Rotating electrical machine

Abstract

An SPM-type multiple three-phase synchronous rotating electrical machine (1) for an aircraft comprises a stator (2), a rotor (3), and a plurality of power converters. The stator (2) has a plurality of slots (8) in which coils (11) are housed. The rotor (3) has a rotor shaft (3S) that is directly connected to a rotary shaft of an aircraft engine, and a plurality of permanent magnets (5). The power converters control the energy of the rotating electrical machine (1). The plurality of permanent magnets (5) are positioned at the outer circumference of the rotor (3) such that a plurality of magnetic poles are formed in the circumferential direction. Each permanent magnet (5) is divided into a plurality of segments in the axial direction. The plurality of slots (8) are formed in the stator (2) in the circumferential direction, and the winding of the coils (11) into the plurality of slots (8) is a short pitch winding and a two-layer distributed winding.

Description

rotating electrical machines

[0001] The present disclosure relates to an SPM-type multiple three-phase synchronous rotating electrical machine for an aircraft.

[0002] In addition to engines such as gas turbine engines that serve as propulsion devices, aircraft are equipped with generators that supply power to the aircraft's electrical systems. The generators generate electricity using a portion of the engine output. Patent Document 1 listed below discloses such a power generation system for aircraft. In recent years, demand for onboard electricity has been increasing due to demands for aircraft electrification (More Electric Aircraft (MEA)) and the like.

[0003] Japanese Patent Application Laid-Open No. 2006-153013

[0004] The demand for electric power on board aircraft is expected to continue to increase. Therefore, generators and motors, i.e., rotating electrical machines, installed on aircraft are required to have higher power density while also being smaller and lighter. However, various constraints arise when they are installed on aircraft. For example, in addition to the high power density that accompanies the aforementioned compactness and lightness, vibration resistance must also be ensured. Furthermore, the operating voltage cannot be made too high due to factors such as the increased likelihood of electrical discharge at low atmospheric pressures at high altitudes.

[0005] Rotating electric machines have an operating voltage range that is technically easy to manufacture relative to the required output, i.e., capacity. If the required output is small but the voltage is high, or if the required output is large but the voltage is low, optimization in terms of efficiency and power factor is impossible, and it is difficult to achieve high power density through miniaturization and weight reduction. This can also increase manufacturing costs. Considering the required output of megawatts, it is technically relatively easy to adopt an operating voltage of several kilovolts. However, considering the operation under the above-mentioned low atmospheric pressure, operation at several kilovolts is difficult. Taking these various performance requirements and constraints into consideration, the inventors have investigated and developed a rotating electric machine that can meet the requirements of the above-mentioned MEA.

[0006] The present disclosure has been made in consideration of the above circumstances, and has an object to provide a rotating electric machine that can increase the power density.

[0007] The present disclosure provides an SPM-type multiple three-phase synchronous rotating electric machine for an aircraft, comprising: a rotor shaft directly connected to the rotating shaft of an aircraft engine; a rotor having a plurality of permanent magnets; a stator having a plurality of slots in which coils are housed; and a plurality of power converters for controlling the energy of the rotating electric machine. The plurality of permanent magnets are arranged on the outer periphery of the rotor so as to form a plurality of magnetic poles in the circumferential direction, and each of the plurality of permanent magnets is divided into a plurality of segments in the axial direction. The stator has a plurality of slots formed in the circumferential direction, and the coils are wound in the plurality of slots with fractional pitch winding and two-layer distributed winding.

[0008] The rotor may further have a sleeve that holds the multiple permanent magnets from the radially outer side, the sleeve being divided into multiple segments in the axial direction, and the number of divisions of the sleeve may be equal to or greater than the number of divisions of the permanent magnets.

[0009] When the air gap between the rotor and the stator is G and the radius of the rotor is R, G / R may be equal to or greater than 0.020 and equal to or less than 0.031.

[0010] The plurality of power converters may be two power converters, the plurality of permanent magnets may be arranged on the outer periphery of the rotor so as to form eight magnetic poles in the circumferential direction, the plurality of slots may be 48 slots, and for each of the two power converters, eight coils of each phase may be electrically connected in parallel.

[0011] The ratio of the short side to the long side in a cross section of the rectangular wire of the coil may be 0.125 or more and 0.310 or less.

