FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
COMPLETE SPECIFICATION
(See section 10 and rule 13)
1. TITLE OF THE INVENTIONARRANGEMENT OF MAGNETIC CLADDING FOR ELECTRICAL SWITCHING DEVICE
2. APPLICANT(S)
(a) NAME : Larsen and Toubro Ltd.
(b) NATIONALITY: Indian
(c)ADDRESS : L&T House, Ballard Estate, Mumbai-400 001, India.
3. PREAMBLE TO THE DESCRITION
COMPLETE
The following specification particularly describes the invention and the manner in which it is to be performed
4. DESCRIPTION (Description shall start from next page)
5. CLAIMS (not applicable for provisional specification. Claims should start with the preamble -
"I/We claim" on separate page)
6. DATE AND SIGNATURE (to be given on the last page of specification)
7. ABSTRACT OF THE INVENTION (to be given along with complete specification on the
separate page)
Note:
*Repeat boxes in case of more than one entry
*To be signed by the applicant(s)or the authorized registered patent agent
*Name of the applicant should be given in full, family name in the beginning
*Complete address of the applicant should be given stating with postal index no. / code, state and
country
*Strike out the column which is/are not applicable

ARRANGEMENT OF MAGNETIC CLADDING FOR ELECTRICAL SWITCHING DEVICE
Field of the invention
The invention is related to electro-magnetic material structure or shape for an electrical switching apparatus. More particularly, this invention relates to magnetic cladding, which is used in switches to lock the moving contact in particular position and to restrict its movement in X-Y direction. The use of magnetic material improves the attraction force between two moving contacts which is used to overcome the repulsion force between contacts to claim higher Short Time Withstand (STW) capacity.
Background of the invention
Electrical switching apparatus, such as switch disconnector, which will provide safety isolation and short time withstand (STW) current capacity for any low voltage circuits and are suitable for diverse applications, in motor control centers, in switchboards and as main switches in various equipment and machines. These switches are ideal for withstanding higher short circuit currents for short time duration.
The electrical contact system assembly of low-voltage switches, for example generally comprises Terminal (Stationary Contact), Moving contact, Magnetic Cladding, Leaf Spring, Rotor and Contact System Housing.
In general, in contact system, the moving contact having a undercut and which is located in bridge, in order to lock the moving contact in particular direction. This moving contact has to restricts its movement in X-Y direction and allow movement in Z-direction only. But due to undercut in moving contact, there are a lot of drawbacks
1. Which will results in weakening of cross-sections at undercut portion in the moving contact, this will results in higher stress point at undercut section and it can break after few mechanical operations and limits the switch life.
2. Hot spots created at undercut portion, which will results into higher temperature at rated current and in case of short-circuit current it results into more thermal stress and damages the contacts and entire system.

So, there is need to avoid the undercut in moving contact, in order to avoid breakage of moving
contact and increases the mechanical life of contacts. This can be achieved by using current
invention.
Object of the invention:
Object of the present invention is to increase the attraction force created by magnetic cladding by minimizing gap between two magnetic claddings.
Another object of the present invention is to remove the slot provided in moving contact.
Yet another object of the present invention is to increase the short-time current carrying capacity
of contact system.
Further object of the invention is to increase the Life (Electrical and Mechanical) of contact
system and support to leaf spring to maintain constant contact pressure.
Summary of the invention:
Magnetic cladding is divided into two parts i.e. top plate (4) and side plate (6). Both top and side plate of magnetic cladding is of magnetic material. The side plate rests on the rotor (2) and moving contact (3) rest on the protrusion given on the side plate (6). Top plate (4) rests on the top surface of the moving contact (3) and there is minimum clearance between magnetic cladding top plate (4) and side plate (6) and also it covers complete magnetic cladding side plate (6). On top of magnetic cladding, leaf spring is used to maintain contact pressure under loading condition, which also creates the attraction force. As the current flows in the parallel conductors (Moving contacts) in the same direction, there will be attraction force (Lorentz force) produced due to the magnetic field generated by the conductors. Similarly magnetic cladding placed on top moving contact will also generate electromagnetic force, which is in terms creates attraction force. Description of the Drawings:
Figure. 1 shows the general view of contact system of Switch disconnector, it comprising of terminal (1), contact system rotor (2), moving contact (3), magnetic cladding top plate (4), leaf spring (5) and magnetic cladding side plate (6).
Figure.2 shows the inside view of contact system rotor and it comprising of moving contact (3), magnetic cladding top plate (4), leaf spring (5), magnetic cladding side plate (6).

