Synchronous reluctance motor and drive device for rolling stock

Abstract

A synchronous reluctance motor (1) comprises: a stator core (9) in which a plurality of slots (14) are formed; and a rotor core (11) configured in a cylindrical shape on the inner-surface side of the stator core (9). The rotor core (11) has a plurality of slits (15), the openings of which are divided by a center rib (18a). The slit spacing of the rotor core (11) is formed to be smaller than the slot spacing of the stator core (9). At least three layers of slit groups are formed in the rotor core (11), and at least two of the at least three layers of slit groups are provided with a side rib (18b). When viewing the plurality of slit groups from the q-axis side to the d-axis side, the average magnetic path width Wt2-3 on the q-axis side of the layer where the side rib (18b) is first provided is larger than the average magnetic path width Wt3-4 on the d-axis side of the layer where the side rib (18b) is first provided.

Description

Synchronous reluctance motor and driving device for railway vehicles

[0001] The present disclosure relates to a synchronous reluctance motor that utilizes reluctance torque and a drive device for a railway vehicle.

[0002] Synchronous reluctance motors are used in railway vehicles, air conditioners, automobiles, and the like. Synchronous reluctance motors rotate by providing slits in the rotor core, which generates magnetic saliency and reluctance torque generated by the magnetic saliency. However, providing slits in the rotor core reduces the strength of the rotor core. The rotor core must be strong enough to withstand the centrifugal force generated when the rotor rotates. For this reason, reinforcing members called ribs are formed in the slits, as shown in Patent Document 1 below.

[0003] JP 2009-11118 A

[0004] However, the ribs formed on the rotor core create a path for leakage magnetic flux, which causes another problem: a decrease in maximum torque. In other words, there is a trade-off between the centrifugal force resistance strength of the rotor core and the maximum torque obtained by the ribs formed on the rotor core.

[0005] The present disclosure has been made in view of the above, and has an object to provide a synchronous reluctance motor that can suppress a decrease in maximum torque while maintaining the centrifugal force resistance strength of the rotor core.

[0006] To solve the above-mentioned problems and achieve the object, a synchronous reluctance motor according to the present disclosure includes an annular stator core having a plurality of slots formed at equal intervals along its inner circumferential surface, windings housed in each slot, and a cylindrical rotor core formed on the inner surface of the stator core. The rotor core has a plurality of slits, each of which is convex toward the center of the cylinder when viewed in the direction of the central axis of the cylinder, with its center located on the q axis of the magnetic pole and having an opening formed by two arcs with two radii of different lengths, and the openings are separated by a center rib. A slit group consisting of the plurality of slits is formed in layers toward the center of the cylinder for each magnetic pole. When the slit spacing is defined as the angle formed between adjacent slits and the center of the rotor core by the center point, which is the midpoint in the circumferential direction of the arc-shaped end of the arc-shaped opening of the slit closest to the outer periphery of the rotor core, along the outer circumferential surface of the rotor core, and the angle formed between adjacent slots in the stator core is defined as the slot spacing, the slit spacing is smaller than the slot spacing. The rotor core has at least three layers of slit groups formed therein, and at least two of the three layers of slit groups have side ribs that further divide the slits divided by the center rib. When the multiple slit groups are viewed from the q-axis side to the d-axis side, the average magnetic path width on the q-axis side of the layer on which the side rib is first provided is larger than the average magnetic path width on the d-axis side of the layer on which the side rib is first provided.

[0007] The synchronous reluctance motor according to the present disclosure has the advantage of being able to suppress a decrease in maximum torque while maintaining the centrifugal force resistance strength of the rotor core.

[0008] 4 and 5 are cross-sectional views illustrating the shape and position of the slits in the rotor core shown in FIG. 5; and FIG. 6 is a cross-sectional view illustrating the position of the center rib and the side rib in the slits shown in FIG. 6 to 8. Average magnetic path width W in the synchronous reluctance motor according to the first embodiment. ｔ２－３ , W ｔ３－４ and the stress generated in the rotor core. ｔ２－３ , W ｔ３－４ and the maximum torque obtained by the rotor core. ｔ２－３ , W ｔ３－４ 1 is a diagram illustrating the relationship between the magnitude relationship of the average magnetic path width W and the torque stress ratio in a synchronous reluctance motor according to the first embodiment. ｔ２－３ , W ｔ５－６ 13 is a diagram for explaining the relationship between the magnitude relationship of the torque stress ratio and the average magnetic path width W in the rotor core having the structure of FIG. 13. ｔ２－３ , W ｔ３－４ The ratio W ｔ２－３ / W ｔ３－４ and average magnetic path width W ｔ３－４ , W ｔ４－５ The ratio W ｔ３－４ / W ｔ４－５ 15 is a diagram for explaining the relationship between the magnitude relationship of the torque stress ratio and the average magnetic path width W in the rotor core having the structure of FIG. 15. ｔ２－３ , W ｔ３－４ The ratio W ｔ２－３ / W ｔ３－４ , average magnetic path width W ｔ３－４ , Wｔ４－５ The ratio W ｔ３－４ / W ｔ４－５ and average magnetic path width W ｔ４－５ , W ｔ５－６ The ratio W ｔ４－５ / W ｔ５－６ 13 is a cross-sectional view illustrating the definition of the rib width in the rotor core of the first embodiment. ｔ３－４ , W ｔ４－５ The ratio W ｔ３－４ / W ｔ４－５ 1 is a cross-sectional view showing one magnetic pole of a 6-pole, 36-slot synchronous reluctance motor according to the second embodiment; and 2 is a diagram illustrating the influence of the rib width on the relationship between the torque stress ratio and the average magnetic path width W in the synchronous reluctance motor according to the second embodiment. ｔ１－２ , W ｔ２－３ and torque stress ratio.

