JP2010088169A - Electric motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric motor which can accurately detect a position of a zero cross generated by a change of the magnetic flux of a permanent magnet. <P>SOLUTION: First slots 31a to 31i are arranged so as to orthogonally cross with respect to the radial direction of a rotor 3, second slots 32a to 32i are arranged from both ends of the first slots 31a to 31i toward the external peripheral face of the rotor 3 along the radial direction of the rotor, air gaps 33, 34 are formed along the external peripheral face of the rotor from ends of the second slots 32a to 32i, and the magnetic flux of the permanent magnet is efficiently concentrated on the face of a magnetic pole. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a magnet-embedded electric motor in which a permanent magnet is embedded in a rotor, and more particularly to an electric motor that detects a rotor position using a zero cross generated by a change in magnetic flux of a permanent magnet.

  A brushless DC motor is used for an electric motor employed in a compressor or the like for higher efficiency. Conventionally, brushless DC motors have used SPM type (surface magnet affixed type) in which a permanent magnet bonded to the surface of the rotor is covered with a metal tube such as stainless steel. At present, the more efficient IPM type (embedded magnet type) has become mainstream (see, for example, Patent Document 1).

  The IPM type motor can be driven more efficiently by synergistically working with the magnet torque that works in synchronism with the permanent magnet M and the reluctance torque obtained by the salient pole ratio generated by the slit part in which the permanent magnet is embedded. It is.

  The rotor of the IPM type motor is arranged so that the magnetic pole surface faces in the circumferential direction between adjacent magnetic poles, thereby effectively utilizing the magnetic flux generated by the permanent magnet to reduce the total amount of magnets while reducing the total amount of magnets. Conversion efficiency can be improved.

  In addition, the permanent magnet synchronous motor including the IPM type can be driven without a sensor, which eliminates the need for an angle sensor, thereby achieving an improvement in reliability and a reduction in cost.

  In order to drive without detecting the position (sensing) of the rotor, it is necessary to accurately detect the relative electrical angle between the rotor and the stator. As a typical sensorless drive method, a method of detecting “zero cross” that is a point at which the induced voltage becomes zero, a method of using a neutral point voltage, a method of using an estimated induced voltage of a dq rotating coordinate model, etc. There is.

Japanese Patent Laid-Open No. 2005-27422

  However, when detecting the zero cross of the induced voltage to detect the rotor position of the IPM type motor, if the induced voltage waveform undulates near the zero cross, the zero cross of the induced voltage cannot be detected accurately, and the rotor position is erroneously detected. There was a fear.

  Accordingly, the present invention has been made to solve the above-described problem, and an object of the present invention is to provide an electric motor capable of detecting a zero cross of an induced voltage caused by a change in magnetic flux of a permanent magnet with high accuracy. .

  In order to achieve the above-described object, the present invention has several features described below. The invention described in claim 1 includes a stator that generates a rotating magnetic field, and a rotor in which a permanent magnet is embedded, and is disposed coaxially on the inner diameter side of the stator. A first slot into which the permanent magnet is inserted; and a radial slot extending from both ends of the first slot toward the outer circumferential surface of the rotor. And a gap is provided along the outer circumferential surface of the rotor from the end of the second slot. The gap is provided in the second slot. A first gap that extends in the circumferential direction of the rotor along the outer circumferential surface of the rotor from the end of the rotor, and a circle of the rotor along the outer circumferential surface of the rotor from the end of the first gap Second arranged in the circumferential direction And the number of teeth of the stator is 3n, the number of magnetic poles of the rotor is 2n (n is a natural number), and the angle formed between the magnetic pole inner side ends of the second gap portion Is about 90 ° in electrical angle, a second bridging portion is provided between the first gap portion and the second gap portion, and the second bridging portions provided on both ends of the magnetic poles are centered on the rotor. When the angle formed with respect to is α, 126 ° <α <144 ° (electrical angle).

