Rotary electric machine and rotary electric machine system

Abstract

According to the embodiment, a rotary electric machine (100) comprises: a stator core (121) and a three-phase armature winding (125); a rotor core (112); a magnetic force-variable magnet (113); a field winding (114) through which a zero-phase current flows; a first slip ring that is provided so as to be capable of electrically connecting one end portion of the field winding to the outside; and a second slip ring that is provided so as to be capable of electrically connecting the other end portion of the field winding to the outside.

Description

Rotating electric machines, rotating electric machine systems

[0001] The present invention relates to a rotating electric machine and a rotating electric machine system.

[0002] In recent years, interior permanent magnet synchronous motors (IMMs) have become increasingly popular in electric drive systems for vehicles due to their compact size and high efficiency. To further improve efficiency, variable magnetic flux motors (memory motors) have been developed, which instantaneously apply a magnetic field to a magnet to actively change its magnetic state. To achieve high motor efficiency, high magnetic force is desirable at low speeds and low magnetic force at high speeds. Variable magnetic flux motors solve this trade-off problem. While low-coercivity magnets (hereafter referred to as variable-force magnets) are typically designed to have a certain level of demagnetization resistance to prevent unintended demagnetization during load operation, this translates into a larger magnetomotive force required to actively control the magnetic state. Therefore, a large instantaneous magnetizing current is required to change the magnetic state of a variable-force magnet.

[0003] Regarding the demagnetization of variable magnetic force magnets, a method is known in which a magnetizing current is passed using an armature current.

[0004] Alternatively, a method is known in which a field winding is provided in the rotor and a magnetizing current flows independently of the armature current.

[0005] Patent No. 5624284 Patent No. 6833907

[0006] The above-mentioned method of using the armature current to pass the magnetizing current has the following problems.

[0007] (1) It is difficult to perform demagnetization during load operation. In other words, the rotor drive and the demagnetization of the variable magnetic force magnet must be performed by controlling the same armature current. In particular, the above-mentioned prior art requires the passage of a magnetizing current that is much larger than the current used in normal load operation. Therefore, in order to obtain the desired magnetizing current, the rotating electric machine must be operated in a state other than load operation.

[0008] (2) It is difficult to achieve both a wide variable flux range within the inverter's allowable current and prevention of demagnetization during load operation. Furthermore, if the number of turns of the armature winding is increased instead of reducing the conductor cross-sectional area, it is possible to increase the magnetomotive force for demagnetization while maintaining the inverter current. However, this significantly increases the electrical resistance of the armature winding, and even if the variable flux performance improves, the loss caused by the winding increases, preventing the benefit of high efficiency. In other words, the first point is that in order to achieve a wide variable flux range, the demagnetization resistance of the variable coercivity magnet must be low. Meanwhile, the second point is that during load operation, the variable coercivity magnet must be able to withstand the opposing magnetic field acting on it. These two points are mutually exclusive, making it difficult to achieve both.

[0009] Furthermore, the above-mentioned method of providing a field winding in the rotor and passing a magnetizing current independently of the armature current has the following problems.

[0010] (1) A circuit for supplying power to the field winding of the rotor is required in addition to the circuit for supplying power to the armature winding.

[0011] (2) If a circuit for energizing the field winding is provided, the electric system becomes larger.

[0012] In addition to these examples, there is also a known technique for achieving variable magnetic flux characteristics by changing the permeability of the rotor magnetic path using zero-phase current flowing through the armature. However, this method has the problem that the zero-phase current must be constantly applied while achieving the variable magnetic flux characteristics. Because the zero-phase current flows through the armature winding and the field winding, copper loss due to the zero-phase current is constantly generated in both windings. This is not desirable for applications aiming for low loss and high efficiency in motors.

[0013] In such a situation, it is desirable to obtain the desired performance without increasing the size of the drive system.

[0014] The problem to be solved by the present invention is to provide a rotating electric machine and a rotating electric machine system that can achieve high efficiency.

[0015] To achieve the above-mentioned object, a rotating electric machine according to an embodiment of the present invention includes a stator core, a star-connected three-phase armature winding wound around the stator core, a rotor shaft extending in the direction of a rotation axis, a rotor core attached radially outside the rotor shaft, variable coercive force magnets housed in the rotor core, a field winding disposed near the variable coercive force magnets and configured to change the magnetization state of the variable coercive force magnets when a zero-phase current flows through the field winding, a first slip ring for electrically connecting a first end of the field winding to an outside of the rotor, and a second slip ring for electrically connecting a second end of the field winding to an outside of the rotor. The first end is electrically connected to a neutral point of the three-phase armature winding via the first slip ring.

