Stator assembly with winding sets having hairpins from multiple hairpin layers

A stator assembly includes a plurality of stator slots defining multiple slot layers. The assembly includes a plurality of hairpins each having a respective first leg positioned in one of the multiple slot layers and a respective second leg positioned in another of the multiple slot layers. Each hairpin is configured to allow a current to flow from the respective first leg to the respective second leg. The plurality of hairpins is divided into multiple hairpin layers. The hairpins form multiple winding sets, such as first, second, third and fourth winding sets. Each of the winding sets at least partially includes the hairpins from at least two of the multiple hairpin layers. The multiple slot layers may include six slot layers. The multiple hairpin layers may include six hairpin layers. Thus, at least one of the hairpin layers may be “shared” by two winding sets.

TECHNICAL FIELD

The disclosure relates generally to a stator assembly in an electric machine, and more particularly, to the winding configuration in a bar-wound stator assembly.

BACKGROUND

An electric machine includes a rotor assembly that is rotatable relative to a stator assembly. The stator assembly generally includes a plurality of stator windings inserted into slots in the stator assembly. A bar wound stator assembly is sometimes employed in electric machines to improve machine thermal and overall performance. The number of turns or windings in a bar-wound stator assembly may generally only be changed in discrete steps corresponding to specific configurations.

SUMMARY

A stator assembly includes a plurality of stator slots defining multiple slot layers. The assembly includes a plurality of conductors or hairpins each having a respective first leg positioned in one of the multiple slot layers and a respective second leg positioned in another of the multiple slot layers. For bar wound construction, the conductor is typically referred to as a “hairpin” by those skilled in the art and will be referred to as such in this description. The plurality of hairpins is divided into multiple hairpin layers. Each of the hairpins (the term “hairpins” is intended to refer to “the plurality of hairpins”) is configured to allow a current flow from the respective first leg to the respective second leg.

The hairpins form multiple winding sets, such as first, second, third and fourth winding sets. Each of the winding sets at least partially includes the hairpins from at least two of the multiple hairpin layers. The multiple slot layers may include first, second, third, fourth, fifth and sixth slot layers. The multiple hairpin layers may include first, second, third, fourth, fifth and sixth hairpin layers. Thus, at least one of the hairpin layers may be “shared” by two winding sets. This stator winding arrangement improves the flexibility of the bar-wound stator assembly by allowing for additional turn counts or additional configurations.

In a first embodiment, the first winding set includes a combination of hairpins from the first and third hairpin layers. The second winding set includes a combination of hairpins from the second and fourth hairpin layers. The third winding set includes a combination of hairpins from the fifth and third hairpin layers. The fourth winding set includes a combination of hairpins from the sixth and fourth hairpin layers. Thus, in the first embodiment, the third hairpin layer may be shared by the first and third winding sets and the fourth hairpin layer may be shared by the second and fourth winding sets.

In one example, the first winding set may include 12 hairpins from the first hairpin layer connected in series with 6 hairpins from the third hairpin layer. The second winding set may include 12 hairpins from the second hairpin layer connected in series with 6 hairpins from the fourth hairpin layer. The third winding set may include 12 hairpins from the fifth hairpin layer connected in series with 6 hairpins from the third hairpin layer. The fourth winding set may include 12 hairpins from the sixth hairpin layer connected in series with 6 hairpins from the fourth hairpin layer.

The first hairpin layer may be defined by hairpins with the respective first leg in the first slot layer and the respective second leg in the second slot layer. The second hairpin layer may be defined by the hairpins with the respective first leg in the second slot layer and the respective second leg in the first slot layer. The third hairpin layer may be defined by the hairpins with the respective first leg in the third slot layer and the respective second leg in the fourth slot layer. The fourth hairpin layer may be defined by the hairpins with the respective first leg in the fourth slot layer and the respective second leg in the third slot layer. The fifth hairpin layer may be defined by the hairpins with the respective first leg in the fifth slot layer and the respective second leg in the sixth slot layer. The sixth hairpin layer may be defined by the hairpins with the respective first leg in the sixth slot layer and the respective second leg in the fifth slot layer.

