Rotary electric machine

Abstract

To provide a rotary electric machine having an improved winding switching function.SOLUTION: A stator having a stator core and a stator coil, and a rotor facing the stator via an air gap, wherein the stator core has a plurality of slots for accommodating the stator coil, and the stator coil has a first coil group for each phase and a second coil group connected in series with the first coil group, the second coil group is switchable between a first mode and a second mode, the first mode being a state in which the number of parallel connections of the second coil group is smaller than that of the first coil group, the second mode being another state, and each of the plurality of slots accommodates the first coil group and the second coil group.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a rotating electric machine having a winding switching function. [Background technology]

[0002] Conventionally, there is known a rotating electric machine having a winding switching function that can switch between a series connection and a parallel connection of a plurality of coil sections that make up the coils of each phase of a multi-phase motor (see, for example, Patent Document 1).With the winding switching function, by switching the connection of the plurality of coil sections, it is possible to change the rotation speed-torque curve (NT curve) for the same current and voltage input, thereby expanding the operating range of the rotating electric machine. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2022 / 234826 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the past, when the winding switching function was used to switch the connections of multiple coil sections, as will be described in detail later, there was a concern that the current flowing through each of the multiple coil sections would become uneven, causing copper loss to concentrate in some slots, raising the maximum coil temperature and exceeding the allowable temperature of the wire coating. Also, when there is an unevenness in the current flowing through each of the multiple coil sections, there is an uneven distribution of the armature magnetomotive force (hereinafter referred to as "ampere turns"), making the iron core more susceptible to magnetic saturation and causing a decrease in torque.

[0005] An object of the present invention is to provide a rotating electric machine with an improved winding switching function. [Means for solving the problem]

[0006] A rotating electric machine according to one aspect of the present invention comprises a stator having a stator core and a stator coil, and a rotor facing the stator via an air gap, wherein the stator core has a plurality of slots that accommodate the stator coil, the stator coil has a first coil group for each phase and a second coil group connected in series with the first coil group, the second coil group being switchable between a first mode in which the number of parallel connections is smaller than that of the first coil group, and a second mode in which the second coil group is in another state, and wherein each of the plurality of slots accommodates the first coil group and the second coil group. [Effects of the Invention]

[0007] According to one aspect of the present invention, it is possible to provide a rotating electric machine with an improved winding switching function. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram showing a schematic configuration of a motor according to a first embodiment of the present invention. [Figure 2] FIG. 10 is a diagram showing a schematic configuration of a stator 210 of a motor according to a conventional example. [Figure 3] 10 is a graph showing calculation results of torque-current characteristics for each ampere-turn ratio. [Figure 4] FIG. 10 is a diagram illustrating a winding arrangement according to a second embodiment of the present invention. [Figure 5] FIG. 10 is a diagram illustrating a winding arrangement according to a comparative example. [Figure 6] 10A and 10B are diagrams illustrating the shape of a coil according to a third embodiment of the present invention. [Figure 7] FIG. 10 is a table showing the current density of each coil section in the 6-series mode and the 4-series mode. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, a rotating electric machine according to an embodiment of the present invention will be described with reference to the drawings. In the drawings, the scale and number of components may differ from the actual structure in order to make each component easier to understand.

[0010] <Embodiment 1> Fig. 1 is a diagram showing a schematic configuration of a motor 100 according to a first embodiment of the present invention. Fig. 1(A) is a schematic diagram of the motor 100 as viewed in a direction parallel to a central axis J, which is the center of the rotation shaft of the motor 100. Fig. 1(B) is a schematic circuit diagram showing a connection configuration of a U-phase coil among stator coils 140 wound around a stator core 111.

