JP2007209186A - Synchronous motor and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a synchronous motor capable of reducing induced voltage strain and cogging torque at the same time that cause variations in the torque of a motor. <P>SOLUTION: The synchronous motor comprises a ring-like core back part 9, a plurality of teeth 2 that protrude radially toward the inside from the core back part 9, a stator core 1a comprising a plurality of slots 4 formed among the teeth 2, a stator 1 which is stored in the slot 4 and comprises a coil 3 wound on the teeth 2, and a rotor 5 which is stored and rotated in the stator 1 with a magnet 6 arranged on the surface. When a gap 10 is formed between the stator 1 and the rotor 5, the length of gap fluctuates in a sinusoidal wave form when the length of the gap 10 in the radial direction is assumed as gap lengths, the number of cycles with which the gap length fluctuates in a sinusoidal wave form agrees with the number of slots 4, and the gap length is a minimum at substantially the center of a part 2a opposite to the rotor of the teeth 2. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a synchronous motor using a magnet for a rotor and a method for manufacturing the synchronous motor.

  In a conventional synchronous motor using a permanent magnet for the field part, winding is applied to the tooth part of the salient pole structure, and magnetic non-uniformity occurs when the permanent magnet moves from the tooth part to the slot opening. Cogging torque is generated, which adversely affects motor performance. Hereinafter, various measures for reducing the cogging torque have been proposed and will be described briefly.

  An armature having a magnetic field portion forming P magnetic poles (where P is an integer of 2 or more), a winding groove and a salient pole around which a plurality of armature windings are wound; One of the field part and the armature is rotated with respect to the other, an auxiliary groove is provided at a position facing the field part of the armature salient pole, and between the armature salient poles. When the order of the fundamental harmonic component of the magnetic inhomogeneity due to the formed winding groove is m (where m is an integer), the basic inhomogeneity of the salient pole part of the armature The order of the harmonic component is K · m (where K is an integer greater than or equal to 2 and when the greatest common divisor of P and m is Q, the greatest common divisor of P / Q and K is P / Q. And a rotating electrical machine configured to be smaller than K have been proposed (see, for example, Patent Document 1).

  In addition, a permanent magnet field magnetized on the even poles, and a plurality of salient poles arranged opposite to the field and an armature having a winding groove formed between the salient poles, And in the rotating electrical machine that rotates either one of the field or the armature with respect to the other, it is made a part facing the field of the salient pole of the armature and at the position of each groove for winding. On the other hand, a rotating electrical machine has been proposed in which a convex portion is provided at a portion shifted by (360 ° / number of field poles or an integral multiple thereof) (for example, see Patent Document 2).

  Further, in a rotating electrical machine including a plurality of salient pole parts and a core iron that forms a groove between the salient pole parts, and a field body, the peripheral surface of the core core on the field body direction side is a salient pole. It is a concavo-convex shape including a portion and a groove, the concavo-convex shape forms a continuous sine wave curve in which valley bottom points and peak vertices alternately appear, and the valley bottom point is located on the direction side away from the field body on the groove center line, A rotating electrical machine has been proposed in which the peak is located at salient poles on both sides of the groove (see, for example, Patent Document 3).

Further, in order to reduce the fluctuation torque of the motor, the tooth portion of the stator core has a predetermined tooth width, and the tooth portion tip portion is formed on the inner diameter side tooth portion up to the opening portion excluding the tooth portion. A part of the tip portion of the tooth portion formed by extending on both sides is cut and removed. Only the tooth tip in the direction of rotation of the rotor is sufficient on one side, but the other tooth tip is also cut so that the rotor can be inserted from either side of the stator when the motor is assembled. . At the tooth tip, the distance from the rotor increases by the amount cut, so that the magnetic resistance at the cut increases, and magnetic flux is concentrated at the tooth tip in the direction of rotation of the rotor. There has been proposed a concentrated winding type brushless DC motor which is averaged without reduction and fluctuations in torque are reduced (see, for example, Patent Document 4).
Japanese Examined Patent Publication No. 58-42707 Japanese Patent Publication No. 2-19695 Japanese Utility Model Publication No. 5-95151 JP 2000-184633 A

  The rotating electrical machine described in Patent Document 1 is effective only in a specific case where the magnetized state of the field part is present as described in Patent Document 2, but when this magnetized state changes, There was a problem that the cogging torque would change.

