WO2024150444A1

WO2024150444A1 - Switched reluctance motor apparatus

Info

Publication number: WO2024150444A1
Application number: PCT/JP2023/000895
Authority: WO
Inventors: 正一田中
Original assignee: 正一田中
Priority date: 2023-01-14
Filing date: 2023-01-14
Publication date: 2024-07-18

Abstract

According to the present invention, a rotor core of a single-phase SRM has a magnet pole disposed among rotor poles. First to third magnet poles adjacent to one another in the axial direction have the N-pole, and fourth to sixth magnet poles adjacent to one another in the axial direction have the S-pole. The single-phase SRM has a single-phase mode and a three-phase mode. The single-phase mode generates single-phase reluctance torque, similar to conventional single-phase SRMs. The single-phase mode further generates magnet torque. In the three-phase mode, a magnet set composed of the first to third magnet poles is considered as a virtual magnet pole (N-pole), and another magnet set composed of the fourth to sixth magnet poles is considered as another virtual magnet pole (S-pole). Three-phase AC current is supplied to six kinds of phase windings sequentially wound around six stator poles. As a result, the single-phase SRM rotates as a three-phase permanent magnet synchronous motor in the three-phase mode.

Description

Switched reluctance motor device

The present invention relates to a switched reluctance motor device, and in particular to a single-phase switched reluctance motor device suitable for an aircraft motor. The switched reluctance motor device of the present invention includes a switched reluctance generator.

The torque-to-weight ratio of a motor is important in aircraft applications and the like. Switched reluctance motors (SRMs) have a lower torque-to-weight ratio (T/kg) than permanent magnet synchronous motors (PMSMs). To improve this problem of conventional SRMs, a hybrid SRM has been proposed, which is an SRM with an added permanent magnet. This hybrid SRM has a magnet pole located in the rotor slot between two circumferentially adjacent rotor poles. The rotor poles are salient poles made of soft magnetic material, and the magnet poles are salient poles made of permanent magnets.

Patent Document 1 proposes a three-phase hybrid SRM in which magnet poles are arranged in the rotor slots of a conventional three-phase SRM. A conventional three-phase SRM has a different number of stator poles than the rotor poles. As a result, the rotor slots of a conventional three-phase SRM have a wider circumferential width than the rotor poles. Therefore, the magnet poles are arranged in the circumferential center of the rotor slot. Two magnet poles adjacent to each other in the circumferential direction across the rotor pole have different polarities.

Patent document 2, filed by the present inventor, also proposes a three-phase hybrid SRM with magnet poles arranged in the rotor slots of a conventional three-phase SRM. The magnet poles are arranged biased toward one side of the rotor slot in the circumferential direction.

The single-phase SRM has been proposed as another type of SRM. It has a number of stator poles equal to the number of rotor poles. However, the disadvantages of the single-phase SRM are that it has high vibration and noise, and it is not easy to generate starting torque.

JP 2004-248730 A JP 2010-193700 A

In reality, conventional three-phase hybrid SRMs cannot compete with permanent magnet synchronous motors (PMSMs) except for special applications. However, the rare earth materials used in conventional three-phase PMSMs are potentially subject to an unstable supply environment.

To reduce the share of rare earth costs in motor costs, the maximum rotational speed of three-phase PMSMs is being increased. However, this increase in maximum rotational speed requires losses in the reduction gear mechanism and an increase in weight. In particular, it is desirable for aircraft motors to be coupled to propellers without a reduction gear mechanism.

One object of the present invention is to provide a switched reluctance motor device having an excellent torque/weight ratio.

In one aspect of the present invention, a single-phase SRM is employed. However, the rotor core of this single-phase SRM has magnet poles made of permanent magnets. The number of stator poles and the number of rotor poles are equal. Furthermore, the number of magnet poles is also equal to the number of rotor poles. Each magnet pole is arranged in a rotor slot, which is a recess between two circumferentially adjacent rotor poles. In other words, the rotor of this single-phase SRM has a structure in which rotor poles, which are soft magnetic salient poles, and magnet poles, which are permanent magnet poles, are arranged alternately in the circumferential direction.

This single-phase SRM has a single-phase mode and a three-phase mode. In this single-phase mode, which is the same as the operation of a conventional single-phase SRM, all stator poles are excited simultaneously during the period when the inductance of the phase winding increases. As a result, all stator poles attract all rotor poles.

Furthermore, in this single-phase mode, all stator poles generate magnet torque in addition to the reluctance torque. This magnet torque is formed by the stator poles magnetically repelling the magnet poles. The stator poles are excited with the same polarity as the closest magnet pole. This magnet pole is positioned in front of the stator pole in the circumferential direction. As a result, all stator poles generate magnet torque consisting of a magnetic repulsive force component in addition to the reluctance torque described above.

When the rotor of a single-phase SRM rotates, the phase windings wound on the stator poles have alternating periods of increasing inductance and decreasing inductance. In single-phase mode, a single-phase current is supplied to the phase winding during the periods of increasing inductance.

As a result, the single-phase mode of this single-phase SRM simultaneously generates both the reluctance torque and the repulsive force component of the magnet torque during the inductance increase period. This allows this single-phase SRM to have a higher torque/weight ratio and torque/current ratio than a conventional single-phase SRM. The stator poles are excited with alternating current to change magnetic polarity in response to the change in magnetic polarity of the nearest magnet pole.