[0016] 1 is a partial horizontal cross-sectional view showing the configuration of a rotating electric machine according to a first embodiment; FIG. 2 is a partial horizontal cross-sectional view showing a modified example of the configuration of the rotating electric machine according to the first embodiment; FIG. 3 is a circuit diagram showing the configuration of a rotating electric machine system according to the first embodiment; FIG. 4 is a flow chart showing the procedure of a control method for the rotating electric machine system according to the first embodiment; FIG. 5 is a circuit diagram showing an example configuration of a comparative example of a rotating electric machine system for explaining the effect of the rotating electric machine system according to the first embodiment; FIG. 6 is a circuit diagram showing the configuration of a rotating electric machine system according to a second embodiment; FIG. 7 is a conceptual partial horizontal cross-sectional view showing an example arrangement of armature winding conductors in slots of a rotating electric machine according to a second embodiment; FIG. 8 is a conceptual partial horizontal cross-sectional view showing an example lamination state of armature winding conductors in slots of a rotating electric machine according to a second embodiment;

[0017] Hereinafter, a rotating electric machine, a rotating electric machine system, and a control method for a rotating electric machine system according to embodiments of the present invention will be described with reference to the drawings. Hereinafter, identical or similar parts will be denoted by common reference numerals, and duplicated explanations will be omitted.

[0018] [First embodiment]

[0019] <Description of Configuration> FIG. 1 is a partial horizontal cross-sectional view showing the configuration of a rotating electrical machine 100 according to a first embodiment.

[0020] The rotating electric machine 100 includes a rotor 110 and a stator 120 .

[0021] The rotor 110 has a rotor shaft 111 extending in the direction of the rotation axis, a rotor core 112 , a variable magnetic force magnet 113 , a field winding 114 , and a plurality of inner fixed magnetic force magnets 115 .

[0022] The rotor shaft 111 is rotatably supported on both axial sides by bearings (not shown).

[0023] The rotor core 112 is attached radially outward of the rotor shaft 111. In each magnetic pole 100p of the rotor core 112, an inner magnet storage outer flux barrier 112a, an inner magnet storage portion 112b, an inner magnet storage inner flux barrier 112c, and an inner bridge 112d are formed radially inward from one side of the rotor core surface 112s. Furthermore, from the inner bridge 112d to the other side of the rotor core surface 112s, the inner magnet storage inner flux barrier 112c, the inner magnet storage portion 112b, and the rotor core surface 112s are formed. These are arranged continuously and in a generally convex shape toward the central axis of rotation CL. This region is referred to as the first flux barrier band. Although the lead wire of the inner magnet storage portion 112b points to the inner fixed magnetic force magnet 115, this refers to the space where the inner fixed magnetic force magnet 115 is not present.

[0024] Additionally, on the radially inner side, from one side of the rotor core surface 112s, an outer magnet storage outer flux barrier 112e, an outer magnet storage portion 112f, an outer magnet storage inner flux barrier 112g, an outer bridge 112h, and an outer central flux barrier 112j are formed. Furthermore, from the outer central flux barrier 112j to the other side of the rotor core surface 112s, the outer bridge 112h, the outer magnet storage inner flux barrier 112g, the outer magnet storage portion 112f, and the outer magnet storage outer flux barrier 112e are formed. These are arranged continuously and in a generally convex shape toward the central axis of rotation CL. This region is referred to as the second flux barrier band. Although the lead wire of the outer magnet storage portion 112f points to the outer fixed magnetic force magnet 116, this refers to the space where the outer fixed magnetic force magnet 116 is not present.

[0025] The variable magnetic force magnet 113 is disposed at the center in the circumferential direction of the first flux barrier band. Field windings 114 for exciting the variable magnetic force magnet 113 are provided adjacent to both sides in the circumferential direction of the variable magnetic force magnet 113, or in the vicinity of the variable magnetic force magnet 113. Here, "in the vicinity" means within a distance range where the current flowing through the field winding 114 can change the magnetized state of the variable magnetic force magnet 113.

