JP2003047188A - Stator for electric motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stator which reduces insulation failure by preventing contact between phases of a stator winding, and further prevents damage on the winding, even if magnetizing a rotor furnished with permanent magnets by utilizing the stator winding. SOLUTION: The stator, which prevents insulation failure and damage on the winding, even if magnetizing the rotor furnished with the permanent magnets by utilizing the stator winding, is achieved by disposing a non-magnetic annular member to protect the winding inside the winding which protrudes the stator end surface, and by providing the annular member with a plurality of partition plates which are radially extended from the side surface of the annular member in the outer diameter direction of the stator in order to prevent contact of the winding, protruding from the stator end surface each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the structure of a stator of an electric motor used in industrial equipment, office equipment, and household appliances. In particular, it relates to a stator of an electric motor provided with a permanent magnet type rotor in which a permanent magnet is used.

[0002]

2. Description of the Related Art Conventionally, in electric motors used in industrial equipment, office equipment, and household appliances, electric motors have become smaller and more efficient from the viewpoint of energy saving in recent years, and high-performance permanent magnets are used in rotors of electric motors. An electric motor including a so-called permanent magnet type rotor is often used. As a result, a compact and high-performance motor is designed.

Accordingly, there is a demand for an electric motor having a high space factor (a ratio of the winding to the slot of the stator) even in the winding wound in the slot of the stator of the electric motor.

In such a stator of a motor having a high space factor, as a matter of course, the number of windings protruding from the end face of the stator is also very large. In particular, in the stator 1a with the supplementary tooth portion 3 in which the winding 2a is straddled over the main tooth portion 4 of the 12-slot three-phase four-pole stator 1a shown in FIG. Since a winding ring wound by an external winding machine is inserted into the formed slot 9a by machine insertion or the like, a large winding ring must be formed in order to improve the insertability of the winding 2a. Winding 2 protruding from the end face of 1a
The amount of a becomes very large. As a result, the winding wheels mounted on the respective main tooth portions 4 of the stator 1a often come into contact with each other between the main tooth portions 4 and the complementary tooth portions 3 formed between the main tooth portions 4 and beyond. (The broken line shows the circumference of the winding 2a protruding from the end face of the stator 1a.)

Further, although not shown, in the case of a normal distributed winding or the like, an insulating film or the like is surely insulated at a portion where the winding contacts. For example, in a place where phases overlap each other, insulation is generally performed with an insulating material such as a polyester film (PET) so that the U phase, the V phase, and the W phase can be surely insulated.

Similarly, in the case of a concentrated winding electric motor in which the windings are wound directly around the teeth of the stator, adjacent windings are interphased in the stator of the motor having a high space factor with a large number of windings. The number of contact points increases.

[0007]

Conventionally, in order to solve such a problem, after the winding is mounted in the slot formed by the main tooth portion and the complementary tooth portion of the stator by machine insertion or the like, It is pushed by hand to ensure that the phases are separated. Another method is to reduce the protrusion of the winding from the end face of the stator and change the winding frame itself that winds the winding so that the phases of the winding do not come into contact with each other. In addition, if the reel is too small, it will not be possible to insert the winding into the slot of the stator, and none of them is the best method.

That is, the former requires an operator to be constantly attached to the manufacturing process of the product in order to separate the phases of the windings, and the latter requires time for adjusting the winding frame itself. However, if the winding frame itself is too small, the winding is forcibly inserted into the slot, which damages the winding and causes a rare defect or damage to the slot insulation or the like, resulting in poor withstand voltage.

Further, in an electric motor incorporated in a hermetic compressor or the like in which the rotor of the electric motor is provided with a permanent magnet type rotor or the like, after the electric motor is incorporated in the hermetic compressor, the stator winding of the electric motor is attached. A so-called built-in magnetizing method, which is also used as a magnetic winding and which magnetizes a rotor provided with a permanent magnet arranged to face the stator, is generally adopted.

