AU2020357566B2

AU2020357566B2 - Electric motor with enhanced thermal characteristics

Info

Publication number: AU2020357566B2
Application number: AU2020357566A
Authority: AU
Inventors: Joseph L. DOBMEIER; Steven Huard
Original assignee: Parker Hannifin Corp
Current assignee: Parker Hannifin Corp
Priority date: 2019-10-03
Filing date: 2020-07-07
Publication date: 2023-04-27
Anticipated expiration: 2040-07-07
Also published as: IL291877A; CA3153132A1; WO2021066917A1; JP7675708B2; CA3153132C; EP4038727A1; JP2025069321A; JP2022550460A; KR20220069105A; IL291877B1; KR102716341B1; AU2020357566A1

Abstract

An example stator of an electric motor includes a lamination stack comprising a plurality of segments (600) disposed adjacent to each other in a radial array; a slot formed in a segment of the plurality of segments of the lamination stack; a slot liner (606) disposed in the slot and configured to be electrically-insulating; a thermally- conductive gap filler (1000) disposed in a gap (800) between the slot liner and the segment; and wire windings disposed in the slot.

Description

Electric Motor with Enhanced Thermal Characteristics

CROSS REFERENCE TO RELATED APPLICATION

[0001] The present application claims priority to U.S. Provisional Application No. 62/909,850,

filed on October 3, 2019, which is hereby incorporated by reference in its entirety.

TECHNICAL FIELD

[0002] This disclosure relates generally to systems and assemblies involving an electric motor

with enhanced thermal characteristics and improved heat transfer to the surrounding

environment of the electric motor.

BACKGROUND

[0003] Any discussion of the prior art throughout the specification should in no way be

considered as an admission that such prior art is widely known or forms part of common general

knowledge in the field.

[0004] An electric motor is an electrical machine that converts electrical

energy into mechanical energy. Most electric motors operate through the interaction between

the motor's magnetic field and electric current in wire windings to generate force in the form

of rotation of a shaft. Electric motors can be powered by direct current (DC) sources, such as

from batteries, motor vehicles or rectifiers, or by alternating current (AC) sources, such as a

power grid, inverters or electrical generators.

[0005] The torque and power generated at the shaft of the motor are limited by how much

current or electric power is input through the wire windings. Increasing current beyond a

certain limit can increase the temperature of the wire windings and cause damage to the wires

and the electric motor.

[0006] It may thus be desirable to have an electric motor with enhanced thermal characteristics

to enable improved heat transfer from the wire windings, thereby reducing the temperature of the wire windings for a given current input, preventing damage to the motor, and enabling an increase in the current limit. It is with respect to these and other considerations that the disclosure made herein is presented.

SUMMARY

[0007] The present disclosure describes implementations that relate to an electric motor with

enhanced thermal characteristics.

[0008] In a first example implementation, the present disclosure describes a stator of an electric

motor. The stator comprises: (i) a lamination stack; (ii) a slot formed in the lamination stack;

(iii) a slot liner disposed in the slot and configured to be electrically-insulating; (iv) a thermally

conductive gap filler disposed in a gap between the slot liner and the lamination stack; and (v)

wire windings disposed in the slot.

[0009] In a second example implementation, the present disclosure describes an assembly of

an electric motor. The assembly includes a stator having an open annular space. The stator

comprises: (i) a lamination stack comprising a plurality of segments disposed adjacent to each

other in a radial array; (ii) a plurality of slots formed between adjacent segments of the plurality

of segments of the lamination stack; (iii) respective slot liners disposed in the plurality of slots

and configured to be electrically-insulating; (iv) a thermally-conductive gap filler disposed in

respective gaps between the respective slot liners and the plurality of segments of the

lamination stack; and (v) wire windings disposed in the plurality of slots. The assembly further

includes a rotor disposed in the open annular space of the stator and comprising: a steel core,

and a plurality of magnets disposed in a respective radial array about the steel core.

[0010] In a third example implementation, the present disclosure describes a method. The

method includes: (i) providing a segment of a lamination stack of a stator of an electric motor,

wherein the segment of the lamination stack comprises a slot; (ii) providing a slot liner formed of an electrically-insulating material; (iii) applying a thermally-conductive gap filler to an exterior surface of the slot liner; (iv) inserting the slot liner with the thermally-conductive gap filler applied thereto into the slot of the segment of the lamination stack, such that the thermally-conductive gap filler is disposed between the exterior surface of the slot liner and the segment; and (v) winding a wire about the segment such that the slot liner and the thermally conductive gap filler are disposed between the wire and the segment.

[0011] In a fourth example implementation of the present invention there, is provided a stator

of an electric motor, the stator comprising:

a lamination stack;

a slot formed in the lamination stack;

a slot liner disposed in the slot and configured to be electrically-insulating;

a thermally-conductive gap filler disposed in a gap between the slot liner and the

lamination stack; and

wire windings disposed in the slot such that the slot liner is between the wire windings

and the thermally-conductive gap filler, and the slot liner electrically insulates the wire

windings from the lamination stack.

[0012] In a fifth example implementation of the present invention, there is provided an

assembly of an electric motor, the assembly comprising: a stator having an open annular space

and comprising:

a lamination stack comprising a plurality of segments disposed adjacent to each other

in a radial array,

a plurality of slots formed between adjacent segments of the plurality of segments of

the lamination stack, respective slot liners disposed in the plurality of slots and configured to be electrically insulating, a thermally-conductive gap filler disposed in respective gaps between the respective slot liners and the plurality of segments of the lamination stack, and wire windings disposed in the plurality of slots, such that the respective slot liners are between the wire windings and the thermally-conductive gap filler, and the respective slot liners electrically insulate the wire windings from the lamination stack; and a rotor disposed in the open annular space of the stator and comprising: a steel core, and a plurality of magnets disposed in a respective radial array about the steel core.

