HK1262905B - Linear flux switching permanent magnet motor - Google Patents

Description

Linear flux switching permanent magnet motor

Technical Field

The invention relates to a linear flux switching permanent magnet machine comprising a longitudinal linear stator with stator teeth facing an air gap, and a mover comprising an armature, the armature comprising an armature framework comprising framework members forming armature teeth of the mover together with at least one permanent magnet, whereby the armature teeth are spaced apart by slots for receiving armature windings. The teeth have a first side fitting against the permanent magnets and a second side facing the slots and fitting against the armature windings, whereby the teeth have an extended width towards the air gap. Such a known construction is shown, for example, in fig. 2(a), with the semi-enclosed slot being formed by a tooth tip which extends at the uppermost part of the tooth so that the area in which the copper or winding is located in the slot is not affected by the tooth tip of increased width. An advantage of this embodiment is that the copper space of the armature winding is not affected by the extended tooth tips.

Background

In linear flux switching permanent magnet machines (FSPM), this solution may lead to over-saturation on the tooth tips, which may be accompanied by leakage flux and may even lead to irreversible demagnetization of the permanent magnets.

A prior art linear flux switching permanent magnet machine is disclosed in US 2016/268883 a 1.

It is therefore an object of the present invention to provide an FSPM machine that reduces the above mentioned problems.

Disclosure of Invention

This object is solved by a linear FSPM machine according to the invention. Preferred embodiments of the present invention are also described in the specification and drawings.

According to the invention, the width increase of the armature teeth starts in the longitudinal direction of the armature teeth, the extended width portion of the armature teeth starting already at the height level of the armature windings in the longitudinal direction i of the armature teeth, i.e. the teeth and the adjacent windings face each other. By this measure, the width increase of the armature tooth occurs over a larger portion of its length, which results in a reduced magnetic flux density at the tooth tip in relation to the known design as shown in fig. 2 (a). Although the space for the copper of the armature winding is reduced in the solution according to the invention, the risk of flux leakage, avoiding excessive flux densities and thus demagnetization of the permanent magnets is substantially reduced.

Preferably, the increase in width of the armature teeth occurs over at least half of its length. Thus, in such a motor geometry, the magnetic flux can be better distributed and coordinated.

Preferably, the width of the armature teeth increases continuously and does not form an edge on its second side. This geometry of the armature teeth results in uniform flux and a reduction in flux leakage.

In a preferred embodiment of the invention, the increase in armature tooth width increases continuously towards the air gap. This feature results in the second flank being increasingly curved outwardly in the direction of the tooth tip or air gap in the direction of the adjacent slot. Thus, flux leakage at the tooth tip is minimized and no over-saturation occurs in the direction of the air gap.

In a preferred embodiment of the invention, the permanent magnets embedded in the armature teeth protrude from the armature framework base on the rear side facing away from the air gap. Therefore, the leakage flux of the framework base region is effectively reduced. Preferably, the size of the protrusion is in the range of 2mm to 6mm, preferably in the range of 3mm to 5 mm.

Preferably, the number of mover teeth per meter length in its moving direction of the mover is 22 to 42, in particular 27 to 37. This is a rather high number of teeth (poles). Due to saturation, this increase of the poles results on the one hand in a reduction of the torque, compared to, for example, 13 poles per meter. However, a higher number of poles reduces the cogging torque or torque ripple of the motor. On the other hand, according to the basic concept of the present invention, the saturation effect due to the large number of magnetic poles and the reduction in torque is satisfied by manufacturing the armature teeth with the extended width portions.

Preferably, two different permanent magnets are fitted between the first sides of each armature tooth, whereby the second permanent magnet extends over a larger part of the length of the armature tooth, while the first permanent magnet is fitted on the first permanent magnet towards the air gap a.

