Phase unit for an electric machine with segmented magnetic cores

Abstract

A phase unit 1 for an electric machine 3, the phase unit comprising a first carrier plate 10A and a second carrier plate 10B, a coil 13 arranged between the first plate 10A and the second plate 10B, and magnetic cores 11A-11D fixed to the first plate and the second plate and retaining the coil. The magnetic cores are respectively segmented into a first part fixed to the first carrier plate and a second part fixed to the second carrier plate. The first and second parts may respectively comprise a soft-magnetic compound where the compound may comprise soft-magnetic powder held together by a non-magnetic binder. The soft-magnetic powder may comprise a nickel-iron alloy or a cobalt-iron alloy. The first parts may be engaged with the respective second part via a form fit. A gap may be formed between the first and second parts of a respective magnetic core. A respective first part may be separated from the corresponding second part along a segmentation line where the segmentation line comprises a step or a protrusion. The first part and the corresponding second part together may form a ball joint. The phase unit may be configured for driving a rotor of the electric machine that may be a transverse flux machine used in an electric propulsion unit for an aircraft.

Description

FIELD The present disclosure particularly relates to a phase unit for an electric machine, to an electric machine, to an electric propulsion unit and to a method for manufacturing a phase unit. BACKGROUND Electric propulsion units for aircrafts allow the use of sustainably generated energy and can be particularly quiet. In addition, electric propulsion units often only require little maintenance compared to, e.g., combustion engines. Phase units of electric machines may comprise an electric coil and one or more magnetic cores, e.g., iron cores. In the case of electric motors and other electric machines, an aim can be to improve various target values, e.g. energy efficiency, power-to-weight ratio or service life. At the same time, it may be desirable to manufacture electric machines as simply and reliably as possible. However, such objectives may conflict with each other. There is a need to provide an electric machine that addresses at least some of the aforementioned problems or at least provides a useful alternative to known electric machines. SUMMARY According to an aspect, a phase unit for an electric machine is provided. The phase unit comprises a first carrier plate and a second carrier plate, an electrical coil arranged in a position between the first and second carrier plates and a plurality of magnetic cores (e.g., iron cores). The magnetic cores are fixed to the first and second carrier plates. The magnetic cores retain the coil in the position between the first and second carrier plates. Therein, the individual magnetic cores are segmented into a first part that is fixed to the first carrier plate and a second part that is fixed to the second carrier plate. By segmenting the magnetic cores such that a first part is fixed to the first carrier plate and a second part is fixed to the second carrier plate, the manufacturing of the phase unit can be simplified, because two halves can be simply attached to one another so as to retain the coil. Each magnetic core may grasp around at least a part of the coil. This allows to optimize the shape of the magnetic cores without complicating the process of assembly. When the coil is provided with an electrical current, magnetic field lines extend through the two parts of each magnetic core. The phase unit can also be referred to as coil assembly (e.g., stator coil assembly) or as an assembly for an electric machine (more particularly, for a stator of an electric machine). The coil may be supplied with one phase of an alternating current (AC), e.g., one phase of a polyphase AC, such as a three-phase AC. The first and second parts (e.g., each of the first and second parts) may, respectively, comprise a soft-magnetic compound (SMC). By using a soft-magnetic compound, more freedom in designing the shape of the magnetic cores can be gained. For example, the soft-magnetic compound comprises soft-magnetic powder held together by a non-magnetic binder. The non-magnetic binder may also be an electrical isolator. Alternatively, or in addition, the particles of the soft-magnetic powder may be coated with an isolator. The binder may be a plastics material. The soft-magnetic powder may comprise (or consist of) a nickel-iron alloy and / or a silicon-iron alloy and / or a cobalt-iron alloy. These alloys allow to provide