Patent Description:
Electric machines, such as electric motors or electric generators, are used in energy conversion. In the aircraft industry, it is common to combine a motor mode and a generator mode in the same electric machine, where the electric machine in motor mode functions to start the engine, and, depending on the mode, also functions as a generator. Regardless of the mode, an electric machine typically includes a rotor having rotor windings that are driven to rotate by a source of rotation, such as a mechanical or electrical machine, which for some aircraft may be a gas turbine engine. A cap or end support can contribute to retaining the rotor windings as they rotate.

<CIT> provides separate, relatively narrow shrink rings, separated from each other by axial air gaps, that press winding heads inwardly on washer rings attached to the rotor. <CIT> discloses a two-piece winding support for rotor windings.

The invention relates to a rotor for an electric machine as claimed in claim <NUM>.

Aspects of the disclosure can be implemented in any environment using an electric motor regardless of whether the electric motor provides a driving force or generates electricity. For purposes of this description, such an electric motor will be generally referred to as an electric machine, electric machine assembly, or similar language, which is meant to clarify that one or more stator/rotor combinations can be included in the machine. While this description is primarily directed toward an electric machine providing power generation, it is also applicable to an electric machine providing a driving force or an electric machine providing both a driving force and power generation. Further, while this description is primarily directed toward an aircraft environment, aspects of the disclosure are applicable in any environment using an electric machine. Additionally, non-limiting aspects of the disclosure are applicable for distributed windings, concentric windings, or a combination thereof. Thus, a brief summary of a contemplated environment should aid in a more complete understanding.

While "a set of" various elements will be described, it will be understood that "a set" can include any number of the respective elements, including only one element. As used herein, the terms "axial" or "axially" refer to a dimension along a longitudinal axis of a generator or along a longitudinal axis of a component disposed within the generator.

As used herein, the terms "radial" or "radially" refer to a dimension extending between a center longitudinal axis, an outer circumference, or a circular or annular component disposed thereof. The use of the terms "proximal" or "proximally," either by themselves or in conjunction with the terms "radial" or "radially," refers to moving in a direction toward the center longitudinal axis, or a component being relatively closer to the center longitudinal axis as compared to another component.

All directional references (e.g., radial, axial, upper, lower, upward, downward, left, right, lateral, front, back, top, bottom, above, below, vertical, horizontal, clockwise, counterclockwise) are only used for identification purposes to aid the reader's understanding of the disclosure, and do not create limitations, particularly as to the position, orientation, or use thereof. Connection references (e.g., attached, coupled, connected, and joined) are to be construed broadly and can include intermediate members between a collection of elements and relative movement between elements unless otherwise indicated. As such, connection references do not necessarily infer that two elements are directly connected and in fixed relation to each other.

As used herein, a "wet" cavity generator includes a cavity housing the rotor and stator that is exposed to free liquid coolant (e.g. coolant freely moving within the cavity). In contrast, a "dry" cavity generator the rotor and stator can be cooled by coolant contained within limited in fluidly sealed passages (e.g. non-freely moving about the cavity).

The exemplary drawings are for purposes of illustration only and the dimensions, positions, order and relative sizes reflected in the drawings attached hereto can vary.

<FIG> illustrates a gas turbine engine <NUM> having an accessory gear box (AGB) <NUM> and an electric machine or generator <NUM> according to an aspect of the disclosure. The gas turbine engine <NUM> can be a turbofan engine, such as a General Electric GEnx or CF6 series engine, commonly used in modern commercial and military aviation or it could be a variety of other known gas turbine engines such as a turboprop or turboshaft. The AGB <NUM> can be coupled to a turbine shaft (not shown) of the gas turbine engine <NUM> by way of a mechanical power take off <NUM>. The gas turbine engine <NUM> can be any suitable gas turbine engine used in modern aviation or it could be a variety of other known gas turbine engines such as a turboprop or turboshaft. The type and specifics of the gas turbine engine <NUM> are not germane to the disclosure and will not be described further herein. While a generator <NUM> is shown and described, aspects of the disclosure can include any electrical machine or generator.

