Patent Application
20200136440
Exemplary embodiments pertain to the art of stators for electric machines and, more particularly, to a stator core comprising carbon fibers and cobalt.
Electric machines, such as motors and generators, are commonly found in industrial, commercial, aerospace, and consumer settings. Such machines are employed to drive various kinds of devices, including pumps, conveyors, compressors, fans, and others. In the case of electric motors and generators, these devices generally include a stator, which has a plurality of stator windings, surrounding a rotor.
The stator is often made from laminated heavy metals such as iron. As a result, the heavy weight of the stator can become problematic in weight sensitive contexts, for example, electric motors for aircraft and other mobile equipment. It is therefore important that weight reduction alternatives to heavy iron composites be available for formation of the stator. The stator also produces excess heat during operation due to, for example, eddy current losses in the stator. Excess heat can reduce the efficiency of the machine and result in failure. Therefore, it is important that the electric machine can efficiently dissipate excess heat, thereby reducing temperatures, improving efficiency, and increasing durability.
Disclosed is an electric machine, comprising: a rotor; and a stator core radially outward from the rotor, the stator core being stationary relative to the rotor during operation; wherein the stator core comprises: carbon fibers and cobalt carbide, and wherein the stator core is greater than or equal to 40% cobalt by weight.
Also disclosed is a method of forming a stator core such that the stator core comprises carbon fibers and cobalt carbide, and wherein the stator core is greater than or equal to about 40% cobalt by weight, the method comprising: coating a plurality of carbon fiber sheets with a mixture of resin and cobalt powder, wherein the resin is a phenolic resin, a powdered pitch resin, or a combination comprising at least one of the foregoing; pressing together the plurality of carbon fiber sheets; heat treating the plurality of carbon fiber sheets to form cobalt carbide in the carbon fiber sheets; and forming a plurality of laminations from the resulting mixture to produce the stator core.
The following descriptions should not be considered limiting in any way. With reference to the accompanying drawing, like elements are numbered alike:
A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figure.
Referring to
The electric machine 10 can be a motor or a generator that is able to drive (via mechanical or electrical output) various devices, including pumps, conveyors, compressors, fans, rollers, wheels, or other machines. The electric machine 10 can be a generator or motor of any architecture that has a wound stator including a permanent magnet, synchronous, induction, or switched reluctance. Additionally, all components of the electric machine 10 are not shown, and the electric machine 10 can include other components, such as those particularly suited for the intended use of the electric machine 10.
Shaft 12 extends axially along an axis of rotation (not shown), which is at a radial center 20 of electric machine 10. The shaft 12 is a cylinder with a consistent or varying radius that can be solid, hollow, or multiple pieces fastened together, depending on design considerations. The shaft 12 can be made from a variety of materials, including steel, aluminum, or other materials able to handle high stresses without deformation or failure. When used as a motor, energy can be outputted from the electric machine 10 through the rotation of the shaft 12, which would be used to drive exterior devices. Alternatively, when used as a generator, rotational energy can be inputted into the electric machine 10 by driving the shaft 12 to rotate which, in turn, induces voltage in stator windings (not shown). The induced voltage can be outputted to supply electricity to exterior devices.
The rotor 14 is radially outward from and extends axially along the axis of rotation and the shaft 12. The rotor 14 is fastened or incorporated into the shaft 12 so that the shaft 12 and the rotor 14 rotate in unison. The rotor 14 can be a lamination stack, which is a plurality of cross-sectional pieces (called sheets) fastened together to create a final piece (called the stack) having the dimensions of the rotor 14. The lamination stack of the rotor 14 can be a variety of materials, such as steel or another material, and the sheets can be fastened together through adhesive, resin, or another means, such as welding.