In the region of the armature tooth tips, the magnetic flux density is very high, which can lead to over-saturation. This is avoided as the armature teeth gradually increase in width. Further away from the tooth tip, the magnetic flux density in the permanent magnet may drop to a relatively low value. Such low operating flux density values can lead to irreversible demagnetization of the permanent magnet, particularly when the permanent magnet is operated at high temperatures. Therefore, a permanent magnet with good demagnetization should be selected for the tooth region. In any case, magnets with good irreversible demagnetization, for example neodymium magnets, have a weaker remanence, which means that the performance of the machine is degraded by choosing magnets that are stronger in terms of magnetization, while such magnets are weaker in terms of remanence on the other hand. The use of two different permanent magnets over the entire length of the armature tooth therefore solves this problem, since a second permanent magnet is used on the uppermost part of the length of the armature tooth, which second permanent magnet has good demagnetization but a low remanence, and a first permanent magnet with a high remanence is used only in the tooth tip region, which leads to good efficiency. This permanent magnet mixture meets the requirements for highly efficient permanent magnets and on the other hand has a good protection against demagnetization at the uppermost part of the length of the armature tooth.

Preferably, the first permanent magnet has a larger cross-sectional area in a plane parallel to the air gap than the second permanent magnet, which is obtained by a larger width than the second permanent magnet. This has the effect of improving the efficiency of the entire set of first and second magnets and reducing magnetic flux leakage.

In a preferred embodiment of the invention, the upper surface of the first permanent magnet is aligned with the tooth tip. This leads to the fact that the first permanent magnet is used in the region where the highest magnetic flux density is present. By using a second permanent magnet with a low remanence but on the other hand a good demagnetization, the operating efficiency and reliability of the SPM-motor can be substantially improved.

Preferably, the materials of the first and second permanent magnets are different from each other as described above, so that the second magnet preferably has a lower remanence but a better irreversible demagnetization than the first permanent magnet, which preferably has a higher remanence in order to increase efficiency. Since the magnetic flux density in the lower part of the armature teeth is not as high as in the upper region, in particular the tooth tips, the low remanence together with the good demagnetization increases the reliability of the machine.

In a preferred embodiment of the invention, the number of slots is increased. In this way, the flux density in each slot is reduced, which in turn reduces flux leakage, and the excessive flux density in the teeth ceases and thus also reduces the risk of demagnetization of the permanent magnet. Thereby, the armature architecture member and the permanent magnet may have a reduced width. Preferably, therefore, the width of the armature teeth is less than 30% of the width of the gap. In the present application, the term "width" refers to the extension in the direction of motion of the mover (or the longitudinal direction of the stator). The term "length" relates to the dimension perpendicular to the plane of the air gap.

In a preferred embodiment, the armature has at least one armature seat extending parallel to the air gap. The armature member protrudes from the armature base in the air gap direction, i.e., perpendicular to the armature base. The armature base may be a single piece part extending over a larger part of the length of the mover, e.g. extending over more than a third, a half or even the complete length of the mover. A correspondingly large number of armature components, preferably one-piece parts, are connected to this armature base. Alternatively, the armature can also be formed by a series of individual U-shaped armature structures which have only two structure members as armature members extending perpendicularly to the structure base. In any of these cases, the armature member forms part of an armature tooth. Then preferably the increase in tooth width of the armature teeth towards the air gap is formed by the increased width of the two armature members embedding the permanent magnets and the increase in width of the first permanent magnet relative to the second permanent magnet. In particular, if this feature is combined with a higher remanence of the first permanent magnet relative to the second permanent magnet, this will result in a reduced saturation of the teeth and an increased torque.

The invention also relates to an elevator comprising a linear motor as described above. Thereby the mover of the FSPM motor is connected along one side of the elevator car and the stator is mounted on a beam extending along the elevator hoistway. An elevator with a motor thus specified has on the one hand good efficiency and on the other hand good operating characteristics and high reliability, in particular against demagnetization of the permanent magnets of the FSPM motor.

The following terms are used as synonyms: armature architecture-lamination stack-stack section; PM-permanent magnet; a copper-armature winding; motor-machine.

The present invention highlights three techniques for improving the magnetic properties of FSPM machines, as follows:

1. tooth width increasing towards the air gap

2. Magnet extension of permanent magnet at armature base

3. Realization of a hybrid permanent magnet of at least two different permanent magnets

1. Tooth width increasing towards the air gap

If the number of slots is increased (e.g., from 13 slots to 25 slots), the permanent magnet thickness and armature tooth thickness in a 25 slot machine is half that of a 13 slot configuration (if no other geometry modifications are made).

