ELECTRIC ROTATING MACHINE

Abstract

Electric rotating machine (1), comprising: a stator (10); and a rotor (20), wherein the stator (10) comprises: Stator coils (12); Cores (15), each consisting at least partially of a magnetic material and wound around the stator coils (12); and a yoke (16) made of a non-magnetic material which supports the cores (15), and that the rotor (20) comprises: rotor coils (22); and a rotor core (21) consisting of slots (24) which accommodate the rotor coils (22), where a first capacitor (17) is connected to each of the stator coils (12) to form a first resonant circuit (18), a second capacitor (27) is connected to each of the rotor coils (22) to form a second resonant circuit (28); and the first resonant circuit (18) and the second resonant circuit (28) have approximately the same resonant frequency, wherein the electric rotating machine (1) is characterized in that the stator coils (12) are multi-phase stator coils and comprise a first-phase stator coil for conducting a current in a first phase of two or more phase currents, and a second-phase stator coil for conducting a current in a second phase of the two or more phase currents; the rotor coils (22) are multi-phase rotor coils and comprise a rotor coil for a first phase for conducting an induced current induced by the conduction of a current in the first phase of the two or more phase currents, and a rotor coil for a second phase for conducting an induced current induced by the conduction of a current in the second phase of the two or more phase currents; one of the first capacitors (17) is connected to the stator coil for the first phase to form one of the first resonant circuits (18) to conduct a current in the first phase of the two or more phase currents, and another of the first capacitors (17) is connected to the stator coil for the second phase to form another of the first resonant circuits (18) to conduct a current in the second phase of the two or more phase currents; one of the second capacitors (27) for forming one of the second resonant circuits (28) is connected to the rotor coil for the first phase to conduct an induced current induced by the conduction of a current in the first phase of the two or more phase currents, and another of the second capacitors (27) for forming another of the second resonant circuits (28) is connected to the rotor coil for the second phase to conduct an induced current induced by the conduction of a current in the second phase of the two or more phase currents; and one of the second resonant circuits (28) for conducting the induction current induced by the conduction of a current in the first phase is electrically insulated from another of the second resonant circuits (28) for conducting the induction current induced by the conduction of a current in the second phase.

Description

[Technical field]

[0001] The present invention relates to an electric rotating machine. [Background of the technology]

[0002] Induction motors are known as rotating electrical machines, and are used to power hybrid electric vehicles and electric cars. JP 2017-038511 A describes a well-known induction motor. In this well-known induction motor, cores, such as those made of iron, are not used to significantly reduce weight. Furthermore, the rotor and stator are made of non-magnetic materials. [State of the art]

[0003] JP 2008-182 782 A discloses an electrical rotating machine with a stator and a rotor. The stator comprises stator coils, cores each made at least partially of a magnetic material and wound with the stator coils, and a yoke made of a non-magnetic material that supports the cores. The rotor comprises permanent magnets. [Summary of the invention][Technical problem]

[0004] By manufacturing a rotor and stator from non-magnetic materials, as described in JP 2017-038511 A, a significant reduction in the weight of induction motors can be expected. On the other hand, reducing the degree of magnetic coupling between the rotor and stator windings leads to a reduction in the induced current flow through the rotor coils of the rotor windings when an alternating current flows through the stator coils of the stator windings.

[0005] In the induction motor described in JP 2017-038511 A, in order to increase the induced current flowing through the rotor windings, magnetic resonance coupling is caused by passing alternating currents at high frequencies through the stator windings and by inserting capacitors in the rotor windings and in the stator windings to form resonant circuits whose resonant frequencies are as high as the high frequencies.

[0006] However, the resonance motor system described in JP 2017-038511 A has the problem of reducing the efficiency and complexity of controlling an inverter, as well as increasing the copper loss resulting from the resonance frequencies due to the high-frequency phase currents flowing through the stator windings.