[0026] Here, the inner fixed magnetic force magnet 115 is a conventionally used permanent magnet with a sufficiently large coercive force, while the variable magnetic force magnet 113 is a permanent magnet with a smaller coercive force than the inner fixed magnetic force magnet 115, and is magnetized and demagnetized by the external magnetic field generated by the field winding 114.

[0027] In the following embodiment, an example will be described in which the rotor 110 has both the variable magnetic force magnets 113 and the inner fixed magnetic force magnets 115, but it may also have only the variable magnetic force magnets 113 without the inner fixed magnetic force magnets 115. Also, in the figure, of the two-layer flux barrier bands, the variable magnetic force magnets are loaded only in the flux barrier band on the inner diameter side, but it may also be configured so that the variable magnetic force magnets are loaded only in the flux barrier band on the outer diameter side, or in both flux barrier bands.

[0028] Fig. 2 is a partial horizontal cross-sectional view showing a modified configuration of the rotating electric machine 100 according to the first embodiment. In the rotor 110a of the modified configuration shown in Fig. 2, a variable magnetic force magnet 113s and field windings 114s for exciting the variable magnetic force magnet 113s adjacent to both sides of the variable magnetic force magnet 113s in the circumferential direction are provided in place of the outer central flux barrier 112j at the circumferential center of the second flux barrier band. Fig. 2 shows an example configuration in which variable magnetic force magnets are installed in both flux barrier bands.

[0029] In the example shown in FIG. 2, the field winding 114 for exciting the variable magnetic force magnet 113 of the first flux barrier band and the field winding 114s for exciting the variable magnetic force magnet 113s of the second flux barrier band are electrically connected in series.

[0030] The field winding 114 is wound around the variable magnetic force magnet 113 and generates a magnetic field by the field winding current. The magnetic field generated by the field winding current flowing through the field winding 114 is directed radially inward and radially outward depending on the flow of the field winding current in one direction and the opposite direction.

[0031] The field winding 114 may be formed by laminating conductors having a rectangular cross section in the radial direction, or may be formed by forming a coil using conductors having a round cross section.

[0032] The stator 120 has a stator core 121 disposed radially outside the rotor core 112, and a three-phase armature winding 125 (hereinafter referred to as the armature winding 125). A plurality of teeth 122 are formed at circumferential intervals on the inner surface of the stator core 121. An annular yoke 123 is formed on the radially outer portion of the teeth 122 of the stator core 121. Adjacent teeth 122 also form slots 122a. The armature winding 125 is disposed to pass through the slots 122a and is wound around the teeth 122. For ease of explanation of the slots 122a, the armature winding 125 within the slots 122a, which are indicated by lead lines, is not shown in FIGS. 1 and 2.

[0033] 3 is a circuit diagram showing the configuration of the rotating electrical machine system 20 according to the first embodiment. Hereinafter, a power circuit including the rotating electrical machine 100 and the drive device 200 will be described with reference to FIG.

[0034] The rotating electric machine system 20 includes a rotating electric machine 100 and a drive device 200 for the rotating electric machine 100 .

[0035] First, the driving device 200 uses an external DC power supply 1 as a power source to supply AC power to the armature winding 125 of the rotating electric machine 100 and DC power to the field winding 114 of the rotating electric machine 100. Here, the DC power supply 1 is assumed to be a power supply having a first power supply 1a and a second power supply 1b, and having a midpoint 2 that is a connection point between the first power supply 1a and the second power supply 1b. The midpoint 2 provides an intermediate potential of the potential difference generated by the first power supply 1a and the second power supply 1b, i.e., an intermediate potential between both ends of the DC power supply 1. The first power supply 1a and the second power supply 1b have the same voltage value, but may have different voltage values. A midpoint lead 2m is provided from the midpoint 2 for connection.

[0036] The driving device 200 includes a three-phase inverter 210 and a controller 215 .

[0037] The three-phase inverter 210 is a full-bridge inverter circuit configured with a plurality of IGBTs (Insulated Gate Bipolar Transistors) 5. The three-phase inverter 210 receives DC power from a DC power supply 1 as input and supplies three-phase AC power to the external connection terminals 130 of the rotating electric machine 100, i.e., external connection terminals 131a, 131b, and 131c. Note that the components are not limited to IGBTs, and other power semiconductors, such as MOSFETs (Metal-Oxide-Semiconductor Field Effect Transistors), may be used depending on the purpose.

