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:
COMPOSITE MATERIAL FOR CONTACT SYSTEM IN SWITCHING DEVICES
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 embodiments herein generally relate to contact materials and particularly to a composite contact material used in switching devices. The embodiments herein more particularly relate to composite contact materials having capricious magnetic and thermal properties.
B) BACKGROUND OF THE INVENTION
[0002] Various contact materials with properties appropriate for use in electrical contacts and current carrying parts of switching devices are often obtained by combining two or more substances. However such contact materials have the disadvantage of low rigidity. The contacts of an electrical switching device must easily be opened to avoid any intermediate contact repulsion position. The repulsion of the contacts takes place due to the effect of the electrodynamic forces, when the current exceeds a preset repulsion threshold. This threshold depends on the configuration of the contact material.
[0003] Most of the contact materials such as copper, silver and the like used in the switching devices is diamagnetic in nature. These diamagnetic materials exhibit negative magnetism when an external magnetic field applied to it. Another class of material such as iron (Fe), silicon steel (CRNGO/CRGO), EN1 grade steel, mild steel, which are ferromagnetic in nature, allows the external magnetic field applied to pass through it. The contact made out of these materials, upon heating below Curie temperature, except showing linear and volumetric expansion does not cause any change in the basic shape and geometrical form. Also above the Curie temperature, these material changes their electrical, magnetic, thermal and mechanical characteristics. By means of suitable annealing and tempering process, the desired characteristics of the materials can be derived.
[0004] However, none of the existing materials has both the extreme magnetic characteristics such as ferromagnetism and diamagnetism, in the same material. Also


a magnetic material while at the same time does not exhibit thermal properties. The conventional contact material also by no means can change their basic shape and form upon heating above ambient temperature.
[0005] Hence there is a need to develop a composite contact material having both the extreme magnetic characteristics and uneven magnetic and thermal behavior.
C) OBJECTS OF THE INVENTION
[0006] The primary object of the present invention is to provide a composite contact material which exhibits both diamagnetism and ferromagnetism at different level of external magnetic field and cross-section of the contact.
[0007] Another object of the present invention is to provide a composite contact material which effects, the repulsive force between opposite current carrying parts
[0008] Yet another object of the present invention is to provide a composite contact material which changes its shape and geometrical form upon heating and regains original shape and form on cooling.
[0009] 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 OJ THE INVENTION
[0010] The above mentioned shortcomings, disadvantages and problems are addressed herein and which will be understood by reading and studying the following specification.

[0011] The various embodiments of the present invention provide a composite contact material for a contact system which exhibits both the characteristic of diamagnetism and ferromagnetism. A composite contact material herein comprising a first layer of an alloy material, a second layer of a diamagnetic material, a third layer of a ferromagnetic material and a fourth layer of the alloy material.
[0012] According to one embodiment, the first layer of alloy material and the fourth layer of alloy material are identical. The first layer of alloy material and the fourth layer of alloy material is selected from a group comprising of nickel (Ni), titanium (Ti), copper (C), hydrogen (H), oxygen (O), iron (Fe). The diamagnetic material is an electrolytic tough pitch (ETP) full hard copper. The ferromagnetic material includes mild steel or any other metal. The diamagnetic material layer and the ferromagnetic material layer herein have a preset profile.
[0013] The alloy material, the diamagnetic material and the ferromagnetic material is obtained after performing the slitting and blanking operations on each of the material to form cavity and rib respectively. The alloy materials, the diamagnetic material, and the ferromagnetic material are then subjected to a mechanical bonding process to obtain a composite contact material.
[0014] The alloy material to be laminated on the diamagnetic material layer includes rectangular ribs arranged in matrix. The diamagnetic material includes cavities corresponding to the alloy material in matrix. The top section of the diamagnetic material includes two cavities separated by one wedge in the matrix. The diamagnetic material layer at its bottom section includes rectangular ribs in the matrix. The bottom section of the diamagnetic material is laminated on the matrix provided on the top section of the ferromagnetic material. The ferromagnetic material is the third layer of the composite contact material. Both the upper and bottom section of the ferromagnetic material includes two cavities separated by one vvedge in the matrix. Since the laminated diamagnetic material

