KR20140119233A - Motor Device - Google Patents

Abstract

The present invention relates to a motor apparatus having a magnet on an outer circumference of a disk shaped or a wheel shaped rotor and a stator at a line extending in a radial direction of the rotor or at a vertical direction of the rotor surface such that the motor can be manufactured in a circular disk shape and an output of the motor is increased by using a difference of an angular speed of the rotor and a motor shaft. The motor apparatus according to the present invention includes: a shaft: a rotor coupled to the shaft and having a circular plate shape or a wheel shape having a spoke and a rim; a plurality of rotor magnets radially coupled to an outer circumference of the rotor and spaced apart from each other and having a pair of pole faces, which have a plate shape in parallel to a surface of the rotor; and a plurality of stators provided at a line extending in a circumferential direction of the rotor and spaced apart from each other, and having a stator member and a pair of stator pieces facing the pair of the pole faces, respectively, extending from the stator member.

Description

[0001]

The present invention relates to a motor, and particularly to a motor in which a magnet is disposed on the outer periphery of a disc-shaped or wheel-shaped rotor, and a stator is provided in a direction perpendicular to the radial direction of the rotor or a rotor surface. And a motor device capable of increasing the output by using a difference in angular velocity between the rotor and the motor shaft.

Electric motors or generators are very important devices that use electric power or produce electricity, and they have long been used as essential devices in various fields. Electric motors are still being improved and developed due to the development of materials, structure, and mechanics related technology, and expansion of applications.

Such improvement and development directions are directed to conversion efficiency to convert power to power, shape suitable for the purpose of use, miniaturization and high power output.

For this purpose, a conventional motor uses a method in which the area of the electromagnetic field is increased by partially increasing the axial length and cross-sectional area of the motor, or using a motor in which the rotor and the stator are constituted by a plurality of motors. Or a speed reducer is attached to the shaft of the motor and the motor is made in a high rotation type so as to obtain a large torque and an output.

However, such a conventional motor has a problem that it is difficult to install the motor in a narrow space and the weight of the motor increases because the axial length of the motor increases, or the installation area such as a speed reducer is combined.

Particularly, in recent years, a demand for an electric motor, an electric bicycle, or an electric motor of a type that can be used in a narrow space has been greatly increased, but the conventional motor has a problem that it is difficult to meet such a demand.

Therefore, according to the present invention, a magnet can be disposed on the outer periphery of a disc-shaped or wheel-shaped rotor, and a stator can be provided in a direction perpendicular to the radial direction of the rotor or the rotor surface, And an output of the motor is increased by using a difference in angular velocity between the motor shaft and the motor shaft.

According to an aspect of the present invention, there is provided a motor device comprising: a shaft; The rotation itself being formed in a wheel-like shape through which the shaft is penetrated and which is in the form of a circular plate or a wheel including spokes and rims; And a pair of front and rear magnetic pole surfaces are formed in a plate shape parallel to the rotation self-surface, the rotor magnet being formed of a plurality of rotor magnets, the rotor magnet being radially spaced apart from the outer circumferential surface or the circumferential surface of the rotation self- And a stator having a plurality of stator pieces disposed radially spaced apart from each other on a circumferential extension line of the rotation itself and extending from the stator itself and the stator itself and having a pair of stator pieces facing each of the pair of stator surfaces; .

The surface of the stator that faces the rotor magnet and the rotor magnet is curved.

Wherein the plurality of rotor magnets are arranged such that the polarities of the pole faces between adjacent rotor magnets are inverted, and the stator pole has the same polarity as the pole face of the stator pole when the stator pole faces the pole face And the polarity is adjusted so as to have a polarity opposite to the polarity of the pole face when the stator pole and the pole face mismatch.

According to another aspect of the present invention, there is provided a motor device comprising: a shaft; The rotation itself being formed in a wheel shape such that the shaft is penetratingly connected and comprising a circular plate or a rim and a spoke; A rotor magnet coupled to an edge of the front and rear surfaces of the circular plate of the rotation itself or to the front and rear surfaces of the rim and having a pair of front and rear pole faces orthogonal to the rotation inner face; And a plurality of permanent magnets which are arranged radially spaced from each other on the front and back surfaces of the circular plate of the rotation itself or on the front and rear surfaces of the rim and which are elongated from the fixation itself and the fixation itself, And a stator having a pair of stator pieces.