[0009] A synchronous reluctance motor and a railway vehicle drive device according to embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. Note that, in the following embodiments, a synchronous reluctance motor suitable for use in driving railway vehicles will be described as an example, but this does not mean that application to other uses will be excluded. Furthermore, in the accompanying drawings, the scale of each component may differ from the actual scale in order to prioritize ease of understanding. The same applies between the drawings.

[0010] Embodiment 1. Figure 1 is a diagram showing the general configuration of a drive device that drives a synchronous reluctance motor 1 according to embodiment 1. In Figure 1, the synchronous reluctance motor 1 is connected to a control device 3 via a power supply line 2. The synchronous reluctance motor 1 operates as an electric machine that converts electrical energy supplied from the control device 3 into mechanical energy. The drive device shown in Figure 1 can be used as a drive device for a railway vehicle.

[0011] Fig. 2 is a cross-sectional view of the synchronous reluctance motor 1 according to the first embodiment, taken along the axial direction of the shaft 4. The dashed line B in Fig. 2 is the axis of the shaft 4. Fig. 3 is a cross-sectional view of the synchronous reluctance motor 1 shown in Fig. 2, taken along line A-A in Fig. 2. Note that the frame 5 is not shown in Fig. 3.

[0012] The synchronous reluctance motor 1 has an annular stator 6 and a cylindrical rotor 7 that are inserted and fixed into a frame 5 by a method such as press fitting or shrink fitting. The annular stator 6 and the cylindrical rotor 7 are arranged to be relatively rotatable using bearings 8 with a magnetic gap 19, which is a mechanical gap, interposed between them.

[0013] The stator 6 is configured by wrapping a winding 10 around a circular stator core 9 made of an iron core. The rotor 7 is configured by inserting the shaft 4 into the center of a cylindrical rotor core 11 made of an iron core by a method such as press fitting or shrink fitting, thereby forming an integrated structure.

[0014] The stator core 9 is composed of an annular core back 12 and teeth 13 that protrude radially inward from the core back 12 and are arranged at equal intervals. A plurality of slots 14 are formed at equal intervals between the plurality of teeth 13 provided on the radially inner side of the stator core 9. The slots 14 house windings 10. The teeth 13 and slots 14 are also provided at the same angle in the circumferential direction of the annulus.

[0015] In Fig. 3, if the number of magnetic poles of rotor core 11 is P and the number of slots provided in stator core 9 is S, then P = 6 and S = 54. That is, Fig. 3 shows the cross-sectional structure of a 6-pole, 54-slot synchronous reluctance motor 1. Note that the numbers of slots and magnetic poles shown in Fig. 3 are merely examples and are not limited to the example shown in Fig. 3.

[0016] Fig. 4 is a cross-sectional view showing one magnetic pole of the 6-pole, 54-slot synchronous reluctance motor 1 shown in Fig. 3, and is an enlarged view of a 1 / 6 region in Fig. 3. Fig. 5 is a cross-sectional view used to explain the arrangement of slits 15 in rotor core 11 shown in Fig. 4.

[0017] First, as shown in Figure 4, the stator 6 of the 6-pole, 54-slot synchronous reluctance motor 1 has nine slots 14 per magnetic pole. In Figure 4, on the cross sections of the stator core 9 and rotor core 11, the d-axis is defined in the direction of the center lines of the magnetic poles, and the q-axis is defined in the direction of the center lines between the magnetic poles. The direction of the center lines of the magnetic poles is the direction in which magnetic flux easily passes, and the direction of the center lines between the magnetic poles is the direction in which magnetic flux does not easily pass. The d-axis direction is sometimes called the "salient pole direction," and the q-axis direction is sometimes called the "non-salient pole direction."

[0018] The d-axis and q-axis have an electrical phase difference of 90 degrees. The rotor 7 rotates due to the inductance torque generated based on the difference in inductance between the d-axis and q-axis directions. In other words, the synchronous reluctance motor 1 generates output torque by utilizing the difference in magnetic resistance in the rotational direction. Therefore, the greater the difference in inductance between the d-axis and q-axis, the higher the output torque the synchronous reluctance motor 1 can generate.

[0019] 4 and 5 , when viewed in the direction of the central axis of the cylinder, rotor core 11 is provided with a plurality of slits 15, each of which is an arc-shaped opening that is convex toward the cylindrical center O of rotor core 11 for each magnetic pole of rotor core 11 and has each apex located on the q axis of the magnetic pole. The plurality of slits 15 create spaces in rotor core 11. In other words, the slits 15 give rotor core 11 a structure in which magnetic portions made of a magnetic material, which is the material of the electromagnetic steel sheet, and non-magnetic portions made of air appear alternately.

[0020] 4, the d-axis passing through the cylindrical center O of rotor core 11 is taken as the center point W, which is the midpoint in the circumferential direction of the arc-shaped end portion along the outer peripheral surface of rotor core 11 at the arc-shaped opening of slit 15 closest to the outer periphery of rotor core 11. The angle θ is taken as the angle formed between the center point W of each slit 15 provided within one magnetic pole and the cylindrical center O of rotor core 11 between adjacent slits.

