JP7363149B2 - reluctance motor - Google Patents

Description

The present invention relates to a reluctance motor.

Since reluctance motors do not have permanent magnets, they are considered promising in terms of cost.

For example, Patent Document 1 proposes a technique for forming a reluctance motor having a segmented rotor by embedding magnetic segments in a non-magnetic conductive member.

JP2006-246571A

However, reluctance motors have lower efficiency than permanent magnet motors.
Therefore, an object of the present invention is to improve the efficiency of a reluctance motor.

One aspect of the reluctance motor according to the present invention includes a stator having a plurality of magnetic poles, a rotor having a plurality of magnetic segments different from the number of magnetic poles of the stator, and the stator is wound in concentrated manner, and the winding directions are mutually mutual. A plurality of identical windings.

According to the present invention, the efficiency of the reluctance motor is improved.

FIG. 1 is a perspective view showing the configuration of a reluctance motor according to a first embodiment. FIG. 2 is a sectional view showing the configuration of the reluctance motor of the first embodiment. FIG. 3 is an enlarged view of salient poles and magnetic segments in the first embodiment. FIG. 4 is a perspective view showing the configuration of a reluctance motor according to the second embodiment. FIG. 5 is a sectional view showing the configuration of a reluctance motor according to the second embodiment. FIG. 6 is an enlarged view of salient poles and magnetic segments in the second embodiment. FIG. 7 is a diagram showing the fundamental wave of an ideal current waveform. FIG. 8 is a diagram showing ideal fundamental waves of self-inductance and mutual inductance. FIG. 9 is a diagram showing the motor torque generated by each ideal fundamental wave. FIG. 10 is a diagram showing a voltage waveform that is a prerequisite for characteristic analysis. FIG. 11 is a diagram showing motor characteristics of the reluctance motor of the first embodiment. FIG. 12 is a diagram showing a current waveform in the reluctance motor of the first embodiment. FIG. 13 is a diagram showing a waveform of self inductance and a waveform of mutual inductance in the reluctance motor of the first embodiment. FIG. 14 is a diagram showing motor characteristics of the reluctance motor of the second embodiment. FIG. 15 is a diagram showing a current waveform in the reluctance motor of the second embodiment. FIG. 16 is a diagram showing the waveforms of self inductance and mutual inductance in the reluctance motor of the second embodiment.

Hereinafter, embodiments of the reluctance motor of the present disclosure will be described in detail with reference to the accompanying drawings. However, in order to avoid the following explanation from becoming unnecessarily redundant and to facilitate understanding by those skilled in the art, more detailed explanation than necessary may be omitted. For example, detailed explanations of well-known matters or redundant explanations of substantially the same configurations may be omitted.

In this specification, embodiments of the present disclosure will be described using as an example a three-phase motor having three-phase windings (sometimes referred to as "coils"). Hereinafter, when distinguishing each phase, they will be referred to as A phase, B phase, C phase, U phase, V phase, and W phase. However, an n-phase motor having n-phase (n is an integer of 4 or more) windings, such as a four-phase or five-phase motor, is also within the scope of the present disclosure.
(Structure of reluctance motor)
FIG. 1 is a perspective view showing the configuration of a reluctance motor according to a first embodiment. FIG. 2 is a sectional view showing the configuration of the reluctance motor of the first embodiment.

The reluctance motor 100 of the first embodiment includes a stator 40 and a rotor 20 having a cylindrical outer shape and inserted into the stator 10. The stator 40 includes a stator core 10 and a coil 30 wound around the stator core 10. The stator 40 generates a rotating magnetic field, and the rotor 20 is rotated by the rotating magnetic field.

Stator core 10 includes a toric body 11 made of a magnetic material and six salient poles 12 protruding from toric body 11 toward rotor 20 . The stator core 10 is formed, for example, by laminating thin steel plates of 0.05 to 1 mm, each of which has an insulating varnish baked onto its surface. The stator core 10 may be formed of a dust core that is less likely to generate eddy currents.

