electric machine

Abstract

An electric machine for use in an aircraft, comprising a rotor and a stator, wherein the rotor comprises a plurality of rotor poles and the stator comprises a plurality of phases, wherein each respective phase occupies at least one elementary block, each elementary block of each phase comprises a set of conductors of the respective phase wound around a plurality of slots of the respective elementary block in a concentrated winding configuration, wherein the stator further comprises at least one sensor located between two elementary blocks, the at least one sensor being configured to measure at least one parameter of the rotor.

Description

TECHNICAL FIELD

[0001] The present invention relates to an electric machine for use in an aircraft. In particular, the present invention relates to an electric machine with integrated sensors for detecting parameters of the rotor, such as position and temperature. BACKGROUND

[0002] Electric aircraft propulsion systems typically comprise a fan (propeller) connected to an electric machine. The electric machine is typically formed by an assembly comprising magnetic circuit components of a rotor and a stator. It is known that the rotation of the rotor relative to the stator causes the magnetic field generated by the rotor to interact with the windings provided on the stator, thereby generating an induced electromotive force (EMF) and / or an electric current. In a permanent magnet generator, the magnetic field of the rotor is generated by permanent magnets, which induce an AC voltage in the stator windings as the moving magnetic field of the permanent magnets passes through the stator windings.

[0003] In order to control the machine, the armature AC excitation must be synchronized with the rotational speed (i.e. the back electromotive force), so that the torque is subsequently obtained, it is necessary to know the rotor position. Typically, the rotor position is measured using a rotary transformer or a Hall effect sensor integrated in the rotor and rotating with the rotor. However, sensors mounted to the shaft, such as the ones typically used, can be very expensive, particularly if high accuracy is required, can be unreliable and have low fault tolerance capabilities, are typically bulky and can increase the overall weight of the machine due to the need for a larger shaft to accommodate the sensor. In order to overcome the problems of sensors integrated with the rotor, the "sensorless control law" is implemented, also known as observers and estimators. This technique monitors the rotor position only by measuring the electrical waveforms (voltage and current) of the stator windings via power electronics. However, this approach is not particularly reliable at low speeds and / or low loads, and is not always accurate, since the back electromotive force and / or the current generated are very small.

[0004] Therefore, there is a need to improve the method of monitoring the rotor position in an electric machine. SUMMARY

[0005] A first aspect of the present invention provides an electric machine for use in an aircraft, comprising a rotor and a stator, wherein the rotor comprises a plurality of rotor poles and the stator comprises a plurality of phases, wherein each respective phase occupies at least one elementary block, each elementary block of each phase comprises a set of conductors of the respective phase wound around a plurality of slots of the respective elementary block in a concentrated winding configuration, wherein the stator further comprises at least one sensor located between two elementary blocks, the at least one sensor being configured to measure at least one parameter of the rotor.

[0006] Thus, the concentrated windings for each phase of the stator are grouped together in at least one block, with at least one sensor for measuring a rotor parameter integrated in the stator between two of the blocks. Arranging the sensor in this way eliminates the need to provide a sensor on the rotating armature of the rotor itself and helps to reduce the overall weight and cost of the motor.

[0007] The at least one sensor can be configured to measure an angular position of the rotor. The at least one sensor can be configured to measure a temperature of the rotor.

[0008] The at least one sensor can comprise at least one sensor coil wound around the pair of adjacent slots. Thus, the stator is provided with at least two additional slots dedicated to the sensor coil. By arranging the sensor coil in a separate grouped slot, the performance of the sensor coil can be protected from interference from the phase windings. Typically, the sensor coil pitch, i.e. the angle between the two sensor slots, will be less than the angle between adjacent poles of the rotor to obtain the required sinusoidal waveform.

[0009] The motor can further comprise at least one power electronics module for processing the electrical output of the concentrated windings, wherein the at least one power electronics module is electrically connected to the conductors of at least one of the plurality of phases, and wherein the at least one sensor coil is electrically connected to the power electronics module of the motor. That is, the sensor coil can be connected to one of the power electronics modules for processing the output of the windings. In this regard, each phase can have its own separate power electronics module, or the plurality of phases can be connected to the same power electronics module. The power electronics module of each stator module can be configured to convert direct current power to alternating current power. For example, the power electronics module can comprise an inverter.

