Patent Description:
Electrical machines commonly include electrically conductive windings supported by core. In motors electrical current is generally applied to the windings to generate magnetic flux, which interacts with a rotor supported for rotation relative to the core to exert torque on the rotor. In generators rotation of a rotor with magnetic elements supported for rotation relative to the core induces current flow within the windings, which is communicated as electric power. In each case, the electrical current flowing through the windings generates heat due to electromagnetic losses in both the windings and the core. The heat is typically rejected to the external environment through the electrical machine frame, which is generally provided with fins that define channels therebetween. The fins increase the surface area of the frame, increasing heat rejection during operation of the electrical machine.

In some electrical machines a liquid coolant is used for removing heat from the electrical machine, generally though a jacket with coolant channels that is attached to the core using a shrink fit process. The coolant channels are typically cut into the jacket using a subtractive technique and enclosed within a sufficient amount of jacket material to withstand the hoop stress associated with the shrink fit process. Alternatively, a coolant conduit can be wrapped about the core to conduct heat from the core into a coolant traversing the conduit. In both arrangements heat conducted from the core traverses an interface defined between the conduit and the core.

Such systems and methods have generally been satisfactory for their intended purposes. However, there remains a need for improved electrical machines and methods of making electrical machines. The present disclosure provides a solution to this need. <CIT> describes a rotary electric machine. <CIT> describes a dynamoelectric machine including a stator heat transfer feature.

A stator is described herein and defined in claim <NUM>.

In addition to one or more of the features described above, further embodiments may include that a first layer of the plurality of layers comprises a fused metallic particulate and a second layer of the plurality of layers comprises a fused metallic particulate, the second layer being fused to the first layer.

In addition to one or more of the features described above, further embodiments may include that the two or more layers bound the coolant channel.

In addition to one or more of the features described above, further embodiments may include that one or more of the plurality of layers is arranged radially between the coolant channel and the outer surface of the core.

In addition to one or more of the features described above, further embodiments may include that the outer surface of the core bounds the coolant channel.

In addition to one or more of the features described above, further embodiments may include that the coolant channel extends helically about the rotation axis.

In addition to one or more of the features described above, further embodiments may include that the coolant channel has a first flow area and a second flow area, the first flow area being larger in size than the second flow area.

In addition to one or more of the features described above, further embodiments may include that the core has a first end portion, an axially opposite second end portion, and an intermediate portion coupling the first end portion to the second end portion, the first flow area being defined along in the intermediate portion of the core and the second flow area being defined along the first end portion or the second end portion of the core.

In addition to one or more of the features described above, further embodiments may include that the coolant channel tapers in flow area size between the first flow area and the second flow area along a length of the coolant channel.

In addition to one or more of the features described above, further embodiments may include a heat transfer structure arranged within the coolant channel, the heat transfer structure being selected from a group including a turbulator, a riblet, and a spire.

In addition to one or more of the features described above, further embodiments may include that the heat transfer structure is formed from a fused particulate and is spaced apart from the coolant jacket by a portion of the outer surface of the core.

In addition to one or more of the features described above, further embodiments may include that the first layer has a radial thickness that is smaller than a radial thickness of the second layer.

In addition to one or more of the features described above, further embodiments may include a liquid coolant disposed within the coolant channel, a winding extending about the rotation axis and arranged radially inward of the outer surface of the core, and a rotor arranged radially inward of the core and supported for rotation about the rotation axis.

In another embodiment an electrical machine is provided. The electrical machine includes a stator as described above, wherein a first layer of the plurality of layers comprises a fused metallic particulate, wherein a second layer of the plurality of layers comprises a fused metallic particulate, wherein the second layer is fused to the first layer, wherein the core comprises a steel material, wherein the coolant jacket comprises a metallic material. A rotor is arranged radially inward of the core and supported for rotation about the rotation axis.

In addition to one or more of the features described above, further embodiments may include that the coolant channel has a first flow area and a second flow area, the first flow area greater than the second flow area, the core further comprising a heat transfer structure arranged within the coolant channel.