The rotor magnet or the stator is disposed such that the positions of the rotor magnet or the stator magnet coupled to the front and rear surfaces are shifted from each other with the rotation itself interposed therebetween.

Wherein the plurality of rotor magnets are arranged such that the polarities of the pole faces between adjacent rotor magnets are inverted, and the stator pole has the same polarity as the pole face of the stator pole when the stator pole faces the pole face And the polarity is adjusted so as to have a polarity opposite to the polarity of the pole face when the stator pole and the pole face mismatch.

The motor device according to the present invention can be manufactured in the form of a circular disk by disposing magnets on the outer periphery of a disk-shaped or wheel-shaped rotor and providing a stator in the direction perpendicular to the axis of rotation of the rotor, The output can be increased by using the difference in angular velocity between the rotor and the motor shaft.

1 is a perspective view of a motor device according to a first embodiment of the present invention;
2 is a schematic plan view of a motor device according to a first embodiment of the present invention;
3 is an exemplary view showing a plan view and a side view of a rotor;
Fig. 4 is an exemplary view showing the side shapes of the rotor and the stator according to the first embodiment; Fig.
5 is a side view and a rear view of the stator and a side view and a rear view of the rotor.
6 is an exemplary view for explaining the rotation of the rotor;
7 is an exemplary view showing a drive circuit of a motor device.
8 is an exemplary view showing a motor device according to a second embodiment of the present invention;
Fig. 9 is an exemplary view showing in detail the stator and the rotor according to the second embodiment; Fig.
10 is a plan view and side elevational view of the motor device according to the third embodiment;
11 is a plan view and side elevational view of the rotor.
12 is an exemplary view showing the stator in more detail;

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. It should be noted that the drawings denoted by the same reference numerals in the drawings denote the same reference numerals whenever possible, in other drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear. And certain features shown in the drawings are intended to be illustrative, not limiting, or reduced, or simplified, and the drawings and elements thereof are not necessarily drawn to scale. However, those skilled in the art will readily understand these details.

FIG. 1 is a perspective view of a motor device according to a first embodiment of the present invention, and FIG. 2 is a perspective view of a motor device according to a first embodiment of the present invention. FIG. 3 is a plan view of a motor of the motor according to the first embodiment, and FIG. 3 is an exemplary view showing a plan view and a side view of the rotor. 4 is an exemplary view showing the side surfaces of the rotor and stator according to the first embodiment, and FIG. 5 is a side view and a rear view of the stator, and a side view and a rear view of the rotor, respectively. Fig. 6 is an exemplary diagram for explaining the rotation of the rotor, and Fig. 7 is an exemplary diagram showing a drive circuit of the motor device.

1 to 7, a motor device 100 according to a first embodiment of the present invention includes a rotor 10 and a stator 60.

The rotor (10) comprises a shaft (30), a rotor (11) and a rotor magnet (12). The rotation itself 11 is coupled to the shaft 30 and the rotor magnet 12 is rotated from the shaft 30 in the circumferential direction of the shaft 30 (I.e., the extension of the hypothetical line connecting one point on the circumference of the cylinder), and may be formed as a disk having a disk or a wheel having a rim and a spoke. 1 to 7 show an example in which the rotor itself 11 is formed in the form of a disk, but the present invention is not limited thereto, and the rotor magnet 12 may be fixed from the shaft 30 by a predetermined distance It is possible to deform the rotation body 11 in various forms. However, in the following, the present invention will be described focusing on a circular plate-shaped rotation body 11 for convenience of explanation.

In this rotor 10, a plurality of rotor magnets are spaced apart and fixed at a constant interval in the circumferential direction of the rotor 11 itself. 4, the rotor 10 is connected to the rotor boss 14 on the shaft 30, and the rotor itself 11 is coupled to the rotor boss 14 . And the rotor magnet 12 is coupled to the circumferential surface 15 of the rotation body 11. [ In FIGS. 3 and 4, the circumference 15 of the rotation itself 11 is shown to be thinner than the other portions of the rotation itself 11, but the present invention is not limited thereto. On the other hand, the rotor magnet 12 can use either an electromagnet or a permanent magnet, and the present invention is not limited to any one type of magnet. However, using the permanent magnet as the rotor magnet 12 is advantageous in that the structure of the motor device can be simplified, and high output can be achieved by easy control and low power.