Each of the hairpins may be a short-pitched coil or a full-pitched coil. The short-pitched and full-pitched coils are configured to extend over a first and second number of the plurality of stator slots, respectively, such that the first number is less than the second number. In one example, the first and second numbers are 8 and 9. In the first embodiment, the third and fourth hairpin layers may include more of the short-pitched coils than any of the first, second, fifth and sixth hairpin layers. For example, the third and fourth hairpin layers may each include at least four short-pitched coils while the first, second, fifth and sixth hairpin layers may each include at least two short pitched coils.

Each of the first, second, third and fourth winding sets may define an identical number of multiple phases. In one embodiment, the multiple phases is exactly three phases; the plurality of stator slots includes exactly 72 slots; and the stator defines 8 poles.

In a second embodiment, the first and second winding sets each include a combination of the plurality of hairpins from the first, third and fifth hairpin layers. The third and fourth winding sets each include a combination of the plurality of hairpins from the second, fourth and sixth hairpin layers. In the second embodiment, the first and second winding sets may each include six of the plurality of hairpins from each of the first, third and fifth hairpin layers. The third and fourth winding sets may each include six of the plurality of hairpins from each of the second, fourth and sixth hairpin layers.

In the second embodiment, the first, second, third, fourth, fifth and sixth hairpin layers each may include the same number of short-pitched coils. For example, each of the first through sixth hairpin layers may include at least four short-pitched coils. An electric machine may include the stator assembly described above.

DETAILED DESCRIPTION

Referring to the Figures, wherein like reference numbers refer to the same or similar components throughout the several views,FIG. 1is a schematic fragmentary sectional view of an electric motor/generator or electric fraction machine, referred to herein as electric machine10. The electric machine10may be employed in a vehicle12. The vehicle12may be any passenger or commercial automobile such as a hybrid electric vehicle including a plug-in hybrid electric vehicle, an extended range electric vehicle, or other vehicles. The electric machine10may include any device configured to generate an electric machine torque by, for example, converting electrical energy into rotational motion. For instance, the electric machine10may be configured to receive electrical energy from a power source, such as a battery array (not shown). The power source may be configured to store and output electrical energy. The vehicle12may include an inverter (not shown) for converting the DC voltage from the battery array into alternating current (AC) voltage. The electric machine10may be configured to use the AC voltage from the inverter to generate rotational motion. The electric machine10may be further configured to generate electrical energy when provided with mechanical energy, such as the mechanical energy (torque) of an engine.

Referring toFIG. 1, the electric machine10includes a rotor assembly14and a stator assembly16. The rotor assembly14is rotatable relative to and within the stator assembly16about a longitudinal axis18(extending out of the page inFIG. 1). The rotor assembly14may be annularly-shaped and positioned around a shaft (not shown). The rotor assembly14may be of any type known to those skilled in the art, including but not limited to, an interior permanent magnet, a surface permanent magnet, an induction, synchronous, reluctance or a separately-excited/wound-field rotor. The specific configuration of the rotor assembly14is not shown inFIG. 1.

Referring toFIG. 1, the stator assembly16includes a plurality of stator slots20extending away from a stator core21. The stator slots20may extend lengthwise along the longitudinal axis18and may be evenly spaced from each other radially about the longitudinal axis18. The stator assembly16may include any number of slots or poles suitable to the application at hand. In one example, the number of stator slots20is exactly 72 (FIG. 1is intended as a schematic illustration only) and the stator assembly16defines 8 poles.

FIG. 2is a schematic fragmentary sectional view of the stator assembly16. In the embodiment shown, the stator assembly16includes 72 slots.FIG. 2shows stator slot numbers S11 through S31. The plurality of stator slots20may define multiple slot layers, such as first, second, third, fourth, fifth and sixth slot layers22A, B, C, D, E and F, shown inFIG. 2. The first slot layer22A is farthest from the outer diameter23of the stator core21and the sixth slot layer22F is closest to the outer diameter23of the stator core21. However, it should be appreciated that each stator slot20may include a different number of layers, including but not limited to, four layers or eight layers. Referring toFIGS. 1-2, the stator slots20may be partially open slots or closed slots.

Referring toFIGS. 1-2, the stator assembly16includes a plurality of conductors or hairpins24. For bar wound construction, the conductor is typically referred to as a “hairpin” by those skilled in the art and will be referred to as such in this description.FIG. 3is a schematic diagram of two types of conductors or hairpins24that may be employed in the stator assembly16. It is understood that the hairpins24shown inFIG. 3are only schematic, and are not meant to represent the scale or specific shape of the hairpins24as is known to those skilled in the art. Referring toFIGS. 1-2, the hairpins24may include a substantially rectangular cross-section. However, any other cross-sectional shape may be employed.