[0012] According to the rotating electric machine according to the present disclosure, it is possible to increase the power density as a rotating electric machine for an aircraft.

[0013] FIG. 1 is a cross-sectional view of a stator and a rotor of a rotating electric machine according to an embodiment. FIG. 2 is a schematic diagram of the rotating electric machine. FIG. 3 is a partially cross-sectional perspective view of the rotor of the rotating electric machine. FIG. 4A is a connection circuit diagram of each phase coil of the stator, FIG. 4B is a connection circuit diagram for 72 slots, and FIG. 4C is a connection circuit diagram for 96 slots. FIG. 5A is a partial cross-sectional view of a stator showing another example of a two-layer distributed coil winding pattern. FIG. 5B is a partial cross-sectional view of a stator showing yet another example of a two-layer distributed coil winding pattern. FIG. 6A is a partial cross-sectional view of a stator with 72 slots. FIG. 6B is a partial cross-sectional view of a stator with 96 slots. FIG. 7A is a distribution diagram of coil current density for 48 slots. FIG. 7B is a distribution diagram of coil current density for 72 slots. FIG. 7C is a distribution diagram of coil current density for 96 slots. FIG. 8A is a graph showing the relationship between rotor loss and the number of divisions of the rotor's permanent magnets and sleeves. FIG. 8B is a graph showing the relationship between the number of divisions and the efficiency of the rotating electrical machine.

[0014] Hereinafter, an SPM type multiple three-phase synchronous rotating electric machine 1 for an aircraft according to an embodiment will be described with reference to the drawings. Here, the rotating electric machine 1 will be described as functioning as a generator, but the rotating electric machine 1 can also function as an electric motor.

[0015] As shown in FIG. 2 , the rotating electric machine 1 of this embodiment is a “dual” three-phase synchronous rotating electric machine equipped with two power converters INV1 and INV2 for controlling its energy. The power converter INV1 is connected to a UVW three-phase coil set CS1, and the power converter INV2 is connected to a UVW three-phase coil set CS2. Each of the power converters INV1 and INV2 has a three-phase inverter configuration and has a well-known circuit configuration capable of realizing two-level or multi-level voltage levels using switching elements such as thyristors, IGBTs (Insulated Gate Bipolar Transistors), or MOSFETs (Metal-Oxide-Semiconductor Field Effect Transistors). The power converters INV1 and INV2, which are three-phase inverters, are driven using PWM (Pulse-Width Modulation) control. As will be explained in detail later, the two coil sets CS1 and CS2 are built into a single stator 2. In this way, the rotating electric machine 1 is equipped with two power converters INV1 and INV2, ensuring redundancy as a rotating electric machine 1 installed on an aircraft.

[0016] As shown in FIG. 1 , a rotor 3 is disposed inside a hollow cylindrical stator 2. Eight rows of permanent magnets 5 are attached to the outer circumferential surface of a rotor core 4 of the rotor 3, arranged in a circumferential direction. The eight rows of permanent magnets 5 are arranged so that their magnetic poles, i.e., S and N poles, alternate in the circumferential direction. In other words, the rotating electric machine 1 is an SPM-type rotating electric machine. The rotor core 4 is hollow, and a rotor shaft 3S extends from both ends of the rotor core 4 along the central axis O of rotation of the rotor 3. The rotor shaft 3S is rotatably held by a housing of the rotating electric machine 1 or a casing of an aircraft engine, for example. As shown in FIG. 3 , each row of permanent magnets 5 is physically divided into multiple segments in the direction of the central axis O of rotation of the rotor 3. The number of divisions of the permanent magnets 5 in each row is typically 15 to 120. The direction of the central axis O of the rotor 3 is the direction of the rotor shaft 3S, which is also the axial direction.

[0017] The rotor 3 also has hollow cylindrical sleeves 6 on the outer circumferential surfaces of the permanent magnets 5 to prevent the permanent magnets 5 from falling off the rotor core 4 due to centrifugal force. The permanent magnets 5 are held radially outward by the sleeves 6. As shown in FIG. 3 , the sleeve 6 is also physically divided into multiple segments in the axial direction. The number of divisions of the sleeve 6 is also typically between 15 and 120. The number of divisions of the sleeve 6 is typically equal to or greater than the number of divisions of the permanent magnets 5, but in this embodiment, the two numbers are the same.