In addition to one or more of the features described above, further embodiments may include a motor-type electrical machine having a stator as described above.

According to a second aspect, a method of making a stator is described herein and defined by claim <NUM>.

Technical effects of the present disclosure include limiting (or eliminating entirely) thermal resistance between the electrical machine frame and the coolant jacket. In certain embodiments the present disclosure provides the capability to orient the coolant channels of the coolant jacket to heat communication characteristics of the electrical machine. In accordance with certain embodiments the diameter of the electrical machine and/or the weight of the coolant jacket is relatively low due to the core of the electrical machine bounding one or more of the coolant channels defined by the coolant jacket.

Reference will now be made to the drawings wherein like reference numerals identify similar structural features or aspects of the subject disclosure. For purposes of explanation and illustration, and not limitation, a partial view of an exemplary embodiment of a stator for an electrical machine in accordance with the disclosure is shown in <FIG> and is designated generally by reference character <NUM>. Other embodiments of stators, electrical machines, motor-type electrical machines, and methods of making stators in accordance with the present disclosure are shown in <FIG>, as will be described. The systems and methods described herein can be used for liquid-cooled electrical machines, such as motor-type electrical machines in aircraft electrical systems, though the present disclosure not limited motor-type electrical machines or to aircraft electrical systems in general.

In addition to the stator <NUM>, a rotor <NUM> is illustrated in <FIG>. When combined, the stator <NUM> and the rotor <NUM> form portions of an electrical machine <NUM>, such as a motor-type electrical machine. The rotor <NUM> is supported for rotation about a rotation axis <NUM> and includes a plurality of sheets <NUM> and one or more magnetic elements <NUM>. The plurality of sheets <NUM> are axially stacked along the rotation axis <NUM> and are formed from a magnetic steel material <NUM>. The one or more magnetic elements <NUM> may be fixed to the rotor <NUM> such that they rotate with the rotor <NUM> about the rotation axis <NUM>. It is contemplated that the one or more magnetic elements <NUM> can be a permanent magnet and/or a coil, as suitable for an intended application.

The stator <NUM> includes a core <NUM>, a winding <NUM> (shown in <FIG>), and a coolant jacket <NUM>. The winding <NUM> is supported within core <NUM> at a radially inner location. The core <NUM> extends circumferentially about the rotation axis <NUM> and has a first end portion <NUM>, a second end portion <NUM>, and an intermediate portion <NUM>. The second end portion <NUM> is arranged on an end of the core <NUM> axially opposite the first end portion <NUM>. The intermediate portion <NUM> of the core <NUM> couples the first end portion <NUM> of the core <NUM> to the second end portion <NUM> of the core <NUM>. It is contemplated that the core <NUM> include a plurality of sheets <NUM> laminated to one another and axially stacked along the rotation axis <NUM>. It is contemplated that the core <NUM> be formed by a steel material <NUM>, such as electric steel by way of non-limiting example. Although described herein as having a laminated core construction, it is also contemplated that cores with other structures can also benefit from the present disclosure, such as forged and sintered powder metal cores by way of non-limiting example.

The coolant jacket <NUM> is deposited on an outer surface <NUM> of the core <NUM>. More specifically, the coolant jacket <NUM> has a first layer <NUM> (shown in <FIG>) and one or more second layer <NUM> (shown in <FIG>) conformally disposed on the outer surface <NUM> of the core <NUM>, the coolant jacket <NUM> inhabiting the one or more surface discontinuity <NUM> defined within the outer surface <NUM> of the core <NUM>. As used herein the term "inhabit" refers to volumetrically occupied space defined by the surface discontinuity, and in proximity thereof, that would be occupied at least in part by air if a coolant jacket were attached to the core <NUM> using a shrink-fit process.