Referring toFIG. 3, the hairpins24are segmented and include a respective first leg26, a respective second leg28and a respective bent end portion30between the respective first and second legs26,28. The hairpins24are configured to allow a current to flow from the respective first leg26to the respective second leg28. Referring toFIG. 3, after being inserted into the stator slot20, the ends32of the hairpins24are bent outward to enable connections between respective hairpins24by welding.

Referring toFIG. 3, two types of hairpins24are shown: a short-pitched coil34and a full-pitched coil38. Referring toFIG. 3, the short-pitched coil34has a first span40and the full-pitched coil38has a second span44. The span of the hairpin24may be defined as the angular distance between stator slots20through which a single hairpin24is positioned. As shown inFIG. 3, the second span44is greater than the first span40. Stated differently, each hairpin24spans a pre-determined number of stator slots20. The short-pitched and full-pitched coils34,38are configured to extend over a first and second number of the plurality of stator slots20, respectively, the first number being less than the second number. In one example, the first and second numbers are 8 and 9.

Referring toFIGS. 1-2, a stator slot liner52may be inserted within the stator slots20to electrically isolate the hairpins24from the stator core21and from one another. The hairpins24must be electrically isolated from the stator core to prevent phase to ground shorts and electrically isolated from one another to prevent phase to phase shorts from occurring. The hairpins24may be coated with enamel, with the slot liner52providing extra protection. In the embodiment shown, the stator slots20are partially open slots and the hairpins24and the stator slot liner52may be axially or radially inserted. However, the stator slots20may also be closed slots and the hairpins24and the slot liner52may be radially inserted.

Referring now toFIG. 2, the hairpins24each have their respective first leg26inserted into one of the first, second, third, fourth, fifth and sixth slot layers22A-F and their respective second leg28inserted into another of the first, second, third, fourth, fifth and sixth slot layers22A-F. The hairpins24may be divided into multiple hairpin layers, such as first, second, third, fourth, fifth and sixth hairpin layers54A-F, shown inFIG. 2(andFIGS. 4-5). The lines inFIG. 2representing hairpin layers54A-F are only schematic, and are not meant to represent the scale or specific shape of the hairpins24as is known to those skilled in the art.

Referring toFIG. 2, the first hairpin layer54A (forward winding from first to second slot layer22A to22B) is formed by the plurality of hairpins24having their first leg26A in the first slot layer22A (e.g. in slot S21) and their second leg28A in the second slot layer22B (e.g. in slot S30). In other words, the first hairpin layer54A is the forward winding from the first to second slot layers22A to22B. Referring toFIG. 2, the second hairpin layer54B is defined by the plurality of hairpins24having their first leg26B in the second slot layer22B (e.g. in slot S21) and their second leg28B in the first slot layer22A (e.g. in slot S12). In other words, the second hairpin layer54B is the reverse winding from the second to first slot layers22B to22A.

Referring toFIG. 2, the third hairpin layer54C is defined by the plurality of hairpins24with their first leg26C in the third slot layer22C (e.g. in slot S21) and their second leg28C in the fourth slot layer22D (e.g. in slot S30). In other words, the third hairpin layer54C is the forward winding from the third to fourth slot layers22C to22D. Referring toFIG. 2, the fourth hairpin layer54D is defined by the plurality of hairpins24with their first leg26D in the fourth slot layer22D (e.g. in slot S21) and their second leg28D in the third slot layer22C (e.g. in slot S12). In other words, the fourth hairpin layer54D is the reverse winding from the fourth to third slot layers22D to22C.

Referring toFIG. 2, the fifth hairpin layer54E is defined by the plurality of hairpins24with their first leg26E in the fifth slot layer22E (e.g. in slot S21) and their second leg28E in the sixth slot layer22F (e.g. in slot S30). In other words, the fifth hairpin layer54E is the forward winding from the fifth to sixth slot layers22E to22F. Referring toFIG. 2, the sixth hairpin layer54F is defined by the plurality of hairpins24with their first leg26F in the sixth slot layer22F (e.g. in slot S21) and their second leg28F in the fifth slot layer22E (e.g. in slot S12). In other words, the sixth hairpin layer54F is the reverse winding from the sixth to fifth slot layers22F to22E.