has lower flow stress as compared to the matrix of ferromagnetic material, the rib invading into cavity of matrix is divided by the wedge and then rib flows separately into the die cavities of ferromagnetic material. The bottom section of the ferromagnetic material layer is laminated on the matrix provided on the fourth layer i.e. alloy material.
[0015] The bonding process is carried out at room temperature to laminate each individual contact material on the matrix. The cavity on the top section of the diamagnetic material receives the first layer of the alloy material thereby forming a mechanical bonding with respect to each other. The first layer of alloy material is also provided with rectangular ribs, which adjoins with the cavity provided on the top section of the diamagnetic material. The rib part of the laminating metal and cavities in the matrix is formed by machining, forging, shape rolling or the like. The composite material thus obtained is annealed to a temperature of 71 OK to obtain the desired magnetic and thermal characteristics. Then the composite strip is subjected to a rolling process where it attains the intended shape and joints throughout its length. Finally after completion of the etching process, the composite material is carved into the desired shape and dimension, followed by flattening and deburring.
[0016] The composite contact material possesses uneven magnetic and thermal behavior. The contact material, when exposed to an external magnetic field, diverts the flux lines towards the ferromagnetic layer of the contact material. The field lines are opposed by the diamagnetic material layer of the contact material. Thus it exhibits both diamagnetic and ferromagnetic characteristics at different levels of external magnetic field and at the cross-section of the contact material.
E) BRIEF DESCRIPTION OF THE DRAWINGS

[0017] 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:
[0018] FIG. 1 shows a plan view of a composite contact material, according to one embodiment of the present invention.
[0019] FIG. 2 shows the structure of the composite contact material, according to one embodiment of the present invention.
[0020] FIG. 3 shows the arrangement of different layers of the composite contact material of FIG. 1.
[0021] FIG. 4 is an exemplary illustration of the capricious magnetic functionality of the composite material, according to one embodiment of the present invention.
[0022] FIG. 5 shows another exemplary illustration of the capricious magnetic functionality of the composite material, according to one embodiment of the present invention.
[0023] FIG.6 shows the effect of repulsive force between opposite current carrying parts due to the composite material according to one embodiment of the present invention.
[0024] FIG.7 shows the current distribution in the various layer of the composite material, according to one embodiment of the present invention.
[0025] FIG.8 shows the heat flux distribution in the composite material, according to one embodiment of the present invention.
[0026] FIG.9 shows the temperature distribution in the composite material, according to one embodiment of the present invention.

[0027] FIG. 10 shows the deflection developed in the composite moving contact formed with a composite material, according to one embodiment of the present invention.
[0028] FIG. 11 shows the force developed in the composite moving contact, having a composite material according to one embodiment of the present invention, due to uneven expansion and contraction of material.
[0029] FIG. 12 shows the phase transition of the composite material, according to one embodiment of the present invention, due to variation in temperature.
[0030] FIG. 13, FIG.14 and FIG.15 shows the comparison of electrical resistivity, modulus of elasticity and thermal conductivity of the composite material with respect to other metals and alloys, according to one embodiment of the present invention.
[0031] 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
[0032] In the following detailed description, a 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.


[0033] The various embodiments of the present invention provide a composite contact material which exhibits a capricious magnetic and thermal behavior. The composite contact material comprises of a first layer of an alloy material, a diamagnetic material, a ferromagnetic material, and a fourth layer of the alloy material. According to one embodiment, the diamagnetic material and the ferromagnetic material is interposed between the first layer of the alloy material and the fourth layer of the alloy material to obtain the composite contact material. The composite contact material when used as a moving contact for switching devices exhibits higher delayed repulsion force during overload conditions. The composite material is malleable and ductile which can be slit into strips, wires, rods or any other preferred form.
[0034] According to one embodiment of the present invention, the composite contact material possesses uneven magnetic and thermal behavior. The composite contact material, when exposed to an external magnetic field, diverts the flux lines towards the ferromagnetic layer of the contact material. The field lines are opposed by the diamagnetic material layer of the contact material. This exhibits dual behavior of extreme magnetism i.e. diamagnetism and ferromagnetism at different level of external magnetic field and at the cross-section of the contact material.
[0035] The composite contact material changes its shape and geometrical form upon heating and regains its original shape and form on cooling. The change of shape of the composite contact material depends on its thermal hysteresis loop. As the temperature is increased, the composite contact material changes its shape above a temperature corresponding to austenitic start temperature (As) and will continue up to a temperature corresponding to the austenitic final temperature (Af). When the material is cooled, it retains its deformed shape up to a temperature corresponding to a martini stic start temperature (Ms) and upon further