[0013] In a sixth example implementation of the present invention, there is provided a method

comprising:

providing a segment of a lamination stack of a stator of an electric motor, wherein the

segment of the lamination stack comprises a slot;

providing a slot liner formed of an electrically-insulating material;

inserting the slot liner into the slot of the segment of the lamination stack,

applying a thermally-conductive gap filler in a gap between the slot liner and the

segment of the lamination stack, such that the thermally-conductive gap filler is disposed

between the exterior surface of the slot liner and the segment; and

winding a wire about the segment such that the slot liner is disposed between the wire

and the thermally-conductive gap filler and the thermally-conductive gap filler is disposed

between the slot liner and the segment.

[0014] The foregoing summary is illustrative only and is not intended to be in any way limiting.

In addition to the illustrative aspects, implementations, and features described above, further

aspects, implementations, and features will become apparent by reference to the figures and

the following detailed description.

[0015] Unless the context clearly requires otherwise, throughout the description and the claims,

the words "comprise", "comprising", and the like are to be construed in an inclusive sense as

opposed to an exclusive or exhaustive sense; that is to say, in the sense of "including, but not

limited to".

BRIEF DESCRIPTION OF THE FIGURES

[0016] The novel features believed characteristic of the illustrative examples are set forth in

the appended claims. The illustrative examples, however, as well as a preferred mode of use,

further objectives and descriptions thereof, will best be understood by reference to the

following detailed description of an illustrative example of the present disclosure when read in

conjunction with the accompanying Figures.

[0017] Figure 1 illustrates a perspective view of an electric motor, in accordance with an

example implementation.

[0018] Figure 2 illustrates a perspective view of a stator and a rotor mounted within the stator,

in accordance with an example implementation.

[0019] Figure 3 illustrates a perspective view of a lamination stack of a stator, in accordance

with an example implementation.

[0020] Figure 4 illustrates an exploded view of insulation slot liners disposed in respective

slots of a lamination stack, in accordance with an example implementation.

[0021] Figure 5 illustrates a perspective view of an individual slot liner, in accordance with an

example implementation.

[0022] Figure 6 illustrates components associated with a segment of a lamination stack prior

to assembly and winding wires of a stator, in accordance with an example implementation.

[0023] Figure 7 illustrates a segment of a lamination stack after assembly of its components

and winding a wire, in accordance with an example implementation.

[0024] Figure 8 illustrates a partial cross-sectional view of a segment of a lamination stack, in

accordance with an example implementation.

[0025] Figure 9 illustrates placing thermally-conductive gap filler in portions of gaps between

a slot liner and segment of a lamination stack and between a cooling tube and the segment of

the lamination stack, in accordance with an example implementation.

[0026] Figure 10 illustrates placing thermally-conductive gap filler throughout interfaces

between a slot liner and a segment of a lamination stack and between a cooling tube and the

segment of the lamination stack, in accordance with an example implementation.

[0027] Figure 11 is a flowchart of a method for assembling a stator or an electric motor, in

accordance with an example implementation.

DETAILED DESCRIPTION

[0028] The torque and power generated at a shaft of an electric motor can be limited by how

much current or electric power is input through the wire windings of the electric motor.

Increasing current beyond a certain limit can cause damage to the wires and motor.

[0029] Within examples, disclosed herein are systems and assemblies that relate to an electric

motor with enhanced thermal and heat transfer characteristics. Particularly, the disclosed

systems using thermally-conductive gap filler between wire winding insulation liners and the lamination stack of the electric motor. The thermally-conductive gap filler can also be placed between cooling tubes of the electric motor and the lamination stack channels through which the cooling tubes are disposed. The thermally-conductive gap filler can enhance heat transfer from the wire windings of the electric motor.

[0030] Improved heat transfer can enable increasing the current limit of the electric motor, and

therefore enable producing higher torque and power for the same electric motor. Improved

heat transfer can also enable running the electric motor at a cooler temperature for a given

torque output, thereby improving efficiency of the electric motor.

[0031] Figure 1 illustrates a perspective view of an electric motor 100, in accordance with an

example implementation. The electric motor 100 includes a stator 102. The stator 102 is

configured to generate a magnetic field. Particularly, as described below, the stator 102 can

include wire windings wrapped about a lamination stack, and when electric current is provided

through the wire windings, a magnetic field is generated. The stator 102 can also include a

mounting location 103 to enable mounting the electric motor 100 to a machine or device that

utilizes the electric motor 100.

[0032] The electric motor 100 further includes a rotor 104. The stator 102 can have an open

annular space in which the rotor 104 is disposed. The rotor 104 can have magnets mounted

thereto that can interact with the magnetic field generated by the stator 102 in order to rotate

and produce torque. The rotor 104 can rotate relative to the stator 102 by being mounted to the

stator 102 via a bearing 106, for example.

[0033] A shaft 108 can be coupled to the rotor 104, and the shaft 108 is configured to transmit

the torque generated by the rotor 104, e.g., to a gear box or a component of a machine to rotate

such component. The electric motor 100 can include another mounting location 109 to further facilitate mounting the electric motor 100 to the machine that utilizes the generated torque and resulting rotary motion of the shaft 108.

[0034] The electric motor 100 can include other components such as feedback device 110 (e.g.,

sensor) that provides sensor information indicative of the position of the rotor 104 to an

electronic controller of the electric motor 100. The electronic controller can then energize the

wire windings of the stator 102 at the appropriate time to achieve a desired torque.