With reference to <FIG>, a portion of the stator <NUM> is shown. The core <NUM> is radially bounded by the outer surface <NUM> and two or more stator teeth <NUM>. The two or more stator teeth <NUM> are arranged radially inward of the outer surface <NUM>. Coils of the winding <NUM> are wrapped about the respective stator teeth <NUM> and are connected electrically with one another in series (or parallel) to communicate magnetic flux to the rotor <NUM> (shown in <FIG>). As will be appreciated by those of skill in the art in view of the present disclosure, application of electric current to the winding <NUM> generates heat H - both from resistive heating of the conductors forming the winding <NUM> and from magnetic flux generated by the current flow or magnetic elements carried by the rotor (e.g., permanent magnets and/or windings) - which is rejected to the environment external to the stator <NUM>.

The coolant jacket <NUM> includes a plurality of layers, e.g., the first layer <NUM> and the one or more second layer <NUM>, and is arranged to communicate the heat H to the external environment. In this respect the coolant jacket <NUM> defines at least partially a plurality of coolant channels <NUM> within the coolant jacket <NUM>. A liquid coolant <NUM> may be provided to the coolant channels <NUM> to receive the heat H. The liquid coolant <NUM> traverses the coolant channels <NUM>, receives the heat H from the core <NUM>, and carries the heat H therewith for communication to the external environment. Examples of suitable liquid coolants include water, water-glycol, refrigerants, liquid metal, oil, brine, glycol-containing mixtures, and kerosene-based fuels.

The first layer <NUM> includes a fused metallic particulate <NUM> distributed radially outward of the core <NUM>. The one or more second layer <NUM> includes an fused metallic particulate <NUM>, also distributed radially outward of the core <NUM>, and is additionally fused with the underlying first layer <NUM> to form a monolithic and unitary stator <NUM>. It is contemplated that either (or both) the fused metallic particulate <NUM> and the fused metallic particulate <NUM> include a metallic material <NUM>, for aluminum or titanium and/or alloys thereof. In certain embodiments metallic material <NUM> is selected to additionally limit, e.g., through the use of aluminum or an aluminum alloy, the weight of the coolant jacket <NUM> while providing good thermal communication through the coolant jacket <NUM>.

The first layer <NUM> and the one or more second layers <NUM> are conformally disposed to the outer surface <NUM> of the core <NUM>. More specifically, the first layer <NUM> and the one or more second layer <NUM> are deposited to the core <NUM> and bound, at least partially, the coolant channels <NUM>. As shown in <FIG> the first layer <NUM> is deposited on the outer surface <NUM> of the core <NUM> and circumferentially about the core <NUM>, and the one or more second layer <NUM> is deposited on the first layer <NUM> and circumferentially about the outer surface <NUM> of the core <NUM> at a location radially outward of the first layer <NUM>. Although shown an described in a specific orientation, e.g., circumferentially about one another and the core <NUM>, other orientations of the first layer <NUM> and one the second layer <NUM> are possible within the scope of the present disclosure.

It is contemplated that the first layer <NUM> and one or more second layers <NUM> be deposited using an additive manufacturing technique. Examples of suitable additive manufacturing techniques include cold spray techniques, wire addition techniques, and powder bed fusion techniques by way of non-limiting examples. Deposition of the first layer <NUM> and the one or more second layer <NUM> reduces the thermal resistance at an interface <NUM> defined between the coolant jacket <NUM> and the core <NUM> relative to shrink-fit cores having coolant channel formed using a subtractive process of similar geometry.

In certain embodiments the thermal resistance presented by the interface <NUM> can be on the order of about <NUM>% less than that presented by a coolant jacket applied by a shrink fit process, which is unexpectedly better than expected. Without wishing to be bound by a particular theory, applicants believe that this unexpected improvement in thermal resistance is attributable to the tendency of deposited materials to displace gas resident in micro-features, e.g., the surface discontinuity <NUM>, defined on the outer surface <NUM> of the core <NUM> resultant from the manufacturing process, e.g., the stamping process used to from the plurality of sheets <NUM>, rather than impound the gases between a coolant jacket and the core <NUM> as can occur when a discrete coolant jacket structure is assembled to the core <NUM> using a shrink-fit technique.

