Patent Publication Number: US-2022216757-A1

Title: Stator, electric motor, compressor, air conditioner, method for fabricating stator, and magnetization method

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a U.S. National Stage Application of International Application No. PCT/JP2019/027649, filed on Jul. 12, 2019, the contents of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a stator for an electric motor. 
     BACKGROUND 
     There is generally known a magnetization method for magnetizing a magnetic material of a rotor by using three-phase coils attached to a stator core. In this magnetization method, when a current for magnetization flows through the three-phase coils, an electromagnetic force might occur to cause deformation of the three-phase coils. In view of this, in the stator of Patent Reference 1, to prevent deformation of the three-phase coils, a lacing material is equally wound on the three-phase coils circumferentially. 
     PATENT REFERENCE 
     Patent Reference 1: Japanese Patent Application Publication No. H11-136896 
     In conventional techniques, however, a large amount of a lacing material is needed in magnetization in a state where a rotor is disposed inside a stator. Accordingly, costs for the stator increases, and significant deformation of three-phase coils of the stator cannot be prevented efficiently. 
     SUMMARY 
     It is therefore an object of the present invention to efficiently prevent significant deformation of three-phase coils of a stator in magnetization performed in a state where a rotor is disposed inside the stator. 
     A stator according to one aspect of the present invention is a stator capable of magnetizing a magnetic material of a rotor, and includes: a stator core; three-phase coils attached to the stator core by distributed winding, the three-phase coils including a first phase coil, a second phase coil, and a third phase coil; and a lacing material wound on the three-phase coil, wherein the first phase coil is a coil through which a largest current flows among the three-phase coils when a current flows through the three-phase coils from a source of electric power for magnetizing the magnetic material, the first phase coil has a first region, a second region, and a third region that are divided equally in a coil end of the three-phase coils, the first region is located between the second region and the third region, and the lacing material is wound on the first region more than at least one of the second region or the third region. 
     A stator according to another aspect of the present invention includes: a stator capable of magnetizing a magnetic material of a rotor, and includes: a stator core; three-phase coils attached to the stator core by distributed winding and including a first phase coil, a second phase coil, and a third phase coil; and a lacing material wound on the three-phase coil, wherein when a current flows through the three-phase coils from the source of electric power for magnetizing the magnetic material, a current flowing through the first phase coil is larger than at least one of a current flowing through the second phase coil or a current flowing through the third phase coil, in the coil end of the three-phase coils, the third phase coils includes a first region, a second region, and a third region that are divided equally, the first region is located between the second region and the third region, the lacing material is wound on the first region more than at least one either the second region or the third region. 
     An electric motor according to another aspect of the present invention includes: the stator; and the rotor disposed inside the stator. 
     A compressor according to another aspect of the present invention includes: a closed container; a compression device disposed in the closed container; and the electric motor configured to drive the compression device. 
     An air conditioner according to another aspect of the present invention includes: the compressor; and a heat exchanger. 
     A method for fabricating a stator according to another aspect of the present invention is a method for fabricating a stator, the stator including a stator core and three-phase coils attached to the stator core by distributed winding, the three-phase coils including a first phase coil, a second phase coil, and a third phase coil, the first phase coil having a first region, a second region, and a third region that are divided equally in a coil end of the three-phase coils, the first region being located between the second region and the third region, and the method includes: attaching the three-phase coils to the stator core by distributed winding; and winding a lacing material on the first region more than at least one of the second region or the third region in a coil end of the first phase coil. 
     A magnetization method according to another aspect of the present invention is a method for magnetizing a magnetic material of a rotor inside a stator, the stator including a stator core and three-phase coils, the three-phase coils being attached to the stator core by distributed winding and including a first phase coil, a second phase coil, and a third phase coil, the first phase coil having a first region, a second region, and a third region that are divided equally in a coil end of the three-phase coil, the first region being located between the second region and the third region, a lacing material being wound on the first region more than at least one of the second region or the third region in a coil end of the first phase coil, and the method includes: disposing the rotor including the magnetic material inside the stator; and supplying a current to the three-phase coils from a source of electric power for magnetizing the magnetic material so that a largest current flows through the first phase coil. 
     According to the present invention, in magnetization performed in a state where a rotor is disposed inside a stator, significant deformation of three-phase coils of the stator can be prevented efficiently. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plan view schematically illustrating a structure of an electric motor according to a first embodiment of the present invention. 
         FIG. 2  is a plan view schematically illustrating a structure of a rotor. 
         FIG. 3  is a plan view illustrating an example of a stator. 
         FIG. 4  is a diagram schematically illustrating an internal structure of the stator illustrated in  FIG. 3 . 
         FIG. 5  is a schematic view illustrating an example of connection in three-phase coils. 
         FIG. 6  is a diagram illustrating first regions, second regions, and third regions in first phase coils. 
         FIG. 7  is a diagram illustrating an equivalent circuit of a connection pattern of three-phase coils in magnetizing a magnetic material by using the stator. 
         FIG. 8  is a flowchart depicting an example of a fabrication step of a stator. 
         FIG. 9  is a diagram illustrating an insertion step of external phase coils. 
         FIG. 10  is a diagram illustrating an insertion step of intermediate phase coils. 
         FIG. 11  is a diagram illustrating an insertion step of internal phase coils. 
         FIG. 12  is a flowchart depicting an example of a method for magnetizing magnetic materials of a rotor. 
         FIG. 13  is a diagram illustrating another example of the stator. 
         FIG. 14  is a diagram schematically illustrating an internal structure of the stator illustrated in  FIG. 13 . 
         FIG. 15  is a diagram illustrating an equivalent circuit of a connection pattern of three-phase coils in magnetizing a magnetic material by using a stator in a first variation. 
         FIG. 16  is a diagram illustrating another example of the stator. 
         FIG. 17  is a diagram schematically illustrating an internal structure of the stator illustrated in  FIG. 16 . 
         FIG. 18  is a diagram illustrating an equivalent circuit of a connection pattern of three-phase coils in magnetizing a magnetic material by using a stator in a second variation. 
         FIG. 19  is a diagram illustrating an equivalent circuit of a connection pattern of three-phase coils in magnetizing a magnetic material by using a stator in a third variation. 
         FIG. 20  is a diagram illustrating an equivalent circuit of a connection pattern of three-phase coils in magnetizing a magnetic material by using a stator in a fourth variation. 
         FIG. 21  is a diagram illustrating an equivalent circuit of a connection pattern of three-phase coils in magnetizing a magnetic material by using a stator in a fifth variation. 
         FIG. 22  is a plan view illustrating another example of the stator. 
         FIG. 23  is a diagram illustrating an equivalent circuit of a connection pattern of three-phase coils in magnetizing a magnetic material by using a stator in a sixth variation. 
         FIG. 24  is a diagram illustrating an equivalent circuit of a connection pattern of three-phase coils in magnetizing a magnetic material by using a stator in a seventh variation. 
         FIG. 25  is a diagram illustrating an example of electromagnetic forces in a radial direction generated in a coil end of three-phase coils when the three-phase coils are energized in a fabrication step of a stator  3 , specifically, a magnetization step of a magnetic material. 