[0035] Cables 112 can be used to provide electric current to the wire windings of the stator

102. The cables 112 can also be used to transmit electric signals generated by the feedback

device 110 to indicate position of the rotor 104 to an amplifier.

[0036] Figure 2 illustrates a perspective view of an assembly 200 of the stator 102 and the rotor

104 mounted within the stator 102, in accordance with an example implementation. The stator

102 can have a steel core. The stator 102 can include a lamination stack. The lamination stack

can be made as a single piece (e.g., unitary construction) or can comprise multiple segments as

described in below with respect to Figure 3.

[0037] Electric wires are wound through segments of the lamination stack. For example,

Figure 2 illustrates individual coils (bundles of wires), such as coil 201, wound through the

segments of the stator 102. The coils are separated from each other to prevent electric shorts

from occurring. When electric current is provided through the wires, the coils can operate as

electromagnets and generate a magnetic field.

[0038] The rotor 104 can also have a steel core. The rotor 104 can further have multiple

magnets (e.g., permanent magnets), such as magnet 202, disposed in a radial or circumferential

array about the steel core of the rotor 104.

[0039] The electric current provided to the coils of the stator 102 can be provided in a particular

sequence to the individual coils of the respective segments of the stator 102. As such, the magnetic field generated by the coils of the stator can effectively be moving or changing in a circular manner around the stator 102. The magnetic field interacts with the magnets of the rotor 104, and such interaction of the magnetic field with the magnets causes the rotor 104 (and the shaft 108 coupled thereto) to rotate.

[0040] Figure 3 illustrates a perspective view of a lamination stack 300 of the stator 102, in

accordance with an example implementation. As illustrated in Figure 3, the lamination stack

300 is generally donut-shaped and has an open annular space 302 in which the rotor 104 can

be disposed. The lamination stack 300 comprises laminated electrical steel sheets.

Lamination is the technique/process of manufacturing a material in multiple layers, so that the

composite material achieves improved strength, stability, sound insulation, appearance or other

desirable electrical properties.

[0041] The lamination stack 300 can be made of silicon steel, also known as electrical steel,

which comprises steel with silicon added to it. Adding silicon to steel increases its electrical

resistance, improves the ability of magnetic fields to penetrate it, and reduces the steel's

hysteresis loss. The lamination stack 300 represents the core of the stator 102 and

is laminated and insulated in order to reduce induced circulating currents and associated heat

as electric current is modulated through the wire windings of the stator 102.

[0042] In an example, the lamination stack 300 can be made as a single piece or single

component that is not segmented. For instance, the lamination stack 300 can have teeth similar

to a gear, and the slots or spaces between the teeth can be configured to receive wires

therethrough.

[0043] In another example, the lamination stack 300 includes multiple segments, such as

segment 304, segment 306, and segment 308, disposed adjacent to teach other in a radial array

and interface with each. The segments are generally formed or shaped as I-beams that have C shaped side channels or slots on each side thereof. Thus, when two adjacent segments interface with each other, a slot is formed therebetween and comprises the C-shaped channels or respective slots of the two adjacent segments. For example, a slot 310 is formed between the segment 304 and the segment 306, and a slot 312 is formed between the segment 306 and the segment 308. Although the description below refers to a multiple segment construction of the lamination stack 300, it should be understood that similar description would apply to a lamination stack made of having unitary construction and made as a single component that is not segmented. Such a component can have holes, channels, or slots similar to the slots 310,

312 made therein to receive the slot liners described below.

[0044] Each of the slots 310, 312 comprises one slot (partial slot) formed in one segment of

the lamination stack 300 and a second slot (partial slot) formed in an adjacent segment of the

lamination stack 300. The term "slot" is used herein to refer to a complete slot such as the slot

310 or the slot 312 and is also used to refer to an individual slot or partial slot (a C-shaped

channel) of a segment of the lamination stack. Wires are wound through the slots of the

lamination stack 300 in wire bundles or coils such as the coil 201 shown in Figure 2.

[0045] As electric current is provided through the wires, the temperature of the wires increases

and heat is generated. The heat can be referred to as winding losses. The rising temperature

of the wires can cause damage and limit performance of the electric motor 100 as described

below.

[0046] In examples, to cool the lamination stack 300 and the wires disposed therein, the

lamination stack 300 can be liquid-cooled. As shown in Figure 3, each of the segments can

have channels disposed therein that are semi-circular in shape. For instance, the segment 304

has a semi-circular channel 314 disposed longitudinally across an exterior peripheral surface

of the segment 304. A tube can be disposed through the semi-circular channel 314, and cooling fluid can be provided through such tube, thereby absorbing some of the heat generated by the wires and cooling the lamination stack 300 and the wires disposed therein.

[0047] The coils of the stator 102 are energized individually as mentioned above to generate a

moving or changing magnetic field. As such, it is desirable to electrically insulate the wires of

the coils from the lamination stack 300 to prevent shorting or electric connections between

wires of two adjacent coils. To isolate the wires from the segments of the lamination stack 300,

insulation liners can be disposed in the slots of the lamination stack 300 to operate as electric

insulators. For example, paper liners can be used as insulation liners.

[0048] Figure 4 illustrate an exploded view of insulation slot liners disposed in respective slots

of the lamination stack 300, and Figure 5 illustrates a perspective view of an individual slot

liner 500, in accordance with an example implementation. The slots of the lamination stack

300 can receive therein the respective insulation papers slot liners shown in a radial array in

Figure 4. For example, insulation paper slot liner 400 can be inserted in the slot 310, and

insulation paper slot liner 402 can be inserted in the slot 312. In an example, an insulation

paper slot liner can be composed of two individual slot liners, each slot liner of the two

individual slot liners can have a U-shape or C-shape, such that when the meet at their lateral

edges, a slot or channel is formed therebetween through which the wires of coils of the stator

102 are disposed.