  Further, as described in Patent Document 3, the rotating electrical machines described in Patent Document 1 and Patent Document 2 have a temporary effect in reducing the cogging torque, but the auxiliary electric device provided in the salient pole portion. In the shape of the groove or convex part, the transition from the outer peripheral surface of the salient pole part to the auxiliary groove or convex part will be formed at a substantially right angle, so the shape change will be severe, magnetic non-uniformity will be large, cogging There was a limit in torque reduction.

  Further, in the rotating electrical machine described in Patent Document 3, the peripheral surface of the salient pole portion of the core core facing the field body direction side has a sinusoidal curve shape. In addition, there are approximately five uneven shapes on the peripheral surface of one salient pole portion facing the field body direction side. The magnetic flux when the permanent magnet passes through the salient pole part has a waveform including harmonics due to the influence of these approximately five uneven shapes, and the induced voltage induced in the winding is distorted. there were.

  Further, the concentrated winding type brushless DC motor described in Patent Document 4 is improved to some extent in the distortion of the induced voltage induced in the winding, but the tip shape of the tooth portion of the stator core is changed to the opening portion excluding the tooth portion. Since the cut portion is provided in the inner diameter side tooth portion up to, the slot opening portion is equivalently widened, and there is a problem that the cogging torque is increased as compared with the case where the gap length is constant.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a synchronous motor that can simultaneously reduce induced voltage distortion and cogging torque, which are causes of motor torque unevenness.

  The synchronous motor according to the present invention includes an annular core back portion, a plurality of teeth portions radially projecting radially inward from the core back portion, and a plurality of slots formed between the teeth portions. A stator core having a stator core, a stator that is housed in a slot and wound around a tooth portion, and a rotor that is housed inside the stator and rotates and has a magnet disposed on the surface thereof. In the gap formed between the rotor and the rotor, when the length in the radial direction of the gap is defined as the gap length, the gap length fluctuates in a sine wave shape, and the number of cycles fluctuating in the sine wave shape of the gap length is the number of slots. And the gap length is minimized at the approximate center of the portion of the teeth portion facing the rotor.

  With the above configuration, the synchronous motor according to the present invention can simultaneously reduce induced voltage distortion and cogging torque, which are causes of motor torque unevenness.

Embodiment 1 FIG.
1 to 10 show the first embodiment. FIG. 1 is a sectional view of the synchronous motor 100, FIG. 2 is a partially enlarged view of FIG. 1, and FIG. 3 is a part of the air gap 10 (one magnetic pole of the rotor 5). 4 is a diagram showing the logarithm), FIG. 4 is a diagram showing the harmonic analysis result of the induced voltage (compare Embodiment 1 and the conventional example), and FIG. 5 is the harmonic analysis result of the cogging torque (this FIG. 6 is a diagram showing a harmonic analysis result of an induced voltage when the sine wave shape is changed, and FIG. 7 is a cogging torque when the sine wave shape is changed. FIG. 8 is a diagram showing the relationship between the harmonic content of the induced voltage and the ratio of the amplitude value of the sine wave to the average gap length, and FIG. 9 is the ratio of the cogging torque (amplitude value). FIG. 10 shows the relationship between the ratio of the amplitude value of the sine wave to the average gap length, and FIG. Motor (rotor A, the rotor B, rotor C) is a diagram showing a magnetic state of.

  The configuration of the synchronous motor 100 will be described with reference to FIGS. 1 and 2. The synchronous motor 100 includes a stator 1 and a rotor 5. 2 is a partially enlarged view of FIG. 1, and FIG. 2 is not particularly described.

  The stator 1 is mainly composed of a stator core 1 a and a winding 3. The stator core 1a has a plurality of tooth portions 2 (12 in the example of FIG. 1) radially projecting radially inside the annular core back portion 9, and a plurality of slots 4 (tooth teeth) between each tooth portion 2. The same number as the portion 2 (12).

  Each tooth part 2 is provided with a winding 3 of a concentrated winding method, and a three-phase connection is made. The winding 3 is inserted into the slot 4 from the slot opening 4 a between the teeth 2.

  Further, although the first embodiment has a feature in the shape of the inner peripheral surface of the tooth portion 2 facing the rotor 2a, the configuration of the rotor 5 will be described first.

  The rotor 5 is a surface magnet arrangement type rotor in which a magnet 6 is arranged on the surface, and includes an annular magnet 6 on the outside of a connecting portion 7 with a shaft. The magnet 6 in FIG. 1 has 8 poles. The connecting portion 7 with the shaft is fitted to the shaft 8.

