DESCRIPTION
FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
SYNCHRONOUS RELUCTANCE MOTOR;
MITSUBISHI ELECTRIC CORPORATION, A CORPORATION ORGANISED AND
EXISTING UNDER THE LAWS OF JAPAN, WHOSE ADDRESS IS 7-3,
MARUNOUCHI 2-CHOME, CHIYODA-KU, TOKYO 100-8310, JAPAN
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE
INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.
2
DESCRIPTION
Title of Invention
SYNCHRONOUS RELUCTANCE MOTOR
5 Technical Field
[0001] The present disclosure relates to a synchronous reluctance motor.
Background Art
[0002] Motors are used for various purposes, for example, for the purpose of
generating a propulsive force of a railway vehicle. Motors installed in a railway vehicle
10 are preferably highly efficient so that a small number of motors can generate a target
propulsive force, because of the limited space under the floor of the railway vehicle.
One example of the motors to be installed in an electric railway vehicle is synchronous
motors having higher efficiency than induction motors. As one type of the synchronous
motors, a typical synchronous reluctance motor is disclosed in Patent Literature 1.
15 [0003] The synchronous reluctance motor disclosed in Patent Literature 1 includes
a rotor and a stator radially opposing the rotor with a space therebetween. The rotor is
fabricated by stacking circular magnetic steel sheets having slits arranged in the
circumferential direction, for example. Each of the slits has a curved shape convex
toward the center of the circular shape. Since through holes are formed, the rotor has
20 various magnetic resistances depending on positions in the circumferential direction.
The rotor thus has multiple salient poles, which indicate portions each having a low
magnetic resistance. The salient poles of the rotor are attracted to stator coils disposed
in slots provided in the stator in response to energization of the stator coils, resulting in
rotation of the rotor.
25 Citation List
Patent Literature
[0004] Patent Literature 1: Unexamined Japanese Patent Application Publication
3
No. 2002-199675
Summary of Invention
Technical Problem
[0005] Although a synchronous reluctance motor has higher efficiency than an
5 induction motor, the efficiency of the synchronous reluctance motor needs to be further
improved in order to generate the target propulsive force of the railway vehicle with a
much smaller number of motors, for example. The efficiency of the synchronous
reluctance motor can be improved by increasing the current flowing in the stator coils,
increasing the number of the slots of the stator to narrow the circumferential intervals of
10 the stator coils, or narrowing the space between the stator and the rotor, for example.
[0006] An excessively high current flowing in the stator coils unintentionally raises
the temperature inside the synchronous reluctance motor. Thus, a cooling capacity of
the synchronous reluctance motor needs to be improved. When the cooling capacity is
improved by increasing the size of a fan, for example, the synchronous reluctance motor
15 accordingly becomes larger. In contrast, narrowed circumferential intervals of the stator
coils or a narrowed space between the stator and the rotor increases the variation of
magnetic permeance of the stator, leading to an expansion of the amplitude of harmonic
magnetic flux generated in the stator. Such an expansion of the amplitude causes
increases in torque ripple, electromagnetic excitation force, and harmonic loss. These
20 problems are not peculiar to synchronous reluctance motors installed in railway vehicles
but common to general synchronous reluctance motors intended to have higher
efficiencies.
[0007] An objective of the present disclosure, which has been accomplished in
view of the above situations, is to provide a highly efficient synchronous reluctance
25 motor that can suppress increases in coil current and in variation of magnetic permeance.
Solution to Problem
[0008] In order to achieve the above objective, a synchronous reluctance motor
4
according to an aspect of the present disclosure includes a shaft, a rotor, a stator, and
multiple magnetic wedges. The shaft is supported rotatably around the rotation axis.
The rotor is located radially outward from the shaft and rotatable integrally with the shaft,
and has a plurality of salient poles. The stator includes a stator core radially opposing
5 the rotor with a space therebetween and including a plurality of slots arranged in the
circumferential direction around the rotation axis and open toward the rotor, and a
plurality of stator coils disposed in the plurality of slots. A plurality of magnetic wedges
close at least some of the plurality of slots with the plurality of stator coils disposed
therein.
