Description:FIELD OF THE INVENTION:
This invention relates to a Process for preparing thermosetting polymer with improved thermal transfer characteristics for better thermal/heat conduction/heat dissipation.
In the present invention, electrical machine in particular Axial Flux Permanent Magnet Electrical Machine (AFPM) has a rotor with a rotary shaft, a stator surrounding an outer periphery of the rotor, and a frame supporting the rotor and the stator, wherein the stator and rotor system interact with each other electromagnetically.
The stator has stack of laminations, in which the stack has slots through which electrically insulated copper winding wires are wounded. The additive-modified thermosetting polymer matrix system is applied to the electrically insulated copper winding wire for encapsulation purpose.
This insulated encapsulation system will surround and bond the electrically insulated copper winding wires within each slot as well as fill all voids within each of the slots of stator. This encapsulation system shall improve thermal conduction and help in development of compact electrical machines.
BACKGROUND OF THE INVENTION
Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
Electrical machine, such as electric motors or generators, typically include a rotor that is installed within a stator and utilized to convert electrical power into mechanical power or vice versa.
Electrical machines can be divided into two types considering their flux path: radial-flux permanent-magnet (RFPM) machines and axial-flux permanent-magnet (AFPM) machines. RFPM is more prevalent and has been in use for a long time. AFPM is an excellent alternative when high torque and efficiency are required. Although the AFPM was invented earlier, its future development was hampered by the material and technology levels available at the time. Immediately after the availability of rare Earth magnets, the era of technological advancement of AFPM was started, which is still lingering.
The basic working principle of the AFPM machine is similar to other electrical machines except for the produced flux pattern. For radial machines, the magnetic flux travels radially along the rotor radius, while in AFPM, it travels axially along the rotor axis. Figure 1 illustrates the two different directions of the magnetic field lines through the air gap of the electrical machines. The different flux directions lead to different coil arrangements inside the machines and different iron structures. While the radial flux machine has a cylindrical iron structure, the axial-flux machine has a disc-like motor shape. Therefore, AFPM machines have a good advantage of short axial length over RFPM machines, and the coreless concept can easily be implemented in this topology. Application of coreless structure helps eliminate core loss and eddy current loss delivering higher power density and efficiency in AFPM machines.
AFPM machines can be designed as double-sided, single-sided, or even as multi disk configurations. Naturally, the easiest and the cheapest construction is the single-sided (only one rotor and one stator disk) type, but due to the relatively low torque production and bearing problems caused by the high attractive force normal to the plane of the air gap which tends to bring the two parts together, this type is not very popular. However, the high attractive force between the rotor and the stator can be counter balanced by the use of a second stator/rotor mounted as the mirror image of the first. This construction is called the double-sided arrangement. Double-sided motors are the most promising and widely used types. Double- sided motors can be constructed with an internal stator or an internal permanent-magnet disk rotor. A double-sided motor with an internal permanent magnet disk rotor has two stator cores and a disk rotor with permanent magnets sandwiched between them. In this construction the stators are surrounded by a considerable amount of end windings which results in a poor utilization of the machine copper. The flux return paths are in the stators and relatively large iron losses are more pronounced in this configuration with respect to the other type. On the other hand, having stators adjacent to the axial end surfaces of the device facilitates in providing a good thermal path for cooling the windings. Stator windings of this configuration can be connected either in parallel or in series, which is an issue to be considered in the design. In parallel connection, the motor can operate even if one stator winding is broken, while series connection provides equal magnitudes of opposite axial attractive forces. If the windings are connected in series, then one stator may be rotated over a certain angle with respect to the other which results in reduced cogging torque and space harmonic components.
The stator can be iron-free or contain magnetic iron. The iron-free stator disc is manufactured by placing the stator coils in a mould to be filled with epoxy. In bigger machines with large mechanical forces, the epoxy may be supported by carbon fibre. When having iron present in the stator, it can be a slotted or non-slotted stator. Then on-slotted stator is very simple, where stator coils are glued to an iron disc as seen in Fig.1.The stator shape has an impact on the cogging torque from (5). Since the rotor magnets and copper have the same permeability as air, a machine with non-slotted stator will have no variation in magnetic reluctance when rotating, hence no cogging torque. The slotted stator iron provides a more solid structure. Using the stator slots to house the stator coils will prevent any movement. The air-gap magnetic field will go through the iron teeth instead of the coil, and because of this the conductor size may be higher due to lower eddy current losses. The disadvantage is that the introduction of slotted stator will generate variable air-gap reluctance, resulting in high cogging that will leave the machine unusable if not taken into account in the design process.
