Patent Application
20150188391
Some embodiments described herein relate to electromagnetic machines and more particularly to dual-function structural and cooling elements for an electronic machine.
Permanent magnet electromagnetic machines (referred to as “permanent magnet machines” or “electromagnetic machines” herein) utilize magnetic flux from permanent magnets to convert mechanical energy to electrical energy or vice versa. Various types of permanent magnet machines are known, including axial flux machines, radial flux machines, and transverse flux machines, in which one component rotates about an axis or translates along an axis, either in a single direction or in two directions (e.g., reciprocating, with respect to another component). Such machines typically include windings to carry electric current through coils that interact with the flux from the magnets through relative movement between the magnets and the windings. In a common industrial application arrangement, the permanent magnets are mounted for movement (e.g., on a rotor or otherwise moving part) and the windings are mounted on a stationary part (e.g., on a stator or the like). Other configurations, typical for low power, inexpensive machines operated from a direct current source where the magnets are stationary and the machine's windings are part of the rotor (energized by a device known as a “commutator” with “brushes”) are also available, but will not be discussed in detail in the following text in the interest of brevity.
In an electric motor, for example, current is applied to the windings in the stator, causing a force or torque between the rotor and stator (e.g., causing the magnets and therefore the rotor to move relative to the windings), thus converting electrical energy into mechanical energy. In a generator, application of an external force to the generator's rotor causes the magnets to move relative to the windings, and the resulting generated voltage causes current to flow through the windings—thus converting mechanical energy into electrical energy. In an AC induction motor, the rotor is energized by electromagnetic induction produced by electromagnets that cause the rotor to move relative to the windings on the stator, which are connected directly to an AC power source and can create a rotating magnetic field when power is applied.
In operation, the rotor and/or the stator can be subject to significant heating, which may necessitate active or passive cooling. In large electromagnetic machines, cooling ducts, particularly thin wall cooling ducts disposed exterior to structural members, can be subject to damage during installation, maintenance, ice and/or snow loading, and/or high winds. In addition, ducting disposed around the rotor and/or stator can reduce the efficiency of a fluid-driven turbine by contributing to the drag loading of the structure. Furthermore, the driving mechanism for a cooling mechanism can contribute mass and/or mechanical complexity to the active section of the machine.
Thus, a need exists for improved apparatus and methods to increase the structural efficiency of an electromagnetic machine and/or improve the ability of the electromagnetic machine to provide cooling functions without an increase in components to the electromagnetic machine.
Apparatus and methods are described herein for providing a cooling system for an electromagnetic machine. In some embodiments, an apparatus includes a structure for an electromagnetic machine including a first support member that is configured to support a conductive winding or a magnet and a second support member that is disposed at a non-zero distance from the first support member. An elongate structural member has a first end coupled to the first support member and a second end coupled to the second support member and extends between the first support member and the second support member. The elongate structural member defines an interior channel that extends between the first end and the second end of the elongate structural member. The channel is configured to convey a cooling medium therethrough to cool at least a portion of the electromagnetic machine.
Some embodiments described herein relate to a structure for an electromagnetic machine having an outer support member and an inner support member. The outer support member can include a conductive winding and/or a magnet. An elongated structural member can be substantially radially disposed between the outer support member and the inner support member and can define a channel configured to convey a cooling medium to cool at least a portion of the electromagnetic machine.
In some embodiments, an apparatus includes a structure for an electromagnetic machine including a first support member that is configured to support a conductive winding or a magnet and a second support member that is disposed at a non-zero distance from the first support member. An elongate structural member has a first end coupled to the first support member and a second end coupled to the second support member and extends between the first support member and the second support member. The elongate structural member defines an interior channel that extends between the first end and the second end of the elongate structural member. The channel is configured to convey a cooling medium therethrough to cool at least a portion of the electromagnetic machine. In some embodiments, the second support member is disposed radially spaced from the first support member and the structural member extends radially between the first support member and the second support member.