[0010] The at least one sensor coil can be arranged to measure an angular position of the rotor based on a voltage induced therein. That is, the voltage measured at the terminals of the sensor coil is indicative of the rotor position. In this regard, the voltage induced in the coil is dependent on the mechanical position of the sensor coil relative to the phase winding (i.e. the mechanical angle between the sensor slot and the slot of the adjacent phase winding), the total number of stator slots and rotor poles, the number of elementary blocks, and the rotor position. Since all other variables are fixed and known, the variation in induced voltage can be used to determine the angular position as the rotor rotates.

[0011] The at least one sensor coil can also be arranged to measure a temperature of the rotor based on a voltage induced therein. In this regard, a change in back-EMF induced in the sensor coil is indicative of a change in temperature of the rotor magnet.

[0012] A first mechanical displacement angle between the sensor coil and the adjacent elementary block can be greater than a rotor pole pitch, which is the angle between adjacent poles of the rotor. This helps to ensure that the sensor coil does not interfere with the performance of the phase winding.

[0013] The second mechanical displacement angle between respective concentrated windings of each pair of adjacent elementary blocks can be less than the rotor pole pitch. That is, the elementary blocks are mechanically displaced together such that they are separated by small stator teeth in order to leave sufficient space for the sensors, while still maintaining the required electrical displacement between phases. At the same time, the stator slot pitch can be equal to the rotor pole pitch in order to maximize the flux linkage between the rotor poles and each phase coil, thereby providing a unity winding factor, which in turn results in a more efficient machine.

[0014] The second mechanical displacement angle can be approximately two-thirds of the rotor pole pitch. This ensures that the forced electrical displacement between phases is maintained, which is 120° for a three-phase machine.

[0015] The stator can comprise two sensors. Such an arrangement provides redundancy and fault tolerance, i.e. if one sensor fails, the operation of the second sensor is not affected. This is important when the sensors are used to monitor the rotor position in order to control the machine.

[0016] In some cases, each of the two sensors comprises a sensor coil wound around the paired adjacent slots.

[0017] The two sensors can comprise a first sensor at a first position on the stator and a second sensor at a second position on the stator. For example, the first and second positions are diametrically opposed. Alternatively, the first position can be adjacent to the second position.

[0018] The two sensors can comprise a first sensor coil and a second sensor coil, the first and second sensor coils being wound around the paired mutually adjacent slots. That is, the two sensor coils are wound around the same pair of slots.

[0019] The rotor can comprise a plurality of permanent magnets.

[0020] Each phase can comprise two elementary blocks connected by a single end conductor. In this case, each phase can be divided into two diametrically opposed regions which act to balance the forces of the rotor, thereby reducing vibration and noise levels. Furthermore, the two elementary blocks of each phase can be configured to provide separate power channels which act independently of each other, which is useful for implementing fault tolerance conditions in which if one power channel fails, the other channel is able to continue to operate at full power. In this case, the stator can comprise two diametrically opposed sensors, each corresponding to one power channel. This is also important for redundancy and fault tolerance, i.e. if one sensor fails, the operation of the second sensor is not affected.

[0021] In some arrangements, the stator can comprise three phases.

[0022] Another aspect of the present application provides an aircraft propulsion system comprising an electric machine according to any of the preceding claims. BRIEF DESCRIPTION OF DRAWINGS

[0023] Other features and advantages of the present application will become apparent from the following description of embodiments of the application, given by way of example only, and with reference to the accompanying drawings in which:

[0024] Figure 1 is a schematic diagram illustrating an electric machine according to the present application;

[0025] Figure 2 is another schematic diagram illustrating an electric machine according to the present application;

[0026] Figure 3 is a schematic diagram illustrating a part of an electric machine according to the present application;

[0027] Figure 4 is another schematic diagram illustrating a part of an electric machine according to the present application;

[0028] Figure 5 is another schematic diagram illustrating an electric machine according to the present application;

[0029] Figure 6 is a schematic diagram illustrating an output of an electric machine according to the present application;

[0030] Figure 7 is another schematic diagram illustrating an output of an electric machine according to the present application;

[0031] Figure 8 is another schematic diagram illustrating an output of an electric machine according to the present application;

[0032] Figure 9 is another schematic diagram illustrating an output of an electric machine according to the present application;

[0033] Figure 10 is another schematic diagram illustrating an electric machine according to the present application;

[0034] Figure 11 is another schematic diagram illustrating an output of an electric machine according to the present application;

[0035] Figure 12 is another schematic diagram illustrating an electric machine according to the present application;