This single-phase SRM makes it much easier to support the permanent magnets. This effect is explained further. In a single-phase SRM, the circumferential width of the rotor poles is essentially equal to the circumferential width of the rotor slots. Furthermore, the circumferential width of the magnet poles is equal to the circumferential width of the rotor slots. Therefore, the permanent magnets forming the magnet poles can be supported by two circumferentially adjacent rotor poles.

In one preferred embodiment, this single-phase SRM has a motor structure that can operate as a three-phase permanent magnet synchronous motor (three-phase PMSM). The number of stator poles, rotor poles, and magnet poles are each equal to an integer multiple of six. Three magnet poles arranged in sequence in the circumferential direction form an N-pole magnet set, and another three magnet poles arranged in sequence in the circumferential direction form an S-pole magnet set. The N-pole magnet set and the S-pole magnet set are arranged alternately in the circumferential direction.

Three adjacent magnet poles with a north pole can be considered as one virtual north pole, and three adjacent magnet poles with a south pole can be considered as one virtual south pole. Therefore, these virtual north poles and virtual south poles are arranged alternately in the circumferential direction.

In the end, when a three-phase AC current synchronized with the rotor rotation is supplied to this single-phase SRM, the single-phase SRM becomes a three-phase permanent magnet synchronous motor. This operating mode is called three-phase mode. Therefore, three-phase mode generates a stable starting torque.

In another preferred embodiment, six different phase windings are wound in a concentrated manner around six stator poles in sequence. According to the three-phase mode, six different phase currents, each having a phase separated by an electrical angle of 60 degrees from the others, are supplied separately to the six different phase windings. In this three-phase mode, the stator pole is excited with the same polarity as the magnet pole that is closest to it. This allows the permanent magnet three-phase synchronous motor to utilize at least the repulsive force component of the magnet torque.

In another preferred embodiment, the power converter driving this single-phase SRM consists of three H-bridges that generate three phase currents separated by an electrical angle of 120 degrees. The current directions of the three phase currents are switched in synchronization with the position of the rotating rotor pole. In this three-phase mode, the stator poles are excited in a direction that attracts the nearby magnet poles and repels the receding magnet poles by switching the current directions of the three phase currents. Each phase current can have various waveforms such as sine waves, square waves, and trapezoidal waves. This allows the three-phase mode to generate stable synchronous torque.

In another preferred embodiment, the three-phase mode is implemented to start the single-phase SRM. This allows the single-phase SRM to be reliably started. In a preferred embodiment, the three-phase mode is implemented during high-speed rotation. The stator current in the three-phase mode has lower frequency components than the stator current in the single-phase mode, so that iron loss during high-speed rotation can be reduced.

In another preferred embodiment, this single-phase SRM has an outer rotor structure. This effectively prevents the permanent magnet from becoming detached from the rotor core rotating at high speed.

In another preferred embodiment, the housing of a single-phase SRM with an inner rotor structure has a cylindrical portion to which the stator core is fixed. The outer peripheral surface of this cylindrical portion has a number of flanges that protrude radially outward. These flanges have a ring plate shape or a spiral coil shape. This makes it possible to improve both acoustic noise and heat dissipation. Conventional inner rotor type switched reluctance motors have the disadvantage that the cylindrical portion of the housing to which the stator core is fixed is a strong source of acoustic noise. According to this embodiment, the flanges reduce radial vibration of the cylindrical portion.

In another preferred embodiment, ferrite magnets are used as permanent magnets forming the magnet poles. To improve the demagnetization problem of the ferrite magnets, a DC current is supplied to the phase windings. Each stator pole of the single-phase SRM can overlap with each magnet pole in the circumferential direction. In other words, each stator pole and each magnet pole can have the same position in the circumferential direction. When the magnet pole has the same position as the stator pole, a DC current is supplied to the phase windings of the single-phase SRM to restore the saturation magnetic flux of the magnet poles. This restores the magnetization of the magnet poles again.

FIG. 1 is a block circuit diagram showing a switched reluctance motor (SRM) device of the present invention. FIG. 2 is a schematic development diagram for explaining the three-phase mode. FIG. 3 is a schematic development diagram for explaining the three-phase mode. FIG. 4 is a timing chart showing the inductance and the three-phase AC current supply period in the three-phase mode. FIG. 5 is a timing chart showing a polarity change pattern of the stator poles in the three-phase mode. FIG. 6 is a schematic development view for explaining the single-phase mode. FIG. 7 is a schematic development view for explaining the single-phase mode. FIG. 8 is a timing chart showing the inductance and the three-phase AC current supply period in the single-phase mode. FIG. 9 is a timing chart showing a polarity change pattern of the stator poles in the single-phase mode. FIG. 10 is a schematic development view for explaining the single-phase power generation mode. FIG. 11 is a schematic development view for explaining the single-phase power generation mode. FIG. 12 is a timing chart showing the inductance and the three-phase AC current supply period in the single-phase power generation mode. FIG. 13 is a timing chart showing a polarity change pattern of the stator poles in the single-phase power generation mode. FIG. 14 is a radial sectional view showing a schematic diagram of the switched reluctance motor of this embodiment. FIG. 15 is a plan view of the switched reluctance motor shown in FIG. FIG. 16 is a plan view showing another example of the switched reluctance motor shown in FIG. FIG. 17 is a partially enlarged cross-sectional view showing a modification of the rotor shown in FIG. FIG. 18 is a schematic axial cross-sectional view showing an outer rotor type switched reluctance motor. FIG. 19 is a flow chart showing the operation of remagnetizing a magnet pole made of a hard ferrite material.