[0018] The rotor shaft 3S of the rotor 3 is directly connected to the rotating shaft of the aircraft engine. The stator 2 and rotor 3 of the rotating electric machine 1 are disposed inside the tail cone of the engine. Because the rotor 3 is directly connected to the rotating shaft of the engine, engine vibrations are directly transmitted to the rotor 3. For this reason, there are restrictions on the air gap G between the rotor 3 and the stator 2 when the rotating electric machine 1 is used for an aircraft. These restrictions will be explained in detail later.

[0019] 1, the stator core 7 of the stator 2 has 48 slots 8, i.e., 48 teeth 9. Each slot 8 accommodates a rectangular wire 10 having a square cross section that forms a coil 11, stacked radially. The rectangular wire 10 is wound around the stator core 7.

[0020] In FIG. 1, the U-phase coil 11 of the coil set CS1 ＣＳ１ and U-phase coil 11 of coil set CS2. ＣＳ２ The arrangement of the U-phase coil 11 is shown. ＣＳ１ and 11 ＣＳ２ Eight of each of the U-phase coils 11 are arranged in the circumferential direction. ＣＳ１ and 11 ＣＳ２Although controlled in a dual system, they function as a single U-phase coil 11U. As shown in FIG. 1 , the U-phase coil pitch P1 is smaller than the magnetic pole pitch P2, resulting in so-called short-pitch winding. Furthermore, two-layer winding is performed in each slot 8, and each U-phase coil 11 is wound across multiple slots 8, resulting in so-called two-layer distributed winding. Here, the two-layer wound coils 11 of each phase are offset by one slot 11 between the outer and inner layers. The VW-phase coils 11 of coil sets CS1 and CS2 are similarly arranged with their phases sequentially offset around the rotational center axis O relative to the U-phase coil.

[0021] For each of the two power converters INV1 and INV2, the eight coils for each phase are connected in parallel, as shown in FIG. 4A. Furthermore, when the air gap between the rotor 3 and the stator 2, i.e., the radial clearance, is G and the radius of the rotor 3 is R, G / R is typically 0.020 or more and 0.031 or less. Although the air gap G is not indicated by a reference symbol in the figure, it is the gap between the inner peripheral surface of the stator 2 and the inner peripheral surface of the rotor 3. Furthermore, as shown in FIG. 1, the ratio of the short side to the long side in the cross section of the rectangular wire 10 of the coil 11 is typically 0.125 or more and 0.310 or less.

[0022] Below, various specifications of the rotating electric machine 1 having the above-described configuration will be explained. As mentioned above, when a megawatt-class output is required, the operating voltage of the rotating electric machine becomes high from a manufacturing standpoint, but in this case, the operating voltage is set to approximately 800 V to 1 kV, taking into account discharge under low atmospheric pressure at high altitudes. As a result of considering various specifications under these conditions, the above-described configuration was decided.

[0023] First, regarding the winding pattern / topology of the coil 11, in addition to the present embodiment shown in FIG. 1, two-layer distributed winding patterns shown in FIGS. 5A and 5B were also considered. In both cases, 20 turns of coil are housed in each slot 8. In the pattern shown in FIG. 5A, the two-layer distributed winding coil 11 of each phase is not misaligned between the outer and inner layers. The pattern shown in FIG. 5A has the same coil pitch and magnetic pole pitch, so it is a full-pitch winding winding specification. In the pattern shown in FIG. 5B, the two-layer distributed winding coil 11 of each phase is misaligned by two slots 11 between the outer and inner layers. As a result of examining these three patterns, the total loss, including eddy current loss in the coil 11, permanent magnet 5, and sleeve 6, iron loss in the rotor core 4 and stator core 7, and copper loss in the coil 11, was the lowest with the winding pattern of the present embodiment shown in FIG. 1. Furthermore, the winding pattern of the present embodiment shown in FIG. 1 also had the highest efficiency.