Assuming that the number of slots is doubled, the increase in the number of slots results in the new slots having half the thickness of the original slots. Thus, in a motor with more slots, the magnetic circuit has a reluctance close to twice that of the original motor with a smaller number of slots. One of the main effects of higher reluctance comes from the narrower air gap region. In fig. 3a and 3b it is shown that in the case of thin teeth the air gap area through which the magnetic flux is conducted is smaller than for thick teeth as shown in fig. 3b, as shown in fig. 3 a. If, for example, the width of a thin tooth is half the width of a thick tooth, this means that the reluctance in the case of a thin tooth according to fig. 3b is twice the reluctance in the case of a thick tooth according to fig. 3a, since the reluctance is inversely proportional to the conduction area (a), as seen in equation (1).

Wherein R is_δIs the reluctance of the air gap, δ is the length of the air gap, μ₀Is the magnetic permeability of a vacuum, A_δIs the flux conducting region.

The higher reluctance inevitably results in a smaller magnetic flux of the individual permanent magnets conducted through the air gap. Thus, if the FSPM machine has a greater number of slots and a correspondingly small tooth thickness, it is advantageous to apply a machine with an increased tooth width to result in a semi-closed armature slot. The objective is to increase the air gap area through which the magnetic flux is conducted, as shown in fig. 4a, a rectangular tooth design is disclosed, while fig. 4b shows a tooth width increased design.

Air gap reluctance may be significantly reduced by applying semi-closed slots in FSPM with thin armature teeth. However, this is a conventional method of increasing the magnetic flux across the air gap in a PMSM. However, this approach has a significant disadvantage. Fig. 5a explains the reason for the disadvantage. In this figure, it is shown that the cumulative effect of flux concentration in the teeth results in strong flux over-saturation towards the air gap. However, this over-saturation increases the reluctance of the magnetic circuit (not in the air gap, but in the stack of laminations), thus reducing the PM flux across the air gap.

The semi-enclosed slots are typically implemented with a tooth tip, as shown in fig. 2 a. Therefore, the tooth tips should take up as little space as possible in the slots to reserve this space for copper (below the winding level 28). However, the applicant has found that in FSPM machines it has been shown to be advantageous to widen the teeth towards the air gap compared to reserving space for the copper. The wider teeth compensate for less copper in the slots and increase the force density of the FSPM machine by increasing the PM flux across the air gap. Accordingly, the preferred tooth design of the armature changes from the prior art semi-closed gap as shown in fig. 2a to a shape according to fig. 2b and 2c, wherein the width of the teeth increases extending to the area of copper (the area at the copper level 28 of the armature winding). Thus, in fig. 2a, the width increase extends over half the length of the armature teeth. In fig. 2c, the width increase extends even over the entire length of the armature tooth, calculated from the copper ground or the frame base.

This may prevent local strong supersaturation. Thus, the performance of the FSPM machine is enhanced. A comparison of the forces generated by the motor topology with semi-closed slots (fig. 2a) and the design of the present invention (fig. 2b) is shown in fig. 6.

In fig. 6, the forces generated by the FSPM with semi-closed slots are shown in solid lines, while the tooth profile of the proposed invention (with increasing width towards the air gap already in the copper region) is shown in dashed lines. It can be seen that the force generated by the FSPM machine can be increased by 30% for the proposed tooth form.

2. Magnet extension at armature base

Conventionally, in FSPM machines, the magnets have the same height as the stack of laminations (or the length of the frame member plus the extension of the frame base in the direction L perpendicular to the air gap). However, if the main magnetic circuit has a high magnetic resistance, a certain amount of flux leakage may occur. If the amount of flux leakage is moderate, it is not critical to the density of the force produced by the FSPM machine. However, if such flux leakage occupies some space in the stack or armature architecture, it may result in increased over-saturation of certain areas, which in turn may increase the reluctance of the main magnetic circuit. Thus, flux leakage may occur at the armature base between the two armature architectures. This leakage flows on the same path as the main and useful magnetic flux and therefore has some effect on the overall magnetic circuit reluctance. In order to reduce leakage at the armature base, the magnet length is extended in such a way that it protrudes the armature framework on the back side facing away from the air gap.