In some embodiments, an apparatus includes a structure for an electromagnetic machine that includes a first support member configured to support a conductive winding or a magnet and a second support member disposed at a non-zero distance from the first support member. An elongate structural member has a first end coupled to the first support member and a second end coupled to the second support member and extends between the first support member and the second support member. The elongate structural member defines a first interior channel extending between the first end and the second end of the elongate structural member and a second interior channel in fluid communication with the first interior channel that extends between the first end and the second end of the elongate structural member. The first interior channel is configured to convey a cooling medium in a first radial direction and the second interior channel is configured to receive the cooling medium from the first interior channel and convey the cooling medium in a second radial direction opposite the first direction. The cooling medium is configured to cool at least a portion of the electromagnetic machine. In some embodiments, the second support member is disposed radially spaced from the first support member and the structural member extends radially between the first support member and the second support member.
In some embodiments, an apparatus includes a structural cooling device for an electromagnetic machine that includes an elongate structural member having a first end couplable to an inner support member of the electromagnetic machine, and a second end couplable to an outer support member of the electromagnetic machine. The elongate structural member extends radially between the inner support member and the outer support member and is configured to resist at least one of radial, axial or rotational deflection of the outer support member relative to the inner support member when coupled thereto. The elongate structural member defines an interior channel extending between the first end and the second end of the elongate structural member and configured to receive a cooling medium therethrough. A source of cooling medium is couplable to the elongate structural member and configured to convey the cooling medium to the interior channel of the elongate structural member. The cooling medium is configured to cool at least a portion of the electromagnetic machine.
Electromagnetic machines as described herein can be various types of synchronous and asynchronous machines, such as wound field synchronous machines, induction machines, doubly fed induction machines (presently commonly found in the wind energy conversion market), permanent magnet machines, including axial flux machines, radial flux machines, and transverse flux machines, in which one component rotates about an axis or translates along an axis, either in a single direction or in two directions (e.g., reciprocating, with respect to another component). Such machines typically include windings to carry electric current through coils that interact with the flux from the magnets through relative movement between the magnets and the windings. In a common industrial application arrangement (including the embodiments described herein), the permanent magnets are mounted for movement (e.g., on a rotor or otherwise moving part) and the windings are mounted on a stationary part (e.g., on a stator or the like). Some embodiments described herein focus on the permanent magnet variety of electromagnetic machines.
Although the embodiments described herein are described with reference to use within an electromagnetic machine (e.g., a rotor/stator assembly as described herein), it should be understood that the embodiments described herein can also be used within other machines or mechanisms. Furthermore, while described herein as being implemented in or on a stator assembly, it should be understood that the embodiments described herein can be implemented in or on a stator and/or a rotor assembly or another mechanism within an electromagnetic machine having a structural member.
Some embodiments described herein address axial field, air core, surface mounted permanent magnet generator rotor/stator configurations; but it should be understood that the features, functions and methods described herein can be implemented in radial field, transverse field and embedded magnet configurations that employ either an air core or iron core winding configuration. Embodiments described herein can also be applied to electrically excited rotors commonly found in industrial and utility applications, such as wound field synchronous machines and devices common in the wind energy conversion industry known as “doubly fed induction generators.” Furthermore, although the embodiments described herein refer to relatively large electromagnetic machines and/or components such as those found in wind power generators, it should be understood that the embodiments described herein are not meant to limit the scope or implementation of the apparatus and methods to that particular application.
As used herein, the term “axial deflection” can refer to, for example, the deflection (e.g., the bending, swaying, deforming, moving, etc.) of a component in a direction parallel to an axis of rotation of an electromagnetic machine. For example, in a generator having a rotor that is rotatably movable relative to a stator, a component of the stator can be said to have axial deflection when a portion of the component, is moved in a direction along an axis of rotation of the rotor.