<FIG> more clearly illustrates a non-limiting example generator <NUM> and its housing <NUM> in accordance with aspects of the disclosure. The generator <NUM> can include a clamping interface <NUM>, used to clamp the generator <NUM> to the AGB (not shown). Multiple electrical connections can be provided on the exterior of the generator <NUM> to provide for the transfer of electrical power to and from the generator <NUM>. The electrical connections can be further connected by cables to an electrical power distribution node of an aircraft having the gas turbine engine <NUM> to power various items on the aircraft, such as lights and seat-back monitors. The generator <NUM> can include a liquid coolant system for cooling or dissipating heat generated by components of the generator <NUM> or by components proximate to the generator <NUM>, one non-limiting example of which can be the gas turbine engine <NUM>. For example, the generator <NUM> can include a liquid cooling system using oil as a coolant.

The liquid cooling system can include a cooling fluid inlet port <NUM> and a cooling fluid outlet port <NUM> for controlling the supply of coolant to the generator <NUM>. In one non-limiting example, the cooling fluid inlet and output ports <NUM>, <NUM> can be utilized for cooling at least a portion of a rotor or stator of the generator <NUM>. The liquid cooling system can also include a second coolant outlet port <NUM>, shown at a rotatable shaft portion of the generator <NUM>. Optionally, by way of non-limiting example, the liquid cooling system can include a rotatable shaft coolant inlet port <NUM> or a generator coolant outlet port <NUM>. While not shown, aspects of the disclosure can further include other liquid cooling system components, such as a liquid coolant reservoir fluidly coupled with the cooling fluid inlet port <NUM>, the rotatable shaft coolant inlet port <NUM>, the cooling fluid outlet port <NUM>, or the generator coolant outlet port <NUM>, and a liquid coolant pump to forcibly supply the coolant through the ports <NUM>, <NUM>, <NUM>, <NUM> or generator <NUM>.

A non-limiting interior of the generator <NUM> is best seen in <FIG>, which is a cross-sectional view of the generator <NUM> shown in <FIG> taken along line III-III. A hollow rotatable shaft <NUM> is located within the generator <NUM> and is the primary structure for supporting a variety of components. The rotatable shaft <NUM> can have a single diameter or one that can vary along its length. The rotatable shaft <NUM> is supported by spaced bearings <NUM> and <NUM> and configured to rotate about a rotational axis <NUM>. Several of the elements of the generator <NUM> have a fixed component and a rotating component, with the fixed component fixed relative to the housing <NUM> and with the rotating component being provided on, or rotatably fixed relative to the rotatable shaft <NUM>. Examples of these elements can include a main machine <NUM>, housed within a main machine cavity <NUM>, an exciter <NUM>, and a permanent magnet generator (PMG) <NUM>. The corresponding rotating component comprises a main machine rotor <NUM>, an exciter rotor <NUM>, and a PMG rotor <NUM>, respectively, and the corresponding fixed component comprises a main machine stator <NUM> or stator core, an exciter stator <NUM>, and a PMG stator <NUM>. In this manner, the main machine rotor <NUM>, exciter rotor <NUM>, and PMG rotor <NUM> are disposed on and co-rotate with the rotatable shaft <NUM>. The fixed components can be mounted to any suitable part of the housing <NUM>, and include the main machine stator <NUM>, exciter stator <NUM>, and PMG stator <NUM>. Collectively, the fixed components define an interior through which the rotatable shaft <NUM> extends and rotates relative to.

It will be understood that the main machine rotor <NUM>, exciter rotor <NUM>, and PMG rotor <NUM> can have a set of rotor poles, and that the main machine stator <NUM>, exciter stator <NUM>, and PMG stator <NUM> can have a set of stator poles. The set of rotor poles can generate a set of magnetic fields relative to the set of stator poles, such that the rotation of the rotor magnetic fields relative to the stator poles generate current in the respective stator components.