[0021] In this case, the slits 15 are arranged so that the angle θ formed by the center point W between adjacent slits is equal to the distance between the adjacent slits. The angle formed by the line connecting the center point W of the slit 15 closest to the d axis and the cylindrical center O of the rotor core 11 with the d axis is set to θ / 2. Specifically, in the configuration of FIG. 4 , θ is set to 5.0 (= 360 / 72) degrees. In this document, this angle θ is referred to as the "slit spacing θ," and the number of angles θ around the entire circumference of the rotor core 11 is sometimes referred to as the "number of pitches." In the structure of FIG. 4 , the number of pitches is 72.

[0022] In addition, in Figure 4, the angle between adjacent slots is called the "slot spacing" and is represented by δ. In the structure of Figure 4, the number of slots S = 54, and δ = 6.67 (= 360 / 54) degrees. Therefore, in the structure of Figure 4, there is a relationship of θ < δ between the slit spacing θ and the slot spacing δ. Note that the relationship of θ < δ is maintained in other embodiments described later.

[0023] 4 illustrates an example in which the slits are arranged so that the slit spacing θ is equal between adjacent slits around the entire circumference of the rotor core 11. In contrast, the gist of the first embodiment is that the slit spacing θ is adjusted based on the concept of "magnetic path width," which will be described later. Details will be provided later. Even if the slit spacing θ is adjusted, the relationship θ<δ is maintained.

[0024] Furthermore, b in FIG. 5 indicates the layer number of the slits 15 provided for each magnetic pole. In FIG. 5, the layer closest to the q axis of the rotor core 11 is designated b=1, and the layer with b=1 is referred to as the "first layer." Then, from the slits 15 in the first layer toward the d axis, b=2 to 6 are assigned, and these are referred to as the "second layer" to "sixth layer," respectively. That is, in the structure of FIG. 5, the layers in which the slits 15 are provided consist of six layers, from the first layer to the sixth layer, in order from the q axis side. Note that in the examples of FIGS. 3 to 5, b=6 is set, but this is not limiting. The slit spacing θ may be any number necessary to satisfy the aforementioned relationship of θ<δ, and in the example of FIG. 5, b=5 may be used.

[0025] 5, odd numbers indicate the arc numbers of the outer edges of the slits 15 provided for each magnetic pole, which are the arc numbers of the edges farther from the center O of the cylinder, and even numbers indicate the arc numbers of the inner edges of the slits 15, which are the arc numbers of the edges closer to the center O of the cylinder. For example, the outer edges of the slits 15 in the b-th layer are the n=2b-1 arc, and the inner edges of the slits 15 in the b-th layer are the n=2b arc. The arcs shown in FIG. 5 have 6 slit layers, and can take on values ​​of n=1 to 12.

[0026] As described above, the rotor core 11 must be strong enough to withstand the centrifugal force generated when the rotor 7 rotates. For this reason, a center rib 18a that acts as a strength member is formed in each of the slits 15 in the first to sixth layers. Furthermore, in addition to the center rib 18a, two side ribs 18b that also act as strength members are formed in each of the slits 15 in the third to sixth layers. The center rib 18a and the side ribs 18b can be formed by leaving the center rib 18a and the side ribs 18b unpunched when forming the slits 15 by punching out a thin steel plate.

[0027] As described above, each slit 15 in the first and second layers has only a center rib 18a, while each slit 15 in the third to sixth layers has both a center rib 18a and a side rib 18b. In this paper, the multiple slits 15 in each layer are collectively referred to as a "slit group." That is, each of the first to sixth layers has a slit group consisting of multiple slits 15 separated by a center rib 18a or a side rib 18b. Thus, each of the first to sixth layers has a center rib 18a separating the slits 15 in each slit group, and each of the third to sixth layers has a side rib 18b further separating the slits 15 separated by the center rib 18a. Furthermore, in each layer, the slits 15 belonging to each slit group are arranged symmetrically with respect to the q axis for each magnetic pole.

[0028] FIG. 6 is a cross-sectional view illustrating the shape and position of the slits 15 in the rotor core 11 shown in FIGS. 4 and 5 . As described above, the multiple slits 15 have arc-shaped openings with their vertices located on the q axis of the magnetic pole. Each arc has an arc center Q on the q axis and at a distance D from the cylindrical outer peripheral surface of the rotor core 11. The radius of the nth arc relative to each arc center Q(n) is defined as R(n), and the distance D determined by the nth arc is defined as D(n). n is the arc number shown in FIG. 5 . Here, the ratio of the distance D(n) to the radius R(n) of the nth arc is defined as k(n), and the ratio k(n) of the distance D(n) to the radius R(n) is defined as shown in Equation (1) below.

[0029] k(n)=D(n) / R(n)...(1)

[0030] The distance D(n) is a constant determined by the nth arc, and the radius R(n) of the nth arc varies depending on the ratio k(n) to the nth arc, where the ratio k(n) satisfies the relationship of the following equation (2):

[0031] k(nmax)<...<k(n)<...<k(1)<1...(2)

[0032] In the above formula (2), nmax is the maximum number of arcs that can be formed. Note that an arc that is approximated by a straight line, for example, is also considered to have the same shape.

[0033] Furthermore, when the slits 15 in the sixth layer are formed with an arc radius R(12), the outer edges of the slits 15 extend beyond the adjacent magnetic pole. For this reason, as shown in each of Figures 4 to 6, the outer edges of the slits 15 are formed at a certain distance from the d-axis and within their own magnetic pole so as not to extend beyond the adjacent magnetic pole.