  The invention described in claim 2 includes a stator that generates a rotating magnetic field, and a rotor in which a permanent magnet is embedded, and is disposed coaxially on the inner diameter side of the stator. A first slot into which the permanent magnet is inserted; and a radial slot extending from both ends of the first slot toward the outer circumferential surface of the rotor. And a second slot into which a permanent magnet is inserted, and a void portion is provided along an outer peripheral surface of the rotor from an end portion of the second slot. Includes a first gap portion extending in the circumferential direction of the rotor along the outer circumferential surface side of the rotor from an end portion of the second slot, and an outer circumferential surface of the rotor from the end portion of the first gap portion. Along the row above And the number of teeth of the stator is 3n, the number of magnetic poles of the rotor is 2n (n is a natural number), and the second gap The angle between the magnetic pole center side ends of the rotor with respect to the rotor center is about 90 ° in electrical angle, and a second bridging portion is provided between the first gap portion and the second gap portion, When the angle between the second bridging portions provided on the rotor and the center of the rotor is α, 108 ° <α <144 ° (electrical angle).

  According to invention of Claim 1, it arrange | positions so that it may orthogonally cross with respect to the radial direction of a rotor, a permanent magnet is inserted in an inside, Along the radial direction of a rotor from the both ends of a 1st slot A second slot disposed toward the outer peripheral surface of the rotor is provided, and a gap is provided from the end of the second slot along the outer peripheral surface of the rotor. According to this, by providing the second slot, magnetic flux bridging of the permanent magnet can be prevented, and further, the angle formed by the magnetic pole center side ends of the second gap is 90 ° in terms of electrical angle. The fundamental wave component contained in the magnetic flux waveform on the surface can be increased, and the efficiency can be further increased. In addition, when the angle formed between the second bridging portions provided on both ends of the magnetic poles with respect to the rotor center is α, 126 ° <α <144 ° (electrical angle) is established, so that the second gap portion is Even if it is provided, the induced voltage waveform of the rotor does not wave at zero crossing, and the position of the rotor can be detected accurately.

  According to the second aspect of the present invention, in the electric motor in which the permanent magnet is provided in the second slot in addition to the first slot in order to increase the torque, the second bridging provided on both ends of the magnetic pole is provided. By setting the angle α between the portions to the rotor center to be 108 ° <α <144 °, the induced voltage waveform of the rotor in which the permanent magnet is inserted into the second slot does not undulate near the zero cross, The rotor position can be accurately detected.

  Next, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited thereto. FIG. 1 is a cross-sectional view of an electric motor according to an embodiment of the present invention, FIG. 2 is an enlarged cross-sectional view of a rotor, and FIG. 3 is an enlarged cross-sectional view further enlarging a main part of the rotor. FIGS. 4A to 4I are enlarged cross-sectional views of main parts showing the shape of the gaps of the rotors of Examples 1 to 9, and FIGS. 5A to 5I are permanently attached to the second slot. It is a graph which shows the relationship between the interlinkage magnetic flux (phi) u of U phase and the induced voltage V (micro | micron | mu) in the electrical angle (theta) m of each Example and comparative example of the state which inserted the magnet.

  FIGS. 6A to 6I are graphs showing the relationship between the U-phase interlinkage magnetic flux φμ and the induced voltage Vμ at each electrical angle θm in each Example and Comparative Example when no permanent magnet is inserted in the second slot. It is. FIGS. 7A to 7C are magnetic flux diagrams at each mechanical angle in a state in which a permanent magnet is inserted into the second slot of Comparative Example 1. FIGS. 9 is a magnetic flux diagram at each mechanical angle in a state where a permanent magnet is not inserted into the second slot of FIGS. 9A to 9C, and FIGS. 9A to 9C are diagrams illustrating a state where a permanent magnet is inserted into the second slot of Comparative Example 1. It is a magnetic flux diagram in a mechanical angle. FIGS. 10A to 10C are magnetic flux diagrams at each mechanical angle in a state in which the permanent magnet is not inserted into the second slot of the first embodiment.

  As shown in FIG. 1, the electric motor 1 is an inner rotor type synchronous motor that includes a cylindrical stator 2 and a rotor 3 that is coaxially disposed along the inner diameter of the stator 2. The rotation shaft 4 is integrally provided at the center of the.

  The stator 2 has nine-pole tooth portions 21a to 21i, and a coil (not shown) is wound around the outer periphery of each of the tooth portions 21a to 21i. In the present invention, the specific configuration of the stator 2 is arbitrary, and the specification is not particularly limited as long as it functions as a synchronous motor.

  The rotor according to the present invention will be described in detail with reference to FIG. The rotor 3 has a cylindrical shape formed by laminating a plurality of electromagnetic steel plates along the axial direction of the rotary shaft 4, and is provided with six first slots 31a to 31f penetrating along the axial direction.

