JP2002209368A - Motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high output and small sized motor which is applied to an air conditioner, refrigerator, a electric vehicle, etc. SOLUTION: This motor has a stator core having a plurality of teeth 7, concentrated windings applied to the teeth 7, and a rotor 3 in which a plurality of low permeability parts, which are hollow parts, are provided and, is driven to rotate by using reluctance torque. As the concentrated windings are applied to the teeth 7, the windings do not significantly protrude to the end of the stator, so that the dimension of the coil end can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a synchronous motor having a stator for generating a rotating magnetic field and driven to rotate using reluctance torque.

[0002]

2. Description of the Related Art In a conventional general synchronous motor, a stator has a plurality of teeth integrally protruding from a ring-shaped yoke to an inner peripheral side thereof. This stator is formed by stacking stator plates having a plurality of teeth protruding inward. In addition, these have a stator core having a slot formed between the teeth,
A winding is wound around the slot by distributed winding. The distributed winding is a winding method of winding a teeth portion separated through a slot portion. The rotor has a configuration in which a plurality of permanent magnets for magnetic poles are embedded in the outer peripheral portion of the rotor core, and a rotating shaft is fitted in the central portion.

As described above, by embedding the permanent magnet in the rotor, the permanent magnet embedded motor capable of utilizing the reluctance torque in addition to the magnet torque can be used in a direction connecting the center of the permanent magnet and the center of the rotor. A d
The inductance Ld in the axial direction and the inductance L in the q-axis direction which is a direction rotated by 90 electrical degrees with respect to the d-axis.
An inductance difference occurs in d, so that reluctance torque is generated in addition to the magnet torque generated by the permanent magnet. Equation (1) shows this relationship. T = Pn [ψa × Iq + ／ (Ld−Lq) × Id × Iq] ‥‥ (1) Pn: Number of pole pairs ψa: Linkage magnetic flux Ld: d-axis inductance Lq: q-axis inductance Iq: q-axis current Id: d-axis current Equation (1) shows a voltage equation for dq conversion. For example, in a surface magnet motor, since the magnetic permeability of the permanent magnet is almost equal to that of air, both inductances Ld and Ld of the above equation (1) are obtained.
q has substantially the same value, and the reluctance torque component shown in the second term in [] of equation (1) does not occur.

When an attempt is made to increase the torque of a motor driven by using reluctance torque in addition to magnet torque, the difference (Ld-Lq) may be increased according to equation (1). Since the inductance L, which is the ease of passing the magnetic flux, is proportional to N ² (the number of turns of the teeth), if the number of turns around the teeth is increased, the difference (Ld−Lq) increases, and the reluctance torque can be increased. it can. However, if the number of turns is increased in order to increase the use of reluctance torque, as the number of turns increases, the number of windings projecting from the end face of the stator, that is, the coil end, increases. Therefore, if the reluctance torque is used to efficiently drive the motor to rotate, the coil end becomes large, and the motor itself becomes large.

[0005] In the distributed winding, a winding wheel is formed by winding a plurality of windings, and the winding wheel is inserted into a tooth, and the circumference of the winding wheel becomes larger than the tooth circumference. Further, in the case of the distributed winding, since the teeth are wound through the slots, the windings cross each other. As described above, in the case of the distributed winding, the windings protrude from the end face of the stator, and the windings cross each other, so that the coil end becomes large. Conversely, if an attempt is made to reduce the size of the motor, the output of the motor will decrease.

[0006] Therefore, if an attempt is made to drive the motor efficiently using the reluctance torque, the size of the motor will be increased. Conversely, if an attempt is made to reduce the size of the motor, the output of the motor will decrease.

[0007]

However, there is a need for a high-output and small-sized electric motor in an air conditioner, a refrigerator, an electric vehicle and the like.

[0008] The magnetic pole portion at the tip of the teeth of the stator is formed wide in the circumferential direction. However, in order to form an opening for applying a winding to the slot portion between the adjacent magnetic pole portions, it is necessary to increase the circumferential width between the tip ends of the teeth. That is, an opening for inserting a winding wheel into a tooth by distributed winding is required. In addition, the gap between the inner circumference of the stator and the outer circumference of the rotor is generally set uniformly over the entire circumference except for the opening of the slot.