advantageous magnetic properties. The first parts (e.g., each of the first parts) may be connected and / or engaged with the respective second parts, e.g., via a form fit. This allows to secure the parts in place, even with a thin design. In some embodiments, a gap is formed between the first and second parts of a respective magnetic core. This allows to avoid stress in the material while a potential loss of performance is kept small. A respective first part may be separated from the corresponding second part along a segmentation line. The segmentation line may comprise a step and / or a protrusion and / or a recess. This allows to create a form fit with a simple design. In some embodiments, a respective first part and the corresponding second part together form a ball joint. This allows a secure form fit in two directions. One of the two parts may have a protrusion with the shape of a part of a ball, the other one of the two parts may have a recess with a mating shape. The phase unit may be configured for driving a rotation of a rotor of the electric machine around an axis of rotation. The magnetic cores may be segmented into the respective first and second parts in an axial direction parallel to the axis of rotation. This allows to provide an effective guidance of the magnetic field lines. At least some of the magnetic cores may be arranged along at least a part of a circle around the axis of rotation. By this, both the coil may be securely held in place, and the magnetic field lines may be uniformly guided. In some embodiments, the magnetic cores are segmented into the first and second parts at a central region between the first and second carrier plates. By this, a symmetric design and simple assembly is enabled. For example, the magnetic cores embrace the coil, e.g., extend around at least a quarter or half of the coil. This allows to securely retain the coil. According to an example, the magnetic cores are C-shaped to securely retain the coil and effectively guide the magnetic field lines. According to an aspect, an electric machine comprises a stator and a rotor being rotatable relative to the stator, wherein the stator comprises one or more phase unit(s) in accordance with any one aspect or embodiment described herein. The electric machine may comprise at least one such phase unit for each of a plurality of, e.g. three, phases of an electrical current. The electric machine may be a transverse flux machine. Transverse flux machines allow a high energy density and efficiency. According to an aspect, an electric propulsion unit, e.g., for an aircraft, is provided. The electric propulsion unit may comprise the electric machine of any aspect or embodiment described herein. The electric propulsion unit may comprise a propeller arranged so as to be driven by the electric machine. According to an aspect, an aircraft is provided comprising the electric machine of any aspect or embodiment described herein and / or comprising the electric propulsion unit according to any aspect or embodiment described herein. According to an aspect, a method of manufacturing a phase unit (e.g., the phase unit in accordance with any one aspect or embodiment described herein) for an electric machine is provided, the method comprising: forming first and second parts (e.g., from a soft-magnetic compound) for assembling magnetic cores; mounting the first parts on a first carrier plate and mounting the second parts on a second carrier plate; arranging a coil between the first and second carrier plates; and approaching the first and second carrier plates with the first and second parts to one another so as to assemble the magnetic cores and retain the coil by the magnetic cores. The skilled person will appreciate that except where mutually exclusive, a feature or parameter described in relation to any one of the above aspects may be applied to any other aspect. Furthermore, except where mutually exclusive, any feature or parameter described herein may be applied to any aspect and / or combined with any other feature or parameter described herein. BRIEF DESCRIPTION OF THE DRAWINGS Exemplary embodiments are now described with reference to the figures, wherein: FIG. 1 shows an aircraft in the form of an airplane with electric propulsion units; FIG. 2 shows a sectional view of an electric machine of one of the electric propulsion units of the aircraft of FIG. 1; FIG. 3 shows several parts of a stator of the electrical machine of FIG. 2; FIG. 4 shows a soft-magnetic compound; FIGS. 5A-5C show different views of a magnetic core of the electric machine of FIG. 2; FIGS. 6A-6C show different views of a magnetic core for the electric machine of FIG. 2; FIGS. 7A-7C show different views of a magnetic core for the electric machine of FIG. 5 2; FIGS. 8A and 8B show different views of a magnetic core for the electric machine of FIG. 2; and FIGS. 9A-9C show various steps of a method of manufacturing a phase unit for an electric machine. 