EP4725097A1

EP4725097A1 - Stator segment, electrical machine and wind turbine

Info

Publication number: EP4725097A1
Application number: EP25713946.9A
Authority: EP
Inventors: Ziad Azar; Ravindra Bhide; Alexander Duke; Xing Li
Original assignee: Siemens Gamesa Renewable Energy AS
Current assignee: Siemens Gamesa Renewable Energy AS
Priority date: 2024-08-23
Filing date: 2025-03-26
Publication date: 2026-04-15
Also published as: EP4701045A1; WO2026041250A1; CN121925772A

Abstract

It is described a Stator segment (101a,b,c) for an electrical machine (100), in particular permanent magnet synchronous electrical generator, comprising: a core ring portion (106a,b,c) extending in a circumferential direction (cd) forming less than a whole circumference; plural first teeth (107a,b,c) extending radially from the ring portion (106a,b,c); two second teeth (108a,b,c) extending radially from the ring portion (106a,b,c) and being arranged at two circumferential ends of the ring portion; wherein between each of two adjacent first teeth (107a,b,c) a first slot (109a,b,c) is formed, wherein between each of the second teeth (108a,b,c) and an adjacent first tooth (107a,b,c) a second slot (110a,b,c) is formed, the stator segment further comprising: a multiple phase winding set (105A,B,C) wound according to a concentrated winding topology.

Description

202301179

1

DESCRIPTION

Stator Segment , Electrical Machine and Wind Turbine

Field of invention

The present invention relates to a stator segment for an electrical machine , relates further to an electrical machine comprising plural stator segments and still further relates to a wind turbine comprising the electrical generator .

Art Background

Conventionally, a stator may be assembled from plural stator segments each spanning a portion of a whole circumference . Conventionally, the stator segments have exposed end coils , i . e . coils which are exposed to air at the segment circumferential ends instead of enclosed in slots .

Exposed end coils suf fer from unreliable mechanical performances during transportation, assembly and operation . One of the critical consequences is that two facing end coils of two neighbouring segments may scrape each other under electromagnetic forces , thermal deformation and vibrations . Without reliable fixation this may cause insulation damage leading to the requirement of generator exchange .

One conventional straightforward solution is to increase the segment-to-segment gap to avoid contact or touch of neighbouring segments . This however may increase the 2 f torque harmonic and most importantly does not eliminate the risk of damage due to scraping of two end coils from the adj acent segments . To fix the exposed end coils mechanical fixation solutions ( for example using straps , clamps , bolds , etc . ) may not be the optimum solution in terms of enhanced li fetime and reliability . 202301179

2

One other conventional method is to remove the end coils which makes the first and the last slot of each segment coil- free which however largely reduces the output power and increases unwanted harmonics . Further conventionally, singlelayer concentrated-winding topology has been employed which does not have exposed end coils and can be easily modulari zed or segmented . The disadvantages include higher harmonics , lower torque and hence an ef ficiency reduction .

Thus , there may be a need for a stator segment for an electrical machine , there may be a need for an electrical machine and there may be a need for a wind turbine , wherein the above sketched disadvantages are reduced or even avoided .

Summary of the Invention

This need may be met by the subj ect matter according to the independent claims . Advantageous embodiments of the present invention are described by the dependent claims .

According to an embodiment of the present invention it is provided a stator segment for an electrical machine , in particular permanent magnet synchronous electrical generator, comprising : a core ring portion extending in a circumferential direction forming less than a whole circumference ; plural first teeth extending radially from the ring portion; two second teeth extending radially from the ring portion and being arranged at two circumferential ends of the ring portion; wherein between each of two adj acent first teeth a first slot is formed, wherein between each of the second teeth and an adj acent first tooth a second slot is formed, the stator segment further comprising : a multiple phase winding set wound according to a concentrated winding topology .

The stator segment may be manufactured from ( layers of ) ferromagnetic material with high magnetic permeability . The diameter of the assembled stator may be between 5 m and 15 m . The electrical generator may be a wind turbine electrical 202301179

3 generator driven by a rotation shaft at which plural rotor blades are mounted .

The core ring portion may be a segment or section of a ring and in particular a section of a circular ring . According to di f ferent embodiments , the core ring portion may span di f ferent amounts of an angular range being less or equal than 180 ° . Thus , the entire stator may be assembled from two , three , four, five , six, ... eighteen and more stator segments .

Each stator segment may be provided with its own ( individual ) associated winding set in particular multiple phase winding set . The core ring portion and the first teeth and/or the second teeth may be integrally formed in particular in layers of magnetically permeable material . The first and/or second teeth may extend radially inwards or outwards from the core ring portion .

The two second (hal f ) teeth may limit the stator segment at the two circumferential ends . Thus , the two second teeth may therefore protect any wire portions which may be provided within the second slots . Thereby protection of wire portion from damage may be improved .