With continuing reference to <FIG>, it is contemplated that the first layer <NUM> and the one or more second layer <NUM> define an inlet manifold <NUM> and or an outlet manifold <NUM>. The inlet manifold <NUM> and/or the outlet manifold <NUM> in turn fluidly connect the coolant channels <NUM> to a singular coolant inlet and/or coolant outlet. Forming the inlet manifold <NUM> and/or the outlet manifold <NUM> can simplify the assembly of the stator <NUM> as there is no need to attach a coolant manifold as discrete structure. Forming the inlet manifold <NUM> and/or the outlet manifold <NUM> can also improve the reliability of electrical machines employing the stator <NUM>, e.g., the electrical machine <NUM> (shown in <FIG>), as fewer coolant conduit connections need to be made during assembly - each of which can present a risk of coolant leakage.

With reference to <FIG>, embodiments of the stator <NUM> are shown. As shown in <FIG>, in certain embodiments the coolant jacket <NUM> can define a coolant channel <NUM> having a heat transfer feature <NUM>. In this respect the coolant channel <NUM> is similar to the coolant channel <NUM> (shown in <FIG>) and additionally includes the heat transfer structure <NUM>. The heat transfer structure <NUM> is defined within the coolant channel <NUM> and is formed using an additive manufacturing technique, e.g., the additive manufacturing technique used to form the first layer <NUM> and/or the second layer <NUM>. During service the heat transfer surface <NUM> increases the surface area otherwise presented by the coolant jacket <NUM> to the liquid coolant <NUM> traversing the coolant channel <NUM>. The increased surface area provided by the heat transfer feature <NUM> increases the rate of heat transfer between the coolant jacket <NUM> and the liquid coolant <NUM>, increasing the rate of heat rejection from the core <NUM> to the liquid coolant <NUM> - allowing for increased rating of the electrical machine <NUM>.

As shown in <FIG>, it is contemplated that the coolant jacket <NUM> and the core <NUM> can collectively define a coolant channel <NUM>. The coolant channel <NUM> is similar to the coolant channel <NUM> (shown in <FIG>) and additionally includes a heat transfer structure <NUM>. The heat transfer structure <NUM> is defined radially on (and within) the outer surface <NUM> of the core <NUM>. The heat transfer feature <NUM> is defined using a subtractive manufacturing technique, such as a milling or stamping technique, increasing the surface area presented by the core <NUM> to the liquid coolant <NUM> traversing the coolant channel <NUM>. The increased surface area provided by the heat transfer feature <NUM> increases the rate of heat transfer between the core <NUM> and the liquid coolant <NUM>, increasing the rate of heat rejection from the core <NUM> to the liquid coolant <NUM> traversing the coolant channel <NUM> during operation of the electrical machine <NUM>.

As shown in <FIG>, it is also contemplated that, in accordance with in certain embodiments, the coolant jacket <NUM> can define a coolant channel <NUM> with a thin coolant jacket layer separating the coolant channel <NUM> from the core <NUM>. In this respect the coolant channel <NUM> is similar to the coolant channel <NUM> (shown in <FIG>) and additionally includes a thin first layer <NUM>. The thin first layer <NUM> has a radial thickness <NUM> that is smaller than a radial thickness <NUM> of the one or more second layers <NUM>. The thin first layer <NUM> allows the coolant jacket <NUM> to be relatively lightweight relative to a coolant jacket fit assembles to the core <NUM> using a shrink-fit technique and still provide a fluid-tight seal between the coolant channel <NUM> and the core <NUM>. This prevents infiltration of the liquid coolant <NUM> into the core <NUM> via leak paths that may be present between the laminations, e.g., the laminations <NUM> (shown in <FIG>), forming the core <NUM>.

As shown in <FIG>, in further embodiments the coolant jacket <NUM> can define one or more coolant channel <NUM> bounded by the outer surface <NUM> of the core <NUM>. In this respect the coolant channel <NUM> is similar to the coolant channel <NUM> (shown in <FIG>) and is additionally bounded by a portion of the outer surface <NUM> of the core <NUM>. Bounding a portion of the outer surface <NUM> of the core <NUM>, the liquid coolant <NUM> flowing through the coolant channel <NUM> flows directly across the outer surface <NUM> of the core <NUM>. This eliminates entirely the thermal resistance associated with the interface that would otherwise be present between a coolant jacket assembled to the core <NUM> using a shrink fit technique and the core <NUM>, increasing the rate of heat transfer from the core <NUM> into the liquid coolant <NUM> within the coolant channel <NUM>. It can also limits the radial thickness of the coolant jacket <NUM>, limiting weight of the stator <NUM>.