[0049] Figure 5 illustrates an example of such a slot liner 500. The slot liner 500 can have a

first side portion 502, a second side portion 504, and a connecting portion 506 that couples or

connects the side portion 502 to the side portion 504. With this configuration, the slot liner

500 forms a channel (e.g., C-shaped channel) therein.

[0050] When two slot liners similar to the slot liner 500 are disposed next to each other such

that the respective edges of the side portions of the slot liners interface with each other (i.e., the connecting portions do not interface with each, but are rather disposed opposite each other with the respective C-channels disposed therebetween), an insulation paper slot liner of the insulation paper slot liners shown in Figure 4 is formed. The slot liners (e.g., the slot liner 500) can be inserted individually in the slots of the respective segments of the lamination stack 300.

[0051] In another example, the insulation paper slot liners 400, 402 can be made as a single

rectangular-shaped liner, rather than two individual slot liners. In still another example, rather

than having separate insulation paper slot liners like the insulation paper slot liners 400, 402,

the slots liners of the entire lamination stack 300 can be made as a single component that goes

all around to line the respective slots of the lamination stack 300.

[0052] Figure 6 illustrates components associated with a segment 600 of the lamination stack

300 prior to assembly and winding wires of the stator 102, in accordance with an example

implementation. The segment 600 can represent any of the segments of the lamination stack

300 (e.g., any of the segments 304, 306, 308).

[0053] As mentioned above, the segments of the lamination stack 300 are generally formed or

shaped as I-beams that have C-shaped channels on each side thereof. The segment 600 can

have a first slot or first channel 602 and a second slot or second channel 604. A first slot liner

606 can be disposed in the first channel 602, and similarly, a second slot liner 608 can be

disposed in the second channel 604. The slot liners 606, 608 can also be C-shaped to conform

to shape of the channels 602, 604 of the segment 600. When wires are wound about the

segment 600, the slot liners 606, 608 insulate the wires from sides of the segment 600 (i.e., the

surfaces of the channels 602, 604).

[0054] The slot liners 606, 608 do not extend to the ends of the segment 600 and might not

isolate end surfaces of the segment 600 from end-turns of the wires as the wires wrap around

the ends of the segment 600. To insulate end-turns of the wires, a first end-turn insulator 610 can be inserted at a first end of the segment 600, and a second end-turn insulator 612 can be inserted at a second end of the segment 600 prior to winding the wire.

[0055] Figure 7 illustrates the segment 600 after assembly of its components and winding a

wire 700, in accordance with an example implementation. As depicted in Figure 7, the slot

liners, such as the slot liner 606, are positioned in their respective channels of the segment 600,

and the end-turn insulators 610, 612 are also inserted at the respective ends of the segment 600.

The wire 700 can then be wound about the segment 600 to form a coil associated with the

segment 600.

[0056] With this configuration, the wire 700 is electrically insulated from the segment 600, and

therefore when the multiple segments of the lamination stack 300 are assembled in a radial

array to form the lamination stack 300, their respective coils are electrically-insulated from

each other. Further, wires can be coated with an electrically-insulating material (e.g., a

synthetic polymer such as nylon polyamide) so as to isolate the individual wires of a given

segment from each other and prevent electrical shorting.

[0057] Once inserted in the channels 602, 604, the exterior surfaces of the slot liners 606, 608

can interface with interior surface of the segment 600 of the lamination stack 300. However,

gaps can separate the exterior surface of the slot liners 606, 608 and the interior surface of the

segment 600.

[0058] Figure 8 illustrates a partial cross-sectional view of the segment 600, in accordance with

an example implementation. As depicted in Figure 8, when the slot liner 606 is inserted in the

channel 602 of the segment 600, a gap 800 can separate exterior surfaces of the side portions

(e.g., the side portions 502, 504) and the connecting portion (e.g., the connecting portion 506)

from the interior surfaces of the channel 602 of the segment 600 in which the slot liner 606 is

disposed.

[0059] As mentioned above with respect to Figure 3, each of the segments of the lamination

stack 300 can have a semi-circular channel disposed therein to receive a cooling tube

therethrough. For example, the segment 600 can receive a cooling tube 802 as depicted in

Figure 8. Another gap 804 can separate the cooling tube 802 from the interior surface of the

segment 600 that bounds the semi-circular channel in which the cooling tube 802 is disposed.

[0060] When electric current is provided through the wires (e.g., the wire 700) of the electric

motor 100, heat is generated and temperatures of the components of the electric motor 100 can

rise. The heat generated from the wire or coils of the electric motor 100 can be referred to as

winding losses and can be determined based on the magnitude of the electric current (1) and

electric resistance (R) of the wire. Particularly, the winding losses can be determined as I2 R.

[0061] Further, the heat generated (the winding losses) can be transferred to the surrounding

environment of the electric motor 100 at a particular heat transfer rate (q) that is based on

temperature of the wire (Tw), ambient temperature (Ta), and winding-to-ambient thermal

resistance (Rthwa). Particularly, the heat transfer can be determined by the following equation:

Winding Losses = IR = q =(TwT Rthwa

(1)

[0062] For a given ambient temperature Ta, electric resistance R, and winding-to-ambient

thermal resistance Rthwa, equation (1) indicates that the winding temperature Tw is

proportional to the square of the electric current (2). During operation of the electric motor

100, if the winding temperature Tw exceeds a threshold level, damage to the electric motor 100

can occur. For example, the coating of the wires (e.g., polyamide coating) can be damaged,

thereby causing the individual wires of a coil or winding to touch each other and electric short

to occur.