         FIG. 26  is a diagram illustrating an example of electromagnetic forces in an axial direction generated in a coil end of three-phase coils when the three-phase coils are energized in a fabrication step of a stator, specifically, a magnetization step of a magnetic material. 
         FIG. 27  is a graph showing a difference in magnitude of an electromagnetic force in a radial direction among connection patterns of three-phase coils when coils of each phase are energized in a magnetization step of a magnetic material. 
         FIG. 28  is a graph showing a difference in magnitude of an electromagnetic force in an axial direction among connection patterns of three-phase coils when coils of each phase are energized in a magnetization step of a magnetic material. 
         FIG. 29  is a graph showing a difference in magnitude of an electromagnetic force in a radial direction in each connection pattern of three-phase coils when two coils in the three-phase coils are energized in a magnetization step of a magnetic material. 
         FIG. 30  is a graph showing a difference in magnitude of an electromagnetic force in an axial direction in each connection pattern of three-phase coils when two coils in the three-phase coils are energized in a magnetization step of a magnetic material. 
         FIG. 31  is a cross-sectional view schematically illustrating a structure of a compressor according to a second embodiment of the present invention. 
         FIG. 32  is a diagram schematically illustrating a configuration of a refrigeration air conditioning apparatus according to a third embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     First Embodiment 
     In an xyz orthogonal coordinate system shown in each drawing, a z-axis direction (z axis) represents a direction parallel to an axis Ax of an electric motor  1 , an x-axis direction (x axis) represents a direction orthogonal to the z-axis direction (z axis), and a y-axis direction (y axis) represents a direction orthogonal to both the z-axis direction and the x-axis direction. The axis Ax is a center of a stator  3 , and is a rotation center of a rotor  2 . A direction parallel to the axis Ax is also referred to as an “axial direction of the rotor  2 ” or simply as an “axial direction.” The radial direction refers to a radial direction of the rotor  2  or a stator  3 , and is a direction orthogonal to the axis Ax. An xy plane is a plane orthogonal to the axial direction. An arrow D 1  represents a circumferential direction about the axis Ax. The circumferential direction of the rotor  2  or the stator  3  will be also referred to simply as a “circumferential direction.” 
     Structure of Electric Motor  1   
       FIG. 1  is a plan view schematically illustrating a structure of the electric motor  1  according to a first embodiment of the present invention. 
     The electric motor  1  includes the rotor  2  having a plurality of magnetic poles, the stator  3 , and a shaft  4  fixed to the rotor  2 . The electric motor  1  is, for example, a permanent magnet synchronous motor. 
     An air gap is present between the rotor  2  and the stator  3 . The rotor  2  rotates about an axis Ax. 
       FIG. 2  is a plan view schematically illustrating the structure of the rotor  2 . 
     The rotor  2  is rotatably disposed inside the stator  3 . The rotor  2  includes a rotor core  21  and at least one magnetic material  22 . 
     The rotor core  21  includes a plurality of magnet insertion holes  211  and a shaft hole  212 . The rotor core  21  may further include at least one flux barrier portion that is a space communicating with each of the magnet insertion holes  211 . 
     In this embodiment, the rotor  2  includes magnetic materials  22 . Each of the magnetic materials  22  is disposed in a corresponding one of the magnet insertion holes  211 . The shaft  4  is fixed to the shaft hole  212 . 
     The magnetic materials  22  included in the electric motor  1  as a finished product are magnetized magnetic materials  22 , that is, permanent magnets. In this embodiment, one magnetic material  22  forms one magnetic pole of the rotor  2 , that is, a north pole or a south pole. It should be noted that two or more magnetic materials  22  may form one magnetic pole of the rotor  2 . 
     In this embodiment, in the xy plane, one magnetic material  22  forming one magnetic pole of the rotor  2  is arranged in a straight line. Alternatively, in the xy plane, a pair of magnetic materials  22  forming one magnetic pole of the rotor  2  may be arranged to have a V shape. 
     A center of each magnetic pole of the rotor  2  is located at a center of each magnetic pole of the rotor  2  (i.e., a north pole or a south pole of the rotor  2 ). Each magnetic pole (hereinafter simply referred to as “each magnetic pole” or a “magnetic pole”) of the rotor  2  refers to a region serving as a north pole or a south pole of the rotor  2 . 
     Structure of Stator  3   
     The stator  3  is capable of magnetizing the magnetic materials  22  of the rotor  2  having 2×n (where n is a natural number) magnetic poles in a magnetization step described later. 
       FIG. 3  is a plan view illustrating an example of the stator  3 . A large current flows through the hatched coils from a source of electric power in the magnetization step described later. For example, in the example illustrated in  FIG. 3 , a current flowing through intermediate phase coils  322  is larger than each of a current flowing through internal phase coils  321  and a current flowing through external phase coils  323 . 
       FIG. 4  is a diagram schematically illustrating an internal structure of the stator  3  illustrated in  FIG. 3 . 
     The stator  3  includes a stator core  31 , three-phase coils  32 , at least one lacing material  34  wound on the three-phase coils  32 , and varnish  36 . 
     The stator core  31  includes a plurality of slots  311  in which the three-phase coils  32  are disposed. In the example illustrated in  FIG. 3 , the stator core  31  includes  36  slots  311 . 
     The three-phase coils  32  are attached to the stator core  31  by distributed winding. As illustrated in  FIG. 4 , the three-phase coils  32  include coil sides  32   b  disposed in the slots  311  and coil ends  32   a  not disposed in the slots  311 . Each coil end  32   a  is an end portion of the three-phase coil  32  in the axial direction. 
     Each three-phase coil  32  includes at least one internal phase coil  321 , at least one intermediate phase coil  322 , and at least one external phase coil  323 . That is, the three-phase coils  32  have a first phase, a second phase, and a third phase. For example, the first phase is a V phase, the second phase is a W phase, and the third phase is a U phase. 
     The three-phase coils  32  include 2×n first phase coils, 2×n second phase coils, and 2×n third phase coils. In this embodiment, n=3. Thus, in the example illustrated in  FIG. 3 , the three-phase coils  32  include six internal phase coils  321 , six intermediate phase coils  322 , and six external phase coils  323 . The number of coils of each phase is not limited to six. In this embodiment, the stator  3  has the structure illustrated in  FIG. 3  at two coil ends  32   a.  The stator  3  only needs to have the structure illustrated in  FIG. 3  at one of the two coil ends  32   a.    
     When a current flows through the three-phase coils  32 , the three-phase coils  32  form 2×n magnetic poles. In this embodiment, n=3. Thus, in this embodiment, when a current flows through the three-phase coils  32 , the three-phase coils  32  form six magnetic poles. 
     At the coil ends  32   a  of the three-phase coils  32 , the second phase coils, the first phase coils, and the third phase coils of the three-phase coils  32  are repeatedly arranged in this order in the circumferential direction of the stator core  31 . In the example illustrated in  FIG. 3 , at the coil ends  32   a  of the three-phase coils  32 , the internal phase coils  321 , the intermediate phase coils  322 , and the external phase coils  323  of the three-phase coils  32  are repeatedly arranged in this order in the circumferential direction of the stator core  31 . 