In the above-mentioned conventional configuration, since the opening of the slot portion is interposed between the magnetic pole portions on the stator side, the magnetic flux emitted from the magnetic pole portions has a circumferentially disconnected portion, and cogging occurs when the rotor rotates. There was a problem that torque was generated. On the rotor side, the cogging torque can be reduced by making the distribution of the magnetic flux emitted from the outer periphery close to a sinusoidal waveform, but since the gap between the inner periphery of the stator and the outer periphery of the rotor is constant, this gap Is constant over the entire circumference, and the magnetic flux distribution changes abruptly in the portion where the ends of the permanent magnets are adjacent, and the cogging torque increases. As described above, there is a problem in that a large cogging torque is generated due to the cogging torque increase factors on both the stator side and the rotor side overlapping.

[0010]

SUMMARY OF THE INVENTION The present invention comprises a stator core having a plurality of teeth, a winding in which the teeth are wound, and a rotor having a plurality of low magnetic permeability portions. The low-permeability part is an electric motor that is driven to rotate by using a reluctance torque that is a gap or a resin member. Since the winding is wound around the teeth part, the winding largely protrudes from the end face of the stator. And the coil end can be made smaller.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention comprises a stator core having a plurality of teeth, a winding in which the teeth are wound, and a rotor having a plurality of low permeability parts therein. The low-permeability part is an electric motor that is driven to rotate by using a reluctance torque that is a void or a resin member.Since the winding is wound around the teeth part, the winding does not protrude significantly on the stator end face. The size of the coil end can be reduced.

[0012]

(Embodiment 1) FIG. 1 to FIG.
This will be described with reference to FIG. In FIG. 1, reference numeral 1 denotes a synchronous motor that is driven to rotate using reluctance torque in addition to magnet torque, and includes a stator 2, a rotor 3, and a rotating shaft 4. The stator 2 is formed between a ring-shaped frame portion 21, a stator core 22 formed by annularly combining a plurality of independent core elements 5 made of a high magnetic permeability material, and the teeth portions 7 of each core element 5. It is composed of a winding wound around the slot portion 8,
A rotating magnetic field is generated by applying a current to these winding groups.

The stator core 22 is constituted by combining a plurality of core elements 5 in an annular shape at an outer peripheral portion 6 thereof and fittingly fixing the core element 5 to the inner periphery of the frame portion 21. The extension is formed in a fan-shaped overall shape passing through the center of the stator. As shown in detail in FIG. 2, the core element 5 has a slot forming recess 9 formed in an inner peripheral portion thereof, and the slot 8 is formed by the slot forming portions 9 of the adjacent teeth portions 7. Is formed. Further, on both side surfaces 6a, there are provided locking portions 11 each having an engaging projection 10a and an engaging concave portion 10b which are engaged with each other when the core elements 5 are combined in an annular shape, and the core elements 5 are firmly fixed to each other. It is configured to be. The combination of the core elements 5 is performed by welding. However, a fitting portion may be provided on a side surface of the core element 5 and swaged and fixed.

As described above, the stator 2 is formed by combining a plurality of core elements 5. Therefore, the stator 2
After the winding is wound around the core element 5 instead of winding the winding, the stator 2 can be formed. In this manner, if the winding is performed in the state of the core element 5, the winding is wound for each core element 5, so that the single winding (concentrated winding) can be facilitated. This is because, as shown in FIG. 4, when winding the winding 23, there is no portion on the side surface of the tooth portion 7 that hinders the winding. Therefore, the winding opening of the winding device rotates around the teeth portion 7, and can perform aligned winding via the insulating film 24. Further, the winding accuracy of the winding 40 can be increased, and the aligned winding can be easily performed.

As described above, by winding the windings of the stator 2 one by one, it is possible to suppress the intersection of the windings at the stator end face. Therefore, the size of the coil end can be suppressed because the winding does not intersect with the end face in the rotation axis direction of the stator 5. Furthermore, since the winding is performed with the stator divided, the circumference of the teeth 5 and the circumference of the winding can be made equal. Therefore, the winding does not protrude at the stator end face, and the coil end can be reduced.