[0011] Hereinafter, the direction parallel to the central axis J will be referred to as the axial direction. In the axial direction, the side extending toward the front from the plane of FIG. 1 will be referred to as the "one side," and the side extending away from the plane of FIG. 1 will be referred to as the "other side." Note that the terms "one side" and "other side" are names used merely for the purpose of explanation and do not limit the actual positional relationship or direction. Furthermore, unless otherwise specified, the radial direction centered on the central axis J will be simply referred to as the "radial direction," and the circumferential direction centered on the central axis J, i.e., around the axis of the central axis J, will be simply referred to as the "circumferential direction." In the radial direction, the side closer to the central axis J will be referred to as the "radially inner side," and the side away from the central axis J will be referred to as the "radially outer side." In the circumferential direction, the clockwise side when viewed from one axial side will be referred to as the "one circumferential side," and the counterclockwise side will be referred to as the "other circumferential side."

[0012] In this specification, "extending in the axial direction" includes not only extending strictly in the axial direction but also extending in a direction tilted by less than 45° with respect to the axial direction. Furthermore, in this specification, "extending in the radial direction" includes not only extending strictly in the radial direction, i.e., in a direction perpendicular to the axial direction, but also extending in a direction tilted by less than 45° with respect to the radial direction. Furthermore, "parallel" includes not only being strictly parallel but also being tilted by an angle of less than 45° with respect to the direction perpendicular to the axial direction. Furthermore, "extending in a direction perpendicular to the axial direction" includes not only extending in a direction perpendicular to the axial direction but also extending in a direction tilted by less than 45° with respect to the direction perpendicular to the axial direction.

[0013] The motor 100 is an example of a rotating electric machine. The motor 100 has a stator 110, a rotor 150 disposed radially inside the stator 110 across an air gap, and a shaft 160 fixed to the rotor 150 and extending along a central axis J. The shaft 160 is the rotating shaft of the motor 100. The motor 100 is an example of an 8-pole, 12-slot motor.

[0014] The stator 110 has a stator core 111 and a stator coil 140. The stator core 111 has a core back portion 112 and teeth portions 120 that extend radially inward of the core back portion 112 and are arranged at equal intervals in the circumferential direction. The teeth portions 120 include teeth portions 120a, 120b, 120c, 120d, 120e, 120f, 120g, 120h, 120i, 120j, 120k, and 120l.

[0015] The stator core 111 has slots 130 between the teeth 120. The slots 130 include slots 130a, 130b, 130c, 130d, 130e, 130f, 130g, 130h, 130i, 130j, 130k, and 130l. The stator core 111 has slot 130a between tooth 120a and tooth 120b. In the figure, lines are drawn dividing each slot 130 into four regions to make the arrangement of the stator coil 140 easier to understand. However, the stator core 111 does not necessarily have members dividing each slot. The four regions in each slot are a region on the radially outer side and one circumferential side, a region on the radially outer side and the other circumferential side, a region on the radially inner side and one circumferential side, and a region on the radially inner side and the other circumferential side.

[0016] The stator core 111 has a slot 130b between the teeth 120b and 120c. The stator core 111 has a slot 130c between the teeth 120c and 120d. The stator core 111 has a slot 130d between the teeth 120d and 120e. The stator core 111 has a slot 130e between the teeth 120e and 120f. The stator core 111 has a slot 130f between the teeth 120f and 120g. The stator core 111 has a slot 130g between the teeth 120g and 120h. The stator core 111 has a slot 130h between the teeth 120h and 120i. The stator core 111 has a slot 130i between the tooth portion 120i and the tooth portion 120j. The stator core 111 has a slot 130j between the tooth portion 120j and the tooth portion 120k. The stator core 111 has a slot 130k between the tooth portion 120k and the tooth portion 120l. The stator core 111 has a slot 130l between the tooth portion 120l and the tooth portion 120a.

[0017] The stator coil 140 is wound around the tooth portion 120. The stator coil 140 has a coil portion provided for each of the UVW phases. The coil portion of the stator coil 140 for the U phase is called the coil portion U, the coil portion of the stator coil 140 for the V phase is called the coil portion V, and the coil portion of the stator coil 140 for the W phase is called the coil portion W.

[0018] In the following, only the U-phase coil section will be described. The V-phase coil sections V1A, V1B, V2A, V2B, V3A, V3B, V4A, and V4B, and the W-phase coil sections W1A, W1B, W2A, W2B, W3A, W3B, W4A, and W4B are arranged as shown in Figure 1(A), and are connected in the same manner as the U-phase coil sections for each phase.