  There is a gap between the inner peripheral surface of the stator core 1a (also the inner peripheral surface of the opposed portion 2a to the rotor) and the outer peripheral surface of the rotor 5, and this is referred to as a gap 10. The rotor 5 side of the air gap 10 is a smooth circle, but the surface on the stator core 1a side fluctuates in a sine wave shape. Accordingly, if the length of the gap 10 in the radial direction is the gap length, the gap length varies sinusoidally, the number of cycles of the sinusoidal variation coincides with the number of slots 4, and the gap length is equal to the teeth portion. It becomes the minimum in the vicinity of the center of the facing portion 2a facing the two rotors.

  FIG. 3 is a diagram in which the number of pairs of one magnetic pole of the rotor 5 is expanded in order to easily understand the sinusoidal fluctuation of the air gap 10. The number of cycles of sinusoidal variation of the air gap length corresponding to the number of one magnetic pole pair (two poles) of the rotor 5 is three. Here, the average value of the gap length is defined as the average gap length. Further, ½ of the difference between the maximum and minimum of the sinusoidal fluctuation is set as the amplitude value of the sine wave.

  An electromagnetic field analysis was performed on the induced voltage and cogging torque of the winding 3 of the synchronous motor 100 having the above-described configuration by the finite element method. The analysis results will be described below.

  FIG. 4 shows a harmonic analysis result of the induced voltage of the winding 3 of the synchronous motor 100 shown in FIG. For comparison, an analysis result for a case where the gap length is constant is also shown. Generally, the harmonics of the induced voltage of the winding 3 have large fifth and seventh order components that are lower order harmonics. As shown in FIG. 4, the fifth harmonic component having a constant gap length has a content rate of slightly over 3%, whereas the number of cycles of sinusoidal fluctuation of the gap length in the first embodiment. However, when the number of slots 4 is the same and the gap length is minimum in the vicinity of the center of the facing portion 2a of the tooth portion 2 with the rotor, it is reduced to about 2%. In addition, the seventh harmonic component having a constant gap length has a content rate of slightly over 1%, while that of the first embodiment is reduced to less than about 1%.

  FIG. 5 shows a harmonic analysis result of the cogging torque (amplitude value) of the synchronous motor 100 shown in FIG. For comparison, an analysis result for a case where the gap length is constant is also shown. The frequency of the cogging torque is an integral multiple of the least common multiple of the number of slots 4 (12 in FIG. 1) of the stator core 1a and the number of magnetic poles of the rotor 5 (8 in FIG. 1). Therefore, as shown in FIG. 5, cogging torque of harmonic components such as 24th order and 48th order is generated. As shown in FIG. 5, the 24th harmonic component with a constant gap length has a cogging torque amplitude value of about 2.4 [mN · m], whereas the gap of the first embodiment The number of cycles of the sinusoidal variation of the length is the same as the number of the slots 4 and the gap length is minimum in the vicinity of the center of the portion 2a facing the rotor of the tooth portion 2 is about 1.2 [mN Reduce to m]. The 48th-order harmonic component has a constant gap length of about 0.6 [mN · m], whereas that of the first embodiment has about 0.1 [mN · m]. To reduce.

  Next, the number of cycles of the sinusoidal variation of the gap length does not match the number of slots 4, specifically, (N−1), (N + 1), and the gap length of the teeth portion 2 Harmonic analysis of induced voltage and cogging torque is performed in addition to the maximum value in the vicinity of the center of the opposed portion 2a to the rotor (in FIGS. 6 and 7, which will be described below, the number of sine waves is N and the minimum gap position is reversed). It was. The results are shown in FIGS.

  As shown in FIG. 6, when the number of cycles of the sinusoidal variation of the gap length is (N-1) (in FIG. 6, sine wave number = N-1), the fifth and seventh harmonics of the induced voltage. The component is substantially equal to or larger than a constant gap length. Further, the one having the largest gap length in the vicinity of the center of the portion 2a facing the rotor of the tooth portion 2 (in FIG. 6, sine wave number = N, opposite to the smallest gap position) is the fifth and seventh harmonics of the induced voltage. Components are larger than those with a constant void length.