Further, since the stator 5 is wound in a divided state, it is not necessary to consider the space of the winding opening of the winding device at the time of winding, so that the windings can be overlapped as much as possible. In addition, since the winding is performed in a state where the stator 5 is divided, the accuracy of the winding device is improved, and the aligned winding can be performed. Therefore, the space factor of the slot portion can be increased. Since the reluctance torque is proportional to the number of windings,
By increasing the space factor, the reluctance torque can be increased.

As described above, since the winding around the teeth portion can be wound with an appropriate length, there is no extra winding, and the winding length is reduced with respect to the total number of turns. be able to. Therefore, copper loss can be reduced and heat generation of the winding can be reduced.

Further, the space d between the tips of the teeth does not require a space for passing the winding through the winding port of the device, so that the distance d between the tips of the teeth can be reduced. Therefore, the change in the gap between the teeth and the outer peripheral portion of the rotor is reduced, and the cogging torque is reduced.

Conventionally, when a single winding is wound around the stator 2 by the winding device, only a space factor of about 30% can be wound. However, when assembling after winding around the core element 5, the space factor of the slot portion 8 can be easily reduced to 3
0% or more, and the space factor can be 60% or more.

The magnetic pole portions 12 at the ends on the inner peripheral side of the slot forming recesses 9 of the respective core elements 5 protrude toward both sides in the circumferential direction, and have a small gap d between the distal ends thereof. 5 is configured so as to be connected to the magnetic pole portions 12 of the core elements 5 so that there is no break in the circumferential magnetic flux distribution from the magnetic pole portions 12 of each core element 5. Further, both side portions 12a of the magnetic pole portion 12 are formed in a substantially triangular shape so that the width in the radial direction becomes smaller toward the tip, and the magnetic resistance at both side portions of the magnetic pole portion 12 is increased and the adjacent cores 12a are formed. Magnetic pole parts 12, 12 of elements 5, 5
Magnetic leakage between them is reduced.

In the first embodiment, the small gap d is 0 <d <0.2.
mm. The small gap d is made possible by winding the core element 5 and then assembling it. By only providing such a small gap, magnetic leakage from the winding of the slot 8 can be suppressed, and the cogging torque can be reduced. Becomes smaller. That the gap d satisfies 0 <d <0.2 mm is a value obtained by an experiment, and is a value in which the cogging torque is efficiently reduced. The reason why the tips are not completely contacted is to suppress the flow of invalid magnetic flux between the adjacent teeth portions 7.

However, in this gap d, the leakage magnetic flux between the adjacent core elements 5, 5 can be neglected, and if there is no problem in assembling accuracy, it can be set to 0 to eliminate the cogging torque.

It is appropriate that b <0.6 mm for a surface b of the tooth 7 opposite to the tip of the tooth 7 (the end of the tooth 7 and a surface facing between the tips of the teeth 7).
By setting b to be smaller than 0.6 mm, magnetic saturation occurs at the tip of the tooth portion 7 and an ineffective leakage magnetic flux can be reduced.

On the other hand, the rotor 3 has a rotor core 13 made of a high magnetic permeability material through which the magnetic flux of the rotating magnetic field generated by the winding group of the stator 2 can easily pass, and the rotor core 13 is arranged at regular intervals in the circumferential direction corresponding to the poles of the rotor 3. And a permanent magnet 14 provided therein. These permanent magnets 14 are arranged such that S poles and N poles alternate in the circumferential direction.

The teeth facing surface 14a of the permanent magnet 14 is linear. The distance between the teeth facing surface 14a and the outer periphery of the rotor 13 is larger at the center of the permanent magnet 14 than at the end. As described above, by providing a portion where the magnetic flux easily passes through and a portion where the magnetic flux does not easily pass therethrough, it is possible to create an inductance difference between the q-axis inductance and the d-axis inductance, and the rotational driving is performed using the reluctance torque. can do. Note that the shape of the permanent magnet 14 may be a shape in which a central portion protrudes toward the center of the rotor 13.

The outer peripheral portion of the rotor core 13 has a third
As shown in detail in the drawing, a linear cutout 15 is formed at a portion where the ends of the permanent magnet 14 are adjacent to each other.

The outer periphery of the stator 2 is covered with a ring-shaped frame portion 21 to reinforce the integrated core element 5 by welding. Thus, the frame portion 21
, The core element 5 is firmly fixed even with a high-speed rotating electric motor. If the stator body assembled with the core elements 5 has sufficient strength, it is not necessary to reinforce the frame element 21.