At least one of the rotor poles and stator poles can be formed by a core with a post and wire wound about the post to form a winding, with the winding having at least one end turn. Aspects of the disclosure shown include at least one set of main machine stator windings <NUM> arranged longitudinally along the housing <NUM>, that is, in parallel with housing <NUM> and the rotational axis <NUM>. The set of stator windings <NUM> can also include a set of stator winding end turns <NUM> extending axially beyond opposing ends of a longitudinal length of a main machine stator <NUM>.

The components of the generator <NUM> can be any combination of known generators. For example, the main machine <NUM> can be either a synchronous or asynchronous generator. In addition to the accessories shown in this aspect, there can be other components that need to be operated for particular applications. For example, in addition to the electromechanical accessories shown, there can be other accessories driven from the same rotatable shaft <NUM> such as the liquid coolant pump, a fluid compressor, or a hydraulic pump.

As explained above, the generator <NUM> can be oil cooled and thus can include a cooling system <NUM>. The cooling oil can be used to dissipate heat generated by the electrical and mechanical functions of the generator <NUM>. The cooling system <NUM> using oil can also provide for lubrication of the generator <NUM>. In the illustrated aspects, the generator <NUM> can be a liquid cooled, wet cavity cooling system <NUM> including the cooling fluid inlet port <NUM> and the cooling fluid outlet port <NUM> for controlling the supply of the cooling fluid to the cooling system <NUM>. The cooling system <NUM> can further include, for example, a cooling fluid reservoir <NUM> and various cooling passages. The rotatable shaft <NUM> can provide one or more channels or paths for coolant or fluid coolant flow <NUM> (shown schematically as arrows) for the main machine rotor <NUM>, exciter rotor <NUM>, and PMG rotor <NUM>, as well as an rotor shaft cooling fluid outlet <NUM>, such as the second coolant outlet port <NUM>, wherein residual, unused, or unspent oil can be discharged from the rotatable shaft <NUM>.

In non-limiting examples of the generator <NUM>, the fluid coolant flow <NUM> can further be directed, exposed, sprayed, or otherwise deposited onto the set of main machine stator windings <NUM>, the set of stator winding end turns <NUM>, or onto alternative or additional components. In this example, the fluid coolant flow <NUM> can flow from the rotatable shaft <NUM> radially outward toward the set of stator windings <NUM> or the set of stator winding end turns <NUM>. In this sense, the coolant can cool the respective set of stator windings <NUM> or set of stator winding end turns <NUM>.

<FIG> illustrates an isometric view of the exciter rotor <NUM> or exciter rotor assembly. As shown, the exciter rotor <NUM> can include a circumferentially extending exciter rotor core <NUM>, such as a laminated rotor core, defining an axial passage encircling the rotatable shaft <NUM> and rotatably connected to co-rotate with the rotatable shaft <NUM>. The exciter rotor core <NUM> includes a set of circumferentially-spaced, axially-extending exciter posts <NUM> or teeth defining slots between adjacent posts <NUM>. The exciter rotor <NUM> can include at least one rotor pole <NUM> defined by a respective rotor post <NUM> and formed when at least a portion of the rotor core <NUM> is wound with a conductive rotor conductor, wire, or windings, about the rotor post <NUM>. As shown schematically, a set of exciter rotor windings <NUM> are wound about the set of rotor posts <NUM> (e.g. in the slots between adjacent posts <NUM>) to define a set of rotor poles <NUM>. In this sense, a winding <NUM> is carried by each of the posts <NUM> and comprising an electrically-conductive wire repeatedly wound around the post <NUM> such that a portion of the winding extends axially beyond the post <NUM> to define an overhang with upper and lower surfaces connected by an end (e.g. an "end turn").

