Synchronous motor and pump system

Abstract

To make self-starting possible and enable highly efficient operation at synchronous speed.SOLUTION: A synchronous motor according to an embodiment has: a cylindrical rotor core with a rotating shaft in the center and a plurality of slots with radially long cross sections arranged in the circumferential direction on the outer periphery; a squirrel-cage conductor including a plurality of conductor bars provided in each slot of the rotor core and end rings connecting the conductor bars at both axial ends of the rotor core; and permanent magnets that are installed on the inner layer side of the rotor core slots and constitute two rotor magnetic poles. The permanent magnets are installed symmetrically with respect to the center line extending in the radial direction when viewed in the axial direction in a semicircular part that constitutes one pole of the rotor core, and has an outer end that is continuous with or close to the inner peripheral end of one of the slots. Two permanent magnets are arranged in two inner layer slits whose inner ends extend to the centerline portion, and the opening angle α formed by the two slots in which each inner layer slit is continuous or close to is 100° or more.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Embodiments of the present invention relate to a synchronous motor capable of self-starting and a pump device incorporating the synchronous motor.

Background Art

[0002] As a motor that is integrally incorporated into a pump device, for example, a motor directly coupled to a motor, a synchronous reluctance motor is known. Generally, in a synchronous reluctance motor, an inverter is required for starting, which causes a problem of high cost. Therefore, conventionally, as shown in, for example, Patent Document 1, a self-starting permanent magnet type synchronous motor configured to include both a cage conductor and a permanent magnet in a rotor and driven by a commercial power supply has been considered.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The above-described permanent magnet type synchronous motor is configured by arranging a rotor on the inner peripheral side of a stator around which a three-layer winding is wound. The rotor is provided with conductor bars in a plurality of slots provided on the outer peripheral portion of the rotor core, short-circuited with a short-circuit ring to provide a cage conductor for starting, and holes for embedding permanent magnets are provided inside the conductor bars, and permanent magnets are embedded in those holes to form two-pole rotor magnetic poles. In this case, the holes for embedding the permanent magnets are four in total and form a square frame shape, and the ends of those holes are provided in proximity to short-circuit prevention slits formed long in the radial direction at two locations at both ends in the diameter direction of the slots. In each magnetic pole, two permanent magnets are arranged in an L shape when viewed in the axial direction in two holes for embedding permanent magnets.

[0005] However, according to the inventors' research, simply combining a squirrel-cage conductor and permanent magnets in the above-described synchronous motor is insufficient to achieve high efficiency. From the standpoint of reducing iron loss to obtain high efficiency and further reducing torque ripple, further exploration of the optimal structure for the arrangement of permanent magnets is required. Therefore, the present invention provides a synchronous motor that is self-starting and can achieve high efficiency, and a pump device using the synchronous motor. [Means for solving the problem]

[0006] The synchronous motor of the embodiment is capable of self-starting and comprises a cylindrical rotor core having a rotating shaft at its center and a plurality of slots with a radially elongated cross-section arranged circumferentially on its outer circumference, a cage-type conductor including a plurality of conductor bars provided in each slot of the rotor core and end rings connecting these conductor bars at both axial ends of the rotor core, and permanent magnets provided on the inner layer side of the rotor core beyond the slots and constituting two rotor magnetic poles, wherein the permanent magnets are provided symmetrically with respect to a radially extending center line when viewed in the axial direction in the semicircular portion constituting one pole of the rotor core, and two permanent magnets are arranged in two inner layer slits in which the outer ends are continuous with or close to one of the inner circumferential ends of the slots and the inner ends extend to the center line portion. At the outer end of the inner layer slit, it is formed to be connected to the inner circumferential end of the continuous slot, or separated from the inner circumferential end of the adjacent slot via a bridge, and the continuous or adjacent The opening angle α between the two slots is specified to be 100° or more. [Brief explanation of the drawing]

[0007] [Figure 1] This diagram shows the first embodiment, schematically illustrating the internal configuration of a synchronous motor within a 180-degree angle (semicircular area). [Figure 2] A schematic diagram showing the appearance of the pump device. [Figure 3] Perspective view showing the rotor's appearance [Figure 4]This figure shows the results of investigating the relationship between the opening angle α and amplitude, for the RMS value of the fundamental wave, the RMS value of the third harmonic, and the RMS values ​​of all other waves. [Figure 5] A diagram showing the configurations of the rotor core models for Examples 1 and 2 and Comparative Example 1 side by side. [Figure 6] A diagram showing the configuration of the rotor core according to the second embodiment. [Figure 7] A diagram showing the configuration of the rotor core according to the third embodiment. [Figure 8] Enlarged view of one slot section [Figure 9] A diagram showing the configuration of the rotor core according to the fourth embodiment. [Figure 10] Enlarged view of the bridge section [Modes for carrying out the invention]