[0024] Regarding the number of slots, in addition to the 48 slots of this embodiment shown in FIG. 1 , 72 slots as shown in FIG. 6A and 96 slots as shown in FIG. 6B were also considered. With the 48 slots of this embodiment shown in FIG. 1 , it is possible to electrically connect eight coils 11 for each phase in each of the two power converters INV1 and INV2 in parallel, as shown in FIG. 4A , enabling a 1-series, 8-parallel configuration. In this case, the number of turns in each coil 11 can be 10. Because of the double-layer winding, 20 turns of rectangular wire 10 can be accommodated within one slot 8. This number of turns is greater than the 72 slots and 96 slots. With 72 slots, the induced voltage increases due to the 3-series, 4-parallel configuration shown in FIG. 4B . Therefore, it was necessary to reduce the number of turns in each coil 11 to 4, as shown in FIG. 6A . Although a 2-series, 6-parallel configuration is also possible with the 72 slots, the study will focus on the 3-series, 4-parallel configuration.

[0025] In the case of 96 slots, as shown in FIG. 4C, two are connected in series and eight in parallel, resulting in 16 coils 11 for each phase of each power converter INV1 and INV2. This is twice as many as in the case of 48 slots, resulting in an increase in induced voltage. For this reason, it was necessary to reduce the number of turns in each coil 11 to six, as shown in FIG. 6B. The winding patterns in FIGS. 6A and 6B were determined through considerations similar to those for the two-layer distributed winding pattern selection for the 48-slot case described with reference to FIGS. 1, 5A, and 5B. As a result, the cross-sectional areas of the rectangular wire 10 differ between the 48-slot (FIG. 1), 72-slot (FIG. 6A), and 96-slot (FIG. 6B), and the impact of eddy current loss generated in the coils 11 differs.

[0026] Figures 7A to 7C show the current density distributions of the coil 11 with 48 slots, 72 slots, and 96 slots, respectively. In these figures, the current density increases in the cross section of the rectangular wire 10 from white to vertical hatching and grid hatching. Note that these figures do not show the current density of the stator core 7, only its shape. The output of the rotating electric machine 1 used in the current density analysis was standardized to three slot patterns for megawatt-class output, and the current density distributions in the figures were obtained using 2D-FEA (Finite Element Analysis). Eddy current loss can be compared from the current density distributions shown in Figures 7A to 7C. As mentioned above, the 48-slot configuration shown in Figure 7A allows for a larger number of turns, resulting in a thinner rectangular wire 10, which reduces eddy current loss due to leakage flux from the teeth 9.

[0027] In the case of the 96 slots shown in Figure 7C, the number of parallel coils 11 is the same as in the 48 slots, but the number of series coils is greater than in the 48 slots, resulting in a reduced number of turns. As a result, the eddy current loss in the coil 11 in the 96 slots case is approximately twice that in the 48 slots case. In the case of the 72 slots shown in Figure 7B, the number of parallel coils 11 is smaller than in the 48 slots and 96 slots case, resulting in a reduced number of turns. Therefore, in the 72 slots case, the cross-sectional area of ​​the rectangular wire 10 is larger, making eddy current loss more likely to occur. As a result, the eddy current loss in the coil 11 in the 72 slots case is approximately five times that in the 48 slots case. Based on these considerations, the 48 slots case was selected.

[0028] Here, in the case of 48 slots, the number of turns can be increased, but this results in a flatter cross-sectional shape of the rectangular wire 10. As a result of examining this cross-sectional shape, it was found that the ratio of the short side to the long side in the cross section is preferably 0.125 or more and 0.310 or less, as described above. If this ratio is less than 0.125, the rectangular wire 10 becomes too thin and easily deformed, making it difficult to manufacture the coil 11. When the rectangular wire 10 is cut into hairpin-shaped divided elements for manufacturing the coil 11, the divided elements are also easily deformed, making it difficult to manufacture the stator 2. On the other hand, if this ratio exceeds 0.310, as in the case of the 72 slots in Figure 7B and the 96 slots in Figure 7C, the ratio of the short side to the long side of the cross section of the rectangular wire 10 described above becomes large, resulting in areas with high current density and increased eddy current loss.

[0029] From the above considerations, the stator 2 with 48 slots was selected as described above. That is, 48 ​​slots was selected from the viewpoint of reducing loss in the stator 2. To reduce loss in the rotor 3, it is better to have a larger number of slots in the stator 2, but this is not necessarily desirable in terms of loss in the stator 2 itself. Therefore, in this embodiment, 48 slots were selected from the viewpoint of reducing loss in the stator 2, while the permanent magnet 5 and the sleeve 6 are divided into multiple parts to reduce loss in the rotor 3, particularly eddy current loss in the permanent magnet 5 and the sleeve 6.

