Synchronous reluctance motor, and design method for a synchronous reluctance motor.

Abstract

To provide a synchronous reluctance motor that can increase torque without reducing the mechanical strength of the rotor. [Solution] The synchronous reluctance motor 1 comprises a rotor 50 in which a plurality of flux barriers 51 and strip-shaped magnetic paths 53 are formed in layers along the radial direction, with the flux barriers 51 being convexly curved toward the rotation axis when viewed from the rotation axis direction, and a stator 30 disposed coaxially with the rotor 50 and on the outside of the rotor 50. The rotor 50 is arranged symmetrically with respect to an axis (d-axis) passing through the center of the flux barriers 51 in the radial direction when viewed from the rotation axis direction, and has a pair of bridges 52 that straddle the flux barriers 51. The circumferential distance between the pair of bridges 52 is set within a predetermined distance in which the region in which magnetic saturation occurs and the permeability decreases due to magnetic flux leaked from one bridge 52 extends to the other bridge 52.

Description

Technical Field

[0001] The present invention relates to a synchronous reluctance motor and a design method for the synchronous reluctance motor.

Background Art

[0002] A synchronous reluctance motor (SynRM) has characteristics such as high efficiency, resource saving, and low cost compared to a permanent magnet synchronous motor (PMSM) or an induction motor (IM) because, for example, a permanent magnet or a rotor conductor is not required.

[0003] A synchronous reluctance motor is a motor that obtains a field magnetic flux by the salient pole property of a rotor (rotating element) (generates magnetic flux with the reactive component of the lagging current). The salient pole property of this synchronous reluctance motor can be obtained, for example, by creating magnetic anisotropy by a flux barrier (gap) formed in the rotor.

[0004] On the other hand, forming a flux barrier (gap) in the rotor reduces the mechanical strength of the rotor against the rotational centrifugal force load. Here, for example, Patent Document 1 discloses a synchronous reluctance motor that increases the mechanical strength against the rotational centrifugal force load and suppresses deformation of the rotor core by providing a bridge across the flux barrier (gap) in the radial direction.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, if a bridge is provided that spans the flux barrier radially, magnetic flux will leak through the bridge (i.e., the magnetic flux will flow in the direction that should be hindering it (radial direction)), which will reduce the salient polarity of the rotor and lead to a decrease in reluctance torque (i.e., a decrease in motor performance).

[0007] The present invention was made to solve the above-mentioned problems, and aims to provide a synchronous reluctance motor that can increase torque without reducing the mechanical strength of the rotor, and a method for designing the synchronous reluctance motor. [Means for solving the problem]

[0008] A synchronous reluctance motor according to one aspect of the present invention comprises a rotor in which a plurality of flux barriers and strip-shaped magnetic paths, which are curved convexly toward the axis of rotation when viewed from the axis of rotation, are formed in layers along the radial direction, and a stator disposed coaxially with the rotor and on the outside of the rotor, wherein the rotor is arranged symmetrically with respect to an axis passing through the center of the flux barriers in the radial direction when viewed from the axis of rotation, and has a pair of bridges that straddle the flux barriers, and the circumferential distance between the pair of bridges is set to a predetermined distance in which the region in which magnetic saturation occurs due to magnetic flux leaked from one bridge and the permeability decreases extends to the other bridge.

[0009] According to one aspect of the present invention, the rotor is arranged symmetrically with respect to an axis passing through the center of the flux barrier in the radial direction when viewed from the direction of rotation, and has a pair of bridges that straddle the flux barrier, and the circumferential distance between the pair of bridges is set to a predetermined distance such that the region in which magnetic saturation occurs and the permeability decreases due to magnetic flux leaked from one bridge extends to the other bridge. As a result, the leakage of magnetic flux (radial flow) from the other bridge is hindered by the region with reduced permeability, and the leakage of magnetic flux from the other bridge is reduced. Therefore, for example, compared to a motor with a single bridge in the radial direction, torque can be improved while maintaining equivalent mechanical strength. [Effects of the Invention]

[0010] According to the present invention, it is possible to increase torque without reducing the mechanical strength of the rotor. [Brief explanation of the drawing]

[0011] [Figure 1] This is a cross-sectional view showing the structure of a synchronous reluctance motor according to an embodiment. [Figure 2] This is a diagram showing an enlarged view of the main part of the rotor (one pole) that constitutes the synchronous reluctance motor according to the embodiment. [Figure 3] This diagram shows the relationship between the distance between a pair of bridges and the motor torque. [Figure 4] This figure shows an example of the results of an electromagnetic field analysis simulation. [Modes for carrying out the invention]

[0012] Preferred embodiments of the present invention will be described in detail below with reference to the drawings. Unless otherwise necessary, the same reference numerals will be used for the same or corresponding parts in the drawings. Furthermore, in each drawing, the same reference numerals will be used for the same elements, and redundant descriptions will be omitted.