[0019] The stator coil 140 has a coil portion U1A, which is the first coil portion of the first set of U-phase coils, and a coil portion U2A, which is the first coil portion of the second set of U-phase coils. The coil portion U1A and the coil portion U2A are wound around the tooth portion 120a. The coil portion U1A is accommodated in an area radially outside and on one circumferential side of the slot 130l and an area radially outside and on the other circumferential side of the slot 130a. The coil portion U2A is accommodated in an area radially inside and on one circumferential side of the slot 130l and an area radially inside and on the other circumferential side of the slot 130a.

[0020] The stator coil 140 has a coil portion U3B, which is the second coil portion of the third set of U-phase coils, and a coil portion U4B, which is the second coil portion of the fourth set of U-phase coils. The coil portions U3B and U4B are wound around the tooth portion 120d. The coil portion U3B is accommodated in a region radially outward and on one circumferential side of the slot 130c and a region radially outward and on the other circumferential side of the slot 130d. The coil portion U4B is accommodated in a region radially inward and on one circumferential side of the slot 130c and a region radially inward and on the other circumferential side of the slot 130d.

[0021] The stator coil 140 has a coil portion U3A, which is the first coil portion of the third set of U-phase coils, and a coil portion U4A, which is the first coil portion of the fourth set of U-phase coils. The coil portion U3A and the coil portion U4A are wound around the tooth portion 120g. The coil portion U3A is accommodated in a region radially outward and on one circumferential side of the slot 130f and a region radially outward and on the other circumferential side of the slot 130g. The coil portion U4A is accommodated in a region radially inward and on one circumferential side of the slot 130f and a region radially inward and on the other circumferential side of the slot 130g.

[0022] The stator coil 140 has a coil portion U1B, which is the second coil portion of the first set of U-phase coils, and a coil portion U2B, which is the second coil portion of the second set of U-phase coils. The coil portion U1B and the coil portion U2B are wound around the tooth portion 120j. The coil portion U1B is accommodated in a region radially outside and on one circumferential side of the slot 130i and a region radially outside and on the other circumferential side of the slot 130j. The coil portion U2B is accommodated in a region radially inside and on one circumferential side of the slot 130i and a region radially inside and on the other circumferential side of the slot 130j.

[0023] In the following, coil portion U1A and coil portion U1B may be simply referred to as coil portion U1, coil portion U2A and coil portion U2B may be simply referred to as coil portion U2, coil portion U3A and coil portion U3B may be simply referred to as coil portion U3, and coil portion U4A and coil portion U4B may be simply referred to as coil portion U4.

[0024] The U-phase coil sections U1A, U1B, U2A, U2B, U3A, U3B, U4A, and U4B are connected as shown in FIG. 1(B).

[0025] Coil section U1A and coil section U1B are connected in series. Coil section U1A is located upstream of coil section U1B. Coil section U2A and coil section U2B are connected in series. Coil section U2A is located upstream of coil section U2B. Coil section U3A and coil section U3B are connected in series. Coil section U3A is located upstream of coil section U3B. Coil section U4A and coil section U4B are connected in series. Coil section U4A is located upstream of coil section U4B.

[0026] The coil portions U1A and U1B are connected in parallel to the coil portions U3A and U3B. The upstream of the coil portion U1A is connected to the upstream of the coil portion U3A, and the downstream of the coil portion U1B is connected to the downstream of the coil portion U3B.

[0027] The coil portions U1A and U1B are connected in series with the coil portions U2A and U2B. The downstream of the coil portion U1B is connected upstream of the coil portion U2A. The coil portions U3A and U3B are connected in series with the coil portions U2A and U2B. The downstream of the coil portion U3B is connected upstream of the coil portion U2A.

[0028] The motor 100 has switches 141, 142, and 143 that switch the connection of the stator coil 140. The upstream of the coil section U2A is connected to the upstream of the coil section U4A via switch 141. The downstream of the coil section U2B is connected to the downstream of the coil section U4B via switch 142. The downstream of the coil section U2B is connected to the upstream of the coil section U4A via switch 143. When the motor 100 turns on switch 141, turns on switch 142, and turns off switch 143, the coil sections U2A and U2B and the coil sections U4A and U4B are connected in parallel. When the motor 100 turns off switch 141, turns off switch 142, and turns on switch 143, the coil sections U2A and U2B and the coil sections U4A and U4B are connected in series.