A preferred embodiment of a switched reluctance motor (SRM) device of the present invention will be described with reference to the drawings. In the drawings, ’AX’ indicates the axial direction, ’RA’ indicates the radial direction, and ’PH’ indicates the circumferential direction.

Figure 1 is a block circuit diagram showing this SRM device. This SRM device has a hybrid SRM 1, a power converter 2, and a controller 4. The phase windings of the hybrid SRM 1, which is a single-phase SRM, consist of U-phase windings 71 and 74, V-phase windings 72 and 75, and W-phase windings 73 and 76.

The power converter 2 consists of a U-phase H-bridge 21, a V-phase H-bridge 22, and a W-phase H-bridge 23. Each of the three H-bridges 21-23 consists of two half-bridges called legs. The H-bridge 21 supplies a U-phase current IU to the U-phase windings 71 and 74. The H-bridge 22 supplies a V-phase current IV to the V-phase windings 72 and 75. The H-bridge 23 supplies a W-current IW to the W-phase windings 73 and 76.

The battery 3 supplies DC power to the three H-bridges. The power converter 2 is controlled by a controller 4. The controller 4 receives the rotor rotation angle and current value of the hybrid SRM 1 from sensors (not shown). The smoothing capacitor 5 is connected in parallel with the battery 3.

The controller 4 has a three-phase mode and a single-phase mode. In the three-phase mode, the hybrid SRM 1 is operated as a permanent magnet synchronous motor (PMSM). In the single-phase mode, the hybrid SRM 1 is operated as a single-phase switched reluctance motor (single-phase SRM). The three-phase mode is described with reference to Figures 2-5. The single-phase mode is described with reference to Figures 6-9. Furthermore, the single-phase power generation mode, which is a power generation mode implemented by the single-phase mode, is described with reference to Figures 10-13.

Figures 2-3, 6-7, and 10-11 are developments showing the change in the relative position of the stator core 11 and rotor core 12 in each mode. The stator core 11 and rotor core 12 are each made of laminated electromagnetic steel sheets. In these figures, the stator core 11 and rotor core 12, which face each other across an electromagnetic gap, are each deformed into a linearly developed shape. Therefore, the back yoke 110 of the stator core 11 and the back yoke 120 of the rotor core 12 are shown linearly in Figures 2-3, 6-7, and 10-11.

The relative positions of the stator core 11 and rotor core 12 in phase periods P1, P2, and P3 are shown in Figures 2, 6, and 10. The relative positions of the stator core 11 and rotor core 12 in phase periods P4, P5, and P6 are shown in Figures 3, 7, and 11. One cycle period of this hybrid SRM 1 consists of these six phase periods P1-P6. The rotor core 12 of this hybrid SRM 1 advances six pole pitches during one cycle period. In other words, the rotor core 12 advances one pole pitch in one phase period.

In Figures 2-3, 6-7, and 10-11, the stator core 11 has a stator pole set consisting of six stator poles 61-66. The stator poles 61-66 are soft magnetic salient poles that protrude toward the rotor core 12. The six stator poles 61-66 are arranged in sequence at equal intervals from one another. A phase winding 71 is wound around the stator pole 61, and a phase winding 72 is wound around the stator pole 62. A phase winding 73 is wound around the stator pole 63, and a phase winding 74 is wound around the stator pole 64. A phase winding 75 is wound around the stator pole 65, and a phase winding 76 is wound around the stator pole 66.

The winding direction of phase winding 71 is opposite to that of phase winding 74. Therefore, when the tip of stator pole 61 is a north pole, the tip of stator pole 64 is a south pole. The winding direction of phase winding 72 is opposite to that of phase winding 75. Therefore, when the tip of stator pole 62 is a north pole, the tip of stator pole 65 is a south pole. The winding direction of phase winding 73 is opposite to that of phase winding 76. Therefore, when the tip of stator pole 63 is a north pole, the tip of stator pole 66 is a south pole.

The rotor core 12 has rotor poles 91-96, which are soft magnetic salient poles that protrude toward the stator core 11. The rotor core 12 has rotor slots, which are gaps between two adjacent rotor poles. Magnet poles 81-86 made of permanent magnets are housed in the rotor slots. Magnet pole 81 is fixed between rotor poles 91 and 92, and magnet pole 82 is fixed between rotor poles 92 and 93. Magnet pole 83 is fixed between rotor poles 93 and 94, and magnet pole 84 is fixed between rotor poles 94 and 95. Magnet pole 85 is fixed between rotor poles 95 and 96, and magnet pole 86 is fixed between rotor poles 96 and 91. The hybrid SRM 1 has the numbers of stator poles, rotor poles, and magnet poles that are all equal and multiples of 6.