[0008] (1) First Embodiment The first embodiment will be described below with reference to Figures 1 to 5. First, Figure 2 schematically shows the configuration of the pump device 1 according to this embodiment. This pump device 1 comprises a pump body 2, which is for example a hydraulic pump, and a two-pole synchronous motor 10 according to this embodiment, which serves as the drive source for the pump body 2. In this case, the synchronous motor 10 is integrally coupled to the pump body 2, and the rotating shaft (not shown) of the synchronous motor 10 is configured to directly drive the pump body 2.

[0009] Figure 1 shows the configuration of one pole, or a semicircular section at an angle of 180 degrees, as viewed in the axial direction of the synchronous motor 10. As shown in Figure 1, the synchronous motor 10 according to this embodiment is constructed by mounting a stator 12 on the inner circumferential surface of a cylindrical frame 11 (see Figure 2), and arranging a rotor 13 with a small air gap on the inner circumference of the stator 12. The stator 12 is constructed by mounting windings (not shown) on a stator core 14 having a plurality of teeth 14a, for example, 24 teeth, that protrude toward the inner circumference.

[0010] As shown in Figure 3, the rotor 13 includes a cylindrical rotor core 15 having, for example, two magnetic salient poles. A rotating shaft (not shown) is fixed through the center of the rotor core 15, and this rotating shaft is rotatably supported by brackets at both ends of the frame 11. The rotor core 15 is constructed by stacking a number of electromagnetic steel sheets in the axial direction and has a central hole 15a in the center where the rotating shaft is positioned.

[0011] As shown in Figure 1, the outer circumference of the rotor core 15 is provided with multiple slots 16, for example, a total of 28 slots, arranged in the circumferential direction for forming conductor bars. The slots 16 are formed in a so-called teardrop shape, for example, with a cross-section that is longer in the radial direction and bulges more towards the outer circumference. In this case, slots of the same shape and size are provided at equal intervals. Although not shown in detail, a conductor bar is provided in each slot 16, for example, made of aluminum die-cast, and end rings 20a are provided at both axial ends of the rotor core 15 to connect these conductor bars, thereby providing a well-known cage-type conductor 20.

[0012] In this embodiment, an inner layer slit 17 for inserting permanent magnets is provided in the rotor core 15 on the inner layer side of the slot 16, extending along the entire axial direction, and a permanent magnet 18 constituting the two rotor magnetic poles is provided within the inner layer slit 17. In Figure 1, etc., the permanent magnet 18 is shown with hatching for convenience. Specifically, in the semicircular portion constituting one pole of the rotor core 15 shown in Figure 1, two inner layer slits 17 are provided, when viewed in the axial direction, symmetrically on both sides with respect to the radially extending center line L, forming a V-shape in the figure. The inner ends of these two inner layer slits 17 are close to each other via a small bridge portion 19 at the center line L. The outer ends of the two inner layer slits 17 are continuous with one of the inner circumferential ends of the slot 16.

[0013] In this embodiment, the outer ends of the two inner-layer slits 17, 17 are continuous with the second slits 16, 16 from the bottom in the figure as shown in Example 1 of FIG. 5, or are continuous with the third slits 16, 16 from the bottom in the figure as shown in Example 2 of FIG. 5. Thus, the opening angle α formed by the two slits 16, 16 to which the inner-layer slit 17 is connected is 100° or more and 150° or less. Specifically, in Example 1, the opening angle α is 141°, and in Example 2, the opening angle α is 116°.

[0014] The permanent magnet 18 has a thin rectangular plate shape that is long in the axial direction. In the semi-circular portions shown in FIGS. 1 and 5, for example, in each inner-layer slit 17, the outer side (the upper side in the figure) is the N pole and the inner side (the lower side in the figure) is the S pole. Although not shown, in the remaining semi-circular portions in the lower half of the rotor core 15 in the figure, the two inner-layer slits 17 are provided symmetrically with respect to the upper and lower directions in FIG. 1, and in each, the permanent magnet 18 is provided such that the outer side is the S pole and the inner side is the N pole. In addition, partial cavities are provided on both end sides of the permanent magnet 18 within the inner-layer slit 17.