[0036] Figure 13 is another schematic diagram illustrating an electric machine according to the present application;

[0037] Figure 14 is another schematic diagram illustrating an electric machine according to the present application;

[0038] Figure 15 is another schematic view showing an electric machine according to the present application;

[0039] Figure 16 is another schematic view showing an electric machine according to the present application;

[0040] Figure 17 is a schematic view of an aircraft propulsion system comprising an electric machine according to the present application. DETAILED DESCRIPTION

[0041] Figure 1 A three-phase electric machine 100 according to the present application is shown, comprising a rotor 102 and a stator 108. The rotor 102 comprises a rotating part 104, preferably in the form of a ferromagnetic back iron, surrounded by an array of permanent magnets 106 distributed around its periphery. The electric machine 100 has a number of poles equal to the number of permanent magnets 106 on the rotor 102. The outer circumferential distance between the centers of two adjacent poles, i.e. the angle between two adjacent rotor magnets 106, is referred to as the rotor pole pitch.

[0042] In particular, the rotor pole pitch τ p is calculated as:

[0043]

[0044] where:

[0045] 2p is the total number of poles of the rotor.

[0046] Here, it is understood that p refers to the number of pole pairs. In Figure 1 the example shown, the rotor 102 comprises 44 permanent magnets 106, i.e. a total number of poles of 44.

[0047] The stator 108 comprises a magnetic stator core 110 and a plurality of longitudinal slots 112, evenly distributed around the periphery of the stator 108 and extending through the stator core 110 in the direction of the longitudinal axis. In Figure 1In the example shown, the stator 108 comprises 42 slots 112. The stator 108 also comprises a plurality of concentrated windings for each of the three phases (denoted A, B and C). For each phase, the windings are grouped such that a plurality of conductors 114 are wound around the slots 112 to form two fundamental blocks 116A-116F of concentrated windings, each slot 112 being configured to receive a coil of conductors 114, known as a single layer winding, comprising at least one conductor 114 in each slot 112. However, the skilled person will appreciate that the same concept can be extended to a double layer winding arrangement, where the slots of the stator are configured to receive two coils of conductors 114. In the present example, the conductors 114 for phase A are wound around the slots 112 in blocks labelled 116A and 116D, the conductors 114 for phase B are wound around the slots 112 in blocks labelled 116B and 116E, and the conductors 114 for phase C are wound around the slots 112 in blocks labelled 116C and 116F. Thus, in this example, each phase is split into two diametrically opposed regions, which in turn has the effect of balancing the forces of the rotor 102, thereby reducing vibration and noise levels. Similarly, the two different regions of each phase can be used to provide separate power channels that act independently of one another. This is important for redundancy and to enable fault tolerant conditions, where if one power channel fails, the other power channel is also able to continue to operate at full power.

[0048] Within each fundamental block 116A-116F, the slots 112 are separated by a plurality of stator teeth 118 of a first size, such that the inter-slot pitch τ s , the angle between adjacent slots 112 is equal to the rotor pole pitch τ p , as shown. This helps to ensure that the total magnetic flux generated from the rotor 102 is maximised with the linking of the coils formed by the windings in the stator 108, i.e. the flux linkage, and thus the winding factor is equal to one. It is not possible to achieve this perfect alignment with conventional concentrated windings, and thus the winding factor will always be less than one. Figure 2

[0049] The fundamental blocks 116A-116F of the windings are mechanically shifted together such that at least a portion of the fundamental blocks 116A-116F are separated by small stator teeth 120 of a second size. Thus, the inter-slot pitch τ sn between the end slots 112 of adjacent portions of the fundamental blocks 116A-116F is equal to two-thirds of the rotor pole pitch τ p , which ensures that the mandatory electrical shift between phases is maintained, which for a three-phase machine is 120°. In Figure 1 and Figure 2 ​In the example, basic blocks 116A-116C are mechanically shifted together, such that there are small stator teeth 120 between blocks 116A and 116B, and between blocks 116B and 116C. Similarly, basic blocks 116D-116F are mechanically shifted together, such that there are small stator teeth 120 between blocks 116D and 116E, and between blocks 116E and 116F.