With the above configuration, the electric motor of the present invention can be driven by using the reluctance torque in addition to the magnet torque. Although the space factor of the slot portion 8 of this motor is 60% or more, the size of the stator is small.

Therefore, since the output torque of the motor that is driven to rotate by using the reluctance torque in addition to the magnet torque has the relationship shown in the equation (1), when the space factor of the slot 8 is increased, Ld −Lq becomes large, and the output torque can be increased. Because the inductance L is proportional to N ² (the number of turns), the output becomes higher as the number of turns is larger, that is, as the space factor in the slot portion 8 is higher.

Therefore, in a motor driven by utilizing reluctance torque in addition to magnet torque, if the winding is wound around the core element 5 and then combined with the stator 2, the space factor can be increased, so that high output and high output can be obtained. It can be small.

The width of the adjacent permanent magnet is equal to the width of the teeth (8 in FIG. 1) opposed to two magnetic poles (two permanent magnets).
In a pole 12 slot, three teeth are opposed to two magnetic poles. In the case of 0.15 to 0.20 with respect to 8 teeth and 4 slots, which is equivalent to 6 teeth), it was found by experiments that the torque ripple was reduced.

In the rotor 3, the rotor core 1
A substantially linear cutout 15 which is a rotor outer peripheral recess is formed in a portion of the outer peripheral portion of the permanent magnet 3 adjacent to the end of the permanent magnet 14. As described above, when the cut portion 15 is provided, the gap between the inner circumference of the stator 2 and the outer circumference of the rotor 3
4 becomes larger in the portion where the end portions are adjacent to each other. Therefore, the magnetic flux distribution in the gap between the inner periphery of the stator 2 and the outer periphery of the rotor 3 can be approximated to a sine waveform by increasing the magnetic resistance in the gap.

It is to be noted that the length of the rotor outer peripheral recess located outside the portion between the adjacent permanent magnets is suitably a length corresponding to an angle of 0.2 to 0.4 of the central angle of one pole of the rotor core. is there.

The gap h between the teeth 7 and the cutout 15 must be at least twice the gap between the teeth 7 and the outer periphery of the rotor. In addition, in the case of Example 1, it was found by experiments that the empty space between the teeth portion 7 and the resection portion is appropriately 0.7 to 1 mm.

As described above, according to the first embodiment, since the cogging torque generation factors on both the stator 2 side and the rotor 3 side can be suppressed, a synchronous motor having a small cogging torque can be provided.

By using such an electric motor for a compressor, a refrigerator, an air conditioner, an electric vehicle, or the like, it is possible to reduce the size and increase the storage space.

An electric motor used in an electric vehicle needs to be miniaturized in order to enlarge the office space, and an electric motor that can efficiently use the current of a charger is required. The electric motor used for electric bicycles is a flat wire,
In many cases, a cross section having a width of 4 mm or more and a height of 1.5 mm or more is used. Also, a large current flowing through the winding is often 300 amperes or more. Then, a large current is applied and
Since the motor rotates by 00, it is effective to use a motor having a short winding length and a small amount of heat generation with respect to the number of windings as in the motor of the present invention. Further, if the aligned winding is possible, it is possible to further increase the space factor than the round wire.

It is very effective to use the electric motor as in the present invention for an electric motor such as an electric vehicle which flows a large current.

In the above description, an electric motor using a single-wound stator utilizing a reluctance torque in addition to a magnet torque by embedding a permanent magnet has been described.
An excellent effect can be obtained even if a gap or resin material, which is a low magnetic permeability material, is provided inside the rotor instead of the permanent magnet, and the rotor is driven to rotate using only reluctance torque. That is,
Even if a single-wound stator is used for the synchronous motor, excellent effects can be obtained. (Embodiment 2) Embodiment 2 will be described with reference to FIG.

In FIG. 5, reference numeral 31 denotes a synchronous motor which rotates mainly in the forward rotation direction F by utilizing reluctance torque in addition to magnet torque, and is constituted by a stator 32, a rotor 33 and a rotating shaft. I have.