[0063] To prevent damage to the electric motor 100, the magnitude of the electric current (1) is

limited so as to prevent the winding losses from exceeding a particular level that would cause

the winding temperature Tw to exceed a threshold level. However, limiting the magnitude of

the electric current (I) can also limit the magnitude of the torque that the electric motor 100 can

produce. In particular, the torque (T) that the electric motor 100 produces can be determined

as T = KtI, where K, is the motor torque constant and is based on a constant multiplied by a

length of the stator 102 and the number of turns of the wire. The power (P) generated by the

electric motor 100 can be determined as P = To = KtIo, where o is the rotational speed of

the rotor 104 or the shaft 108 coupled thereto.

[0064] As such, limiting the magnitude of the electric current I also limits the torque T and

power P that the electric motor 100 can generate. Further, at a particular power level, the

amount of heat generated can affect efficiency of the electric motor 100 (e.g., the ratio of the

power P produced by the electric motor 100 divided by the electric power provided to the

electric motor 100). Running the electric motor 100 at a lower winding temperature Tw for a

particular power output P can increase efficiency of the electric motor 100.

[0065] The slot liners discussed above (e.g., the slot liners 500, 606, 608) are configured to be

electrically-insulating, but might not be thermally-conductive and may thus cause a higher

thermal resistance to, and may impede, heat transfer from the wires to the environment. In

other words, the slot liners being not configured to be made of a thermally-conductive material

may increase Rthwa. Further, if there is a gap (e.g., the gap 800) between a slot liner and the

segment of the lamination stack, the gaps can be filled with air, which may further increase

Rthwa.

[0066] One way to enable the electric motor 100 to receive higher magnitudes of electric

current (1) without damaging its components involves reducing the winding-to-ambient thermal

resistance (Rthwa). Based on equation (1) above, reducing Rthwa can maintain the winding temperature Tw at a particular level for a higher magnitudes of electric current (1), which enables the electric motor 100 to produce higher torque (T) and power (P) without damaging its components. Alternatively, the same current level (1) can be used and the electric motor 100 can generate the same torque (T) and power (P) while reducing the winding temperature Tw, thereby increasing efficiency of the electric motor 100.

[0067] In an example, reducing the winding-to-ambient thermal resistance (Rthwa) can be

achieved by placing a thermally-conductive gap filler in the gaps between the slot liners (e.g.,

the slot liner 606) and the lamination stack 300 (e.g., in the gap 800). Additionally or

alternatively, a thermally-conductive gap filler can be placed in the gap between the cooling

tubes (e.g., the cooling tube 802) and the lamination stacks 300 (e.g., in the gap 804). Such a

thermally-conductive gap filler can reduce thermal resistance (resistance to heat flow from the

windings to the lamination stack 300 and then to the environment), thus reducing Rthwa.

[0068] In examples, the thermally-conductive gap filler can be placed in, or can line, a portion

of the respective gap (e.g., the gap 800 and/or the gap 804). In other examples, the thermally

conductive gap filler can be used to fill the entire interface between the slot liners and the

lamination stack 300 and the interface between the cooling tubes and the lamination stack 300.

[0069] Figure 9 illustrates placing thermally-conductive gap filler in portions of the gap 800

and the gap 804, in accordance with an example implementation. As depicted in Figure 9,

thermally-conductive gap filler 900 (illustrated by a dashed line) can be placed in a portion

between the connecting portion (e.g., vertical portion) of the slot liner 606 and the interior

surface of the segment 600 of the lamination stack 300. A respective thermally-conductive gap

filler 902 (illustrated by a curved dashed line) can also be placed in a portion of the gap 804

between a respective exterior surface of the cooling tube 802 and the interior surface of the

semi-circular channel of the segment 600 in which the cooling tube 802 is disposed.

[0070] In examples, the thermally-conductive gap filler 900, 902 can be placed in the segment

600 of the lamination stack 300 prior to insertion of the slot liner 606 and the cooling tube 802.

Alternatively, the thermally-conductive gap filler 900, 902 can be applied to exterior surfaces

of the slot liner 606 and the cooling tube 802 prior to their insertion in their respective channels

of the lamination stack 300.

[0071] Figure 10 illustrates placing thermally-conductive gap filler throughout interfaces

between the slot liner 606 and the segment 600 and between the cooling tube 802 and the

segment 600, in accordance with an example implementation. As depicted in Figure 10,

thermally-conductive gap filler 1000 (illustrated by a dashed line) can be placed throughout the

gap 800 between, or disposed along, the side portions and the connecting portion of the slot

liner 606 and the interior surface of the segment 600 that bounds the channel in which the slot

liner 606 is disposed. Thermally-conductive gap filler 1002 (illustrated by a curved dashed

line) can also be placed throughout the gap 804 between the cooling tube 802 and the interior

surface of the semi-circular channel of the segment 600 in which the cooling tube 802 is

disposed.

[0072] Figures 9-10 illustrate a partial cross-section depicting one side or one half of the

segment 600 and using thermally-conductive gap fillers with respect to a portion of the segment

600. It should be understood, however, that the thermally-conductive gap fillers can be used

on the other side of the segment 600 and can be used with all or some of the other segments of

the lamination stack 300. Further, as mentioned above, the thermally-conductive gap filler can

be placed in the segments of the lamination stack 300 prior to insertion of the slot liner 606 and

the cooling tube 802, or alternatively, the thermally-conductive gap filler can be applied to the

slot liners (e.g., applied to the side portions 502, 504 and the connecting portion 506 of the slot

liner 500) and the cooling tubes (e.g., the cooling tube 802) prior to their insertion in their

respective channels.