Any first slot is formed between two circumferentially immediately adj acent first teeth . Any second slot is formed or limited at one circumferential side by a first tooth and at another circumferential side by a second tooth . The slot width of the first slot may substantially be equal to the slot width of the second slot or may have a di f ferent si ze depending on the application .

The first teeth and the second (hal f ) teeth may be configured in a similar manner but the second (hal f ) tooth may have a smaller circumferential width than the first tooth . In the assembled stator one second tooth of a first stator segment may be close or may even contact a second tooth of a second segment . Between neighbouring stator segments a small gap may 202301179

4 be provided to avoid direct or immediate contact of the corresponding second teeth . Two neighbouring stator segments may for example be mounted or coupled to each other by bolts . Other mounting or coupling methods are possible alternatively or additionally .

The second hal f teeth may also be referred to as " end-hal f- teeth" , since they are provided at circumferential ends of the respective stator segments and have typically a circumferential width which is substantially smaller than the circumferential width of the first teeth . The assisting end- hal f-tooth or in general the second tooth at each segment circumferential end may enclose the end coil in the ( second) slot . In an electrical machine assembled from multiple stator segments , two second hal f teeth of di f ferent , adj acent stator segments come in close distance or even touch each other in order to form a ( single ) second full tooth .

In concentrated winding topology all the turns of the wires (wound around one tooth) may have the same magnetic axes . According to the concentrated winding topology, the formed coils are concentric in particular concentric with respect to the first teeth .

The number of phases may for example amount to two , three , four, five , six, seven, or even a higher number of phases . For three phases , for example the winding set may comprise three wires which may be connected according to a starconnection or delta-connection . Preferably, in a segmented stator design, a star-connection has three phases which are connected to the central neutral point of a stator segment . The neutral points of the di f ferent stator segments are connected to each other via electrical connections , e . g . bus bars .

The stator segment may be transported and assembled with reduced risk of damaging end coils due to the second teeth which protect end coils from damage . 202301179

According to an embodiment of the present invention, the multiple phase winding set comprises for each phase a wire , wherein each wire is wound, in particular in one or more turns , around at least one of the first teeth to form at least one coil such that in each of the first slots two hal fcoils are present .

Each wire may be wound in several turns around at least one , in particular around several of the first teeth, to form at each first teeth around which the wire is wound, a coil . In each of the first slots thereby a hal f-coil being wound around a neighbouring first tooth and another hal f-coil wound another neighbouring first tooth may be present . Thereby, a double-layer configuration may be formed . In each of the second slots only one hal f-coil may be present such that in each of the second slots there is no double-layer configuration .

According to an embodiment of the present invention, the two hal f coils in each of the first slots are formed by portions of two wires associated with one phase or by portions of two wires being associated with two di f ferent phases .

Thereby, a great flexibility for the winding may be provided .

According to an embodiment of the present invention, in each of the first slots a double-layer design of wire portions is provided, wherein wire portions belonging to di f ferent hal fcoils in any one first slot are arranged circumferentially and/or radially adj acent .

In each of the second slots a double-layer design of wire portion is not present . In each of the second slots only one hal f-coil of a coil wound around the adj acent first teeth is present .

According to an embodiment of the present invention, the multiple wires are wound around the first teeth but not wound 202301179

6 around the second teeth in order to form coils such that in each of the first slots, two half-coils are present.

According to an embodiment of the present invention, none of the wires of the winding set is wound around any of the second teeth. Thus, any of the second teeth is free or void of any coil. Also, no coil is wound around two immediately adjacent second teeth in the assembled state of the entire stator .

According to an embodiment of the present invention, each of the second teeth has a circumferential extent being smaller or larger than or equal to a circumferential extent of any of the first teeth, and/or wherein each of the second teeth has a radial extent being substantially equal to a radial extent of any of the first teeth.

The circumferential extent of the second teeth may for example amount to between 10% and 70% of the circumferential extent of the first tooth. Thereby, weight can be reduced.

According to an embodiment of the present invention, the plural first teeth and second teeth extend radially outwards from the ring portion, and/or wherein the ring portion spans in the circumferential direction 180°, 120°, 90°, 72°, 60°, 45°, 40°, 36°, 30°, 24°, 22.5°, 20°, 18°, 15°, 12°, 10° or between 180° and 5° of a 360 ° -circumference .

Thereby a great flexibility is provided so enabling to meet requirements of transportation equipment and opportunities.