The coils 30 are concentratedly wound around each salient pole 12 of the stator core 10, and a total of six coils 30 are provided. That is, the coil 30 is wound around the stator 40 in a concentrated manner. Since each salient pole 12 becomes a magnetic pole when a current is passed through the coil 30, the stator 40 has six magnetic poles. That is, stator 40 has multiple magnetic poles. The directions of the currents flowing through the six coils 30 are the same as each other, as shown in FIG. 2, and the six coils 30 are wound in the same direction. In this embodiment, each coil 30 is wound clockwise, for example, when viewed from the tip side of the salient pole 12. Further, each coil 30 is wound, for example, from the inner circumferential side to the outer circumferential side. Note that the winding direction of the coils 30 being the same means that the winding direction as seen from the tip side of the salient pole 12 is uniformly clockwise or counterclockwise, from the inner circumferential side to the outer circumferential side. The coil 30 wound in the same manner and the coil 30 wound from the outer circumferential side to the inner circumferential side may coexist.

The rotor 20 has a non-magnetic block 21, a magnetic segment 22, and a shaft 23. The non-magnetic block 21 is made of, for example, aluminum, aluminum alloy, copper, copper alloy such as brass, other non-magnetic conductive metal, or resin. Like the stator 10, the magnetic segments 22 may be formed by laminating steel plates, for example, or may be formed from a dust core. The magnetic segment 22 has an arcuate cross-sectional shape perpendicular to the rotational axis of the rotor 20, and is fitted into and held by the non-magnetic block 21. More specifically, the arcuate cross-sectional shape of the magnetic segment 22 is a cross-sectional shape in which the circumferential surface of the rotor 20 is arcuate and the inner side of the rotor 20 is linear. The arcuate portions and linear portions do not have to be exact circular arcs or straight lines.
Rotor 20 has a plurality of magnetic segments 22 that are different in number from the number of magnetic poles of stator 40 . In this embodiment, rotor 20 has two magnetic segments 22. The shaft 23 protrudes from the rotation center of the non-magnetic block 21 and outputs the rotational force of the reluctance motor 100.
Here, since magnetic torque is not generated in the reluctance motor 100, the torque equation in the reluctance motor 100 is the following equation (1).

Here, the subscripts U, V, and W represent each phase of the motor, iu, iv, and iw represent current values, Lu, Lv, and Lw represent self-inductance values, and Muv, Mvw, and Mwu represent self-inductance values. represents a value. The first term in equation (1) is the torque generated by the change in self-inductance at the rotor position, and the second term in equation (1) is the torque generated by the change in mutual inductance at the rotor position. be. The torque expressed by equation (1) is called reluctance torque.

In the case of a general switched reluctance motor, either self inductance or mutual inductance is often used. In contrast, in the reluctance motor 100 of the first embodiment, since the segment type rotor 20 is used, both self-inductance and mutual inductance contribute to rotation.

In this way, when both self-inductance and mutual inductance are used for rotation, in order to improve the efficiency of the motor, the phase relationship between the fundamental wave of self-inductance and the fundamental wave of mutual inductance is adjusted to the ideal level described later. A close phase relationship is required. In the reluctance motor 100 of the first embodiment, since the plurality of coils 20 are wound in the same direction, the same magnetic poles are generated in the mutually opposing salient poles 12 of the stator 10, and a desirable phase relationship is obtained.

Furthermore, in order to improve the efficiency of the motor, the fundamental wave of self-inductance and the fundamental wave of mutual inductance are required to have a close to ideal phase relationship with respect to the fundamental wave of the current waveform. In the reluctance motor 100 of the first embodiment, the desirable phase relationship is obtained because the magnetic segments 22 have an arcuate shape.
FIG. 3 is an enlarged view of the salient poles 12 and magnetic segments 22 in the first embodiment.

At the end 12b of the salient pole 12 in the rotational direction of the rotor 20, the distance between the salient pole 12 and the rotor 20 is wider than the distance at the center 12a of the salient pole 12. That is, at the end portion 12b of the magnetic pole tip in the rotational direction of the rotor 20, the distance between the magnetic pole tip and the rotor 20 is wider than the distance at the center portion 12a of the magnetic pole tip. With this structure, the inductance changes as the rotor 20 rotates smoothly, and torque ripple is reduced.