[0073] Different types of thermally-conductive fillers can be used. For example, the thermally

conductive filler can take the form of a paste comprising a mineral oil with thermally

conductive solid particles (e.g., metallic material) suspended therein. In other examples, the

thermally conductive filler can take the form of a thermally-conductive pad comprising a

silicone polymer that is combined with a thermal medium (e.g., ceramic).

[0074] In an example, the thermally-conductive gap filler can include silicone grease or wax

filled with a thermally-conductive material such as aluminum oxide. Such silicon grease can

take the form of a semi-liquid or solid material at normal room temperature, and may liquefy

or soften at elevated temperatures to flow and better conform to any irregularities of the

interface surfaces between the slot liners and the segments of the laminations stack 300 or

between the cooling tubes and the lamination stack 300. In some examples, the silicon greases

or waxes can be provided in the form of a film. To provide such a film, a substrate, web, or

other carrier can be provided.

[0075] In another example, the thermally-conductive gap fillers can include a cured, sheet-like

material. Such materials can be compounded as containing one or more thermally-conductive

particulate fillers dispersed within a polymeric binder, and may be provided in the form of

cured sheets, tapes, pads, or films. Example binder materials include silicones, urethanes,

thermoplastic rubbers, and other elastomers, with example fillers including aluminum oxide,

magnesium oxide, zinc oxide, boron nitride, and aluminum nitride.

[0076] In another example, the thermally-conductive gap fillers can include a cured, form

stable, sheet-like, thermally-conductive material for transferring thermal energy from the wire

windings and the lamination stack 300 to the environment. Such material can be formed of a

urethane binder, a curing agent, and one or more thermally-conductive fillers. The fillers, which

may include aluminum oxide, aluminum nitride, boron nitride, magnesium oxide, or zinc oxide,

can range in particle size from about 1-50 microns or can comprise nanoparticles, for example.

[0077] In an example, the thermally-conductive gap fillers can include phase-change materials,

which can be self-supporting and form-stable at room temperature for ease of handling. Such

phase-change materials can liquefy or otherwise soften at temperatures within the operating

temperature range of the electric motor 100 to form a viscous, thixotropic phase, which can

better conform to the interface surfaces between the slot liners and the segments of the

laminations stack 300 or between the cooling tubes and the lamination stack 300. The phase

change materials, which can be supplied as free-standing films, or as heated screen printed onto

a substrate surface, can operate as greases and waxes in conformably flowing within the

operating temperature of the electric motor 100 under relatively low clamping pressures of

about 5 pounds per square inch (psi).

[0078] In another example, the thermally-conductive gap fillers can include a tape or sheet

comprising an inner and outer release liner and an interlayer of a thermal compound. One side

of the tape or sheet can be coated with a thin layer of a pressure-sensitive adhesive (PSA) for

the application of the material to the heat transfer surfaces between the slot liners and the

segments of the laminations stack 300 or between the cooling tubes and the lamination stack

300.

[0079] Other example thermally-conductive gap filler materials can include thermal interface

compounds, caulks, form-in-place materials, or encapsulants. These materials can be provided

as charged within one or more tubes, containers as one or two-part liquid or otherwise fluent,

filled reactive systems, which cure at room or elevated temperatures to be formed-in-place

within the gaps (e.g., the gaps 800, 804).

[0080] In another example, the thermally-conductive gap fillers can include a thermally

conductive compound that is dispensable under an applied pressure as issued as a bead or mass

from a nozzle or other orifice. The material, which may be charged in a tube, cartridge, or

other container, can be dispensed onto a surface of the slot liners or the cooling tubes, which forms a gap (e.g., the gaps 800, 804) with a segment of the lamination stack 300 or directly into the gaps formed between the adjoining surfaces. As applied, the material can form a bead or mass of material "in place." Within the gap, the formed-in-place bead or mass of the material can operate as an interface material in being conformable to at least partially fill the gaps and to thereby provide a thermally-conductive pathway between the surfaces and reduce the winding-to-ambient thermal resistance (Rthwa). In examples, the material can be fully cross linked or otherwise cured as charged within the tube, cartridge, or other container, or as otherwise supplied. While being of a fluent viscosity, the material can be generally viscoelastic and, as filled, might not exhibit appreciable settling of the metallic filler particles.

[0081] The thermally-conductive compound can be formulated as being fluent under an

applied pressure, yet form-stable as applied to a surface or within the gaps, as a blend or

admixture of: (i) a polymer gel component; and (ii) a particulate filler component, which can

be thermally-conductive particles or a blend thereof. The gel component can be, for example,

a thermoplastic gel or a silicone gel which may be an organopolysiloxane.

[0082] Gels that can be used for the above-mentioned thermally-conductive compound include

systems based on silicones, i.e., polysiloxanes, such as polyorganosiloxane, as well as systems

based on other polymers, which may be thermoplastic or thermosetting, such as polyurethanes,

polyureas, fluoropolymers, chlorosulfonates, polybutadienes, butyls, neoprenes, nitrites,

polyisoprenes, and buna-N, copolymers such as ethylene-propylene (EPR), styrene-isoprene

styrene (SIS), styrene-butadiene-styrene (SBS), ethylene-propylene-diene monomer (EPDM),

nitrile butadiene (NBR), styrene-ethylene-butadiene (SEB), and styrene-butadiene (SBR), and

blends thereof such as ethylene or propylene-EPDM, EPR, or NBR.

[0083] The polymer gel can include fluid-extended polymer system comprising a continuous

polymeric phase or network, which can be chemically, e.g., ionically or covalently, or

physically cross-linked, and an oil, such as a silicone or other oil, a plasticizer, unreacted monomer, or other fluid extender, which swells or otherwise fills the interstices of the network.