     At the coil ends  32   a  of the three-phase coils  32 , the second phase coils, the first phase coils, and the third phase coils are arranged in this order from the inner side of the stator core  31  in the radial direction of the stator core  31 . In the example illustrated in  FIG. 3 , the internal phase coils  321 , the intermediate phase coils  322 , and the external phase coils  323  are arranged in this order from the inner side of the stator core  31  in the radial direction of the stator core  31 . Thus, at the coil ends  32   a,  in the radial direction of the stator core  31 , the intermediate phase coils  322  are located outside the internal phase coils  321 , and the external phase coils  323  are located outside the intermediate phase coils  322 . 
     At the coil ends  32   a,  coils of each phase in the three-phase coils  32  have a ring shape. Specifically, in the example illustrated in  FIG. 3 , at the coil ends  32   a,  the six internal phase coils  321  have a ring shape, the six intermediate phase coils  322  have a ring shape, and the six external phase coils  323  have a ring shape. 
     At the coil ends  32   a,  coils of each phase in the three-phase coils  32  are concentrically arranged. Specifically, in the example illustrated in  FIG. 3 , at the coil ends  32   a,  the six internal phase coils  321  are concentrically arranged, the six intermediate phase coils  322  are concentrically arranged, and the six external phase coils  323  are concentrically arranged. 
     At the coil ends  32   a,  coils of each phase are arranged at regular intervals in the circumferential direction. A coil in any one of the phases is disposed in one slot  311 . In this manner, magnetic flux of the magnetic materials  22  of the rotor  2  can be effectively used. 
       FIG. 5  is a schematic view illustrating an example of connection in the three-phase coils  32 . 
     The connection in the three-phase coils  32  is, for example, Y connection. In other words, the three-phase coils  32  are connected by, for example, Y connection. In this case, the three-phase coils  32  have neutral points, and the internal phase coils  321 , the intermediate phase coils  322 , and the external phase coils  323  are connected by Y connection. 
       FIG. 6  is a diagram illustrating first regions  35   a , second regions  35   b,  and third regions  35   c  in the first phase coils. 
     At the coil ends  32   a  of the three-phase coils  32 , each of the 2×n first phase coils includes the first region  35   a,  the second region  35   b,  and the third region  35   c  that are equally divided. For example, as illustrated in  FIG. 3 , in a case where the first phase coils are the intermediate phase coils  322 , at the coil ends  32   a,  each of the six intermediate phase coils  322  includes the first region  35   a,  the second region  35   b , and the third region  35   c.    
     The first region  35   a  is located between the second region  35   b  and the third region  35   c.  At the coil ends  32   a  of the three-phase coils  32 , each first phase coil is equally divided into the first region  35   a,  the second region  35   b,  and the third region  35   c.  That is, in the xy plane, each first region  35   a , each second region  35   b,  and each third region  35   c  has the same area. 
     The lacing material  34  is, for example, a cord. The varnish  36  adheres to the lacing material  34 . Accordingly, the lacing material  34  is fixed to the three-phase coils  32 . 
     At each of the coil ends  32   a  of the first phase coils, the lacing material  34  is wound on the first region  35   a  more than the second region  35   b  and the third region  35   c.  In other words, at each of the coil ends  32   a  of the first phase coils, the density of the lacing material  34  in the first region  35   a  is higher than at least one of the density of the lacing material  34  in the second region  35   b  or the density of the lacing material  34  in the third region  35   c.    
     That is, the lacing material  34  may be wound on the first region  35   a  more than the second region  35   b,  the lacing material  34  may be wound on the first region  35   a  more than the third region  35   c,  and the lacing material  34  may be wound on the first region  35   a  more than each of the second region  35   b  and the third region  35   c.  In other words, at each of the coil ends  32   a  of the first phase coils, the density of the lacing material  34  in the first region  35   a  may be higher than the density of the lacing material  34  in the second region  35   b,  the density of the lacing material  34  in the first region  35   a  may be higher than the density of the lacing material  34  in the third region  35   c,  and the density of the lacing material  34  in the first region  35   a  may be higher than each of the density of lacing material  34  in the second region  35   b  and the density of the lacing material  34  in the third region  35   c.    
     In this embodiment, at each of the coil ends  32   a  of the first phase coils (the intermediate phase coils  322  in this embodiment), the lacing material  34  is wound on the first region  35   a  more than each of the second region  35   b  and the third region  35   c.  In other words, at each of the coil ends  32   a  of the first phase coils (the intermediate phase coils  322  in this embodiment), the density of the lacing material  34  in the first region  35   a  is higher than each of the density of the lacing material  34  in the second region  35   b  and the density of the lacing material  34  in the third region  35   c.    
     In a manner similar to the first phase coils, at the coil ends  32   a  of the three-phase coils  32 , each of the 2×n second phase coils has a first region, a second region, and a third region that are equally divided. That is, in the xy plane, each first region, each second region, and each third region of the second phase coils have the same area. In this case, in each of the second phase coils, the first region is located between the second region and the third region. 
     In a manner similar to the first phase coil, at the coil ends  32   a  of the three-phase coils  32 , each of the 2×n third phase coils have a first region, a second region, and a third region that are equally divided. That is, in the xy plane, each first region, each second region, and each third region of the third phase coils have the same area. In this case, in each of the third phase coils, the first region is located between the second region and the third region. 
     In the example illustrated in  FIG. 3 , at the coil ends  32   a  of the three-phase coils  32 , the density of the lacing material  34  in the first region  35   a  of each first phase coil is higher than the density of the lacing material  34  in the first region of each second phase coil and the density of the lacing material  34  in the first region of each third phase coil. Accordingly, in the magnetization step of the magnetic materials  22  described later, significant deformation of the first phase coils through which a largest current flows among the three-phase coils  32  can be prevented. 
       FIG. 7  is a diagram illustrating an equivalent circuit of a connection pattern of the three-phase coils  32  in magnetizing the magnetic materials  22  by using the stator  3 . In other words,  FIG. 7  is a diagram illustrating an example of a connection state between the three-phase coils  32  connected by Y connection and the source of electric power for magnetization. Arrows in  FIG. 7  represent directions of current. The source of electric power for magnetizing the magnetic materials  22  will be also referred to simply as a “source of electric power”. In this embodiment, the source of electric power is a direct-current source of electric power. 
     Y Connection, Three-phase Electrification, Connection Pattern P 1   
     In the example illustrated in  FIG. 7 , when a current flows through the three-phase coils  32  from the source of electric power for magnetization, the positive side of the source of electric power (i.e., the positive pole side of the source of electric power) is connected to the intermediate phase coil  322 , and the negative side of the source of electric power (i.e., the negative pole side of the source of electric power) is connected to the internal phase coil  321  and the external phase coil  323 . The connection state illustrated in  FIG. 7  will be referred to as a connection pattern P 1 . When a current flows through the three-phase coils  32  from the source of electric power for magnetization, an electrification method for causing a current to flow through coils of each phase will be referred to as “three-phase electrification.” 
     Although the circuit diagram illustrated in  FIG. 7  is an equivalent circuit diagram, in an actual magnetization step, when a current flows through the three-phase coils  32  from the source of electric power for magnetization, each of the 2×n first phase coils is connected to the positive side or the negative side of the source of electric power. In the connection pattern P 1 , the first phase coils are coils through which the largest current flows among the three-phase coils  32  when a current flows through the three-phase coils  32  from the source of electric power for magnetization. 