cooling, regains its original shape at a temperature corresponding to a martinistic final temperature (Mf).
[0036] FIG. 1 illustrates a plan view of a composite contact material, according to one embodiment of the present invention. The composite contact material 10 includes four layers. The first layer is an alloy material 1 which has a composition comprising of nickel (Ni), titanium (Ti), carbon (C), hydrogen (H), oxygen (O), iron (Fe), trace elements and ferromagnetic material. The second layer is a diamagnetic material 2 which includes an electrolytic tough pitch (ETP) full hard copper. The third layer is a ferromagnetic material 3 which includes mild steel or any suitable metals. The fourth layer is an alloy material 4 having a composition of Ni, Ti, C, H, O, Fe, trace elements and ferromagnetic material. The diamagnetic material 2 and the ferromagnetic material 3 are interposed between the two layers of same alloy material to obtain the composite contact material 10.
[0037] FIG. 2 shows the structure of the composite contact material 10, according to one embodiment of the present invention. Each layer of the composite contact material 10 is obtained after a slitting operation and a blanking operation on the base material to form the cavities and the ribs respectively. As shown in FIG. 2, the mechanical bonding is done between the first layer of an alloy material 1, diamagnetic material 2, ferromagnetic material 3 and the fourth layer of an alloy material 4. According to one embodiment, the first layer in the composite contact material 10 is an alloy material 1. The alloy material 1 to be laminated on the diamagnetic material layer 2 includes rectangular rib 11 arranged in a matrix. The diamagnetic material 2 includes cavities corresponding to the alloy material 1 in the matrix. The diamagnetic material 2 is a second layer in the composite contact material 10 which includes an electrolytic tough pitch (ETP) full hard copper. The top section of the diamagnetic material 2 includes at least two cavities separated by one wedge in the matrix. The diamagnetic material layer 2 at its bottom section includes rectangular ribs 24 in matrix. The bottom section of the diamagnetic material 2 is laminated on the matrix provided on the bottom

section of the ferromagnetic material 3. The ferromagnetic material 3 is the third layer in the composite contact material 10. Both the top section and the bottom section of the ferromagnetic material 3 include at least two cavities separated by one wedge in the matrix. Since the laminated diamagnetic material 2 has a lower flow stress as compared to the matrix of ferromagnetic material 3, the rib 24 invading into cavity 32 and 33 of matrix is divided by the wedge 33 and then rib 24 flows separately into the cavities 31 and 32 of ferromagnetic material. The bottom section of the ferromagnetic material 3 layer is laminated on the matrix provided on the fourth layer i.e. alloy material 4.
[0038] The upper section of the diamagnetic material 2 with cavities 21 and 22 allows the first layer of the alloy material 1 to create a mechanical bonding with respect to each other. The first Jayer of aiioy material 1 is also provided with rectangular ribs 11, which enters into the cavities 21 and 22 provided in the bottom section of the diamagnetic material 2. The rib part of the laminating metal and cavities in the matrix are formed by machining, forging or by means of shape rolling.
[0039] FIG. 3 shows the arrangement of different layers of the composite contact material 10 of FIG. 1. The diamagnetic material 2, the ferromagnetic material 3 and the alloy material 1, 4 is provided with preset profiles to provide a mechanical bonding between the layers so as to obtain the composite contact material. The alloy material 1 to be laminated on the diamagnetic material layer matrix has rib 11 corresponding to that of diamagnetic matrix cavity 21 and 22. The diamagnetic material 2 includes an electrolytic tough pitch (ETP) full hard copper. The bottom section of the diamagnetic material 2 includes two cavities separated by one wedge in matrix. The diamagnetic material 2 includes rectangular ribs 24 at the bottom section, which is laminated on the matrix provided in the bottom section of the ferromagnetic material 3. The laminated copper material has lower flow stress as compared to the matrix of ferromagnetic material 3. The rectangular rib 24 invading into cavity 31 and 32 of matrix is


divided by the wedge and then rib 24 flows separately into the cavities 31 and 32 of ferromagnetic material 3. The bottom section of the ferromagnetic material layer 3 includes cavities, which is laminated on the matrix provided on the fourth layer i.e. alloy material 4.
[0040] The composite material 10 thus obtained is annealed at a temperature for instant at 710°K to obtain the desired magnetic and thermal characteristics. Thereafter, the composite contact material 10 is subjected to rolling process where it attains the intended shape and joints throughout its length. Finally after completion of the etching process, it is slit to the desired shape and dimension, followed by a flattening and a deburring process.
[0041] FIG. 4 shows an exemplary illustration of the capricious magnetic functionality of the composite material, according to one embodiment of the present invention. With respect to FIG. 4, a sheet metal of a copper 41 and a composite contact material 10 is modeled at a distance of approximately 6 mm apart in air. A 2D analysis is done with 10 KA current flowing through the current carrying parts in opposite direction. The resultant flux produced by copper 41 and composite contact material 10 is shown in FIG. 4 to understand the capricious magnetic behavior of the composite material.
[0042] FIG. 5 shows another exemplary illustration of the capricious magnetic functionality of the composite material, according to one embodiment of the present invention. The similar flux lines are plotted for two copper contacts 41 separated by a distance of 6mm in air (FIG. 5). As shown in FIG. 5, the flux lines due to individual upper contact and lower contact are opposing with respect to each other and are parallel to each other at the intersection axis. Whereas as in FIG. 4, the resultant flux lines are trying to enter into the ferromagnetic region of the composite contact material 10. The effect of resultant flux lines tending towards the ferromagnetic region, leads to reduction in the repulsion force generated between the opposite current carrying contacts. This shows the