[0050] By arranging the base blocks 116A-116F in this manner, two spaces are created within the stator core 110 in which static position sensors 122A-122B are mounted. However, those skilled in the art will understand that the base blocks can be arranged to provide space for only one position sensor, as described in the example below. In this example, each position sensor 122A-122B includes a sensor coil 124 wound around a pair of slots 126A-B. Those skilled in the art will understand that the slots 126A-B in which the sensor coil 124 is located can have the same, similar, or different shapes and dimensions (e.g., height and width) as the slots of the main phase winding 112. The first position sensor 122A is located between base blocks 116A (phase A) and 116F (phase C), while the second position sensor 122B is located between base blocks 116C (phase A) and 116D (phase C).

[0051] Arranging the motor 100 in this way allows one or more sensors 122A, 122B to be integrated into the stator core 110, eliminating the need to place sensors on the rotating armature of the rotor 108 itself, thereby helping to reduce the overall weight and cost of the motor 100.

[0052] like Figure 5 As shown, these position sensors 122A, 122B can then be connected to the power electronics 130A-130B of the motor 100 and used to monitor the position and temperature of the rotor 102 based on the voltage sensed at its terminals, as will be described in more detail below. Figure 5In the example shown, each position sensor 122A, 122B is connected to the same power electronics module 130A, 130B, such as an inverter, which is used to convert the direct current of the main phase winding into alternating current. In the present example, the first position sensor 122A is connected to a first inverter 130A which is connected to a first set of windings of each phase, denoted as phases Al, Bl and Cl. This corresponds to one power channel. The second position sensor 122B is connected to a second inverter 130B which is connected to a second set of windings of each phase, denoted as phases A2, B2 and C2. This corresponds to a second power channel. Thus, each inverter 130A, 130B has a dedicated position sensor 122A, 122B which is important for redundancy and fault tolerance. In this regard, if one position sensor fails, the operation of the second sensor is not affected and thus control of the machine can be maintained. In particular, a machine having six fundamental blocks (n = 6) and two diametrically opposed position sensors, as in the present example, provides a balanced radial magnetic pull required to improve the machine noise and vibration behavior. Furthermore, since the sensor coil 124 is wound around its own slot 126A-B, its performance is not interfered or disturbed by the main phase windings.

[0053] While two sets of power electronics modules 130A, 130B are shown in the above example, any suitable number can of course be used. For example, each winding of a fundamental block can be connected to a separate power electronics device.

[0054] The sensor coil 124 is designed to obtain a required amplitude and waveform quality of the voltage induced at its terminals. In this regard, the main features of the sensor coil 124 are the number of turns N tr and the sensor coil pitch τ sc As shown in Figure 3 and Figure 4 In the case of two sensors as in the present example, it will be appreciated that the sensor coils 124 can have different features. For example, two sensor coils 124 can be provided, each having a different number of turns to provide two different voltages, one providing a high voltage and the other a low voltage. One benefit of being able to adapt the features of the sensor coils is that the sensor coils, for example the coil with the higher voltage, can provide a small amount of power to the power electronics device while providing its sensing function.

[0055] By knowing the mechanical position of the sensor coil 124 relative to the magnetic field axis of the adjacent phase winding, i.e. the angle θ s-ph As shown in Figure 3 and Figure 4The illustrated, and the voltage at the terminals of the sensor winding 124, enables accurate determination of the rotor position.

[0056] In this regard, the rotor position θ r and the voltage V coil induced in the sensor coil 124 can be calculated by the following equation:

[0057]

[0058]

[0059] where:

[0060] V pk is the amplitude of the induced voltage;

[0061] f is the electrical frequency;

[0062] p is the number of pairs of poles;

[0063] N s is the number of stator slots containing phase windings;

[0064] n is the number of elementary blocks; and

[0065] t is time.

[0066] The amplitude of the voltage induced at the terminals of the sensor coil 124 can be further calculated as:

[0067]

[0068] where:

[0069] Ω is the rotational speed;

[0070] N tr is the number of turns of the sensor coil;

[0071] Φ pk is the peak value of the fundamental of the flux seen by the coil; and

[0072] k w is the winding factor.

[0073] The winding factor k w may be further defined as follows:

[0074]

[0075] where τ sc-p is the sensor coil spacing per element, also referred to as the coil span per element, defined as:

[0076]

[0077] According to equations [4]-[6], the amplitude of the induced voltage is proportional to the coil spacing τ sc-p Closely related, as Figure 6 shown, the harmonic content of the voltage waveform is closely related to the coil span, and thus any particular harmonic can be eliminated or highly mitigated by choosing a particular τ sc-p In this regard, it is generally easier to monitor a pure sinusoidal waveform with only one fundamental, and thus it is advantageous to be able to adjust the characteristics of the sensor coil 124 to obtain a preferred waveform. For example, as Figure 7 shown, a τ sc-p equal to 2 / 3 pu eliminates the third harmonic.