     In the connection pattern P 1 , when a current flows through the three-phase coils  32  from the source of electric power for magnetization in the magnetization step, a current flowing through each first phase coil is larger than a current flowing through each second phase coil, and is larger than a current flowing through each third phase coil. That is, in the magnetization step, when a current flows through the three-phase coils  32  from the source of electric power for magnetization, a current flowing through each first phase coil may be larger than a current flowing through each second phase coil, a current flowing through each first phase coil may be larger than a current flowing through each third phase coil, and a current flowing through each first phase coil may be larger than both of a current flowing through each second phase coil and a current flowing through each third phase coil. 
     In the connection pattern P 1 , a current flowing through the first phase coils from the source of electric power for magnetization is branched into a current flowing through the second phase coils and a current flowing through the third phase coils. That is, in the connection pattern P 1 , a large current flows through the intermediate phase coils  322  from the source of electric power. The current flowing through the intermediate phase coils  322  from the source of electric power is branched into as a current flowing through the internal phase coils  321  and a current flowing through the external phase coils  323 . Thus, the current flowing through the intermediate phase coils  322  is larger than each of a current flowing through the internal phase coils  321  and a current flowing through the external phase coils  323 . 
     Method for Fabricating Stator  3   
     An example of a method for fabricating the stator  3  will be described. 
       FIG. 8  is a flowchart depicting an example of a process for fabricating the stator  3 . 
       FIG. 9  is a diagram illustrating an insertion step of the external phase coils  323  in step S 11 . 
     In step S 11 , as illustrated in  FIG. 9 , the external phase coils  323  are attached to a previously prepared stator core  31  by distributed winding. Specifically, the external phase coils  323  are inserted in the slots  311  of the stator core  31  by an insertion tool. 
       FIG. 10  is a diagram illustrating an insertion step of the intermediate phase coils  322  in step S 12 . 
     In step S 12 , as illustrated in  FIG. 10 , the intermediate phase coils  322  are attached to the stator core  31  by distributed winding. Specifically, the intermediate phase coils  322  are inserted in the slots  311  of the stator core  31  by an insertion tool. 
       FIG. 11  is a diagram illustrating an insertion step of the internal phase coils  321  in step S 13 . 
     In step S 13 , as illustrated in  FIG. 11 , the internal phase coils  321  are attached to the stator core  31  by distributed winding. Specifically, the internal phase coils  321  are inserted in the slots  311  of the stator core  31  by an insertion tool. 
     In step S 11  through step S 13 , at each of the coil ends  32   a  of the three-phase coils  32 , the three-phase coils  32  are attached to the stator core  31  by distributed winding so that the intermediate phase coils  322 , the internal phase coils  321 , the external phase coils  323  are repeatedly arranged in this order in the circumferential direction of the stator core  31 . 
     In other words, in step S 11  through step S 13 , at each of the coil ends  32   a  of the three-phase coils  32 , the three-phase coils  32  are attached to the stator core  31  by distributed winding so that the internal phase coils  321 , the intermediate phase coils  322 , and the external phase coils  323  are arranged in this order from the inner side of the stator core  31  in the radial direction of the stator core  31 . 
     Accordingly, in step S 11  through step S 13 , at each of the coil ends  32   a  of the three-phase coils  32 , the three-phase coils  32  are attached to the stator core  31  so that the intermediate phase coils  322  are located outside the internal phase coils  321  and the external phase coils  323  are located outside the intermediate phase coil  322  in the radial direction of the stator core  31 . 
     In step S 14 , the internal phase coils  321 , the intermediate phase coils  322 , and the external phase coils  323  are connected. For example, the internal phase coils  321 , the intermediate phase coils  322 , and the external phase coils  323  are connected by Y connection or delta connection. In this embodiment, the internal phase coils  321 , the intermediate phase coils  322 , and the external phase coils  323  are connected by Y connection. Thereafter, the shape of the connected three-phase coils  32  is appropriately adjusted. 
     In step S 15 , a lacing material  34  is attached to the three-phase coils  32 . In this embodiment, as illustrated in  FIGS. 3 and 4 , the lacing material  34  is wound on the three-phase coils  32 . 
     For example, the lacing material  34  is wound on the internal phase coils  321  and the intermediate phase coils  322 . Accordingly, the internal phase coils  321  and the intermediate phase coils  322  are fixed by the lacing material  34 . 
     Similarly, the lacing material  34  is wound on the intermediate phase coils  322  and the external phase coils  323 . Accordingly, the intermediate phase coils  322  and the external phase coils  323  are fixed by the lacing material  34 . 
     In addition, the lacing material  34  may be wound on the internal phase coils  321 , the intermediate phase coils  322 , and the external phase coils  323 . Accordingly, the internal phase coils  321 , the intermediate phase coils  322 , and the external phase coils  323  are fixed by the lacing material  34 . 
     In step S 15 , at each of the coil ends  32   a  of each first phase coil, the lacing material  34  is wound on the first region  35   a  more than at least one of the second region  35   b  or the third region  35   c.  In other words, at each of the coil ends  32   a  of each first phase coil, the lacing material  34  is wound on the three-phase coils  32  so that the density of the lacing material  34  in the first region  35   a  is higher than at least one of the density of the lacing material  34  in the second region  35   b  or the density of the lacing material  34  in the third region  35   c.    
     In this embodiment, at each of the coil ends  32   a  of each first phase coil (each intermediate phase coil  322  in this embodiment), the lacing material  34  is wound on the first region  35   a  more than each of the second region  35   b  and the third region  35   c.  In other words, at each of the coil ends  32   a  of each first phase coil (each intermediate phase coil  322  in this embodiment), the lacing material  34  is wound on the three-phase coils  32  so that the density of the lacing material  34  in the first region  35   a  is higher than each of the density of the lacing material  34  in the second region  35   b  and the density of the lacing material  34  in the third region  35   c.    
     In step S 16 , the varnish  36  is made to adhere to the lacing material  34 . For example, the lacing material  34  is immersed in the varnish  36 . 
     At each of the coil ends  32   a  of each first phase coil (each intermediate phase coil  322  in this embodiment), since the lacing material  34  is wound on the first region  35   a  more than each of the second region  35   b  and the third region  35   c , the amount of varnish  36  adhering to the lacing material  34  in the first region  35   a  is larger than the amount of varnish adhering to the lacing material  34  in the second region  35   b  and the amount of varnish adhering to the lacing material  34  in the third region  35   c.  Accordingly, holding power of the lacing material  34  in the first region  35   a  is enhanced. Consequently, the first phase coils (the intermediate phase coils  322  in this embodiment) can be firmly fixed, and the amount of the varnish  36  in the stator  3  can be reduced as compared to a conventional technique. 
     In step S 17 , the varnish  36  adhering to the lacing material  34  is hardened. For example, the varnish  36  adhering to the lacing material  34  is heated by a heater and consequently the varnish  36  is hardened. Accordingly, the three-phase coils  32  are fixed by the lacing material  34 , and thus the stator  3  illustrated in  FIG. 3  is obtained. 
     Method for Magnetizing Magnetic Material  22  of Rotor  2  Using Stator  3   
     A method for magnetizing the magnetic materials  22  of the rotor  2  using the stator  3  will be described. 
