Patent Description:
This application claims priority to European Patent Application <CIT>.

Such an electro-mechanical device is known to a person skilled in the art. Such a commonly known electro-mechanical device is, for example, an electric generator.

Typically, an operational rating of an electric generator, for example, a turbo-generator is largely dependent on the current carrying capacity of its windings, that is, stator windings and rotor windings. Heating of the rotor windings limits the turbo-generator operations at overexcited conditions, particularly when there is a requirement of the reactive power by the connected power grid. Thus, the operational rating of generators is largely dependent on the rotor windings. Conventionally, cooling arrangement such as water-cooling are employed for turbo-generators, especially, large turbo-generators for efficient cooling of the stator windings. However, the conventional cooling arrangements are not efficient when employed for rotating parts such as the rotor windings. The rotor windings are typically made of Copper due to its commercial viability, reasonable costs, as well as its high electrical & thermal conduction properties. Copper is typically used for the rotor windings in all large turbo-generators. However, despite of having high electrical & thermal conduction properties, copper coils also have limitations on current carrying capability, which is largely dependent on cooling of the coils, for example, heat removal from the surface of the coils.

<FIG> illustrates a sectional view of a rotor slot <NUM> having direct-cooled rotor windings, according to state of the art. As shown in <FIG>, the rotor slot <NUM> comprises conductors <NUM>, for example, copper coils housed within a rotor slot cell <NUM>, and having ventilation channels <NUM> passing therewithin. Conventionally, electric generators, for example, large turbo-generators are designed to have direct-cooled rotor windings, in which several ventilation channels <NUM> are made in and around rotor coil cross-section, that is, conductors <NUM>, in order to allow cooling gas to flow through these ventilation channels <NUM>. The conductors <NUM> are separated from one another via inter-turn insulation layers <NUM>. The ventilation channels <NUM> are positioned on each of the conductors <NUM>. Typically, the rotor conductors <NUM> are made of Copper and conventional means of increasing the current carrying capacity of these conductors <NUM> is by increasing the cross-section or by increasing the cooling gas flow. However, due to constraints associated with physical dimensions of the generator, the current carrying capacity of these conductors <NUM> cannot be increased beyond a certain limit, which in turn decides the power rating of the generator.

Electro-mechanical devices such as electric generators of the aforementioned kind are known to employ composites such as Graphene for achieving effective power to weight ratio as these composites have better conductivity and lower losses compared to conventional materials such as Copper. Graphene is a newly discovered material having <NUM>-dimensional properties and is a crystalline allotrope of carbon. Carbon atoms of Graphene are densely packed in a regular hexagon making Graphene a light yet strong compound, having high conduction of electricity and of heat at room temperature. However, conventional methods known to employ such composites, typically, are for conductors carrying alternating current that tends to flow through the conductor's outer surfaces due to skin effect, as opposed to a direct current that tends to flow throughout the conductor's cross-section.

From document <CIT> an armature winding of electrical rotating apparatus, an electrical rotating apparatus using the same, and a method of manufacturing the same is known. From document <CIT> an electroplating apparatus is known. From document <CIT> an electric conductor for an electric machine with enhanced power to weight ratio and an electric component for the electric machine are known.

Therefore, it is an object of the present invention to provide a coated article of an electro-mechanical device of the aforementioned kind according to claim <NUM>. The coated article has a plurality of conductors carrying a direct current therewithin, and at least one heat convection enabling component disposed in operable connection within one or more of the conductors, such that the coated article increases current carrying capacity of the electro-mechanical device by employing enhanced heat convection, without compromising physical compactness and costs associated with the electro-mechanical device.

The coated article of an electro-mechanical device disclosed in the present invention achieves the aforementioned object, in that a coating is applied at least partially on the conductors and the heat convection enabling component.

In accordance with the present invention, a coated article for an electro-mechanical device, having a plurality of current carrying conductors in operable connection with at least one heat convection enabling component coated at least partially with a coating is provided. The conductors carry a direct current therewithin. As used herein, "coated article" is a rotatable component. In a preferred embodiment according to the present invention, the rotatable component is a rotor of the electro-mechanical device. According to another embodiment not part of the invention, the coated article is a rotor winding ventilation duct. According to an embodiment not part of the invention, the coated article is a rotor sub-slot. The coated articles include any suitable component such as, but not limited to, the rotor, a rotor shaft, a rotor slot, a rotor sub-slot, one or more current carrying parts within a rotor, or a combination thereof.

Also, used herein, "heat convection enabling component" refers to a temperature affecting component of the electro-mechanical device enabling the electro-mechanical device to maintain its temperature within predefined limits. According to the present invention, the heat convection enabling component is at least one ventilation channel disposed within at least one conductor. According to an embodiment, the ventilation channel includes that of an axially cooled rotor as well as a radially cooled rotor.