capricious magnetic behavior of the composite material, which changes the state of the material from diamagnetic or paramagnetic to ferromagnetic.
[0043] The capricious behavior is more prominently seen as the magnetic field developed is further increased at high fault current (i.e. more than 10KA). However at lower fault current (i.e. less than SKA), the ferromagnetic effect may not be that much prominent as the field lines of the lower contact will be almost parallel to the flux lines of the upper contact which is similar to the condition of flux lines as shown in FIG. 5. Hence, it is clear from the analysis that the composite material is at diamagnetic state below fault level of 5 KA or for a feeble external magnetic field, whereas, it is at ferromagnetic state above a fault level of 10KA. Between SKA to 10KA, the composite material is partially at paramagnetic state. At a fault level of 10KA, the difference in reduction of repulsive force developed due to ferromagnetic effect of the composite material, found to be 2.2 Kg.
[0044] The capricious magnetic behavior of the composite material is identified by means of performing a 3D analysis to know the repulsive force developed at various fault current ranging from 500A to 50KA. The upper composite contact (32 x 2 x 10.4 mm) consists of first and fifth layer as alloy material, second and fourth layer as copper and third layer as Mild steel. The lower contact (34 x 6.4 x 2 mm) is of copper with dimension. The upper and lower contacts are placed at a distance of 6mm in air between nearest copper to copper contact. The result of the analysis is compared with the repulsive force developed due to copper contacts only. The result is that the ferromagnetic effect is more prominently seen above SKA of fault current.
[0045] A similar 3D analysis is conducted to illustrate the capricious thermal behavior of the invention with the following composition of elements in different layer of the composite contact system. The upper composite contact consists of first and fifth layer as alloy material, second and fourth layer as copper and third layer as mild steel. The lower contact is of a copper layer. The upper contacts and


lower contacts are placed at a distance of 6mm in air between nearest copper to copper contact. An electro-thermal structural simulation is then provided to analyze the capricious thermal behavior of the composite material at various fault current ranging from 50A to 50KA. Upon application of voltage to the terminals, a current flow is modeled in the composite contact. Due to the difference in the electrical resistivity of the individual material, the joule heat loss developed will vary from one type of material to another in the composite contact material.
[0046] FIG.6 shows an effect of repulsive force between the opposite current carrying parts in the composite material. The analysis is done to compare the repulsive force developed due to the copper contacts and the composite contact material. The graph shows the reduction in the repulsion force due to ferromagnetic effect of the composite material at various fault currents.
[0047] FIG. 7 shows a current distribution in the various layers of the composite material. The upper and lower portion of the composite material shows the current distribution in the NITI alloy layer. The distribution of current in this layer is less, owing to lower electrical conductivity of the NiTi alloy layer. The electrical conductivity is 100 times lesser as compared to the copper material. FIG. 7 represents a current density at a fault current of about 1000A. Due to the difference in the current distribution and the electrical conductivity of the composite material, the heat flux and the temperature distribution along the length of the composite material is different.
[0048] Similarly FIG. 8 shows the heat flux distribution in the composite material at a fault current of about 1000A and FIG.9 shows a temperature distribution in the composite material at a fault current of about of about 1000A. This shows a variation in differential temperature in the composite material.
[0049] The parameters, especially Young's modulus of elasticity, coefficient of linear expansion and thermal conductivity of the individual material, will vary with the temperature. This will cause a thermal deflection of the overall composite