Also, at the ends 22b of the arcuate magnetic segments 22 in the rotational direction of the rotor 20, the distance between the magnetic segments 22 and the stator 10 is wider than the distance at the center portion 22a of the magnetic segments 22. This structure also contributes to reducing torque ripple by smoothing changes in inductance as the rotor 20 rotates.
Next, the structure of the second embodiment will be explained.
FIG. 4 is a perspective view showing the configuration of a reluctance motor according to the second embodiment. FIG. 5 is a sectional view showing the configuration of a reluctance motor according to the second embodiment.

The reluctance motor 200 of the second embodiment also includes a stator 10, a rotor 20, and a coil 30, similarly to the first embodiment. The structures of the stator 10 and coil 30 in the second embodiment are the same as those in the first embodiment.

The rotor 20 in the second embodiment includes a non-magnetic block 21, a magnetic segment 25, and a shaft 23. The non-magnetic block 21 is made of non-magnetic conductive metal or resin as in the first embodiment. The magnetic segment 25 has a cross-sectional shape perpendicular to the rotational axis of the rotor 20 in the shape of two arcuate parts overlapping each other, and is fitted and held in the non-magnetic block 21. More specifically, the cross-sectional shape of the magnetic segment 25 is such that the circumferential surface of the rotor 20 has an arc shape, and the inside of the rotor 20 has a polygonal line shape bent toward the magnetic segment 25 side. The arcuate portions and linear portions do not have to be exact circular arcs or straight lines.

In the reluctance motor 200 of the second embodiment, as in the first embodiment, the segment type rotor 20 is used, so that both the fundamental wave of self-inductance and the fundamental wave of mutual inductance contribute to rotation.

Furthermore, in the reluctance motor 200 of the second embodiment, as in the first embodiment, the plurality of coils 20 are wound in the same direction, so that the phase relationship between the fundamental wave of self-inductance and the fundamental wave of mutual inductance is adjusted. This results in a desirable phase relationship.

Furthermore, in the reluctance motor 200 of the second embodiment, the magnetic segment 25 has a shape in which two arcuate parts overlap each other, so that the self-inductance waveform and the mutual inductance waveform are desirable for the current waveform. The phase relationship becomes.
FIG. 6 is an enlarged view of the salient poles 12 and magnetic segments 25 in the second embodiment.

At the end 12b of the salient pole 12 in the rotational direction of the rotor 20, the distance between the salient pole 12 and the rotor 20 is wider than the distance at the center 12a of the salient pole 12. That is, at the end portion 12b of the magnetic pole tip in the rotational direction of the rotor 20, the distance between the magnetic pole tip and the rotor 20 is wider than the distance at the center portion 12a of the magnetic pole tip. With this structure, the inductance changes as the rotor 20 rotates smoothly, and torque ripple is reduced.

Furthermore, even in the end portion 25b of the magnetic segment 25 in the rotational direction of the rotor 20, which has a shape in which two arcuate parts overlap with each other, the distance between the magnetic segment 25 and the stator 10 is the same as the distance at the center portion 25a of the magnetic segment 25. wider than This structure also contributes to reducing torque ripple by smoothing changes in inductance as the rotor 20 rotates.
(Characteristics of reluctance motor)

Hereinafter, in explaining various characteristics of the reluctance motors 100 and 200 of the first embodiment and the second embodiment, first, waveforms having the above-mentioned ideal phase relationship will be explained. The ideal waveform described below is a waveform obtained by optimization calculation using the above-mentioned equation (1) and a genetic algorithm.
FIG. 7 is a diagram showing an ideal fundamental wave current waveform. FIG. 8 is a diagram showing ideal fundamental waves of self-inductance and mutual inductance.