Next, the three-phase mode is described. The hybrid SRM 1 operates as a three-phase permanent magnet synchronous motor (three-phase PMSM). The power converter 2 supplies three phase currents IU, IV, and IW to the six phase windings 71-76. Supplying the phase currents IU, IV, and IW to the phase windings 74-76 wound in opposite directions is equivalent to supplying the opposite phase currents -IU, -IV, and -IW to the phase windings 74-76. In effect, the U-phase current IU is supplied to the phase winding 71, the V-phase current IV is supplied to the phase winding 75, and the W-phase current IW is supplied to the phase winding 73. The -U-phase current -IU, which has the opposite phase to the U-phase current IU, is supplied to the phase winding 74. The -V-phase current -IV, which has the opposite phase to the V-phase current IV, is supplied to the phase winding 72. The -W-phase current -IW, which has the opposite phase to the W-phase current IW, is supplied to the phase winding 76.

The three phase currents IU, IV, and IW are alternating currents with phases that differ from each other by an electrical angle of 120 degrees. As a result, phase magnetic fields that are 60 electrical degrees apart from each other are formed by the stator poles 61-66. Therefore, the phase currents IU, IV, and IW form a rotating magnetic field in the stator core 11 that rotates by 60 electrical degrees each.

Figure 2 shows the relative circumferential position of the rotor core 12 in three consecutive phase periods P1-P3. Figure 3 shows the relative circumferential position of the rotor core 12 in three consecutive phase periods P4-P6. In Figures 2 and 3, the relative circumferential position of the rotor core 12 indicates the position at a phase angle of 0 degrees. Each of these phase periods P1-P6 corresponds to a period in which the rotor core 12 moves circumferentially by one stator pole pitch. Each of the phase periods P1-P6 corresponds to an electrical angle of 360 degrees.

In phase periods P1-P6, an electrical angle of 0 degrees indicates that the magnet poles 81-86 are positioned to overlap the stator poles 61-66 in the circumferential direction. Therefore, at an electrical angle of 0 degrees, the rotor poles 91-96, which are soft magnetic poles, overlap the stator slots between the stator poles in the circumferential direction. Similarly, an electrical angle of 180 degrees indicates that the rotor poles 91-96 are positioned to overlap the stator poles 61-66 in the circumferential direction. Therefore, at an electrical angle of 180 degrees, the magnet poles 81-86 overlap the stator slots between the stator poles in the circumferential direction.

Phase windings 71 and 74 have an inductance LU, phase windings 75 and 72 have an inductance LV, and phase windings 73 and 76 have an inductance LW. Inductances LU, LV, and LW are at their minimum values at an electrical angle of 0 degrees and at their maximum values at an electrical angle of 180 degrees. For this reason, the period from an electrical angle of 0 degrees to an electrical angle of 180 degrees is called the inductance increase period, and the period from an electrical angle of 180 degrees to an electrical angle of 0 degrees is called the inductance decrease period.

The stator poles 61-66, rotor poles 91-96, and magnet poles 81-86 each have approximately the same circumferential width. Each magnet pole 81-86, made of a ferrite magnet, is fixed in a space called a rotor slot. The rotor slots exist between the rotor poles 91-96. The tip surfaces of the rotor poles 91-96, which face the stator poles 61-66 across an electromagnetic gap, have a wider circumferential width than the bottoms of the rotor poles 91-96.

In other words, the rotor poles 91-96 are formed in a wedge shape that narrows the opening of the rotor slot. Furthermore, each permanent magnet that makes up the magnet poles 81-86 is fired to have a shape that matches these rotor slots. This allows the rotor poles 91-96 to strongly support the magnet poles 81-86.

As shown in Figures 2 and 3, the surfaces of magnet poles 81-83 facing stator poles 61-66 have a north pole. The surfaces of magnet poles 84-86 facing stator poles 61-66 have a south pole. In other words, magnet poles 81-83 adjacent to each other in the circumferential direction have the same polarity, and magnet poles 84-86 adjacent to each other in the circumferential direction have the same polarity.

In the three-phase mode, the three magnet poles 81-83 with north poles can be represented diagrammatically by a virtual north pole placed at the position of magnet pole 82. Similarly, the three magnet poles 84-86 with south poles can be represented diagrammatically by a virtual south pole placed at the position of magnet pole 85.

Therefore, when three-phase AC currents IU, IV, and IW are supplied to the phase windings 71-76, one set of stator poles 61-66 forms a rotating magnetic field with one N pole and one S pole. When the N pole of this rotating magnetic field is located behind the virtual N pole and in front of the virtual S pole, the N pole of the rotating magnetic field advances the virtual N pole due to a repulsive force and advances the virtual S pole due to an attractive force. Similarly, when the S pole of this rotating magnetic field is located behind the virtual S pole and in front of the virtual N pole, the S pole of the rotating magnetic field advances the virtual S pole due to a repulsive force and advances the virtual N pole due to an attractive force.

In conclusion, in this three-phase mode, the three-phase AC current is controlled so that the rotational speed and phase of the rotating magnetic field are synchronized with the rotational speed and phase of the rotor core 12. This causes the hybrid SRM 1 to rotate as a three-phase PMSM.