[0030] Here, as a result of examining the number of divisions of the permanent magnet 5 and the sleeve 6, it was found that the number of divisions for both the permanent magnet 5 and the sleeve 6 is preferably between 15 and 120. If the number of divisions is less than 15, the axial width of each segment of the permanent magnet 5 or the sleeve 6 becomes too wide, making it difficult to obtain the effect of reducing eddy current loss. On the other hand, if the number of divisions exceeds 120, the width of each segment becomes too narrow, making it difficult to manufacture the rotor 3.

[0031] FIG. 8A shows a graph illustrating the relationship between the number of divisions of the permanent magnets 5 and sleeve 6 and the total loss in the rotor 3. FIG. 8B shows a graph illustrating the relationship between the number of divisions of the permanent magnets 5 and sleeve 6 and the efficiency of the rotating electric machine 1. Note that in FIGS. 8A and 8B, the number of divisions of the permanent magnets 5 and the number of divisions of the sleeve 6 are the same. These graphs also show the results for 72 slots and 96 slots. As can be seen from the graph in FIG. 8B, the loss reduction effect in the rotor 3 by increasing the number of divisions is more significant for 48 slots. Even for 72 slots, increasing the number of divisions does have a loss reduction effect in the rotor 3, but not as great as for 48 slots. For 96 slots, the loss reduction effect in the rotor 3 due to the increased number of slots on the stator 2 side is more dominant as described above, so increasing the number of divisions does not seem to have much of an effect on the loss reduction on the rotor 3 side.

[0032] As described above, with 48 slots, the effect of improving the efficiency of the rotating electric machine 1 by increasing the number of divisions is more pronounced, and the increased number of divisions appears to have a significant effect on reducing losses in the rotor 3. In this way, by approaching both the stator 2 and the rotor 3, an improvement in efficiency and a resulting improvement in power density have been achieved in the 48-slot SPM-type dual three-phase synchronous rotating electric machine 1.

[0033] In this embodiment, the permanent magnets 5 and the sleeve 6 are divided into the same number of parts. However, it is preferable that the number of parts divided into the sleeve 6 is equal to or greater than the number of parts divided into the permanent magnets 5. The sleeve 6 is closer to the outer periphery of the rotor 3 than the permanent magnets 5, and the influence of changes in magnetic flux from the stator 2 as the rotor 3 rotates is more pronounced on the sleeve 6 than on the permanent magnets 5. In other words, the sleeve 6 is more susceptible to eddy current loss than the permanent magnets 5. Therefore, increasing the number of parts divided into the sleeve 6 can further enhance the effect of reducing eddy current loss. Therefore, when the number of parts divided into the permanent magnets 5 and the number of parts divided into the sleeve 6 are different, the efficiency of the rotating electric machine 1 can be improved by making the number of parts divided into the sleeve 6 greater than the number of parts divided into the permanent magnets 5.

[0034] Furthermore, as a result of examining the air gap G between the stator 2 and the rotor 3, it is preferable that the ratio G / R, where G is the air gap and R is the radius of the rotor 3, be 0.020 or more and 0.031 or less, as described above. This means that G / R is 2.0% or more and 3.1% or less when considered as a percentage. Note that, in the case where the rotor 3 has a sleeve 6 as in this embodiment, the outer diameter of the rotor 3 is equal to the outer diameter of the sleeve 6. Because the rotor 3 is directly connected to the rotating shaft of the aircraft engine, a relatively wide air gap G is ensured in this embodiment. As described above, engine vibrations are directly transmitted to the rotor 3, and therefore, if the air gap G is too narrow, there is a risk of contact between the stator 2 and the rotor 3.

[0035] Furthermore, if a rotating blade inside the engine is deformed due to a bird strike or the like, the rotational balance will become unbalanced, and the vibration transmitted to the rotor 3 will increase. The lower limit of the ratio G / R described above is set taking this into consideration. Because the air gap G varies depending on the size of the rotating electric machine 1 itself, a preferable air gap G was considered as a ratio to the radius R of the rotor 3. If the ratio G / R is less than 0.020, as described above, there is a risk of contact between the stator 2 and the rotor 3, which is directly connected to the rotating shaft of the aircraft engine. On the other hand, if the ratio G / R exceeds 0.031, the air gap G becomes too wide relative to the radius R, and the efficiency of the rotating electric machine 1 will decrease.