[0034] Next, a method for determining the distance D(n), radius R(n), and ratio k(n) will be described. First, let point X be the point on the q axis shown in Figure 6 that is the radius of the rotor 7, and let points Y and Y' be the points where the nmax-th arc intersects with the outer peripheral surface of the rotor core 11. If the maximum number of slit layers is bmax, then the maximum number nmax that can be taken by the arcs is determined by the maximum number bmax.

[0035] The radius R(nmax) of the nmax-th arc is a circle that passes through points Y and Y' and has an arc center Q on the q axis. Therefore, once the ratio k(nmax) is determined, the radius R(nmax) and distance D(nmax) of the nmax-th arc are determined based on the above formula (1).

[0036] In addition, in Figure 6, the case where D(1) > D(2) > ... > D(11) > D(12) is illustrated, but the order does not necessarily have to be as shown in Figure 6, and it is sufficient if the distance D(n) is determined so as to satisfy the above equations (1) and (2).

[0037] As explained above, rotor core 11 is cylindrically shaped on the inner surface of stator core 9, and when viewed in the direction of the central axis of the cylinder, has an opening that is convex toward the center of the cylinder for each magnetic pole, has a center located on the q axis of the magnetic pole, and is formed by two arcs with two radii of different lengths. Rotor core 11 also has a plurality of slits 15 whose openings are separated by center ribs 18a, and slit groups made up of the plurality of slits 15 are formed in layers toward the center of the cylinder for each magnetic pole.

[0038] FIG. 7 is a cross-sectional view illustrating the positions of the center rib 18a and the side ribs 18b in the slits 15 shown in FIGS. 4 to 6. First, the center rib 18a is provided on the q-axis in each of the first to sixth layers. The side ribs 18b are formed at positions where the slits 15 in each of the third to sixth layers intersect with lines L1 and L2, which are centered at point Z on the q-axis, which is located outside point X, the radius of the rotor 7 on the q-axis, and extend radially toward the rotor core 11 at an angle α with respect to the q-axis. The side ribs 18b formed in the third to sixth layers do not necessarily need to be formed in a straight line along line L1 or line L2, but may be formed offset to the left or right from line L1 or line L2.

[0039] Next, the configuration of the main parts according to the first embodiment will be described. Fig. 8 is a cross-sectional view illustrating the definition of the average magnetic path width in rotor core 11 according to the first embodiment. Note that, since slits 15 in rotor core 11 are arranged symmetrically with respect to the q axis, only the right half of the q axis is shown in Fig. 8. This also applies to the subsequent figures.

[0040] As described above, in the rotor core 11 of the first embodiment, the slits 15 in the first and second layers do not have side ribs 18b, but the slits 15 in the third to sixth layers have side ribs 18b. In each layer, the magnetic material between each layer forms a magnetic path through which magnetic flux flows. Here, the magnetic path width between each layer differs even between layers with the same layer number. For this reason, in this paper, the average value of the magnetic path width between the q-axis and the outer periphery of the rotor core 11 is called the "average magnetic path width." Under this definition, the average magnetic path width between the slit group in the second layer and the slit group in the third layer is called W ｔ２－３ Similarly, the average magnetic path width between the slit group in the third layer and the slit group in the fourth layer is expressed as W ｔ３－４ and the average magnetic path width between the slit group in the fourth layer and the slit group in the fifth layer is W ｔ４－５ and the average magnetic path width between the slit group in the fifth layer and the slit group in the sixth layer is W ｔ５－６ It is expressed as:

[0041] Next, the results of an electromagnetic field analysis performed on the rotor core 11 according to the first embodiment using the finite element method will be described. First, the average magnetic path width W ｔ２－３ , W ｔ３－４ In order to examine the influence of the magnitude relationship on rotor core 11 of synchronous reluctance motor 1, the stress generated in rotor core 11 and the maximum torque obtained by rotor core 11 were obtained by electromagnetic field analysis and summarized as shown in Figures 9 to 11. Note that stress here refers to the maximum value of stress generated in rotor core 11. The location where stress is maximum is the location where centrifugal force resistance strength is lowest, and stress is introduced as an index representing the centrifugal force resistance strength of rotor core 11.

[0042] FIG. 9 shows the average magnetic path width W ｔ２－３ , W ｔ３－４ 9 is a diagram illustrating the relationship between the magnitude relationship of the average magnetic path width W ｔ３－４ Average magnetic path width W ｔ２－３ The ratio of W ｔ２－３ / W ｔ３－４ 9 represents the stress value generated in the rotor core 11, and the vertical axis of FIG.

[0043] The dashed line in Figure 9 indicates the specified value that the stress must not exceed when the synchronous reluctance motor 1 is rotated at 6,000 rpm. 6,000 rpm is the maximum rotational speed that is expected when the synchronous reluctance motor 1 is used to drive a railway vehicle. As shown in Figure 9, when the synchronous reluctance motor 1 is rotated at 6,000 rpm, the ratio W ｔ２－３ / W ｔ３－４ When the ratio W ｔ２－３ / W ｔ３－４ The variable range of the ratio W is approximately 0.98 or more and 1.13 or less. ｔ２－３ / W ｔ３－４ When is 1, that is, the average magnetic path width W ｔ２－３ and the average magnetic path width W ｔ３－４ It has been shown that the stress is lowest when and are equal.