As used herein, the term “rotational deflection” can refer to, for example, the deflection (e.g., the bending, swaying, deforming, moving, etc.) of a component in a direction of rotation of an electromagnetic machine. Such deflection can also be referred to as torsional deflection. In instances of large components and structures used in rotating flux machines (e.g., as seen in wind power generators) a small amount of deflection in the rotational direction can be considered tangential deflection near the outer extent of the machine.
As used herein, the term “radial deflection” can refer to, for example, deflection in a direction radially inward toward an axis of rotation of an electromagnetic machine or radially outward from the axis of rotation. For example, an outer support member of a stator or of a rotor can deflect in a radial direction toward an inner support member (e.g., hub) of the stator or rotor.
In an alternative embodiment, the generator structure 100 can be a rotor assembly included in an electromagnetic machine. For example, as described above, a rotor assembly can include one or more rotor portions that move relative to a stator. In such embodiments where the generator structure 100 is a rotor assembly, the rotor assembly can include or support one or more magnetic flux generating members, such as, for example, magnets (e.g., a magnet pole assembly, or array of magnets) or windings (each not shown in
As shown in
The second support member 120 can be any suitable structure. For example, in some embodiments, the second support member 120 can be substantially annular and can be configured as a hub, disposed radially inwardly from the first support member 110. In such an arrangement, the first support member 110 may be referred to as an outer support member, and the second support member 120 may be referred to as an inner support member.
The generator structure 100 further includes at least one elongate structural member 130 disposed between the first support member 110 and the second support member 120. In some embodiments, the generator structure 100 can include structural members such as those described in U.S. patent application Ser. No. 13/692,089, entitled “Structure for an Electromagnetic Machine Having Compression and Tension Members,” the disclosure of which is incorporated herein by reference in its entirety. The generator structure 100 can optionally include one or more elongate tension members 150, a forcing mechanism 180 and a source of a cooling medium 170.
The elongate structural member 130 (also referred to herein as “structural member” or “compression member”) can provide structural support to the first support member 110 from the second support member 120. For example, the structural member 130 can include a first end coupled to the first support member 110 and a second end coupled to the second support member 120. For example, in some embodiments, the structural member 130 includes flanged end portions configured to be coupled to the first support member 110 and the second support member 120 (e.g., welded, bolted, riveted, pinned, adhered, or any combination thereof). In some embodiments the structural member 130 can be in compression. The structural member 130 can be formed from any suitable material such as a metal, metal alloy (e.g., steel or steel alloy), and/or composite.
The structural member 130 can also be any suitable shape, size, or configuration. For example, in some embodiments, the structural member 130 can be tubular and define and/or contain one or more cooling channels 135. For example, the structural member 130 can have a cross-section that is square, circular, elliptical, rectangular, oval, etc. In some embodiments, the structural member 130 can be a substantially hollow, closed structure such as, for example, a box tubing (e.g., square or rectangular tubing). The structural member 130 can define a single cooling channel 135 suitable to convey a cooling medium from a first end of the structural member 130 to a second end of the structural member 130 to provide cooling to at least a portion of the electromagnetic machine. In other embodiments, the structural member 130 can include multiple channels. For example, internal structures, such as walls, baffles, tubing, etc., can be disposed within an interior of the structural member 130 and be operable to define one or more cooling channels 135. For example, in such an embodiment, a first channel can deliver or convey the cooling medium in a first direction and the second channel can be a return path for the cooling medium. Such an embodiment can be applied to, for example, a closed loop cooling system described in more detail below. In one such embodiment, the structural member 130 can include one or more longitudinal interior walls that divide the interior region or volume of the structural member 130 into two (or more) cooling channels 135. In another embodiment, the structural member 130 can contain pipes, hoses, and/or tubing suitable to convey a cooling medium (see, e.g.,
The optional elongate tension member 150 (also referred to herein as “tension member”) can be any suitable shape, size, or configuration. In some embodiments, the tension member 150 can be a tie rod or a cable such as, for example, a steel braided cable or the like. In some embodiments, the tension member 150 can include a first end portion coupled to a portion of the first support member 110 and a second end portion coupled to a portion of the second support member 120. In some embodiments, the tension member 150 includes a first end portion coupled to a portion of the compression member 130 and a second end portion coupled to the second support member 120. In other embodiments, the first end portion of the tension member 150 can be coupled to a portion of the structural member 130 and the second end portion of the tension member 150 can be coupled to a portion of an adjacent compression member (not shown in
The structural member 130 and/or the tension member 150 can be collectively configured to substantially increase the structural efficiency and/or increase resistance to deflection of the generator structure 100. For example, in some embodiments, the structural member 130 can be configured to resist axial, radial, and/or rotational deflection of the first support member 110 with respect to the second support member 120. In such embodiments, the cross-sectional shape of the structural member 130 can be configured to resist the deflection. In addition to or alternatively, a force can be applied to the structural member 130 such that the structural member 130 further resists axial and/or radial deflection.