This method will be described with reference to the magnetization connection diagrams of FIGS. 9 and 10. In FIG. 9, the three phases of the stator winding are also used as the magnetized winding. For example, the U phase of the stator winding is connected to the + side of the magnetizing power source side, the V phase and the W phase are connected to the − side, and the rotor provided with a permanent magnet is aligned with a predetermined position, It can be magnetized by passing a magnetizing current through the winding. Further, FIG. 10 also shows a method in which two phases of the stator winding are also used as magnetizing windings to magnetize the permanent magnets attached to the rotor. For example, the U phase of the stator winding is connected to the + side of the magnetizing power supply side, the V phase is connected to the − side, and the W phase is opened. As another method, the U phase is connected to the + side of the magnetizing power source side, the W phase is connected to the − side, and the V phase is opened. In this case as well, the rotor can be magnetized by aligning the rotor provided with the permanent magnet at a predetermined position and flowing a magnetizing current through the stator winding as in the above case.

In such a method, in order to completely magnetize the permanent magnet attached to the rotor, a large current must be passed through the stator winding to magnetize the permanent magnet. Depending on the direction of the electric current, the winding repulsion of the winding itself occurs. In particular,
In many cases, the windings fall to the inner diameter side of the stator, causing contact with the rotor during motor operation, resulting in a burnout accident. Such a phenomenon is particularly remarkable in the U phase in FIG. Further, in FIG. 10, when the U phase is connected to the + side of the magnetizing power source side and the V phase is connected to the − side, both appear as the U phase and the V phase. When the U phase is connected to the + side of the magnetizing power supply side and the W phase is connected to the − side, both the U phase and the W phase appear. Further, in many cases, due to the strong magnetic field at the time of magnetization, the winding is attracted to the rotor, which is a magnetic material arranged on the inner diameter side of the stator, and the winding falls to the inner diameter side of the stator. Contact with the rotor causes a burnout accident.

When used as an electric motor in a hermetic compressor such as a refrigerator or an air conditioner, an HFC that considers environmental problems
As the refrigerating machine oil in the hermetic compressor for using alternative refrigerants such as 134a, HFC410a, HFC407c, polyalkylene glycol-based oil, polyester-based oil, ether-based oil, etc. are often used, which facilitates water dissolution. There is. Therefore, the insulating material of the electric motor must be a material that does not cause hydrolysis by water.

[0013]

In a motor with a complementary tooth part in which a winding is inserted across a main tooth part of a stator, a non-magnetic ring covering an inner diameter side of a winding end part protruding from a stator end face. By arranging the members and providing a plurality of partition plates radially extending from the side surface of the annular member toward the outer diameter direction of the stator, the windings protruding from the end face of the stator are prevented from contacting each other. It is possible to reliably separate the phases and to reduce the insulation failure. Moreover, when magnetizing the rotor provided with the permanent magnet using the stator winding as the magnetizing winding, it is possible to prevent the stator winding from falling toward the inner diameter side by the annular member.

Further, in particular, in an electric motor in which windings are directly wound around the teeth of the stator and concentratedly wound, an annular member similar to the above is attached to the inner diameter side of the winding protruding from the end face of the stator. The windings of each phase directly wound around the teeth of the stator can be reliably separated, and insulation failure due to interphase contact can be reduced.

Further, in order to increase the strength of the annular member, a flange is formed from the end of the annular member opposite to the end face side of the stator to which the annular member is attached, toward the outer diameter side of the stator, to form the flange. The strength of can be increased.
Accordingly, for example, when the rotor including the permanent magnet is magnetized by using the stator winding as the magnetizing winding, the strength can be maintained against the force falling to the inner diameter side of the stator winding.

Further, by making the height of the annular member higher than the height of a plurality of partition plates radially extending from the side surface of the annular member toward the outer diameter direction of the stator,
The lead wires and windings drawn around the end face of the stator will not fall into the inner diameter side of the stator, preventing contact with the rotor arranged on the inner diameter side of the stator and easily removing the lead wires and windings. Can be fixed.

The material of the annular member is PEN (polyethylene naphthalate), PBT (polybutylene terephthalate), PPS (polyphenylene sulfide), L.
HFC134a, HFC410a, H by using CP (liquid crystal polymer resin), fluororesin, PEEK (polyether ether ketone), and aromatic polyamide resin
It can be used as an electric motor of a hermetic compressor that uses an alternative refrigerant such as FC407c, and can be used as an insulating material of an electric motor that does not cause hydrolysis by water.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an electric motor with a complementary tooth portion 3 in which a winding 2a is inserted across a main tooth portion 4 of a stator 1a. The stator 1a has main tooth portions 4 and complementary tooth portions 3 formed between the main tooth portions 4. Due to the electric motor performance, the complementary tooth portion 3 is the stator 1a.
The cogging torque can be reduced and the sound and vibration can be reduced by providing between the main tooth portion 4 and the main tooth portion 4. Also, the performance of the electric motor can be improved.