FIG. 4is a schematic diagram of a first embodiment of the electrical connections60of the stator assembly16. The hairpins24form multiple winding sets, such as first, second, third, and fourth winding sets61,62,63,64(shown inFIG. 4) within the stator slots20(shown inFIGS. 1-2). However, any number of winding sets may be configured according to the particular application at hand. The first through fourth winding sets61-64may be connected in series or in parallel. The first through fourth winding sets61-64may define an identical number of multiple phases. In one embodiment, each winding set defines a “U” phase, a “V” phase and a “W” phase. In another embodiment, each winding set defines five phases, i.e., the winding set defines a “U” phase, a “V” phase, an “X” phase, a “Y” phase and a “Z” phase. However, the electric machine10is not limited to a three or five phase machine, and the number of phases may differ from the phases described herein.

As shown inFIG. 4, the first, second, third and fourth winding sets61-64may be parallel to one another. Each of the first, second, third and fourth winding sets61-64include a different plurality of hairpins24connected in series.

FIG. 5is a schematic diagram of a winding layout100for the first through sixth hairpin layers54A-F, corresponding to the connections shown inFIG. 4.FIG. 5represents a stator assembly16with 72 slots. The slot numbers are bracketed on the right by the letter “S” (such that numbers 1 through 72 refer to slots S1 through S72).FIG. 5shows all the stator slots (S1-72) with the right side of the figure wrapping over or joining the left side of the figure. The letter “N” inFIG. 4refers to the neutral connection while U, V and W refer to the three phases. While the winding layout100inFIG. 5is shown for phase U, the layouts for phases V and W are similar. Other alternative configurations may be made, for example, a “Y” configuration without a common neutral or a Delta connection, as known to those skilled in the art.

The first winding set61includes a combination of hairpins24from the first and third hairpin layers54A,C. Referring toFIGS. 4-5, the first winding set61includes a first coil set66from the first hairpin layer54A and a second coil set68from the third hairpin layer54C. The first and second coil sets66,68are connected in series through a first jumper84. Referring toFIG. 5, the first coil set66may include twelve hairpins (see hairpins70,71,72,73,74,75,76,77,78,79,80,81and82) and the second coil set68may include six hairpins (hairpins85,86,87,88,89,90). As shown inFIG. 5, turn82of the first coil set66is connected via the first jumper84to turn85of the second coil set68.FIGS. 4-5show the start cable92and end cable93interconnecting the ends of the first winding set61.

The second winding set62includes a combination of hairpins24from the second and fourth hairpin layers54B,D. Referring toFIGS. 4-5, the second winding set62includes a third coil set94from the second hairpin layer54B and a fourth coil set96from the fourth hairpin layer54D. The third and fourth coil sets94,96are connected in series through a second jumper98.FIG. 4shows the start cable101and end cable99interconnecting the ends of the second winding set62.

The third winding set63includes a combination of hairpins24from the fifth and third hairpin layers54E,C. Referring toFIGS. 4-5, the third winding set63includes a fifth coil set102from the fifth hairpin layer54E and a sixth coil set104from the third hairpin layer54C. The fifth and sixth coil sets102,104are connected in series through a third jumper106.

The fourth winding set64includes a combination of hairpins24from the sixth and fourth hairpin layers54F,D. Referring toFIGS. 4-5, the fourth winding set64includes a seventh coil set108from the sixth hairpin layer54F and an eighth coil set110from the fourth hairpin layer54D. The seventh and eighth coil sets108,110are connected in series through a fourth jumper112. Referring toFIGS. 4-5, the first, third, fifth and seventh coil sets66,94,102,108each include twelve hairpins and the second, fourth, sixth, and eighth coil sets68,96,104,110each include six hairpins.

Referring toFIG. 5, the third hairpin layer54C is shared by the first and third winding sets61,63. The fourth hairpin layer54D is shared by the second and fourth winding sets62,64. The sharing of hairpins24from the third and fourth hairpin layers54C-D may accommodate asymmetry between rotor pole or stator tooth tips (not shown). The winding layout100is configured such that no voltage potential exists between parallel connections.