[0036] The ratio of the inner diameter to the outer diameter of the stator 2, i.e., the stator inner / outer diameter ratio, was also considered. The outer diameter of the stator 2 is the outer diameter of the stator core 7, and its inner diameter is the inner diameter at the tips of the teeth 9. The stator inner / outer diameter ratio is preferably 0.671 or greater and 0.700 or less. Expressed as a percentage, the stator inner / outer diameter ratio is 67.1% or greater and 70.0% or less. As the value of the stator inner / outer diameter ratio increases, the radial thickness of the stator 2 decreases. The rotating electric machine 1 of this embodiment is an SPM type, and the energy that can be supplied from the rotor 3 is determined to some extent by the permanent magnets 5 attached to the rotor 3. On the other hand, the energy that can be supplied from the stator 2 can be changed by the specifications of the slots 8 and the coils 11, etc. In other words, the stator inner / outer diameter ratio reflects the characteristics of the rotating electric machine 1.

[0037] The rotating electric machine 1 of this embodiment has a low-voltage, high-current specification for megawatt-class required output due to voltage setting that takes into account operation under low atmospheric pressure. This characteristic affects the stator inner / outer diameter ratio. From this perspective, when the stator inner / outer diameter ratio is 0.671 or greater and 0.700 or less, both the efficiency and power density of the rotating electric machine 1 can be most improved. When the stator inner / outer diameter ratio is less than 0.671, the size of the rotating electric machine 1 increases, resulting in a decrease in power density. On the other hand, when the stator inner / outer diameter ratio exceeds 0.700, the coil cross-sectional area cannot be sufficiently secured, resulting in a decrease in the efficiency of the rotating electric machine 1.

[0038] The rotating electric machine 1 according to the embodiment includes a stator 2, a rotor 3, and two power converters INV1 and INV2. The power converters INV1 and INV2 control the energy of the rotating electric machine 1. The multiple power converters form a multiplexed circuit configuration, ensuring redundancy as a rotating electric machine 1 for an aircraft. The stator 2 has multiple slots 8 in which coils 11 are housed. The rotor 3 has a rotor shaft 3S directly connected to the rotating shaft of an aircraft engine and multiple permanent magnets 5. The stator has multiple slots 8 formed in the circumferential direction, and the coils 11 are wound around the slots 8 using short-pitch winding and two-layer distributed winding. This reduces loss in the stator 2 and improves the efficiency of the rotating electric machine 1. The permanent magnets 5 are arranged on the outer periphery of the rotor 3 so as to form multiple magnetic poles in the circumferential direction, and are divided into multiple segments in the axial direction. This reduces loss in the rotor 3 and improves the efficiency of the rotating electric machine 1. As a result, the rotating electric machine 1 according to the embodiment can increase the output density as a rotating electric machine for an aircraft. Specifically, in the above embodiment, a dual-system circuit configuration is formed by two power converters INV1 and INV2, 48 slots 8 are formed, and 8 magnetic poles are formed by the permanent magnets 5.

[0039] According to the rotating electric machine 1 of the above embodiment, the rotor 3 further includes a sleeve 6 that holds the permanent magnets 5 from the radially outer side. The sleeve 6 is also divided into multiple sections in the axial direction. Here, the number of divisions of the sleeve 6 may be equal to or greater than the number of divisions of the permanent magnets 5. As described above, the sleeve 6 is closer to the outer periphery of the rotor 3 than the permanent magnets 5, and the influence of changes in magnetic flux from the stator 2 as the rotor 3 rotates is more pronounced on the sleeve 6 than on the permanent magnets 5. Therefore, if the number of divisions of the permanent magnets 5 and the number of divisions of the sleeve 6 are different, the efficiency of the rotating electric machine 1 can be more effectively improved by making the number of divisions of the sleeve 6 greater than the number of divisions of the permanent magnets 5. Note that the number of divisions of the permanent magnets 5 and the number of divisions of the sleeve 6 may be the same.