According to an embodiment of the present invention, it is provided an electrical machine, in particular permanent magnet synchronous generator, comprising: plural stator segments according to one of the preceding embodiments, assembled to form a whole circumference; a rotor, in particular outer rotor, rotatably mounted with respect to the stator and having plural permanent magnets mounted at different circumferential 202301179

7 positions forming plural magnet poles , the plural stator segments having winding sets with concentrated winding topology . The winding sets are electrically connected such that winding sets of adj acent stator segments are phase shi fted relative to each other, wherein there are at least three groups of stator segments , wherein all winding sets of one group of stator segments are not phase-shi fted relative to each other, wherein winding sets of di f ferent groups of stator segments are phase-shi fted relative to each other .

The plural stator segments may be mounted to each other such that the assembled and mounted plural stator segments form a ring across a whole circumference . Thereby the respective second (hal f ) teeth of the stator segments may contact each other or may be in close proximity to each other being a small gap in-between . Two adj acent second hal f teeth form a full tooth, also called second full tooth/teeth .

The rotor may be an inner rotor or an outer rotor . Preferably the first teeth and second teeth extend radially outwards and the rotor is an outer rotor . The winding sets provided at the di f ferent stator segments may be physically the equal or identical or not distinguishable , but may electrically provide a di f ferent sequence of electrical phases . The respective winding sets of the di f ferent stator segments are electrically not connected to each other, but may each be connected separately to an associated converter .

2* AQs is the total number of second teeth, AQs is the total number second full teeth, Nseq is the number of stator segments , wherein AQs = Nseq .

When the above relationship is satis fied, it is ensured that each stator segment comprises at each circumferential end one second tooth for protection of coils .

According to an embodiment of the present invention, the number of di f ferent winding schemes in the plural stator seg- 202301179 ments is equal to the number of phases or a multiple thereof, wherein the number of phases is in particular three.

Tin advantage may be that each phase has the same number of coils which locate in the second slots (i.e. end-coils) , obtaining a balanced or symmetric multi-phase system.

According to an embodiment of the present invention, the number of first teeth Qs plus the number of second full teeth AQs is the total number of teeth of the stator, wherein

2 * p + 2 * Ap is the total number of poles in the electrical machine, wherein p is the number of pole pairs, wherein Ap is the number of added pole pairs, wherein Qs, 2p have a common divider, wherein Qs/ (2*p) is 1.2, wherein p is an integer number, Ap is an integer number, Ap is in particular an even number greater than 1.

Ap may e.g. be 2 or 4 or 6. Ap may be an odd number e.g. 3 or 5. Thereby great flexibility is provided.

In particular, the number of segments (equal to AQs) may be equal to or greater than 12 and/or equal to or smaller than 18.

According to an embodiment of the present invention, ip is the circumferential width or pole pitch of each of the poles, TS is the circumferential width or slot pitch of each of the first slots, tau_p/tau_s (Qs,ps) = tau_p/tau_s (Qs+Delta_Qs, ps+Delta_P) = ip/is = Qs/ (2p) , w_EHT is the width of the second teeth, wherein TS depends on AQs, on w_EHT and on Qs, wherein ip depends on p and Ap.

According to an embodiment of the present invention, the electrical machine is characterized by the following: 202301179

9

Qs=216 and AQs=12 and 2p=180 and 2 *Ap=4 and in particular with three groups of stator segments , or

Qs=216 and AQs=18 and 2p=180 and 2 *Ap=12 and in particular with three groups of stator segments , or

Qs=288 and AQs=12 and 2p=240 and 2 *Ap=8 and in particular with three groups of stator segments , or

Qs=288 and AQs=12 and 2p=240 and 2 *Ap=4 and in particular with six groups of stator segments , or

Qs=288 and AQs=16 and 2p=240 and 2 *Ap=8 and in particular with four groups of stator segments , or

Qs=324 and AQs=18 and 2p=270 and 2 *Ap=6 and in particular with three groups of stator segments , or

Qs=336 and AQs=14 and 2p=280 and 2 *Ap=4 and in particular with seven groups of stator segments , or

Qs=360 and AQs=12 and 2p=300 and 2 *Ap=4 and in particular with three groups of stator segments , or

Qs=360 and AQs=15 and 2p=300 and 2 *Ap=6 and in particular with five groups of stator segments , or

Qs=360 and AQs=15 and 2p=300 and 2 *Ap=10 and in particular with three groups of stator segments , or

Qs=384 and AQs=16 and 2p=320 and 2 *Ap=8 and in particular with four groups of stator segments , or

Qs=432 and AQs=12 and 2p=360 and 2 *Ap=4 and in particular with six groups of stator segments , or

Qs=432 and AQs=12 and 2p=360 and 2 *Ap=8 and in particular with three groups of stator segments , or

Qs=432 and AQs=18 and 2p=360 and 2 *Ap=12 and in particular with three groups of stator segments .

According to an embodiment of the present invention the winding sets of one group of stator segments are connected to one or two converters . Thereby, di f ferent power capacities may be provided .