[0015] The synchronous motor 10 of this embodiment configured as described above has been confirmed to be capable of self-starting by a commercial power supply and of operating with high efficiency at the synchronous speed by combining the cage-shaped conductor 20 and the permanent magnet 18 on the rotor 13. That is, the rotor core 15 has the function as an induction motor by including the cage-shaped conductor 20, that is, the characteristic of being able to be rotationally driven at the synchronous speed corresponding to the power supply frequency using a commercial power supply. At the same time, due to the magnet torque by providing the permanent magnet 18, self-starting is possible and driving with higher efficiency than an induction motor is possible. In particular, it is suitable for the pump device 1 with a small moment of inertia.

[0016] Now, the inventor of the present invention has conducted various tests and studies regarding the arrangement of the permanent magnets 18, that is, the inner layer slits 17, when a permanent magnet 18 is provided in addition to the cage-shaped conductor 20 in the rotor core 15 of the synchronous motor 10. Here, in the semi-circular portion of the rotor core 15, as described above, two inner layer slits 17 are symmetrically provided so as to form a U-shape when viewed in the axial direction, and a configuration in which the permanent magnets 18 are arranged in these respective inner layer slits 17 is taken as the basic configuration. Then, regarding at what specific angles the permanent magnets 18 are arranged with respect to the above basic configuration to have excellent torque characteristics and reduce losses, an investigation was made to verify the effectiveness of the synchronous motor 10 according to the present embodiment.

[0017] FIG. 4 shows the results of examining the relationship between the opening angle α formed by the two slots 16, 16 to which the inner layer slits 17, 17 are connected and the amplitude, for the effective value of the fundamental wave, the effective value of the third harmonic, and the effective value of all components other than the fundamental wave. From these results, the smaller the opening angle α, the larger the amplitude of the fundamental wave, and the third harmonic is minimized at α = 120°, and all harmonics are minimized at α = 139°. Further, the inventor analyzed the torque ripple and iron loss for three types of models in which the positions of the two slots 16, 16 to which the inner layer slits 17, 17 are connected were changed to make the opening angle α different.

[0018] FIG. 5 shows the three types of models used in the analysis. As described above, in Example 1, the inner layer slits 17, 17 are continuous with the second slots 16, 16 from the bottom in the figure, and the opening angle α is 141°. In Example 2, the inner layer slits 17, 17 are continuous with the third slots 16, 16 from the bottom in the figure, and the opening angle α is 116°. And in Comparative Example 1, the inner layer slits 17, 17 are continuous with the fourth slots 16, 16 from the bottom in the figure, and the opening angle α is 90°.

[0019] Analysis of the torque ripple and iron loss for the three models described above revealed that Example 1 had the smallest torque ripple, followed by Example 2 and then Comparative Example 1. Similarly, Example 1 also showed the best iron loss, followed by Example 2 and then Comparative Example 1. These results clearly demonstrate that setting the opening angle α to 100° or more reduces torque ripple and thus losses, resulting in high efficiency. Furthermore, it became clear that setting the opening angle α to 150° or less is desirable.

[0020] As described above, the synchronous motor 10 of this embodiment, in addition to the functions and characteristics of an induction motor due to the presence of a squirrel-cage conductor 20, enables self-starting due to the magnetic torque provided by the permanent magnet 18, and enables driving with higher efficiency compared to an induction motor. In this case, starting was possible with an inertia moment more than three times the required specification. Furthermore, by setting the opening angle α between the two consecutive slots 16 of each inner layer slit 17 to 100° or more and 150° or less, torque ripple and thus losses are reduced, resulting in high efficiency. The synchronous motor 10 with the above configuration is particularly suited to the starting load characteristics of the pump device 1, and by incorporating the synchronous motor 10 into the pump body 2, a pump device 1 with excellent starting characteristics and high efficiency can be provided at a low cost.

[0021] (2) Second embodiment Figure 6 shows a second embodiment, which differs from the first embodiment in the configuration of the rotor core 21. Specifically, the rotor core 21 in this embodiment is constructed by stacking a large number of electromagnetic steel sheets in the axial direction, and has a central hole 21a in the center where the rotation axis is positioned, and a plurality of slots 22, for example a total of 28, are arranged in the circumferential direction on the outer circumference to form conductor bars.

[0022] In this case, the multiple slots 22 on the outer circumference of the rotor core 21 are formed in a so-called teardrop shape with a long radial cross-section. In the semicircular portion shown in the figure when viewed in the axial direction, the width is relatively narrow on the side of the center line L, i.e., the upper side or central side in the figure, and wider at both ends. In addition, the spacing of the multiple slots 22 in the circumferential direction is also set to be relatively small on the side of the center line L and relatively large at both ends. As a result, the circumferential arrangement position of the slots 22 differs from that of the slots 16 in the first embodiment.