[0040] According to the rotating electric machine 1 of the above embodiment, the ratio G / R is set to 0.020 or more and 0.031 or less, where G is the air gap between the rotor 3 and the stator 2 and R is the radius of the rotor 3. Vibrations are easily transmitted to the rotor 3, which is directly connected to the rotating shaft of an aircraft engine. Therefore, by setting the ratio G / R to 0.020 or more, the air gap G is slightly wider relative to the radius R, and contact between the stator 2 and the rotor 3 can be avoided. On the other hand, if the ratio G / R exceeds 0.031, the air gap G relative to the radius R becomes too wide, and the efficiency of the rotating electric machine 1 decreases.

[0041] According to the rotating electric machine 1 of the above embodiment, eight coils 11 for each phase are electrically connected in parallel for each of the two power converters INV1 and INV2. This configuration makes it possible to keep the induced voltage low, thereby increasing the number of turns in the coils 11. Increasing the number of turns in the coils 11 allows the rectangular wire 10 that constitutes the coils 11 to be thinner. As a result, loss in the coils 11 can be reduced.

[0042] In the rotating electric machine 1 according to the above embodiment, the ratio of the short side to the long side in the cross section of the rectangular wire 10 of the coil 11 is 0.125 or more and 0.310 or less. This makes it possible to more reliably reduce eddy current loss in the coil 11. If this ratio is less than 0.125, the rectangular wire 10 becomes too thin, making it difficult to manufacture the stator 2. On the other hand, if this ratio exceeds 0.310, high current density areas will occur, resulting in increased eddy current loss.

[0043] Although several embodiments have been described, modifications or variations of the embodiments can be made based on the above disclosure. All components of the above embodiments and all features described in the claims may be individually extracted and combined, as long as they are not mutually contradictory. In the above embodiments, the rotating electric machine 1 is a generator that generates electricity using the output of an aircraft engine. However, the rotating electric machine 1 may also be used as an electric motor. The rotating electric machine 1 as an electric motor may be used as a starter motor for an aircraft engine. Furthermore, in the future, if energy storage devices such as fuel cells are installed in aircraft, it may be possible to configure a hybrid thrust system in which the rotating electric machine 1 is driven as a generator.

[0044] When the rotating electric machine 1 is used as a generator, the power converters INV1 and INV2 function as converters that control the power generated by the generator. When the rotating electric machine 1 is used as an electric motor, the power converters INV1 and INV2 function as inverters that control the rotation speed of the electric motor.

[0045] The entire contents of Japanese Patent Application No. 2024-149874 (filed August 30, 2024) are hereby incorporated by reference into this specification.

[0046] REFERENCE SIGNS LIST 1 Rotating electric machine 2 Stator 3 Rotor 3S Rotor shaft 4 Rotor core 5 Permanent magnet 6 Sleeve 7 Stator core 8 Slot 9 Teeth 10 Rectangular wire 11 Coil INV1, INV2 Power converter

Claims

1. An SPM type multiple three-phase synchronous rotating electric machine for aircraft, comprising: a rotor shaft directly connected to the rotating shaft of an aircraft engine, a rotor having a plurality of permanent magnets; a stator having a plurality of slots in which coils are housed; and a plurality of power converters for controlling the energy of the rotating electric machine, wherein the plurality of permanent magnets are arranged on the outer periphery of the rotor so as to form a plurality of magnetic poles in the circumferential direction, and each of the plurality of permanent magnets is divided into a plurality of segments in the axial direction, a plurality of slots are formed in the stator in the circumferential direction, and the coils are wound in the plurality of slots using fractional pitch winding and two-layer distributed winding.

2. A rotating electric machine according to claim 1, wherein the rotor further has a sleeve that holds the plurality of permanent magnets from the radially outer side, the sleeve is divided into a plurality of segments in the axial direction, and the number of divisions of the sleeve is equal to or greater than the number of divisions of the permanent magnets.

3. A rotating electric machine according to claim 1 or 2, wherein, when the air gap between the rotor and the stator is G and the radius of the rotor is R, G / R is 0.020 or more and 0.031 or less.

4. A rotating electric machine according to any one of claims 1 to 3, wherein the plurality of power converters are two power converters, the plurality of permanent magnets are arranged on the outer periphery of the rotor so as to form eight magnetic poles in the circumferential direction, the plurality of slots are 48 slots, and for each of the two power converters, the eight coils of each phase are electrically connected in parallel.

5. A rotating electric machine according to any one of claims 1 to 4, wherein the ratio of the short side to the long side in the cross section of the rectangular wire of the coil is 0.125 or more and 0.310 or less.

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