Thus, fig. 7a shows the flux density distribution and leakage path between the two armature architectures when the permanent magnets do not protrude out of the rear of the armature architecture. Fig. 7b shows the magnetic flux density distribution and the magnetic flux leakage when the magnet protrudes (protrudes) by about 3.5 mm. In the case of an extended permanent magnet, the magnetic flux density at the lamination tooth tip is reduced and the area can be made thinner and thus the slot space for copper is increased.

3. Realization of hybrid permanent magnet

The magnetic circuit of FSPM with relatively thin teeth has a large magnetic reluctance. Therefore, the magnetic flux density in the permanent magnet may drop to a relatively low value. Such low operating flux density values can lead to irreversible demagnetization of the permanent magnet, particularly when the permanent magnet is operated at high temperatures.

To avoid such irreversible demagnetization, the type of material chosen for the permanent magnet should be dedicated to the harsh operating conditions. However, permanent magnets, such as rubidium magnets, have good irreversible demagnetization and, on the other hand, have a weak remanence. This means that the performance of the machine will decline with the choice of magnets that are stronger in demagnetization and weaker in remanence. Preferably a hybrid permanent magnet system is employed, wherein at least two different types of magnets are selected:

a) a first permanent magnet, generating a primary working flux.

b) A second permanent magnet, eliminating flux leakage between the laminated segments and maintaining the primary flux (generated by the first magnet set) in the correct path.

By this division, the materials of the two different permanent magnets can be optimized according to their function. The first permanent magnet group does not work under severe conditions but can therefore be made of a type of material with a high remanence (e.g. Br ═ 1.3T), while the second permanent magnet does not need to have a high remanence, since its effect on the main flux is rather low, but it works at low flux density and needs to have a good irreversible demagnetization. Thus, the set of second permanent magnets may be made of a type of material having a low remanence (e.g. Br ═ 1.1T) but good demagnetisation.

In order to increase the efficiency of the first set of magnets generating the actual magnetic flux and at the same time optimize the segment shape to reduce the magnetic flux leakage, it is advantageous to make the first permanent magnet wider (with a larger cross-sectional area) than the second set of permanent magnets, as shown in fig. 1 and 8. An advantageous hybrid magnet material comprising at least two different permanent magnets and preferably having different widths provides more freedom in the optimization of the FSPM machine of the invention to enhance its performance and avoid irreversible demagnetization.

Preferably, and just as the armature geometry of the motor, the armature is formed by a U-shaped armature architecture (stacked segments), whereby each permanent magnet of the mover is embedded between two adjacent armature architecture sides, and wherein the armature winding is located between two parallel members of the U-shaped armature architecture, which parallel members together with the embedded permanent magnets form an armature tooth.

Preferably, each armature framework is formed from stacked armature framework sheet metal, as this is a reliable and current approach in armature design.

Preferably, the at least one permanent magnet is magnetized in a direction perpendicular to the longitudinal direction of the armature teeth. In this case, the successive permanent magnets in the width direction w of the mover are preferably magnetized in opposite directions.

Preferably, the length of the permanent magnet in the length direction i of the tooth is greater than the length of the armature architecture member, in particular generally greater than the length of the armature architecture. This feature ensures that the permanent magnets protrude from the back side of the armature, thereby improving the magnetic flux properties, in particular reducing flux leakage.

Preferably, the width of the armature teeth, which are constituted by permanent magnets embedded between two frame members, is in the range of 40% to 65%, preferably in the range of 50% to 60%, relative to the width of the adjacent armature slots, in the moving direction of the mover, which of course involves non-width extending tooth portions. This pole geometry results in a very favorable magnetizability and a strong and uniform magnetic flux.