[0023] Furthermore, an inner layer slit 23 for inserting permanent magnets is provided on the inner layer side of the rotor core 21, beyond the slot 22, and a permanent magnet 18 constituting the two rotor magnetic poles is provided within this inner layer slit 23. The outer ends of the two inner layer slits 23, 23 are continuous with the second slots 22, 22 from the bottom in the figure, and the opening angle α formed by these two slots 22, 22 is set to be 100° or more and 150° or less. Specifically, the opening angle α is set to 123° depending on the arrangement position of the above-mentioned slots 22.

[0024] Thus, even when the opening angle α is set to 123°, efficiency equivalent to or better than that obtained when the opening angle α is set to 141° in the first embodiment can be obtained, and the same effect can be obtained. Furthermore, as a result of investigating the torque ripple, it was possible to reduce the torque ripple to a similar extent when the opening angle α was set to 123° and 141°. In this embodiment, by making improvements to the cross-sectional shape of the slot 22, i.e., the conductor bar, even in parts where the spacing between the slots 22 is large, the cross-sectional shape becomes thicker, ensuring that the magnetic flux flows easily and improving the torque ripple.

[0025] (3) Third Embodiment Figures 7 and 8 show a third embodiment. In this third embodiment as well, the configuration of the rotor core 31 differs from that of the first embodiment and the like. Specifically, as shown in Figure 7, the rotor core 31 in this embodiment is constructed by stacking a large number of electromagnetic steel sheets in the axial direction, and has a central hole 31a in the center where the rotation axis is positioned, and has a plurality of slots 32, for example a total of 28, arranged in the circumferential direction on the outer circumference for forming conductor bars.

[0026] In this case, as shown in Figure 8, the multiple slots 32 on the outer circumference of the rotor core 31 have a cross-sectional shape that is elongated radially in the semicircular portion shown in the figure when viewed in the axial direction, forming a so-called teardrop shape. The tip side, that is, the outer circumference end side, has a pointed, mountain-like shape, and the position of the vertex 32a located at the outer circumference end is set to be inclined in the circumferential direction with respect to the radial direction. Specifically, in the slots 32 on the right half of Figure 7, straddling the center line L, the vertex 32a is located at a position inclined by a small angle δ in the clockwise direction with respect to the radial direction R, as shown in Figure 8. In the slots 32 on the left half of Figure 7, straddling the center line L, the vertex 32a is located at a position inclined by a small angle δ in the counterclockwise direction with respect to the radial direction R.

[0027] Furthermore, as shown in Figure 7, an inner layer slit 33 for inserting a permanent magnet is provided on the inner layer side of the rotor core 31, beyond the slot 32, and a permanent magnet 18 is provided within this inner layer slit 33. The outer ends of the two inner layer slits 33, 33 are continuous with the second slots 32, 32 from the bottom in the figure, and the opening angle α between these two slots 32, 32 is in the range of 100° or more and 150° or less, for example, 141° or 123°.

[0028] According to this third embodiment, the same effects as the first and second embodiments can be obtained, such as enabling self-starting and high-efficiency operation at synchronous speed. Furthermore, it was confirmed that by arranging the position of the outer vertices 32a of the slots 32, 32 inclined, the flow of magnetic flux can be slightly altered, thereby further reducing torque ripple.

[0029] (4) Fourth embodiment, other embodiments Figures 9 and 10 show a fourth embodiment and illustrate the configuration of the rotor core 41. As shown in Figure 9, the rotor core 41 in this embodiment has a central hole 41a at its center, and multiple slots 42, for example a total of 28, are arranged in the circumferential direction on the outer circumference to form conductor bars. Similar to the slots 22 in the second embodiment described above, the cross-sectional shape of these slots 42 is such that, in the semicircular portion shown in the figure when viewed in the axial direction, the width is relatively narrow on the side of the center line L, and the width is wider at both ends.

[0030] In addition, the spacing between the multiple slots 42 in the circumferential direction is set to be relatively small on the centerline L side and relatively large on both ends. Moreover, in this embodiment, similar to the third embodiment described above, the multiple slots 42 have a pointed, mountain-like shape at their tip side, i.e., the outer peripheral end side, and the positions of their vertices 42a are set to be inclined in the circumferential direction with respect to the radial direction. In other words, in this embodiment, the slots 42 are set up in a form that combines the slots 22 of the second embodiment and the slots 32 of the third embodiment.