[0007] Another problem is that the flow of the induced current decreases with increasing deviation of the current frequency from the resonance frequency, so that the operating range is limited because during the occurrence of magnetic resonance coupling, the coils and capacitors operate in a resonance state in which the impedance of the coils and capacitors becomes low, although a large current flow is allowed.

[0008] In view of the foregoing, an object of the present invention is to provide an electric rotating machine capable of not only restricting a reduction in efficiency, the complexity of controlling an inverter, and the copper loss due to the resonance frequency, but also increasing the flow of the induced current. [Solution to the task]

[0009] An electric rotating machine is provided, comprising: a stator and a rotor. The electric rotating machine is characterized in that the stator comprises: stator coils; cores, each made at least partially of a magnetic material and wound by the stator coils; and a yoke made of a non-magnetic material that supports the cores, and in that the rotor comprises: rotor coils;and a rotor core consisting of slots that accommodate the rotor coils. A first capacitor is connected to each of the stator coils to form a first resonant circuit. A second capacitor is connected to each of the rotor coils to form a second resonant circuit. The first resonant circuit and the second resonant circuit have approximately the same resonant frequency. The electric rotating machine is characterized in that the stator coils are multi-phase stator coils and include a first-phase stator coil for conducting a current in a first phase of two or more phase currents, and a second-phase stator coil for conducting a current in a second phase of the two or more phase currents;the rotor coils are multi-phase rotor coils and comprise a rotor coil for a first phase for conducting an induced current induced by the conduction of a current in the first phase of the two or more phase currents, and a rotor coil for a second phase for conducting an induced current induced by the conduction of a current in the second phase of the two or more phase currents; one of the first capacitors for forming one of the first resonant circuits is connected to the stator coil for the first phase for conducting a current in the first phase of the two or more phase currents, and another of the first capacitors for forming another of the first resonant circuits is connected to the stator coil for the second phase for conducting a current in the second phase of the two or more phase currents;one of the second capacitors for forming one of the second resonant circuits is connected to the rotor coil for the first phase to conduct an induced current induced by the conduction of a current in the first phase of the two or more phase currents, and another of the second capacitors for forming another of the second resonant circuits is connected to the rotor coil for the second phase to conduct an induced current induced by the conduction of a current in the second phase of the two or more phase currents; and one of the second resonant circuits for conducting the induced current induced by the conduction of a current in the first phase is electrically insulated from another of the second resonant circuits for conducting the induced current induced by the conduction of a current in the second phase; [Advantageous effect of the invention]

[0010] The present invention limits the reduction in efficiency, the complexity of controlling an inverter, and the copper loss due to the resonant frequency and increases the flow of the induced current. [Brief description of the drawings] Fig. 1 is a cross-sectional view of an electrically rotating machine according to the invention. Fig. Figure 2 is a schematic diagram of the connection of stator coils and the connection of rotor coils. Fig. Figure 3 shows the torque-frequency curve of the electrically rotating machine. Fig. Figure 4 is a simulation of the magnetic flux density during magnetic resonance. Fig. Figure 5 is a schematic diagram of a modification of an electric rotating machine. Fig. 6 is a schematic view of a capacitance changing device. [Detailed description]

[0011] In the present embodiment, an electric rotating machine is disclosed, comprising: a stator and a rotor. The electric rotating machine is characterized in that the stator comprises: stator coils; cores each made at least partially of a magnetic material, with the stator coils wound thereon; and a yoke made of a non-magnetic material that supports the cores, and the rotor comprises: rotor coils; and a rotor core consisting of slots that accommodate the rotor coils. The present invention restricts a reduction in efficiency, the complexity of controlling an inverter, and copper loss due to the resonant frequency, and increases the flow of induced current. [Embodiment(s)]

[0012] Referring to the accompanying drawings, an electric rotating machine according to the invention will be described.