[0078] As Figure 8 shown, the voltage induced in the sensor coil 124 as the rotor magnets 106 rotate can be used to accurately determine the position of the rotor 102. As defined by equations [2]-[4], the voltage waveform is indicative of the rotational speed and position of the rotor 102. Given the time, the number of rotor pole pairs, the number of slots in the stator, and the position of the sensor relative to the main phase winding, the position of the rotor 102 within the stator 104 can be determined. For example, at a first position (a) at t = 1 s, two rotor magnets 106A and 106B are directly below the sensor slots 126A and 126B, respectively, resulting in an induced voltage of 1 pu. As the rotor magnets 106 rotate to a second position (b) such that one rotor magnet 106B is positioned directly in line with the sensor coil 124, the induced voltage drops to 0 pu. As the rotor magnets 106 continue to rotate to a third position (c) and then to a fourth position (d), the induced voltage continues to oscillate accordingly, such that it can be mapped to a particular rotor position.

[0079] In addition to the rotor position, the voltage measured at the terminals of the sensor coil 124 can also be used to indicate the temperature of the rotor magnets. As described above in equation [4], the amplitude of the induced voltage in the sensor coil 124 is proportional to the rotational speed and the linking flux generated by the rotor magnets 106. This linking flux is closely related to the residual flux density Br of the array of permanent magnets 106, which is closely related to the operating temperature of the rotor 102. The higher the temperature of the magnets, the lower the residual inductance Br of the magnets, and the lower the induced voltage in the sensor coil, as Figure 9 shown. Thus, by measuring the drop in back-EMF at the terminals of the sensor coil 124, the drop in residual inductance Br can be determined, and thus the temperature of the rotor magnets can be determined.

[0080] In this regard, the temperature dependence of the magnet residual inductance is defined as follows:

[0081] B r (T) = B r20℃ (1 + a(T - 20°C)) [7]

[0082] where:

[0083] For SmCo,

[0084] For NdFeB,

[0085] Here, SmCo and NdFeB are two common rare-earth alloy magnets used in permanent magnet electric machines. However, it will be appreciated that any suitable magnetic material can be used, and an appropriate value of a can be used in each case to determine temperature from residual inductance.

[0086] In order to obtain a viable electric machine with at least one position sensor integrated to the stator core, the number of slots N s and the number of poles 2p must satisfy a set of conditions.

[0087] For electric machines with three basic phase winding blocks, n = 3:

[0088] If N s is even: N s = 2p-i

[0089] where i = 0, 2, 4,...

[0090] If N s is odd: N s = 2p-i

[0091] where i = 1, 3, 5,...

[0092] For electric machines with six basic phase winding blocks, n = 6:

[0093] Ns= 2p-i

[0094] where i = 0, 2, 4,...

[0095] Preferably, the space allocated to the position sensor is minimized so that the number of slots N s is as close as possible to the number of poles 2p.

[0096] Examples of the above viable electric machines will now be described.

[0097] Figure 10 A first example is given which shows an electric machine 200 where n = 6, Ns= 42, and 2p= 44. As before, the electric machine 200 comprises a rotor 202 and a stator 208. The rotor 202 comprises a rotating member 204, preferably in the form of a ferromagnetic back iron, surrounded by an array of permanent magnets 206 distributed around its periphery. As above, Figure 10 The electric machine 200 has 44 permanent magnets 206.

[0098] The stator 208 includes a magnetic stator core 210 and a plurality of longitudinal slots 212. The longitudinal slots 212 are evenly distributed around the periphery of the stator 208 and extend through the stator core 210 along the longitudinal axis. As described above, the stator 208 includes 42 slots 212. The stator 208 also includes a plurality of concentrated windings for each of the three phases (denoted as A, B, and C), as shown in... Figure 10 The winding layout 228 is further illustrated. For each phase, the winding is divided into two basic blocks 216A-216F such that multiple conductors 214 are wound around slots 212 to form a concentrated winding, each slot 212 being configured to receive a conductor 214. In this example, the conductors 214 of phase A are wound around slots 212 in blocks labeled 216A and 216D, the conductors 214 of phase B are wound around slots 212 in blocks labeled 216B and 216E, and the conductors 214 of phase C are wound around slots 212 in blocks labeled 216C and 216F.