[0029] In the following, the state in which coil sections U2A and U2B and coil sections U4A and U4B are connected in series by winding switching is referred to as the 6-series mode, since there are six coil sections connected in series. Also, the state in which coil sections U2A and U2B and coil sections U4A and U4B are connected in parallel by winding switching is referred to as the 4-series mode, since there are four coil sections connected in series.

[0030] Coil sections U1 and U3 are always in a parallel circuit in the 6-series mode and the 4-series mode, while coil sections U2 and U4 are in a series circuit in the 6-series mode and in a parallel circuit in the 4-series mode. In this case, when comparing the number of parallel connections between coil sections U1 and U3 and coil sections U2 and U4, in the 6-series mode, coil sections U1 and U3 are the coil group with the larger number of parallel connections, while coil sections U2 and U4 are the coil group with the smaller number of parallel connections. The coil group with the larger number of parallel connections is sometimes called the first coil group, and the coil group with the smaller number of parallel connections is sometimes called the second coil group.

[0031] FIG. 1(B) shows the current flowing from upstream of coil section U1A to downstream of coil section U4B in the 6-phase mode. Ia is the 1-phase armature current. If the current flowing in the U phase is Ia, then in the 6-phase mode, the current flowing through coil sections U1A, U1B, U3A, and U3B is Ia / 2, and the current flowing through coil sections U2A, U2B, U4A, and U4B is Ia.

[0032] FIG. 1A also shows the ampere-turns at the positions of the teeth around which the U-phase coils are wound in the 6-series mode. Ia is the single-phase armature current. Nt is the total number of turns of the coils wound around one tooth. The number of turns is assumed to be equal for coils U1A, U1B, U2A, U2B, U3A, U3B, U4A, and U4B. The total U-phase ampere-turns is 3IaNt. At each of the positions of teeth 120a, 120d, 120g, and 120j, the ampere-turns are (3 / 4)IaNt. As described above, this embodiment can eliminate ampere-turn imbalances.

[0033] In addition, in the 4-series mode, the current flowing through each of coil sections U1A, U1B, U3A, U3B, U2A, U2B, U4A, and U4B is Ia / 2, and no current imbalance occurs.

[0034] Fig. 2 is a diagram showing a schematic configuration of a stator 210 of a motor according to a conventional example. Fig. 2(A) is a schematic diagram of the stator 210 as viewed from a direction parallel to the rotation axis. Fig. 2(B) is a schematic circuit diagram showing a connection configuration of a U-phase coil of a stator coil 240 wound around a stator core 211.

[0035] The stator 210 has a stator core 211 and a stator coil 240. The stator core 211 has a core back portion 212 and teeth portions 220 that extend radially inward of the core back portion 212 and are arranged at equal intervals in the circumferential direction. The teeth portions 220 include teeth portions 220a, 220b, 220c, 220d, 220e, 220f, 220g, 220h, 220i, 220j, 220k, and 220l.

[0036] The stator core 211 has slots 230 between the teeth 220. The slots 230 include slots 230a, 230b, 230c, 230d, 230e, 230f, 230g, 230h, 230i, 230j, 230k, and 230l. The stator core 211 has slot 230a between teeth 220a and 220b. The stator core 211 has slot 230b between teeth 220b and 220c. The stator core 211 has slot 230c between teeth 220c and 220d. The stator core 211 has slot 230d between teeth 220d and 220e. The stator core 211 has a slot 230e between the tooth portion 220e and the tooth portion 220f. The stator core 211 has a slot 230f between the tooth portion 220f and the tooth portion 220g. The stator core 211 has a slot 230g between the tooth portion 220g and the tooth portion 220h. The stator core 211 has a slot 230h between the tooth portion 220h and the tooth portion 220i. The stator core 211 has a slot 230i between the tooth portion 220i and the tooth portion 220j. The stator core 211 has a slot 230j between the tooth portion 220j and the tooth portion 220k. The stator core 211 has a slot 230k between the tooth portion 220k and the tooth portion 220l. Stator core 211 has slots 230l between teeth 220l and teeth 220a.