Copper is commonly used as conductor material in electrical machines due to its excellent conductive property. However, the price of copper has been increasing over the last decade, and is now considered a very costly metal. As a response to this, aluminium has been introduced into a number of application store place copper. Aluminium is a cheap, light weight metal, with about 60% conductivity of copper. The material properties of copper and aluminium is shown in table 1. Compared to copper, the aluminium oxidizes instantly in contact with oxygen. The oxidation layer is highly resistive, and is problematic when connecting aluminium coils together. The contact surface needs to be larger with aluminium coils compared to copper coils. This present a problem when having many connections and restricted space in the stator. The natural oxidation of aluminium provides a protecting and electrically isolating surface. To increase the oxidation layer, the aluminium part can be anodized, resulting in higher electrical insulation and more protective against external damages. Copper oxidizes slowly, and it is not difficult to remove any oxidation to achieve a good contact surface. However, the copper needs to be coated with an insulator. The insulation is very thick and has a low heat transfer capability compared to the oxidation layer of aluminium. If copper is used in the machine, the surface facing the cooling liquid will not be insulated, provided that the cooling mediums dielectric strength is suited to the voltage level. Without insulation on the copper, the heat transfer will be larger than from aluminium, together with higher thermal and electrical conductivity. But due to higher cost and weight, copper is more suited in high performance machines.
Cooling mediums considered in this design are water and air. Transformer oil or other such liquids can also be used, but is not considered here. The axial flux machine acts as a natural centrifugal pump when rotating, where it pushes air or water radially out from its centre. If the operation of the machine provides sufficient flow, there is no need for any external fan or pump. The centrifugal effect is enhanced by salient features in the rotor design. In Fig.1 (a) & (b) this is done by designing the rotor as a wheel with spokes together with salient magnets. The key parameter that influences the cooling capability is the HTC-Heat Transfer Coefficient. The HTC has units Watts per Kelvin per surface area, and determines how much energy the cooling medium can extract per second from the stator coil. The HTC is proportional to the temperature gradient between the cooling medium and heat source, and proportional to the surface area between them. The HTC is heavily influenced by the flow and phase of the cooling medium. For example, at low speeds, the medium will have a laminar flow with a thin film close to the stator surface. This will act as a boundary layer and not mixed with the rest of the flow. The medium within this boundary will be heated, and so on reach a higher temperature than the surrounding flow. With a lower temperature gradient between the coil and cooling medium will proportionally reduce the amount of energy removed from the coil. At high speeds the flow is turbulent, and heated medium at the heat source will quickly be removed and replaced with colder medium, keeping the entire flow heated. Hence, the temperature gradient will be higher and extract more energy.
In recent years, industrial and automobile motors and industrial and automobile inverters have been rapidly downsized and increased in output, and insulating materials are demanded to have considerably superior properties. Particularly, the amount of heat generated from conductors increased significantly in association with downsizing has been increased, making dissipation of the heat an important problem. As insulating materials used in these motors and inverters, temperature cured samples containing a thermosetting polymer are widely employed because of their high insulation performance, ease of moulding, heat resistance and the like. However, since thermosetting polymer temperature cured samples generally have a low thermal conductivity and are thus a major factor that interferes with heat dissipation, it is desired to develop a thermosetting polymer cured samples having a high thermal conductivity for better heat conduction from copper conductor to the base plate of the electrical vehicle.
The improvement of heat dissipation or better heat conduction in electric devices has become a very important issue recently, because operating currents and circuit densities in the devices show a consistent tendency to go up in various electrical systems. Furthermore, it is a fact that the low thermal conductivity of insulating resins can be a blocking factor in the improvement of heat dissipation or better heat conduction.
Improved thermal management can reduce total weight and size of the motor for a required power and torque, and allow cost saving because the amount of the copper, lamination steel, and even magnet material can be reduced. When forced air or liquid cooling is not enough to achieve the thermal management requirements, high thermally conductive encapsulation materials can be used effectively to help meet design and operation requirements. This additive modified thermosetting polymer will act as building block between low thermal conductive thermosetting polymer and high thermal conductive copper, stack of laminate steel and base plate of electrical vehicle. Further for better thermal conductance of stator stack of laminations, an insulated encapsulation system can be adopted.
Now, reference may be made to below patents:
U.S. Patent No. 4,492,889 discloses an encapsulated stator for a submerged motor having an inner cylindrical part made of carbon fibre-reinforced plastic which is adhesively bonded to metal end covers which are welded to an outer metal cylinder. The laminations and windings of the stator enclosed between the inner composite and outer metal cylinders are encapsulated by injecting a mould resin which can contain inorganic powder material into the volume enclosed by the cylinders. The composite inner cylinder provides increased wall thickness at opposite axial end portions to provide flawless joints between the inner composite cylinder and the end. According to this patent the inner cylinder may be made from any plastic material or sheet metal and any suitable material may be used for adhesively bonding the cylinders together.
U.S. Pat. No. 4,973,872, a rotor assembly has a plurality of magnets and is encapsulated by an outer moulded plastic cylindrical sleeve having runners which extend into channels in the rotor core. The plastic sleeve may be a fiberglass-filled plastic material.