[0013] First, the configuration of the synchronous reluctance motor 1 according to this embodiment will be explained using Figures 1 and 2 together. Figure 1 is a cross-sectional view (a cross-sectional view perpendicular to the axis of rotation) showing the structure of the synchronous reluctance motor 1. Figure 2 is an enlarged view showing the main part of the rotor 50 (one pole) that constitutes the synchronous reluctance motor 1.

[0014] The synchronous reluctance motor 1 mainly comprises a stator 30 consisting of a stator core 31 with an annular cross-section and a plurality of coils 34 wound around the stator core 31, and a rotor 50 rotatably disposed inside the stator 30.

[0015] The stator 30 is mainly composed of an annular (cylindrical) stator core 31 having a plurality of teeth 33, and stator windings (coils) 34 wound around each of the teeth 33.

[0016] The stator core 31 is configured in an annular (cylindrical) shape by arranging multiple stator segments (divided cores) in the circumferential direction of the stator 30. Each stator segment is composed of an arc-shaped yoke 32 extending in the circumferential direction of the stator core 31 and multiple teeth 33 protruding radially inward from the stator core 31. Each stator segment is also composed of laminated electromagnetic steel sheets having a directionality, such as silicon steel sheets.

[0017] With this configuration, the stator core 31 has a plurality of teeth 33 that extend radially inward at predetermined intervals along the circumferential direction. The teeth 33 are formed such that when cut by a plane perpendicular to the radial direction of the stator core 31 (the axis of the teeth 33), they exhibit a substantially rectangular (or circular) cross-sectional shape.

[0018] Stator windings (coils) 34, which consist of windings made of highly conductive wires such as copper covered with insulating material such as enamel, are wound around the sides of the teeth 33.

[0019] The rotor 50 is positioned inside the stator 30 and coaxially with the stator 30. The rotor 50 is composed of, for example, a laminate of steel plates formed by stacking multiple annular electromagnetic steel plates. Alternatively, the rotor 50 can be made of, for example, a compacted powder made of magnetic powder such as soft magnetic metal powder or soft magnetic metal oxide powder coated with a resin binder such as silicone resin. The output shaft 70 is fitted (for example, press-fitted) into the center of the rotor 50.

[0020] On the rotor 50, a plurality of flux barriers (gaps) 51 that are convexly curved (arc-shaped) toward the rotation axis side (inner side) and a band-shaped magnetic path 53 are formed in layers along the radial direction when viewed from the rotation axis direction. In this embodiment, four flux barriers 51 are provided per pole. Also, in this embodiment, the number of poles of the motor is eight.

[0021] Here, the direction in which the flow of magnetic flux is not obstructed by the flux barrier 51 (i.e., the direction in which magnetic flux easily passes) is defined as the q-axis. On the other hand, the direction in which the flow of magnetic flux is obstructed by the flux barrier 51 (the direction in which magnetic flux hardly passes), that is, the direction that is magnetically orthogonal to the q-axis, is defined as the d-axis. That is, the d-axis is an axis (an axis passing through the center of the rotation axis and the center of the flux barrier 51) that passes through the center of the flux barrier 51 in the radial direction when viewed from the rotation axis direction.

[0022] In particular, the synchronous reluctance motor 1 has a function of increasing torque without reducing (while maintaining) the mechanical strength of the rotor 50 as compared with, for example, a motor having a single bridge on the d-axis.

[0023] Therefore, the rotor 50 has a pair of bridges 52 that are arranged symmetrically (i.e., equidistantly) with respect to the d-axis when viewed from the rotation axis direction and straddle the flux barrier 51.

[0024] The pair (two) of bridges 52 are formed to extend parallel to each other and in the radial direction when viewed from the rotation axis direction so as to straddle each of the plurality of flux barriers 51.