According to an embodiment of the present invention, it is provided a wind turbine , comprising : a rotation shaft at which plural rotor blade are mounted; an electrical machine according to any of preceding embodiments , the rotor of the 202301179

10 electrical machine being mechanically, in particular directly, e . g . having one to one trans formation ratio ( e . g . without gear box ) , coupled to the rotation shaft .

The aspects defined above and further aspects of the present invention are apparent from the examples of embodiment to be described hereinafter and are explained with reference to the examples of embodiment . The invention will be described in more detail hereinafter with reference to examples of embodiment but to which the invention is not limited .

Brief Description of the Drawings

Embodiments of the present invention are now described with reference to the accompanying drawings . The invention is not restricted to the illustrated or described embodiments .

Fig . 1 schematically illustrates an electrical machine according to an embodiment of the present invention, comprising several stator segments according to an embodiment of the present invention;

Fig . 2 schematically illustrates a stator segment according to another embodiment of the present invention;

Fig . 3 schematically illustrates plural assembled stator segments according to an embodiment of the present invention; and

Fig . 4 schematically illustrates a wind turbine according to an embodiment of the present invention .

Detailed Description

The illustration in the drawings is in schematic form . It is noted that in di f ferent figures , elements similar or identical in structure and/or function are provided with the same reference signs or with reference signs , which di f fer only 202301179

11 within the first digit . A description of an element not described in one embodiment may be taken from a description of this element with respect to another embodiment .

According to embodiments of the present invention, the circumferential end coil-sides of a stator segment are enclosed by merging two teeth/pole combinations ( adding extra slots/pole into original slot/pole combination) . Thereby, the assisting end segment-hal f-teeth can be added with minor influences on the performance , i . e . torque and with the advantage of lower cogging torque and torque ripple . The dimension can be designed to eliminate the influence of segment- to-segment gap .

The electrical machine 100 schematically illustrated in Fig . 1 comprises plural stator segments 101a, 101b, 101c which are assembled to form a whole circumference ( in the circumferential direction cd) and form a stator 103 . The electrical machine 100 further comprises a rotor 102 which is rotatably mounted with respect to the stator 103 ( formed by the assembled stator segments 101a, 101b, 101c ) . The rotor 102 has plural magnets 104 , 105 mounted thereon, wherein each pair 104 , 105 forms a pole pair having alternating pole or magnetic pole configurations , such that the magnet 104 for example provides a north pole at a radially inner end and the magnet 105 provides a south pole at a radially inner end .

In the electrical machine 100 , each of the plural stator segments 101a, 101b, 101c has winding sets 105A, 105B, 105C, for three di f ferent electrical phases A, B, C . In Fig . 1 , the winding topology of the three phase wires are indicated including the indication of the winding sense , meaning running inwards or outwards .

The electrical machine 100 comprises in the illustrated embodiment three stator segments 101a, 101b, 101c having seg- ment-to-segment gap 120 between neighbouring segments . In 202301179

12 other embodiments more or less segments may be provided to form a whole circumference of a stator .

Each stator segment 101a, 101b, 101c comprises a core ring portion 106a, 106b, 106c which extends in the circumferential direction cd forming less than a whole circumference . In the illustrated embodiment , the stator segments form each a 120 ° segment of a 360 ° circumference . Each stator segment comprises plural first teeth 107a, 107b, 107c which extend radially (outwards ) from the respective ring portion 106a, 106b, 106c . Each of the stator segments 101a, 101b, 101c further comprises two second (hal f ) teeth 108a, 108b, 108c, respectively, which also extend radially ( outwards ) from the ring portion 106a, 106b, 106c and being arranged at two circumferential ends of the respective ring portion or the stator segment 101a, 101b, 101c .

Thereby, between each of two adj acent first teeth ( for example teeth 107a ) a first slot 109a is formed . Similarly between any two first teeth 107b of the second stator segment 101b, the first slot 109b is formed . The same holds for the third segment 101c . Further, between each of the second (hal f ) teeth 108a and an adj acent first tooth 107a, a second slot 110a is formed .

The multiple phase winding set 105A, 105B, 105C is wound across the assembled stator according to a concentrated winding topology . The multiple phase winding set comprises for each phase , for example A, B, C, a wire ( electrical conductor ) would around several teeth . For example for phase A, the wire 105A is provided . This wire 105A is wound around at least one of the first teeth 107a to form at least one coil , for example the coil 111A as illustrated in Fig . 1 formed by winding the wire 105A. Thereby, in each of the first slots 109a two hal f-coils (belonging to same or di f ferent phases ) are present . 202301179

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The two half-coils in each of the first slots 109a are formed by portions of two wires associated with one phase or by portions of two wires being associated with two different phases, or by portions of two wires associated with one system or by portions of two wires being associated with two different systems. For example in the first slot labelled 109a' wire portions both belonging to the phase A are provided. In contrast at the first slot 109a" one half-coil belongs to the phase A and the other half-coil belongs to the phase C.