[0013] Referring to Fig. 1, an electric rotating machine 1 takes the form of a low-frequency magnetic resonance induction motor, in which high-efficiency magnetic resonance occurs upon passage of a low-frequency current. The electric rotating machine 1 comprises a stator 10 and a rotor 20 separated from the stator 10 by an air gap. The rotor 20, which has a rotating shaft 5, is supported by a motor housing (not shown) for rotation about an axis of the rotating shaft 5 relative to the stator 10.

[0014] The term "radial direction" refers to a direction perpendicular to the axis of the rotating shaft 5 and directed outward. The term "radial outer" refers to the side radially distant from the axis of the rotating shaft 5. The term "radial inner" refers to the side radially closest to the axis of the rotating shaft 5.

[0015] The term "circumferential direction" refers to a direction along the circumference of a circle encircling the axis of the rotating shaft 5. The term "axial direction" refers to a direction along or parallel to the axis of the rotating shaft 5.

[0016] The stator 10 includes stator coils 12; stator cores 15, each at least partially made of a magnetic material and wound by the stator coils 12; and a yoke 16 made of a non-magnetic material that supports the cores 15.

[0017] The stator coils 12 can be divided into two or more groups, each for one of two or more corresponding phases of multi-phase alternating currents. In the present embodiment, three-phase alternating currents are used, so the stator coils 12 are divided into three groups for the W phase, the V phase, and the U phase of the three-phase alternating currents. Concentrated windings or distributed windings can be used for the winding of the stator coils 12, but concentrated windings are preferred to reduce stator copper loss.

[0018] For the winding of the stator coils 12, stranded wires, rectangular wires and round wires can be used, but stranded wires are preferred for the stator coils 12 in order to limit the occurrence of copper loss caused by the stray flux linked to the wire.

[0019] Each of the stator cores 15 is a multi-layer electromagnetic structure resulting from the lamination of electromagnetic steel plates as a highly permeable material in a direction along or parallel to the rotation axis of the stator 10.

[0020] The stator cores 15 are designed to act as an intermediate pole because they are made of a magnetic material. This increases the inductance of each stator coil 12, so that the stator coils 12 slightly resonate magnetically in response to the passage of low-frequency phase currents.

[0021] The yoke 16, which is located on the outer peripheral side of the stator 10 with respect to the stator cores 15, is made of a polyphenylene sulfide resin (PPS) as a non-magnetic material.

[0022] The yoke 16 supports the stator cores 15 on their radial outer sides to prevent the stator cores 15 from falling away from the stator 10. Furthermore, the yoke 16 connects two adjacent stator cores 15 to each other.

[0023] Furthermore, the stator 10 includes a bridge 19 made of a non-magnetic material. The bridge 19, located on the inner peripheral side of the stator 10 relative to the stator cores 15, is made of a polyphenylene sulfide resin (PPS) as a non-magnetic material.

[0024] The bridge 19 supports the stator cores 15 on their radially inner side to prevent the stator cores 15 from falling away from the stator 10. Furthermore, the bridge 19 connects two adjacent stator cores 15 to each other. The bridge 19 cooperates with the yoke 16 to improve or increase the rigidity of the stator 10.

[0025] An electric current flows through each of the stator coils 12, which are configured as described to generate a magnetic field. Due to the passage of three-phase alternating currents through the stator coils 12 of the stator 10, a rotating magnetic field is generated that rotates in the circumferential direction. The magnetic flux generated at the stator 10 causes interlinkage with the rotor 20, thus generating torque.

[0026] The rotor 20 includes rotor coils 22 and a rotor core 21 formed with slots 24 that receive the rotor coils 22. Furthermore, the rotor 20 includes rotor teeth 23 evenly distributed in the circumferential direction. The rotor coils 22 are wound around the rotor core 21 and the rotor teeth 23.

[0027] The rotor core 21 is a multilayer electromagnetic structure resulting from the lamination of electromagnetic steel plates. The grooves 24 are grooves cut radially inward from the circumference of the rotor core, extending along the rotation axis of the rotating shaft 5.