The stator 60 is composed of a plurality of stator and is disposed at regular intervals (or ring or circular) along the outer periphery of the rotor 11 of the rotor 10 and is coupled to a case (not shown) of the motor device. As shown in FIG. 4, the stator 60 has a cross-sectional shape of 'C'. Specifically, the stator 60 includes a pair of stator pieces 62 (62a, 62a, 62a, 62a, 62a, 62a, 62a, 62a, , And 62b. Further, coils 70 for forming an electromagnetic field are wound around the stator pieces 62, respectively. On the other hand, the interval of the slits is determined so that the interval between the stator pieces 62a and 62b is minimized. When the distance between the stator pieces 62a and 62b and the rotor magnet 12 is increased, the distance between the stator piece 62 and the rotor magnet 12 is determined so that the torque and the output are reduced so that mechanical interference does not occur. do.

The stator pieces 62 have opposite magnetic poles due to the currents flowing through the coils wound on the stator pieces 62a and 62b and form a magnetic field between the stator pieces 62a and 62b through them, 12 by applying an attractive force or a repulsive force to the rotor 10.

5, the stator piece 62 may be thinner than the other portions of the coil 70 where the coil 70 is wound. 4, the portion where the coil 70 is not wound is formed thicker than the portion where the coil 70 is wound, so that the stator 60 (i.e., the stator 60) A part of the coil 70 can be covered by the stator piece 62. [ However, the present invention is not limited thereto.

On the other hand, a detector 40 may be coupled to the shaft 30. The detector 40 detects the rotation of the rotor 10, converts the rotation of the rotor 10 into an electric signal, and transmits the electric signal to the controller 90 of the motor device 100. The controller 90 uses the signal from the detector 40 to switch the polarity of the stator element 62 to alternately provide attraction force and repulsion force to the rotor magnet 12, . Here, in the case where the rotor magnet 12 is composed of an electromagnet, the detector 40 can convert the polarity of the rotor magnet 12 using the signal detected from the detector 40, It is not.

The detector 40 includes an optical sensor 43 such as a photocoupler and a pin wheel 42 for controlling the light of the optical sensor 43 according to the rotation of the rotor 10. More specifically, the optical sensor is disposed on one side of the pin wheel 42. The optical sensor includes a light output terminal (not shown) in which the blade of the pin wheel 42 is formed on the optical sensor 43, Not shown). At this time, the blade interrupts the light emitted from the optical output terminal to the optical input terminal, and the optical sensor 43 senses the generated light to generate an electric signal. Through this, the position of the rotor magnet 12 So that the control unit 90 can recognize it. The polarity of the stator 60 is reversed in accordance with the position between the rotor magnet 12 and the stator 60 of the control unit 90 and the rotor 10 is rotated.

FIGS. 6 and 7 are diagrams for explaining a control procedure for rotation of the motor device according to the first embodiment of the present invention. 6 and 7, the features of the motor device 100 according to the first embodiment will be described in more detail with reference to Figs. 1 to 5 described above.

1, 3 and 4, the motor device 100 according to the first embodiment is thinner than the conventional motor (in the longitudinal direction of the shaft 30, or perpendicular to the surface of the rotation self 11) It is possible to implement the motor device of the present invention.

Particularly, the motor device 100 according to the first embodiment is arranged so that the rotor magnet 12 is spaced apart from the shaft 30 by the diameter of the rotation self 11. The motor device 100 according to the first embodiment can increase the output by using the rotational force of the rotor magnet 12 by disposing the rotor magnet 12 away from the shaft 30 in comparison with the conventional motor . Specifically, in the motor device of the present invention, the circular motion of the rotor 10 is converted into a force on the shaft 30 by the principle of the angular momentum conservation law and the centrifugal force. That is, if the diameter of the rotation body 11 is increased, it is possible to realize a motor device of high output without increasing the thickness of the shaft 30. In particular, when the rotor magnet 12 uses a permanent magnet having a large coercive force and a large residual magnetism, and an electromagnet is used for the stator 60, it is possible to realize a low rotation high output motor device.