In each of the first slots 109a, b, c, a double-layer design of wire portion is provided, wherein wire portions belonging to different half-coils are arranged circumferentially and/or radially adjacent. In the illustrated embodiment, the wire portions in one of the first slots 109a, b, c are arranged circumferentially adjacent (side-by-side) . In other embodiments the different half-coils may be arranged radially adjacent to each other (also referred to as arrangement on top of each other) .

As can be appreciated from Fig. 1, none of the wires 105A, 105B, 105C is wound around any of the second teeth 108a, b, c.

As can also be appreciated from Fig. 1, each of the second (half) teeth 108a, b, c has a circumferential extent c2 which is smaller than a circumferential extent cl of the first teeth 107a, b, c. The radial extent of the second and first teeth may be substantially similar or the same. In other embodiments, the respective stator segments may span a different angle range than the angle range as illustrated.

The total number of second (half) teeth 108a, b, c is in the illustrated embodiment 6 and the number of segments is 3. Thus, the equation AQs=Nseq holds, wherein 2xAQs is the total number of second (half) teeth 108a, b, c and Nseq is the number of stator segments. AQs is the total number of second 202301179

14 full teeth of the electrical machine, each second full tooth formed by two adjacent second half teeth.

As can be taken from the different shadings used for the different phases in different running direction, the windings in the different segments are not according to a same topology but are phase-shifted relative to each other. It should be appreciated that each of the stator segments 101a, b, c comprises its own multiple phase winding set. Only one winding set, namely the winding set 105A, B, C is labelled in Fig. 1.

A concentrated winding generator according to an embodiment of the present invention may be characterized by a tooth/pole (or slot/pole) combination, namely the ratio of Qs/2p (Qs is the number of teeth or slots, 2p is the number of poles (2p is also written as 2*p, p is the number of pole pairs) , which is usually described by the minimum tooth/pole (or slot/pole) number of a module machine if Qs/2p have a common divider. For example, for Qs=144, 2p=120, the tooth/pole (or slot/pole) combination is 12/10. For concentrated winding generators, this combination is typically close to 1. The following combinations Qs/2p are possible according to embodiments of the present invention or which may serve as starting points for embodiments of the present invention: 12/10, 12/14, 24/22, 18/14, 18/16, 18/20, 18/22, 24/20, 24/26, 27/22, 27/24, 27/26, 30/26 etc. In general, the relation Qs/2p is in the range between 0.86 and 1.29, preferably 1.2. For large generators despite high numbers of slots and poles, the combination may remain the same as small generators.

One example of a slot/pole number, to which the invention is not limited to, would be 18 multiplied by a 12/10 slot/pole combination would give 216 slots (Qs=216) and 180 poles (2p=180) as a baseline machine. The slot/pole relation is 1.2. This machine could be split into 12 segments (AQs=12) . According to an embodiment of the present invention, to each segment an additional half tooth to both circumferential ends is added, i.e. there are 24 half teeth added (or 12 full 202301179

15 teeth added) which results in Qs=12. In order to keep a harmonic behaviour of this machine in regard to torque ripple which is similar as the baseline machine, a number of poles have to be added to the pole number of the baseline machine. In this case, 2 or 4 poles are added to the rotor. So, this would give a total slot/pole number of 228/182 or 228/184.

For large generators with conventional double-layer concentrated winding design, the circumferential end coil-sides of each stator segment are exposed to air. According to embodiments of the present invention it is proposed to enclose the circumferential end coil-sides in slots by adding extra "end- half-tooth" (also referred to as "second (half) tooth") at each circumferential end of the segments and meanwhile having extra pole(s) (optionally) . The number of added "half-teeth" may be defined to be 2xAQs . The number of added poles is defined to be 2xAp. They are determined based on the original combination of Qs/2p. The width of added end-half tooth and the winding scheme should also be adapted to have good performances .

1) Number of added full teeth

The number of added half-teeth is defined to be 2xAQs . Two facing end-half-teeth of two neighbouring segments are regarded as one "full" tooth here. Therefore, AQs is the number of added "full" teeth which should be identical to the number of segments Nseg, meaning AQs=Nseg.

2) Number of added poles

The number of added poles is defined to be 2xAp, where Ap is the number of added pole pairs. Theoretically, Ap is an independent variable which may take any integer number. However, it influences the determination of the end-half-tooth width, therefore the constraints as given below may apply.

3) Width of the added end-half-tooth

In order to have enough space for the added end-half-teeth, the other "normal" slots (i.e. the first slots) , and/or teeth 202301179

16

(i.e. first teeth) have to be reduced in width, which means the slot pitch is is reduced. The new is depends on the number of added full teeth AQs as well as the width of added end-half-tooth w_EHT . Simultaneously the pole pitch ip is also reduced due to the added poles. is = TS (QS, AQS, W_EHT) ip = ip (p, Ap) .