U.S. Pat. No. 6,069,421 discloses an electric motor having a composite encapsulated rotor in which permanent magnets and pole pieces are encased in a canning layer of high strength resin containing high modulus fibres such as fiberglass combined with a metallic backing ring on the side away from the magnetic flux field extending between the rotor and the stator.
U.S. Pat. No. 5,122,704 discloses a composite rotor sleeve for preventing flow of liquid from the interior of a liquid-cooled rotor into a gap between the rotor and the stator. That sleeve includes an inner layer which is a continuous film of polyimide material in the form of a helically wound ribbon sealed with polyimide adhesive and a covering layer formed with a plurality of plies of wound fibrous material such as carbon fibre, each ply being impregnated in a resin matrix. Preferably eight of the plies are wound generally circumferentially to provide hoop strength and four other plies are wound at an angle to prevent generation of thermally induced stresses or relative movement between the sleeve and the rotor.
The present invention differs from the practices disclosed in the prior art. This application does not use any conventional methods for better heat dissipation, instead uses inorganic or organic metal oxide Nano-powder for improvement of thermal conduction compared to liquid or air cooling of the stator. Additive modified thermosetting polymer acts as intermediator between copper conductor and base plate of the electrical vehicle or stator slots.
Thus, the prior art fails to disclose a less expensive thermos-setting polymer system for the manufacture of high speed Axial Flux Permanent Magnet (AFPM) electrical machine with high thermal conductivity and/or thermal expansion, which are mechanically strong and which also meet the depicted high voltage insulation requirements.
OBJECTS OF THE INVENTION
Primary object of the invention is to provide Process for preparing thermosetting polymer with improved thermal transfer characteristics for better thermal/heat conduction/heat dissipation, which obviates shortcomings of the prior art(s).
Another object of the invention is to provide a Process for preparing thermosetting polymer with improved thermal transfer characteristics for better thermal/heat conduction/heat dissipation, which permits a quick and simple manufacturing, requiring better heat conduction resulting in a stator with better characteristics, permitting amongst others at a higher rotational speed.
Still another object is to propose a method according to which the encapsulation of stator slots with epoxy insulated copper winding wire by additive modified thermos-setting polymer system that solidifies, forms a monolithic body and is solid at the working temperatures of the electrical machine, such as a thermosetting plastic, more particularly an epoxy resin, or a metal alloy with a suitable melting point, wherein said liquid is injected under pressure between the inner diameter of the stator slot and the motor body and held under pressure during solidification.
Yet another object is to propose a stator of a high speed Axial Flux Permanent Magnet (AFPM) electrical machine, in which an epoxy insulated copper winding wire wounded stator slots of laminated stacks is encapsulated by additive modified thermosetting polymer for better thermal conduction and firmly acting as a single component.
These and other objects and advantages of the present invention will be apparent to those skilled in the art after a consideration of the following detailed description taken in conjunction with the accompanying drawings in which a preferred form of the present invention is illustrated.
SUMMARY OF THE INVENTION
One or more drawbacks of conventional systems and process are overcome, and additional advantages are provided through the apparatus/composition and a method as claimed in the present disclosure. Additional features and advantages are realized through the technicalities of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered to be part of the claimed disclosure.
According to this invention, there is provided Process for preparing thermosetting polymer with improved thermal transfer characteristics for better thermal/heat conduction/heat dissipation comprising steps of:
• preparing an inner peripheral surface of a stator iron core by chemical etching and/or mechanically for promoting the adhesion between the stator iron core and the electrically insulated copper winding wire;
• preparing an emulsion of epoxy material;
• preparing an emulsion of epoxy - additive/filler material by mixing and milling of additive/filler material and emulsion of epoxy material for 03-05 hours continuously;
• preparing an additive/filler modified thermosetting polymer by mixing emulsion of epoxy - additive/filler material and carboxylic acid anhydride hardeners using a high shear mixer under a vacuum with pre-determined ratio of the two components.