10 The following table lists the reference numerals used in the drawings with the features to which they refer: Ref no. Feature Figure 1 Phase unit 23 2 Aircraft 1 2 3 Electric machine 1 10A,10B Carrier plate 2 3 9B 9C 9C 11A-11D Magnetic core 2 3 5A SB 5C 6A 6B 6C 7A 7B 7C 8A 8B 12 Frame 3 13 Coil 2 3 9B 9C 20 Fuselage 1 21 Wings 1 22 Electric propulsion unit 1 23 Battery system 1 30 Stator 2 31 Rotor 2 32 Bearing 2 110A-110D First part 5A SB 5C 6A 6B 6C 7A 7B 7C 8A 8B 9A 9B 111A-111D Second part 5A SB 5C 6A 6B 6C 7A 7B 7C 8A 8B 9A 9B 112-112A Gap 5ASB 113A-113C Segmentation line 5A SB 5C 6A 6B 6C 7A 7B 7C 114A, 114B Step 6A 6B 7A 7C 115 Protrusion 5A 5C 9A 9B 116 Receptacle 9A9B 117 Protrusion 8A8B 118 Depression 8A8B 221 Propeller 1 310 Magnet 2 311 Magnet carrier 2 B Binder 4 C Central region 5C G Grain 4 Ref no. Feature Figure M Soft-magnetic compound 4 P Soft-magnetic powder 4 R Axis of rotation 23 DETAILED DESCRIPTION Aspects and embodiments of the present disclosure will now be discussed with reference to the accompanying figures. Further aspects and embodiments will be apparent to those skilled in the art. FIG. 1 shows an aircraft 2 in the form of an airplane having a fuselage 20, wings 21 and one or more, in this example two electric propulsion units 22. The electric propulsion units 22 comprise respective propellers 221. The propellers 221 comprisea plurality of rotor blades, respectively, in this example two rotor blades. In alternative embodiments, the aircraft 2 comprises, for example, one or more fans instead of propellers 221 and / or a plurality of propellers, fans or the like. Each of the electric propulsion units 22 is mounted on one of the wings 21, respectively. The respective propeller 221 is driven by an electric machine 3 of the corresponding electric propulsion unit 22. Furthermore, the aircraft 2 exemplarily comprises a battery system 23 (or alternatively or additionally another energy source, e.g. a fuel cell, a generator, a photovoltaic system or the like). The battery system 23 stores electrical energy for operating the electric propulsion units 22. In the present case, the battery system 23 is connected to inverters which convert a DC voltage of the battery system 23 into an AC voltage, here, a three-phase AC. The AC voltage is applied to the electric machine 3 of the respective electric propulsion unit 22 in order to set the respective propeller 221 in rotation and thus drive the aircraft 2. FIG. 2 shows a sectional view of the electric machine 3 of one of the electric propulsion units 22 of the aircraft 2. The electric machine 3 extends around an axis of rotation R. The electric machine 3 is designed in the form of a transverse flux machine. The electric machine 3 comprises a stator 30 and a rotor 31 rotatable about the axis of rotation R relative to the stator 30. The rotor 31 is rotatably mounted on the stator 30 by means of bearings 32, here in the form of ball bearings, alternatively e.g. plain bearings. The rotor 31 surrounds parts of the stator 30. The stator 30 can be mounted on a supporting structure of the aircraft 2 using a bracket. A shaft can be mounted on the rotor 31. The rotor 31 then drives the corresponding propeller 221 via the shaft. The stator 30 also comprises at least one, in this case several, phase units 1. Each of the phase units 1 is electrically connected to one of the plurality of AC phases (here: of the three phases). Each of the phase units 1 of the stator 30 of the electric machine 3 comprises a first carrier plate 10A, a second carrier plate 10B, a coil 13 arranged between the first and second carrier plates 10A, 10B and a plurality of magnetic cores 11A fixed to the first and second carrier plates 10A, 10B and retaining the coil 13. The carrier plates 10A, 10B are attached to a holder. In the present case, the carrier plates 10A, 10B are aligned parallel to one another. In this example, the carrier plates 10A, 10B are each plate-shaped and made of PEEK, for example. Each of the phase units 1 comprises several magnetic cores 11 A. Several magnetic cores 11A are attached to each of the carrier plates 10A, 10B. In the present case, each magnetic core 11A is attached to each of the two carrier plates 10A, 10B of the respective phase unit 1. Each magnetic core 11A extends between the two carrier plates 10A, 10B. The magnetic cores 