Preferably, the maximum width of the width extension of the tooth is in the range 30% to 60%, in particular in the range 40% to 50% of the width of the frame member at its non-width extension. This results in an increase in saturation and a higher torque, in particular an increase in the number of poles per meter length of the mover, i.e. in the range of 22 to 42, in particular 27 to 37 per meter length of the mover.

Advantageously, the tooth width increase is achieved at least in part by an increase in the width of the increased width portion of the framing member. Thus, the extended tooth geometry can be easily designed by the geometry of the width extension. Of course, an increase in the width of the permanent magnets may also have an effect on the width extension towards the tooth tip, especially if a plurality of permanent magnets are used in one tooth or pole.

The mover in a passenger elevator usually has a length in the range of 0.5 to 1.5 meters, in particular in the range of 0.7 to 1 m.

The following terms are used as synonyms: armature member-framework member; armature base-frame base; flux-magnetic flux; armature architecture-armature iron; tooth-pole

The invention is also applicable in principle to rotating electrical machines, in which case the air gap is circular and not linear.

Drawings

Some prior art and techniques of the present invention are described below by way of example in connection with the accompanying schematic drawings.

Fig. 1 shows a longitudinal cross-section through a mover and a part of a stator of an FSPM machine according to the invention;

fig. 2(a) shows an armature architecture design according to the prior art, with semi-closed slots;

fig. 2(b) and 2(c) show armature architecture shapes according to the present invention;

fig. 3a) and 3b) are diagrams illustrating the flux when the tooth width is reduced due to an increase in the number of teeth and a reduction in the width of the armature architecture member;

fig. 4a) and 4b) show the flux in the case of a known semi-closed slot;

FIGS. 5a and 5b illustrate magnetic flux in a prior art armature tooth and in an armature tooth according to the present invention;

fig. 6 illustrates forces generated by the conventional mover having a semi-closed slot according to fig. 2(a) and the mover having an increased tooth width according to fig. 2 (b);

figures 7a and 7b show the magnetic flux leakage at the base of the architecture with the conventional design (figure 7a) and with permanent magnet extensions according to the invention (figure 7 b);

fig. 8 shows the magnetic flux of the mover armature of the present invention having an increased tooth width, and a permanent magnet mixture composed of two different permanent magnets.

Detailed Description

Fig. 1 shows a linear FSMP motor 10 comprising a mover 12 and a stator 14, the stator 14 only being shown in part, since in high-rise elevators in elevator shafts the stator typically extends over a length of several meters to several tens of meters or even hundreds of meters. The mover 12 is usually attached beside the side of the elevator car and the cooperation between the stator 14 and the mover 12 is used to move the elevator car vertically along the elevator shaft. An air gap a is provided between the stator 14 and the mover 12, whereby on the stator side the stator teeth 16 face the air gap a, while on the mover 12 side an armature 13 is provided, comprising a plurality of preferably U-shaped armature frameworks 15 positioned in sequence and adjacent to each other in the width direction w of the armature 13, separated only by permanent magnets 20, 22 positioned therebetween. l denotes the length direction of the armatures 13 in the direction of the air gap a (perpendicular to the air gap plane) to define the area of the armatures with respect to their distance from the air gap a. These directional designations apply to all of the drawings.

Each armature frame 15 is composed of a frame base 21 having two parallel frame members 23 extending perpendicular to the frame base 21. The frame member 23 with two adjacent armature frames 15 forms an armature tooth with the permanent magnets 20, 22 embedded between them. The armature teeth 18 protrude from the armature 13 in the direction of the air gap a. Slots 30 adapted to receive armature windings 32 are formed between the frame members 23 of each armature frame 15.

The armature framework 15 is a regularly stacked stack or stack segments, respectively forming a stamped metal sheet. The armature structure 15 may also be formed by a plurality of these U-shaped structures in succession as a one-piece component, thereby reducing the number of separate armature structures 15 for the armature 13.

The structural members 23 of two adjacent armature architectures embed the second permanent magnet 20 over most of the length l of the armature teeth 18. The first permanent magnet 22 is located on top of the second permanent magnet 20, in particular in the region of the tooth tip 19. The first permanent magnet 22 has a larger base area and width than the second permanent magnet 20 and is aligned with its upper surface with the tips 19 of the armature teeth 18 facing the air gap a.