[0044] FIG. 10 shows the average magnetic path width W ｔ２－３ , W ｔ３－４ 10 is a diagram illustrating the relationship between the magnitude relationship of the ratio W and the maximum torque obtained by the rotor core 11. ｔ２－３ / W ｔ３－４ The vertical axis of FIG. 10 represents the ratio W ｔ２－３ / W ｔ３－４ The maximum torque when the ratio W ｔ２－３ / W ｔ３－４ The value is normalized by the maximum torque when the ratio W is 1. ｔ２－３ / W ｔ３－４ If the ratio is greater than 1, the maximum torque increases, and the ratio W ｔ２－３ / W ｔ３－４ It is shown that when is made smaller than 1, the maximum torque becomes smaller.

[0045] FIG. 11 shows the average magnetic path width W ｔ２－３ , W ｔ３－４ 11 is a diagram illustrating the relationship between the magnitude relationship of the torque stress ratio and the torque stress ratio. The torque stress ratio represents the ratio of the maximum torque to the stress. The horizontal axis of FIG. 11 is the ratio W ｔ２－３ / W ｔ３－４ The vertical axis of FIG. 11 represents the ratio W ｔ２－３ / W ｔ３－４ The torque stress ratio (maximum torque / stress) when the ratio W ｔ２－３ / W ｔ３－４ The torque stress ratio is expressed as a normalized value when the ratio W is 1. ｔ２－３ / W ｔ３－４ When the ratio W is 0.98, ｔ２－３ / W ｔ３－４ When the torque stress ratio is 1, the torque stress ratio is larger. ｔ２－３ / W ｔ３－４ is 1, the ratio W ｔ２－３ / W ｔ３－４ It is shown that the torque stress ratio is larger when is 1.13.

[0046] The analysis results of Figures 9 to 11 will be considered. First, in the case of the structure of Figure 8, the average magnetic path width W ｔ２－３ is the average magnetic path width of the magnetic path on the q-axis side of the layer on which the side rib 18b is first provided, when the plurality of slit groups are viewed from the q-axis side to the d-axis side. ｔ３－４ is the average magnetic path width of the magnetic path on the d-axis side of the layer on which the side rib 18b is first provided. Therefore, the average magnetic path width W ｔ２－３ The average magnetic path width W on the d-axis side ｔ３－４ It can be explained that if the torque stress ratio is increased to be larger than the above, the torque stress ratio can be improved.

[0047] Next, the reason why the above results are obtained will be explained. First, the average magnetic path width W ｔ２－３ Increasing the amount of iron core increases the amount of iron core, and the stress in the increased area and the surrounding area increases. On the other hand, in the structure of FIG. 8, the slit groups in the third to sixth layers are provided with side ribs 18b, so the third to sixth layers have a structure in which the rotor core 11 is supported by two ribs, the center rib 18a and the side rib 18b. Therefore, the areas where the stress is high are dispersed within the rotor core 11, and the average magnetic path width W ｔ２－３ It is believed that there was almost no increase in maximum stress due to the increase in the iron core volume. In addition, it is believed that the increase in the iron core volume alleviated magnetic saturation of rotor core 11, thereby improving maximum torque.

[0048] Although the details of the analysis results are omitted, in the rotor core 11 having the structure shown in FIG. 8, the ratio W ｔ２－３ / W ｔ３－４ It has also been found that when the average magnetic path width W in FIG. ｔ２－３ , W ｔ５－６ The effect of the magnitude relationship of these on the torque stress ratio was examined.

[0049] FIG. 12 shows the average magnetic path width W ｔ２－３ , W ｔ５－６12 is a diagram illustrating the relationship between the magnitude relationship of the ratio W and the torque stress ratio. ｔ２－３ / W ｔ５－６ The vertical axis of FIG. 12 represents the ratio W ｔ２－３ / W ｔ５－６ The torque stress ratio (maximum torque / stress) when the ratio W ｔ２－３ / W ｔ５－６ The values ​​are normalized by the torque stress ratio when is 1.

[0050] According to FIG. 12, the ratio W ｔ２－３ / W ｔ５－６ This result shows that the torque stress ratio hardly changes even if the average magnetic path width W ｔ２－３ Without changing the value of ｔ２－３ / W ｔ５－６ This is thought to be because even if the ratio W is increased or decreased, the direction in which the maximum torque increases or decreases and the direction in which the stress increases or decreases coincide with each other. ｔ２－３ / W ｔ３－４ In this case, the direction of increase / decrease in maximum torque and the direction of increase / decrease in stress are in a contradictory relationship, so the ratio W ｔ２－３ / W ｔ３－４ It is believed that increasing the torque stress ratio increases.

[0051] In the above, based on the analysis results for the rotor core 11 having the structure of FIG. 8, the average magnetic path width W on the q-axis side of the layer in which the side ribs 18b are first provided is ｔ２－３ The average magnetic path width W on the d-axis side ｔ３－４ It has been explained that the torque stress ratio can be improved by making the value of the rotor core 11 larger than the value of the rotor core 11 shown in FIG. 13. Other structural examples were also examined to see if this idea was valid. Fig. 13 is a cross-sectional view of a rotor core 11 showing a first example of a structure different from that shown in Fig. 8.

[0052] While Fig. 8 shows a structure in which side ribs 18b are formed in each slit group from the third to sixth layers, Fig. 13 shows a structure in which side ribs 18b are formed in each slit group from the fourth to sixth layers. That is, in Fig. 13, side ribs 18b are not provided in the slit group of the third layer, and the layer on which side ribs 18b are first provided is the fourth layer. The definition of the average magnetic path width is the same as in Fig. 8.