[0028] The rotor coils 22 are accommodated in the slots 24 and wound as distributed windings. Specifically, the rotor coils 22 are wound as distributed windings, so that the conductors extend forward and backward around the rotating shaft 5.

[0029] Referring to Fig. 2, a three-phase star (Y) connection is used in the stator 10, in which three windings, each comprising at least one stator coil 12, are connected. In each of the windings, a first capacitor 17 is connected in series with a stator coil 12. The stator coil 12 and the first capacitor 17, which is connected to the stator coil 12, form a first resonant circuit 18. The first resonant circuit 18 is an LC series resonant circuit.

[0030] On the other hand, each of the windings of the rotor 20 includes a second capacitor 27 connected in series with a rotor coil 22. The rotor coil 22 and the second capacitor 27, which is connected in series with the rotor coil 22, form a second resonant circuit 28.

[0031] Thus, the second resonant circuit 28 is an LC series resonant circuit. The second resonant circuit 28 of each of the three phases is electrically isolated from the resonant circuit 28 of each of the other phases. In other words, the second resonant circuits 28 of the three phases are not grounded. In the present embodiment, a resonant frequency of the first resonant circuit 18 and a resonant frequency of the second resonant circuit 28 are approximately the same.

[0032] In the present embodiment, the frequencies at which the three-phase alternating currents flow through stator coils 12 are low frequencies ranging from several tens of Hz to several hundred thousand Hz. Thus, the first resonant circuit 18 and the second resonant circuit 28 are configured such that the resonant frequencies of the first and second resonant circuits 18 and 28 approximately equal to certain frequencies selected from a range of frequencies of the three-phase alternating currents. The term "approximately" herein refers to the vicinity of a certain frequency, with a difference equal to at most the slip frequency of the rotor 20 relative to the stator 10.

[0033] With the configuration just described, the three-phase currents flowing through the stator coils 12 are used not only to excite the rotor coils 22 of the rotor 20, but also to generate a magnetic resonance coupling between the first resonant circuit 18 and the second resonant circuit 28 to supply power to the rotor 20.

[0034] Since the stator cores 15 in the present embodiment are made of a magnetic material and the yoke is made of a non-magnetic material, the amount of magnetic material used in the stator 10 is significantly reduced. This achieves a significant reduction in the weight of the rotating electric machine 1 and a significant reduction in the size of the rotating electric machine 1, as well as a reduction in iron loss in the stator 10.

[0035] In addition, the product of the inductance of the stator coil 12 and the capacitance of the first capacitor 17 in the present embodiment is approximately equal to the product of the inductance of the rotor coil 22 and the capacitance of the second capacitor 27.

[0036] In the present embodiment, the stator coils 12 include a first-phase stator coil for conducting a current in a first phase of two or more phase currents, and a second-phase stator coil for conducting a current in a second phase of the two or more phase currents. The rotor coils 22 include a first-phase rotor coil for conducting an induction current induced by the conduction of a current in the first phase of the two or more phase currents, and a second-phase rotor coil for conducting an induction current induced by the conduction of a current in the second phase of the two or more phase currents.The first capacitor 17 is connected to the stator coil for the first phase to form the first resonant circuit 18 for conducting a current in the first phase of the two or more phase currents, and the first capacitor 17 is connected to the stator coil for the second phase to form the first resonant circuit 18 for conducting the current in the second phase of the two or more phase currents. The second capacitor 27 is connected to the rotor coil for the first phase to form the second resonant circuit 28 for conducting an induced current induced by the conduction of a current in the first phase of the two or more phase currents, and the second capacitor 27 is connected to the rotor coil for the second phase to form the second resonant circuit 28 for conducting an induced current induced by the conduction of a current in the second phase of the two or more phase currents.The second resonant circuit 28 for conducting the induction current induced by the conduction of a current in the first phase is electrically isolated from the second resonant circuit 28 for conducting the induction current induced by the conduction of a current in the second phase.