  The first slots 31a to 31f each have a rectangular shape that is orthogonal to the radial direction of the rotor 3, and are arranged in a hexagonal shape so that the end portions face each other on a concentric circle with the rotation axis 4 as the center. ing. Permanent magnets 51a to 51f are inserted into the first slots 31a to 31f.

  The rotor 3 further includes six second slots 32a to 32f extending from the end portions of the first slots 31a to 31f to the outer peripheral side of the rotor 3. The second slots 32a to 32f are made of through holes formed in a rectangular shape along the radial direction of the rotor 3, and permanent magnets 52a to 52f are also inserted into the inside of the through holes to form a six-pole rotor.

  Thereby, the permanent magnets 51a to 51f inserted into the first slots 31a to 31f and the permanent magnets 52a to 52f inserted into the second slots 32a to 32f are formed in a bathtub shape for each magnetic pole. Are arranged as follows.

  The permanent magnets 51a to 51f (52a to 52f) are each composed of two plate magnets having the same shape. This plate-like magnet is formed in a rectangular shape having a long side and a short side in cross section by a plane perpendicular to the rotor rotation axis.

  The permanent magnets 51 a to 51 f are configured by arranging the short sides of two plate magnets so as to be adjacent to each other in the circumferential direction of the rotor 3. Further, the permanent magnets 52a to 52f are arranged so that the long sides of the two plate-shaped magnets are adjacent to each other in the circumferential direction of the rotor 3, and at intervals of a predetermined angle along the radial direction of the rotor. Then, it arrange | positions at the mechanical angle 60 degree space | interval.

  According to this, since the permanent magnets 51a to 51f (52a to 52f) are divided, not only the generation of eddy currents is reduced, but also the long sides are arranged adjacent to each other to thereby increase the thickness of the magnet. Becomes larger and harder to demagnetize. Furthermore, it is not necessary to prepare a magnet having a different shape for each slot shape, and the production cost can be reduced. In addition, the specific material, shape, etc. of permanent magnet 51a-51f (52a-52f) of this invention are not restricted to this, It can change suitably.

  In this example, the permanent magnets 52a to 52f are inserted into the second slots 32a to 32f, respectively, but without inserting the permanent magnets 52a to 52f, the second slots 32a to 32f are left as gaps, It may be a flux barrier.

  In the rotor 3, a first gap 33 is formed along the circumferential direction from the end of each of the second slots 32a to 32f. Hereinafter, the first gap portion 33 formed in the vicinity of the second slot 32a will be described as an example with reference to FIG.

  The first gap portion 33 is disposed so as to sandwich the first bridging portion 35 at a predetermined interval from the side surface on the front end side of the second slot 32 a, and is formed in an elongated slit shape along the circumferential direction of the rotor 3. Yes. The first gap portion 33 is a through-hole penetrating along the axial direction of the rotor 3 and is a nonmagnetic flux barrier that hardly allows magnetic flux to pass through.

  On the distal end side of the first gap portion 32, a second gap portion 34 is further provided with the second bridge portion 36 sandwiched by a predetermined interval. The second gap portion 34 is a through hole formed in an arc shape having the same curvature as the first gap portion 33, and is formed in an elongated slit shape along the circumferential direction of the rotor 3. The second gap 34 is also a nonmagnetic flux barrier that hardly allows magnetic flux to pass through.

  Since the rotor 3 has the above-described configuration, the second gap portion 34 is disposed on the outer peripheral side of the rotor magnetic pole 37 so as to face the circumferential direction. Here, the angle formed by the side end portions of the second gap portion 34 at the center of the rotor magnetic pole 37 with respect to the rotor rotation axis is 90 ° in electrical angle. Thereby, the fundamental wave component contained in the surface magnetic flux generated on the rotor surface is increased, and the efficiency of the motor can be improved.

    In the present embodiment, the radial width of the first bridging portion 35 and the second bridging portion 36 is about 1.5 times the thickness of the electromagnetic steel sheet. However, this width can be set as appropriate as long as the magnetic field lines coming out from the N pole side of the magnetic flux of the permanent magnet 5 embedded in the rotor 3 do not increase the amount of magnetic flux (wraparound) that closes in the rotor core without going through the stator. Yes, it is not limited to this width.

  More preferably, it is preferable that the radial width and the circumferential width of the first bridging portion 35 and the second bridging portion 36 are designed so that the circumferential width is larger than the radial width. If it does in this way, when punching out a rotor core from an electromagnetic steel plate, the intensity of the 2nd bridge part 34 pinched by the 1st and 2nd crevice parts 35 and 36 can be made higher.