11A are each in engagement with the two carriers 10A, 10B. The magnetic cores 11A can also be referred to as iron cores. The magnetic cores 11A have the shape of retaining webs. In the example shown, the magnetic cores 11A are each C-shaped. Coils 13 of the stator 30 are mounted on the magnetic cores 11 A. For each phase unit 1, a coil 13 is mounted between the magnetic cores 11A of the respective phase unit 1. Several of the magnetic cores 11A surround the respective coil 13 on opposite sides of the coil 13. The coils 13 extend at least in sections around the axis of rotation R. The coils 13 are wound in such a way that they extend around the axis of rotation R at least along part of a circle. The magnetic cores 11A of a coil 13 are arranged next to each other around the axis of rotation R. Each of the coils 13 is held between several magnetic cores 11 A. Each of the coils 13 also extends between the two carrier plates 10A, 10B to which the magnetic cores 11A of the coils 13 are attached. The carrier plates 10A, 10B each describe at least a part of a circular disc. In the present case, the magnetic cores 11A together with the respective coil 13 form an inductance. The magnetic cores 11A conduct the magnetic flux of the coil 13. Each of the magnetic cores 11A conducts the magnetic flux of the coil 13 from one carrier plate 10A, 10B to the other. The magnetic cores 11A therefore have two functions, one electromagnetic and one mechanical, namely holding the coil 13. If a respective coil 13 is energised, a magnetic field is created which interacts with magnets 310 of the rotor 31 and thus causes the rotor 31 to rotate about the axis of rotation R relative to the stator 30. The magnetic cores 11A guide the magnetic field lines. In the present example, the stator 30 comprises two coils 13 axially offset along the axis of rotation R, although a design with only one such coil 13, viewed along the axis of rotation R, is of course also possible. The rotor 31 has two carrier plates 10A, 10B for each of the coils 13. The magnets 310 of the rotor 31 are attached to magnet carriers 311 of the rotor 31. The magnets 310 of the rotor 31 are arranged adjacent the ends of the magnetic cores 11A. Along the coil 13, the magnetic cores 11A are arranged pairwise on opposite sides of the coil 13. FIG. 3 shows one of the phase units 1 of the electric machine 3. According to FIG. 3, the carrier plates 10A, 10B are fixed to a frame 12. The frame 12 holds the carrier plates 10A, 10B in place. Here, six of the phase units of FIG. 3 together form a full circle. That is, each phase unit 1 extends over a sixth of a circle. In the present example, the electric machine 3 comprises two times six phase units 1, however, it could alternatively comprise just one disk of six phase units 1, or only three phase units 1, just to mention several examples. The coil 13 extends (with a plurality of windings; note that the coil 13 is shown simplified in FIG. 3 for reasons of illustration only) in an inner section according to a section of an inner circle around the axis of rotation R, makes a turn outwards and returns in an outer section according to a section of an outer circle around the axis of rotation R to a turn inwards connecting to the inner section. The coil 13 is held in place between the two carrier plates 10A, 10B by means of the magnet cores 11A. The magnet cores 11A are arranged alternating on a radially inner side of the coil 13 and a radially outer side of the coil 13. The magnetic cores 11A are C-shaped, wherein the coil 13 is arranged in the receptacle (formed by the C-shape) of each magnetic core 11A. The phase unit 1 comprises a plurality of magnetic cores 11 A. Here, the phase unit 1 comprises more than 2 magnetic cores 11A, more specifically, more than ten magnetic cores 11 A, more specifically, more than 20 magnetic cores 11 A, more specifically, more than 50 magnetic cores 11 A. The magnetic cores 11A are made of a soft-magnetic compound. FIG. 4 shows a sample made of soft-magnetic compound M moulded from a pressed, soft-magnetic powder P. The soft-magnetic powder P comprises grains G. The grains G comprise or consist of a ferromagnetic material. The grains G have an average grain size of less than 1 mm, in the present case less than 0.5 mm. For example, the average grain size is in the range from 0.01 mm to 0.5 mm. The grains G are electrically conductive. However, the grains are (at least partially) electrically insulated from each other by a binder B. Alternatively, or in addition, the grains may be coated with an insulating material. The binder B also bonds the grains G together. The binder may be a polymer, for