The emulsion of epoxy material comprising of epoxy resin preferably diglicydylether of Bisphenol-A (DGEBA), flexibilzer and accelerator prepared by mixing for 50-90 minutes
The additive/filler material is prepared by the below steps:
-Addition of functionalization agent including silane coupling agent ((3-Glycidyloxypropyl) trimethoxysilane (GPS)) with Isopropyl alcohol;
-Addition of additive/filler system with different average particle size (APS) with the prepared functionalization agent;
-Mixing and Milling the above prepared chemicals for about 2-3 hrs, ultrasonication for ⁓1hr, thereby formation of slurry of functionalized additive/filler followed by drying at 60-80 Deg. C for removal of isopropyl alcohol;
-Post curing the slurry at 160-180 Deg. C for 4-10 hrs to obtain dry functionalized additive/filler material.
The additive/filler material is prepared by mixing and maintaining a weight ratio of 0.1-1%:40-60%:0.1-5% for functionalization agent including silane coupling agent (3-Glycidyloxypropyl) trimethoxysilane (GPS), Isopropyl alcohol and additive/filler material.
The emulsion of epoxy material is prepared by mixing and maintaining a weight ratio of 90-100%:05-20%:0.1-1% for epoxy resin preferably diglicydylether of bisphenol-A (DGEBA), flexibilizer and accelerator.
The additive/filler modified thermosetting polymer is prepared by maintaining a weight ratio of 90-100%: 90-100%: 0.1-5% for epoxy: hardener: additive/filler material.