  Next, specific examples will be described together with comparative examples. After laminating the magnetic steel sheets punched into the shapes of Examples 1 to 5 and Comparative Examples 1 to 4 along the axial direction, permanent magnets are inserted into the first slots to produce rotors. The rotors of Examples 1 to 5 and Comparative Examples 1 to 4 are coaxially attached to a stator prepared in advance, and various drive devices are incorporated to produce an electric motor.

  4 (a) to 4 (i) are cross-sectional views showing the main parts of the rotors of the examples and comparative examples. Below, the shape of the rotor of Examples 1-5 and Comparative Examples 1-4 is shown. Here, α represents an angle formed by the second bridging portions provided on both sides in the circumferential direction of the rotor magnetic pole 37 with respect to the rotor center. More specifically, α represents an angle formed by the contact points of the second bridge portion and the first gap portion with respect to the rotor center (see FIG. 2).

<< Example 1 >> Second bridging portion: α = 138 °
Example 2 Second bridging portion: α = 132 °
Example 3 Second bridging portion: α = 126 °
Example 4 Second bridging portion: α = 120 °
<< Example 5 >> Second bridging portion: α = 114 °
<Comparative example 1> No second bridging part <Comparative example 2> Second bridging part: α = 144 °
<Comparative Example 3> Second bridging portion: α = 108 °
<Comparative example 4> Second bridging portion: α = 102 °

  The produced motor is driven, and there are two patterns (18 types in total) when the permanent magnet is inserted into the second slot 34 of each of the motors of Examples 1 to 5 and Comparative Examples 1 to 4 and not inserted. Calculate the voltage and flux linkage at each electrical angle of the motor. The calculation results when a permanent magnet is inserted into the second slot 34 are shown in FIGS. 6A to 6I show the measurement results when the permanent magnet is not inserted.

  According to this, when a permanent magnet is inserted into the second slot 34, the angle α formed by the second bridging portions is in the range inside the comparative examples 2 and 3, that is, the embodiment 1 (FIG. 4A). ) To Example 5 (FIG. 4 (e)) under the conditions (108 [deg.] <[Alpha] <144 [deg.]), The linkage of the U phase at the position ([theta] m = 150 [deg.]) Where the rotor magnetic pole 37 and the stator teeth (U phase) are directly opposed The magnetic flux φμ becomes a sine waveform, and a beautiful peak appears.

  That is, φμ increases and decreases monotonously around the position (θm = 150 °) where the rotor magnetic pole 37 and the stator teeth (U-phase) face each other. Therefore, the point (zero cross) at which the induced voltage Vμ represented by the amount of change (dμ / dt) in the flux linkage is zero is only one point at θm = 150 ° at which φμ is maximum. Accordingly, the rotor position can be detected by detecting the zero cross of the induced voltage without detecting the induced voltage waveform undulating near the zero cross.

  When the permanent magnet is not inserted in the second slot 34, the angle α formed by the second bridging portions is in the range of 126 ° <α <144 °, that is, Example 1 (FIG. 6A) and the implementation. Under the conditions of Example 2 (FIG. 6B), the interlinkage magnetic flux φμ at the position (θm = 150 °) where the rotor magnetic pole 37 and the stator teeth (U phase) face each other becomes a sine wave, and a beautiful peak appears. Note that the reason why the range α becomes smaller when no permanent magnet is inserted in the second slot will be described later.

  Next, the flow of the magnetic flux lines of the electric motor of the present invention around θm = 150 ° will be examined with reference to FIGS. 7 (a) to 7 (c) show an electrical angle of ± 9 from the position where the rotor magnetic pole 37 and the stator teeth shown in FIG. 7 (b) face each other when the permanent magnet is inserted into the second slot 34 of Comparative Example 1. FIG. 4 is a magnetic flux diagram at a position of ° (that is, θm = 141 °, 150 °, 159 °).

  According to this, out of the magnetic flux flowing through the rotor magnetic pole 37 at the position of θm = 141 ° (FIG. 7A), the magnetic flux flowing in the vicinity of the magnetic pole center side end 341 of the second gap portion 34 on the V phase side. A part flows into the V phase, but all of the magnetic flux passing through the vicinity of the magnetic pole center side end portion 341 of the second gap 34 on the W phase side flows into the U phase.