10 Advantageous Effects of Invention
[0009] The synchronous reluctance motor according to an aspect of the present
disclosure includes the magnetic wedges to close at least some of the slots provided in the
stator while the stator coils are disposed in the slots. The magnetic wedges closing the
slots can suppress an increase in variation of magnetic permeance of the stator even when
15 the efficiency is improved by narrowing the circumferential intervals of the stator coils or
narrowing the space between the stator and the rotor while maintaining the magnitude of
the current flowing in the stator coils. This structure can provide a highly efficient
synchronous reluctance motor that can suppress increases in coil current and in variation
of magnetic permeance.
20 Brief Description of Drawings
[0010] FIG. 1 is a sectional view of a synchronous reluctance motor according to
Embodiment 1;
FIG. 2 is a sectional view of the synchronous reluctance motor according to
Embodiment 1 taken along the line II-II of FIG. 1;
25 FIG. 3 is a partially enlarged view of the synchronous reluctance motor according
to Embodiment 1;
FIG. 4 illustrates an exemplary relationship between a thickness of magnetic
5
wedges and a loss in a rotor according to Embodiment 1;
FIG. 5 is a sectional view of a synchronous reluctance motor according to
Embodiment 2;
FIG. 6 is a sectional view of a modified synchronous reluctance motor according
5 to the embodiments; and
FIG. 7 illustrates an exemplary relationship between a loss and a ratio of the
number of magnetic wedges to the number of slots in a synchronous reluctance motor
according to the embodiments.
Description of Embodiments
10 [0011] A synchronous reluctance motor according to embodiments of the present
disclosure is described in detail below with reference to the accompanying drawings. In
the drawings, the components identical or corresponding to each other are provided with
the same reference symbol.
[0012] Embodiment 1
15 The following description is directed to a synchronous reluctance motor 1
according to Embodiment 1, which is a synchronous reluctance motor for driving a
railway vehicle. The synchronous reluctance motor 1 illustrated in FIG. 1 is installed
under the floor of the railway vehicle. In FIG. 1, the Z-axis direction indicates the
vertical direction when the railway vehicle is in a horizontal state. The Y-axis direction
20 indicates the width direction of the railway vehicle. The X-axis direction indicates the
traveling direction of the railway vehicle. In other words, the railway vehicle travels
toward the positive side in the X-axis direction or the negative side in the X-axis
direction. The X, Y, and Z axes are orthogonal to each other.
[0013] The synchronous reluctance motor 1 includes a shaft 11 supported rotatably
25 around a rotation axis AX represented with the dashed and single-dotted line in FIG. 1, a
rotor 12 located radially outward from the shaft 11 and rotatable integrally with the shaft
11, a stator 13 radially opposing the rotor 12 with a space 30 therebetween, and bearings
6
14 and 15 to support the shaft 11 rotatably. The synchronous reluctance motor 1 further
includes a frame 16 to accommodate the rotor 12, the stator 13, and the bearings 14 and
15 while the shaft 11 is inserted therethrough, and a first bracket 17 and a second bracket
18 to hold the frame 16 therebetween in the direction of extension of the rotation axis
5 AX. As illustrated in FIG. 2, which is a sectional view taken along the line II-II of FIG.
1, the synchronous reluctance motor 1 further includes magnetic wedges 19 to close slots
33a provided in the stator 13.
[0014] The components of the synchronous reluctance motor 1 are described in
detail below.
10 The end of the shaft 11 adjacent to the second bracket 18 illustrated in FIG. 1 is
coupled to the axle of the railway vehicle via joints and gears, which are not illustrated.
The rotation of the shaft 11 causes generation of a propulsive force of the railway vehicle.
[0015] The rotor 12 includes a rotor core 31 provided to the shaft 11, and a pair of
holding members 32 to hold the rotor core 31 therebetween in the direction of extension
15 of the rotation axis AX and thereby stabilize the rotor core 31. As illustrated in FIG. 2,
the rotor core 31 has multiple salient poles 31a. The salient pole indicates a portion of
the rotor core 31 having a lower magnetic resistance than the other portions and guiding
the magnetic flux generated in response to energization of the stator 13 to the inside.