moving contact due to an upward force developed in the composite material. Due to the stress developed at the NiTi alloy layer, the differential expansion and contraction between the individual layer of copper/mild steel and NiTi alloy, leads to a deflection in the composite contact in an upward direction. The NiTi alloy layer contracts when its temperature increases. This is due to its negative coefficient of linear thermal expansion. Due to the difference in the electrical conductivity of the composite material, the current distribution in the individual layer is different.
[0050] FIG. 10 and FIG. 11 shows the deflection and force developed in the composite material at a fault current of 1000A, This shows the capricious thermal behaviour of the composite material, which upon heating causes change in its crystai structure. The crystai structure, which normaJiy remain at a distorted state, upon heating causes alignment of the crystal lattice and hence the basic shape and geometry of the composite material. The upward deflection of the composite material is the resultant of the above phenomenon. FIG. 12 shows the phase transition of the NiTi alloy material.
[0051] FIG. 13, FIG. 14 and FIG. 15 shows the comparison of electrical resistivity, modulus of elasticity and thermal conductivity of composite material with that of other metals and alloys such as copper, silver, aluminum, gold, platinum, invar, brass, bronze etc, at standard temperature and pressure. As shown in FIG. 13, the electrical resistivity of the composite alloy is near to that of aluminum and gold. However is very much low when compared to other ferromagnetic metals such as iron, mild steel, stainless steel etc. Even the transition metals such as antimony, bismuth, platinum, titanium, manganin and alloys such as brass, bronze German silver have higher resistivity as compared to the composite material.
[0052] As shown in FIG. 14, the composite, alloy offers a moderate modulus of elasticity similar to that of copper, zinc and brass but is higher when compared


to silver, aluminum, gold, antimony, bismuth, lead, tin etc. There are few transition materials such as mild steel, Nickel and iron and its alloy, which offers twice the modulus of elasticity. Thermal conductivity of the alloy is moderate and very much similar to that of most transition metals such as tin, cobalt, nickel, platinum, mild steel, iron pure etc. However there are certain metals such as copper, silver, aluminum and gold, which have thermal conductivity almost 2 to 4 times than that of the composite alloy.
[0053] The data revealing the properties, behaviour and characteristics of the composite material as explained above is given for a typical dimension and geometrical shape and configuration. By means of suitable design of the different layer of materials in terms of their geometrical shape and dimension, further improvement in the magnetic and thermal behavior can be achieved. Also the electrical, thermal and mechanical properties can be improved and altered.
G) ADVANTAGES OF THE INVENTION
[0054] The various embodiments of the present invention provide a composite contact material with capricious magnetic and thermal behavior. The contact material exhibits extreme magnetic characteristics such as ferromagnetism and diamagnetism. The contact material is used as a diamagnetic material or as a ferromagnetic material depending upon the critical condition. The usage of contact material in contact system for switching devices provides for developing higher repulsion force, thereby improving the performance of the switching device.
[0055] The composite contact material has higher tensile strength, higher melting point as compared to individual ferromagnetic material. The contact material exhibits magnetic characteristics similar to silicon steel material below a critical temperature (Tc) due to the presence of silicon and iron. , Above a critical temperature (Tc), the contact material changes its shape and geometric form and upon cooling regains its original shape and geometry under a biased force applied

to it. The contact material regains its shape and geometry for a fixed band of temperature (i.e. from As to Af and Ms to Mf).
[0056] 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.
[0057] 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:
A composite contact material for a contact system, comprising; a first layer of an alloy material; a second layer of a diamagnetic material; a third layer of a ferromagnetic material; and a fourth layer of the alloy material.
The composite contact material according to claim 1, wherein the first layer of alloy material and the fourth layer of alloy material are same.
The composite contact material according to claim 1, wherein the first layer of alloy material and the fourth layer of alloy material is selected from a group comprising nickel (Ni), titanium (Ti), copper (C), hydrogen (H), oxygen (O) and iron (Fe).
The composite contact material according to claim 1, wherein the diamagnetic material is an electrolytic tough pitch (ETP) full hard copper.
The composite contact material according to claim 1, wherein the ferromagnetic material is mild steel.
The composite contact material according to claim 1, wherein the first layer of alloy material and the second layer of ferromagnetic material includes a plurality of ribs.
The composite contact material according to claim 1, wherein the diamagnetic material includes a preset profile.

8. The composite contact material according to claim 7, wherein the preset profile includes at least one of a plurality of cavities, a plurality of wedges and a plurality of ribs arranged in a matrix.
9. The composite contact material according to claim 1, wherein the ferromagnetic material has a preset profile.

10. The composite contact material according to claim 9, wherein the preset profile includes a plurality of cavities and a plurality of wedges in a matrix.
11. The composite material according to claim 1, wherein at least one wedge divide the rib entering into the cavity to at least two sections.
12. The composite material according to claim 11, wherein the at least one section of rib flow separately into at least one cavity to provide a mechanical bonding.