Figure.3 shows the exploded view of contact system rotor.
Figure.4 shows the general view of magnetic cladding top plate (4).
Figure.5 shows the general view of magnetic cladding side plate (6).
Detailed Description:
The foregoing objects of the present invention are accomplished and the problems and shortcomings associated with the prior art, techniques and approaches are overcome by the present invention as described below in the preferred embodiments.
In this invention, magnetic cladding is divided into two parts i.e. top plate (4) and side plate (6).
Both top and side plate of magnetic cladding is of magnetic material.
Figure.2 shows the moving contact assembly in rotor. Here the moving contact (3) rest on the
protrusion given on the side plate (6) and side plate rest on the rotor (2), not like in other case
where a slot is given on the moving contact and magnetic cladding and both rest on the rotor. As
the slot is removed from the moving contact, it helps in reducing the thermal stress level on
moving contact i.e., decreases the current density and in turn increasing the mechanical life of
contact system.
Top plate (4) is designed in such a way that it rests on the top surface of the moving contact (3)
and there is minimum clearance between magnetic cladding top plate (4) and side plate (6) and
also it should cover the complete magnetic cladding side plate (6).
In order to overcome the Electro-Dynamic Stress during short circuit, we need to compensate the
electro-dynamic forces (i.e., Attraction and Repulsion Forces) in such a way that attraction force
should be greater than repulsion force.
The Repulsion force (i.e., Holmes forces) generate at constriction level at contact zone (contact
area), due to current reversal at constriction level. It totally depends on number of a-spots.
In order to compensate this repulsion forces, attraction force is generated by
a. Two Parallel Conductors (Lorentz Force)
b. Magnetic Claddings (Electro-magnetic Force)
c. Leaf Springs (Compression Force)
As the current flows in the parallel conductors (Moving contacts) in the same direction, there will be attraction force (Lorentz force) produced due to the magnetic field generated by the

conductors. Similarly magnetic cladding placed on top moving contact will also generate
electromagnetic force, which is in terms creates attraction force. On top of Magnetic cladding,
leaf spring is used to maintain contact pressure under loading condition, which in terms creates
the attraction force.
So it is necessary to restrict the movement of moving contact and cladding to utilize the contact
pressure provided by leaf spring.
Some of the advantages of present invention are:
a) With this unique arrangement of magnetic cladding, the undercut in moving contact is avoided, by this increasing the life of contacts.
b) In this invention, the magnetic cladding is divided into two separate components (i.e., Top Plate and Side Plate), which increases the electro-magnetic force in the contact system.
c) This arrangement helps in restricting the moving contact displacement in X-Y direction resulting in proper contact surface area between moving contact and terminal.
d) Increase the mechanical life of contacts,
e) Fixing arrangement,
f) Improvement in temperature rise at rated current and also
g) Improvement in short-circuit performance.

We claim,
1) An arrangement of magnetic cladding for electrical switching device comprising;
a rotor, the rotor having a cavity and plurality of slots in its centre for mounting contact
system,
a vertical side plate magnetic cladding mounted along the side walls of the said central
cavity in the rotor, the side plate having protrusions,
a moving contact mounted on the said protrusion,
a horizontal top plate magnetic cladding mounted over the said moving contact, the top
plate extending to cover top surface of the said vertical side plate magnetic cladding and
a leaf spring mounted over the horizontal top plate magnetic cladding to maintain
pressure on the said moving contact.
2) An arrangement of magnetic cladding for electrical switching device of the claim 1, wherein vertical side plate magnetic cladding and horizontal top plate magnetic cladding are made of magnetic material
3) An arrangement of magnetic cladding for electrical switching device of the claim 1, wherein as the current flows in the parallel conductors (Moving contacts) in the same direction, there will be attraction force (Lorentz force) produced due to the magnetic field generated by the conductors.
4) An arrangement of magnetic cladding for electrical switching device of the claim 1, wherein movement of the moving contact and cladding is restricted due to leaf spring pressure.