The cross-linking density of such network and the proportion of the extender can be controlled

to tailor the modulus, i.e., softness, and other properties of the gel. The polymer gel can also

encompass materials that alternatively can be classified broadly as pseudogels or gel-like as

having viscoelastic properties similar to gels, such has by having a "loose" cross-linking

network formed by relatively long cross-link chains, but as, for example, lacking a fluid

extender. Example polymer or silicone gels can include soft silicone gels such as "GEL-8100"

by NuSilTM.

[0084] The polymer gel component can be rendered thermally-conductive via its loading with

a thermally-conductive filler such as: noble and non-noble metals such as nickel, copper, tin,

aluminum, and nickel; noble metal-plated noble or non-noble metals such as silver-plated

copper, nickel, aluminum, tin, or gold; non noble metal-plated noble and non-noble metals such

as nickel-plated copper or silver; and noble or non-noble metal plated non-metals such as silver

or nickel-plated graphite, glass, ceramics, plastics, elastomers, or mica; and mixtures thereof.

[0085] Figure 11 is a flowchart of a method 1100 for assembling the stator 102 of the electric

motor 100, in accordance with an example implementation.

[0086] The method 1100 may include one or more operations, or actions as illustrated by one

or more of blocks 1102-1110. Although the blocks are illustrated in a sequential order, these

blocks may also be performed in parallel, and/or in a different order than those described

herein. Also, the various blocks may be combined into fewer blocks, divided into additional

blocks, and/or removed based upon the desired implementation. It should be understood that

for this and other processes and methods disclosed herein, flowcharts show functionality and

operation of one possible implementation of present examples. Alternative implementations

are included within the scope of the examples of the present disclosure in which functions may

be executed out of order from that shown or discussed, including substantially concurrent or in reverse order, depending on the functionality involved, as would be understood by those reasonably skilled in the art.

[0087] At block 1102, the method 1100 includes providing a segment (e.g., the segment 600)

of the lamination stack 300 of the stator 102 of the electric motor 100, wherein the segment

600 of the lamination stack comprises a slot (e.g., the channel 602 or the channel 604). The

term "providing" as used herein, and for example with regard to the segment of the lamination

stack 300 or other components (e.g., the slot liner 606) includes any action to make the segment

or any other component available for use, such as supplying the segment or bringing the

segment to an apparatus or to a work environment for further processing (e.g., mounting other

components, winding a wire, etc.).

[0088] At block 1104, the method 1100 includes providing a slot liner (e.g., the slot liner 606)

formed of an electrically-insulating material (e.g., insulation paper).

[0089] At block 1106, the method 1100 includes applying a thermally-conductive gap filler

(e.g., the thermally-conductive gap filler 900, 1000) to an exterior surface of the slot liner.

[0090] At block 1108, the method 1100 includes inserting the slot liner with the thermally

conductive gap filler applied thereto into the slot of the segment of the lamination stack, such

that the thermally-conductive gap filler is disposed between the exterior surface of the slot liner

and the segment.

[0091] At block 1110, the method 1100 includes winding a wire (e.g., the wire 700) about the

segment such that the slot liner and the thermally-conductive gap filler are disposed between

the wire and the segment.

[0092] The method 1100 can further include other steps associated with assembling the stator

102 and the electric motor 100 described above, such as: applying the thermally-conductive

gap filler along one or more of the first side portion, the second side portion, or the connecting portion of the slot liner; applying the thermally-conductive gap filler 902, 1002 to the exterior surface of the cooling tube 802; inserting the cooling tube 802 in the semi-circular channel disposed on an exterior peripheral surface of the segment 600; mounting the end-turn insulators

610, 612 to the segment 600; etc.

[0093] The detailed description above describes various features and operations of the

disclosed systems with reference to the accompanying figures. The illustrative

implementations described herein are not meant to be limiting. Certain aspects of the disclosed

systems can be arranged and combined in a wide variety of different configurations, all of

which are contemplated herein.

[0094] Further, unless context suggests otherwise, the features illustrated in each of thefigures

may be used in combination with one another. Thus, thefigures should be generally viewed as

component aspects of one or more overall implementations, with the understanding that not all

illustrated features are necessary for each implementation.

[0095] Additionally, any enumeration of elements, blocks, or steps in this specification or the

claims is for purposes of clarity. Thus, such enumeration should not be interpreted to require

or imply that these elements, blocks, or steps adhere to a particular arrangement or are carried

out in a particular order.

[0096] Further, devices or systems may be used or configured to perform functions presented

in the figures. In some instances, components of the devices and/or systems may be configured

to perform the functions such that the components are actually configured and structured (with

hardware and/or software) to enable such performance. In other examples, components of the

devices and/or systems may be arranged to be adapted to, capable of, or suited for performing

the functions, such as when operated in a specific manner.

[0097] By the term "substantially" or "about" it is meant that the recited characteristic,

parameter, or value need not be achieved exactly, but that deviations or variations, including

for example, tolerances, measurement error, measurement accuracy limitations and other

factors known to skill in the art, may occur in amounts that do not preclude the effect the

characteristic was intended to provide.

[0098] The arrangements described herein are for purposes of example only. As such, those

skilled in the art will appreciate that other arrangements and other elements (e.g., machines,

interfaces, operations, orders, and groupings of operations, etc.) can be used instead, and some

elements may be omitted altogether according to the desired results. Further, many of the

elements that are described are functional entities that may be implemented as discrete or

distributed components or in conjunction with other components, in any suitable combination

and location.