The encapsulation of thus-obtained additive/filler modified thermosetting polymer is carried out by casting in Steel/MS mould as per the dimension/shape of the components/specimens including removal of the air bubble in the composite body through de-gassing during fabrication/casting/moulding/impregnating.
The heat treatment of the encapsulated additive/filler modified thermosetting polymer for better thermal conduction/thermal dissipation on stator iron core in an air circulated oven in a temperature range of 80-90oC preferably at 80oC for a period of 6-8 hours, and producing a pre-cured additive-modified encapsulated body.
The heat treatment of the pre-cured additive-modified encapsulated body is carried out with air in the oven at a temperature range of 140o – 150oC preferably at 140oC for a period of 6 – 8 hours, which produces a fully-cured additive-modified thermosetting polymer for better thermal conduction/thermal dissipation”.
Various objects, features, aspects, and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.
It is to be understood that the aspects and embodiments of the disclosure described above may be used in any combination with each other. Several of the aspects and embodiments may be combined to form a further embodiment of the disclosure.
The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.

BRIEF DESCRIPTION OF THE ACCOMPNAYING DRAWINGS
The illustrated embodiments of the subject matter will be best understood by reference to the drawings, wherein like parts are designated by like numerals throughout. The following description is intended only by way of example, and simply illustrates certain selected embodiments of devices, systems, and processes that are consistent with the subject matter as claimed herein, wherein:-
Figure 1 (a) shows: Front view of Axial Flux Machine.
Figure 1 (b) shows: Side view of Axial Flux Machine.
The figures depict embodiments of the disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.
DETAIL DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS
While the embodiments of the disclosure are subject to various modifications and alternative forms, specific embodiment thereof have been shown by way of example in the figures and will be described below. It should be understood, however, that it is not intended to limit the disclosure to the particular forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternative falling within the scope of the disclosure.
The instant makes a disclosure regarding a Process for preparing thermosetting polymer with improved thermal transfer characteristics for better thermal/heat conduction/heat dissipation and thereby, a method for manufacturing a high speed Axial Flux Permanent Magnet (AFPM) electrical machine or any electrical machine, which has a rotor with a rotary shaft, a stator surrounding an outer periphery of the rotor, and a frame supporting the rotor and the stator, wherein the stator and rotor system interact with each other electromagnetically. The stator has stack of laminations, and the stack has slots through which electrically insulated copper winding wires are wounded. The additive-modified thermosetting polymer matrix system is applied to the electrically insulated copper winding wire for encapsulation purpose. This insulated encapsulation system surrounds and bonds the electrically insulated copper winding wires within each slot as well as fill all voids within each of the slots of stator. This encapsulation system improves thermal conduction and helps in development of compact electrical machines.
The incorporation of additive/filler into the thermosetting polymer system for better thermal conduction/heat dissipation in the encapsulation system will allow easy penetration of epoxy resin matrix material and provide the good adhesion between electrically insulated copper winding wire to the stack laminates of stator slots and base frame of the electrical vehicle, the process of functionalisation of additive/filler system before adding into the thermosetting polymer system, thereby encapsulation of additive/filler modified thermosetting polymer system for better thermal/heat conduction or heat dissipation, comprises the following steps:
Process for functionalisation of additive/filler system before addition into thermosetting polymer system;
• Addition of required percentage of functionalisation agent like silane coupling agent ((3-Glycidyloxypropyl) trimethoxysilane (GPS)) with Isopropyl alcohol;
• Addition of additive/filler system with different average particle size (APS) with already prepared functionalization agent;
• Mixing and Milling the above prepared chemicals for about 2-3 hrs, further ultrasonication for 1hr, thereby formation of slurry of functionalised additive/filler system, further drying at 60-80 Deg. C for removal of isopropyl alcohol;
• After removal of isopropyl alcohol from slurry of functionalised additive/filler system, the slurry is again post cured at 160-180 Deg. C for 4-10 hrs.;
• Dried functionalised additive/filler system is ready for addition into thermosetting polymer system is known as “additive/filler system or material”.
Process for encapsulation of additive/filler modified thermosetting polymer system for better thermal/heat conduction or heat dissipation;
• preparing an inner peripheral surface of a stator iron core by chemical etching and/or mechanically for promoting the adhesion between stator iron core and the electrically insulated copper winding wire;
• preparing an “emulsion of epoxy material” comprising commercial epoxy resin system preferably diglicydylether of Bisphenol-A (DGEBA), required percentage of flexibilzer and accelerator by mixing for 50-90 minutes;
• preparing an “emulsion of epoxy - additive/filler material” comprising “additive/filler system or material” and “emulsion of epoxy material” by mixing and milling for 03-05 hours continuously;
• preparing a “additive/filler modified thermosetting polymer system” containing “emulsion of epoxy - additive/filler material” and carboxylic acid anhydride hardeners system mixing using a high shear mixer for required time; under a vacuum with pre-determined ratio of the two components to produce a “additive/filler modified thermosetting polymer system”;
• encapsulation of thus-obtained “additive/filler modified thermosetting polymer system” by casting in Steel/MS mould as per the dimension/shape of the components/specimens including removal of the air bubble in the composite body through de-gassing during fabrication/casting/moulding/impregnating;
• heat treatment of the encapsulated with additive/filler modified thermosetting polymer for better thermal conduction/thermal dissipation on stator iron core in an air circulated oven in a temperature range of 80-90oC preferably at 80oC for a period of 6-8 hours, and produce a pre-cured additive-modified encapsulated body; and
• heat treatment of the pre-cured additive-modified encapsulated body with air in an over at a temperature range of 140o – 150oC preferably at 140oC for a period of 6 – 8 hours, which produces a fully-cured additive-modified thermosetting polymer for better thermal conduction/thermal dissipation”.
According to the invention, a validation of the process was made by testing of thus-derived “additive/filler modified thermosetting polymer system for better thermal conduction/thermal dissipation”: for measurement of withstanding or withholding better heat dissipation/thermal conduction under high speed operation of electrical vehicle.

The derived ‘encapsulated epoxy composites’ according to the invention, can be used as a superior electrical insulation material in the field of high voltage insulation system for producing numerous insulation components for indoor and outdoor use.