example. The powder P comprises or consists of a nickel-iron alloy and / or a cobalt-iron alloy. To allow the magnetic cores 11A to closely encompass the coil 13 while simplifying the assembly of the phase unit 1, each of the magnetic cores 11A is segmented into a first part 110A fixed to the first carrier plate 10A and a second part 111A fixed to the second carrier plate 10B, see FIGS. 5A-5C. The first and second parts 110A, 111A may be two halves of the magnetic core 11 A. FIGS. 5A-5C show one of the magnetic cores 11A. Some or all of the plurality of magnetic cores 11A of the phase unit 1 may be constructed as the magnetic core 11A shown in FIGS. 5A-5C. The magnetic core 11A is flat and has two opposing side faces, an upper and a lower end face, an inner face and an outer face. The side faces are the larges faces. The side faces extend parallel to one another. The upper and lower end faces are the smallest faces. The upper and lower end faces are parallel to one another. The inner face is concave. In the assembled state, the inner face contacts the coil 13. The outer face is convex. The outer face faces away from the coil 13 section that is in contact with the inner face. The magnetic core 11A has a central region C, from which two arms extend. Each of the arms has a width (from the inner to the outer face) that increases from the central region C towards the respective upper or lower end. By this shape, the magnetic core 11A may be securely held by a form fit in a corresponding opening in each of the carrier plates 10A, 10B. The first part 110A and the second part 111A of the magnetic core 11A are separated from one another by a segmentation line 113A. Along the segmentation line 113A, the first part 110A and the second part 111A of the magnetic core 11A have the same outer shape. The first part 110A and the second part 111A of the magnetic core 11A have the same length and width at the segmentation line 113A. As such, the first part 110A and the second part 111A of the magnetic core 11A may either be formed separately, or formed as a unitary one-piece magnetic core which is then cut into the two parts 110A, 111A along the segmentation line 113A. The first part 110A and the second part 111A of the magnetic core 11A are aligned with one another. Here a gap 112 is formed between the first part 110A and the second part 111A of the magnetic core 11 A. The gap 112 has a width of, e.g., less than 1 mm. Alternatively, the first part 110A and the second part 111A of the magnetic core 11A contact one another at the segmentation line 113A. Optionally, the gap 112 is filled with an adhesive that fixes the first part 110A and the second part 111A to one another. Further, the first part 110A is engaged with the second part 111A via a form fit. Here, the segmentation line 113A describes a U-shaped form according to which the first part 110A and the second part 111A are engaged with one another. Specifically, the first part 110A comprises a protrusion 115 that is arranged inside a receptacle 116 of the second part 111A. The protrusion 115 (and, accordingly, the receptacle 116) extends from one side face to the other side face of the first part 110A (the second part 111 A). Here the protrusion 115 is rectangular. The receptacle 116 has a shape that matches the shape of the protrusion 115. With respect to the axis of rotation R, the segmentation line 113A extends in radial direction (perpendicular to the axis of rotation R). At the protrusion 115 and receptacle 116, the segmentation line 113A proceeds in the axial direction (parallel to the axis of rotation R). Then the segmentation line proceeds further radially, in the opposite axial direction and further radially. The segmentation of the first part 110A and the second part 111A is in the central region C. Specifically, the segmentation line 113A is arranged in the central region C. The magnetic core 11A is segmented into the first and second parts 110A, 111A in the axial direction parallel to the axis of rotation R. Turning now to FIGS. 6A-6C, a magnetic core 11B is shown. The phase unit 1 may comprise the magnetic core 11B instead of, or in addition to one or more of the magnetic cores 11A. The magnetic core 11B of FIGS. 6A-6C has the same shape as the magnetic core 11A of FIGS. 5A-5C. However, the segmentation line 113B has a different shape. According to FIGS. 6A-6C, the segmentation line 113B comprises a step 114A. In a view on the side faces (see, e.g., FIG. 6C), the segmentation line 113B describes a straight line along the entire depth from the inner face to the outer face of the magnetic core 11B. In axial direction, the segmentation line 