[0016] As illustrated in FIGS. 1 and 2, the rotor core 31 has multiple slits 31b
20 arranged in the circumference direction in Embodiment 1. Each of the slits 31b extends
through the rotor core 31 in the direction of extension of the rotation axis AX and has a
curved shape convex toward the radial center. Specifically, six slits 31b are arranged in
the circumferential direction around the rotation axis AX, and four slits 31b are radially
arranged. A slit 31b located on a radially inner side has a circumferential length shorter
25 than that of a slit 31b located on a radially outer side. The salient poles 31a are formed
in the vicinity of the ends of the slits 31b from which the slits 31b extend radially inward,
specifically, in the vicinity of the portions in which two slits 31b are adjacent to each
7
other in the circumferential direction. In other words, the salient poles 31a are formed at
positions located between two slits 31b adjacent to each other in the circumferential
direction. The rotor 12 has six salient poles 31a because six slits 31b are arranged in the
circumference direction. In other words, the number of poles of the rotor 12 is six.
5 Since four slits 31b are radially arranged, the radial spaces between the slits 31b define
magnetic paths 31c for connecting two adjacent salient poles 31a to each other.
[0017] The rotor core 31 is fabricated by stacking magnetic steel sheets having a
disc shape, for example. Each of the magnetic steel sheets has multiple through holes
corresponding to the slits 31b illustrated in FIG. 2 and a through hole to receive the shaft
10 11. In detail, the magnetic steel sheet has multiple through holes having a curved shape
convex toward the center of the disc shape, and a circular through hole located at the
center. In a stack of the magnetic steel sheets, the curved through holes of the magnetic
steel sheets constitute the slits 31b.
[0018] The pair of holding members 32 illustrated in FIG. 1 are plate members
15 having an annular section in a plane orthogonal to the direction of extension of the
rotation axis AX. The pair of holding members 32 hold the rotor core 31 therebetween
and thereby suppress the magnetic steel sheets of the rotor core 31 from being displaced
from each other in the circumferential direction.
[0019] The stator 13 includes a stator core 33 provided to the inner periphery of the
20 frame 16, and multiple stator coils 34 inserted in the respective slots 33a provided in the
stator core 33. The stator core 33 radially opposes the rotor core 31 to define the space
30 therebetween. As illustrated in FIG. 2, the stator core 33 has the slots 33a extending
in the direction of extension of the rotation axis AX. The stator core 33 is fabricated by
stacking magnetic steel sheets that have an annular shape and include notches
25 corresponding to the slots 33a, for example.
[0020] The slots 33a are open toward the rotor 12. For example, the slots 33a are
grooves extending through the stator core 33 in the direction of extension of the rotation
8
axis AX, open radially inward, and having a rectangular section in a plane orthogonal to
the rotation axis AX. In Embodiment 1, thirty-six slots 33a are provided at regular
intervals in the circumferential direction. The slots 33a receive the respective stator
coils 34.
5 [0021] The stator coils 34 disposed in the above-described slots 33a are fed with
three-phase AC current from the outside via a lead wire, which is not illustrated.
[0022] At least some of the slots 33a are provided with the magnetic wedges 19 to
close the slots 33a while the stator coils 34 are disposed in the slots 33a. The magnetic
wedges 19 have an appropriate shape and are made of an appropriate material so that the
10 magnetic wedges 19 can avoid an increase in variation of magnetic permeance while
closing the slots 33a and thus preventing the stator coils 34 from falling off. For
example, the magnetic wedges 19 are made of plates of a ferromagnetic material,
specifically, iron plates, or plates of the same material as the magnetic steel sheets of the
stator core 33. The magnetic wedges 19 preferably have an appropriate radial thickness
15 so that the magnetic wedges 19 reduce the variation of magnetic permeance caused by
the existence of the slots 33a, for example, a thickness of at least the half of the radial
length of the space 30. Specifically, the radial thickness of the magnetic wedges 19 is
preferably at least one millimeter and at most four millimeters. Preferably, the magnetic
wedges 19 each have a curved shape convex radially outward, and the inner peripheries
20 of the magnetic wedges 19 are located on the same curved surface as the inner periphery
of the stator core 33.
[0023] In Embodiment 1, the openings of all the slots 33a are closed by the
magnetic wedges 19. For example, the magnetic wedges 19 fit in the openings of the
respective slots 33a. The structure in which the openings of the slots 33a are closed by
25 the magnetic wedges 19 can reduce the variation of magnetic resistance of the inner
periphery of the stator 13 in comparison to that in the structure in which the openings of
the respective slots 33a are not closed. The above-described structure can thus reduce
9
the variation of magnetic permeance of the stator 13. In addition, the magnetic wedges
19 fitting in the openings of the respective slots 33a can prevent the stator coils 34
disposed in the respective slots 33a from falling off.