The second permanent magnet 20 protrudes with a projection d over the rear of the armature 13 formed by the frame base 21 of the armature frame 15, which reduces flux leakage in the region of the frame base 21.

Linear FSPM machines with these geometries have high efficiency and low flux leakage.

Fig. 2(b) and 2(c) show two different possible geometries of an armature iron or armature framework 15 for a mover, whereby in the embodiment of fig. 2(b) the increasing width portion 36 of the framework member 23 extends over half of its length, whereas in the embodiment of fig. 2(c) the increasing width portion 36 extends over the entire length l of the framework member 23.

Fig. 3a and 3b generally illustrate the effect of the reduced width of the framing member 23 on the flux between the armature 13 and the stator 14.

Fig. 4a and 4b generally illustrate the flux increasing effect of the well-known semi-closed slot scheme 36 of the structural member 23 on the flux between the armature 13 and the stator 14.

Fig. 5a and 5b illustrate the advantage of reduced flux density between the armature 13 and the stator 14 when using teeth 18 of increased width according to the invention, wherein the increased width portion 36 of the structural member causes a reduction in flux density (black arrows) between the armature teeth 18 and the stator teeth 16.

With respect to fig. 6 and 7, reference is made to the general description above.

Fig. 8 shows the magnetic flux of a linear FSPM machine of the invention with armature teeth 18 extending in width on one side and with a hybrid permanent magnet consisting of a second permanent magnet 20, preferably with a lower remanence (and correspondingly higher demagnetization stability) at the uppermost part of the length of the tooth 18, the tooth 18 being covered by a first permanent magnet in the direction of the tooth tip 19, the first permanent magnet 22 having a larger width than the second permanent magnet 20. These second permanent magnets 22 also have a higher remanence than the first permanent magnets 20 to improve the efficiency of the machine.

In summary, the increase in width of the armature teeth 18 is achieved by the increased width portion 36 of the frame member 23 and the increased width of the first permanent magnet 22 relative to the second permanent magnet 20. It can be seen that the magnetic flux density in the interface between the armature teeth 18 and the stator teeth 16 is moderate, which results in less flux leakage and a reduced tendency for irreversible demagnetization of the permanent magnets 20, 22.

The invention is not limited to the embodiments disclosed but may be varied within the scope of the following claims.

List of reference numerals

10 linear FSPM motor

12 mover

13 armature

14 stator

15 armature architecture

16 stator teeth

18 armature teeth

20 second permanent magnet

21 armature base-frame base

22 first permanent magnet

23 armature component-framework component

24 first side of the structural member facing the permanent magnet

26 second side of the channel-facing frame member

Level of armature winding in 28 slots

30 groove

32 armature winding-copper

Width extension of 36 frame member

l perpendicular to the length direction of the mover region

d extension of the second permanent magnet at armature ground

w width direction in the length or moving direction of the mover

a air gap

Claims (20)

1. Linear Flux Switching Permanent Magnet (FSPM) machine (10) comprising a longitudinal linear stator (14) with stator teeth (16) facing an air gap (a) and a mover (12) comprising at least one armature (13), said armature (13) being composed of a plurality of U-shaped armature frameworks (15), each U-shaped armature framework (15) being composed of a framework base (21) extending parallel to the air gap (a) and two parallel framework members (23) extending perpendicular to said framework base (21),

wherein the U-shaped armature architectures (15) are positioned consecutively and adjacent to each other in a direction parallel to the air gap (a), separated by only permanent magnets (20, 22) positioned therebetween,

wherein the frame members (23) of two adjacent U-shaped armature frames (15) form armature teeth (18), which armature teeth (18) protrude from the armature (13) in the direction of the air gap (a), wherein a slot (30) is formed between the frame members (23) of each U-shaped armature frame (15) to accommodate an armature winding (32),

wherein the permanent magnets (20, 22) consist of a first permanent magnet (22) and a second permanent magnet (20), wherein the first permanent magnet (22) is located on top of the second permanent magnet (20) in the region of the tooth tip (19),