[0053] FIG. 14 shows the average magnetic path width W ｔ２－３ , W ｔ３－４ The ratio W ｔ２－３ / W ｔ３－４ and average magnetic path width W ｔ３－4 , W ｔ４－５ The ratio W ｔ３－4 / W ｔ４－５ 14 is a diagram illustrating the relationship between the magnitude relationship of the ratio W and the torque stress ratio. ｔ２－３ / W ｔ３－４ and ratio W ｔ３－4 / W ｔ４－５ The vertical axis of FIG. 14 represents the ratio W ｔ２－３ / W ｔ３－４ and ratio W ｔ３－4 / W ｔ４－５ The torque stress ratio (maximum torque / stress) when one of the values ​​is fixed to 1 and the other is changed is expressed as the ratio W ｔ２－３ / W ｔ３－４ and ratio W ｔ３－4 / W ｔ４－５ The values ​​are normalized by the torque stress ratio when both are 1. Specifically, the plots connected by a solid line represent the ratio W ｔ３－4 / W ｔ４－５ The value of is fixed to 1, and the ratio W ｔ２－３ / W ｔ３－４ The results are for values ​​of 0.85, 1, and 1.16, and the plots connected by dashed lines represent the ratio W ｔ２－３ / W ｔ３－４ The value of is fixed to 1, and the ratio W ｔ３－4 / W ｔ４－５ The results are for values ​​of 0.84, 1 and 1.13.

[0054] According to the results of FIG. 14, similar to the rotor core 11 having the structure of FIG. 8, the ratio W ｔ２－３ / W ｔ３－４ However, unlike the results shown in FIG. 11, the torque stress ratio did not improve, and instead decreased. Therefore, the average magnetic path width W on the q-axis side of the layer on which the side ribs 18b are not initially provided is ｔ２－３ The average magnetic path width W on the d-axis side ｔ３－４ It can be seen that even if the ratio W is increased, the effect of improving the torque stress ratio cannot be obtained. ｔ３－4 / Wｔ４－５ Therefore, the result that the torque stress ratio can be improved by making the average magnetic path width on the q-axis side of the layer on which side ribs 18b are first provided larger than the average magnetic path width on the d-axis side is also obtained in rotor core 11 having the structure in FIG.

[0055] 15 is a cross-sectional view of a rotor core 11 showing a second example of a structure different from that of FIG. 8. In FIG. 13, side ribs 18b are formed in each of the slit groups in the fourth to sixth layers, but in FIG. 15, side ribs 18b are formed only in each of the slit groups in the fifth and sixth layers. That is, in FIG. 15, side ribs 18b are not provided in the slit groups up to the fourth layer, and the layer on which side ribs 18b are first provided is the fifth layer. The definition of the average magnetic path width is the same as in FIGS. 8 and 13.

[0056] FIG. 16 shows the average magnetic path width W ｔ２－３ , W ｔ３－４ The ratio W ｔ２－３ / W ｔ３－４ , average magnetic path width W ｔ３－4 , W ｔ４－５ The ratio W ｔ３－4 / W ｔ４－５ and average magnetic path width W ｔ４－５ , W ｔ５－６ The ratio W ｔ４－５ / W ｔ５－６ 16 is a diagram illustrating the relationship between the magnitude relationship of the ratio W and the torque stress ratio. ｔ２－３ / W ｔ３－４ , ratio W ｔ３－4 / W ｔ４－５ and ratio W ｔ４－５ / W ｔ５－６ The vertical axis of FIG. 16 represents the ratio W ｔ２－３ / W ｔ３－４ , ratio W ｔ３－4 / W ｔ４－５ and ratio W ｔ４－５ / W ｔ５－６ The value of the ratio W ｔ３－4 / W ｔ４－５ The solid line represents the value normalized by the torque stress ratio when the value of W is 1. ｔ２－３ / W ｔ３－４The dashed line represents the torque stress ratio when the ratio W ｔ３－４ / W ｔ４－５ The broken line represents the torque stress ratio when the ratio W ｔ４－５ / W ｔ５－６ It should be noted that when one ratio is changed to a value other than 1, the other two ratios are fixed at 1.

[0057] According to the results of FIG. 16, the ratio W ｔ４－５ / W ｔ５－６ Therefore, the result that the torque stress ratio can be improved by making the average magnetic path width on the q-axis side of the layer on which side ribs 18b are first provided larger than the average magnetic path width on the d-axis side is also obtained in rotor core 11 having the structure in FIG.

[0058] In the results of FIG. 16, the ratio W ｔ３－４ / W ｔ４－５ When the ratio W is increased, the torque stress ratio tends to improve. ｔ３－４ / W ｔ４－５ If the ratio W is increased, the stress may exceed the specified value when rotated at 6,000 rpm. Therefore, if the application has ample centrifugal force resistance, the ratio W ｔ３－４ / W ｔ４－５ On the other hand, when the synchronous reluctance motor 1 is used for driving a railway vehicle, the ratio W ｔ３－４ / W ｔ４－５ Without increasing the ratio W ｔ４－５ / W ｔ５－６ In a preferred embodiment, the larger value is used.

[0059] In the first embodiment, the influence of the rib width, which is the width in the short direction of the side ribs 18b, on the torque stress ratio was also examined. Fig. 17 is a cross-sectional view illustrating the definition of the rib width in the rotor core 11 of the first embodiment. Fig. 18 is a cross-sectional view illustrating the average magnetic path width W ｔ３－4 , W ｔ４－５ The ratio W ｔ３－4 / W ｔ４－５ 10 is a diagram illustrating the influence of the rib width on the relationship between the stress and torque stress ratio.