Thus, the present invention refers to modification of conventional Epoxy Resin system by identifying and incorporating a new dielectric material as an additive/filler, i.e., nanostructured amorphous alumina, silica, hexagonal boron nitride, cubical boron nitride filler material and thereby fabricating an epoxy composite body following pre-defined procedure and process parameters, composite body of which has enhanced/higher Thermal conductivity, which would serve as a superior electrical insulating material in high voltage electrical machine applications.
According to the present invention and in order to accomplish the above objects, there is provided a process for incorporating nanostructured amorphous alumina, silica, hexagonal boron nitride, cubical boron nitride filler material for fabricating filler-modified epoxy composites using variable loading of filler in the Epoxy Resin system so as to enhance the Thermal conductivity, which is disclosed in this invention.
In a more particular embodiment of the present invention, the synthesis of Thermal conductivity dielectric material as a filler along with its properties is defined in the Table 1.0 (below) and the same is synthesized by adopting appropriately synthesis procedure in-house. As described, the new filler dielectric material, i.e., amorphous alumina, silica, hexagonal boron nitride, cubical boron nitride has unique properties, which is amorphous in the XRD and having a tap density in the range of 0.2 – 0.3 g/cc and preferably the material with a tap density of about 0.22-0.28 g/cc were chosen in this invention.
Table 1.0: Properties of Nano Structured Additive/Filler
Sl. Nos Properties Alumina
Silica Hexagonal Boron Nitride Cubical boron Nitride
a) Chemical Formula Al2O3 SiO2 hBN cBN
b) Appearance Whitish Powder White, odour less powder Whitish Powder Whitish Powder
c) Specific Surface Area 15 - 20 m2/g 10-20 m2/g 250–350 m2g 60-65 m2/g
d) Average Crystallite Size (Range) 50 – 150 nm 1-120 µm 2-200 µm 7-12 µm
e) Tap Density 0.2 – 0.3 g/cc 2.7-2.95 g/cc 2.1-2.57 g/cc 2.1-2.77 g/cc

As per the invention, the said amorphous alumina, silica, hexagonal boron nitride, cubical boron nitride filler material having the loading in the range of 1 – 5 weight% are first to be mixed with silane (Υ-glycidoxypropyltrimethoxysilane) in the weight range of 0.5 – 2 % along with the hardener liquid (which is chemically carboxylic acid anhydride based liquid) in the conventional Epoxy Resin system using a 3D mixer or a planetary mixer after which an emulsion results.
The resultant emulsion is then to be mixed with Epoxy Resin (bisphenol A Epoxy Resin) along with flexibilizer (polyglycol based liquid) and accelerator (tertiary amine based liquid) in pre-determined proportions using a vacuum mixer (with de-gassing attachment) for a period of 30 – 60 minutes, maintaining the vacuum level (0.5 – 3 mbar; lower is better) in which an emulsion-based filler-modified Epoxy Resin system results.
The resultant emulsion-based filler-modified Epoxy Resin system is now to be casted as per the shape/size of component and then to be de-gassed and further to be heat treated in air circulated oven by maintaining the set temperature range of 80 - 90oC preferably at 80oC for a period of 6 – 8 hours, which results in pre-cured filler-modified Epoxy Resin body.
The thus-derived pre-cured filler-modified epoxy body is to be heat treated in air circulated oven at a set temperature range of 140 – 150oC preferably at 140oC for a period of 6 - 8 hours and then to be cooled down to ambient temperature by which the fully cured filler-modified epoxy composite body results.
The cured filler-modified epoxy composite bodies/articles are then removed from the moulds in which a standard mould releasing agent was applied prior to casting the filler-modified epoxy composite body.
The filler-modified epoxy composites are then tested for thermal conductivity performance using standard dimensions of the test samples as per IEC norms.
The Table 2.0 represents thermal conductivity test profile of the filler-modified epoxy composites as compared to blank conventional epoxy system, both of which have been casted under identical conditions.
Table 2.0, Thermal Conductivity Test Results on encapsulated electrical machine
S. No Item Description Thermal Conductivity (w/m. K) % Increase
1 Non-encapsulated electrical machine 0.20 0.00
2 Encapsulated electrical machine *
1. Alumina 0.32

60.00
2. Silica 0.22 10.00
3. Hexagonal Boron Nitride 0.94 370.00
4. Cubical Boron Nitride 0.45 125.00