[0037] The stator coil 240 is wound around the tooth portion 220. The stator coil 240 has coil portions provided for each of the UVW phases. The stator coil 240 has coil portion U1, which is a first set of coil portions for the U phase. The coil portion U1 is wound around the tooth portion 220a. The stator coil 240 has coil portion U2, which is a second set of coil portions for the U phase. The coil portion U2 is wound around the tooth portion 220j. The stator coil 240 has coil portion U3, which is a third set of coil portions for the U phase. The coil portion U3 is wound around the tooth portion 220g. The stator coil 240 has coil portion U4, which is a fourth set of coil portions for the U phase. The coil portion U4 is wound around the tooth portion 220d.

[0038] The U-phase coil sections U1, U2, U3, and U4 are connected as shown in Figure 2(B). Coil section U1 and coil section U3 are connected in parallel. Coil section U1 and coil section U2 are connected in series.

[0039] In this conventional example, switches 241, 242, and 243 are provided to switch the connection of the stator coil 240. The upstream of the coil section U2 is connected to the upstream of the coil section U4 via switch 241. The downstream of the coil section U2 is connected to the downstream of the coil section U4 via switch 242. The downstream of the coil section U2 is connected to the upstream of the coil section U4 via switch 243. When switch 241 is turned on, switch 242 is turned on, and switch 243 is turned off, the coil sections U2 and U4 are connected in parallel. When switch 241 is turned off, switch 242 is turned off, and switch 243 is turned on, the coil sections U2 and U4 are connected in series.

[0040] The number of turns in the coil section U1 is equal to the sum of the number of turns in the coil section U1A and the number of turns in the coil section U1B in embodiment 1. The number of turns in the coil section U2 is equal to the sum of the number of turns in the coil section U2A and the number of turns in the coil section U2B in embodiment 1. The number of turns in the coil section U3 is equal to the sum of the number of turns in the coil section U3A and the number of turns in the coil section U3B in embodiment 1. The number of turns in the coil section U34 is equal to the sum of the number of turns in the coil section U4A and the number of turns in the coil section U4B in embodiment 1.

[0041] In this conventional example, the state in which the coil section U2 and the coil section U4 are connected in series is called the 6-series mode in consideration of the number of turns of the coil sections, and corresponds to the first embodiment in Fig. 1. Also, the state in which the coil section U2 and the coil section U4 are connected in parallel is called the 4-series mode in consideration of the number of turns of the coil sections, and corresponds to the first embodiment in Fig. 1.

[0042] Figure 2(B) shows the current flowing from upstream of coil unit U1 to downstream of coil unit U4 in the 6-phase mode. Ia is the 1-phase armature current. If the current flowing in the U phase is Ia, then in the 6-phase mode, the current flowing in each of coil units U1 and U3 is Ia / 2, and the current flowing in each of coil units U2 and U4 is Ia.

[0043] FIG. 2A also shows the ampere-turns at the tooth positions around which the U-phase coils are wound in 6-series mode. Ia is the single-phase armature current. Nt is the total number of turns of the coils wound around one tooth. The number of turns in each of coils U1, U2, U3, and U4 is assumed to be equal. The total U-phase ampere-turns is 3IaNt. At each of teeth 220a and 220g, the ampere-turns are (1 / 2)IaNt. At each of teeth 220d and 220j, the ampere-turns are IaNt. As described above, the conventional example suffers from an imbalance in ampere-turns. Furthermore, in the conventional example, the current imbalance causes copper loss to concentrate in certain slots, raising the maximum coil temperature and potentially exceeding the allowable temperature of the wire coating.