[0024] In Embodiment 1, the magnetic wedges 19 have a shape of thin plate. The
5 shape of the magnetic wedges 19 can be determined depending on the shape of the
openings of the slots 33a, and the amplitude of harmonic magnetic flux generated in the
stator 13 in the case of absence of the magnetic wedges 19. In detail, the magnetic
wedges 19 may have a shape that can tightly fit in the openings of the slots 33a so as not
to fall off from the openings of the slots 33a. For example, the magnetic wedges 19
10 may have a shape of thin plate of which the radially outer surface has a circumferential
width equal to the circumferential width of the openings of the slots 33a. Furthermore,
the magnetic wedges 19 may have a shape of thin plate having an appropriate radial
thickness so that the magnetic wedges 19 can suppress an expansion of the amplitude of
harmonic magnetic flux, in order to attenuate the torque ripple, electromagnetic excitation
15 force, and harmonic loss, which can be generated by the amplitude of harmonic magnetic
flux, to allowable levels.
[0025] The bearing 14 is retained at the first bracket 17 and supports the shaft 11
rotatably.
The bearing 15 is retained at the second bracket 18 and supports the shaft 11
20 rotatably.
The frame 16 is fixed under the floor of the railway vehicle with fixing members,
which are not illustrated. The frame 16 has a hollow cylindrical shape. In
Embodiment 1, the frame 16 has a hollow cylindrical shape having openings at both
ends, which are closed by the first bracket 17 and the second bracket 18.
25 [0026] The following description is directed to a variation of loss in the rotor 12
depending on the shape of the magnetic wedges 19 in the synchronous reluctance motor 1
having the above-described structure. As illustrated in FIG. 3, which is a partially
10
enlarged view of FIG. 2, W1 indicates the radial thickness of the magnetic wedges 19,
and G1 indicates the radial length of the space 30. As illustrated in FIG. 4, the loss in
the rotor 12 varies in accordance with a change in the ratio of the radial thickness W1 of
the magnetic wedges 19 to the radial length G1 of the space 30.
5 [0027] The horizontal axis in FIG. 4 indicates a ratio of the radial thickness W1 of
the magnetic wedges 19 to the radial length G1 of the space 30, that is, a value obtained
by dividing the radial thickness W1 of the magnetic wedges 19 by the radial length G1 of
the space 30. The horizontal value of 0 in FIG. 4 corresponds to a synchronous
reluctance motor of which the slots of the stator are not closed by magnetic wedges.
10 The horizontal value of 1 in FIG. 4 corresponds to a structure in which the radial length
G1 of the space 30 is equal to the radial thickness W1 of the magnetic wedges 19.
[0028] The vertical axis in FIG. 4 indicates a loss in the rotor 12. In detail, the
vertical axis in FIG. 4 indicates a level of loss in the rotor 12 when the loss in the rotor 12
is defined as 1 in the structure in which the radial length G1 of the space 30 is equal to the
15 radial thickness W1 of the magnetic wedges 19. As illustrated in FIG. 4, the loss in the
rotor 12 can be reduced by increasing the ratio of the radial thickness W1 of the magnetic
wedges 19 to the radial length G1 of the space 30. A reduction in the loss in the rotor 12
leads to a reduction in the amount of heat generated from the rotor 12. This structure
can thus suppress temperature rises in the bearings 14 and 15 that rotatably support the
20 shaft 11 to which the rotor 12 is provided. In other words, the structure can increase the
output from the synchronous reluctance motor 1 while maintaining the temperatures of
the bearings 14 and 15 at an allowable temperature or lower.
[0029] As described above, the slots 33a provided in the stator core 33 of the stator
13 included in the synchronous reluctance motor 1 according to Embodiment 1 are closed
25 by the magnetic wedges 19. The magnetic wedges 19 made of a ferromagnetic material
close the openings of the slots 33a and can thereby reduce the variation of magnetic
resistance of the inner periphery of the stator 13. This structure can thus reduce the
11
variation of magnetic permeance of the stator 13, leading to decreases in torque ripple,
electromagnetic excitation force, and harmonic loss.