With reference to <FIG>, the heat transfer structures <NUM> and the heat transfer structure <NUM> are shown. As shown in <FIG>, the heat transfer structure <NUM> and/or the heat transfer structure <NUM> can include one or more turbulator <NUM>. The one or more turbulator <NUM> is arranged transversely with respect to flow of the liquid coolant <NUM> through the coolant channel <NUM> (shown inn <FIG>) and/or the coolant channel <NUM> (shown in <FIG>). In certain embodiments the one or more turbulator <NUM> can be an artifact, e.g., unintentional consequence of tool wear, from the stamping process used to for the sheets <NUM> (shown in <FIG>) forming the core <NUM> (shown in <FIG>). In accordance with certain embodiments the one or more turbulator <NUM> can formed using the additive manufacturing technique used to conformally dispose the first layer <NUM> (shown in <FIG>) and/or the one or more second layer <NUM> (shown in <FIG>) on the outer surface <NUM> of the core <NUM>. As will be appreciated by those of skill in the art in view of the present disclosure, the transverse orientation of the one or more turbulator <NUM> relative to the direction of the flow of the liquid coolant <NUM> through the coolant channel <NUM> and/or the coolant channel <NUM> introduces turbulence within the flow of the liquid coolant <NUM>, promoting fluid mixing and increasing the rate of heat transfer between the stator <NUM> (shown in <FIG>) and the liquid coolant <NUM>.

As shown in <FIG>, the heat transfer structure <NUM> and/or the heat transfer structure <NUM> can include one or more riblet or fin <NUM>. The one or more riblet of fin <NUM> is arranged along the direction of flow of the liquid coolant <NUM>, increasing the surface area of the coolant jacket <NUM> (shown in <FIG>) or the core <NUM> (shown in <FIG>) that the liquid coolant <NUM> contacts while traversing the stator <NUM> (shown in <FIG>). This increases the rate of heat transfer between the coolant jacket <NUM> or the core <NUM> and the liquid coolant <NUM>. It is contemplated that the one or more riblet or fin <NUM> can be axially discontinuous and circumferentially displaced within the coolant channel relative to another riblet or fin <NUM>.

As shown in <FIG>, the heat transfer structure <NUM> and/or the heat transfer structure <NUM> can include one or more spire <NUM>. The one or more spire <NUM> protrude radially into the liquid coolant <NUM>, increasing the surface area of the coolant jacket <NUM> (shown in <FIG>) or the core <NUM> (shown in <FIG>) that the liquid coolant <NUM> contacts while traversing the stator <NUM> (shown in <FIG>), the one or more spire <NUM> increasing increase the rate of heat transfer between the coolant jacket <NUM> or the core <NUM> and the liquid coolant <NUM>.

With reference to <FIG>, a stator <NUM> is shown. The stator <NUM> is similar to the stator <NUM> (shown in <FIG>) and additionally includes a coolant jacket <NUM>. The coolant jacket <NUM> defines at least partially a coolant channel <NUM>. The coolant channel <NUM> extends helically about the rotation axis <NUM>. More specifically, the coolant jacket <NUM> defines a plurality of coolant channels <NUM> extending helically about the rotation axis <NUM> spanning at least an intermediate portion <NUM> of the core <NUM>. The helical path increases the length of the coolant channel <NUM> with respect to the axial length of core <NUM>, increasing the amount of heat communicated to the liquid coolant <NUM> (shown in <FIG>) as the liquid coolant traverses the coolant channel <NUM>. As shown in <FIG> the helical path of the coolant channel <NUM> span the first end portion <NUM>, the intermediate portion <NUM>, and the second end portion <NUM> of the core <NUM>.