At each opposing axial end of the of the exciter rotor <NUM>, the set of exciter rotor windings <NUM> can be at least partially supported or contained by an end cap <NUM>. In this sense, the set of exciter rotor windings <NUM>, or portions thereof is differential in both side and requires balanced support structure to contain winding <NUM> movement radially outward and inward. As shown in for the foreground in the perspective of <FIG>, a first axial end <NUM> of the exciter rotor <NUM> includes a first end cap <NUM>, while a second axial end <NUM> at opposing end of the exciter rotor <NUM> can include a second end cap <NUM>. Non-limiting aspects of the first and second end caps <NUM>, <NUM> can be substantially similar or different depending on the needs of the exciter rotor <NUM>. While further discussion of the first and second end caps <NUM>, <NUM> will be primarily directed toward the example of the first end cap <NUM>, aspects of the disclosure can be applicable to the second end cap <NUM>, as well.

The first end cap <NUM> can include a set of apertures or openings allowing or providing access to the underlying set of exciter rotor windings <NUM>. As shown, aspects of the disclosure can include a set of axial-facing coolant openings <NUM> or slots. The first end cap includes a set of first radially-inward facing coolant openings <NUM> or slots. Also as illustrated, the rotatable shaft <NUM> includes a radially-extending set of shaft openings <NUM> allowing access to an inner cavity <NUM> of the rotatable shaft <NUM>, such as the cavity <NUM>, defining a coolant passage having the fluid coolant flow <NUM> (not shown). In this sense, the set of shaft openings <NUM> can extend from an inner surface of the rotatable shaft <NUM> to an outer surface of the rotatable shaft <NUM>. While four circumferentially spaced shaft openings <NUM> are shown, any number of shaft openings <NUM> can be included. Additionally, the set of shaft openings <NUM> can be circumferentially arranged to align with the set of first coolant openings <NUM>.

By way of non-limiting example, the end cap <NUM> can be fixed to the rotatable shaft <NUM> using one or more bolts, screws, pins, or other known fasteners. It is also contemplated that the end cap <NUM> and the rotatable shaft <NUM> can be fixed by any affixing mechanisms.

<FIG> illustrates a cross-sectional view of the exciter <NUM>, including the exciter rotor <NUM> and the exciter stator <NUM>. The set of exciter rotor windings <NUM> wound around the rotor post <NUM> defines rotor winding end turns <NUM> extending axially beyond the rotor core <NUM> or rotor post <NUM>. In one non-limiting example, the rotor winding end turns <NUM> can be at least partially axially spaced from the rotor post <NUM>, defining a gap <NUM> or radially-extending opening. The gap <NUM> can further define a second coolant opening <NUM> or slots (or a set thereof). Stated another way, the outer wall of the end cap <NUM> can terminate short of the rotor core <NUM> to define at least one of the gap <NUM> or the set of second coolant openings <NUM>. In another non-limiting example, the gap <NUM> can be defined by tubes, cuts, or another structural element about which the set of exciter rotor windings <NUM> are wound. The exciter rotor <NUM> can also be configured to define a set of second outwardly-facing coolant openings <NUM> at a radially outward wall of the end cap <NUM>. As shown, the exciter rotor <NUM> can be arranged or aligned with at least a subset of the shaft openings <NUM>, at least a subset of the first coolant openings <NUM> of the end cap <NUM>, the gap <NUM>, the set of second coolant openings <NUM>, or a combination thereof, define a continuous or contiguous radial opening or passageway fluidly coupled to one another and the set of exciter rotor windings <NUM> and the rotor winding end turns <NUM>.

Generally, the end cap <NUM> includes a collar circumscribing the outer surface of the rotatable shaft <NUM> and a C-shaped wall, set of walls, channel, or the like, supported by the collar and that axially envelop, contain, retain, or otherwise cradle the rotor winding end turns <NUM>. In this sense, the end cap <NUM> can support the rotor winding end turns <NUM>.

<FIG> further illustrates a schematic representation of the exciter stator <NUM>, having at least an exciter stator core <NUM> and a set of exciter stator windings <NUM>. As shown, the exciter stator core <NUM> is radially spaced from and generally sized to match the exciter rotor core <NUM>, and the set of exciter stator windings <NUM> extend axially along and beyond the exciter stator core <NUM>, and are radially spaced from and generally sized to match the set of exciter rotor windings <NUM>. In one non-limiting example, at least a portion of the set of exciter stator windings <NUM> can be radially aligned with the set of second coolant openings <NUM>.