[0099] Within each basic block 216A-216F, slot 212 is separated by a plurality of stator teeth 218 of the first size, such that the slot spacing τ s That is, the angle between adjacent slots 212 is equal to the rotor pole spacing τ. p In this example, base blocks 216A-216F are mechanically shifted together to create space in which a single position sensor 222 can be placed. In this example, small stator teeth 220 are respectively disposed between base blocks 216A and 216B, 216B and 216C, 216C and 216D, 216D and 216E, and 216E and 216F, with the position sensor 222 located between base blocks 216A and 216F. As previously described, the position sensor 222 includes a sensor coil 224 wound around paired slots 226A-B.

[0100] Figure 11 Further illustrations show the use Figure 10 The temperature dependence of the back electromotive force of the sensor coil measured by position sensor 222. Figure 11 The voltage of sensor coil 224 at ambient temperature (T = 20°C) and at temperatures above 20°C are shown. It can be seen here that the back electromotive force of sensor coil 224 decreases as the temperature increases.

[0101] Figure 12 and Figure 13 Another example of a feasible motor is provided, which shows motor 300, where n = 6, N s= 36, and 2p = 36. As before, the electric machine 300 includes a rotor 302 and a stator 308. The rotor 302 includes a rotating member 304, preferably in the form of a ferromagnetic back iron, surrounded by an array of permanent magnets 306 distributed around its periphery. As before, Figure 12 and Figure 13 The electric machine 300 has 36 permanent magnets 306.

[0102] The stator 308 includes a magnetic stator core 310 and a plurality of longitudinal slots 312 evenly distributed around the periphery of the stator 308 and extending through the stator core 310 in the direction of the longitudinal axis. As before, the stator 308 includes 36 slots 312. The stator 308 also includes a plurality of concentrated windings for each of three phases, denoted A, B, and C, as further shown in the winding layout 328. For each phase, the windings are grouped so that a plurality of conductors 314 are wound around the slots 312 to form two fundamental blocks 316A-316F of concentrated windings, each slot 312 configured to receive a conductor 314. In this example, the conductors 314 for phase A are wound around the slots 312 in blocks labeled 316A and 314D, the conductors 314 for phase B are wound around the slots 312 in blocks labeled 316B and 316E, and the conductors 414 for phase C are wound around the slots 312 in blocks labeled 316C and 316F. Figure 12

[0103] Within each fundamental block 316A-316F, the slots 312 are separated by a plurality of stator teeth 318 of a first size, such that the slot pitch τ s , the angle between adjacent slots 312, is equal to the rotor pole pitch τ p In this example, the fundamental blocks 316A-316F are mechanically shifted together to create two spaces in which position sensors 322A-322B can be placed. In this example, small stator teeth 320 are provided between the fundamental blocks 316B and 316C, 316C and 316D, 316E and 316F, and 316F and 316A, respectively, a first position sensor 222A is located between the fundamental blocks 316A and 316B, and a second position sensor 222B is located between the fundamental blocks 316D and 316E. As before, the position sensors 322A, 322B each include a sensor coil 324 wound around a pair of slots 326A-B.

[0104] Figure 14 An example of an electric machine 400 is provided in which n = 3, N s = 15, and 2p = 16. As before, the electric machine 400 includes a rotor 402 and a stator 408. The rotor 402 includes a rotating member 404, preferably in the form of a ferromagnetic back iron, surrounded by an array of permanent magnets 406 distributed around its periphery. As before,​Figure 14 The electric machine 400 has 16 permanent magnets 406.

[0105] The stator 408 includes a magnetic stator core 410 and a plurality of longitudinal slots 412 that are evenly distributed around the circumference of the stator 408 and extend through the stator core 410 in the direction of the longitudinal axis. As noted above, the stator 108 includes 15 slots 412. The stator 408 also includes a plurality of concentrated windings for each of three phases, denoted A, B, and C, as further shown in the winding layout 428. For each phase, the windings are grouped such that a plurality of conductors 414 are wound around the slots 412 to form individual elementary blocks 416A-416C of concentrated windings, each slot 412 being configured to receive a conductor 414. In the present example, the conductors 414 for phase A are wound around the slots 412 in the elementary blocks labeled 416A, the conductors 414 for phase B are wound around the slots 412 in the elementary blocks labeled 416C, and the conductors 414 for phase C are wound around the slots 412 in the elementary blocks labeled 416C. Figure 14