*Filler/additive are added to base epoxy resin hardener system and filler/additive are added in (0.5-5.0) %wt.
The invention would be more understood in terms of taking various examples, which are explained in the following:
WORKING EXAMPLES
EXAMPLE 1:
As per this example, nano-structured amorphous alumina, silica, hexagonal boron nitride, cubical boron nitride filler/additive dielectric material out of these nano-structured amorphous alumina which is used as a filler was synthesized in-house by adopting appropriately a synthesis process using LPG-fired Spray Pyrolysis System (LPG=liquid petroleum gas).
As described this filler material has its typical properties which is amorphous in the XRD and has a tap density in the range of 0.2 – 0.3 g/cc and the material with a tap density of 0.249g/cc was used in this example. The filler material was oven dried in air at a set temperature of 300oC for a period of 2 hours before using it; this procedure is to let out the filler material from the entrapped moisture.
90-100 parts by weight of liquid hardener (carboxylic acid anhydride based liquid) is first mixed with liquid silane (Gamma-glycidoxypropyltrimethoxysilane) (1-5% wt). To this solution, nanostructured alumina filler/additive material 0.05-5.0%wt is mixed using a high speed mechanical stirrer for a period of 30 minutes and then ultrasonicated for a period of 15 minutes so that the filler powders are dispersed into the solution and an emulsion is resulted, which is termed as “Emulsion A”.

In another container (glass/plastic or stainless steel), Epoxy Resin (bisphenol A) (90-100%wt), flexibiliser (polyglycol based liquid) (5-10%wt) and accelerator (tertiary amine based liquid) (1-5%wt) were taken and mixed using a mechanical stirrer for a period of 20 minutes to get a uniformly mixed liquid resulted, which is termed as “Liquid B”.
“Liquid B” is then mixed with the “Emulsion A” for a period of 45 minutes using a high shear mechanical mixer. After this mixing, the whole mix is transferred to a vacuum casting system wherein it is degassed.
Stainless steel moulds with pre -determined dimensions are first smeared with standard mould releasing agent and the degassed mix is then vacuum casted to these moulds by maintaining a cavity.
These liquid filled moulds are then transferred to an oven and heat treated in air at 80oC for a period of 6 hours which resulted in the pre-cured “nanostructured alumina, calcium carbonate, aluminium phosphate, zinc borate filler modified epoxy composites”.
The said pre-cured composites is then heat treated at 140oC for a period of another 6 hours and then cooled down at ambient temperature by which the fully cured “nanostructured alumina filler/additive modified epoxy composites” with pre- determined dimensions resulted which were released from the moulds and tested for thermal conductivity characteristics following IEC norms.
For comparison, conventional Epoxy Resin body with pre- determined dimensions was also casted without using any filler in the epoxy system and subjected to thermal conductivity characteristics tests following the same IEC norms.
The derived composite showed a % increase in thermal conductivity after the Test which is about 60.0% compared to the blank conventional epoxy body.
Example 2:
In this example, the procedure and all the experimental conditions were followed exactly the same that is described in the example 1, except that the filler material, i.e., the silica filler/additive material was used instead of nanostructured alumina filler in the example 1.
The derived composite showed a % increase in thermal conductivity after the Test which is about 10.0% compared to the blank conventional epoxy body.
Example 3:
In this example, the procedure and all the experimental conditions were followed exactly that is described in the example 1, except that the filler material, i.e., the hexagonal boron nitride filler/additive material was used instead of nanostructured alumina filler in the example 1.
The derived composite showed a % increase in thermal conductivity after the Test which is about 370.0% compared to the blank conventional epoxy body.
Example 4:
In this example, the procedure and all the experimental conditions were followed exactly that is described in the example 1, except that the filler material, i.e., the cubical boron nitride filler/additive material was used instead of nanostructured alumina filler in the example 1.
The derived composite showed a % increase in thermal conductivity after the Test which is about 125.0% compared to the blank conventional epoxy body.
From above examples, the best suitable filler is chosen for encapsulation of axial flux machine and the thermal properties are evaluated.
ADVANTAGES OF INVENTION
- Quick and simple manufacturing, requiring better heat conduction resulting in a stator with better characteristics, permitting amongst others at a higher rotational speed;
-A stator of a high speed Axial Flux Permanent Magnet (AFPM) electrical machine, in which an epoxy insulated copper winding wire wounded stator slots of laminated stacks is encapsulated by additive modified thermosetting polymer for better thermal conduction and firmly acting as a single component;
-Serves the purpose efficiently.

Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references below to the "invention" may in some cases refer to certain specific embodiments only. In other cases, it will be recognized that references to the "invention" will refer to subject matter recited in one or more, but not necessarily all, of the claims.
Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all groups used in the appended claims.
It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particulars claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogues to “at least one of A, B and C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to “at least one of A, B, or C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase “A or B” will be understood to include the possibilities of “A” or “B” or “A and B”.