The stator 32 includes a ring-shaped frame portion and a plurality of independent core elements 3 made of a high magnetic permeability material.
And a winding wound around a slot 38 formed between the teeth 37 of each core element 35, and a current is applied to a group of the windings. Thus, a rotating magnetic field is generated.

Then, a permanent magnet 39 is embedded in a rotor 33 provided in the stator 32. The shape of the permanent magnet 39 is V-shaped, and the permanent magnet is
3 protrudes toward the center. In this way, by setting the reverse saliency, it is possible to increase the inductance difference between the d-axis and the q-axis. Also, this permanent magnet 39
Is the front portion 39a of the permanent magnet 39a in the forward rotation direction F of the rotor.
b and a permanent magnet rear portion 39b. At this time, the thickness of the permanent magnet rear portion 39b is larger than the thickness of the permanent magnet front portion 39a.

The reason for such a configuration is as follows. In the permanent magnet rear part 39b, the permanent magnet rear part 39b
There is a possibility that the magnetic flux generated from the magnetic field and the magnetic flux output from the teeth portion 37 repel each other, and the permanent magnet rear portion 39b is demagnetized. Therefore, since a permanent magnet that generates a magnetic force that does not cause demagnetization is required, the thickness of the permanent magnet is increased.

However, in a motor in which most of the rotation only rotates in the forward rotation direction F, the permanent magnet front portion 39a attracted by the attraction force from the teeth is
Since demagnetization does not occur, it is not necessary to provide the same thickness as the permanent magnet rear portion 39b. Therefore, the permanent magnet rear portion 39b
The front portion 39a of the permanent magnet may be made thinner. Therefore,
Even if the amount of permanent magnets is reduced in an electric motor that performs most rotations in the forward rotation, the amount of permanent magnets can be reduced without deteriorating characteristics.

The internal permanent magnet rear portion 39b
Is protruded toward the stator 35 and is thicker than the front portion 39a of the permanent magnet. However, the teeth-facing surface of the permanent magnet rear portion 39b provided inside is fixed to the permanent magnet front portion 39b.
A may be made symmetrical with the facing surface of a and protrude toward the center of the rotor.

The embedded magnet may have a weight for balance adjustment embedded in the rotor at the front part and the rear part when driven to rotate.

The shape of the permanent magnet is not limited to the V-shape, but may be a linear shape or an arc shape. (Embodiment 3) Embodiment 3 will be described with reference to FIG.

In FIG. 6, reference numeral 51 denotes a synchronous motor which rotates by using reluctance torque in addition to magnet torque, and comprises a stator 52, a rotor 53 and a rotating shaft 54.

The stator 52 is formed by annularly combining a plurality of independent core elements 55 made of a material having a high magnetic permeability. Each of the core elements 55 is constituted by a winding wound around a slot portion 58 formed between the teeth portions 57, 57, and a rotating magnetic field is generated by applying a current to a group of these windings. Have been.

The rotor 53 is fixed to a rotor core made of a high magnetic permeability material by fixing four sets of permanent magnets 59 and 60 arranged so that N poles and S poles are alternately arranged to an embedded rotor shaft 54. ing. The permanent magnet per pole is divided into two in the radial direction of the rotor, and is composed of an outer permanent magnet 59 and an inner permanent magnet 60. Each of the permanent magnets 59 and 60 is formed in a circular arc shape protruding toward the center of the rotor, and both end portions 59a and 60a extend to positions near the outer periphery of the rotor. The interval between the outer peripheral permanent magnet 59 and the inner peripheral permanent magnet 60 has a substantially constant width, and a passage 61 through which the magnetic flux in the q-axis direction passes is formed in this interval.

The stator 52 has a predetermined number of teeth 57.
And each tis 57 is provided with a winding (not shown). Since the winding at this time is wound for each core element 55, it can be wound as a single body. When an alternating current is applied to the stator winding, a rotating magnetic flux is generated, and a magnet torque and a reluctance torque act on the rotor 53 by the rotating magnetic flux, and the rotor 53 is driven to rotate.

The width M between the outer peripheral permanent magnet 59 and the inner peripheral permanent magnet 60 is desirably as small as possible in consideration of the magnetomotive force loss of the permanent magnets 59 and 60. However, q
From the viewpoint of the shaft inductance Lq, it is desired that the inductance is large enough not to cause magnetic saturation in order to increase the inductance.