[0106] Within each elementary block 416A-416C, the slots 412 are separated by a plurality of stator teeth 418 of a first size such that the inter-slot pitch τ s , the angle between adjacent slots 412, is equal to the rotor pole pitch τ p In the present example, the elementary blocks 416A-416C are mechanically shifted together to create space in which a single position sensor 422 can be placed. In the present example, small stator teeth 420 are disposed between the elementary blocks 416A and 416C and 416B and 416C, respectively, and the position sensor 422 is located between the elementary blocks 416A and 416B. As noted previously, the position sensor 422 includes a sensor coil 424 that is wound around the pair of slots 426A-B.

[0107] Figure 15 Another example of an electric machine 500 according to the present application is shown, where n = 6, N s = 42, and 2p = 44. As noted previously, the electric machine 500 includes a rotor 502 and a stator 508. The rotor 502 includes a rotating member 504, preferably in the form of a ferromagnetic back iron, that is surrounded by an array of permanent magnets 506 that are distributed around the circumference thereof. As noted above, Figure 15 The electric machine 500 has 44 permanent magnets 506.

[0108] ​The stator 508 includes a magnetic stator core 510 and a plurality of longitudinal slots 512, which are evenly distributed around the periphery of the stator 508 and extend through the stator core 510 along the longitudinal axis. As described above, the stator 508 includes 42 slots 512. The stator 508 also includes a plurality of concentrated windings for each of the three phases (denoted as A, B, and C), as shown in... Figure 15 The winding layout 528 is further illustrated. For each phase, the winding is divided into two basic blocks 516A-516F such that multiple conductors 514 are wound around slots 512 to form a concentrated winding, each slot 512 being configured to receive a conductor 514. In this example, the conductors 514 of phase A are wound around slots 512 in blocks labeled 516A and 516D, the conductors 514 of phase B are wound around slots 512 in blocks labeled 516B and 516E, and the conductors 514 of phase C are wound around slots 512 in blocks labeled 516C and 516F.

[0109] Within each basic block 516A-516F, slot 512 is separated by a plurality of stator teeth 518 of the first size, such that the slot spacing τ s That is, the angle between adjacent slots 512 is equal to the rotor pole spacing τ. p In this example, base blocks 516A-516F are mechanically shifted together to create a single space in which position sensor 522 can be placed. Therefore, small stator teeth 520 are arranged between base blocks 516A and 516B, 516B and 516C, 516C and 516D, 516D and 516E, and 516E and 516F, with position sensor 522 located between base blocks 516A and 516F. However, in this case, position sensor 522 comprises two sensor coils 524A-524B wound around paired slots 526A-B. Each sensor coil 524A, 524B will be connected individually to effectively set up two position sensors. That is, position sensor 522 will output two separate voltage measurements. As discussed earlier, this facilitates fault-tolerant control of motor 500.

[0110] Figure 16 Another example of a motor 600 according to the invention is shown, where n = 6, N s =42, and 2p=44. As previously described, the motor 600 includes a rotor 602 and a stator 608. The rotor 602 includes a rotating component 604, preferably in the form of a ferromagnetic back iron, the rotating component 604 being surrounded by an array of permanent magnets 606 distributed around its periphery. As described above, Figure 16 The motor 600 has 44 permanent magnets 606.

[0111] The stator 608 includes a magnetic stator core 610 and a plurality of longitudinal slots 612 evenly distributed around the circumference of the stator 608 and extending through the stator core 610 in the direction of the longitudinal axis. As noted above, the stator 608 includes 42 slots 612. The stator 608 also includes a plurality of concentrated windings for each of the three phases, denoted A, B, and C, as further shown in the winding layout 628. For each phase, the windings are grouped such that a plurality of conductors 614 are wound around the slots 612 to form two fundamental blocks 616A-616F of concentrated windings, with each slot 612 configured to receive a conductor 614. In the present example, the conductors 614 for phase A are wound around the slots 612 in blocks labeled 616A and 614D, the conductors 614 for phase B are wound around the slots 612 in blocks labeled 616B and 616E, and the conductors 614 for phase C are wound around the slots 612 in blocks labeled 616C and 616F. Figure 16

[0112] Within each fundamental block 616A-616F, the slots 612 are separated by a plurality of stator teeth 618 of a first size such that the slot pitch τs s , the angle between adjacent slots 612, is equal to the rotor pole pitch τr p In the present example, the fundamental blocks 616A-616F are mechanically shifted together to create a single space in which both position sensors 622A-622B can be placed. Accordingly, small stator teeth 620 are provided between the fundamental blocks 616A and 616B, 616B and 616C, 616D and 616E, 516E and 616F, and 616F and 616A, respectively, with the position sensors 622A, 622B positioned in series between the fundamental blocks 616C and 616D. As previously noted, each position sensor 622A, 622B includes a sensor coil 624 wound around a pair of slots 626A-B. As previously discussed, this facilitates providing fault-tolerant control for the electric machine 500.