For the aim of low harmonics, the width of added end-half teeth should make sure the new combination of ip/is is identical or close to the combination of the original slot and pole number Qs/2p.

Therefore, the following equation (s) may hold: ip/is = Qs/2p or ip/is approximately equals to Qs/2p

4) Winding scheme

Winding scheme has to be adapted after adding new slot/pole combination, i.e. extra teeth and poles. The new winding scheme depends on the phase shift 0 (i.e. angle in electrical degree) in no-load condition between the two neighbouring end coils of two neighbouring segments which should fulfill

0 = 180° * (2p/Qs + 2Ap/AQs) or

0 is approximately equal to: 180° * (2p/Qs + 2Ap/AQs)

Various Ap/ AQs may lead to different winding schemes in each segment, thus different segment types. For the aim of a balanced m-phase system, the number of different segment types (or winding schemes) are recommended to be m or multiple times of m, wherein the numbers of end-coils of each phase are identical. The final determination of the end-half-tooth 202301179

17 width and number of added poles depends on the performance requirements (for example output power, torque ripple, losses, etc.) and manufacturing complexity.

The proposed design method, based on correct selections of Ap, AQs and wEHT will have minor influences on the performances, i.e. torque, compared to the original design.

The original design may refer to any generator design, which has a total slot (or tooth) number identical to the total number of the first teeth of all segments, and a tooth/pole (or slot/pole) combination Qs/2p identical or approximately identical to ip/is, for example but not limited to 12/10, 12/14, 24/22, 18/14, 18/16, 18/20, 18/22, 24/20, 24/26, 27/22, 27/24, 27/26, 30/26 etc. (ip and is are the pole pitch and slot pitch of first slot of a generator with end-tooth design . )

In this manner the skilled person can find the original design (Qs and 2p) by measuring the ip and is of the existing design with end-half-teeth.

It also has the advantage of lower cogging torque and torque ripple, meanwhile, eliminating the influence of segment-to- segment gap .

A conventional generator design with 36 slots/30 poles, 3 segments may be considered. Starting from this conventional generator according to an embodiment of the present invention three teeth (2xAQs=6) and two extra poles (2xAp=2) are added. The winding scheme of the stator has to be also modified to ensure the maximum output power.

Segments will have different winding schemes. In the following Table 1 the winding scheme of the electrical machine illustrated in Fig. 1 is given according to an exemplary proposed design (with end-half-teeth, 30 poles + 2 extra poles, based on 36 slots/30 poles design) . 202301179

Table 1 :

The new winding scheme is determined by the phase-shift angle 0, which is 270° (electrical degrees for the illustrated embodiment) . As can be appreciated from Table 1, the winding scheme in segment 1, segment 2, segment 3 corresponding to segments 101a, 101b, 101c illustrated in Fig. 1, is mutually phase-shifted (and inverted) , but is not equal.

For any given number of phases and given slot/pole combination, following equation regarding winding scheme, the skilled person will generate a corresponding winding scheme with phase-shift.

According to other embodiments of the present invention the electrical machine may characterized by the following: Qs=216 and AQs=12 and 2p=180 and 2*Ap=4 and in particular with three groups of stator segments, or

Qs=216 and AQs=18 and 2p=180 and 2*Ap=12 and in particular with three groups of stator segments, or

Qs=288 and AQs=12 and 2p=240 and 2*Ap=8 and in particular with three groups of stator segments, or

Qs=288 and AQs=12 and 2p=240 and 2*Ap=4 and in particular with six groups of stator segments, or

Qs=288 and AQs=16 and 2p=240 and 2*Ap=8 and in particular with four groups of stator segments, or

Qs=324 and AQs=18 and 2p=270 and 2*Ap=6 and in particular with three groups of stator segments, or 202301179

19

Qs=336 and AQs=14 and 2p=280 and 2*Ap=4 and in particular with seven groups of stator segments, or

Qs=360 and AQs=12 and 2p=300 and 2*Ap=4 and in particular with three groups of stator segments, or

Qs=360 and AQs=15 and 2p=300 and 2*Ap=6 and in particular with five groups of stator segments, or

Qs=360 and AQs=15 and 2p=300 and 2*Ap=10 and in particular with three groups of stator segments, or

Qs=384 and AQs=16 and 2p=320 and 2*Ap=8 and in particular with four groups of stator segments, or

Qs=432 and AQs=12 and 2p=360 and 2*Ap=4 and in particular with six groups of stator segments, or

Qs=432 and AQs=12 and 2p=360 and 2*Ap=8 and in particular with three groups of stator segments, or

Qs=432 and AQs=18 and 2p=360 and 2*Ap=12 and in particular with three groups of stator segments.