The above description does not provide specific details of manufacture or design of the various components. Those of skill in the art are familiar with such details, and unless departures from those techniques are set out, techniques, known, related art or later developed designs and materials should be employed. Those in the art are capable of choosing suitable manufacturing and design details.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. It will be appreciated that several of the above-disclosed and other features and functions, or alternatives thereof, may be combined into other systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may subsequently be made by those skilled in the art without departing from the scope of the present disclosure as encompassed by the following claims.

The claims, as originally presented and as they may be amended, encompass variations, alternatives, modifications, improvements, equivalents, and substantial equivalents of the embodiments and teachings disclosed herein, including those that are presently unforeseen or unappreciated, and that, for example, may arise from applicants/patentees and others.

While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.
, Claims:We Claim:
1. Process for preparing thermosetting polymer with improved thermal transfer characteristics for better thermal/heat conduction/heat dissipation comprising steps of:
• preparing an inner peripheral surface of a stator iron core by chemical etching and/or mechanically for promoting the adhesion between the stator iron core and the electrically insulated copper winding wire;
• preparing an emulsion of epoxy material;
• preparing an emulsion of epoxy - additive/filler material by mixing and milling of additive/filler material and emulsion of epoxy material for 03-05 hours continuously;
• preparing an additive/filler modified thermosetting polymer by mixing emulsion of epoxy - additive/filler material and carboxylic acid anhydride hardeners under a vacuum with pre-determined ratio of the two components.

2. The process as claimed in claim 1, wherein the emulsion of epoxy material comprising of epoxy resin preferably diglicydylether of Bisphenol-A (DGEBA), flexibilzer and accelerator prepared by mixing for 50-90 minutes
3. The process as claimed in claim 1 or 2, wherein the additive/filler material is prepared by the below steps:
-Addition of functionalization agent including silane coupling agent ((3-Glycidyloxypropyl) trimethoxysilane (GPS)) with Isopropyl alcohol;
-Addition of additive/filler system with different average particle size (APS) with the prepared functionalization agent;
-Mixing and Milling the above prepared chemicals for about 2-3 hrs, ultrasonication for ⁓1hr, thereby formation of slurry of functionalized additive/filler followed by drying at 60-80 Deg. C for removal of isopropyl alcohol;
-Post curing the slurry at 160-180 Deg. C for 4-10 hrs to obtain dry functionalized additive/filler material.
4.The process as claimed in claims 1-3, wherein the additive/filler material is prepared by mixing and maintaining a weight ratio of 0.1-1%:40-60%:0.1-5% for functionalization agent including silane coupling agent (3-Glycidyloxypropyl) trimethoxysilane (GPS), Isopropyl alcohol and additive/filler material.
5.The process as claimed in claims 1-4, wherein the emulsion of epoxy material is prepared by mixing and maintaining a weight ratio of 90-100%:05-20%:0.1-1% for epoxy resin preferably diglicydylether of bisphenol-A (DGEBA), flexibilizer and accelerator.
6.The formulation as claimed in claims 1-5, wherein the additive/filler modified thermosetting polymer is prepared by maintaining a weight ratio of 90-100%: 90-100%: 0.1-5% for epoxy: hardener: additive/filler material.
7.The process as claimed in claims 1-6, wherein the encapsulation of thus-obtained additive/filler modified thermosetting polymer is carried out by casting in Steel/MS mould as per the dimension/shape of the components/specimens including removal of the air bubble in the composite body through de-gassing during fabrication/casting/moulding/impregnating.
8.The process as claimed in claims 1-7, comprising of heat treatment of the encapsulated additive/filler modified thermosetting polymer for better thermal conduction/thermal dissipation on stator iron core in an air circulated oven in a temperature range of 80-90oC preferably at 80oC for a period of 6-8 hours, and producing a pre-cured additive-modified encapsulated body.
9.The process as claimed in claims 1-8, wherein heat treatment of the pre-cured additive-modified encapsulated body is carried out with air in the oven at a temperature range of 140o – 150oC preferably at 140oC for a period of 6 – 8 hours, which produces a fully-cured additive-modified thermosetting polymer for better thermal conduction/thermal dissipation”.
10. The process as claimed in claims 1-9 comprising of further steps such as herein described.
Dated this 29th day of March, 2024