  Next, at the position of θm = 150 ° (electrical angle 0 °: FIG. 7B), a part of the magnetic flux flowing in the vicinity of the magnetic pole center side end portion 341 of the second gap portion 34 on the V phase side is θm As in the case of = 141 °, it flows into the V phase, and part of the magnetic flux flowing in the vicinity of the magnetic pole center side end portion 341 of the second gap portion 34 on the W phase side also flows into the W phase. For this reason, the amount of magnetic flux flowing into the U phase decreases.

  Next, at the position of θm = 159 ° (FIG. 7C), all of the magnetic flux flowing in the vicinity of the magnetic pole center side end portion 341 of the second gap portion 34 on the V phase side flows into the U phase. A part of the magnetic flux flowing in the vicinity of the magnetic pole center side end portion 341 of the second gap portion 34 on the W phase side flows into the W phase in the same manner as when θm = 150 °.

  Therefore, when θm = 150 °, the amount of magnetic flux φμ flowing into the U-phase decreases, and the peak of φμ at the directly facing position does not appear. Since the peak of φμ appears before and after θm = 150 °, Vμ, which is the deformation amount of φμ, becomes zero at three points before and after θm = 150 °. Therefore, even if the point at which the induced voltage becomes zero is detected, the induced voltage waveform undulates and the position of the rotor cannot be accurately detected.

  On the other hand, FIGS. 8A to 8C show ± 9 ° from the position where the rotor magnetic pole 37 and the stator teeth face each other when the permanent magnet is inserted into the second slot of the third embodiment (α = 126 °). It is a magnetic flux diagram of θm = 141 °, 150 °, 159 °.

  According to this, at the position of θm = 141 ° (FIG. 8A), a part of the magnetic flux passing through the vicinity of the magnetic flux center side end portion 341 of the second gap portion 34 on the V phase side and the first gap portion 33. And the magnetic flux flowing through the second bridging portion 35 between the second gap portion flows in the V phase. Similarly, at θm = 159 ° (FIG. 8C), a part of the magnetic flux passing through the vicinity of the magnetic pole center side end portion 341 of the second bridging portion 34 on the W phase side and the second bridging portion 35 flow. Magnetic flux flows in the W phase.

  On the other hand, at the position where the rotor magnetic pole 37 and the stator teeth face each other (θm = 150 °: FIG. 9B), the end on the magnetic pole center side of the second gap portion 34 on both the V-phase side and the W-phase side. The magnetic flux passing through the vicinity of the portion 341 flows into the opposite magnetic pole face (U phase), and the magnetic flux does not leak to the adjacent W and V phases. Therefore, since the peak of the magnetic flux amount φμ appears at one point of θm = 150 °, the position of the rotor can be detected by detecting the zero cross of the induced voltage. As in the case of the third embodiment, when a permanent magnet is inserted into the second slot, the angle α formed by the second bridging portions is θm = 150 ° within the range of the first to fifth embodiments. The peak of the magnetic flux amount appears at one point, and the zero cross of the induced voltage becomes one point.

  10A to 10C, the rotor magnetic pole 37 in the state where the permanent magnet is not inserted into the second slot of the first embodiment (α = 138 °) and the stator teeth around which the U-phase is wound face each other. It is a magnetic flux diagram of ± 9 ° from the position. As can be seen from FIG. 10, when FIG. 10B, that is, when the rotor magnetic pole 37 and the U phase face each other, the amount of magnetic flux flowing into the U phase becomes the maximum, so that the induced voltage near θm = 150 ° The zero crossing can be defined as one point. Here, the reason why the induced voltage waveform starts to wave and the range of α becomes narrow when no magnet is inserted into the second slot will be described below. That is, when the permanent magnet is not inserted into the second slot, there is no magnet between the poles, so the magnetic flux density at the rotor magnetic pole 37 is lower than that of “with magnet”, and the magnetic flux easily passes through the magnetic pole center side. Become.

  Therefore, in the position of θm = 141 ° or 159 ° than in the case of “with magnet”, if it is not easy to pass the magnetic flux that leads to the V phase and the W phase through the second bridge portion, the position of θm = 150 °. φμ does not peak. In order for the magnetic flux to easily flow through the second bridge portion to the V phase or the W phase, it is necessary to bring the second bridge portion close to the V phase and the W phase. Therefore, the range of α is narrowed.