[0038] The controller 215 controls the gate voltage of each of the IGBTs 5 that make up the three-phase inverter 210. In a normal operating state of the rotating electric machine 100, in a situation where the magnetic force of the variable magnetic force magnet 113 is maintained, the voltage of the neutral point 126n becomes zero, and control is performed so that no zero-phase current flows in the field winding 114.

[0039] On the other hand, in states including the normal operating state of the rotating electric machine 100, the magnetic force of the variable magnetized magnet 113 can be changed by shifting the voltage of the AC power supplied to each phase of the armature winding 125 by the same voltage value in the same direction (positive or negative). By superimposing a predetermined voltage of the same sign and absolute value on the time-averaged zero AC power voltage for each phase, the neutral point 126n can be shifted to a predetermined zero-phase sequence voltage. As a result, a potential difference is generated on both sides of the field winding 114, and a predetermined zero-phase sequence current flows through the field winding 114.

[0040] The controller 215 includes an input unit 215a, a storage unit 215b, a calculation unit 215c, and an output unit 215d. Details of the controller 215 will be described later with reference to FIG.

[0041] As described above, the rotating electric machine 100 includes the rotor 110 and the stator 120 .

[0042] First, as described above, the stator 120 has the armature winding 125. The armature winding 125 has armature winding conductors 126, specifically, phase conductors connected in parallel to one another, namely, a U-phase conductor 126u, a V-phase conductor 126v, and a W-phase conductor 126w. One ends of the U-phase conductor 126u, the V-phase conductor 126v, and the W-phase conductor 126w are connected to external connection terminals 131a, 131b, and 131c, respectively. The other ends of the U-phase conductor 126u, the V-phase conductor 126v, and the W-phase conductor 126w are connected to one another at a neutral point 126n. A neutral point lead wire 126m is provided from the neutral point 126n for connection.

[0043] Next, a circuit configuration for passing a field current through the field winding 114 provided on the rotor 110 will be described. A first end 114a of the field winding 114 is electrically connected or configured to be electrically connectable to the neutral point 126n of the armature winding 125 via a first slip ring 117a. A second end 114b of the field winding 114 is electrically connected or configured to be electrically connectable to a midpoint connection line 114m connected to an external connection terminal 132 via a second slip ring 117b. The external connection terminal 132 is connected or configured to be electrically connectable to a midpoint lead line 2m from the midpoint 2 of the DC power supply 1.

[0044] In addition, the stationary side (neutral point lead wire 126m and midpoint connection wire 114m) that mechanically contacts the first slip ring 117a and the second slip ring 117b to electrically connect them respectively is provided with, for example, brushes that contact each slip ring, but these are not shown in the figure.

[0045] 4 is a flowchart showing the procedure of the control method for the rotary electric machine system according to the first embodiment, that is, the control procedure by the controller 215 of the drive device 200.

[0046] For convenience of explanation, the procedure will be described below taking as an example a case where the rotary electric machine 100 is a drive motor for a vehicle. For example, the procedure starts when the drive key of the vehicle is inserted.

[0047] First, the input unit 215a of the controller 215 receives magnetization condition data as external data. The magnetization condition data is data including magnetization conditions for changing the magnetic force of the variable magnetic force magnet 113 when switching between each operating state. The magnetization condition data received by the input unit 215a is stored in the storage unit 215b.

[0048] Next, the calculation unit 215c of the controller 215 determines whether or not it is necessary to switch the magnetic force of the variable magnetic force magnet 113 (step S02). The determination of whether or not to switch the magnetic force is made by receiving information related to a change in the driving state, such as when the vehicle starts moving or when a gear is changed. If it is not determined that a switch of the magnetic force is necessary (step S02: NO), the controller 215 remains in a standby state.

[0049] If it is determined that switching of the magnetic force is necessary (step S02 YES), the calculation unit 215c accesses the memory unit 215b and reads the magnetization conditions at the time of switching from the magnetization conditions at the time of each switching stored in the memory unit 215b (step S03).

[0050] The calculation unit 215c derives a zero-phase current corresponding to the read magnetization condition (step S04). Based on the derived zero-phase current, the calculation unit 215c further derives a gate voltage of each IGBT 5 that superimposes the zero-phase current, and the output unit 215d outputs a command signal to the three-phase inverter 210. As a result, a zero-phase voltage of the same value is added to the voltage of each phase of the output of the three-phase inverter 210, and this zero-phase voltage causes a zero-phase current to flow.