113B describes the step 114A. Therein, the step is arranged, in axial direction, in the middle of the magnetic core 11B between the side faces. Here, regarding in circumferential direction around the axis of rotation R, the segmentation line 113B follows a straight line in tangential direction, then proceeds in axial direction and then proceeds again in tangential direction. Turning now to FIGS. 7A-7C, a further magnetic core 11C is shown. The phase unit 1 may comprise the magnetic core 110 instead of, or in addition to one or more of the magnetic cores 11 A, 11B described above. The magnetic core 11C of FIGS. 7A-7C has the same shape as the magnetic core 11A of FIGS. 5A-5C. However, the segmentation line 113C has a different shape. Similar as the magnetic core 11B of FIGS. 6A-6C, according to FIGS. 7A-7C, the segmentation line 113C of the magnetic core 11C comprises a step 114B. Herein, in a view on the inner and outer faces (see, e.g., FIGS. 7A and 7B), the segmentation line 113C describes a straight line along the entire width between the side faces. In radial direction, the segmentation line 113C describes the step 114B. Therein, the step is arranged, in radial direction, in the middle of the magnetic core 11C between the inner and outer faces of the magnetic core 11C. Here, regarding in radial direction, the segmentation line 113B follows a straight line in radial direction, then proceeds in axial direction and then proceeds again in radial direction. Turning now to FIGS. 8A and 8B, a further magnetic core 11D is shown. The phase unit 1 may comprise the magnetic core 11D instead of, or in addition to one or more of the magnetic cores 11 A, 11B, 11C described above. The magnetic core 11D of FIGS. 8A and 8B may have the same outer shape as the magnetic core 11A of FIGS. 5A-5C. However, the segmentation line has a different shape. According to FIGS. 8A and 8B, the magnetic core 11D has a first and a second part 110D, 111D which, when mounted, together form a ball joint. The first part 110D has a depression 118 that describes a part of a ball. The second part 111D has a protrusion 117 that is formed mating with the depression 118 and also describes a part of a ball. The protrusion 117 and the depression 118 are each formed an the surface of the respective part 110D, 111D facing the other one of the two parts 110D, 111D (and, in this example, with a distance to the edges delimiting this respective surface). By means of a segmentation of the magnetic cores 11A-11C that is described by a segmentation line 113A-113C with a step 114A, 114B and / or protrusion 115 or other form-fit feature, a secure fixture of the magnetic core 11A-11C parts 110A-110C, 111A-111C is possible. The first and second parts 110A-110C, 111A-111C consist of the soft-magnetic compound M as described above. FIGS. 9A-9C illustrate a method of manufacturing a phase unit 1. The method comprises forming first and second parts 110A, 111A for assembling magnetic cores 11A, see FIG. 9A as an example. The first and second parts 110A, 111A may be separately formed, or produced by cutting a magnetic core in two. The first and second parts 110A, 111A are made from the soft-magnetic compound M. A plurality of first and second parts 110A, 111A may be formed. The method further comprises mounting the first part(s) 110A on the first carrier plate 10A and mounting the second parts 111A on the second carrier plate 10B, e.g., with a form fit, see FIG. 9B. The method further comprises arranging the coil 13 between the first and second carrier plates 10A, 10B and between the magnetic cores 11A, see FIG. 9B. The method also comprises approaching the first and second carrier plates 10A, 10B with the first and second parts 110A, 111A mounted thereon to one another so as to assemble the magnetic cores 11A and fix the coil 13 by the magnetic cores 11 A, see FIG. 90. Like this, the magnetic cores 11A can be arranged very close to the coil 13, e.g., in contact therewith. This allows a simplified assembly and an increased performance. For assembling the electric machine 3, a plurality of the phase units 1 are mounted (e.g., according to a disk) to form the stator 30, and the rotor 31 is mounted at the stator 30. It will be understood that the invention is not limited to the embodiments abovedescribed and various modifications and improvements can be made without departing from the concepts described herein. Except where mutually exclusive, any of the features may be employed separately or in combination with any other features and the disclosure extends to 5 and includes all combinations and sub-combinations of one or more features described herein.