Also, used herein the term "coating" refers to a chemical compound comprising a Graphene derivative. The Graphene derivative includes, but is not limited to, a Graphitic oxide, a Graphene oxide, a Graphene, a functionalized Graphitic oxide, a functionalized Graphene oxide, a functionalized Graphene, or a combination thereof. Advantageously, the Graphene coating formed over the heat convection enabling component increases the current carrying capacity of the conductors because of its low electrical resistivity resulting in reduction of heating of the conductors and decrease in I<NUM>R losses. The decrease in I<NUM>R losses is proportional to a thickness of the coating. The thickness is largely governed by the manufacturing process being followed for the coating. Advantageously, the thickness of the coating is of about <NUM> millimetres to about <NUM> millimetre. Moreover, because of low thermal conductivity of Graphene, the heat dissipation in the conductors is enhanced thus resulting in an improved current carrying capacity of the conductors due to an increased flow of the excitation current in the rotor conductors. This increase in turn is utilized for power upgrades of the electro-mechanical device employing the coated article in its rotor. Furthermore, Graphene coating reduces corrosion caused in and around the conductors, thereby increasing life and operational efficiency of the electro-mechanical device such as an electric generator or an electric motor.

According to the present invention, the Graphene derivative is applied as a coating over any suitable surface of the conductors and the heat convection enabling component by any suitable application method. A suitable surface includes, but is not limited to, a substrate, a base coat over the substrate, a plurality of coatings over the substrate, or a combination thereof wherein the substrate refers to one or more surfaces of the conductors and the heat convection enabling components. Suitable application method comprises one or more of a plurality of processes comprising, for example, Chemical Vapour Deposition (CVD), screen printing, electrophoresis, thermal spray coating, low temperature application processes, and other chemical & electrochemical techniques or a combination thereof. Low temperature application processes include, but are not limited to, spray coating, painting, dipping, or a combination thereof.

Also disclosed herein is a rotor for an electro-mechanical device having a shaft and a winding wound within a plurality of rotor slots. One or more of the rotor slots are configured as a coated article comprising a plurality of conductors positioned within the rotor slots, and at least one heat convection enabling component in operable connection with one or more of the conductors.

Also disclosed herein is an electro-mechanical device having a stator and a rotor comprising a shaft and a winding wound within a plurality of rotor slots configured as the aformentioned coated article having a plurality of conductors positioned within the rotor slots, and at least one heat convection enabling component in operable connection with one or more of the conductors. The electromechanical device is an electric generator or an electric motor.

The above-mentioned and other features of the invention will now be addressed with reference to the accompanying drawings of the present invention. The illustrated embodiments are intended to illustrate, but not limit the invention.

Various embodiments are described with reference to the drawings, wherein like reference numerals are used to refer to like elements throughout. In the following description, for the purpose of explanation, numerous specific details are set forth in order to provide thorough understanding of one or more embodiments.

<FIG> illustrates a sectional view of a rotor slot <NUM> having direct-cooled rotor windings, as an embodiment of a coated article in accordance to the present invention. A slot cell <NUM> of the rotor slot <NUM> houses therewithin multiple conductors <NUM> forming a rotor winding, each turn of which is separated by an inter-turn insulation layer <NUM>. The conductors <NUM> are made of Copper and carry a direct current therewithin. The rotor slot <NUM> comprises at least one ventilation channel <NUM> disposed within at least one conductor <NUM>. The rotor slot <NUM> comprises Graphene coating 201A, 201B as shown in <FIG>. Graphene coating 201A is deposited on inner walls of each of the ventilation channels <NUM>. Graphene coating 201B is deposited on outer surfaces of the conductors <NUM> such that the Graphene coating 201B is sandwiched between the conductor <NUM> and the inter-turn insulation layer <NUM>, and between the conductor <NUM> and the slot cell <NUM>. The Graphene coating 201A, 201Bis in a thickness ranging about <NUM> to <NUM>. The Graphene coating 201A inside the ventilation channels <NUM> allows more heat to be removed via cooling media circulated in the rotor directly. The Graphene coating 201B on the outer surfaces of the conductors <NUM> allows more heat to conduct to the rotor body and/or end region of the rotor, from where the heat will be removed via the cooling media. This allows flow of additional current through the rotor, that is, the conductors <NUM>, thereby, increasing the current carrying capacity of the rotor.

<FIG> illustrate a rotor <NUM> of an electric generator, comprising rotor slots <NUM> shown in <FIG>, as an embodiment of a coated article in accordance to the present invention. <FIG> illustrates the rotor <NUM> comprising a shaft <NUM> having about two third of its peripheral area <NUM> covered with windings inserted into rotor slots <NUM>. <FIG> illustrates rotor slots <NUM> made in the rotor shaft <NUM>, each configured as a coated article disclosed in the detailed description of <FIG>.

<FIG> illustrates a sectional view of an active part of an electric generator <NUM> having a stator <NUM> and a rotor <NUM> with the rotor slots <NUM> shown in <FIG>, in accordance to the present invention. The rotor <NUM> is as disclosed in the detailed description of <FIG>, <FIG>. The rotor slots <NUM> are configured as a coated article as disclosed in the detailed description of <FIG>.

Claim 1:
A coated article (<NUM>) for an electro-mechanical device (<NUM>), having:
- a plurality of conductors (<NUM>) carrying a current therewithin,
- a heat convection enabling component (<NUM>) disposed in operable connection with one or more of the conductors (<NUM>),
- wherein the heat convection enabling component (<NUM>) is at least one ventilation channel (<NUM>) disposed within at least one conductor (<NUM>),
- wherein a coating (201A, 201B) is applied at least partially on one or more of the conductors (<NUM>) and on the heat convection enabling component (<NUM>), characterized in that
- the plurality of conductors (<NUM>) carries a direct current therewithin,
- the coating (201A, 201B) comprises a Graphene derivative and
- the coating (201A) formed over the heat convection enabling component (<NUM>) is configured to increase the current carrying capacity of the conductors.