The stator 1a shown in FIG. 1 forms a 12-slot three-phase four-pole structure. As described above, the winding 2a wound by an external winding machine is inserted into the slot 9a by a machine or the like so as to mount the winding 2a on one main tooth portion 4. Usually, the method of inserting the winding 2a into the slot 9a of the stator 1a by a machine or the like is called an inserter method.
(The broken line shows the winding 2a protruding from the end face of the stator 1a.
Shows the circumference portion of the. )

Therefore, windings 2a forming different phases are attached to the adjacent main tooth portions 4 sandwiching the complementary tooth portion 3. The slot 9a of the stator 1a is provided with slot insulation 5a in order to insulate the winding 2a from the iron core of the stator 1a. The slot insulation 5a is insulated by a bobbin formed of a film or resin. In this case, the protrusion of the slot insulation 5a from the stator 1a does not interfere with the mounting of the winding 2a because the winding 2a is mounted on the main tooth portion 4 by machine insertion or the like. It is preferable that the winding 2a and the end surface of the stator 1a are protruded by a distance that can maintain insulation. Preferably, the protrusion of the slot insulation 5a from the end surface of the stator 1a is 2.0.
It is good to set it to about mm to 5.0 mm.

Although not shown, for example, when a permanent magnet type rotor or the like is used for the rotor of the electric motor, the winding 2a of the stator 1a of the electric motor is used as a magnetizing winding and the stator 1a is used. When magnetizing the permanent magnet type rotor which is arranged opposite to, the winding 2a is attracted and repelled depending on the direction of the current flowing through the winding 2a of the stator 1a, or the stator 1a
When the winding 2a is pulled toward the inner diameter side of the stator 1a by being attracted to the rotor, which is a magnetic material arranged on the inner diameter side of a, the non-magnetic side of the winding 2a protruding from the end surface of the stator 1a This can be prevented by attaching the annular member 6a. As a result, the winding 2a does not come into contact with the rotor during the operation of the electric motor to cause a burnout accident, and the occurrence of insulation failure can be prevented.

Further, in the electric motor with the complementary tooth portion 3 in which the winding 2a having a high space factor is inserted across the main tooth portion 4 of the stator 1a, adjacent windings 2a do not come into contact with each other so that insulation failure does not occur. As described above, the plurality of partition plates 10a are radially provided from the side surface of the annular member 6a toward the outer diameter direction of the stator 1a and the complementary tooth portion 3 is formed.
By arranging the windings 2a so as to follow each other, the phases of the windings 2a can be surely separated from each other, and there is no interphase contact in each phase, so that insulation failure can be reduced. Note that FIG. 3A is a perspective view of the annular member 6a.

FIG. 2 shows a concentrated winding electric motor in which the winding 2b is directly wound around the tooth portion 8 of the stator 1b having 6 slots and 3 phases and 4 poles. As mentioned above, one tooth 8
The winding 2b is directly wound around the. Also in this case
Similarly, in the slot 9b of the stator 1b, the slot insulation 5 is provided in order to insulate the winding 2b from the iron core of the stator 1b.
b is given. The slot insulation 5b is insulated by a bobbin formed of film or resin. The difference from FIG. 1 is that the complementary tooth part 3 is not provided.
(The broken line shows the winding 2b protruding from the end face of the stator 1b.
Shows the circumference portion of the. )

Similarly, in FIG. 2, when a permanent magnet type rotor or the like is used for the rotor of the electric motor, the winding 2b of the stator 1b of the electric motor is used as a magnetized winding and is arranged to face the stator 1b. When the permanent magnet type rotor is magnetized, the stator 1b
The winding 2b is attracted and repelled depending on the direction of the current flowing through the winding 2b, or the winding 2b is drawn toward the inner diameter side of the stator 1b by being attracted to the rotor which is a magnetic material arranged on the inner diameter side of the stator 1b. This motor's stator 1 so that it will not fall down and come into contact with the rotor during the operation of the motor to cause a burnout accident.
On the inner diameter side of the winding 2b protruding from the end face of b, the winding 2b
By arranging the non-magnetic annular member 6a for protecting the above, it is possible to prevent the occurrence of insulation failure.