wherein the first permanent magnet (22) has a larger base area and width than the second permanent magnet (20) and is aligned with its upper surface, the tooth tip (19) of the armature tooth (18) facing the air gap (a), and wherein the second permanent magnet (20) is embedded over a majority of the length (l) of the armature tooth (18),

and wherein the structural members (23) comprise a width extension (36) such that the width of the armature teeth (18) towards the air gap (a) increases, the increase in tooth width of the armature teeth (18) towards the air gap (a) being formed by the width extensions (36) of the two structural members (23) embedding the permanent magnets (20, 22) and the increase in width of the first permanent magnet (22) relative to the second permanent magnet (20).

2. The electric machine (10) of claim 1, wherein the increase in width of the armature teeth (18) occurs over at least half of their length.

3. The electric machine (10) of claim 1, wherein the increase in width of the armature teeth (18) occurs over the entire length thereof.

4. The electric machine (10) according to any of claims 1-3, wherein the extended width extension (36) of the armature teeth (18) increases continuously and does not form an edge in its side (26) facing the slot (30).

5. The electrical machine (10) of claim 4, wherein the increase in width of the width extension (36) continuously increases toward the air gap (a), causing the side (26) thereof facing the armature winding (32) to increasingly curve outward toward the slot (30).

6. The electrical machine (10) according to claim 5, wherein the permanent magnets (20, 22) embedded in the armature teeth (18) protrude with a protrusion (d) over the U-shaped armature structure (15) in a direction away from the air gap (a).

7. The electric machine (10) of claim 6, wherein an upper surface of the first permanent magnet (22) is aligned with the tooth tip (19).

8. The electric machine (10) of claim 7, wherein the first and second permanent magnets (20, 22) are different materials from each other.

9. The electric machine (10) of claim 8, wherein the second permanent magnet (20) has a lower remanence than the first permanent magnet (22).

10. The electrical machine (10) according to claim 9, wherein the number of armature teeth (18) per meter length of the mover in its moving direction is in the range of 22 to 42.

11. The electrical machine (10) according to claim 9, wherein the number of armature teeth (18) per meter length of the mover in its moving direction is in the range of 27 to 37.

12. The electrical machine (10) according to claim 10 or 11, wherein the armature (13) is formed by a U-shaped armature architecture (15) comprising an architecture base (21) and at least two parallel architecture members (23) perpendicular to the architecture base (21) and facing the air gap (a), whereby the permanent magnets (20, 22) are embedded between first sides (24) of the architecture members (23), and wherein the armature windings (32) are located between second sides (26) of the architecture members (23).

13. The electric machine (10) of claim 12, wherein each U-shaped armature architecture (15) is formed from stacked armature architecture sheet metal.

14. The electrical machine (10) according to claim 13, wherein the length of the permanent magnets (20, 22) in the length direction (l) of the armature teeth (18) is greater than the length of the frame members (23) of the U-shaped armature frame (15).

15. The electrical machine (10) according to claim 14, wherein the width of the armature teeth (18) in relation to the width of the adjacent slots (30) in the moving direction of the mover is in the range of 40% to 65%.

16. The electrical machine (10) according to claim 14, wherein the width of the armature teeth (18) in relation to the width of the adjacent slots (30) in the moving direction of the mover is in the range of 50% to 60%.

17. The electric machine (10) of claim 14, wherein the maximum width of the width extension (36) of the armature teeth (18) is in the range of 30% to 60% of the width of the non-width extending tooth portion.

18. The electric machine (10) of claim 14, wherein the maximum width of the width extension (36) of the armature teeth (18) is in the range of 40% to 50% of the width of the non-width extending tooth portion.

19. The electric machine (10) of claim 14, wherein the tooth width increase is achieved at least in part by an increase in width of the width extension (36) of the frame member (23).

20. Elevator comprising a linear Flux Switching Permanent Magnet (FSPM) motor (10) according to any of the preceding claims, wherein the mover (12) is connected along one side of the elevator car and the stator (14) is mounted on a beam extending along the elevator hoistway.