[0030] In other words, since the synchronous reluctance motor 1 can reduce the
variation of magnetic permeance by means of the magnetic wedges 19 closing the slots
5 33a of the stator core 33, the synchronous reluctance motor 1 can achieve a narrower
space 30 between the rotor 12 and the stator 13 while maintaining the variation of
magnetic permeance at the same level, in comparison to a synchronous reluctance motor
in which the slots of the stator are not closed. For example, the space 30 has a radial
length shorter than ten millimeters, specifically, a radial length of two millimeters. The
10 space 30 between the rotor 12 and the stator 13 having a narrower width can facilitate
rotation of the rotor 12 and improve the efficiency of the synchronous reluctance motor 1.
[0031] In addition, the synchronous reluctance motor 1 can achieve an increased
number of slots 33a and narrower circumferential intervals of the stator coils 34, while
maintaining the variation of magnetic permeance at the same level, in comparison to a
15 synchronous reluctance motor in which the slots of the stator are not closed by magnetic
wedges. The narrower circumferential intervals of the stator coils 34 can facilitate
rotation of the rotor 12 and improve the efficiency of the synchronous reluctance motor 1.
[0032] The efficiency of the synchronous reluctance motor 1 can thus be improved
by narrowing the space 30 between the rotor 12 and the stator 13 or narrowing the
20 circumferential intervals of the stator coils 34, as described above, without increasing the
current flowing in the stator coils 34. In other words, by means of the magnetic wedges
19 closing the slots 33a of the stator core 33, the highly efficient synchronous reluctance
motor 1 can suppress an increase in the current flowing in the stator coils 34 and an
increase in the variation of magnetic permeance.
25 [0033] Embodiment 2
Although the openings of all the slots 33a are closed by the magnetic wedges 19 in
the synchronous reluctance motor 1 according to Embodiment 1, the number of the
12
magnetic wedges 19 may be smaller than the number of the slots 33a. The description
of Embodiment 2 is directed to a synchronous reluctance motor in which the number of
the magnetic wedges 19 is smaller than the number of the slots 33a.
[0034] As illustrated in FIG. 5, a synchronous reluctance motor 2 according to
5 Embodiment 2 further includes non-magnetic wedges 20 to close the slots 33a other than
the slots 33a closed by the magnetic wedges 19, in addition to the components of the
synchronous reluctance motor 1 according to Embodiment 1. FIG. 5 is a sectional view
of the synchronous reluctance motor 2 in the same section as in FIG. 2. The nonmagnetic wedges 20 are made of a non-magnetic material, specifically, a material of
10 which the relative magnetic permeability can be regarded as 1, for example, aluminum.
The non-magnetic wedges 20 preferably have the same shape as the magnetic wedges 19.
[0035] The number of the magnetic wedges 19 included in the synchronous
reluctance motor 2 is smaller than the number of the slots 33a, and is equal to a multiple
of the product of the number of poles of the rotor 12 and the number of phases of the
15 stator 13. In detail, the ratio of the number of the magnetic wedges 19 to the number of
the slots 33a can be represented by k/n, where n indicates the number of slots per phase
per pole obtained by dividing the number of the slots 33a by the product of the number of
poles of the rotor 12 and the number of phases of the stator 13. The coefficient k is a
natural number equal to or smaller than n. In Embodiment 2, since the number of poles
20 of the rotor 12 is six and the number of the slots 33a is 36, the number of slots per phase
per pole n is equal to 2 in the case where three-phase AC current is fed to the stator coils
34. In Embodiment 2, the coefficient k is defined as 1. As illustrated in FIG. 5, the
magnetic wedges 19 and the non-magnetic wedges 20 are preferably arranged alternately
in the circumferential direction.
25 [0036] As described above, some of the slots 33a are closed by the magnetic
wedges 19, and the others of the slots 33a are closed by the non-magnetic wedges 20 in
the synchronous reluctance motor 2. By means of the magnetic wedges 19 closing the
13
slots 33a of the stator core 33, the highly efficient synchronous reluctance motor 2 can
suppress an increase in the current flowing in the stator coils 34 and an increase in the
variation of magnetic permeance. Such a combination of the magnetic wedges 19 and
the non-magnetic wedges 20 less expensive than the magnetic wedges 19 can reduce the
5 manufacturing costs of the synchronous reluctance motor 2.