[0044] If the ampere-turn ratio is (ampere-turns of coil sections U1, U3) / (ampere-turns of coil sections U2, U4), the ampere-turn ratio of the conventional example described above is approximately 0.5, while the ampere-turn ratio of embodiment 1 is approximately 1. FIG. 3 is a graph showing calculation results of torque-current characteristics for each ampere-turn ratio when the total ampere-turns of coil sections U1 to U4 is constant and the configurations of the V phase and W phase are the same as that of the U phase. As shown in FIG. 3, it can be seen that the torque decreases as the ampere-turn ratio becomes smaller than 1. According to embodiment 1, the ampere-turn ratio can be made approximately 1, and good torque-current characteristics can be obtained.

[0045] In the first embodiment, in a configuration in which winding switching is possible, one slot accommodates a coil group with a smaller number of parallel connections (coil sections U2 and U4) and a coil group with a larger number of parallel connections (coil sections U1 and U3).

[0046] <Embodiment 2> The second embodiment is an example of determining the positions at which the coil sections U1, U2, U3, and U4 are accommodated in each slot. FIG. 4 is a diagram illustrating a winding arrangement according to the second embodiment of the present invention. FIG. 4(A) is an enlarged view showing the vicinity of the tooth section 120 of the stator 110 according to the second embodiment of the present invention. In the second embodiment, the coil sections U1 and U3 are accommodated on the radially outer side of the slot 130, and the coil sections U2 and U4 are accommodated on the radially inner side. As shown in FIG. 1(B), in the 6-series mode, the current flowing through each of the coil sections U1 and U3 is Ia / 2, and the current flowing through each of the coil sections U2 and U4 is Ia. By arranging the coil sections U1, U2, U3, and U4 as shown in FIG. 4(A), the magnetic flux generated by the coil sections U1 and U3 is reduced.

[0047] Fig. 4(B) is a diagram showing copper loss in the stator 110 according to the second embodiment of the present invention. In the configuration of the second embodiment, as shown in Fig. 4(B), in the second embodiment, the DC copper loss and AC copper loss in the coil portions U1 and U3 are approximately 0.1, and the DC copper loss and AC copper loss in the coil portions U2 and U3 are approximately 0.7. Therefore, the sum of the DC copper loss and AC copper loss in the coil portions U1 and U3 and the DC copper loss and AC copper loss in the coil portions U2 and U3 is approximately 0.8.

[0048] 5A and 5B are diagrams illustrating a winding arrangement according to a comparative example. FIG. 5A is an enlarged view showing the vicinity of the tooth portion 120 of the stator 110 according to the comparative example. In the second embodiment, the coil portion U1 or U3 is accommodated on the radially outer side of the slot 130, and the coil portion U2 or U4 is accommodated on the radially inner side. As shown in FIG. 1B, in the 6-series mode, the current flowing through each of the coil portions U1 and U3 is Ia / 2, and the current flowing through each of the coil portions U2 and U4 is Ia. By arranging the coil portions U1, U2, U3, and U4 as shown in FIG. 5A, the magnetic flux generated by the coil portions U2 and U4 is large.

[0049] Fig. 5(B) is a diagram showing copper loss in a stator 110 according to a comparative example. In the configuration of embodiment 2, as shown in Fig. 5(B), in the comparative example, the DC copper loss and AC copper loss in the coil portions U1 and U3 are approximately 0.7, and the DC copper loss and AC copper loss in the coil portions U2 and U3 are approximately 0.3. Therefore, the sum of the DC copper loss and AC copper loss in the coil portions U1 and U3 and the DC copper loss and AC copper loss in the coil portions U2 and U3 is approximately 1.0.

[0050] As described above, the total of the DC copper loss and the AC copper loss is improved compared to the comparative example according to the second embodiment. This is thought to be because the amount of AC magnetic flux passing through the coil closer to the air gap increases when the current flowing through the coil farther from the air gap is larger.