<FIG> illustrates a schematic zoomed view of the exciter rotor <NUM> wherein coolant traverses a set of passages. As shown, a first interface <NUM> is between an upper surface of the overhanging rotor winding end turns <NUM> and an under or lower surface of the end cap <NUM>. Similarly, a second interface <NUM> is between an axial surface of the overhanging rotor winding end turns <NUM> and an axial surface of the end cap <NUM>. Finally, a third interface <NUM> is between an under or lower surface of the overhanging rotor winding end turns <NUM> and an upper surface of the end cap <NUM>. In this sense, the end cap <NUM> is configured or adapted to support the lower surface of the overhang, and can be configured or adapted to support at least one of the upper or axial surfaces of the overhanging rotor winding end turns <NUM>, or a combination thereof. As used herein, under, lower, axial, upper, and like denotes a radially relative position between respective elements.

During operation, the cooling system <NUM> flows the fluid coolant flow <NUM> (schematically shown as arrows) through at least a portion of the exciter rotor <NUM>. As shown, fluid coolant flow <NUM> received in the cavity <NUM> of the rotatable shaft <NUM> can traverse radially outward through the set of shaft openings <NUM>. The direction or location of the fluid coolant flow <NUM>, including a source of coolant (not shown) is not limited by the illustration and can be considered in any location that is fluidly coupled to the cavity <NUM> of the rotatable shaft <NUM>. It is further considered that additional conduit, pumps, valves, or other devices can be included to fluidly connect the fluid coolant flow <NUM> to the rotatable shaft.

The fluid coolant flow <NUM> is expelled radially outward from the set of shaft openings <NUM> toward the overlying set of first coolant openings <NUM>. The set of first coolant openings <NUM> fluidly receives the fluid coolant flow <NUM>, and further directs the fluid coolant flow <NUM> toward the set of exciter rotor windings <NUM> and rotor winding end turns <NUM>. Non-limiting aspects of the disclosure can be included wherein surfaces, walls, or the like can be configured or adapted at the set of shaft openings <NUM>, the set of first coolant openings <NUM>, or the like, to ensure the expected directing of the fluid coolant flow <NUM> toward the set of exciter rotor windings <NUM> and rotor winding end turns <NUM>. In this sense, the set of first coolant openings <NUM> can be configured to overlie the fluid output volume from the set of shaft openings <NUM>, such that fluid expelled from the set of shaft openings <NUM> is received by set of first coolant openings <NUM> reliably. At least a portion of the fluid coolant flow <NUM> can be received in the gap <NUM> and can further flow radially outward past at least a portion of the set of rotor windings <NUM>, past at least a portion of the rotor core <NUM>, or a combination thereof.

In another non-limiting aspect of the disclosure, the fluid coolant flow <NUM> can be received by the set of second coolant openings <NUM>, and expelled radially outward beyond the exciter rotor <NUM>. In one example, the fluid coolant flow <NUM> can be expelled outward toward the set of stator windings <NUM>, shown schematically in boxed form. In yet another non-limiting aspect of the disclosure an axially-outer-facing wall <NUM> of the rotor core <NUM> or rotor post <NUM> can be adapted or configured to include a surface to direct or redirect the fluid coolant flow <NUM> as desired, to ensure or allow for proper flow toward the set of rotor windings <NUM> or set of rotor winding end turns <NUM>, or toward the set of second coolant openings <NUM>. Similarly, non-limiting aspects of the set of second coolant openings <NUM> can include a set of shaped walls, surfaces, nozzles, or the like, such that the fluid coolant flow <NUM> is directed or redirected, as needed, toward the set of stator windings <NUM>.