[0060] A supplementary note on Figures 17 and 18 will be provided. The structure of the rotor core 11 in Figure 17 is the same as that shown in Figure 13. In the analysis results of Figure 18, as shown in Figure 17, the rib width of the side ribs 18b of the fourth layer, where the side ribs 18b are provided first, was tested for three cases: 0.9 mm, 1.1 mm, and 1.3 mm. 0.9 mm was set as the minimum rib width expected when punching out the slits 15 from the thin steel plate while leaving the side ribs 18b. In addition, as for the ratio of the average magnetic path width of interest, the average magnetic path width W that is considered to be easily affected by the side ribs 18b of the fourth layer was set as the minimum rib width. ｔ３－4 , W ｔ４－５ The ratio W ｔ３－4 / W ｔ４－５ In Fig. 18, the solid line represents the torque stress ratio when the rib width is 0.9 mm, the broken line represents the torque stress ratio when the rib width is 1.1 mm, and the dashed line represents the torque stress ratio when the rib width is 1.3 mm. ｔ３－4 / W ｔ４－５ The values ​​are normalized by the torque stress ratio when is 1.

[0061] According to FIG. 18, the ratio W ｔ３－４ / W ｔ４－５ It has been shown that if the ratio W is within the range of 0.8 to 1.2, the torque stress ratio hardly changes. ｔ３－４ / W ｔ４－５ It has been shown that if the ratio W is 1 or more, the influence of the rib width is almost negligible. ｔ３－４ / W ｔ４－５ is the average magnetic path width W on the q-axis side of the layer on which the side rib 18b is first provided. ｔ３－４ and the average magnetic path width W on the d-axis side of the layer on which the side rib 18b is first provided. ｔ４－５ This ratio W ｔ３－４ / W ｔ４－５ As mentioned above, the torque stress ratio increases as the torque becomes larger.

[0062] As described above, the synchronous reluctance motor according to the first embodiment includes an annular stator core having a plurality of slots arranged at equal intervals along its inner circumferential surface, windings housed in each slot, and a cylindrical rotor core formed on the inner surface of the stator core. The rotor core has a plurality of slits, each of which is convex toward the center of the cylinder when viewed in the direction of the central axis of the cylinder, with its center located on the q axis of the magnetic pole and having an opening formed by two arcs with two different radii, and the openings separated by a center rib. A group of slits, each of which is formed in layers toward the center of the cylinder for each magnetic pole, is formed. The slit spacing is defined as the angle formed between adjacent slits and the center of the rotor core by the center point, which is the midpoint in the circumferential direction of the arc-shaped end of the arc-shaped opening of the slit closest to the outer periphery of the rotor core. The slot spacing is defined as the angle formed between adjacent slots in the stator core. The slit spacing is defined to be smaller than the slot spacing. The rotor core has at least three layers of slit groups, and at least two of the three layers of slit groups have side ribs that further divide the slits separated by the center rib. In the synchronous reluctance motor configured as described above, when the multiple slit groups are viewed from the q-axis side to the d-axis side, the average magnetic path width on the q-axis side of the layer on which the side ribs are first formed is larger than the average magnetic path width on the d-axis side of the layer on which the side ribs are first formed. This configuration can increase the torque stress ratio compared to when the average magnetic path width on the q-axis side of the layer on which the side ribs are first formed is equal to or smaller than the average magnetic path width on the d-axis side of the layer on which the side ribs are first formed. This can prevent a decrease in maximum torque while maintaining the centrifugal force resistance of the rotor core.

[0063] Furthermore, in the synchronous reluctance motor according to the first embodiment, when the stator core has nine slots per magnetic pole, the rotor core can have a structure having six layers of slit groups, numbered from the first layer to the sixth layer, in order from the q-axis side. Of these six layers of slit groups, the layer on which side ribs are first provided may be the fifth layer, the fourth layer, or the third layer. In either structure, if the average magnetic path width on the q-axis side of the layer on which side ribs are first provided is made larger than the average magnetic path width on the d-axis side of the layer on which side ribs are first provided, it is possible to suppress a decrease in maximum torque while maintaining the centrifugal force resistance strength of the rotor core.

[0064] Second Embodiment In the first embodiment, a 6-pole, 54-slot synchronous reluctance motor was described, but in the second embodiment, a synchronous reluctance motor of another structure that can obtain the effects described in the first embodiment will be described.

[0065] Fig. 19 is a cross-sectional view showing one magnetic pole of a 6-pole, 36-slot synchronous reluctance motor 1 according to embodiment 2. As shown in Fig. 19, the stator 6 of the 6-pole, 36-slot synchronous reluctance motor 1 has six slots 14 per magnetic pole.

[0066] As in the case of FIG. 4 , the slits 15 are arranged so that the angle θ formed between adjacent slits and the center point W of the opening of the slit 15 along the outer peripheral surface of the rotor core 11 is equal to the distance between adjacent slits. The angle formed between the d axis and a line connecting the center point W of the slit 15 closest to the d axis and the cylindrical center O of the rotor core 11 is set to θ / 2. Specifically, in the configuration of FIG. 4 , the pitch number is 54, and the slit spacing θ is set to θ = 6.67 (= 360 / 54) degrees. Furthermore, in the structure of FIG. 19 , the number of slots S = 36, and the slot spacing δ is δ = 10.0 (= 360 / 36) degrees. Therefore, in the structure of FIG. 19 , the relationship θ < δ holds, as in FIG. 4 .