[0037] The Fig. 3 represents the torque-frequency characteristic of the electrically rotating machine 1, which is determined by an analysis of the electromagnetic fields, wherein the horizontal axis represents the rotation frequency of the rotor 20 (hereinafter also called “rotor rotation frequency”), and the vertical axis represents the torque of the rotor 20.

[0038] In Fig. 3, "Fs" denotes the frequency of a rotating magnetic field generated by the stator 10. The frequency "Fs" is often referred to as the fundamental frequency at which the stator coils 12 of the stator 10 are excited and may be referred to as the stator excitation fundamental frequency. The frequency "Fs" is an excitation or excitation frequency at which the rotor coils 22 of the rotor 20 are excited.

[0039] In Fig. 3, the frequency “Fs” includes variable frequencies of 100 Hz, 150 Hz, 175 Hz and 200 Hz. Fig. The characteristic curves shown in Figure 3 are determined by recording the torque and frequency values for different speeds of the rotor 20, with the frequency Fs being maintained at a selected frequency of 100 Hz, 150 Hz, 175 Hz and 200 Hz.

[0040] As in Fig. As shown in Figure 3, the electric rotating machine 1 generates a high-amplitude torque when the rotor rotation frequency approximately corresponds to a particular frequency called the resonant frequency, at which magnetic resonance coupling occurs between the first resonant circuit 18 and the second resonant circuit 28. The magnetic resonance coupling allows not only operation of the electric rotating machine 1 for converting electrical energy to mechanical energy, or drive mode, but also operation for converting mechanical energy to electrical energy, or generator mode.

[0041] The Fig. Figure 4 shows the result of the simulation of the magnetic flux density during the electromagnetic resonance between the first resonant circuit 18 and the second resonant circuit 28. This magnetic flux density results from the excitation of the stator 10, which is achieved by passing 900 ampere-turns (AT) through the stator coil 12 to generate a stator magnetomotive force.

[0042] As in Fig. 4, the magnetic flux density in each of the stator cores 15 made of a magnetic material is high, so that a closed magnetic circuit is provided because each of the stator cores 15 serves as an intermediate pole.

[0043] Also visible is that the magnetic flux density is high in sections of the yoke 16, providing a closed magnetic circuit. This demonstrates that the magnetic resonance coupling between the first resonant circuit 18 and the second resonant circuit 28 allows for the conversion of electrical to mechanical energy.

[0044] In the present embodiment, the electric rotating machine 1 is designed to increase the coupling factor k instead of the quality factor or Q factor. This makes it possible to induce magnetic resonance with a conventional magnetomotive force generated by a current of several hundred AT.

[0045] The electric rotating machine 1, which in the present embodiment is in the form of an induction motor, has electromagnetic resonance induced by a low frequency, so that a secondary excitation system capable of bidirectional power supply can be formed between the stator 10 and the rotor 20 to generate current for regulating a slip frequency of the rotor 20, thereby implementing a brushless motor system. This brushless motor system has a reduced size and increased rigidity because the brush for power transmission is omitted. The term "brushless motor system" herein refers to a motor system in which electromagnetic coupling allows power transmission without contact between a brush and a slip ring.

[0046] A known approach to increasing the coupling factor k is to excite air-core coils at a high frequency. Instead of this approach, it has been found desirable to form the stator core 15 from a magnetic material to increase the magnetic coupling factor between the stator coil 12 and the rotor coil 22.

[0047] In view of the foregoing, the stator coil 15 of the electric rotating machine 1 in the present embodiment serves as an intermediate pole because the stator 10 has a stator core 15 made of a magnetic material.

[0048] Furthermore, in the present embodiment, the stator coils are magnetically coupled by the high flux density generated at resonance at a location with low magnetic permeability (ie, at the yoke 16 made of a non-magnetic material) between two adjacent stator cores 15, without resorting to magnetic paths conventionally formed by connecting the stator cores 15 to a rear yoke.