       FIG. 12  is a flowchart depicting an example of a method for magnetizing the magnetic materials  22  of the rotor  2 . 
     In step S 21 , the stator  3  is fixed. For example, the stator  3  is fixed in a compressor or an electric motor by a fixing method such as press fitting or shrink fitting. 
     In step S 22 , the rotor is disposed inside the stator  3 . At least one of magnetic material  22  is attached to this rotor. 
     In step S 23 , three-phase coils  32  are connected to a source of electric power for magnetization. For example, first phase coils are connected to a positive side or a negative side of the source of electric power. The connection between the three-phase coils  32  and the source of electric power is, for example, the connection pattern P 1  described above. The connection between the three-phase coils  32  and the source of electric power may be any one of connection patterns P 2  through P 8  according to variations described later. 
     In step S 24 , a position of the rotor  2  (specifically, a phase of the rotor  2 ) having at least one magnetic material  22  is fixed by a jig. 
     Step S 25  is a step of magnetizing the magnetic material  22  (which will be referred to simply as a “magnetization step”). In step S 25 , the magnetic material  22  is magnetized. Specifically, a current is supplied from the source of electric power to the three-phase coils  32  so that a largest current flows through the first phase coils. 
     In the connection pattern P 1 , a large current flows through the intermediate phase coils  322  from the source of electric power. The current flowing through the intermediate phase coils  322  from the source of electric power is branched into as a current flowing through the internal phase coils  321  and a current flowing through the external phase coils  323 . Thus, the current flowing through the intermediate phase coils  322  is larger than each of a current flowing through the internal phase coils  321  and a current flowing through the external phase coils  323 . 
     A current flowing through the three-phase coils  32  from the source of electric power generates a magnetic field, and the magnetic material  22  of the rotor  2  is magnetized. Accordingly, the magnetic material  22  changes to a permanent magnet. 
     In step S 26 , the jig used in step S 24  is detached from the rotor. 
     Other examples of the stator  3 , that is, first through seventh variations, will be described with respect to aspects different from those described in the first embodiment. 
     First Variation &lt;Y Connection, Three-Phase Electrification, Connection Pattern P 2 &gt; 
       FIG. 13  is another example of the stator  3 . 
       FIG. 14  is a diagram schematically illustrating an internal structure of the stator  3  illustrated in  FIG. 13 . 
     In the stator  3  illustrated in  FIGS. 13 and 14  (hereinafter also referred to as a first variation), the first phase coils are the internal phase coils  321 , the second phase coils are the intermediate phase coils  322 , and the third phase coils are the external phase coils  323 . 
     That is, in the first variation, at the coil ends  32   a  of the three-phase coils  32 , the first phase coils, the second phase coils, and the third phase coils of the three-phase coils  32  are repeatedly arranged in this order in the circumferential direction of the stator core  31 , and the first phase coils, the second phase coils, and the third phase coils are arranged in this order from the inner side of the stator core  31  in the radial direction of the stator core  31 . 
       FIG. 15  is a diagram illustrating an equivalent circuit of a connection pattern of the three-phase coils  32  in magnetizing the magnetic material  22  by using the stator  3  in the first variation. In other words,  FIG. 15  is a diagram illustrating an example of a connection state between the three-phase coils  32  connected by Y connection and the source of electric power for magnetization in the first variation. Arrows in  FIG. 15  represent directions of current. 
     In the example illustrated in  FIG. 15 , when a current flows through the three-phase coils  32  from the source of electric power for magnetization, the positive side of the source of electric power (i.e., the positive pole side of the source of electric power) is connected to the internal phase coils  321 , and the negative side of the source of electric power (i.e., the negative pole side of the source of electric power) is connected to the intermediate phase coils  322  and the external phase coils  323 . The connection state illustrated in  FIG. 15  will be referred to as a connection pattern P 2 . 
     Although the circuit diagram illustrated in  FIG. 15  is an equivalent circuit diagram, in an actual magnetization step, when a current flows through the three-phase coils  32  from the source of electric power for magnetization, each of the 2×n first phase coils is connected to the positive side or the negative side of the source of electric power. 
     In the connection pattern P 2 , a large current flows through the internal phase coils  321  from the source of electric power. The current flowing through the internal phase coils  321  from the source of electric power is branched into as a current flowing through the intermediate phase coils  322  and a current flowing through the external phase coils  323 . Thus, a current flowing through the internal phase coils  321  is larger than each of a current flowing through the intermediate phase coils  322  and a current flowing through the external phase coils  323 . 
     In the first variation, the first phase coils are coils through which the largest current flows among the three-phase coils  32  when a current flows through the three-phase coils  32  from the source of electric power for magnetization. 
     In the first variation, at the coil ends  32   a  of the three-phase coils  32 , the density of the lacing material  34  in the first region  35   a  of each first phase coil is higher than the density of the lacing material  34  in the first region of each second phase coil and the density of the lacing material  34  in the first region of each third phase coil. Accordingly, in the magnetization step of the magnetic material  22 , significant deformation of the first phase coils through which a largest current flows among the three-phase coils  32  can be prevented. 
     Second Variation &lt;Y Connection, Two-Phase Electrification, Connection Pattern P 3 &gt; 
       FIG. 16  is another example of the stator  3 . 
       FIG. 17  is a diagram schematically illustrating an internal structure of the stator  3  illustrated in  FIG. 16 . 
     In the stator  3  illustrated in  FIGS. 16 and 17  (hereinafter also referred to as a second variation), the first phase coils are the internal phase coils  321 , the second phase coils are the external phase coils  323 , and the third phase coils are the intermediate phase coils  322 . 
     In this case, at the coil ends  32   a  of the three-phase coils  32 , the first phase coils, the third phase coils, and the second phase coils of the three-phase coils  32  are repeatedly arranged in this order in the circumferential direction of the stator core  31 , and the first phase coil, the third phase coil, and the second phase coil are arranged in this order from the inner side of the stator core  31  in the radial direction of the stator core  31 . 
     In the second variation, the first phase coils may be the external phase coils  323 . In this case, the internal phase coils  321  are, for example, the second phase coils. 
     In the second variation, each internal phase coil  321  has a first region  35   a,  a second region  35   b,  and a third region  35   c , and each external phase coil  323  also has a first region  35   a,  a second region  35   b,  and a third region  35   c.    
     In each of the coil ends  32   a,  the lacing material  34  is wound on the first region  35   a  more than at least one of the second region  35   b  or the third region  35   c.  In other words, at each of the coil ends  32   a,  the density of the lacing material  34  in the first region  35   a  is higher than at least one of the density of the lacing material  34  in the second region  35   b  or the density of the lacing material  34  in the third region  35   c.    
     In the example illustrated in  FIG. 16 , at each of the coil ends  32   a,  the lacing material  34  is wound on the first region  35   a  more than the second region  35   b.  In other words, at each of the coil ends  32   a,  the density of the lacing material  34  in the first region  35   a  is higher than the density of the lacing material  34  in the second region  35   b.    