[0051] Next, a zero-phase current is applied (step S05). Specifically, first, the three-phase inverter 210 outputs the gate voltage of each IGBT 5 derived by the calculation unit 215c for a predetermined time (magnetization time). Here, the predetermined time is the time required for the magnetization state of the variable magnetic force magnet 113 to change.

[0052] Next, the calculation unit 215c determines whether or not operation has been stopped (step S06). That is, it determines whether or not information to the effect that operation of the rotating electric machine 100 is to be stopped has been received. If it has not been determined that operation has been stopped (step S06: NO), steps S02 to S06 are repeated. If it has been determined that operation has been stopped (step S06: YES), control ends. Note that while the same figure has described an example of an operation in which only a zero-phase current is applied to change the magnetic state of the variable magnetic force magnet, the ability to change the magnetic state can be further improved by simultaneously applying a zero-phase current and an armature current.

[0053] 5 is a circuit diagram showing an example of the configuration of a rotating electrical machine system 30 as a comparative example for explaining the effects of the rotating electrical machine system 20 according to the first embodiment. This embodiment has further effects as described below.

[0054] The rotating electric machine system 30 as a comparative example similarly has a field winding 31. Here, both ends of the field winding 31 of the rotating electric machine system 30 as a comparative example are electrically connected or can be electrically connected to a chopper circuit 32 via slip rings. The field current is adjusted by the chopper circuit 32.

[0055] On the other hand, in this embodiment, the field winding 114 is electrically connected to the neutral point 126 n of the armature winding 125 and the midpoint 2 of the DC power supply 1, without providing any additional equipment such as the chopper circuit 32, so that the magnetic force can be changed to the specified value without providing any additional equipment.

[0056] <Explanation of Effects> As described above, the rotary electric machine system 20 according to this embodiment has the following effects by providing the field winding 114 and using the zero-phase current of the three-phase inverter 210.

[0057] (1) The dq-axis current control of the armature winding 125 for load operation of the rotating electric machine 100 and the zero-phase current control for demagnetizing the variable magnetic force magnet 113 can be separated. As a result, the magnetization state can be changed even during load operation of the rotating electric machine 100. In addition, by configuring the field winding so that the conductor cross-sectional area per turn is smaller and the number of turns is larger than that of the armature winding, the magnetomotive force (ampere turns) of the field winding can be increased. Furthermore, by winding the field winding around the variable magnetic force magnet, the magnetic field generated by the field winding can be concentrated on the variable magnetic force magnet. These contributions allow a stronger magnetic field to act on the variable magnetic force magnet within the limited allowable inverter current. This eliminates the trade-off between the variable magnetic force range and preventing demagnetization under load.

[0058] (2) The zero-phase current is applied only for a very short moment, and the zero-phase current does not cause steady copper loss.

[0059] (3) The field current of the field winding 31 can be adjusted by connecting it to the circuit without providing an additional device such as the chopper circuit 32.

[0060] Second Embodiment FIG. 6 is a circuit diagram showing the configuration of a rotating electrical machine system 20a according to a second embodiment.

[0061] This embodiment is a modification of the first embodiment, and the differences between this embodiment and the first embodiment will be described below.

[0062] (1) The drive device 200a of the rotary electric machine system 20a according to this embodiment includes a first three-phase inverter 221 and a second three-phase inverter 222. In the first embodiment, only one three-phase inverter is provided, and the zero-phase voltage output by this three-phase inverter serves as the voltage that energizes the field winding. In contrast, in the second embodiment, the field winding is connected between two three-phase inverters, and the difference between the zero-phase voltages of the three-phase inverters serves as the voltage that energizes the zero-phase current. For example, the first three-phase inverter 221 is controlled to have a positive zero-phase voltage, and the second three-phase inverter 222 is controlled to have a negative zero-phase voltage, thereby generating a zero-phase voltage difference.