In the case of FIG. 2, the windings 2b having a high space factor, which are concentratedly wound around the tooth portion 8 of the stator 1b, are mounted so that the adjacent portions in the slots 9b are out of phase with each other. Therefore, a plurality of partition plates 10a radially extending from the side surface of the annular member 6a toward the outer diameter direction of the stator 1b prevent the adjacent windings 2b in the slots 9b from contacting each other and causing insulation failure. The windings 2b having different phases in 9b are arranged on the end surface of the stator 1b.

The slot 9b in the stacking direction of the stator 1b
In the inside, different phases are surely separated by a film-like in-slot in-slot interphase insulation 11 or the like.
Insulation of the winding 2b in the slot is performed by film-like interphase insulation, and the winding 2 protruding from the end of the stator 1b
Since the inner diameter side of b is insulated by the annular member 6a, it takes twice as much time to insulate the inside of the slot 9b and to insulate the winding 2b protruding from the end of the stator 1b. Therefore, from the side surface of the annular member 6a to the stator 1b
Partition plates 10 extending radially toward the outer diameter of the
The partition plate 10a penetrating the center of the slot 9b in the axial direction so as to separate the winding 2b in the slot 9b of the stator 1b from a allows only one interphase insulation between different phases. The partition plate 10a is located substantially at the center of each slot 9b, and can reliably separate adjacent different phases in one slot.

FIG. 3 (a) is a perspective view of the annular member 6a attached to FIGS. 3B shows a case where the inter-slot interphase insulation 11 is shared with the partition plate of the annular member, and a plurality of partition plates radially extending from the side surface of the annular member 6b toward the outer diameter direction of the stator 1b. 10B is a perspective view of the annular member 6b when the partition plate 10b is provided with the partition plate 10b extending in the slot 9b of the stator 1b in the axial direction for inter-slot interphase insulation.

As a method for attaching the annular members 6a and 6b of FIGS. 1 to 3 to the stators 1a and 1b, the annular member 6a is used.
Windings 2a protruding from the end faces of the stators 1a and 1b
After attaching the annular members 6a and 6b to the inner diameter sides of the windings 2a and 2b, the windings 2a and 2b are fixed by a winding fixing string or a binding band.
It is tied and fixed at the same time as b. Incidentally, the annular members 6a and 6b
The fixing method of is not limited to this method.

FIG. 4 shows the annular members 6a and 6 shown in FIG.
It is another example of b. For example, when a permanent magnet type rotor or the like is used for the rotor of the electric motor, in the rare earth magnet that requires a stronger magnetic field than the ferrite magnet, the annular members 6a and 6b shown in FIG. The windings 2a and 2b of the stator are magnetized windings, and the stators 1a and 1b are
When magnetizing the permanent magnet type rotor arranged opposite to
In some cases, the annular members 6a and 6b cannot prevent the winding from falling toward the inner diameter side of the stator.

In view of this, as in the shape of the annular member 6c shown in FIGS. 4 and 5, from the end of the annular member 6c located on the side opposite to the end face side of the stator to the outside of the stators 1a and 1b. By forming the collar 7 toward the radial side, the annular member 6a is formed.
And 6b can increase the strength. 4 shows the annular member 6c of the present embodiment, and FIG. 5 is a sectional view taken along the line AA 'so that the collar 7 of the annular member 6c of FIG. 4 can be seen.

Further, in the annular member 6d shown in FIG. 6, the lead wire drawn around the end of the stator, the winding drawn out from the stator slot, etc. fall to the inner diameter side of the stator and come into contact with the rotor during operation of the motor, resulting in a burnout accident. The height of the non-magnetic annular member 6d is made higher than the height of the plurality of partition plates 10c radially extending from the side surface of the annular member 6d toward the outer diameter direction of the stator so as not to cause It is possible to prevent the winding and the like from falling toward the inner diameter side of the stator. Further, since the lead wire and the winding wire do not fall toward the inner diameter side of the stator, the work of fixing the lead wire and the winding wire can be easily performed.