The rotor 14 can include multiple rotor windings, which are not shown in
The stator core 16 extends axially parallel to the axis of rotation and the shaft 12 to be radially outward from the rotor 14. The stator core 16 is physically separate from the rotor 14 so that a gap is present between an outermost surface of the rotor 14 and an innermost surface of the stator core 16. In operation, the stator core 16 is stationary relative to the shaft 12 and the rotor 14, and the shaft 12 and the rotor 14 rotate within the stator core 16 to either induce voltage in stator windings or the rotor windings on the rotor 14 depending on the excitation source. The stator core 16 has a cylindrical shape that extends axially parallel to the axis of rotation. The mechanical teeth 18 are illustrated as multiple inward projections extending from the radially inner surface of the stator core 16 towards the rotor 14. The stator 16 can have a plurality of mechanical teeth 18, including two, four, six, eight, ten, or more teeth 18. The stator windings can be wrapped around the mechanical teeth 18 so that each stator winding is wrapped around one corresponding tooth of the mechanical teeth 18. The stator windings are each continuous wires that are electrically conductive and wrapped multiple times around the mechanical teeth 18. The wires of the stator windings can be arranged in a single layer or can be multiple layers of wires.
During operation of the electric machine 10 as a generator, stator windings can either be energized with electricity to act as an electromagnet to induce voltage in the rotor 14, which is outputted to exterior devices, or the stator windings can be energized by the rotation of the magnetic field from the electrically energized rotor 14 (which creates an electromagnet) or permanent magnets of the rotor 14 so that the voltage induced in the stator windings is outputted to exterior devices.
The heat fins 22 are heat dissipating projections that extend radially outward from an outer surface of the stator core 16 away from the rotor 14. The heat fins 22 allow heat from the stator core 16 to be dissipated radially outward by providing an increased surface area. Additionally, the shape and configuration of the heat fins 22 can be optimized for specific designs, such as reduced weight, minimal diameter increase, manipulation of the flow of cooling fluid, or maximum heat transfer (fluid pressure drop and increased heat transfer are proportional to one another).
The housing 28 has a cylindrical shape centered about the axis of rotation and is radially outward from the stator core 16. The housing 28 provides protection to the electric machine 10 to ensure the inner components (i.e., the shaft 12, the rotor 14, the stator core 16, and the heat fins 22) are not damaged during manufacturing, transportation, installation, and operation, as well as preventing unwanted particulate or fluid from entering the electric machine 10. For example, the housing 28 can provide electromagnetic shielding for the electric machine 10. The housing 28 can be made from a variety of materials, including steel, aluminum, plastic, or another material or combination of materials. The housing 28 can be made from one continuous and monolithic piece or can be a number of pieces fastened together. The housing 28 can include additional features, such as orifices to allow access to the inner components of the electric machine 10 or features that allow attachment of other components to the housing 28.
The stator core 16 and/or the housing 28 can comprise carbon fibers and cobalt carbide, wherein the stator core 16 and/or the housing 28 is greater than or equal to 40% cobalt by weight. For example, the stator core 16 and/or the housing 28 can include about 40% to about 70% cobalt by weight. The stator core 16 and/or the housing 28 can include about 5% to about 30% carbon fibers by weight. The stator core 16 and/or the housing 28 can include carbon fibers within a cobalt/cobalt carbide matrix. The carbon fibers can comprise carbon fiber cloth, graphene, chopped carbon fibers, carbon microfibers, carbon nanofibers, or a combination comprising at least one of the foregoing. The use of carbon fiber reinforcement can result in improved radial magnetic conductance and improved radial heat dissipation properties. The carbon fibers can have a laminar orientation (i.e., parallel layers of carbon fibers) or a random orientation within the stator core 16 and/or the housing 28. Laminar orientation of the carbon fibers can result in improved directional magnetic properties, for example, radial magnetic conductance along the direction of the fibers. Laminar orientation of the carbon fibers can also result in improved directional thermal properties, for example, radial heat dissipation along the direction of the fibers. The stator core 16 and/or the housing 28 can include about 0.01% to about 5% cobalt carbide by weight. The cobalt carbide may be nanoscale cobalt carbide, for example, an average molecular diameter of the cobalt carbide can be less than or equal to about 100 nanometers. The stator core 16 and/or the housing 28 can include less than or equal to about 1% iron, for example, the cobalt composite material can include 0% iron.
Referring to
Referring to
The term “about” is intended to include the degree of error associated with measurement of the particular quantity based upon the equipment available at the time of filing the application.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, element components, and/or groups thereof.
While the present disclosure has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the present disclosure. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present disclosure without departing from the essential scope thereof. Therefore, it is intended that the present disclosure not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this present disclosure, but that the present disclosure will include all embodiments falling within the scope of the claims.