In addition, the motor device 100 of the present invention has the same surface area of the magnetic poles of the rotor magnet 12 and the stator 60, and the magnetic pole distance between the rotor magnet 12 and the stator 60 To a minimum. By maximizing the intensity of the magnetic field applied to the rotor magnet 12, the magnetic field generated by the same power is maximized, thereby improving the output of the motor device 100.

The motor device 100 according to the first embodiment of the present invention reverses the magnetic pole of the stator 60 in accordance with the rotation of the rotor 10 to alternately apply attraction force and repulsive force to the rotor magnet 12, .

To this end, the rotor magnet 12 according to the first embodiment of the present invention and the second and third embodiments to be described below are arranged so that the rotation itself 11 is rotated so that the poles of the adjacent rotor magnets 12 are reversed, . Specifically, assuming that one surface of the rotation body 11, for example, the surface facing the detector 40 is the front surface and the other surface of the rotation body 11 is the rear surface, any one of the neighboring rotor magnets 12 is N One of the poles and the S pole is arranged to face the front side, and the other neighboring magnet is arranged such that the other pole of the N pole and the S pole faces the front.

Specifically, a1, a2 and a3 in Fig. 6 represent rotor magnets 12, and a1 and a3 are rotor magnets 12 adjacent to a2. When this rotor magnet 12 is arranged at the outer periphery of the rotor 11, a1 is a plan view in which the S pole a1- is viewed from the front (in Fig. 6, the rotor 10 is viewed from the front direction). , A2 is arranged such that the N pole (a2 +) faces the front, and a3 is arranged such that the S pole (a3-1) faces the front. That is, as described above, the adjacent rotor magnets 12 are arranged such that the polarities of the surfaces facing in the same direction are reversed.

In order to rotate the rotor 10 having the rotor magnet 12 arranged in this way, the motor device of the present invention alternately provides a repulsive force and attractive force to the rotor magnet 12. Specifically, in the state where the rotor magnet 12 coincides with the stator 60 as shown in FIG. 6 (a), the magnetic poles of the rotor magnet 12 facing each stator 60, The stator 60 generates a repulsive force to the rotor magnet 12 so as to have the same polarity as the polarity of the surface. On the other hand, when the rotor magnet 12 is located between the stator 60 and the stator 60 in the state where the rotor magnet 12 is inconsistent with the stator 60, the rotor magnet 12, And the polarity of the stator piece 61 is opposite to that of the stator piece 61 to generate attractive force with respect to the rotor magnet 12.

6, stator pieces (b1 ±, b2 ±, b3 ±) and three rotor magnets (a1, a2, a3) of the three stator b1, b2 and b3 are shown have. In Fig. 6, the left and counterclockwise directions are the moving directions of the rotor magnets a1, a2 and a3. 6, b1-, b2 +, b3-, b3-, and b3- in the upper diagram in which the stator pieces (b1 占 b2 占 b3 占 and rotor magnets a1, a2, (b1-, b2-, b3 +) in Fig. 3 (b) becomes the stator side on the opposite side of the front side and the stator side on the rear side. The first rotor magnet a1 and the third rotor magnet a3 among the rotor magnets (hereinafter referred to as first to third rotary magnets a1, a2 and a3) (a2 +) in the front direction and S pole (a2-) in the rear direction of the second rotor magnet a2, so that the rotor magnet 12 ) Are arranged alternately.

When the rotor magnets a1 to a3 and the stator b1, b2 and b3 coincide with each other when the rotor magnets a1 to a3 rotate left (or counterclockwise) the polarity of the stator pieces b1 ±, b2 ±, b3 ± of the rotor magnets a1 to a3 is determined such that the stator pieces b1 ±, b2 ±, b3 ± have the same polarity as the magnet faces of the facing rotor magnets a1 to a3. Specifically, the front stator piece b1- of the first stator piece b1- facing the first electromagnet a1 has an S pole of the same polarity as the front surface of the first rotor magnet a1, The polarity of the rear stator piece b1 + facing the rear surface of the rotor magnet a1 is adjusted so as to become the N pole. Similarly, the second stator piece b2 占 and the third stator piece b3 占 are also controlled so as to have the same polarity as the front and rear polarities of the coincident rotors a2 and a3. Thereby, a repulsive force is generated between the rotor magnets a1 to a3 and the stator pieces ±, b2 ±, b3 ±, whereby the rotor magnets a1 to a3 obtain rotational power.