[0025] And the circumferential distance (interval) between the pair of bridges 52 is set (designed) within a predetermined distance where the region where magnetic saturation occurs due to the magnetic flux leaking from one bridge 52 and the magnetic permeability decreases (refer to the substantially triangular region in FIG. 2) reaches the other bridge 52.

[0026] More specifically, the circumferential distance (spacing) between a pair of bridges 52 is set (designed) such that the region where magnetic saturation occurs due to magnetic flux leaked from one bridge 52 and the relative permeability (or permeability) falls below a predetermined value (for example, around 30) (see the roughly triangular region in Figure 2) can cover (block) the connection portion of the other bridge 52 with the strip-shaped magnetic path 53.

[0027] Therefore, the leakage of magnetic flux from one bridge 52 causes magnetic saturation and a decrease in relative permeability (or permeability) in that region, which hinders the leakage of magnetic flux (radial flow) from the other bridge 52, thereby reducing the leakage of magnetic flux from the other bridge 52.

[0028] On the other hand, the circumferential distance (spacing) between the pair of bridges 52 is set (designed) to be wider than a predetermined distance (spacing) at which they can be considered as a single bridge magnetically positioned on the d-axis.

[0029] Figure 3 shows the relationship between the distance (spacing) between a pair of bridges 52 and the motor torque. The horizontal axis in Figure 3 represents the position of the bridges 52 (distance from the d-axis) (mm), and the vertical axis represents the maximum torque (Nm). As shown in Figure 3, the greater the distance (spacing) between the pair of bridges 52, the weaker the effect of suppressing leakage flux on the other bridge 52 becomes, causing the magnetic flux from both bridges to leak, and the torque to decrease.

[0030] On the other hand, if the distance (spacing) between the pair of bridges 52 becomes too close (too close), it can be considered as a single bridge (a single bridge with twice the cross-sectional area) positioned on the d-axis, and the torque decreases. Therefore, the distance (spacing) between the pair of bridges 52 is set (designed) so that the torque is maximized (takes its peak value).

[0031] When setting (designing) the distance (spacing) between a pair of bridges 52, it is preferable to repeatedly determine the optimal value by simulating (electromagnetic field analysis using the finite element method) the region (range) where magnetic saturation occurs and permeability decreases, by varying, for example, the thickness (cross-sectional area) of each of the pair of bridges 52 and the distance (spacing) between the pair of bridges 52 relative to the design specifications of the stator 30 and rotor 50. For electromagnetic field analysis software, for example, JMAG Designer from JSOL Corporation can be used.

[0032] Here, Figure 4 shows an example of the results of an electromagnetic field analysis simulation. According to the simulation results (example) shown in Figure 4, it can be confirmed that the region with a relative permeability of less than 30 is blocking the exit of the bridge 52 (the connection point with the strip-shaped magnetic path 53).

[0033] As described in detail above, according to this embodiment, the rotor 50 has a pair of bridges 52 that are symmetrically arranged on the d-axis and straddle the flux barrier 51, and the circumferential distance (spacing) between the pair of bridges 52 is set (designed) within a predetermined distance such that the region in which magnetic saturation occurs and the permeability decreases due to magnetic flux leaked from one bridge 52 extends to the other bridge 52. As a result, the leakage of magnetic flux (radial flow) from the other bridge 52 is hindered by the region with reduced permeability, and the leakage of magnetic flux from the other bridge 52 is reduced. Therefore, compared to, for example, a single bridge on the d-axis (a single bridge with a cross-sectional area equal to the sum of the circumferential cross-sectional areas of the pair of bridges 52), it is possible to improve torque while having equivalent mechanical strength.

[0034] As a result, it becomes possible to increase torque without reducing the mechanical strength of the rotor 50.

[0035] Furthermore, according to this embodiment, since the pair of bridges 52 are arranged symmetrically on either side of the d-axis, the same characteristics can be achieved during power generation and regeneration (i.e., regardless of the direction of motor rotation).

[0036] According to this embodiment, a pair (two) of bridges 52 are formed to be parallel to each other and extend radially when viewed from the direction of the rotation axis, straddling each of the multiple flux barriers 51. Therefore, in each of the pair (two) of bridges 52 formed to stradd each of the multiple flux barriers 51, magnetic flux leakage from the other bridge 52 can be reduced. Thus, for example, compared to a system with a single bridge in the radial direction, torque can be improved while maintaining equivalent mechanical strength.