Fig. 2 schematically illustrates a stator segment 201a according to another embodiment of the present invention. 12 segments with the same geometries with stator segments 201a are required in order to form a whole circumference of a stator. Also the stator segment 201a has second teeth 208 at circumferential ends and first teeth 207 in-between. In each of first slots 209, a double-layer design is present while in the second slots 210 only a single-layer design is present, meaning only one half-coil is present.

The following Table 2 illustrates the winding scheme for the different segments 1 to 12 (201a, b, c, ...) , one of which is illustrated in Fig. 2, in order to assemble an entire stator 203, as is schematically illustrated in Fig. 3.

The design has 24 end-half-teeth (i.e. AQs=12) , 180 poles (i.e. 2p=180) + 4 extra poles (i.e. 2*Ap=4) , based on 216 slots/180 poles (i.e. Qs=216, 2p=180) design. There are three groups of stator segments. 202301179

20

Table 2 :

In the electrical machine illustrated in Fig. 3, in total 184 poles are present and 228 slots are present.

Advantages of embodiments of the present invention may include to enable a lifetime reliable solution for implementing concentrated winding topology with modularized stator and the direct-drive wind turbines. In addition, the 2f oscillation due to segment-to-segment tolerance gap can be reduced as part of the design.

Compared to the exposed end coils with mechanical fixation solutions (using straps, clamps, bolds, etc.) enclosing the end coils and slots by using end-half-tooth is advantageous in terms of manufacturing difficulty, reliability and lifetime. The potential installation damage of end coils due to mechanical contact is avoided. Compared to the other solutions, the proposed design has lower harmonics and lower influences on the performances. 202301179

21

Fig . 4 schematically illustrates a wind turbine 450 according to an embodiment of the present invention . The wind turbine 450 includes a wind turbine tower 451 on top of which a nacelle 452 is rotatably mounted . The nacelle 452 harbours an electrical machine 400 according to an embodiment of the present invention . A rotation shaft 453 to which plural rotor blades 454 are mounted, is coupled ( directly) to the electrical machine 400 . The electrical machine outputs a three-phase output power which is provided to a ( optional ) converter 455 . The converter converts the AC power stream to a fixed frequency AC power stream and supplies the fixed frequency power stream to a wind turbine trans former 456 . The electrical machine 400 comprises the outer rotor 402 rotating relative to the stator 403 which may be configured similar to the stator 103 illustrated in Fig . 1 .

A single- or multi-stage gearbox could also be present in the wind turbine drivetrain .

It should be noted that the term "comprising" does not exclude other elements or steps and "a" or "an" does not exclude a plurality . Also elements described in association with di f ferent embodiments may be combined . It should also be noted that reference signs in the claims should not be construed as limiting the scope of the claims .

Claims

202301179 22 CLAIMS :

1. Stator segment (101a, b,c) for an electrical machine (100) , in particular permanent magnet synchronous electrical generator, comprising: a core ring portion (106a, b,c) extending in a circumferential direction (cd) forming less than a whole circumference ; plural first teeth (107a, b,c) extending radially from the ring portion (106a, b, c) ; two second teeth (108a, b,c) extending radially from the ring portion (106a, b,c) and being arranged at two circumferential ends of the ring portion; wherein between each of two adjacent first teeth (107a, b,c) a first slot (109a, b,c) is formed, wherein between each of the second teeth (108a, b,c) and an adjacent first tooth (107a, b,c) a second slot (110a, b,c) is formed, the stator segment further comprising: a multiple phase winding set (105A, B,C) wound according to a concentrated winding topology.

2. Stator segment according to the preceding claim, wherein the multiple phase winding set (105A, B,C) comprises for each phase a wire (105A) , wherein each wire is wound, in particular in one or more turns, around at least one of the first teeth (107a) to form at least one coil (111A) such that in each of the first slots (109a' , 109a' ' ) two half-coils are present.

3. Stator segment according to the preceding claim, wherein the two half coils in each of the first slots (109a' , 109a' ' ) are formed by portions of two wires associated with one phase (A, B, C) or by portions of two wires being associated with two different phases (A, B, C) .

4. Stator segment according to one of the preceding claims, wherein in each of the first slots (109a, b,c) a double-layer 202301179

23 design of wire portions is provided, wherein wire portions belonging to different half-coils in any one first slot are arranged circumferentially and/or radially adjacent.

5. Stator segment according to one of the preceding claims, wherein none of the wires (105A,B,C) of the winding set is wound around any of the second teeth (108a, b,c) .

6. Stator segment according to one of the preceding claims, wherein each of the second teeth (108a, b,c) has a circumferential extent being smaller or larger than or equal to a circumferential extent of any of the first teeth (107a, b,c) , and/or wherein each of the second teeth (108a, b,c) has a radial extent being substantially equal to a radial extent of any of the first teeth (107a, b,c) .