[0049] The configuration in which the stator cores 15 made of a magnetic material are arranged within the non-magnetic, resin-formed, lightweight yoke 16 provides structural limitation of the iron loss resulting from the magnetic material due to a significant reduction in the amount of magnetic material used.

[0050] This also maximizes the magnetic permeability between the stator coil 12 and the rotor coil 22. Furthermore, the yoke 16 can thus support the stator cores 15.

[0051] In addition, the stator cores 15 acting as intermediate poles lead to a considerable reduction in the leakage of the magnetic flux linking the stator coils 12, which leads to a reduction in the copper loss of the stator coils 12.

[0052] As in Fig. As shown in Figure 5, a power supply unit 30, which is connected to the rotor coils 22 of the rotor 20 by a resonant coupling, can be provided separately from the stator coils 12. The power supply unit 30 includes excitation coils 32 and a capacitor (not shown) comparable to the first capacitor 17. The power supply unit 30 is provided integrally on the stator 10 or separately from the stator 10.

[0053] In this case, too, a frequency of a current flowing through the excitation coils 32, that is, a frequency during magnetic resonance between the excitation coils 32 and the rotor coils 22, should be a low frequency between several tens of Hz and several hundred thousand Hz, and the rotating electric machine 1 should preferably be configured to increase the coupling factor k. This allows the secondary excitation system to be formed that is capable of bidirectional power supply between the stator 10 and the rotor 20 to generate power for regulating a slip frequency of the rotor 20.

[0054] In the Fig. In the electric rotating machine 1 shown in Figure 5, an inverter 40 is connected to the stator 10 to supply three-phase alternating currents to the stator coils 12 of the stator 10. On the other hand, an inverter 50 is connected to the excitation coils 32 to supply three-phase alternating currents to the excitation coils 32.

[0055] In order to expand the operating range of the electric rotating machine 1, the first capacitor 17 and the second capacitor 27 are preferably designed as variable capacitors.

[0056] In both the first capacitor 17 and the second capacitor 27, the capacitance of the capacitor is variable by changing the area of the opposing conductive plates separated by a dielectric. Furthermore, in both the first capacitor 17 and the second capacitor 27, the capacitance of the capacitor is variable by changing the separation distance between the opposing conductive plates.

[0057] In both the first capacitor 17 and the second capacitor 27, the capacitance of the capacitor is variable by changing the permittivity (or relative permittivity) of the dielectric separating the opposing conductive plates.

[0058] Among the three methods described above for changing the capacitance of a capacitor, the method in which the area of the opposing conductive plates is changed to vary the capacitance, as shown in Fig. 6, is carried out by providing n capacitors C1, C2, ..., Cn and selectively connecting some or all of the capacitors in parallel depending on a combination of open / closed states of switches S1, S2, ..., Sn.

[0059] A change in the capacitance of the first capacitor 17 or the second capacitor 27 causes a change in the resonant frequency of the associated first resonant circuit 18 or second resonant circuit 28. Thus, the inverter 40 must change the frequencies of the current flowing through the stator coils 12 such that they correspond to the resonant frequency after the change.

[0060] As previously described, the switches S1, S2, ..., Sn, which are provided for changing the capacitance of the first capacitor 17 and the second capacitor 27, form a capacitance-changing device according to the invention. The inverter 40, which changes the frequencies of the current flowing through the stator coils 12, forms a frequency-changing device according to the invention.

[0061] Furthermore, the electric rotating machine 1 may take the form of a linear motor, provided that it has a stator instead of the stator 10 and a rotor instead of the rotor 20.

[0062] In the present embodiment, the stator 10 includes: stator coils 12; stator cores 15, each at least partially made of a magnetic material, around which the stator coils 12 are wound; and a yoke 16 made of a non-magnetic material that supports the cores 15.

[0063] The rotor 20 includes: rotor coils 22; and a rotor core 21 consisting of slots 24 that receive the rotor coils 22.

[0064] This configuration allows a reduction in the weight of the electric rotating machine 1 because the yoke 16 is a non-magnetic structure.