The horizontal axis in FIG. 7 represents the rotation angle in electrical angle, and the vertical axis represents the current value. The horizontal axis in FIG. 8 represents the rotation angle in electrical angle, and the vertical axis represents the inductance value. However, the physical quantities on the vertical axis in each figure have no particular meaning, and FIGS. 7 and 8 represent the phase relationship of each fundamental wave. In each graph below, the A-phase waveform is shown by a solid line, the B-phase waveform is shown by a long broken line, and the C-phase waveform is shown by a short broken line. In each of the graphs below, the mutual inductance of phase B and phase C is shown by a solid line, the mutual inductance of phase C and A is shown by a long broken line, and the mutual inductance of phase A and B is shown by a short broken line.

As shown in FIG. 7, the current waveforms of the A, B, and C phases are trigonometric function waveforms with the same amplitude, and are 120 [edeg. It has a phase difference of ]. The self-inductance waveform and the mutual inductance waveform are trigonometric function waveforms having twice the frequency of the current waveform.

The waveforms of the A-phase self-inductance and the B-phase and C-phase mutual inductance are in phase with each other. The waveforms of the B-phase self-inductance and the C-phase and A-phase mutual inductance are in phase with each other. The waveforms of the C-phase self-inductance and the A-phase and B-phase mutual inductance are in phase with each other.
The fundamental wave of these current waveforms and the fundamental wave of self/mutual inductance are expressed by the following equations.

Here, θ is the rotation angle, Ia, Ib, and Ic are the instantaneous currents of each phase, I is the current amplitude, La, Lb, and Lc are the instantaneous self-inductances of each phase, L is the amplitude of self-inductance, and _L0 is the self-inductance. , Mab, Mbc, and Mca are instantaneous mutual inductances related to the subscript phase, M is the amplitude of the mutual inductance, and M ₀ is the offset amount of the mutual inductance, respectively.

Since each fundamental wave has the phase relationship shown in FIGS. 7 and 8 and the above equations (2) to (10), the output and motor efficiency of the reluctance motor are improved.
FIG. 9 is a diagram showing the motor torque generated by each ideal fundamental wave.
The horizontal axis in FIG. 9 represents the rotation angle in electrical angle, and the vertical axis represents torque.

FIG. 9 shows a total of six torque waveforms representing the torques generated by the self-inductances La, Lb, and Lc, and the torques generated by the mutual inductances Mab, Mbc, and Mca. It can be seen that the total torque due to these six torque waveforms is linear, and stable torque can be obtained. It can also be seen that the torques of the self-inductances La, Lb, and Lc and the torques of the mutual inductances Mab, Mbc, and Mca complement each other, resulting in high torque. Such compensation improves the output power of the reluctance motor. Furthermore, since the output for the same current waveform is improved, the motor efficiency is improved.
Next, motor characteristics of the reluctance motor 100 of the first embodiment described above will be explained.
FIG. 10 is a diagram showing a voltage waveform that is a prerequisite for characteristic analysis.

The horizontal axis in FIG. 10 represents the rotation angle in electrical angle, and the vertical axis represents the voltage value. In FIG. 10, the position of the rotor 20 shown in FIGS. 2 and 5 is an initial position, and the advance angle is 0.0 [edeg. ] The voltage waveforms of each phase are shown. In each graph below, the A-phase waveform is shown by a solid line, the B-phase waveform is shown by a long broken line, and the C-phase waveform is shown by a short broken line. As shown in FIG. 10, the voltage waveforms of each phase of A, B, and C are trigonometric function waveforms with the same amplitude, and are 120 [edeg. ] has a phase difference of
FIG. 11 is a diagram showing motor characteristics of the reluctance motor 100 of the first embodiment.

The horizontal axis in FIG. 11 is the advance angle [edeg. ] represents. In FIG. 11, the advance angle 0.0 [edeg. ], the lead angle is 20 [edeg. ]~55[edeg. ] For each case, the output, iron loss, copper loss, power factor, and efficiency of the reluctance motor 100 of the first embodiment are shown. However, a winding specification is used in which the rated torque is 0.040 [Nm], the rated rotation speed is 72,000 [rpm], and the rated output is 300 [W] at the maximum output point.