Incidentally, FIG. 7A is a sectional view taken along line BB 'of FIG. The broken line in the drawing indicates the lead wire 12, the winding wire 2c, and the like. In FIG. 7B, as described in FIG. 7A, the lead wire 12, the winding wire 2c, etc. are prevented from falling toward the stator inner diameter side, and the stator outer diameter of the partition plate 10d is also shown. By extending the outer end portion located on the side in the axial direction opposite to the end face side of the stator, it is possible to prevent the lead wire 12, the winding 2c, and the like from falling toward the outer diameter side of the stator. Further, by using the present embodiment in FIGS. 3B and 4, it is possible to obtain a better effect.

Further, in the electric motor used for the hermetic electric compressor or the like, the refrigerant in the hermetic compressor is changed to HFC134a, HFC410a, HFC40 in view of recent environmental problems.
It has become a hermetic compressor using an alternative refrigerant such as 7c.

Conventionally, as refrigerating machine oil in a hermetic compressor,
Although naphthene-based or paraffin-based mineral oil or alkylbenzene-based oil was used, it hardly dissolved water due to its structure, but due to the structure of the refrigeration system or compatibility with alternative refrigerants The use of polyalkylene glycol-based oils, polyester-based oils or ether-based oils as refrigerating machine oil has made it easier to dissolve water.

Therefore, the materials of the annular members 6a, 6b and 6c are PEN (polyethylene naphthalate) and PBT.
(Polybutylene terephthalate), PPS (polyphenylene sulfide), LCP (liquid crystal polymer resin), fluororesin, PEEK (polyether ether ketone),
By using aromatic polyamide resin, HFC134
It can be used as an electric motor in a hermetic compressor using an alternative refrigerant such as a, HFC410a, HFC407c, etc., and can be used as an insulating material for an electric motor that does not cause hydrolysis by water.

[0036]

In the electric motor with the complementary tooth portion in which the winding is inserted across the main tooth portion of the stator, the non-magnetic annular member for protecting the winding is provided on the inner diameter side of the winding protruding from the end face of the stator. This annular member is securely wound by providing a plurality of partition plates radially extending from the side surface of the annular member toward the outer diameter direction of the stator so that the windings protruding from the end face of the stator do not come into contact with each other. Insulation defects can be reduced by eliminating the contact between the phases of the wires. Further, it is not necessary to forcibly separate the windings from each other and secure the insulation distance, so that the number of steps can be shortened. Further, even when the windings are bent and the phases come into contact with each other, it is not necessary to forcibly reduce the size of the winding frame itself, so that the windings are not damaged and the insulation failure can be reduced.

In an electric motor incorporated in a hermetic compressor or the like, when a stator winding is used as a magnetizing winding to magnetize a permanent magnet in a rotor, a large current flows and is fixed in the stator winding. It is also possible to prevent the coil from falling on the inner diameter side of the child and coming into contact with the rotor during the operation of the motor to cause a burnout accident.

Further, the same effect as described above can be obtained by attaching the annular member to the concentratedly wound electric motor in which the winding is directly wound around the teeth of the stator. In addition, it is more advantageous in terms of cost to form the slot insulation by using an insulating material such as a film than by using a bobbin formed of resin or the like.

Further, in order to increase the strength of the annular member, the annular member is formed by forming a flange from the end of the annular member opposite to the end surface side of the stator to which the annular member is attached, toward the outer diameter side of the stator. The strength of can be increased.
Thus, for example, when a rotor equipped with a rare earth magnet that requires a stronger magnetic field than a ferrite magnet is used by magnetizing the stator winding as the magnetizing winding, the stator winding is It is possible to maintain the strength against the force of falling toward the inner diameter side of the.

Further, by making the height of the annular member higher than the height of the plurality of partition plates radially extending from the side surface of the annular member toward the outer diameter direction of the stator, the lead wires, windings, etc. are fixed to the stator. It is prevented from dropping to the inner diameter side, contact with the rotor arranged on the inner diameter side of the stator can be prevented, and the lead wire, winding, etc. can be easily fixed. The annular member of the present invention may be arranged on either or both of the lead wire lead-out side and the non-lead wire lead-out side of the stator.