Figure 4 is a timing diagram showing the three phase currents (IU, IV, and IW) supplied to phase windings 71-76, and the inductances (LU, LV, and LW) of phase windings 71-76. U-phase current IU is supplied to phase windings 71 and 74, V-phase current IV is supplied to phase windings 75 and 72, and W-phase current IW is supplied to phase windings 73 and 76. Stator poles 61 and 64 have opposite polarities. Stator poles 62 and 65 have opposite polarities. Stator poles 63 and 66 have opposite polarities.

Phase windings 71 and 74 have an inductance LU, phase windings 72 and 75 have an inductance LV, and phase windings 73 and 76 have an inductance LW. Phase windings 71 and 74 may be connected in series or in parallel. Phase windings 72 and 75 may be connected in series or in parallel. Phase windings 73 and 76 may be connected in series or in parallel.

Three consecutive phase periods P1-P3 are shown in FIG. 2. Three consecutive phase periods P4-P6 are shown in FIG. 3. The passage of six phase periods P1-P6 means that the rotor core 12 rotates by six pole pitches.

According to this three-phase mode, one cycle period of the three-phase AC current (IU, IV, IW) consists of phase periods P1-P6. The U-phase AC current IU shifts from a negative half-wave period to a positive half-wave period at time t1, and from a positive half-wave period to a negative half-wave period at time t4. The V-phase AC current IV shifts from a positive half-wave period to a negative half-wave period at time t2, and from a negative half-wave period to a positive half-wave period at time t5. The W-phase AC current IW shifts from a negative half-wave period to a positive half-wave period at time t3, and from a positive half-wave period to a negative half-wave period at time t6.

The waveform of the three-phase AC current (IU, IV, IW) can be selected from sine waves, trapezoidal waves, square waves, etc. as necessary. In FIG. 4, the three-phase AC current (IU, IV, IW) has a square wave waveform. FIG. 5 shows the polarity change of the stator poles 61-66 in each phase period P1-P6. This polarity refers to the polarity of the tip surfaces of the stator poles 61-66 facing the electromagnetic gap.

According to this three-phase mode, three consecutive magnet poles of the same polarity in the circumferential direction are regarded as one virtual magnetic pole. This virtual magnetic pole is regarded as existing at the position of the middle magnet pole among the three magnet poles of the same polarity. As a result, the six magnet poles 81-86 form a pair of north and south virtual magnetic poles. The three-phase currents (IU, IV, and IW) sequentially change the polarity of the stator poles 61-66.

This creates a rotating magnetic field. The north and south poles of this rotating magnetic field exert magnetic attraction and repulsion on the virtual magnetic poles formed by the magnet poles 81-86. Ultimately, the rotor core 12 becomes the magnet rotor of a three-phase PMSM.

Next, the single-phase mode will be described with reference to Figures 6 to 9. The hybrid SRM 1 operates as a single-phase SRM. According to this single-phase mode, during the inductance increase period, which is the period from electrical angle 0 degrees to electrical angle 180 degrees, a U-phase current IU is supplied to the phase windings 71 and 74, a V-phase current IV is supplied to the phase windings 75 and 72, and a W-phase current IW is supplied to the phase windings 73 and 76. Figures 6 and 7 show the circumferential positions of the rotor poles 91-96 during phase periods P1-P6. In Figures 6 and 7, the rotor poles 91-96 are at angular positions corresponding to an electrical angle of 90 degrees.

The stator poles 61-66, excited by the three-phase currents IU, IV, and IW, excite the rotor poles 91-96. During the inductance increase period, the rotor poles 91-96 are located to the left of the nearest stator pole in the circumferential direction. Therefore, the rotor poles 91-96 are attracted to the right in the circumferential direction.

Furthermore, as shown in Figures 6 and 7, when three-phase currents IU, IV, and IW are supplied to the six-phase windings 71-76, the stator poles 61-66 have the same polarity as the closest magnet pole among the magnet poles 81-86. In other words, the stator poles 61-66 are each excited and have the same polarity as the magnet pole on the circumferential right side. As a result, the excited stator poles 61-66 during the inductance increase period of 0-180 electrical degrees repel the magnet poles 81-86 to the circumferential right side.

In this single-phase mode, by switching the current direction of the phase currents IU, IV, and IW, the stator poles 61-66 always have the same polarity as the magnet poles 81-86 adjacent to them on the circumferential front side. In Figures 6 and 7, the double lines shown indicate the magnetic repulsive forces applied to the magnet poles, and the single lines shown indicate the magnetic attractive forces applied to the rotor poles.

In conclusion, when single-phase AC current is supplied to the three-phase windings 71-76, the stator poles 61-66 apply a reluctance torque to all of the rotor poles 91-96, and further apply a repulsive force component of the magnet torque to all of the magnet poles 81-86. As a result, the hybrid SRM 1 driven in this single-phase mode can have a high torque/weight ratio.

Figure 8 is a timing chart showing the three-phase currents (IU, IV, and IW) supplied to the phase windings 71-76 and the inductances (LU, LV, and LW) of the phase windings 71-76. In this single-phase mode, the three-phase currents (IU, IV, and IW) become three-phase AC currents, as in the three-phase mode. In Figure 8, the phase windings 71 and 74 have an inductance LU, the phase windings 72 and 75 have an inductance LV, and the phase windings 73 and 76 have an inductance LW. The six phase periods P1-P6 correspond to one cycle period of the three-phase AC current. Figure 6 shows the phase period P1-P3, and Figure 7 shows the phase period P4-P6. When the six phase periods have elapsed, the rotor core 12 rotates by six pole pitches.