       FIG. 18  is a diagram illustrating an equivalent circuit of a connection pattern of the three-phase coils  32  in magnetizing the magnetic material  22  by using the stator  3  in the second variation. In other words,  FIG. 18  is a diagram illustrating an example of a connection state between the three-phase coils  32  connected by Y connection and the source of electric power for magnetization in the second variation. Arrows in  FIG. 18  represent directions of current. 
     In the example illustrated in  FIG. 18 , when a current flows through the three-phase coils  32  from the source of electric power for magnetization, the positive side of the source of electric power is connected to the internal phase coils  321 , and the negative side of the source of electric power is connected to the external phase coils  323 . One end of each intermediate phase coil  322  is connected to a neutral point, and the other end is a free end. The connection state illustrated in  FIG. 18  will be referred to as a connection pattern P 3 . When a current flows through the three-phase coils  32  from the source of electric power for magnetization, an electrification method for causing a current to flow in two of the three phases will be referred to as “two-phase electrification.” 
     In the connection pattern P 3 , a current flowing through the first phase coils from the source of electric power for magnetization flows through the second phase coils and does not flow through the third phase coils. In this embodiment, a large current flows through the internal phase coils  321  and the external phase coils  323  from the source of electric power. The current flowing through the internal phase coils  321  from the source of electric power flows through the external phase coils  323  and does not flow in the intermediate phase coils  322 . 
     In the second variation, the first phase coils and the second phase coils are coils through which the largest current flows among the three-phase coils  32  when a current flows through the three-phase coils  32  from the source of electric power for magnetization. 
     In the second variation, the density of the lacing material  34  in the first region  35   a  of each first phase coil is higher than the density of the lacing material  34  in the first region of each third phase coil, and the density of the lacing material  34  in the first region  35   a  of each second phase coil is higher than the density of the lacing material  34  in the first region of each third phase coil. Accordingly, in the magnetization step of the magnetic material  22 , a largest current among the three-phase coils  32  flows through the first phase coils and the second phase coils, and thus, significant deformation of the first phase coils and the second phase coils can be prevented in the magnetization step of the magnetic material  22 . 
     Third Variation &lt;Delta Connection, Three-Phase Electrification, Connection Pattern P 4 &gt; 
     In a third variation, the structure of the stator  3  is the same as the structure of the stator  3  illustrated in  FIGS. 3 and 4 , and a connection pattern of the three-phase coils  32  in magnetizing the magnetic material  22  using the stator  3  is different from the connection pattern P 1  illustrated in  FIG. 7 . 
     In the third variation, the connection in the three-phase coils  32  is delta connection. In other words, the three-phase coils  32  are connected by delta connection. In this case, the internal phase coils  321 , the intermediate phase coils  322 , and the external phase coils  323  are connected by delta connection. 
       FIG. 19  is a diagram illustrating an equivalent circuit of a connection pattern of the three-phase coils  32  in magnetizing the magnetic material  22  by using the stator  3  in the third variation. In other words,  FIG. 19  is a diagram illustrating an example of a connection state between the three-phase coils  32  connected by delta connection and the source of electric power for magnetization in the third variation. Arrows in  FIG. 19  represent directions of current. 
     In the example illustrated in  FIG. 19 , when a current flows through the three-phase coils  32  from the source of electric power for magnetization, the positive side of the source of electric power is connected to the intermediate phase coils  322  and the external phase coils  323 , and the negative side of the source of electric power is connected to the internal phase coils  321  and the intermediate phase coils  322 . The connection state illustrated in  FIG. 19  will be referred to as a connection pattern P 4 . 
     In the connection pattern P 4 , a current flows through the internal phase coils  321 , the intermediate phase coils  322 , and the external phase coils  323  from the source of electric power. Since the external phase coils  323  and the internal phase coils  321  are connected in series, an electrical resistance from the external phase coils  323  to the internal phase coils  321  is larger than an electrical resistance of the intermediate phase coils  322 . Thus, a current flowing through the external phase coils  323  and the internal phase coils  321  is smaller than a current flowing through the intermediate phase coils  322 , and a current flowing through the intermediate phase coils  322  is larger than each of a current flowing through the external phase coils  323  and a current flowing through the internal phase coils  321 . 
     In the third variation, the first phase coils are coils through which the largest current flows among the three-phase coils  32  when a current flows through the three-phase coils  32  from the source of electric power for magnetization. 
     In the third variation, at the coil ends  32   a  of the three-phase coils  32 , the density of the lacing material  34  in the first region  35   a  of each first phase coil is higher than the density of the lacing material  34  in the first region of each second phase coil and the density of the lacing material  34  in the first region of each third phase coil. Accordingly, in the magnetization step of the magnetic material  22 , significant deformation of the first phase coils through which a largest current flows among the three-phase coils  32  can be prevented. 
     Fourth Variation &lt;Delta Connection, Three-Phase Electrification, Connection Pattern P 5 &gt; 
     In a fourth variation, the structure of the stator  3  is the same as the structure of the first variation illustrated in  FIGS. 13 and 14 , and a connection pattern of the three-phase coils  32  in magnetizing the magnetic material  22  using the stator  3  is different from the connection pattern P 2  in the first variation. 
     In the fourth variation, the connection in the three-phase coils  32  is delta connection. In other words, the three-phase coils  32  are connected by delta connection. In this case, the internal phase coils  321 , the intermediate phase coils  322 , and the external phase coils  323  are connected by delta connection. 
       FIG. 20  is a diagram illustrating an equivalent circuit of a connection pattern of the three-phase coils  32  in magnetizing the magnetic material  22  by using the stator  3  in the fourth variation. In other words,  FIG. 20  is a diagram illustrating an example of a connection state between the three-phase coils  32  connected by delta connection and the source of electric power for magnetization in the fourth variation. Arrows in  FIG. 20  represent directions of current. 
     In the example illustrated in  FIG. 20 , when a current flows through the three-phase coils  32  from the source of electric power for magnetization, the positive side of the source of electric power is connected to the intermediate phase coils  322  and the internal phase coils  321 , and the negative side of the source of electric power is connected to the internal phase coils  321  and the external phase coils  323 . The connection state illustrated in  FIG. 20  will be referred to as a connection pattern P 5 . 
     In the connection pattern P 5 , a current flows through the internal phase coils  321 , the intermediate phase coils  322 , and the external phase coils  323  from the source of electric power. Since the intermediate phase coils  322  and the external phase coils  323  are connected in series, an electrical resistance from the intermediate phase coils  322  to the external phase coils  323  is larger than an electrical resistance of the internal phase coils  321 . Thus, a current flowing through the intermediate phase coils  322  and the external phase coils  323  is smaller than a current flowing through the internal phase coils  321 , and a current flowing through the internal phase coils  321  is larger than each of a current flowing through the intermediate phase coils  322  and a current flowing through the external phase coils  323 . 
     In the fourth variation, the first phase coils are coils through which the largest current flows among the three-phase coils  32  when a current flows through the three-phase coils  32  from the source of electric power for magnetization. 
     In the fourth variation, at the coil ends  32   a  of the three-phase coils  32 , the density of the lacing material  34  in the first region  35   a  of each first phase coil is higher than the density of the lacing material  34  in the first region of each second phase coil and the density of the lacing material  34  in the first region of each third phase coil. Accordingly, in the magnetization step of the magnetic materials  22 , significant deformation of the first phase coils through which a largest current flows among the three-phase coils  32  can be prevented. 
