnet because the force given by spring will remain constant, 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, and the dependency is highly on the force given by the compression spring 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 spring force and air gap.

Figures 5 and 6 show front 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 increases magnetic field intensity also increases and it will provide magnetic pull to the moving magnet, it attracts towards the fixed magnet against the compression spring. As the moving magnet moves compresses the spring, the pin on the other side of the moving magnet is connected to the trip plate which further pulls the trip plate and will trip the breaker.
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 9 above the moving magnet shown in figure 7. By changing the position of the knob (9) the actuation point of the knob will press the moving magnet (3) thus reducing or increasing the air gap between the fixed and moving magnets. Thus variable magnetic release can be produced with ease.
In the present invention, the variable magnetic tripping feature is configured with ease by only tightening the screw and changing the air gap between fixed and moving magnet without changing the spring force as it is of constant rate. The components required to achieve the magnetic tripping are simplified to a great extent.
Thus 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. Therefore the invention disclosed here is a green product concept.
Afthough 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 a\l 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 use in circuit breakers, said system comprising:
a link means (1);
a fixed magnet (2) screwably or permanently engaged to said link means (1) on its one side;
a moving magnet (3) being located proximal to said link means on its other side defining a desired air gap;
a pin means (6) so as to define a linkage between said moving magnet (3) and a trip bar;
wherein said moving magnet communicates with said link means by means of plurality of guiding means (4)
wherein said guiding means (4) being loaded with biasing means (5) such that moving magnet is movable towards and away from said link means and wherein during short circuit condition movement of said moving magnet corresponding to increased magnetic field trips the circuit breaker.
2. A system as claimed in claim 1 wherein said biasing means comprising compression springs.
3. A system as claimed in claim 2 wherein said compression spring having a constant rate providing variable magnetic tripping feature by changing the air gap between said moving magnet and said fixed magnet.

4. A system as claimed in claim 1 wherein said guiding means comprising pins.
5. An improved magnetic tripping system for circuit protection device as herein substantially described and illustrated with reference to the accompanying drawings.