[0063] (2) In the rotating electric machine 100a of the rotating electric machine system 20a according to this embodiment, the armature winding 125 has two series of armature winding conductors: a first armature winding series conductor 127 and a second armature winding series conductor 128. The first armature winding series conductor 127 has a first series U-phase conductor 127u, a first series V-phase conductor 127v, and a first series W-phase conductor 127w, which are connected to external connection terminals 131a, 131b, and 131c, respectively. The first armature winding series conductor 127 is connected to or configured to be electrically connectable to the first three-phase inverter 221 via the external connection terminals 131a, 131b, and 131c. The armature winding second series conductor 128 has a second series U-phase conductor 128u, a second series V-phase conductor 128v, and a second series W-phase conductor 128w, which are connected to external connection terminals 132a, 132b, and 132c, respectively. The armature winding second series conductor 128 is connected or configured to be electrically connectable to the second three-phase inverter 222 via the external connection terminals 132a, 132b, and 132c. The armature winding first series conductor 127 functions as a first three-phase armature winding, and the armature winding second series conductor 128 functions as a second three-phase armature winding.

[0064] (3) The first end 114a of the field winding 114 is electrically connected or configured to be electrically connectable to a neutral point 127n of the armature winding first series conductor 127 via a first slip ring 117a. A neutral point lead 127m is provided from the neutral point 127n for connection. Furthermore, the second end 114b of the field winding 114 is electrically connected or configured to be electrically connectable to a neutral point 128n outside the armature winding second series conductor 128 via a second slip ring 117b. A neutral point lead 128m is provided from the neutral point 128n for connection.

[0065] (4) The controller 216 has the same configuration as that of the first embodiment, i.e., an input unit 216a, a memory unit 216b, a calculation unit 216c, and an output unit 216d, but differs from the first embodiment in the parts corresponding to the differences in configuration described above in (1) to (3).

[0066] FIG. 7 is a conceptual partial horizontal cross-sectional view showing an example of the arrangement of the armature winding conductors 126 in the slots 122a of the rotary electric machine according to the second embodiment.

[0067] A plurality of slots 122a are formed at intervals in the circumferential direction on a stator core inner peripheral surface 121x on the radially inner side of the stator core 121. The stator core inner peripheral surface 121x is cylindrical, but in Fig. 7, its cross section is simplified and shown as a straight line.

[0068] In each slot 122a, a U-phase conductor, a U-phase conductor, a V-phase conductor, a V-phase conductor, a W-phase conductor, and a W-phase conductor are arranged in a repeating pattern of six slots. Within each slot 122a, the U-phase conductor, the V-phase conductor, and the W-phase conductor are stacked radially.

[0069] Here, the U-phase conductor refers to the first-series U-phase conductor 127u or the second-series U-phase conductor 128u, the V-phase conductor refers to the first-series V-phase conductor 127v or the second-series V-phase conductor 128v, and the W-phase conductor refers to the first-series W-phase conductor 127w or the second-series W-phase conductor 128w.

[0070] 8 is a conceptual partial horizontal cross-sectional view showing an example of the lamination state of the armature winding conductors 126 in the slots 122a of the rotating electric machine 100 according to the second embodiment. Fig. 8 shows the lamination state of the U-phase conductors in two adjacent slots 122a and the current flow direction when only a zero-phase current is flowing.

[0071] Each slot 122a contains multiple (four in FIG. 8 ) U-phase conductors. Furthermore, each slot 122a contains the same number (two) of first-series U-phase conductors 127u and second-series U-phase conductors 128u stacked alternately. The current flowing through the first-series U-phase conductor 127u is from the back to the front of the page, while the current flowing through the second-series U-phase conductor 128u is from the front to the back of the page, in opposite axial directions (parallel to the rotation axis). For example, in the U-phase, the first-series U-phase conductor 127u functions as a first conductor, and the second-series U-phase conductor 128u functions as a second conductor.

[0072] The reason for this is that in FIG. 6 , zero-phase current flows from one inverter to the other (for example, from neutral point 127n to neutral point 128n). As a result, the direction of the zero current is reversed between the two inverters, i.e., between the conductors of the two series. Meanwhile, although not shown in FIGS. 8 and 9 , the direction of the three-phase AC current flowing through each series is the same in the first series U-phase conductor 127u and the second series U-phase conductor 128u. Therefore, during normal load operation, the two inverters control three-phase AC currents that are roughly in phase.

[0073] The stacking order in two adjacent slots 122a is reversed to each other. That is, in the slot 122a on the left side in Fig. 8, the first series U-phase conductor 127u and the second series U-phase conductor 128u are stacked in this order from the radially inner side, while in the slot 122a on the right side in Fig. 8, the second series U-phase conductor 128u and the first series U-phase conductor 127u are stacked in this order from the radially inner side.