From FIG. 11, it can be seen that the advance angle is 25 [edeg. ]～30[edeg. ] It can be seen that the motor efficiency is maximum near . Specifically, a high efficiency of 79.1% was obtained. Even under conditions where a rated output of 300 W was obtained, a high efficiency of 76.8% was obtained. In the reluctance motor 100 of the first embodiment, the magnetic segments 22 having an arcuate cross-sectional shape are used, and it has been found that higher motor efficiency can be obtained than with other cross-sectional shapes such as an arcuate shape. The current waveform and inductance waveform generated in the reluctance motor 100 of the first embodiment will be described below with respect to the voltage waveform at the advance angle where the motor efficiency is maximum.
FIG. 12 is a diagram showing a current waveform in the reluctance motor 100 of the first embodiment.

The horizontal axis in FIG. 12 represents the rotation angle in electrical angle, and the vertical axis represents the current value. In FIG. 12, the actual waveform analyzed by the finite element method for the reluctance motor 100 of the first embodiment is shown as a thin line, and the fundamental wave obtained by Fourier transforming the actual waveform is shown as a thick line. The fundamental waves of each phase are 120 [edeg. ] The trigonometric function waveforms have different movements.
FIG. 13 is a diagram showing a waveform of self inductance and a waveform of mutual inductance in the reluctance motor 100 of the first embodiment.

The horizontal axis in FIG. 13 represents the rotation angle in electrical angle, and the vertical axis represents the inductance value. Also in FIG. 13, the actual waveform analyzed by the finite element method for the reluctance motor 100 of the first embodiment is shown as a thin line, and the fundamental wave obtained by Fourier transforming the actual waveform is shown as a thick line.

The phase relationship between the fundamental wave of self-inductance and the fundamental wave of mutual inductance shown in FIG. 13 matches the phase relationship between the ideal self-inductance waveform and mutual inductance waveform shown in FIG. 8. Furthermore, regarding the phase relationship between the fundamental wave of self-inductance and the fundamental wave of mutual inductance shown in FIG. 13 and the current waveform shown in FIG. It can be seen that the phase relationship is almost equal to that of

In this way, according to the reluctance motor 100 of the first embodiment, a phase relationship close to the ideal phase relationship among the fundamental wave of the current waveform, the fundamental wave of self-inductance, and the fundamental wave of mutual inductance is realized. As a result, in the reluctance motor 100 of the first embodiment, efficiency can be improved by using both self-inductance and mutual inductance as shown in FIG.

In the reluctance motor 100 of the first embodiment, as shown in FIG. 3, the distance between the magnetic segment 22 and the rotor 20 is wider at the end portion 22b of the magnetic segment 22 than at the center portion 22a. Further, at the end portion 12b at the tip of the salient pole 12, the distance between the tip of the salient pole 12 and the rotor 20 is wider than at the center portion 12a. Therefore, as shown in FIG. 13, both the self inductance and the mutual inductance change smoothly as the rotor 20 rotates. As a result, the occurrence of torque ripple is suppressed.
Next, motor characteristics of the reluctance motor 200 of the second embodiment will be explained.
FIG. 14 is a diagram showing motor characteristics of the reluctance motor 200 of the second embodiment.

The horizontal axis in FIG. 14 is the advance angle [edeg. ] represents. In FIG. 14, the advance angle 0.0 [edeg. ], the lead angle is 20 [edeg. ]~55[edeg. ] For each case, the output, iron loss, copper loss, power factor, and efficiency of the reluctance motor 200 of the second embodiment are shown. However, a winding specification is used in which the rated torque is 0.040 [Nm], the rated rotation speed is 72,000 [rpm], and the rated output is 300 [W] at the maximum output point.