  The electric motor 1 of the present invention has been described by taking an example designed for a compressor (compressor) of an air conditioner. However, if the electric motor 1 has the above-described basic form, it can be used for other purposes. The overall size, shape, etc. may be arbitrary according to the specifications. In this embodiment, the number of slots in the stator is 9 and the number of poles in the rotor is 6. However, the present invention is not limited to this, and can be applied to an electric motor that satisfies the number of slots / number of rotor poles = 3/2. It is.

Sectional drawing of the electric motor which concerns on one Embodiment of this invention. The expanded sectional view of the rotor of the said embodiment. The expanded sectional view which expanded the principal part of the rotor further. (A)-(i) is principal part expanded sectional drawing which shows the shape of the space | gap part of the rotor of each Examples 1-5 and Comparative Examples 1-4. (A)-(i) The graph which shows the relationship between the electrical angle of the comparative example 1 of the state which inserted the permanent magnet in the 2nd slot, and the voltage and the flux linkage. (A)-(i) is a graph which shows the relationship between the electrical angle of each Example and a comparative example, voltage, and a linkage flux in case the permanent magnet is not inserted in the 2nd slot. (A)-(c) is a magnetic flux diagram in each mechanical angle of the state which inserted the permanent magnet in the 2nd slot of the comparative example 1. FIG. (A)-(c) is a magnetic flux diagram in each mechanical angle in the state where the permanent magnet is not inserted in the second slot of Comparative Example 1. (A)-(c) is a magnetic flux diagram in each mechanical angle of the state which inserted the permanent magnet in the 2nd slot of Example 3. FIG. (A)-(c) is a magnetic flux diagram in each mechanical angle of the state which has not inserted the permanent magnet in the 2nd slot of Example 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electric motor 2 Stator 21a-21i Teeth 3 Rotor 31a-31i 1st slot 32a-32i 2nd slot 33 1st space | gap part 34 2nd space | gap part 341 Magnetic pole center side edge part 35 1st bridge part 36 2nd bridge part 37 Rotor magnetic pole 4 Rotating shaft 51a to 51i Permanent magnet 52a to 52i Permanent magnet

Claims (2)

A stator that generates a rotating magnetic field, and a rotor having a permanent magnet embedded therein and coaxially disposed on the inner diameter side of the stator, the rotor being orthogonal to the radial direction of the rotor And a first slot into which the permanent magnet is inserted, and a second slot arranged from both ends of the first slot along the radial direction of the rotor toward the outer peripheral surface of the rotor, In the magnet-embedded electric motor in which a gap is provided from the end of the second slot along the outer peripheral surface of the rotor,
The gap includes a first gap extending in the circumferential direction of the rotor from the end of the second slot along the outer peripheral surface of the rotor, and the rotor from the end of the first gap. And a second gap portion disposed in the circumferential direction of the rotor along the outer circumferential surface of the rotor,
The number of teeth of the stator is 3n, the number of magnetic poles of the rotor is 2n (n is a natural number), and the angle formed by the magnetic pole center side ends of the second gap with respect to the rotor center is about an electrical angle. 90 °
A second bridging portion is provided between the first gap portion and the second gap portion, and an angle formed by the second bridging portions provided on both ends of the magnetic poles with respect to the rotor center is α. And 126 ° <α <144 ° (electrical angle). A stator that generates a rotating magnetic field, and a rotor having a permanent magnet embedded therein and coaxially disposed on the inner diameter side of the stator, the rotor being orthogonal to the radial direction of the rotor A first slot into which the permanent magnet is inserted, and a first slot into which the permanent magnet is inserted from both ends of the first slot along the radial direction of the rotor toward the outer circumferential surface of the rotor. In an embedded magnet type motor having two slots, and a gap is provided along the outer peripheral surface of the rotor from the end of the second slot,
The gap includes a first gap extending in the circumferential direction of the rotor from the end of the second slot along the outer peripheral surface of the rotor, and the rotor from the end of the first gap. And a second gap disposed in the circumferential direction of the rotor along the outer circumferential surface of the rotor,
The number of teeth of the stator is 3n, the number of magnetic poles of the rotor is 2n (n is a natural number), and the angle formed by the magnetic pole center side ends of the second gap with respect to the rotor center is about an electrical angle. 90 °
A second bridging portion is provided between the first gap portion and the second gap portion, and an angle formed by the second bridging portions provided on both ends of the magnetic poles with respect to the rotor center is α. The electric motor is characterized in that 108 ° <α <144 ° (electrical angle).

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