[0037] The above-described embodiments are not intended to limit the scope of the
present disclosure. The rotor core 31 has any shape provided that the rotor 12 can
achieve multiple salient poles 31a. For example, the rotor core 31 does not necessarily
have an annular section in a plane orthogonal to the direction of extension of the rotation
10 axis AX. Specifically, as in a synchronous reluctance motor 3 illustrated in FIG. 6, the
rotor core 31 may have multiple protrusions 31d that are arranged in the circumferential
direction on the outer peripheral surface and protruding radially outward. The salient
poles 31a are formed at the protrusions 31d. The rotor core 31 of the rotor 12 included
in the synchronous reluctance motor 3 is fabricated by preparing multiple through holes
15 in magnetic steel sheets having circular disc shapes such that each of the through holes
has a curved shape convex toward the center of the disc shape, preparing notches at the
outer edges of the disc shapes such that each of the notches has a curved shape convex
toward the center of the disc shape, and then stacking the magnetic steel sheets on each
other, for example.
20 [0038] The rotor core 31 of the rotor 12 included in the synchronous reluctance
motor 3 may have the protrusions 31d alone without the slits 31b. In this case, the
protrusions 31d can also define the salient poles 31a of the rotor 12.
[0039] The above-mentioned number of poles of the rotor 12 is a mere example.
The number of poles is not necessarily six and may be any even number. For example,
25 the rotor core 31 may include four slits 31b in the circumferential direction and four slits
31b in the radial direction. The number of poles of the rotor 12 is four in this case.
[0040] In a case where the number of poles of the rotor 12 is four, the number of
14
the slots 33a is 36, and three-phase AC current is fed to the stator coils 34, the number of
slots per phase per pole n is three. The ratio of the number of the magnetic wedges 19
to the number of the slots 33a is not necessarily 1 or 1/2 as in the above-described
embodiments. For example, the ratio of the number of the magnetic wedges 19 to the
5 number of the slots 33a may also be 1/3. In other words, k=1 may be applied to the
expression k/n, which represents the ratio of the number of the magnetic wedges 19 to the
number of the slots 33a. In this case, twelve magnetic wedges 19, corresponding to the
one-third of 36, are disposed at regular intervals in the circumferential direction.
Specifically, one magnetic wedge 19 and a unit of two adjacent non-magnetic wedges 20
10 are arranged alternately in the circumferential direction.
[0041] The ratio of the number of the magnetic wedges 19 to the number of the
slots 33a in the synchronous reluctance motor 2 may also be 2/3. In this case, twentyfour magnetic wedges 19, corresponding to the two-thirds of 36, are disposed such that
two adjacent magnetic wedges 19 are arranged at regular intervals in the circumferential
15 direction. Specifically, a unit of two adjacent magnetic wedges 19 and one nonmagnetic wedge 20 are disposed alternately in the circumferential direction.
[0042] FIG. 7 illustrates a variation of loss in the synchronous reluctance motor 1 or
2 in accordance with a change in the ratio of the number of the magnetic wedges 19 to the
number of the slots 33a in the case where the number of slots per phase per pole n is
20 three. The horizontal axis in FIG. 7 indicates a ratio (k/n) of the number of the magnetic
wedges 19 to the number of the slots 33a. The horizontal value of 0 in FIG. 7
corresponds to a synchronous reluctance motor in which the slots of the stator are not
closed by magnetic wedges. The horizontal value larger than 0 and smaller than 1 in
FIG. 7 corresponds to the synchronous reluctance motor 2 including the magnetic wedges
25 19 to close some of the slots 33a. The horizontal value of 1 in FIG. 7 corresponds to the
synchronous reluctance motor 1 including the magnetic wedges 19 to close all the slots
33a.
15
[0043] The vertical axis in FIG. 7 indicates a loss in the synchronous reluctance
motor 1 or 2. In detail, the vertical axis in FIG. 7 indicates a level of loss in the
synchronous reluctance motor 1 or 2 when the loss in a synchronous reluctance motor in
which the slots of the stator are not closed by magnetic wedges is defined as 1. As
5 illustrated in FIG. 7, the synchronous reluctance motor including the magnetic wedges 19
to close only some of the slots 33a can also reduce the loss, in comparison to a
synchronous reluctance motor in which the slots of the stator are not closed by magnetic
wedges.
[0044] The above-mentioned number of phases of the stator 13 is a mere example.
10 The stator coils 34 may also be fed with two-phase AC current, for example.
[0045] The above-mentioned shape of the slits 31b is a mere example. The slits
31b may have any shape provided that the slits 31b enable the rotor 12 to have the salient
poles 31a.