  As shown in FIG. 7, when the number of cycles of sinusoidal fluctuation of the gap length is (N−1) (in FIG. 7, the number of sine waves = N−1), the cogging torque amplitude value is 24th order, 48th. The second harmonic component is substantially equal to or larger than that having a constant gap length. In addition, the gap length that is maximum near the center of the portion 2a facing the rotor of the tooth portion 2 (in FIG. 7, the sine wave number = N, the gap minimum position reverse) is the 24th and 48th amplitude values of the cogging torque. The second harmonic component is larger than that having a constant gap length.

  Furthermore, the relationship between the ratio of the amplitude value of the sine wave to the average gap length and the ratio of the harmonic content of the induced voltage and the cogging torque (amplitude value) was analyzed. The results are shown in FIGS. In both figures, three types of rotors 5 (rotor A, rotor B, and rotor C) in which the magnetizing waveform of the magnet 6 is changed are analyzed as parameters (see FIG. 10).

  As shown in FIG. 8, when the harmonic content of the induced voltage when the gap length is constant is 1, and the ratio of the amplitude value of the sine wave to the average gap length increases, the harmonic content of the induced voltage Becomes smaller than 1 for a while. For example, when the ratio of the amplitude value of the sine wave to the average gap length is 50%, the harmonic content of the induced voltage is about 0.7.

  As shown in FIG. 9, when the cogging torque (amplitude value) when the gap length is constant is 1, the ratio of the amplitude value of the sine wave to the average gap length is 10% and the cogging torque is less than 0.8. When the ratio of the amplitude value of the sine wave to the average gap length is about 35%, the cogging torque becomes minimum (about 0.4), and then increases, and about 50%, which is about the same as when the gap length is constant. If it exceeds 50%, it will increase rapidly.

  Therefore, the ratio of the amplitude value of the sine wave with respect to the average gap length that can reduce both the harmonic content of the induced voltage and the cogging torque as compared with the case where the gap length is constant is 10 to 50%.

  As shown in FIGS. 8 and 9, the ratio of the amplitude value of the sine wave to the average gap length is 10 to 50% regardless of the magnetized state of the magnet 6, and both the harmonic content of the induced voltage and the cogging torque Can be reduced as compared with the case where the gap length is constant.

  It is confirmed by analysis that the same effect can be obtained when the magnet 6 is not polar anisotropy but parallel magnetized (the direction of the magnetic flux is parallel) or radial magnetized (the direction of the magnetic flux is radial). is made of.

Embodiment 2. FIG.
FIG. 11 is a partial cross-sectional view of the synchronous motor 200 showing the second embodiment. The synchronous motor 200 shown in FIG. 11 is different from that in FIG. 1 in the shape of the inner peripheral surface of the facing portion 2a of the teeth portion 2 of the stator core 1a facing the rotor. As shown in FIG. 11, a protrusion 11 that protrudes toward the rotor 5 is provided near the center of the tooth portion 2. Moreover, it has the notch part 12 in the surrounding surface at the side of the rotor 5 of the part protruded in the circumferential direction both sides of the opposing part 2a with the rotor of the teeth part 2. As shown in FIG. The protrusion 11 and the notch 12 make the variation in the gap length substantially sinusoidal.

  In the above-described shape, the gap length fluctuates in a substantially sine wave shape as in the first embodiment, the number of cycles of the sine wave fluctuation matches the number of slots 4, and the gap length is the rotor of the tooth portion 2. Near the center of the facing portion 2a.

  Therefore, as in the first embodiment, there is an effect that both the harmonic content of the induced voltage and the cogging torque can be simultaneously reduced.

  Further, an arc portion 13 concentric with the rotor is provided between the protrusion 11 and the notch 12. The arc portion 13 concentric with the rotor corresponds to the inner peripheral surface of the stator core 1a when the gap length is constant. Therefore, there is an effect that the dimensions of the stator core 1a can be easily managed.

Embodiment 3 FIG.
FIGS. 12 and 13 are diagrams showing the third embodiment, FIG. 12 is a diagram showing a manufacturing process of the stator core 1a, and FIG. 13 is a diagram showing a change in cogging torque due to a difference in the lamination method of the stator core 1a.

  With reference to FIG. 12, the lamination procedure of the stator core 1a will be described.

  In STEP1, the core is punched out of the non-oriented electrical steel sheet by pressing.

  In STEP2, the punched core is divided into several blocks.

  In STEP 3, the second block is rotated 360 ° / integer multiple of the number of slots with respect to the first block, and is added to the first block. This is to make the positions of the teeth portions 2 coincide when rotated.

  In STEP 4, the third block is rotated 360 ° / integer multiple of the number of slots with respect to the second block, and is added to the second block. At this time, it is rotated in the same direction as STEP3.