The material of the annular member is PEN (polyethylene naphthalate), PBT (polybutylene terephthalate), PPS (polyphenylene sulfide), L.
HFC134a, HFC410a, H by using CP (liquid crystal polymer resin), fluororesin, PEEK (polyether ether ketone), and aromatic polyamide resin
It can be used as an electric motor of a hermetic compressor that uses an alternative refrigerant such as FC407c, and can be used as an insulating material of an electric motor that does not cause hydrolysis by water.

[Brief description of drawings]

FIG. 1 is a diagram of a stator with a complementary tooth part showing an embodiment of the present invention.

FIG. 2 is a diagram of a stator showing another embodiment of the present invention.

FIG. 3 is a perspective view of an annular member according to an embodiment of the present invention.

FIG. 4 is a perspective view of an annular member according to another embodiment of the present invention.

5 is a sectional view taken along the line A-A 'of the annular member of the embodiment of FIG.

FIG. 6 is a perspective view of an annular member according to another embodiment of the present invention.

7 (a) is a sectional view taken along line BB ′ of the annular member of the embodiment of FIG.
Sectional view. (B) is sectional drawing of the annular member of another Example.

FIG. 8 is a diagram of a stator showing a conventional embodiment.

FIG. 9 is a magnetizing connection diagram when the stator winding is a magnetizing winding.

FIG. 10 is another magnetization connection diagram when the stator winding is a magnetized winding.

[Explanation of symbols]

1a, 1b ... Stator, 2a, 2b, 2c ... Winding, 3 ... Complementary tooth portion, 4 ... Main tooth portion, 5a, 5b ...
-Slot insulation, 6a, 6b, 6c, 6d ... Annular member, 7 ... Collar, 8 ... Tooth, 9a, 9b ... Slot, 10a, 10b, 10c, 10d ... Partition plate,
11 ... Insulation between phases in slot, 12 ... Lead wire,
U, V, W ... Phase winding of the stator, E ... Power supply.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kaneharu Mano             Aichi-Ema, 2 Aichi-cho, Kasugai-shi, Aichi             Son Electric Co., Ltd. F-term (reference) 5H002 AA09 AB07 AE07                 5H604 BB01 BB10 BB17 CC01 CC05                       CC16 DA14 DA20 DA24 DB01                       DB26 PB02 PB03 PE02 PE03                       QA01                 5H622 QB01

Claims (6)

[Claims] 1. In a motor with a complementary tooth part, in which a winding is inserted across a main tooth part of a stator, a non-magnetic motor for protecting the winding on the inner diameter side of the winding protruding from the end face of the stator. An annular member is arranged, and a plurality of partition plates extending radially from the side surface of the annular member toward the outer diameter direction of the stator are provided, and the adjacent plates that protrude from the end face of the stator by the partition plates. An electric motor characterized in that the wires do not touch each other. 2. In a motor in which a winding is directly wound around a tooth portion of a stator and concentratedly wound, a non-magnetic annular member for protecting the winding is provided on an inner diameter side of the winding protruding from an end surface of the stator. A plurality of partition plates that are arranged and radially extend from the side surface of the annular member toward the outer diameter direction of the stator are provided, and the adjacent windings protruding from the stator end surface by the partition plates are adjacent to each other. An electric motor characterized by being prevented from contacting. 3. In an electric motor in which a winding is directly wound around a tooth portion of a stator and concentratedly wound, a non-magnetic annular member for protecting the winding is provided on an inner diameter side of the winding protruding from an end surface of the stator. A plurality of partition plates that are arranged and radially extend from the side surface of the annular member toward the outer diameter direction of the stator are provided, and the partition plates project from the end face of the stator, between the adjacent windings. An electric motor which prevents contact and extends the partition plate so as to axially penetrate the slot of the stator. 4. The flange of the annular member is formed from the end of the annular member opposite to the end face side of the stator toward the outer diameter side of the stator. A stator for an electric motor according to claim 3. 5. The height of the annular member is higher than the height of a plurality of partition plates radially extending from the side surface of the annular member toward the outer diameter direction of the stator. The electric motor according to claim 4. 6. The material of the annular member is PEN (polyethylene naphthalate), PBT (polybutylene terephthalate), PPS (polyphenylene sulfide), L.
6. The stator for an electric motor according to claim 1, wherein CP (liquid crystal polymer resin), fluororesin, PEEK (polyether ether ketone), or aromatic polyamide resin is used.