     Fifth Variation &lt;Delta Connection, Two-Phase Electrification, Connection Pattern P 6 &gt; 
     In a fifth variation, the structure of the stator  3  is the same as the structure of the second variation illustrated in  FIGS. 16 and 17 , and a connection pattern of the three-phase coils  32  in magnetizing the magnetic material  22  using the stator  3  is different from the connection pattern P 3  in the second variation. 
     In the fifth variation, the connection in the three-phase coils  32  is delta connection. In other words, the three-phase coils  32  are connected by delta connection. In this case, the internal phase coils  321 , the intermediate phase coils  322 , and the external phase coils  323  are connected by delta connection. 
       FIG. 21  is a diagram illustrating an equivalent circuit of a connection pattern of the three-phase coils  32  in magnetizing the magnetic material  22  by using the stator  3  in the fifth variation. In other words,  FIG. 21  is a diagram illustrating an example of a connection state between the three-phase coils  32  connected by delta connection and the source of electric power for magnetization in the fifth variation. Arrows in  FIG. 21  represent directions of current. 
     In the example illustrated in  FIG. 21 , when a current flows through the three-phase coils  32  from the source of electric power for magnetization, the positive side of the source of electric power is connected to the external phase coils  323 , the intermediate phase coils  322 , and the internal phase coils  321 , and the negative side of the source of electric power is connected to the internal phase coils  321  and the external phase coils  323 . The connection state illustrated in  FIG. 21  will be referred to as a connection pattern P 6 . 
     In the connection pattern P 6 , a current flows through the internal phase coils  321  and the external phase coils  323  from the source of electric power, and no current flows through the intermediate phase coils  322 . Accordingly, a large current flows through the internal phase coils  321  and the external phase coils  323 . 
     In the fifth variation, the first phase coils and the second phase coils are coils through which the largest current flows among the three-phase coils  32  when a current flows through the three-phase coils  32  from the source of electric power for magnetization. 
     In the fifth variation, the density of the lacing material  34  in the first region  35   a  of each first phase coil is higher than the density of the lacing material  34  in the first region of each third phase coil, and the density of the lacing material  34  in the first region  35   a  of each second phase coil is higher than the density of the lacing material  34  in the first region of each third phase coil. Accordingly, in the magnetization step of the magnetic material  22 , a largest current among the three-phase coils  32  flows through the first phase coils and the second phase coils, and thus, significant deformation of the first phase coils and the second phase coils can be prevented in the magnetization step of the magnetic material  22 . 
     Sixth Variation &lt;Y Connection, Three-Phase Electrification, Connection Pattern P 7 &gt; 
       FIG. 22  is a plan view illustrating another example of the stator  3 . 
     In a sixth variation, the first phase coils are the external phase coils  323 , the second phase coils are the intermediate phase coils  322 , and the third phase coils are the internal phase coils  321 . 
     That is, in the sixth variation, at the coil ends  32   a  of the three-phase coils  32 , the third phase coils, the second phase coils, and the first phase coils of the three-phase coils  32  are repeatedly arranged in this order in the circumferential direction of the stator core  31 , and the third phase coils, the second phase coils, and the first phase coils are arranged in this order from the inner side of the stator core  31  in the radial direction of the stator core  31 . 
       FIG. 23  is a diagram illustrating an equivalent circuit of a connection pattern of the three-phase coils  32  in magnetizing the magnetic material  22  by using the stator  3  in the sixth variation. In other words,  FIG. 23  is a diagram illustrating an example of a connection state between the three-phase coils  32  connected by Y connection and the source of electric power for magnetization in the sixth variation. Arrows in  FIG. 23  represent directions of current. 
     In the example illustrated in  FIG. 23 , when a current flows through the three-phase coils  32  from the source of electric power for magnetization, the positive side of the source of electric power is connected to the internal phase coils  321  and the intermediate phase coils  322 , and the negative side of the source of electric power is connected to the external phase coils  323 . The connection state illustrated in  FIG. 23  will be referred to as a connection pattern P 7 . 
     In the connection pattern P 7 , a current from the source of electric power is branched into a current flowing through the internal phase coils  321  and a current flowing through the intermediate phase coils  322 , and these currents flow in the external phase coils  323 . Thus, a current flowing through the external phase coils  323  is larger than each of a current flowing through the internal phase coils  321  and a current flowing through the intermediate phase coils  322 . 
     In the sixth variation, the first phase coils are coils through which the largest current flows among the three-phase coils  32  when a current flows through the three-phase coils  32  from the source of electric power for magnetization. 
     In the sixth variation, at the coil ends  32   a  of the three-phase coils  32 , the density of the lacing material  34  in the first region  35   a  of each first phase coil is higher than the density of the lacing material  34  in the first region of each second phase coil and the density of the lacing material  34  in the first region of each third phase coil. Accordingly, in the magnetization step of the magnetic material  22 , significant deformation of the first phase coils through which a largest current flows among the three-phase coils  32  can be prevented. 
     Seventh Variation &lt;Delta Connection, Three-Phase Electrification, Connection Pattern P 8 &gt; 
     In a seventh variation, the structure of the stator  3  is the same as the structure of the stator  3  illustrated in  FIG. 22 , and a connection pattern of the three-phase coils  32  in magnetizing the magnetic material  22  using the stator  3  is different from the connection pattern P 7  illustrated in  FIG. 23 . 
     In the seventh variation, the connection in the three-phase coils  32  is delta connection. In other words, the three-phase coils  32  are connected by delta connection. In this case, the internal phase coils  321 , the intermediate phase coils  322 , and the external phase coils  323  are connected by delta connection. 
       FIG. 24  is a diagram illustrating an equivalent circuit of a connection pattern of the three-phase coils  32  in magnetizing the magnetic material  22  by using the stator  3  in the seventh variation. In other words,  FIG. 24  is a diagram illustrating an example of a connection state between the three-phase coils  32  connected by delta connection and the source of electric power for magnetization in the seventh variation. Arrows in  FIG. 24  represent directions of current. 
     In the example illustrated in  FIG. 24 , when a current flows through the three-phase coils  32  from the source of electric power for magnetization, the positive side of the source of electric power is connected to the intermediate phase coils  322  and the external phase coils  323 , and the negative side of the source of electric power is connected to the internal phase coils  321  and the external phase coils  323 . The connection state illustrated in  FIG. 24  will be referred to as a connection pattern P 8 . 
     In the connection pattern P 8 , a current flowing through the external phase coils  323  is larger than each of a current flowing through the internal phase coils  321  and a current flowing through the intermediate phase coils  322 . 
     In the seventh variation, the first phase coils are coils through which the largest current flows among the three-phase coils  32  when a current flows through the three-phase coils  32  from the source of electric power for magnetization. 
     In the seventh variation, at the coil ends  32   a  of the three-phase coils  32 , the density of the lacing material  34  in the first region of each first phase coil is higher than the density of the lacing material  34  in the first region of each second phase coil and the density of the lacing material  34  in the first region of each third phase coil. Accordingly, in the magnetization step of the magnetic materials  22 , significant deformation of the first phase coils through which a largest current flows among the three-phase coils  32  can be prevented. 