  In STEP5, all blocks are stacked in the same manner.

  In STEP 6, the stacked core is fixed by caulking or welding.

  In STEP 7, the stator core 1a is completed.

  The number of cores to be stacked is preferably an integer multiple of the number of slots / 2 if the number of slots is an even number, and is preferably an integer multiple of the number of slots if the number of slots is an odd number.

  Effects obtained by manufacturing the stator core 1a as described above will be described below.

  Non-oriented electrical steel sheets are characterized in that there is no anisotropy in their magnetic properties. That is, the relative permeability is uniform regardless of the orientation used. However, actually, it has a slight magnetic anisotropy in the rolling direction of the roll. In particular, the higher the grade of non-oriented electrical steel sheet, the greater the difference in magnetic anisotropy.

  As shown in FIG. 13, the stator core 1 a in which cores having magnetic anisotropy are stacked in the same direction (conventional core in FIG. 13) generates cogging torque having the same number of harmonic components as the number of magnetic poles of the rotor 5. This is because it is synonymous with having saliency in one direction.

  Further, as in the second embodiment, in the case where the protruding portion 11 is provided in the portion 2a facing the rotor, variation in the size of the protruding portion 11 may lead to an increase in cogging torque. When the protrusion 11 of one tooth portion 2 is larger or smaller than the protrusion 11 of the other tooth portion 2, a cogging torque having the same number of harmonic components as the number of magnetic poles of the rotor 5 is also generated. Become. Further, not only one tooth portion 2 but also the cogging torque having the same number of harmonic components as the number of magnetic poles of the rotor 5 is generated even when the dimensions of the protrusions 11 of the plurality of tooth portions 2 vary. In particular, when the dimension of the protrusion 11 of the in-phase teeth portion 2 is larger or smaller than the other among the three phases, the cogging torque having the same number of harmonic components as the number of magnetic poles of the rotor 5 becomes larger.

  That is, the stator core 1a manufactured according to the third embodiment has an imbalance (saliency) in magnetic characteristics due to anisotropy of the non-oriented electrical steel sheet, and a protrusion when the protrusion 11 is provided on the tooth portion 2. Thus, the unbalance of the magnetic characteristics due to the dimensional variation of 11 can be canceled, and the cogging torque having the same number of harmonic components as the number of magnetic poles of the rotor 5 can be reduced.

Embodiment 4 FIG.
14 and 15 show the fourth embodiment, FIG. 14 is a partial cross-sectional view of the synchronous motor 300, and FIG. 15 shows a torque waveform.

  In the synchronous motor 300 shown in FIG. 14, the facing portions 2 a of the teeth portions 2 facing the rotor are all connected in the circumferential direction. That is, the slot opening 4a is not provided in the portion 2a facing the rotor of the stator core 1a. The core back portion 9 is provided with a slot opening 9a. The winding 3 is inserted from a slot opening 9 a provided in the core back portion 9.

  In the air gap 10 between the stator 1 and the rotor 5, the air gap length fluctuates in a sinusoidal manner as in the first embodiment, the number of cycles of the sinusoidal fluctuation coincides with the number of slots 4, and the air gap The length is minimum in the vicinity of the center of the portion 2a facing the rotor of the tooth portion 2.

  Although not shown in the drawings, as in the second embodiment, there is a protruding portion 11 that protrudes toward the rotor 5 near the center of the tooth portion 2, and the circumferential direction of the portion 2 a facing the rotor of the tooth portion 2. It is also possible to have a notch portion 12 on the peripheral surface of the rotor 5 side of the portion projecting on both sides, and to make the fluctuation of the gap length substantially sinusoidal by the projection portion 11 and the notch portion 12.

  With this structure, as shown in FIG. 15, the magnetic non-uniformity generated in the slot opening 4a is less likely to occur, and the occurrence of cogging torque and torque unevenness can be suppressed.