In other words, this single-phase mode simultaneously supplies three-phase AC currents IU, IV, and IW to the phase windings 71-76. This causes all stator poles 61-66 to attract all rotor poles 91-96 and repel all magnet poles 81-86. This single-phase mode achieves a high torque/weight ratio. Figure 9 shows the change in polarity of the stator poles 61-66 excited by the three phase currents (IU, IV, and IW).

Next, the single-phase generating mode will be described with reference to Figs. 10-13. This single-phase generating mode is an operating mode in which the hybrid SRM 1 operates as a single-phase switched reluctance generator (SRG). As is well known, a motor can operate as a generator. This single-phase generating mode is essentially the same as the single-phase mode shown in Figs. 6-9. Fig. 10 is essentially the same as Fig. 6, Fig. 11 is essentially the same as Fig. 7, Fig. 12 is essentially the same as Fig. 8, and Fig. 13 is essentially the same as Fig. 9.

However, in Figures 10 and 11, each of the stator poles 61-66 is positioned in front of the nearest magnet pole and behind the nearest rotor pole. Figures 10 and 11 show positions at an electrical angle of 270 degrees in phase periods P1-P6. Each excited stator pole 61-66 has the same polarity as the nearest magnet pole. Furthermore, each excited stator pole 61-66 magnetizes the nearest rotor pole with the opposite polarity.

As shown in FIG. 13, three phase currents IU, IV, and IW flow through the phase windings 71-76 during the inductance reduction period having an angular range of 180 electrical degrees to 0 electrical degrees. In this single-phase power generation mode, the phase currents IU, IV, and IW are supplied to the phase windings 71-76 at the beginning of the current conduction period. Thereafter, the supply of these phase currents is stopped, but the phase windings 71-76 continue to pass the generated current to the power converter 2.

As can be seen from Figures 12 and 13, in this single-phase power generation mode, the three phase currents IU, IV, and IW flowing through the phase windings 71-76 are each AC currents. This is because the polarity of the stator poles 61-66 is changed. The single-phase power generation mode of this embodiment is essentially the same as the power generation mode of a conventional single-phase SRG. However, according to this embodiment, a high generated voltage can be obtained by using the magnet poles arranged in the rotor slots.

An inner rotor type hybrid SRM 1 will be described with reference to FIG. 14. FIG. 14 is a radial cross-sectional view of this hybrid SRM 1. The stator core 11 has two stator pole sets. Each stator pole set consists of stator poles 61-66. Therefore, the rotor core 12 also has two rotor pole sets, each of which consists of rotor poles 91-96. The rotor core 12 has two magnet pole sets. Each magnet pole set consists of magnet poles 81-86.

In this inner rotor type hybrid SRM 1, the outer peripheral surface of the stator core 11 is fixed to the inner peripheral surface of the cylindrical portion 101 of the housing 100. A ring-shaped flange portion 200 protrudes radially outward from the outer peripheral surface of the cylindrical portion 101. The flange portion 200 is cast integrally with the housing 100 using an aluminum alloy. This flange portion 200 reduces radial vibration of the cylindrical portion 101. Furthermore, the flange portion 200 suppresses an increase in the weight of the housing 100.

Figure 15 is a plan view showing the details of the flange portion 200. Nine flange portions 200 protrude radially outward from the outer circumferential surface of the cylindrical portion 101 of the housing 100. Each of the flange portions 200 is formed around the entire circumference of the cylindrical portion 101. An air passage of a predetermined width is formed between each of the flange portions 200. The air flow for cooling the flange portions 200 flows perpendicular to the axial direction of the rotating shaft 13. Furthermore, the cylindrical portion 101 is suppressed from vibrating radially due to the radial vibration of the stator core 11. In the single-phase mode, all of the stator poles 61-66 vibrate radially at the same time. The flange portions 200 achieve the effects of vibration suppression, weight reduction, and improved heat dissipation. In a preferred embodiment, in order to achieve these effects, the average height of the flange portions 200 is formed to be greater than the average thickness of the cylindrical portion 101. Furthermore, it is preferable that at least three or more flanges 200 are formed on the cylindrical portion 101.

Figure 16 is a plan view showing a modified example of the flange 200. An aircraft propeller 400 is fixed to the rotating shaft 13 of a single-phase SRM 1 having an inner rotor structure. The housing 100 has a cylindrical portion 101. A spiral coil flange 300 is fixed to the outer circumferential surface of the cylindrical portion 101. Preferably, the cylindrical portion 101 and the flange 300 are cast together. When the propeller 400 rotates, the air flow 401 formed by the propeller 400 flows into the spiral groove 301 between the spiral coil flanges 300. The flange 300 is well cooled by the air flow 401. Furthermore, the flange 300 is formed around the entire circumference of the cylindrical portion 101. Therefore, radial vibration of the cylindrical portion 101 is suppressed.