[0065] This results in a significant improvement in the magnetic resonance properties between a stator coil 12 and a rotor coil 22, resulting in an increase in the induced current in the rotor coil 22 when an electric current is passed through the stator coil 12.

[0066] This results in a significant reduction in the magnetic leakage flux linking the stator coil 12 because the magnetic leakage flux links the rotor 20, which contributes to a reduction in copper loss.

[0067] This results in a reduction in the amount of magnetic material compared to a case where a yoke made of a magnetic material is used, which contributes to a reduction in iron loss and a reduction in the weight of the electric rotating machine 1.

[0068] Referring to Fig. 2, in the present embodiment, a first capacitor 17 is connected or connected in series to each of the stator coils 12 to form a first resonant circuit 18, while a second capacitor 27 is connected or connected in series to each of the rotor coils 22 to form a second resonant circuit 28. The first resonant circuit 18 and the second resonant circuit 28 each have approximately the same resonant frequency.

[0069] As just described, by utilizing magnetic resonance coupling, the induced current induced in the rotor coils 22 (or the stator coils 12) is increased when a current at the resonant frequency is passed through the stator coils 12 (or the rotor coils 22).

[0070] In the present embodiment, the product of the inductance of the stator coil 12 and the capacitance of the first capacitor 17 is approximately equal to the product of the inductance of the rotor coil 22 and the capacitance of the second capacitor 27.

[0071] As just described, by utilizing magnetic resonance coupling, the induced current induced in the rotor coils 22 (or the stator coils 12) is increased when a current at the resonant frequency is passed through the stator coils 12 (or the rotor coils 22).

[0072] In the present embodiment, the stator coils 12 are multi-phase stator coils and include a first-phase stator coil for conducting a current in a first phase of two or more phase currents, and a second-phase stator coil for conducting a current in a second phase of the two or more phase currents. The rotor coils 22 are multi-phase rotor coils and include a first-phase rotor coil for conducting an induction current induced by conducting a current in the first phase of the two or more phase currents, and a second-phase rotor coil for conducting an induction current induced by conducting a current in the second phase of the two or more phase currents.One of the first capacitors 17 is connected to the stator coil for the first phase to form one of the first resonant circuits 18 for conducting a current in the first phase of the two or more phase currents, and another of the first capacitors 17 is connected to the stator coil for the second phase to form another of the first resonant circuits 18 for conducting the current in the second phase of the two or more phase currents.One of the second capacitors 27 is connected to the rotor coil for the first phase to form one of the second resonant circuits 28 for conducting an induced current induced by the conduction of a current in the first phase of the two or more phase currents, and another of the second capacitors 27 is connected to the rotor coil for the second phase to form another of the second resonant circuits 28 for conducting an induced current induced by the conduction of a current in the second phase of the two or more phase currents. One of the second resonant circuits 28 for conducting the induced current induced by the conduction of a current in the first phase is electrically insulated from another of the second resonant circuits 28 for conducting the induced current induced by the conduction of a current in the second phase.

[0073] As just described, the occurrence of resonance between rotor coils 22 of different phases is prevented while a current having the resonance frequency flows through the stator coils, thus preventing the operation of the rotating electric machine 1 from becoming unstable. Since three-phase windings are short-circuited in the rotating electric machine described in JP 2017-038511 A, the operation of the rotating electric machine is likely to become unstable due to the occurrence of resonance among the phase windings.

[0074] Furthermore, the electric rotating machine 1 in the present embodiment includes a capacitance changing device in the form of switches S1, S2, ..., Sn for changing the capacitance of the first capacitor 17 and the capacitance of the second capacitor 27, and a frequency changing device in the form of the inverter 40 for changing the frequencies of the current flowing through the stator coils 12.

[0075] This allows an extension of the operating range of the electric rotating machine 1 because the capacitances of the stator capacitors and the rotor capacitors are variable.