FIG. 3 is a diagram illustrating the first embodiment and is a cross-sectional view of the synchronous motor 100. FIG. 2 shows the first embodiment, and is a partially enlarged view of FIG. 1. FIG. 5 is a diagram showing the first embodiment, and is a diagram showing a part of the air gap 10 (one magnetic pole pair of the rotor 5) in a straight line. It is a figure which shows Embodiment 1, and is a figure which shows the harmonic analysis result (this Embodiment 1 is compared with a prior art example) of an induced voltage. It is a figure which shows Embodiment 1, and is a figure which shows the harmonic analysis result (this Embodiment 1 and a prior art example are compared) of a cogging torque. It is a figure which shows Embodiment 1, and is a figure which shows the harmonic analysis result of the induced voltage at the time of changing a sine wave shape. It is a figure which shows Embodiment 1, and is a figure which shows the harmonic analysis result of a cogging torque at the time of changing a sine wave shape. It is a figure which shows Embodiment 1, and is a figure which shows the relationship between the harmonic content of an induced voltage, and the ratio of the amplitude value of a sine wave with respect to average space | gap length. FIG. 5 is a diagram illustrating the first embodiment and is a diagram illustrating a relationship between a ratio of cogging torque (amplitude value) and a ratio of an amplitude value of a sine wave to an average gap length. FIG. 10 is a diagram illustrating the first embodiment, and is a diagram illustrating magnetization states of the three types of rotors (rotor A, rotor B, and rotor C) illustrated in FIGS. 8 and 9. FIG. 10 is a diagram showing the second embodiment and is a partial cross-sectional view of the synchronous motor 200. FIG. It is a figure which shows Embodiment 3, and is a figure which shows the manufacturing process of the stator core 1a. It is a figure which shows Embodiment 3, and is a figure which shows the change of the cogging torque by the difference in the lamination | stacking method of the stator core 1a. FIG. 10 is a diagram illustrating the fourth embodiment, and is a partial cross-sectional view of the synchronous motor 300. It is a figure which shows Embodiment 4, and is a figure which shows a torque waveform.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Stator, 1a Stator core, 2 teeth part, 2a Opposite part with rotor, 3 winding, 4 slot, 4a slot opening part, 5 rotor, 6 magnet, 7 Axis connection part, 8 axis, 9 core back part, 9a Slot opening, 10 gap, 11 protrusion, 12 notch, 13 arc portion concentric with rotor, 100 synchronous motor, 200 synchronous motor, 300 synchronous motor.

Claims (7)

A stator core having an annular core back portion, a plurality of teeth portions radially projecting radially inward from the core back portion, and a plurality of slots formed between the teeth portions; And a stator having a winding wound around the teeth portion,
A rotor that is housed inside the stator and rotates, and a magnet is disposed on the surface;
In the air gap formed between the stator and the rotor, when the length in the radial direction of the air gap is the air gap length, the air gap length fluctuates in a sine wave shape and the cycle fluctuates in a sine wave shape of the air gap length. The number of slots is the same as the number of slots, and the gap length is minimized at the approximate center of the teeth portion facing the rotor. A stator core having an annular core back portion, a plurality of teeth portions radially projecting radially inward from the core back portion, and a plurality of slots formed between the teeth portions; And a stator having a winding wound around the teeth portion,
A rotor that is housed inside the stator and rotates, and a magnet is disposed on the surface;
The teeth portion has a protrusion that protrudes toward the rotor at a substantially central portion, and a portion of the teeth portion that protrudes on both sides in the circumferential direction of the portion facing the rotor, on the circumferential surface on the rotor side. Has a notch,
In the air gap formed between the stator and the rotor, when the length in the radial direction of the air gap is the air gap length, the air gap length varies substantially sinusoidally due to the protrusion and the notch. A synchronous motor characterized by   The synchronous motor according to claim 2, further comprising an arc portion concentric with the rotor between the protrusion and the notch.   4. The synchronous motor according to claim 1, wherein an opening of the slot is provided in the core back portion, and portions of the teeth portion facing the rotor are connected to each other. In the manufacturing method of the synchronous motor according to any one of claims 1 to 4,
When the non-oriented electrical steel sheet is laminated by punching the non-oriented electrical steel sheet into the stator core shape, the stator core is laminated so that the rolling direction of the non-oriented electrical steel sheet changes in the stacking direction of the stator core. A method for manufacturing an electric motor.   6. The stator core according to claim 5, wherein when the non-oriented electrical steel sheet is punched into a shape of the stator core and stacked, the non-oriented electrical steel sheet is rotated by a predetermined angle for each predetermined number of sheets. A method for manufacturing a synchronous motor.   When the number of slots is an even number, the number of blocks of the non-oriented electrical steel sheet to be rotated and laminated is an integral multiple of 1/2 of the number of slots, and the number of slots when the number of slots is an odd number. The method of manufacturing a synchronous motor according to claim 6, wherein an integer multiple of the synchronous motor is set.

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