7. Stator segment according to one of the preceding claims, wherein the plural first teeth (107a, b,c) and second teeth (108a, b,c) extend radially outwards from the ring portion, and/ or wherein the ring portion spans in the circumferential direction 180°, 120°, 90°, 72°, 60°, 45°, 40°, 36°, 30°, 24°, 22.5°, 20°, 18°, 15°, 12°, 10° or between 180° and 5° of a 360° -circumference .

8. Electrical machine (100) , in particular a permanent magnet synchronous generator, comprising: plural stator segments (101a, b,c) according to one of the preceding claims, assembled to form a whole circumference, a rotor (102) , in particular outer rotor, rotatably mounted with respect to the stator (103) and having plural permanent magnets (104, 105) mounted at different circumferential positions forming plural magnet poles, the plural stator segments (101a, b,c) having winding sets with concentrated winding topology, 202301179

24 wherein the winding sets are electrically connected such that winding sets of adjacent stator segments are phase shifted relative to each other, wherein there are at least three groups of stator segments, wherein all winding sets of one group of stator segments are not phase-shifted relative to each other, wherein winding sets of different groups of stator segments are phase-shifted relative to each other.

9. Electrical machine according to the preceding claim, wherein 2* AQs is the total number of second half teeth, wherein AQs is the total number of second full teeth, i.e each second full tooth being combined by two second half teeth, wherein

Nseq is the number of stator segments, wherein AQs = Nseq.

10. Electrical machine according to any of claims 8 or 9, wherein the number of different winding schemes in the plural stator segments (101a, b,c) is equal to the number of phases or a multiple thereof, wherein the number of phases is in particular three.

11. Electrical machine according to any of claims 8 to 10, wherein the number of first teeth Qs plus the number of second full teeth AQs is the total number of teeth of the stator, wherein

2 * p + 2 * Ap is the total number of poles in the electrical machine, wherein p is the number of pole pairs, wherein Ap is the number of added pole pairs, wherein Qs, 2p have a common divider, wherein Qs/ (2*p) is 1.2, wherein p is an integer number, Ap is an integer number, Ap is in particular an even number greater than 1. 202301179

25

12. Electrical machine according to any of claims 8 to 11, wherein ip is the circumferential width or pole pitch of each of the poles ,

TS is the circumferential width or slot pitch of each of the first slots, tau_p/tau_s (Qs,ps) = tau_p/tau_s (Qs+Delta_Qs, ps+Delta_P) = ip/is = Qs/ (2p) , w_EHT is the width of the second teeth, wherein TS depends on AQs, on w_EHT and on Qs, wherein ip depends on p and Ap.

13. Electrical machine according to any of claims 8 to 12, wherein the electrical machine is characterized by the fol- lowing : Qs=216 and AQs=12 and 2p=180 and 2*Ap=4 and with three groups of stator segments, or Qs=216 and AQs=18 and 2p=180 and 2*Ap=12 and with three groups of stator segments, or Qs=288 and AQs=12 and 2p=240 and 2*Ap=8 and with three groups of stator segments, or Qs=288 and AQs=12 and 2p=240 and 2*Ap=4 and with six groups of stator segments, or Qs=288 and AQs=16 and 2p=240 and 2*Ap=8 and with four groups of stator segments, or Qs=324 and AQs=18 and 2p=270 and 2*Ap=6 and with three groups of stator segments, or Qs=336 and AQs=14 and 2p=280 and 2*Ap=4 and with seven groups of stator segments, or Qs=360 and AQs=12 and 2p=300 and 2*Ap=4 and with three groups of stator segments, 202301179

26 or

Qs=360 and AQs=15 and 2p=300 and 2*Ap=6 and with five groups of stator segments, or

Qs=360 and AQs=15 and 2p=300 and 2*Ap=10 and with three groups of stator segments, or

Qs=384 and AQs=16 and 2p=320 and 2*Ap=8 and with four groups of stator segments, or

Qs=432 and AQs=12 and 2p=360 and 2*Ap=4 and with six groups of stator segments, or

Qs=432 and AQs=12 and 2p=360 and 2*Ap=8 and with three groups of stator segments, or

Qs=432 and AQs=18 and 2p=360 and 2*Ap=12 and with three groups of stator segments.

14. Electrical machine according to any of claims 8 to 13, wherein the winding sets of one group of stator segments are connected to one or two converters .

15. Wind turbine (450) , comprising: a rotation hub (453) at which plural rotor blades (454) are mounted; an electrical machine (400) according to any of claims 8 to 14, the rotor (402) of the electrical machine being mechanically, in particular directly without gear box, coupled to the rotation hub (453) .