On the other hand, when the rotor magnets a1 to a3 and the stator pieces b1 ±, b2 ±, b3 ± are not coincident with each other, the magnet pieces of the rotor magnets a1 to a3 and the stator pieces b1 (B1 ±, b2 ±, b3 ±) are controlled so that the polarities of the stator pieces (b1 ±, b2 ±, b3 ±) are different from each other so that the stator pieces a1 to a3 are provided so that the rotating rotor magnets a1 to a3 are attracted to the stator pieces b1 ±, b2 ±, b3 ± to rotate.

The controller 90 detects the rotation of the rotor 10 by the detector 40 and outputs the magnetic poles of the stator pieces b1 ±, b2 ±, b3 ± during the rotation of the rotor 10 The rotation of the rotor 10 is maintained, accelerated or decelerated.

FIG. 8 is an exemplary view showing a motor device 200 according to a second embodiment of the present invention, and FIG. 9 is an exemplary view showing details of a stator and a rotor according to the second embodiment. The motor device 200 of the second embodiment differs from that of the first embodiment only in the shape of the rotor magnet 212 and the shape of the stator piece 262 corresponding thereto, and a detailed description of the same components will be omitted .

Referring to FIGS. 8 and 9, the rotor magnet 212 of the motor device 200 according to the second embodiment of the present invention is curved and formed into an arc shape as shown in FIG. This shape is a shape when the rotor magnet is cut into an extension line of the circumferential direction of the rotor 11 or when the motor device is viewed from the side. That is, it is formed in a shape protruding in either the front or rear direction and recessed in the other direction.

One of the stator pieces 262 is concave to correspond to the convex portion of the rotor magnet 212 and the other is formed to correspond to the rotor magnet 212 And the convex portion is formed so as to correspond to the concave portion of the concave portion. Even if the rotor magnet 212 is formed into a curved shape, the gap between the surface of the rotor magnet 212 and the surface of the stator piece 262 becomes uniform.

In particular, the rotor magnet 212 according to the second embodiment of the present invention is formed in an arc shape, so that the mechanical rigidity is improved as compared with the first embodiment described above. The width of the magnet surface and the width of the corresponding stator piece 262 are increased, so that the magnetic flux is increased and the output is increased.

10 to 12 are illustrations showing a motor device 300 according to a third embodiment of the present invention. FIG. 10 is a plan view and a side elevational view of the motor device according to the third embodiment, FIG. 12 is an exemplary view showing the stator in more detail. FIG.

10 to 12, the motor device 300 according to the third embodiment of the present invention is different from the above-described embodiment in that the arrangement and shape of the rotor magnet 310 and the stator 360 are different, Which is the same as the first and second embodiments. In the following description of the third embodiment, detailed description of the same components as those of the first and second embodiments will be omitted.

The rotor 310 of the motor device 300 according to the third embodiment is mounted on the front and rear faces of the rotor 311 in a direction perpendicular to the plane of the rotor 311, . This type of coupling of the rotor magnet 312 is shown in Fig. The rotor magnets 312 are provided on the front and rear surfaces of the rotor 311, respectively, and the rotor magnets formed on the same surface are separated from each other by a predetermined distance to be coupled to the rotor 311. The rotor magnet 312a on the front side and the rotor magnet 312b on the rear side are staggered and arranged in a staggered manner as shown in the lower part of Fig.

In addition, the stator 360 is disposed correspondingly to the arrangement of the rotor magnets 312. More specifically, the stator 360 is divided into a front stator 360a and a rear stator 360b. Each of the front stator 360a and the rear stator 360b is disposed at a distance from the rotation itself 311 along the front and rear edges of the rotation itself 311. [ The front stator 360a and the rear stator 360b may be arranged so as to form a stator pair with the rotor 311 interposed therebetween as shown in the bottom of FIG. The front stator 360a and the rear stator 360b may be arranged in a zigzag manner, but the present invention is not limited thereto.