The cooling medium can be, for example, air, water, refrigerant, and/or any other gas, liquid, and/or two-phase coolant that can be conveyed along a length or portion of a length of the support member(s) 130 via the cooling channel(s) 135 of the structural member(s) 130. The cooling medium can reduce the temperature of at least a portion of the generator structure and/or the electromagnetic machine in which the generator structure is disposed. For example, the cooling medium can carry thermal energy away from a portion of the electromagnetic machine to maintain a lower operating temperature than would otherwise be expected without such a cooling medium being introduced into the machine.
The cooling medium can be provided via the source of cooling medium 170. For example, a reservoir or other device can be coupled to the generator structure 130 and be in fluid communication with the cooling channel(s) 135. Alternatively, the cooling medium source 170 may be an inlet, such as an intake that supplies cooling air from the external environment to the cooling channel(s) 135. The forcing mechanism 180 can be fluidically coupled to for example, a first end of the elongate structural member(s) 130 and can be used to increase a flow of the cooling medium within or through the cooling channel(s) 135. The forcing mechanism 180 can be, for example, one or more fans, pumps, compressors or other suitable mechanism to induce or increase a flow of the cooling medium within or through the cooling channel(s) 135. Such components can be, for example, coupled to the rotor of the electromagnetic machine to passively encourage further air flow. In some embodiments, such forcing mechanism(s) 180 can be disposed on or near the first support member 110 or the second support member 120.
The forcing mechanism and/or the source of cooling medium 170 can each be coupled to, for example, the second support member 120, which can reduce the complexity and mass in the active section (e.g., near the windings and/or magnets) of the electromagnetic machine. For example, piping and/or ducting carrying the cooling medium from the source 170 to the cooling channel(s) 135 can be reduced, which can reduce the opportunity for mechanical failure, for example during installation, maintenance, ice and/or snow loading, and/or high winds. For example, in an embodiment where the second support member is an inner support member 120, e.g. includes a central hub and the first support member is an outer support member 110 formed as an annular ring, a centrally disposed forcing mechanism 180 can circulate the cooling medium through the structural member 130 without the need for exterior ducting or piping. In addition, coupling the forcing mechanism to the inner support member 120 can further reduce drag loading of the structure (e.g., of a rotor) which may occur if additional duct surface is exposed to wind loading. In some embodiments, the forcing mechanism 180 can be coupled to a different component of the generator structure 100 and/or the electromagnetic machine in which the generator structure 100 is included.
In some embodiments, the forcing mechanism 180 can be an integral component of the generator structure 100, including such features as airfoils, blades, and/or vanes which can produce a pressure differential as the rotor of the generator structure rotates. Thus, in such an embodiment, a separate forcing mechanism distinct from the generator may not be necessary. In other embodiments, a pressure differential caused by the generator structure 100 can induce a flow through the cooling channel(s) 135 without the use of a forcing mechanism 180.