[0031] Furthermore, an inner layer slit 43 for inserting a permanent magnet is provided on the inner layer side of the rotor core 41, closer to the slot 42, and a permanent magnet 18 is placed within this inner layer slit 43. The outer ends of the two inner layer slits 43, 43 are close to the second slot 42, 42 from the bottom in the figure, and the opening angle α between these two slots 42, 42 is set to 123°. In this embodiment, as also shown in Figure 10, a bridge 44 is formed between the outer end of the inner layer slit 43 and the slot 42. The bridge 44 can be easily formed by changing the punching die of the electromagnetic steel sheet that constitutes the rotor core 41.

[0032] According to this fourth embodiment, similar to the first embodiment described above, it is possible to achieve self-starting and high-efficiency operation at synchronous speed. Generally, squirrel-cage conductors are formed by aluminum die-casting, but during formation, it is necessary to prevent the molten aluminum introduced into the slot 42 from entering the inner layer slit 43. In this embodiment, the intrusion of molten aluminum can be prevented with a simple configuration by providing a bridge 44 between the slot 42 and the inner layer slit 43 without providing any other means for preventing intrusion. It has been shown that there is almost no adverse effect on the characteristics due to the provision of the bridge 44.

[0033] In the above embodiments, thin plate-shaped permanent magnets 18 are arranged in the inner layer slits of the rotor core, but permanent magnets formed in a gentle arc shape may also be arranged in the arc-shaped inner layer slits. Regarding the thickness of the permanent magnets, relatively thick permanent magnets can be used, taking demagnetization into consideration. Furthermore, the number of slots in the rotor core can, of course, be changed as appropriate. In addition, synchronous motors can be applied to various pump devices, not just hydraulic pumps, and can be used in applications other than pump devices.

[0034] Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of symbols]

[0035] In the drawing, 1 is the pump device, 2 is the pump body, 10 is the synchronous motor, 13 is the rotor, 15, 21, 31, and 41 are the rotor cores, 16, 22, 32, and 42 are the slots, 17, 23, 33, and 43 are the inner layer slits, 18 is the permanent magnet, 20 is the cage conductor, 32a and 42a are the vertices, 44 is the bridge, α is the opening angle, and L is the centerline.

Claims

1. A synchronous motor that enables self-starting, A cylindrical rotor core has a rotating shaft at its center and multiple slots with elongated cross-sections arranged circumferentially on its outer circumference, A cage-type conductor including a plurality of conductor bars provided in each slot of the rotor core and end rings connecting these conductor bars at both axial ends of the rotor core, The rotor core is provided with permanent magnets that form two rotor magnetic poles and are located on the inner layer side of the slots, The permanent magnets are arranged in a semicircular portion that constitutes one pole of the rotor core, symmetrically with respect to a radially extending centerline when viewed in the axial direction, with two magnets disposed within two inner layer slits, each having an outer end continuous with or close to one of the inner circumferential ends of the slots, and an inner end extending to the centerline portion. A synchronous motor in which the outer end of the inner layer slit is formed to be connected to the inner circumferential end of the continuous slot, or separated from the inner circumferential end of the adjacent slot via a bridge, and the opening angle α between the continuous or adjacent slots is 100° or more.

2. The synchronous motor according to claim 1, wherein the opening angle α between two slots that are continuous or adjacent to each other in the inner layer slit is 150° or less.

3. The synchronous motor according to claim 1, wherein the plurality of slots on the outer circumference of the rotor core are provided in the semicircular portion constituting one pole of the rotor core such that, when viewed in the axial direction, the cross-sectional shape is relatively narrow on the centerline side and wider on both ends.

4. A synchronous motor that enables self-starting, A cylindrical rotor core has a rotating shaft at its center and multiple slots with elongated cross-sections arranged circumferentially on its outer circumference, A cage-type conductor including a plurality of conductor bars provided in each slot of the rotor core and end rings connecting these conductor bars at both axial ends of the rotor core, The rotor core is provided with permanent magnets that form two rotor magnetic poles and are located on the inner layer side of the slots, The permanent magnets are arranged in a semicircular portion that constitutes one pole of the rotor core, symmetrically with respect to a radially extending centerline when viewed in the axial direction, with two magnets disposed within two inner layer slits, each having an outer end continuous with or close to one of the inner circumferential ends of the slots, and an inner end extending to the centerline portion. The opening angle α between the two slots that are continuous or adjacent to each of the aforementioned inner layer slits is 100° or more. A synchronous motor in which the slots on the outer circumference of the rotor core are arranged such that, depending on the formation position, the position of the vertex located at the outer circumference end is inclined in the circumferential direction with respect to the radial direction.

5. A pump body and A pump device comprising a motor that serves as a driving source for the pump body, the synchronous motor described in any one of claims 1 to 4.

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