[0074] Fig. 9 is a conceptual partial horizontal cross-sectional view showing a comparative example for describing the effect of an example of arrangement of the armature winding conductors 126 in the slots 122a of the rotating electric machine 100 according to the second embodiment. In the comparative example, only the first-series U-phase conductor 127u is laminated in the slot 122a on the left side of Fig. 8. Also, only the second-series U-phase conductor 128u is laminated in the slot 122a on the right side of Fig. 8. The currents in the U-phase conductors in two adjacent slots 122a flow in the same direction within each slot 122a, and the zero-phase current flowing through the first-series U-phase conductor 127u and the zero-phase current flowing through the second-series U-phase conductor 128u flow in opposite directions in the axial direction.

[0075] The dashed lines in Figure 9 indicate the magnetic fields formed by the zero-phase current flowing through the U-phase conductors in each slot 122a. The magnetic field MF1 formed by the zero-phase current flowing through the first-series U-phase conductor 127u in the left slot 122a rotates counterclockwise. On the other hand, the magnetic field MF2 formed by the zero-phase current flowing through the second-series U-phase conductor 128u in the right slot 122a rotates clockwise. As a result, the magnetic fields MF1 and MF2 do not cancel each other out, and a magnetic field directed radially outward is generated between the two slots 122a. This can lead to a deterioration in transient response characteristics due to an increase in the inductance of the field winding or to unintended behavior due to local magnetic saturation.

[0076] In the rotating electric machine 100 according to this embodiment, the magnetic fields of the armature windings of the same phase housed in adjacent slots 122a cancel each other out, so this problem does not occur.

[0077] The rotating electric machine 100 according to this embodiment is provided with two inverters (a first three-phase inverter 221 and a second three-phase inverter 222). However, the capacity of each inverter is approximately half that of the three-phase inverter 210 according to the first embodiment. Therefore, the rotating electric machine system 20a can achieve the same effects as the rotating electric machine system 20 according to the first embodiment without being significantly larger. Furthermore, the zero-phase voltage for passing the zero-phase current is maximized by halving the voltage of the DC voltage source in the first embodiment, whereas the voltage of the DC voltage source is maximized in the second embodiment. That is, the voltage utilization rate of the zero-phase component is doubled in the second embodiment, enabling more active utilization of the zero-phase current.

[0078] Harmonics caused by switching are superimposed on the current controlled by the inverter. This current pulsation causes iron loss and eddy current loss in the magnet. In the first embodiment, there is one inverter, and the zero-phase-sequence voltage of the inverter is applied directly to the field winding, so it is not possible to take measures against the iron loss caused by the carrier harmonics mentioned above, and it is also not possible to suppress the pulsation of the field current, so it is not possible to suppress the eddy current loss in the variable coercive force magnet wound with the field winding. On the other hand, in the second embodiment, two inverters are used, and the same number of conductors of the systems connected to each inverter are loaded into the slots, so various advantages can be obtained with respect to inverter harmonics as well.

[0079] In an operating state such as one-pulse operation in which the inverter output voltage reaches its maximum, the zero-phase-sequence voltage of the inverter pulsates over time, and the resulting pulsation of the field current cannot be prevented in the first embodiment. On the other hand, in the second embodiment, the zero-phase-sequence voltage of the inverter also pulsates over time, but since the voltage applied to the field winding is the difference between the zero-phase-sequence voltages of the two inverters, if the output voltages of the two inverters are equal, the field current will not pulsate.

[0080] Furthermore, even in an operating state where the inverter output voltage is low and the inverter is operated under PWM (Pulse-Width-Modulation) control, the first embodiment cannot suppress iron loss caused by carrier harmonics. On the other hand, in the second embodiment, by controlling the phase of the carrier harmonics to be shifted between the two inverters, even if the current flowing through the conductors of each system pulsates, the total current in the slot, i.e., the pulsation of the magnetomotive force, is suppressed, and therefore iron loss and eddy current loss in the magnet caused by carrier harmonics can be suppressed.

[0081] According to the embodiments described above, it is possible to provide a rotating electric machine and a rotating electric machine system that can achieve high efficiency.

[0082] [Other Embodiments] Although the embodiments of the present invention have been described above, they are presented as examples and are not intended to limit the scope of the invention. Furthermore, features of each embodiment may be combined. Furthermore, the embodiments may be implemented in various other forms, and various omissions, substitutions, and modifications may be made without departing from the spirit of the invention. The embodiments and their modifications are intended to be included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as set forth in the claims.