In some embodiments, the generator structure can include one or more heat transfer members 190 that can be thermally coupled to the elongate structural member(s) 130 and/or to the cooling medium. The heat transfer members 190 can extract heat from the cooling medium and reject it to the external environment. For example, the fluid may be ‘hot’ as it passes through the structural member 130, and can be cooled by the ambient air passing by the structural member 130. The heat transfer members 190 can be, for example, a heat sink, disposed inside or outside the structural member(s) 130, heat pipes extending through an interior of the structural member(s) 130, a feature or component integrally formed with the structural member(s) 130, or a separate component coupled to the structural member(s) 130 that can be formed with the same or different material as the structural member(s) 130.
The generator structure 100 can also optionally include a flow guide (not shown in
In some embodiments, the generator structure 100 can include an “open-loop” cooling system, such that the cooling medium can be discharged to the atmosphere. For example, an end portion of the structural member 130 can define an opening in fluid communication with the cooling channel 135 such that the cooling medium can be discharged out through the opening. For example, a cooling medium such as air can be discharged from the structural member 130. In other embodiments, the generator structure 100 can include a “closed-loop” cooling system in which the cooling medium is circulated through one or more structural members 130 and is contained within the cooling system. For example, the cooling medium can circulate from a reservoir (e.g., source of the cooling medium), through the structural member 130 and return to the reservoir. For example, a first cooling channel 135 can carry the cooling medium in a first direction (e.g., towards the first support member 110) and a second cooling channel 135 can carry the cooling medium in a second direction (e.g., away from the first support member 110). Although the direction of flow of the cooling medium is described as flowing in a radial direction from the inner support member 120 towards the outer support member 110, it should be understood that in alternative embodiments, the direction of flow of the cooling medium can be from the outer support member 110 radially inward towards the inner support member 120. In some embodiments, an “open-loop” cooling system can also include a return path or channel to provide an exhaust path for the cooling medium.
As shown in
The generator structure 200 can be any suitable structure included in an electromagnetic machine. For example, in this embodiment, the generator structure 200 is a stator. As described above in reference to
The compression member 230 includes a first end portion 231 and a second end portion 232 and is configured to extend between the outer support member 210 and the inner support member 220. The compression member 230 can be any suitable shape, size, or configuration. For example, in some embodiments, the compression member 230 can have a substantially rectangular or square cross-section. The first end portion 231 of the compression member 230 is coupled to the outer support member 210 and the second end portion 232 of the compression member 230 is coupled to the inner support member 220. More specifically, the first end portion 231 and the second end portion 232 can be any suitable shape and/or include any suitable structure to couple to the outer support member 210 and the inner support member 220, respectively, and simultaneously convey a cooling medium. For example, in some embodiments, the first end portion 231 and the second end portion 232 can form a flange configured to mate with a portion of the outer support member 210 and a portion of the inner support member 220, respectively. In some embodiments, the first end portion 231 and the second end portion 232 can be bolted to the outer support member 210 and the inner support member 220, respectively. In other embodiments, the end portions 231 and 232 can be riveted, welded, pinned, adhered, or any combination thereof.
The first tension member 250 includes a first end portion 251 coupled to a portion of the compression member 230 and a second end portion 252 coupled to the inner support member 220 or a portion of an adjacent compression member 230′. Similarly, the second tension member 255 includes a first end portion 256 coupled to a portion of the compression member 230 and a second end portion 257 coupled to the inner support member 220 of a portion of an adjacent compression member 230′. As shown in
The first tension member 250 and the second tension member 255 can be any suitable shape, size, or configuration. For example, in some embodiments, the first tension member 250 and the second tension member 255 are cable (e.g., steel braided cable or the like). In some embodiments, the first tension member 250 and the second tension member 255 can be substantially similar. In other embodiments, for example, the first tension member 250 and the second tension member 255 can have different shapes, sizes and/or configurations. For example, the first tension member 250 and the second tension member 255 can be cables and can have a different diameter (e.g., the cables are of a different diameter, thickness, or perimeter).