[0113] Figure 17 An example of an all-electric or hybrid-electric aircraft propulsion system 700 is shown, including an electric machine 702 as described herein. The electric machine 702 includes a stator 704 and a rotor 706 according to the arrangements described above. In this regard, the stator 706 is configured such that the coils corresponding to each phase are arranged in fundamental blocks, positioned to allow for integration of position sensor coils into the stator core. The electric machine 702 is connected to an aircraft propeller 708 by way of a rotating shaft 710, with the electric motor 702 driving the shaft 710 to thereby drive the propeller 708.

[0114] ​In the context of all-electric or hybrid-electric aircraft, the electric machines described herein can be used in propulsion systems in which an electric motor drives the propulsors of the aircraft by converting electrical power into mechanical power (torque), the electrical power being provided by a turbine-shaft-driven generator or by a battery.

[0115] Various modifications can be made to all above-described embodiments in order to provide further embodiments, where any and / or all embodiments will be encompassed by the appended claims.

Claims

1. An electric machine for use in an aircraft, comprising: a rotor, wherein the rotor comprises a plurality of rotor poles; and a stator comprising a plurality of phases, wherein each respective phase occupies at least one fundamental block, the at least one fundamental block of each phase comprising a set of conductors of the respective phase wound in a concentrated winding configuration around a plurality of slots of the respective fundamental block; wherein the stator further comprises at least one sensor located between two fundamental blocks, the at least one sensor configured to measure at least one parameter of the rotor, wherein the at least one sensor comprises at least one sensor coil wound around a pair of adjacent slots.

2. The electric machine of claim 1, wherein, the at least one sensor is configured to measure an angular position of the rotor.

3. The electric machine of claim 1, wherein, the at least one sensor is configured to measure a temperature of the rotor.

4. The electric machine of claim 1, wherein, the electric machine further comprises at least one power electronics module for processing an electrical output of the concentrated winding, wherein the at least one power electronics module is electrically connected to a conductor of at least one phase of the plurality of phases, and wherein the at least one sensor coil is electrically connected to the power electronics module of the electric machine.

5. The electric machine of claim 1, wherein, the at least one sensor coil is arranged to measure an angular position of the rotor based on a voltage induced therein.

6. The electric machine of claim 1, wherein, the at least one sensor coil is arranged to measure a temperature of the rotor based on a voltage induced therein.

7. The electric machine of claim 1, wherein, a first mechanical displacement angle between the sensor coil and an adjacent fundamental block is greater than a rotor pole pitch, the rotor pole pitch being an angle between adjacent rotor poles.

8. The electric machine of claim 7, wherein, a second mechanical displacement angle between respective concentrated windings of each pair of adjacent fundamental blocks is less than the rotor pole pitch.

9. The electric machine of claim 8, wherein, the second mechanical displacement angle is two-thirds of the rotor pole pitch.

10. The electric machine of claim 1, wherein, the stator comprises two sensors.

11. The electric machine of claim 10, wherein, each of the two sensors comprises a sensor coil wound around a pair of adjacent slots.

12. The electric machine of claim 10, wherein, the two sensors comprise a first sensor located at a first position on the stator and a second sensor located at a second position on the stator.

13. The electric machine of claim 12, wherein, the first position and the second position are diametrically opposed.

14. The electric machine of claim 12, wherein, the first position is adjacent to the second position.

15. The electric machine of claim 10, wherein, the two sensors comprise a first sensor coil and a second sensor coil wound around a pair of mutually adjacent slots.

16. The electric machine of claim 1, wherein, the rotor comprises a plurality of permanent magnets.

17. The electric machine of claim 1, wherein, each phase comprises two fundamental blocks connected by a single end conductor.

18. The electric machine of claim 1, wherein, the stator comprises three phases.

19. An aircraft propulsion system comprising the electric machine of any one of claims 1 to 18.

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