Claims

1. A phase unit (1) for an electric machine (3), the phase unit comprising:a first carrier plate (10A) and a second carrier plate (10B);a coil (13) arranged between the first carrier plate (10A) and the second carrier plate (10B); anda plurality of magnetic cores (11A-11D) fixed to the first carrier plate (10A) and the second carrier plate (10B) and retaining the coil (13), the magnetic cores (11A-11D) being respectively segmented into a first part (110A-110D) fixed to the first carrier plate (10A) and a second part (111A-111D) fixed to the second carrier plate (10B).

2. The phase unit (1) of claim 1, wherein the first and second parts (110A-110D, IHA-HID) respectively comprise a soft-magnetic compound (M).

3. The phase unit (1) of claim 2, wherein the soft-magnetic compound (M) comprises soft-magnetic powder (P) held together by a non-magnetic binder (B).

4. The phase unit (1) of claim 3, wherein the soft-magnetic powder (P) comprises or consists of a nickel-iron alloy or a cobalt-iron alloy.

5. The phase unit (1) of any preceding claim, wherein the first parts (110A-110D) are engaged with the respective second part (111A-111D) via a form fit.

6. The phase unit (1) of any preceding claim, wherein a gap (112) is formed between the first and second parts (110A-110D, 111A-111D) of a respective magnetic core (11A-11D).

7. The phase unit (1) of any preceding claim, wherein a respective first part (110A-110D) is separated from the corresponding second part (111A-111D) along a segmentation line (113A-113C), wherein the segmentation line (113A-113C) comprises a step (114A, 114B) or a protrusion (115).

8. The phase unit (1) of any preceding claim, wherein a respective first part (110D) and the corresponding second part (111D) together form a ball joint.

9. The phase unit (1) of any preceding claim, configured for driving a rotation of a rotor (31) of the electric machine (3) around an axis of rotation (R), wherein the magnetic cores(11A-11D) are segmented into the respective first and second parts (110A-110D, IHA-HID) in an axial direction parallel to the axis of rotation (R).

10. The phase unit (1) of claim 9, wherein at least some of the magnetic cores (11A-11D) are arranged along a circle around the axis of rotation (R).

11. The phase unit (1) of any preceding claim, wherein the magnetic cores (11A-11D) are segmented into the first and second parts (110A-110D, 111A-111D) at a central region (C) between the first and second carrier plates (10A, 10B).

12. The phase unit (1) of any preceding claim, wherein the magnetic cores (11A-11D) embrace the coil (13).

13. The phase unit (1) of any preceding claim, wherein the magnetic cores (11A-11D) are C-shaped.

14. An electric machine (3) comprising a stator (30) and a rotor (31) rotatable relative to the stator (30), wherein the stator (30) comprises one or more phase unit(s) (1) of any preceding claim.

15. The electric machine (3) of claim 14, being a transverse flux machine.

16. An electric propulsion unit (22) for an aircraft (2), the electric propulsion unit comprising the electric machine (3) of claim 14 or 15 and a propeller (221) driven by the electric machine (3).

17. An aircraft (2) including the electric machine (3) of claim 13 or 14 and / or the electric propulsion unit (22) of claim 16.

18. A method of manufacturing a phase unit (1), the method comprising the steps of: forming first and second parts (110A-110D, 111A-111D) for assembling magnetic cores (11A-11D);mounting the first parts (110A-110D) on a first carrier plate (10A) and mounting the second parts (111 A-111D) on a second carrier plate (10B);arranging a coil (13) between the first carrier plate (10A) and the second carrier plate (10B); andapproaching the first carrier plate (10A) and the second carrier plate (10B) with the firstand second parts (110A-110D, 111A-111D) to one another so as to assemble the magnetic cores (11A-11D) and retain the coil (13) by the magnetic cores (11A-11D).15

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