As further shown, non-limiting aspects of the disclosure can be included wherein another portion of the fluid coolant flow <NUM> can flow through the rotor winding end turns <NUM> toward, and be axially expelled from, the set of axial coolant openings <NUM>.

Thus, non-limiting aspects of the disclosure enable or allow for a fluid delivery passageway. Fluid can enter the rotatable shaft <NUM> via the inlet port <NUM>. The rotatable shaft <NUM> at least in part, can define the cavity <NUM>, from which fluid can flow radially outward relative to the rotational axis <NUM>. The fluid coolant supplied from the cavity <NUM> of the rotatable shaft <NUM> is fluidly delivered through the set of shaft openings <NUM>, into the set of first coolant openings <NUM>, along the gap <NUM> between the rotor core <NUM> and the rotor winding end turns <NUM>, and out of the set of second coolant openings <NUM>, optionally toward the set of stator windings <NUM>. It is contemplated that the fluid can be, but is not limited to, coolant.

During operation of the generator <NUM>, the magnetic field generated by the set of exciter stator windings <NUM> relative to the rotating set of exciter rotor windings <NUM> induces current in the set of exciter rotor windings <NUM>. This magnetic interaction further generates heat in at least one of set of exciter rotor windings <NUM> and exciter stator windings <NUM>. In accordance with aspects described herein, the fluid coolant flow <NUM> can be delivered from the rotatable shaft <NUM> through the set of shaft openings <NUM>, into the set of first coolant openings <NUM> and past at least one of the rotor core <NUM>, the set of exciter rotor windings <NUM>, the rotor winding end turns <NUM>, or a combination thereof. The fluid coolant flow <NUM> past the at least one of the rotor core <NUM>, the set of exciter rotor windings <NUM>, the rotor winding end turns <NUM>, or a combination thereof transfers heat from the rotor core <NUM>, the set of exciter rotor windings <NUM>, or the rotor winding end turns <NUM> into the coolant by conduction. The coolant is radially expelled from set of second coolant openings <NUM>, and optionally further radially expelled outward to contact the set of exciter stator windings <NUM>. This contacting further removes heat from the exciter stator windings <NUM> into the coolant.

<FIG> illustrates another end cap <NUM> according to another aspect of the present disclosure. The end cap <NUM> is similar to the end cap <NUM>; therefore, like parts will be identified with like numerals increased to <NUM>-series numbers, with it being understood that the description of the like parts of the end cap <NUM> applies to the end cap <NUM>, unless otherwise noted. One difference is that the radially-outward surface <NUM> of the end cap <NUM> can define the set of second coolant openings <NUM>, compared with the set of second openings <NUM> defined between the end cap <NUM> and the rotor core <NUM>. As shown, the end cap <NUM> also includes a set of axial openings <NUM> on an axially-outward surface <NUM> and a set of first coolant openings <NUM> at the radially-inward surface <NUM>. Non-limiting aspects of the disclosure can be included wherein the set of first coolant openings <NUM> can further include surfaces adapted or configured to include a surface to direct or redirect the fluid coolant flow <NUM> as desired, to ensure or allow for proper flow toward the set of first coolant openings <NUM>, the set of rotor windings <NUM>, set of rotor winding end turns <NUM>, or the like.

<FIG> illustrates another end cap <NUM> according to another aspect of the present disclosure. The end cap <NUM> is similar to the end caps <NUM>, <NUM>; therefore, like parts will be identified with like numerals increased to <NUM>-series numbers, with it being understood that the description of the like parts of the end cap <NUM>, <NUM> applies to the end cap <NUM>, unless otherwise noted. One difference is that the radially-outward surface <NUM> of the end cap <NUM> can define a set of axially extending teeth <NUM>, between which define the set of second coolant openings <NUM>. As show, the end cap <NUM> also includes a set of axial openings <NUM> on an axially-outward surface <NUM> and a set of first coolant openings <NUM> at the radially-inward surface <NUM>. Additionally aspects of the disclosure, including but not limited to the set of axially extending teeth <NUM>, the set of second coolant openings <NUM>, the set of axial openings <NUM>, the set of first coolant openings <NUM>, or a combination thereof, can extend circumferentially along any portion of the end cap <NUM>.