From FIG. 14, it can be seen that the advance angle is 25 [edeg. ]～30[edeg. ] It can be seen that the motor efficiency is maximum near . Specifically, a high efficiency of 82.1% was obtained. Even under conditions where a rated output of 300 W was obtained, a high efficiency of 80.1% was obtained. As shown in FIG. 5, the reluctance motor 200 of the second embodiment uses a magnetic segment 25 having a cross-sectional shape in which two arcuate parts overlap each other, and other magnetic segments 25 having a cross-sectional shape such as an arc shape are used. It was found that higher motor efficiency can be obtained than The current waveform and inductance waveform generated in the reluctance motor 200 of the second embodiment will be described below with respect to the voltage waveform at the advance angle where the motor efficiency is maximum.
FIG. 15 is a diagram showing a current waveform in the reluctance motor 200 of the second embodiment.

The horizontal axis in FIG. 15 represents the rotation angle in electrical angle, and the vertical axis represents the current value. In FIG. 15, the actual waveform analyzed by the finite element method for the reluctance motor 200 of the second embodiment is shown as a thin line, and the fundamental wave obtained by Fourier transforming the actual waveform is shown as a thick line. The fundamental waves of each phase are 120 [edeg. ] The result is a trigonometric function waveform with different phases.
FIG. 16 is a diagram showing a waveform of self inductance and a waveform of mutual inductance in the reluctance motor 200 of the second embodiment.

The horizontal axis in FIG. 16 represents the rotation angle in electrical angle, and the vertical axis represents the inductance value. Also in FIG. 16, the actual waveform analyzed by the finite element method for the reluctance motor 200 of the second embodiment is shown as a thin line, and the fundamental wave obtained by Fourier transforming the actual waveform is shown as a thick line.

The phase relationship between the fundamental wave of self-inductance and the fundamental wave of mutual inductance shown in FIG. 16 matches the phase relationship between the ideal fundamental wave of self-inductance and the fundamental wave of mutual inductance shown in FIG. 8. Furthermore, regarding the phase relationship between the fundamental wave of self-inductance and the fundamental wave of mutual inductance shown in FIG. 16 and the current waveform shown in FIG. It can be seen that the phase relationship is almost equal to that of

In this way, according to the reluctance motor 200 of the second embodiment, a phase relationship close to the ideal phase relationship among the fundamental wave of the current waveform, the fundamental wave of self-inductance, and the fundamental wave of mutual inductance is realized. As a result, even in the reluctance motor 200 of the second embodiment, efficiency can be improved by using both self-inductance and mutual inductance as shown in FIG.

Also in the reluctance motor 200 of the second embodiment, as shown in FIG. 6, the distance between the magnetic segment 25 and the rotor 20 is wider at the end portion 25b of the magnetic segment 25 than at the center portion 25a. Further, at the end portion 12b at the tip of the salient pole 12, the distance between the tip of the salient pole 12 and the rotor 20 is wider than at the center portion 12a. Therefore, as shown in FIG. 16, both the self inductance and the mutual inductance change smoothly as the rotor 20 rotates. As a result, the occurrence of torque ripple is suppressed.

The embodiments described above should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is indicated by the claims rather than the embodiments described above, and it is intended that all changes within the meaning and range equivalent to the claims are included.

100, 200: Reluctance motor 10: Stator 11: Toric body 12: Salient pole 20: Rotor 21: Non-magnetic blocks 22, 25: Magnetic segment 23: Shaft 30: Coil

Claims (3)

a stator having multiple magnetic poles;
a rotor having a plurality of magnetic segments different from the number of magnetic poles of the stator;
a plurality of windings wound on the stator in a concentrated manner and having the same winding direction;
Equipped with
The rotor has a cylindrical outer shape and is inserted into the stator,
The magnetic segment is a reluctance motor in which a cross-sectional shape perpendicular to the rotational axis of the rotor is a shape in which two arcuate shapes partially overlap each other. 2. The reluctance motor according to claim 1 , wherein at an end in the rotational direction of the rotor at the tip of the magnetic pole, a gap between the tip and the rotor is wider than a gap at a central portion of the tip. The reluctance motor according to claim 1 or 2, wherein a distance between the magnetic segment and the stator at an end of the magnetic segment in the rotational direction of the rotor is wider than a distance at a central portion of the magnetic segment.

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