Figure 17 is a radial cross-sectional view partially showing a modified example of the rotor core 12. The magnet poles 81-86 are formed of ferrite magnets. The magnet poles 81-86 are housed separately in rotor slots 500, which are grooves formed between the rotor poles 91-96. The side of the rotor poles 91-96 facing each rotor slot 500 has protrusions 501 and 502 that protrude toward the rotor slot 500. The protrusions 501 and 502 are located in the radial middle of the rotor poles 91-96.

As a result, the circumferential width of the rotor slot 500 is narrowed by the protrusions 501 and 502. This prevents the magnet poles 81-86 from detaching radially outward from the rotor core 12 due to centrifugal force. In FIG. 17, the rotor core 12 is fixed to the rotating shaft 13 via a cylinder member 120 made of an aluminum alloy. This reduces the weight of the rotor.

Figure 18 is an axial cross-sectional view showing an outer rotor type hybrid SRM 1. The hybrid SRM 1 has a stator core 11 fixed to a stationary shaft 130 that protrudes upward from a fixed base 14. A phase winding 7 is wound around the stator core 11. A rotating rotor core 12 is disposed radially outside the stator core 11 with an electromagnetic gap between them.

The rotor core 12 is sandwiched vertically between rotor housings 15 and 16, which form the base of the propeller. The rotor housings 15 and 16 are fastened together with bolts (not shown) to form a single unit. The rotor housings 15 and 16 are rotatably supported by a stationary shaft 130 through bearings 18 and 19. The outer periphery (not shown) of the rotor housings 15 and 16 has a predetermined number of rotor blades. This hybrid SRM 1, which employs an outer rotor structure, has the advantage of being able to effectively prevent the permanent magnets from coming off the rotor core 12.

Figure 19 is a flowchart showing the remagnetization operation of the magnet poles 81-86 of the rotor core 12. First, the necessity of this remagnetization will be explained. The case where the residual magnetic flux density of the ferrite magnet is irreversibly reduced by the magnetic field of the stator poles 61-66 is known as the demagnetization problem of the ferrite magnet. This problem is solved by remagnetizing the magnet poles 81-86.

In the hybrid SRM1, which is essentially a single-phase switched reluctance motor, the circumferential positions of the stator poles 61-66 have a structure that allows them to be aligned with the circumferential positions of the magnet poles 81-86, for example as shown in FIG. 14. Therefore, when the magnet poles 81-86 are stationary at the same circumferential positions as the stator poles 61-66, the magnet poles 81-86 can be remagnetized by passing a remagnetization current through the stator poles 61-66.

When the hybrid SRM 1 is stopped, the magnet poles 81-86 generally stop at the same circumferential position as the stator poles 61-66 due to permanent magnetic force. The polarity of the magnet poles 81-86 facing the stator poles 61-66 is determined from the detected rotation angle of the rotor core 12. The direction of the DC current supplied to the phase windings 71-76 is then determined according to the polarity of the magnet poles 81-86.

For example, a direct current supplied to a phase winding wound around a stator pole facing magnet pole 81, which has a north pole on its surface, has a direction that magnetizes the end face of this stator pole facing magnet pole 81 into a south pole. This allows magnet poles 81-86 to be easily remagnetized.

The remagnetization subroutine shown in FIG. 19 is started after it is confirmed that the motor is stationary. First, based on the detected rotational position of the rotor core 12, it is determined whether the magnet poles 81-86 are stopped at the circumferential position of the stator poles 61-66 (S100). Next, if the magnet poles 81-86 are not stopped at the same circumferential position as the stator poles 61-66, the three-phase mode is implemented to rotate the rotor core 12 slightly (S102). Next, the alignment work is again carried out, consisting of determining the alignment state and implementing the three-phase mode.

When it is determined in step S100 that the magnet poles 81-86 are stopped in alignment with the stator poles 61-66, a DC current is supplied to the phase windings 71-76 for a predetermined period of time or more (S104). As a result, the residual magnetic field of the magnet poles 81-86 is strengthened, and the demagnetization problem of the ferrite magnets is solved.

The main advantages of the hybrid SRM 1 of this embodiment are summarized below. First, the first advantage of this hybrid SRM 1, which can essentially operate as a single-phase switched reluctance motor, is that the number of poles of the motor can be easily increased. This advantage is particularly important in aircraft motors.

For example, consider the simple case of an aircraft propeller accelerating air backwards. It is assumed that the inlet velocity of the airflow entering the propeller is zero, and that the exit velocity of the airflow blowing backwards from the propeller is V. The mass of the airflow passing the propeller per unit time is assumed to be m.

The force 'F' that the propeller exerts on the airflow is equal to 'mV'. Therefore, the propeller receives a thrust (-F) from the airflow. Furthermore, the kinetic energy 'E' that the propeller exerts on the airflow is equal to '0.5mVV'. Therefore, the thrust per unit of energy consumed '-F/E' is '2/V'. This means that the lower the speed 'V', the more efficiently the thrust can be obtained. In short, it can be understood that a large propeller rotating at a slow speed generates thrust more efficiently than a small propeller rotating at a high speed.

However, propellers are notorious for having a problem with wingtip stall. Therefore, the propeller's rotation speed is strictly limited. Conventional propellers on small aircraft have a rotation speed of about 25 rps.

A motor can increase its output per weight by increasing its rotational speed. A reduction gear mechanism placed between the motor and the propeller increases the torque applied to the propeller. However, in aircraft applications, the weight of the motor should be reduced as much as possible, and the weight increase due to the reduction gear mechanism is a serious problem. Furthermore, loss in the reduction gear mechanism is also a serious problem.