[0037] According to this embodiment, the circumferential distance (spacing) between a pair of bridges 52 is set (designed) such that the region where magnetic saturation occurs due to magnetic flux leaked from one bridge 52, causing the relative permeability (or permeability) to fall below a predetermined value, can cover the connection portion of the other bridge 52 with the strip-shaped magnetic path 53. Therefore, magnetic flux leakage (flow) from the other bridge 52 can be effectively prevented, and magnetic flux leakage from the other bridge 52 can be effectively reduced (suppressed).

[0038] According to this embodiment, the circumferential distance (spacing) between a pair of bridges 52 is set (designed) to be wider than a predetermined distance (spacing) at which they can be considered as a single bridge arranged magnetically on the d-axis. Here, as described above, if the distance (spacing) between the pair of bridges 52 gets closer (too close), they can be considered as a single bridge arranged on the d-axis (a single bridge with twice the cross-sectional area), and the torque decreases. Therefore, by setting (designing) the circumferential distance (spacing) between the pair of bridges 52 to be within a predetermined distance at which the region where magnetic saturation occurs due to magnetic flux leaked from one bridge 52 and the permeability decreases extends to the other bridge 52, and further away (farther away) than a predetermined distance at which they can be considered as a single bridge arranged on the d-axis (a single bridge with twice the cross-sectional area), it is possible to set the distance (spacing) to the distance at which the torque is maximized (to take the torque peak).

[0039] Although embodiments of the present invention have been described above, the present invention is not limited to the above embodiments and various modifications are possible. For example, in the above embodiments, the flux barrier 51 was made up of four layers, but the number of layers of the flux barrier 51 is not limited to four layers, and may be two, three, or five or more layers. Also, the number of poles of the motor is not limited to eight poles, and may be four, six, or ten or more poles.

[0040] Furthermore, the dimensions, materials, and other specific numerical values ​​shown in the above embodiments are illustrative examples to facilitate understanding of the present invention and do not limit the present invention unless otherwise specified. [Explanation of Symbols]

[0041] 1 Synchronized reluctance motor 30 Stator 31 Stator Core 32 York 33 Teeth 34 Stator windings (coils) 50 Rotors 51 Flux barrier (void) 52 Bridge 53. Strip-shaped magnetic circuits 70 Output shaft

Claims

1. A rotor in which, when viewed from the direction of the rotation axis, multiple flux barriers and strip-shaped magnetic paths, which are curved convexly toward the rotation axis side, are formed in layers along the radial direction, The system comprises a stator disposed coaxially with the rotor and on the outside of the rotor, The rotor, when viewed from the direction of rotation, is arranged symmetrically with respect to an axis passing through the center of the flux barrier in the radial direction, and has a pair of bridges that straddle the flux barrier. A synchronous reluctance motor characterized in that the circumferential distance between the pair of bridges is set within a predetermined distance in which the region where magnetic saturation occurs and the permeability decreases due to magnetic flux leaked from one bridge extends to the other bridge.

2. The synchronous reluctance motor according to claim 1, characterized in that the pair of bridges are parallel to each other and extend radially when viewed from the direction of the rotation axis, and are formed to straddle each of the plurality of flux barriers.

3. The synchronous reluctance motor according to claim 2, characterized in that the circumferential distance between the pair of bridges is set such that the region where magnetic saturation occurs due to magnetic flux leaked from one bridge and the permeability falls below a predetermined value can cover the connection portion of the other bridge with the strip-shaped magnetic path.

4. The synchronous reluctance motor according to claim 3, characterized in that the circumferential distance between the pair of bridges is set to be wider than the distance at which they can be magnetically considered as a single bridge arranged radially on an axis passing through the center of the flux barrier.

5. A method for designing a synchronous reluctance motor comprising a rotor having multiple flux barriers and strip-shaped magnetic paths formed in layers along the radial direction, which are curved convexly toward the axis of rotation when viewed from the axis of rotation, and a stator disposed coaxially with the rotor and on the outside of the rotor, On the rotor, a pair of bridges are arranged symmetrically across the flux barrier, with respect to the axis passing through the center of the flux barrier in the radial direction when viewed from the direction of rotation, A method for designing a synchronous reluctance motor, characterized in that the circumferential distance between the pair of bridges is set to a predetermined distance within which the region in which magnetic saturation occurs due to magnetic flux leaked from one bridge and the permeability decreases extends to the other bridge.

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