[0051] <Embodiment 3> In the third embodiment, the number of turns of the coil sections U1, U2, U3, and U4 is different. In the third embodiment, in a switching state (e.g., 6-series mode) in which circuits with different numbers of parallel connections are used, the number of turns of the coil group with fewer parallel connections (coil sections U2 and U4) is smaller than the number of turns of the coil group with more parallel connections (coil sections U1 and U3). However, to avoid bias in the ampere-turn distribution depending on the connection state, such as in the 6-series mode and the 4-series mode, it is preferable to determine the allocation of the number of turns by considering the overall balance of the improvement for each mode. In the third embodiment, the number of turns of the coil sections U1, U2, U3, and U4 may be different after being arranged in the slot 130 shown in FIG. 1A, or the number of turns of the coil sections U1, U2, U3, and U4 may be different after being arranged in the slot 230 shown in FIG. 2A. 2(A) are arranged in the slots 130 and the number of turns is made different, the winding connection can be simplified compared to embodiment 1. The slot area of ​​the stator cores 111 and 211 may be changed depending on the number of turns.

[0052] <Embodiment 4> The fourth embodiment is an example in which the coil shapes of the coil sections U1, U2, U3, and U4 are different. Fig. 6 is a diagram illustrating the coil shape according to the fourth embodiment of the present invention. In the fourth embodiment, the conductor cross-sectional area per turn of the coil group with fewer parallel connections (coil sections U2 and U4) is made larger than that of the coil group with more parallel connections (coil sections U1 and U3). According to the fourth embodiment, the loss distribution can be further alleviated and the maximum temperature of the coil can be reduced.

[0053] Fig. 7 is a table showing the current density of each coil section in the 6-phase and 4-phase modes. Fig. 7(A) shows an example in which the conductor cross-sectional area per turn is not different between the coil sections U1 and U3 and the coil sections U2 and U4. Fig. 7(B) shows an example in which the conductor cross-sectional area per turn is different between the coil sections U1 and U3 and the coil sections U2 and U4. According to the fourth embodiment, by changing the conductor cross-sectional area, the maximum current density is reduced, making it possible to suppress the maximum coil temperature.

[0054] <Embodiment 5> In embodiment 5, the coil group with fewer parallel connections (coil sections U2 and U4) uses a material with a higher specific gravity and lower resistivity than the coil group with more parallel connections (coil sections U1 and U3). For example, the coil group with fewer parallel connections is made of copper, and the coil group with more parallel connections is made of aluminum. According to embodiment 5, aluminum is used only for the coil group with a large number of parallel connections and a low winding resistance, thereby reducing loss and reducing weight.

[0055] <Embodiment 6> In the sixth embodiment, in the distributed winding of each of the above-described embodiments, the coil portions housed on the radially inner side of each slot 130 are shifted in the circumferential direction relative to the coil portions housed on the radially outer side. For example, the coil portions housed on the radially inner side are shifted by one to several slots to one side in the circumferential direction. According to the sixth embodiment, in addition to improving the winding switching characteristics, the effect of suppressing torque ripple and vibration can also be obtained.

[0056] The present invention is not limited to the above-described embodiments, and various improvements and design changes may be made without departing from the spirit of the present invention. In addition, the embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0057] 100...Motor 110...Stator 111... Stator core 120...Teeth part 130...Slot 140...Stator coil

Claims

1. a stator having a stator core and a stator coil, and a rotor facing the stator via an air gap; the stator core has a plurality of slots that accommodate the stator coils; The stator coil has a first coil group for each phase and a second coil group connected in series with the first coil group, the second coil group is switchable between a first mode in which the number of parallel connections is smaller than that of the first coil group, and a second mode in which the second coil group is in another state; Each of the plurality of slots accommodates the first coil group and the second coil group. A rotating electric machine characterized by:

2. Each of the plurality of slots accommodates the second coil group on a side closer to an air gap between the rotor and the slot, and accommodates the first coil group on a side farther from the air gap.

2. The rotating electrical machine according to claim 1.

3. The number of turns of the first coil group is different from the number of turns of the second coil group.

2. The rotating electrical machine according to claim 1.

4. a conductor cross-sectional area of ​​the first coil group is different from a conductor cross-sectional area of ​​the second coil group; 2. The rotating electrical machine according to claim 1.

5. the material of the first coil group is different from the material of the second coil group; 2. The rotating electrical machine according to claim 1.

6. each of the plurality of slots accommodates the first coil group of one of the phases and the second coil group of a phase different from the one phase; 2. The rotating electrical machine according to claim 1.

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