[0083] REFERENCE SIGNS LIST 1... DC power supply, 1a... first power supply, 1b... second power supply, 2... midpoint, 2m... midpoint lead wire, 5... insulated gate bipolar transistor (IGBT), 20, 20a... rotating electric machine system, 30... rotating electric machine system as a comparative example, 31... field winding, 32... chopper circuit, 100, 100a... rotating electric machine, 100p... magnetic pole, 110, 110a... rotor, 111... rotor shaft, 112... rotor core, 112a... inner magnet housing outer flux barrier, 112b... inner magnet housing, 112c... inner magnet housing inner flux barrier, 112 d...inner bridge, 112e...outer magnet storage section outer flux barrier, 112f...outer magnet storage section, 112g...outer magnet storage section inner flux barrier, 112h...outer bridge, 112j...outer central flux barrier, 112s...rotor core surface, 113, 113a...variable magnetic force magnet, 114...field winding, 114a...first end, 114b...second end, 114m...midpoint connecting line, 114s...field winding, 115...inner fixed magnetic force magnet, 116...outer fixed magnetic force magnet, 117a...first slip ring, 117b...second slip ring, 120... Stator, 121... stator core, 121x... inner peripheral surface of stator core, 122... teeth portion, 122a... slot portion, 123... yoke portion, 125... armature winding, 126... armature winding conductor, 126m... neutral point lead wire, 126n... neutral point, 126u... U-phase conductor, 126v... V-phase conductor, 126w... W-phase conductor, 127... armature winding first series conductor, 127m... neutral point lead wire, 127n... neutral point, 127u... first series U-phase conductor, 127v... first series V-phase conductor, 127w... first series W-phase conductor, 128... armature winding second series conductor, 128m... neutral point lead wire Lead wire, 128n...neutral point, 128u...second series U-phase conductor, 128v...second series V-phase conductor, 128w...second series W-phase conductor, 130, 131a, 131b, 131c, 132...external connection terminals, 200, 200a...drive device, 210...three-phase inverter, 215...controller, 215a...input section, 215b...storage section, 215c...calculation section, 215d...output section, 216...controller, 216a...input section, 216b...storage section, 216c...calculation section, 216d...output section, 221...first three-phase inverter, 222...second three-phase inverter, MF1, MF2...magnetic field

Claims

1. A rotating electric machine comprising: a stator core; a three-phase armature winding wound around the stator core; a rotor shaft extending in the direction of the rotation axis; a rotor core attached radially outside the rotor shaft; variable magnetic force magnets housed within the rotor core; a field winding arranged near the variable magnetic force magnets and changing the magnetization state of the variable magnetic force magnets when a zero-phase current flows through it; a first slip ring arranged so that one end of the field winding can be electrically connected to the outside; and a second slip ring arranged so that the other end of the field winding can be electrically connected to the outside.

2. The rotating electric machine according to claim 1, wherein said first slip ring is electrically connectable to a neutral point of said three-phase armature winding.

3. A rotating electric machine according to claim 1, wherein the three-phase armature winding is a first three-phase armature winding, and when the first slip ring is electrically connectable to the neutral point of the three-phase armature winding, the second slip ring is electrically connectable to a midpoint that provides an intermediate potential between both ends of a DC power source.

4. A rotating electric machine according to claim 1, wherein the three-phase armature windings are a first three-phase armature winding and a second three-phase armature winding, the first slip ring is electrically connectable to the neutral point of the first three-phase armature winding, and the second slip ring is electrically connectable to the neutral point of the second three-phase armature winding.

5. A rotating electric machine according to claim 4, wherein a plurality of slots are formed on the inner peripheral surface of the stator core at intervals in the circumferential direction, and the number of first conductors constituting the first three-phase armature winding and the number of second conductors constituting the second three-phase armature winding that are housed in each of the plurality of slots are equal to the number of first conductors and second conductors of the same phase that are housed in each of the plurality of slots.

6. A rotating electric machine system comprising: a rotating electric machine according to claim 1; a three-phase inverter that converts DC power from a DC power source into three-phase AC power and supplies the three-phase AC power to the three-phase armature windings; and a controller that controls the three-phase inverter.

7. The rotating electrical machine system according to claim 6, further comprising the DC power supply.

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