Therefore, in the third embodiment, the width M is set so as not to saturate the magnetic flux generated by the current flowing through the winding.
Is set to a half of the width N of the teeth 56.
When examining the width M and the q-axis inductance Lq, the width becomes smaller than the width N1 / 3 of the teeth 57 having the width M. On the other hand, even when the width M becomes larger than the width N of the teeth 57, the q-axis inductance Lq hardly changes. Therefore, from this investigation, the distance between the outer peripheral permanent magnet 59 and the inner peripheral permanent magnet 60, that is, the width M may be larger than よ り of the width N of the stator 57.

In the third embodiment, the magnetic flux path is formed by a plurality of layers of permanent magnets. However, any number of layers may be used as long as the number of layers is two or more. all right.

Fourth Embodiment A fourth embodiment will be described with reference to FIGS. 7 and 8.

In FIG. 7, reference numeral 71 denotes a synchronous motor which rotates by using reluctance torque in addition to magnet torque, and comprises a stator 72 and a rotor 73.

The stator 72 has a ring-shaped frame portion 7.
4, a stator core formed by annularly combining a plurality of independent core elements 75 made of a high magnetic permeability material, and a winding wound around slots 78 formed between the teeth 77 of each core element 75. 80, and a rotating magnetic field is generated by supplying a current to the winding group.

As shown in FIG. 8, the ends of the core element 75 are connected to each other to form a core element group. The core element group has a space in the bent portion 81 at the end, so that it can be easily bent. In this way, by winding and bending the winding 80 with the core element group to configure the stator 72, the positioning of the stator assembly becomes easy. At this time, the core elements 75 may be connected by welding, or the ring-shaped frame portion 74 may be fitted and fixed.

The core element group may constitute one group to form an annular stator, or a plurality of core element groups may be combined to form an annular stator.

Instead of forming the stator by contacting the end faces of the core elements 75, the stator may be formed by solidifying the core element group with a resin or the like.

[0061]

According to the present invention, since the winding is wound around the teeth portion, the winding does not protrude significantly from the end face of the stator, and the coil end can be reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an electric motor according to a first embodiment.

FIG. 2 is a partial sectional view of the stator.

FIG. 3 is a partial sectional view of the rotor.

FIG. 4 is a view showing the core element.

FIG. 5 is a sectional view of the electric motor according to the second embodiment.

FIG. 6 is a sectional view of the electric motor according to the third embodiment.

FIG. 7 is a sectional view of the electric motor according to the fourth embodiment.

FIG. 8 is a partial sectional view of a core element group of the electric motor according to the fourth embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Motor 2 Stator 3 Rotor 7 Teeth part 14 Permanent magnet 15 Cutting part

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H02K 1/27 501 H02K 1/27 501K 3/18 3/18 P 19/10 19/10 A (72) Inventor Yasufumi Kazumi 1006 Kazuma Kazuma, Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. 1006 Kadoma, Ichidai-ji Matsushita Electric Industrial Co., Ltd. CA01 CC11 CC15 CC17 EE01 EE03 FA16 5H619 AA01 AA07 BB01 BB06 BB15 BB24 PP01 PP02 PP05 PP06 PP08 5H621 GA01 GA04 GA12 GA16 HH01 HH09 JK02 JK05 5H622 A A03 CA02 CA07 CA14 CB03 CB04 CB05 PP11

Claims (8)

[Claims] 1. A stator core having a plurality of teeth, a winding having a single body wound around the teeth, and a rotor having a plurality of low permeability parts provided therein, wherein the low permeability part has a gap. An electric motor that rotates using the reluctance torque. 2. A stator core having a plurality of teeth, a winding having a single body wound around the teeth, and a rotor having a plurality of low-permeability parts provided therein, wherein the low-permeability part is made of resin. An electric motor that rotates using the reluctance torque that is the material. 3. The electric motor according to claim 1, wherein the low magnetic permeability portion is formed in a plurality of layers in a radial direction of the rotor. 4. The electric motor according to claim 1, wherein the electric motor is driven to rotate at 300 amperes or more. 5. A compressor having the electric motor according to claim 1. 6. An electric bicycle comprising the electric motor according to claim 1. 7. An air conditioner having the electric motor according to claim 1. 8. A refrigerator having the electric motor according to claim 1.