The first, second, third, fourth, fifth and sixth hairpin layers54A-F (shown inFIG. 2) each include a combination of short-pitched and full-pitched coils34,38(shown inFIG. 3). As noted previously, the short-pitched and full-pitched coils34,38are configured to extend over a first and second number of the plurality of stator slots20, respectively, the first number being less than the second number.

In the first embodiment, the third and fourth hairpin layers54C,54D may include more of the short-pitched coils34than any of the first, second, fifth and sixth hairpin layers54A, B, E, F. Referring toFIG. 5, the first, second, fifth and sixth hairpin layers54A, B, E, F may each include at least two short-pitched hairpins, such as first and second short-pitched hairpins114,116. In the embodiment shown, the first and second short-pitched hairpins114,116each span 8 slots, from slots S11 to S19 and slots S12 to S20, respectively. Referring toFIG. 5, the third and fourth hairpin layers54C and54D may each include at least four short-pitched hairpins, such as third, fourth, fifth and sixth short-pitched hairpins118,120,122,124. In the embodiment shown, the third through sixth short-pitched hairpins118,120,122,124each span 8 slots, from slots S11-S19, S12-S20 and S47-S55, S48-S56 (layer54C), and S56-S64, S57-S65, and S20-S28, S21-S29 (layer54D), respectively.

FIG. 6is a schematic diagram of a second embodiment of the electrical connections160that may be employed in the stator assembly16ofFIG. 1. As shown inFIG. 6, the first, second, third and fourth winding sets161,162,163and164are parallel to one another. Each of the first, second, third and fourth winding sets161-164include a different plurality of hairpins24connected in series.

In the second embodiment, the first and second winding sets161,162both may include a combination of hairpins24from any of the six hairpin layers54A-F, for example it may include a combination of hairpins24from the first, third and fifth hairpin layers54A, C, E or a combination from other hairpin layers. Referring toFIG. 6, the first winding set161includes first, second and third coil sets166,168,170(connected in series through respective jumpers192) from the first, third and fifth hairpin layers54A, C, E, respectively. Referring toFIG. 6, the second winding set162includes fourth, fifth and sixth coil sets174,176,178(connected in series through respective jumpers192) from the first, third and fifth hairpin layers54A, C, E, respectively. Each of the first through sixth coil sets166,168,170,174,176,178may include six hairpins24each. In other words, the first and second winding sets161,162may each include six hairpins24from each of the first, third and fifth hairpin layers54A, C, E.

The third and fourth winding sets163,164both may include a combination of hairpins24from any of the six hairpin layers54A-F, for example it may include a combination of hairpins24from the second, fourth and sixth hairpin layers54B, D, F. Referring toFIG. 6, the third winding set163includes seventh, eighth and ninth coil sets180,182,184(connected in series through respective jumpers192) from the second, fourth and sixth hairpin layers54B, D, F, respectively. Referring toFIG. 6, the fourth winding set164includes tenth, eleventh and twelfth coil sets186,188,190(connected in series through respective jumpers192) from the second, fourth and sixth hairpin layers54B, D, F, respectively. Each of the sixth through twelfth coil sets180,182,184,186,188,190may include six hairpins24each. In other words, the third and fourth winding sets163,164may each include six hairpins24from each of the second, fourth and sixth hairpin layers54B, D, F.

Thus, in the second embodiment, the first, third and fifth hairpin layers54A, C, E may be shared by the first and second winding sets161,162while the second, fourth and sixth hairpin layers54B, D, F may be shared by the third and fourth winding sets163,164. The windings inFIG. 6are connected in a delta configuration but alternatively those may be connected in a Y configuration as inFIG. 4.

The configurations outlined above allow for greater flexibility in designing an electric machine10with a particular torque or system voltage requirement. Arbitrarily specifying a configuration for an electric machine10will not produce the required torque output or meet minimum noise requirements. Only specific configurations with a particular number of slots, number of phases, number of poles, number of winding sets, configuration of hairpin layers54A-F (relative to the slot layers22A-F) etc. will produce the desired functionality. These specific configurations cannot readily be determined by inspection. If an arrangement is not selected correctly, the design will either perform poorly or will not meet the functional requirements. Because of the large number of possible combinations, the workable configurations are neither easily determined nor obvious.