Particularly, in the stator 360 of the third embodiment, the gap between the slits through which the rotor magnet 312 passes, that is, the stator pieces 362a and 362b, is disposed in a direction perpendicular to the surface of the rotation itself 311. [ In the first and second embodiments described above, the gap between the stator pieces 62 and 262 is arranged on the circumferential extension line of the rotation selfs 11 and 211, whereas in the third embodiment, unlike the above-described embodiments, And is disposed in a direction perpendicular to the plane of its own (311). That is, the stator 360 of the third embodiment is formed by extending a pair of stator pieces 362a, 362b from the fixed body 361 toward the rotating body 311, and a pair of opposed stator pieces 362a, 362b are arranged on imaginary ellipses which are concentric with the circumferential surface of the rotation body 311. [ FIG. 12 shows the shape of the stator 360, the intermediate view is a rear view of the stator 360, and the lower end view is a side sectional view. 12, the first stator piece 362a and the second stator piece 362b are elongated from the fixed body 361 and are spaced apart from each other, and a slit through which the rotor magnet 312 can pass . In particular, the stator piece 362 is formed in a curved shape as shown to allow the rotor magnet 312 to pass easily through the stator piece 362. [ The rotor magnet 312 is also formed in such a curved shape that the gap between the rotor magnet 312 and the stator piece 362 is constant even when passing between the stator pieces 362 by rotation . Particularly, since the gap between the rotor magnet 312 and the stator piece 362 can be kept very close, it is possible to prevent the loss of the magnetic force and to improve the output thereof.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, . ≪ / RTI > Accordingly, such modifications are deemed to be within the scope of the present invention, and the scope of the present invention should be determined by the following claims.

10, 310: rotator 11, 311: rotation itself
12, 212, 312: rotor magnet 14: rotor boss
15: circumference 30: axis
40: Te tector 42: Pinwheel
43: optical sensor 60, 360: stator
61: fixed body 62, 262: fixed body
70: coil 90:

Claims (6)

shaft;
The rotation itself being formed in a wheel-like shape through which the shaft is penetrated and which is in the form of a circular plate or a wheel including spokes and rims;
And a pair of front and rear magnetic pole surfaces are formed in a plate shape parallel to the rotation self-surface, the rotor magnet being formed of a plurality of rotor magnets, the rotor magnet being radially spaced apart from the outer circumferential surface or the circumferential surface of the rotation self- And
A stator having a plurality of stator teeth arranged radially apart from each other on the circumferential extension line of the rotation itself and having a fixed body and a pair of stator pieces extending from the fixed body and facing each of the pair of magnetic pole faces; And a motor for driving the motor. The method according to claim 1,
Wherein a surface of the stator that faces the rotor magnet and the rotor magnet is curved. The method according to claim 1,
Wherein a plurality of the rotor magnets are arranged so that the polarities of the pole faces between the neighboring rotor magnets are reversed,
The stator piece
And has the same polarity as the polarity of the pole face when the stator pole and the pole face coincide with each other,
And the polarity is controlled so as to have a polarity opposite to the polarity of the pole face when the stator pole and the pole face are not mismatched. shaft;
The rotation itself being formed in a wheel shape such that the shaft is penetratingly connected and comprising a circular plate or a rim and a spoke;
A rotor magnet coupled to an edge of the front and rear surfaces of the circular plate of the rotation itself or to the front and rear surfaces of the rim and having a pair of front and rear pole faces orthogonal to the rotation inner face; And
A plurality of permanent magnets arranged on the front and rear faces of the circular plate of the rotation itself or facing the front and rear faces of the rim and radially spaced from each other and extending from the fixation itself and the fixation itself and facing each of the pair of pole faces And a stator having a pair of stator pieces. 5. The method of claim 4,
The rotor magnet or the stator
And the position of the rotor magnet or the stator magnet coupled to the front and rear surfaces with the rotation itself interposed therebetween are arranged to be shifted from each other. 5. The method of claim 4,
Wherein a plurality of the rotor magnets are arranged so that the polarities of the pole faces between the neighboring rotor magnets are reversed,
The stator piece
And has the same polarity as the polarity of the pole face when the stator pole and the pole face coincide with each other,
And the polarity is controlled so as to have a polarity opposite to the polarity of the pole face when the stator pole and the pole face are not mismatched.

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