In the end, it is understood that a low-speed, high-torque motor is the best choice for an aircraft motor. It is well known that the torque of a motor can be increased by increasing the number of motor poles. However, the motor weight increases significantly with the increase in the number of poles in a conventional motor such as a three-phase PMSM.

Increasing the number of motor poles requires the addition of a large number of stator poles. For example, a 24-pole three-phase synchronous motor requires 72 stator poles. This problem is solved by adopting a single-phase switched reluctance motor. For example, a single-phase SRM with 12 stator poles has a number of poles that is substantially equal to a three-phase synchronous motor (PMSM) with 72 stator poles. Ultimately, it is understood that a single-phase SRM is suitable as a direct-drive type aircraft motor for propellers.

The hybrid SRM 1 of this embodiment can be used in a variety of mobile devices other than aircraft, wind power generators, and other applications. When quiet operation is required, it is also possible to use a three-phase mode instead of a single-phase mode. Furthermore, it is also preferable to use a three-phase mode in the high-speed range where iron loss increases. In the three-phase mode, it is also preferable to use a three-phase AC current with a sinusoidal waveform in order to reduce iron loss and noise.

Claims

A switched reluctance motor device comprising: a single-phase switched reluctance motor including a soft magnetic stator core having stator poles, a soft magnetic rotor core having rotor poles, and a phase winding wound around the stator poles; a power converter that applies a phase voltage to the phase winding; and a controller that controls the power converter,
The rotor core further includes magnet poles each formed of a permanent magnet fixed to a rotor slot disposed between the rotor poles,
The number of the rotor poles and the number of the magnet poles are equal to the number of the stator poles,
13. A switched reluctance motor device, wherein the phase voltages are essentially composed of AC voltages.
The switched reluctance motor device according to claim 1, wherein the power converter is composed of three H-bridges, the three H-bridges apply the three phase voltages to the phase windings, and the phases of the three phase voltages are spaced apart from each other by an electrical angle of 120 degrees.
The switched reluctance motor device of claim 1, wherein the controller has a single-phase mode in which both a single-phase reluctance torque value and a single-phase magnet torque value are generated by simultaneously exciting all of the stator poles.
The single-phase mode gives the stator poles the same polarity as the nearest magnet poles,
4. The switched reluctance motor device according to claim 3, wherein the nearest magnet pole is located forward of the stator pole.
The switched reluctance motor device of claim 1, wherein the controller has a single-phase power generation mode in which both a negative single-phase reluctance torque value and a negative single-phase magnet torque value are generated by simultaneously exciting all of the stator poles.
The single-phase generating mode provides the stator pole with the same polarity as the nearest magnet pole;
6. The switched reluctance motor device according to claim 5, wherein the nearest magnet pole is located rearward of the stator pole.
The controller has a three-phase mode,
2. The switched reluctance motor apparatus according to claim 1, wherein the power converter operates the single-phase switched reluctance motor as a three-phase permanent magnet synchronous motor in the three-phase mode by applying the three phase voltages to the phase windings.
the number of the stator poles, the number of the rotor poles, and the number of the magnet poles are each equal to an integer multiple of 6;
The six consecutive magnet poles are divided into a first group and a second group,
The first group is made up of three consecutive magnet poles,
the second group is made up of three adjacent magnet poles,
8. The switched reluctance motor arrangement of claim 7, wherein said magnet poles of said first group have an opposite polarity to said magnet poles of said second group.
The switched reluctance motor device of claim 7, wherein the controller starts the single-phase switched reluctance motor in the three-phase mode.
The switched reluctance motor device according to claim 1, wherein each of the magnet poles is supported on the side surfaces of two adjacent rotor poles.
The switched reluctance motor device of claim 1, wherein the single-phase switched reluctance motor has an outer rotor structure.
The single-phase switched reluctance motor has an inner rotor structure,
The stator core is fixed to an inner circumferential surface of a cylindrical portion of a housing,
the housing has a number of annular plate-shaped flanges protruding radially outward from an outer circumferential surface of the cylindrical portion,
The switched reluctance motor device according to claim 1 , wherein an average height of the flange portion exceeds an average thickness of the cylindrical portion.
The single-phase switched reluctance motor has an inner rotor structure,
The stator core is fixed to an inner circumferential surface of a cylindrical portion of a housing,
2. The switched reluctance motor device according to claim 1, wherein the housing has a flange portion in the form of a spiral coil protruding radially outward from an outer circumferential surface of the cylindrical portion.
the controller has a demagnetization compensation mode for compensating for demagnetization of the magnet poles;
2. The switched reluctance motor device according to claim 1, wherein the demagnetization compensation mode remagnetizes the magnet poles by supplying a direct current to the phase windings during a period in which the magnet poles and the stator poles overlap in the circumferential direction.
The switched reluctance motor device according to claim 1, wherein the single-phase switched reluctance motor has 12 or more stator poles and is directly connected to a rotating device as a load.
The switched reluctance motor device according to claim 15, wherein the rotating device is an aircraft propeller.
The switched reluctance motor device according to claim 15, wherein the rotating device is a wind turbine.