[0100] While various aspects and implementations have been disclosed herein, other aspects

and implementations will be apparent to those skilled in the art. The various aspects and

implementations disclosed herein are for purposes of illustration and are not intended to be

limiting, with the true scope being indicated by the following claims, along with the full scope

of equivalents to which such claims are entitled. Also, the terminology used herein is for the

purpose of describing particular implementations only, and is not intended to be limiting.

Claims

1. A stator of an electric motor, the stator comprising:

a lamination stack;

a slot formed in the lamination stack;

a slot liner disposed in the slot and configured to be electrically-insulating;

lamination stack; and

windings from the lamination stack.

2. The stator of claim 1, wherein the slot liner comprises a first side portion, a

second side portion, and a connecting portion configured to connect the first side portion to the

second side portion, and wherein the thermally-conductive gap filler is disposed along one or

more of the first side portion, the second side portion, or the connecting portion.

3. The stator of claim 1 or claim 2, further comprising:

a cooling tube disposed in a channel disposed on an exterior peripheral surface of the

lamination stack; and

a respective thermally-conductive gap filler disposed in a respective gap between the

cooling tube and the exterior peripheral surface of the lamination stack.

4. The stator of claim 3, wherein the channel is semi-circular in shape and is

disposed longitudinally across the exterior peripheral surface of the lamination stack.

5. The stator of any one of the preceding claims, wherein the lamination stack

comprises a plurality of segments disposed adjacent to each other in a radial array, wherein

the slot is formed in a segment of the plurality of segments, and wherein the stator further

comprises:

a first end-turn insulator disposed at a first end of the segment between the wire

windings and the segment and configured to electrically-insulating; and

a second end-turn insulator disposed at a second end of the segment between the wire

windings and the segment and configured to electrically-insulating.

6. The stator of any one of the preceding claims, wherein the thermally-conductive

gap filler comprises a mineral oil with thermally-conductive solid particles suspended therein.

7. The stator of any one of claims 1 to 5, whereinthe thermally-conductive gap

filler comprises an admixture of: (i) a polymer gel component; and (ii) a particulate filler

component.

8. An assembly of an electric motor, the assembly comprising:

a stator having an open annular space and comprising:

a lamination stack comprising a plurality of segments disposed adjacent to each

other in a radial array,

a plurality of slots formed between adjacent segments of the plurality of

segments of the lamination stack,

respective slot liners disposed in the plurality of slots and configured to be

electrically-insulating, a thermally-conductive gap filler disposed in respective gaps between the respective slot liners and the plurality of segments of the lamination stack, and wire windings disposed in the plurality of slots, such that the respective slot liners are between the wire windings and the thermally-conductive gap filler, and the respective slot liners electrically insulate the wire windings from the lamination stack; and a rotor disposed in the open annular space of the stator and comprising: a steel core, and a plurality of magnets disposed in a respective radial array about the steel core.

9. The assembly of claim 8, wherein each slot liner comprises two individual slot

liners, wherein each individual slot liner comprises a first side portion, a second side portion,

and a connecting portion configured to connect the first side portion to the second side portion,

and wherein the thermally-conductive gap filler is disposed along one or more of the first side

portion, the second side portion, or the connecting portion.

10. The assembly of claim 8 or claim 9, further comprising:

a plurality of cooling tubes, each cooling tube of the plurality of cooling tubes being

disposed in a channel disposed on an exterior peripheral surface of a segment of the plurality

of segments of the lamination stack; and

cooling tube and the exterior peripheral surface of the segment.

11. The assembly of claim 10, wherein the channel is semi-circular in shape and is

disposed longitudinally across the exterior peripheral surface of the segment.

12. The assembly of any one of claims 8 to 11, further comprising:

a first end-turn insulator disposed at a first end of a respective segment of the plurality

of segments between the wire windings and the respective segment and configured to

electrically-insulating; and

a second end-turn insulator disposed at a second end of the respective segment between

the wire windings and the respective segment and configured to electrically-insulating.

13. The assembly of any one of claims 8 to 12, whereinthe thermally-conductive

14. The assembly of any one of claims 8 to 12, whereinthe thermally-conductive

gap filler comprises an admixture of: (i) a polymer gel component; and (ii) a particulate filler

component.

15. A method comprising:

segment of the lamination stack comprises a slot;

providing a slot liner formed of an electrically-insulating material;

inserting the slot liner into the slot of the segment of the lamination stack,

between the exterior surface of the slot liner and the segment; and winding a wire about the segment such that the slot liner is disposed between the wire and the thermally-conductive gap filler and the thermally-conductive gap filler is disposed between the slot liner and the segment.

16. The method of claim 15, wherein the slot liner comprises a first side portion, a

second side portion, and wherein applying the thermally-conductive gap filler to the exterior

surface of the slot liner comprises applying the thermally-conductive gap filler along one or

17. The method of claim 15 or claim 16, further comprising:

inserting a cooling tube in a channel disposed on an exterior peripheral surface of the

segment; and

applying a respective thermally-conductive gap filler between a respective exterior

surface of a cooling tube and the exterior peripheral surface of the segment.

18. The method of claim 17, wherein inserting the cooling tube in the channel

comprises inserting the cooling tube in a semi-circular channel.

19. The method of any one of claims 15 to 18, further comprising:

mounting a first end-turn insulator at a first end of the segment such that the wire is

electrically-insulated from the first end of the segment; and

mounting a second end-turn insulator at a second end of the segment such that the wire

is electrically-insulated from the second end of the segment.

20. The method of any one of claims 15 to 18, wherein applying the thermally

conductive gap filler comprises applying: (i) a mineral oil with thermally-conductive solid

particles suspended therein, or (ii) an admixture of a polymer gel component and a particulate

filler component.