Many other possible aspects and configurations in addition to that shown in the above figures are contemplated by the present disclosure. For example, one aspect of the disclosure contemplates coolant passageway that extend along alternative portions or lengths of the exciter rotor <NUM>. In another example, the windings or the coolant passageway can further include intervening thermally conductive layers to assist in thermal conduction while, for example, avoiding an electrically conductive relationship between respective components. Additionally, the design and placement of the various components such as valves, pumps, or conduits can be rearranged such that a number of different in-line configurations could be realized.

The aspects disclosed herein provide method and apparatus for cooling a set of exciter rotor windings or a set of rotor winding end turns during electric machine operations (e.g. motor or generator operations). One advantage that may be realized in the above aspects is that the above described aspects have significantly improved thermal conduction to remove heat from the set of exciter rotor windings or the set of rotor winding end turns. The improved thermal conductivity between the set of exciter rotor winding end turns and the coolant conduits coupled with the coolant channels provide for heat removal in a much more effective fashion from the rotor winding end turns to the coolant. Furthermore, the improved cooling of the set of exciter rotor windings further prevents issues associated with overheating windings, including but not limited to, insulation failure issues, mechanical failure of top containment band, arrested axial movement of containment band, and the like.

The increased thermal dissipation of the rotor winding end turns allows for a higher speed rotation, which may otherwise generate too much heat. The higher speed rotation may result in improved power generation or improved generator efficiency without increasing generator size. The described aspects having the fluid channels for the wet cavity machine are also capable of cooling the exciter stator windings or end turn segments which further reduces thermal losses of the electric machine. Reduced thermal losses in the electric machine allows for greater efficiency and greater power density of the generator.

When designing aircraft components, reliability is also informant feature. The above described end assembly can provide additional physics stability and improved cooling to the rotor end windings. The stability and cooling provided by the end support allow an increase in performance and reliability.

To the extent not already described, the different features and structures of the various aspects can be used in combination with each other as desired. That one feature cannot be illustrated in all of the aspects is not meant to be construed that it cannot be, but is done for brevity of description. Thus, the various features of the different aspects can be mixed and matched as desired to form new aspects, whether or not the new aspects are expressly described. Combinations or permutations of features described herein are covered by this disclosure.

Claim 1:
A rotor (<NUM>) for an electric machine comprising:
a core (<NUM>) having circumferentially-spaced, axially-extending posts (<NUM>), and defining an axial passage;
a winding (<NUM>) carried by each of the posts (<NUM>) and comprising an electrically-conductive wire repeatedly wound around the post (<NUM>) such that a portion of the winding (<NUM>) extends axially beyond the post (<NUM>) to define an overhang with upper and lower surfaces connected by an end; and
a shaft (<NUM>) located within the axial passage, wherein the shaft (<NUM>) is hollow, defining an inner surface and an outer surface, and has a coolant passage (<NUM>) radially extending between the inner and outer surfaces, arranged such that during operation coolant is expellable radially outward from the coolant passage (<NUM>);
wherein the rotor (<NUM>) comprises:
an end cap (<NUM>, <NUM>, <NUM>) comprising a collar circumscribing the outer surface of the shaft and a C-shaped wall supported by the collar, wherein the C-shaped wall axially cradles the winding end turns and supports the lower surface of the overhang, the end cap (<NUM>, <NUM>, <NUM>) having a first radially inward facing coolant opening (<NUM>, <NUM>, <NUM>) on a radially inward surface of the end cap (<NUM>, <NUM>, <NUM>), the first radially inward facing coolant opening (<NUM>, <NUM>, <NUM>) being fluidly coupled to the overhang lower surface; and wherein
the coolant passage (<NUM>) is fluidly coupled to the first radially inward facing coolant opening (<NUM>, <NUM>, <NUM>).