With reference to <FIG>, a stator <NUM> is shown. The stator <NUM> is similar to the stator <NUM> and additionally has a coolant jacket <NUM>. The coolant jacket <NUM> defines at least partially a coolant channel <NUM>. The coolant channel <NUM> has a first flow area <NUM> and a second flow area <NUM>. The first flow area <NUM> is greater than the second flow area <NUM>. It is contemplated that the first flow area be defined by the coolant channel <NUM> at an axial location radially adj acent to an end turn <NUM> of a winding <NUM>, e.g., radially adjacent to the first end portion <NUM> and/or the second end portion <NUM>, and that the second flow area <NUM> be defined along the intermediate portion <NUM> of the core <NUM>. Defining the first flow area <NUM> radially adjacent to the end turn <NUM> increases residency time of the liquid coolant <NUM> (shown in <FIG>) at locations radially adjacent to the end turn <NUM>, increasing the amount of heat removed from the end turn <NUM>. As the end turn <NUM> of a winding can run hotter than the portion of the winding spanning the intermediate portion <NUM> of the core <NUM>, the greater size of the first area <NUM> reduces the total range of temperature along the core <NUM> during operation electrical machines employing the stator <NUM>.

With reference to <FIG>, a stator <NUM> is shown. The stator <NUM> is similar to the stator <NUM> (shown in <FIG>) and additionally includes a coolant jacket <NUM>. The coolant jacket <NUM> defines at least partially a coolant channel <NUM> having a first flow area <NUM> and a second flow area <NUM>, the first flow area <NUM> having a greater area than the second flow area <NUM>. Between the first flow area <NUM> and the second flow area <NUM> the coolant channel <NUM> tapers in flow area size. For example, between the first flow area <NUM> defined on the first end portion <NUM> of the core <NUM> the coolant channel <NUM> tapers to the second flow area <NUM> at a location along the intermediate portion <NUM> of the coolant channel <NUM>. Tapering the coolant channel <NUM> graduates the resistance presented to the liquid coolant <NUM> (shown in <FIG>) traversing the coolant channel <NUM>, promoting laminar flow within the coolant channel <NUM> and limiting pressure loss in the liquid coolant <NUM> during traverse of the stator <NUM>.

With reference to <FIG>, a method <NUM> of making a stator, e.g., the stator <NUM> (shown in <FIG>), is shown. The method <NUM> includes conformally depositing a coolant jacket, e.g., the coolant jacket <NUM> (shown in <FIG>), on the outer surface of a core, e.g., the outer surface <NUM> (shown in <FIG>) of the core <NUM> (shown in <FIG>), as shown with box <NUM>. The coolant jacket is deposited conformally on the core by depositing a first layer using an additive manufacturing technique, e.g., the first layer <NUM> (shown in <FIG>), on the outer surface of the core, as shown with box <NUM>, and depositing one or more second layer, e.g., the second layer <NUM> (shown in <FIG>), on the outer surface of the core, as shown with box <NUM>. The second layer can be deposited on the outer surface of the core, the first layer, or both the outer surface of the core and the first layer, as shown with box <NUM>. It is contemplated that the coolant jacket be deposited using an additive manufacturing technique, such a cold-spray additive technique, wire addition additive technique, or a laser deposition technique.

As shown with box <NUM>, the method <NUM> includes defining a coolant channel within the coolant jacket during the depositing of the first layer and the one or more second layer using the additive manufacturing technique. In certain also embodiments a heat transfer structure, e.g., the heat transfer structure <NUM> (shown in <FIG>), is defined within the coolant channel, as shown with box <NUM>. As shown with box <NUM>, the heat transfer structure can be defined using an additive manufacturing technique, e.g., the additive manufacturing technique used deposit the coolant jacket. As shown with box <NUM>, the heat transfer structure is defined using a subtractive manufacturing technique, such as with a stamping or milling operation by way of illustration and non-limiting example. It is contemplated that defining the heat transfer structure can include defining one or more of a turbulator, e.g., the one or more turbulator <NUM> (shown in <FIG>), a riblet, e.g., the one or more riblet <NUM> (shown in <FIG>), or the one or more spire <NUM> (shown in <FIG>), as shown with box <NUM>.