[0046] The above-mentioned number of the slots 33a is a mere example and may
15 be any even number. For example, the number of slots may be 54.
The above-mentioned shape of the slots 33a is a mere example. The slots 33a
may have any shape provided that the slots 33a can receive the stator coils 34. For
example, the slots 33a may have a shape of which the circumferential width decreases
toward the radial center.
20 [0047] The synchronous reluctance motors 1 to 3 can be applied as not only motors
for generating propulsive forces of railway vehicles, but also general-purpose motors,
such as motors for driving pumps, for example.
The synchronous reluctance motors 1 to 3 can be applied as not only motors of an
inner-rotor type but also motors of an outer-rotor type.
25 [0048] The foregoing describes some example embodiments for explanatory
purposes. Although the foregoing discussion has presented specific embodiments,
persons skilled in the art will recognize that changes may be made in form and detail
16
without departing from the broader spirit and scope of the invention. Accordingly, the
specification and drawings are to be regarded in an illustrative rather than a restrictive
sense. This detailed description, therefore, is not to be taken in a limiting sense, and the
scope of the invention is defined only by the included claims, along with the full range of
5 equivalents to which such claims are entitled.
Reference Signs List
[0049] 1, 2, 3 Synchronous reluctance motor
11 Shaft
12 Rotor
10 13 Stator
14, 15 Bearing
16 Frame
17 First bracket
18 Second bracket
15 19 Magnetic wedge
20 Non-magnetic wedge
30 Space
31 Rotor core
31a Salient pole
20 31b Slit
31c Magnetic path
31d Protrusion
32 Holding member
33 Stator core
25 33a Slot
34 Stator coil
AX Rotation axis
17
We Claim :
[Claim 1] A synchronous reluctance motor comprising:
a shaft supported rotatably around a rotation axis;
a rotor located radially outward from the shaft and rotatable integrally with the
5 shaft, the rotor including a plurality of salient poles;
a stator including
a stator core radially opposing the rotor with a space therebetween, the stator
core including a plurality of slots arranged in a circumferential direction around the
rotation axis, the plurality of slots being open toward the rotor, and
10 a plurality of stator coils disposed in the plurality of slots; and
a plurality of magnetic wedges to close at least some of the plurality of slots with
the plurality of stator coils disposed therein.
[Claim 2] The synchronous reluctance motor according to claim 1, wherein a
15 number of the plurality of magnetic wedges is equal to a number of the plurality of slots.
[Claim 3] The synchronous reluctance motor according to claim 1, wherein a
number of the plurality of magnetic wedges is equal to a multiple of a product of a
number of poles of the rotor and a number of phases of the stator, and is smaller than a
20 number of the plurality of slots.
[Claim 4] The synchronous reluctance motor according to claim 3, wherein the
plurality of magnetic wedges are disposed at regular intervals in the circumferential
direction.
25
[Claim 5] The synchronous reluctance motor according to claim 3, wherein
units of the plurality of magnetic wedges are disposed at regular intervals in the
18
circumferential direction, each of the units including two or more magnetic wedges
adjacent to each other.
[Claim 6] The synchronous reluctance motor according to any one of claims 3
5 to 5, further comprising a non-magnetic wedge to close a slot of the plurality of slots
other than the at least some slots closed by the magnetic wedges while the plurality of
stator coils are disposed in the plurality of slots.
[Claim 7] The synchronous reluctance motor according to any one of claims 1
10 to 6, wherein a radial thickness of the plurality of magnetic wedges is larger than a radial
length of the space between the stator and the rotor.
[Claim 8] The synchronous reluctance motor according to any one of claims 1
to 7, wherein
15 the rotor includes a plurality of slits arranged in the circumferential direction, each
of the plurality of slits extending through the rotor in an extending direction of the
rotation axis and having a curved shape convex toward a radial center, and
the plurality of salient poles are formed at positions located between slits adjacent
to each other in the circumferential direction.
20

19
[Claim 9] The synchronous reluctance motor according to any one of claims 1
to 8, wherein
the rotor includes a plurality of protrusions arranged in the circumferential
direction on an outer peripheral surface, each of the plurality of protrusions protruding
5 radially outward, and
the plurality of salient poles are formed at the plurality of protrusions.