[0076] Furthermore, the currents flowing through the stator coils 12 of the stator 10 are not limited to three-phase currents. More than three-phase currents can also be conducted through the stator 10. A three-phase star connection of the rotor coils 22 is preferred, but the rotor can also take the form of a squirrel-cage rotor.

[0077] In the present embodiment, the electric rotating machine 1 is an electric rotating machine with an inner rotor, but the present invention can also be applied to electric rotating machines with an outer rotor.

[0078] In addition, the electric rotating machine 1 in the present embodiment is an electric rotating machine with a radial pitch, and the present invention can also be applied to electric rotating machines with an axial pitch.

[0079] Although the disclosure relates to the present embodiment, but is not limited thereto, it will be apparent to those skilled in the art that changes may be made without departing from the spirit of the present invention. All possible modifications and equivalents are to be considered as covered by the appended claims. [Description of reference symbols] 1 Electric rotating machine; 10 Stator; 12 stator coil; 15 core; 16 yoke; 17 First capacitor; 18 First resonant circuit; 20 rotor; 21 rotor core; 22 rotor coil; 24 grooves; 27 Second capacitor; 28 Second resonant circuit; 40 Frequency changing device, in the present embodiment in the form of an inverter; S1,S2...Sn capacitance changing device, in the present embodiment in the form of switches.

Claims

[1] Electric rotating machine (1), comprising: a stator (10); and a rotor (20), wherein the stator (10) comprises: Stator coils (12); Cores (15), each consisting at least partially of a magnetic material and wound around the stator coils (12); and a yoke (16) made of a non-magnetic material which supports the cores (15), and that the rotor (20) comprises: rotor coils (22); and a rotor core (21) consisting of slots (24) which accommodate the rotor coils (22), where a first capacitor (17) is connected to each of the stator coils (12) to form a first resonant circuit (18), a second capacitor (27) is connected to each of the rotor coils (22) to form a second resonant circuit (28); and the first resonant circuit (18) and the second resonant circuit (28) have approximately the same resonant frequency, wherein the electric rotating machine (1) characterized by is that the stator coils (12) are multi-phase stator coils and comprise a first-phase stator coil for conducting a current in a first phase of two or more phase currents, and a second-phase stator coil for conducting a current in a second phase of the two or more phase currents; the rotor coils (22) are multi-phase rotor coils and comprise a rotor coil for a first phase for conducting an induced current induced by the conduction of a current in the first phase of the two or more phase currents, and a rotor coil for a second phase for conducting an induced current induced by the conduction of a current in the second phase of the two or more phase currents; one of the first capacitors (17) is connected to the stator coil for the first phase to form one of the first resonant circuits (18) to conduct a current in the first phase of the two or more phase currents, and another of the first capacitors (17) is connected to the stator coil for the second phase to form another of the first resonant circuits (18) to conduct a current in the second phase of the two or more phase currents; one of the second capacitors (27) for forming one of the second resonant circuits (28) is connected to the rotor coil for the first phase to conduct an induced current induced by the conduction of a current in the first phase of the two or more phase currents, and another of the second capacitors (27) for forming another of the second resonant circuits (28) is connected to the rotor coil for the second phase to conduct an induced current induced by the conduction of a current in the second phase of the two or more phase currents; and one of the second resonant circuits (28) for conducting the induction current induced by the conduction of a current in the first phase is electrically insulated from another of the second resonant circuits (28) for conducting the induction current induced by the conduction of a current in the second phase. [2] Electric rotating machine (1) according to claim 1, characterized by, that: the product of the inductance of the stator coil (12) and the capacitance of the first capacitor (17) is approximately equal to the product of the inductance of the rotor coil (22) and the capacitance of the second capacitor (27). [3] The electric rotating machine (1) according to claim 2, characterized by in that it comprises: a capacitance changing device for changing the capacitance of the first capacitor (17) and the capacitance of the second capacitor (27); and a frequency changing device (40) for changing the frequencies of the current flowing through the stator coils (12).

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