Electrical machines typically generate heat during operation due resistive heating of electrical conductors and magnetic flux communication. The heat is generally communicated to the external environment by conduction through the frame of the electrical machine frame to a fluid, and therethrough to the ambient environment. Since the rate of heat rejection through the frame can influence the rating of the electrical machine for a given level of current flow and/or magnetic flux, structures like fins, coolant tubes, or coolant jackets can be thermally coupled to the frame to route coolant fluid across the electrical device. Fins increase the area of the frame for heat rejection to the ambient environment while coolant tubes and coolant jackets sink heat from the electrical machine across an interface between the frame and coolant jacket.

In embodiments described herein electrical machines employ stators having a core and coolant jacket. The coolant jacket is conformally deposited over the outer surface of the core and at least partially defines therein a coolant channel. The coolant jacket includes two or more layers deposited on the core and/or one another, limiting the thickness of the coolant jacket by limiting (or eliminating entirely) the hoop stress associated with shrink-fitting the coolant jacket to the core. In certain embodiments the first layer and the one or more second are deposited such that the thermal resistance of the interface between the core and the coolant jacket is smaller than that of a shrink-fit coolant jacket - the interface having as much as <NUM>% less thermal resistance than a shrink-fit coolant jacket in contemplated embodiments. In accordance with certain embodiment the coolant channel can be defined with non-linear share, such as a helical shape by way of illustration and not limitation. It is also contemplated that the coolant channel can widen and narrow according to coolant flow characteristics for the heat loading at given location on the core, the coolant channel widening at locations radially adjacent to the winding end turns for example.

Claim 1:
A stator (<NUM>), comprising:
a core (<NUM>) with an outer surface (<NUM>) extending about a rotation axis (<NUM>), wherein the outer surface (<NUM>) defines one or more surface discontinuity (<NUM>) therein; and
a coolant jacket (<NUM>) deposited on the outer surface (<NUM>) of the core and defining a coolant channel (<NUM>), wherein the coolant jacket (<NUM>) comprises a plurality of layers (<NUM>/<NUM>) conformally disposed on the outer surface (<NUM>) of the core (<NUM>) and inhabiting the one or more surface discontinuity (<NUM>),
wherein the plurality of layers (<NUM>/<NUM>) each have a radial thickness and include a first layer (<NUM>) deposited on the outer surface (<NUM>) of the core (<NUM>) and circumferentially about the core (<NUM>), and a second layer (<NUM>) deposited on the first layer (<NUM>) and circumferentially about the outer surface (<NUM>) of the core (<NUM>) at a location radially outward of the first layer (<NUM>);
the first layer (<NUM>) of the plurality of layers (<NUM>/<NUM>) comprises a fused metallic particulate (<NUM>),
the second layer (<NUM>) of the plurality of layers comprises a fused metallic particulate (<NUM>),
wherein the second layer (<NUM>) is fused to the first (layer <NUM>);
wherein either or both of the fused metallic particulate (<NUM>) and the fused metallic particulate (<NUM>) include metallic material (<NUM>), including aluminium or titanium and/or alloys thereof;
characterized in that: :
a heat transfer structure (<NUM>/<NUM>) arranged within the coolant channel (<NUM>),
wherein the heat transfer structure (<NUM>/<NUM>) is selected from a group including a turbulator (<NUM>), a riblet (<NUM>), and a spire (<NUM>);
wherein the heat transfer structure (<NUM>/<NUM>) is formed from a fused particulate from the same process as the fused metallic particulate (<NUM>) and/or the fused metallic particulate (<NUM>), and is spaced apart from the coolant jacket (<NUM>) by a portion of the outer surface (<NUM>) of the core (<NUM>);
wherein the heat transfer structure (<NUM>/<NUM>) is defined by the outer surface (<NUM>) of the core (<NUM>) or defined by at least one of the plurality of layers (<NUM>/<NUM>) in the coolant channel (<NUM>).