[0067] 19 has three layers of slit groups, from the first layer to the third layer, in order from the q-axis side. No side ribs 18b are formed in the slits 15 in the first layer, but side ribs 18b are formed in the slit groups in the second and third layers. That is, the layer on which side ribs 18b are first provided is the second layer, and side ribs 18b are provided in the slit groups in the second and third layers. Although not shown to avoid complexity, the magnetic material portions between the layers form magnetic paths through which magnetic flux flows, and the average magnetic path width between the slit groups in the first layer and the slit groups in the second layer is W ｔ１－２ and the average magnetic path width between the slit group in the second layer and the slit group in the third layer is W ｔ２－３ It is expressed as:

[0068] Next, the results of an electromagnetic field analysis performed on rotor core 11 according to the second embodiment using the finite element method will be described. ｔ１－２ , W ｔ２－３ 20 is a diagram illustrating the relationship between the magnitude relationship of the ratio W and the torque stress ratio. ｔ１－２ / W ｔ２－３ The vertical axis of FIG. 20 represents the ratio W ｔ１－２ / W ｔ２－３ The torque stress ratio (maximum torque / stress) when the ratio W ｔ１－２ / W ｔ２－３ The torque stress ratio is expressed as a normalized value when the ratio W is 1. ｔ１－２ / W ｔ２－３ When the ratio W is 0.91, ｔ１－２ / W ｔ２－３ When the torque stress ratio is 1, the torque stress ratio is larger. ｔ１－２ / W ｔ２－３ is 1, the ratio W ｔ１－２ / W ｔ２－３ It is shown that the torque stress ratio is larger when the torque stress ratio is 1.18.

[0069] 19, the torque stress ratio can be improved by making the average magnetic path width on the q-axis side of the layer on which side ribs 18b are first provided larger than the average magnetic path width on the d-axis side. This allows the synchronous reluctance motor 1 according to embodiment 2 to achieve the same effect as embodiment 1, that is, to suppress a decrease in maximum torque while maintaining the centrifugal force resistance strength of the rotor core.

[0070] The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, or different embodiments may be combined with each other. It is also possible to omit or modify parts of the configurations as long as they do not deviate from the gist of the invention.

[0071] 1 Synchronous reluctance motor, 2 Power supply line, 3 Control device, 4 Shaft, 5 Frame, 6 Stator, 7 Rotor, 8 Bearing, 9 Stator core, 10 Winding, 11 Rotor core, 12 Core back, 13 Teeth, 14 Slot, 15 Slit, 18a Center rib, 18b Side rib, 19 Magnetic gap

Claims

1. a stator core having an annular shape and a plurality of slots arranged at equal intervals along an inner circumferential surface thereof; a winding housed in each of the slots; and a rotor core which is cylindrically shaped on the inner surface of the stator core, which is convex toward the center of the cylinder for each magnetic pole when viewed in the direction of the central axis of the cylinder, has an opening formed by two arcs with two radii of different lengths, the opening having a plurality of slits separated by a center rib provided on the q axis, and a slit group consisting of the plurality of slits formed in layers toward the center of the cylinder for each magnetic pole; Equipped with when a slit interval is an angle formed between adjacent slits by a center point that is a midpoint in the circumferential direction of an end of an arc-shaped opening of the slit closest to the outer periphery of the rotor core along the outer periphery of the rotor core, and a cylindrical center of the rotor core, and when a slot interval is an angle formed between adjacent slots in the stator core, the slit interval is smaller than the slot interval, At least three layers of slit groups are formed in the rotor core, and at least two layers of the at least three layers of slit groups are provided with side ribs that further divide the slits divided by the center rib, When the plurality of slit groups are viewed from the q-axis side to the d-axis side, the average magnetic path width on the q-axis side of the layer on which the side ribs are first provided is larger than the average magnetic path width on the d-axis side of the layer on which the side ribs are first provided. A synchronous reluctance motor comprising:

2. the rotor core has six layers of slit groups, namely, a first layer to a sixth layer, in order from the q-axis side, The layer on which the side ribs are first provided is the fifth layer, and the side ribs are provided in the slit groups of the fifth layer and the sixth layer.

2. A synchronous reluctance motor according to claim 1.

3. the rotor core has six layers of slit groups, namely, a first layer to a sixth layer, in order from the q-axis side, The layer on which the side ribs are first provided is the fourth layer, and the side ribs are provided in the slit groups from the fourth layer to the sixth layer.

2. A synchronous reluctance motor according to claim 1.

4. the rotor core has six layers of slit groups, namely, a first layer to a sixth layer, in order from the q-axis side, The layer on which the side ribs are first provided is the third layer, and the side ribs are provided on the slit groups from the third layer to the sixth layer.

2. A synchronous reluctance motor according to claim 1.

5. The number of slots per magnetic pole in the stator core is 9.

2. A synchronous reluctance motor according to claim 1.

6. the rotor core has three layers of slit groups, namely, first to third layers, in order from the q-axis side, The layer on which the side ribs are first provided is the second layer, and the side ribs are provided in the slit groups of the second layer and the third layer.

2. A synchronous reluctance motor according to claim 1.

7. The number of slots per magnetic pole in the stator core is six.

7. A synchronous reluctance motor according to claim 6.

8. A driving device for a railway vehicle, comprising the synchronous reluctance motor according to any one of claims 1 to 7.