In this embodiment, the structural member 330 defines a cooling channel 335, a first opening 334 on a first end portion of the structural member 330 and a pair of second openings 336 on a second end portion of the structural member 330, each in fluid communication with the cooling channel 335. As described above for previous embodiments, a cooling medium can enter the cooling channel 335 via the first opening 334, be conveyed through the cooling channel 335, and exit through the second openings 336. Thus, in this embodiment, the cooling medium can be conveyed, for example, in a radial direction from near an inner support member toward an outer support member of the generator structure 300. Alternatively, the cooling medium can be conveyed through the second openings 336, through the cooling channel 335 and exit the first opening 334. Thus, in such an embodiment, the cooling flow is in a radial direction from near the outer support member toward an inner support member of the generator structure 300. Two flow guides 338 are disposed on the second end of the structural member 330 and can direct the cooling medium through the second opening 336 and through an opening 333 defined between the two flow guides 338. In this embodiment, the cooling system is an open-loop system in that the cooling medium exits the opening 334 or 336, 333 and flows freely over and/or through a portion of the generator structure and/or the electromagnetic machine.
Although not shown in
In this embodiment, the structural member 430 defines a cooling channel 435, a first opening 434 defined on a first end portion of the structural member 430 and a second opening 436 defined on a second end portion of the structural member 430, each in fluid communication with the cooling channel 435. As described above for previous embodiments, a cooling medium can enter the cooling channel 435 via the first opening 434, and be conveyed through the cooling channel 435, and exit through the second opening 436. Thus, in this embodiment, the cooling medium can be conveyed, for example, in a radial direction from an inner support member to an outer support member of the generator structure 400.
As with generator structure 300, the generator structure 400 includes flow guides 438 disposed on the second end of the structural member 430 and that can direct the cooling medium towards the second opening 436. In this embodiment, the generator structure 400 also includes flow guide 440. The flow guides 440 can distribute the flow of cooling medium over a desired region of the generator structure 400.
As with the generator structure 300, in this embodiment, the cooling system is an open-loop system in that the cooling medium exits the opening 436 and flows freely over and/or through a portion of the generator structure and/or the electromagnetic machine.
Although not shown in
As shown in
Although not shown in
In some embodiments, two cooling pipes can be used. For example, a first cooling pipe can be used as the delivery channel for the cooling medium and the second cooling pipe can be used as the return path for the cooling medium. In such an embodiment, the two cooling pipes can be formed as two separate components coupled together with a connection or as a single cooling pipe that is bent, curved or otherwise formed such that the cooling pipes are disposed along side each other. In an alternative embodiment, a single cooling pipe can be included and used as an open loop cooling system. For example, in such an embodiment, the cooling medium can flow in a radial direction through the cooling pipe and exit, for example, at an end portion near an outer support member or an inner support member.
While various embodiments have been described above, it should be understood that they have been presented by way of example only, not limitation, and various changes in form and details may be made. Any portion of the apparatus and/or methods described herein may be combined in any combination, except mutually exclusive combinations. The embodiments described herein can include various combinations and/or sub-combinations of the functions, components and/or features of the different embodiments described. For example, although some embodiments are shown and described as having flow guides positioned adjacent to an outlet of a cooling channel, in addition or alternatively, flow guides can be positioned adjacent to an inlet of a cooling channel, along the length of the flow channel, and/or in any other suitable position to, for example, direct a flow and/or reduce pressure losses of a cooling medium.
In addition, it should be understood that the features, components and methods described herein for each of the various embodiments can be implemented in a variety of different types of electromagnetic machines, such as, for example, axial and radial machines that can support rotational movement of a rotor assembly relative to a stator assembly.