     Advantages of Stator  3   
     Advantages of the stator  3  will be described.  FIG. 25  is a diagram illustrating an example of electromagnetic forces F 1  in a radial direction generated in the coil ends  32   a  of the three-phase coils  32  when the three-phase coils  32  are energized in a fabrication step of the stator  3 , specifically, a magnetization step of the magnetic materials  22 . In  FIG. 25 , arrows in the three-phase coils  32  represent directions of current. 
     In the example illustrated in  FIG. 25 , when a current flows through the three-phase coils  32  from the source of electric power for magnetization, electromagnetic forces F 1  that are repulsive to each other in the radial direction are generated between the intermediate phase coils  322  and the external phase coils  323 . The electromagnetic forces F 1  are also called Lorentz forces. 
       FIG. 26  is a diagram illustrating an example of electromagnetic forces F 2  in a radial direction generated in the coil ends  32   a  of the three-phase coils  32  when the three-phase coils  32  are energized in the fabrication step of the stator  3 , specifically, the magnetization step of the magnetic materials  22 . 
     In a case where a current flows through a curved path such as the coil ends  32   a,  a difference in the magnetic flux density caused by a current occurs between the inner side and the outer side of the curved portion, and forces are generated in the three-phase coils  32  so as to uniformize the magnetic flux density. Accordingly, forces that are to deform the coil ends  32   a  linearly are generated in the coil ends  32   a.  Since the both end portions of the coil ends  32   a  in the coils of each phase are fixed to the stator core  31 , forces are exerted in the axial direction in the coil ends  32   a.  Accordingly, when a current flows through the three-phase coils  32  from the source of electric power for magnetization, electromagnetic forces F 2  in the axial direction are generated in the three-phase coils  32 , as illustrated in  FIG. 26 . 
       FIG. 27  is a graph showing a difference in magnitude of an electromagnetic force F 1  in the radial direction among connection patterns of the three-phase coils  32  when coils of each phase are energized in the magnetization step of the magnetic material  22 . That is,  FIG. 27  is a graph showing a difference in magnitude of the electromagnetic force F 1  in the radial direction generated when magnetization is performed in three-phase electrification in the magnetization step of the magnetic material  22 . Data shown in  FIG. 27  is a result of analysis by an electromagnetic field analysis. 
     In  FIG. 27 , the connection patterns P 1  and P 2  correspond to connection patterns shown in  FIGS. 7 and 15 , respectively. A connection pattern Ex 1  is a comparative example. In the connection pattern Ex 1 , in the three-phase coils  32  connected by Y connection, the external phase coils  323  are connected to the positive side of the source of electric power for magnetization, and the internal phase coils  321  and the intermediate phase coils  322  are connected to the negative side of the source of electric power. In the connection pattern Ex 1 , a large current flows through the external phase coils  323 . 
     In the connection pattern Ex 1 , a large current flows through the external phase coils  323  from the source of electric power for magnetization, and electromagnetic forces F 1  generated in the external phase coils  323  are larger than those in the connection patterns P 1  and P 2 . In this case, the external phase coils  323  are easily deformed in the radial direction. Accordingly, when the electric motor  1  is applied to a compressor, for example, the external phase coils  323  approach a metal part (e.g., a closed container of the compressor), and it becomes difficult to obtain electrical insulation of the external phase coils  323 . 
     On the other hand, in the connection patterns P 1  and P 2 , electromagnetic forces F 1  generated in the external phase coils  323  are smaller than those in the connection pattern Ex 1 . Thus, in performing magnetization with the rotor  2  disposed inside the stator  3 , significant deformation of the three-phase coils  32 , especially the external phase coils  323 , can be prevented. As a result, deformation of the external phase coils  323  is suppressed, and thus electrical insulation of the external phase coils  323  can be obtained. 
       FIG. 28  is a graph showing a difference in magnitude of electromagnetic forces F 2  in the axial direction among connection patterns pf the three-phase coils  32  when coils of each phase are energized in the magnetization step of the magnetic materials  22 . That is,  FIG. 28  is a graph showing a difference in magnitude of the electromagnetic forces F 2  in the axial direction generated when magnetization is performed in three-phase electrification in the magnetization step of the magnetic material  22 . In  FIG. 28 , the connection patterns Ex 1 , P 1 , and P 2  correspond to the connection patterns Ex 1 , P 1 , and P 2 , respectively, in  FIG. 27 . 
     As shown in  FIG. 28 , with respect to electromagnetic forces F 2  in the axial direction, a large electromagnetic force F 2  in the axial direction is generated in one of the three-phase coils  32 , independently of the connection pattern. Specifically, in the connection pattern Ex 1 , a large current flows through the external phase coils  323  from the source of electric power, and large electromagnetic forces F 2  in the axial direction are generated in the external phase coils  323 . In the connection pattern P 1 , a large current flows through the intermediate phase coils  322  from the source of electric power, and large electromagnetic forces F 2  in the axial direction are generated in the intermediate phase coils  322 . In the connection pattern P 2 , a large current flows through the internal phase coils  321  from the source of electric power, and large electromagnetic forces F 2  in the axial direction are generated in the internal phase coils  321 . 
     As described above, in the magnetization step of the magnetic material  22 , the connection pattern of the three-phase coils  32  is preferably the connection pattern P 1  or P 2  in consideration of electromagnetic forces F 1  in the radial direction. In the connection pattern P 1  or P 2 , however, electromagnetic forces F 2  of the first phase coils connected to the positive side of the source of electric power for magnetization are large. Deformation tends to be large especially in a center portion, that is, the first region  35   a , of each first phase coil. 
     Thus, at each of the coil ends  32   a  of each first phase coil, the lacing material  34  is wound on the first region  35   a  more than the second region  35   b  and the third region  35   c.  In other words, at each of the coil ends  32   a  of each first phase coil, the density of the lacing material  34  in the first region  35   a  is higher than at least one of the density of the lacing material  34  in the second region  35   b  or the density of the lacing material  34  in the third region  35   c.  In the connection pattern P 1 , the first phase coils are the intermediate phase coils  322 , and in the connection pattern P 2 , the first phase coils are the internal phase coils  321 . 
     Accordingly, in the connection pattern P 1  or P 2 , in performing magnetization with the rotor  2  disposed inside the stator  3 , the lacing material  34  can prevent significant deformation of the first phase coils. 
     Accordingly, deformation of the three-phase coils  323  is suppressed, and thus, performance of the electric motor  1 , for example, electrical insulation of the three-phase coils  32 , can be obtained. 
     In addition, at each of the coil ends  32   a  of each first phase coil, the lacing material  34  only needs to be wound on the first region  35   a  more than at least one of the second region  35   b  or the third region  35   c,  and thus, the number of lacing materials  34  can be reduced, and costs for the stator  3  can be reduced. Accordingly, significant deformation of the three-phase coils  32  can be efficiently prevented. 
     The amount of the varnish  36  adhering to the lacing material  34  in the first region  35   a  only needs to be larger than at least one of the amount of varnish adhering to the lacing material  34  in the second region  35   b  or the amount of varnish adhering to the lacing material  34  in the third region  35   c.  Accordingly, holding power of the lacing material  34  in the first region  35   a  is enhanced. Consequently, the first phase coils can be firmly fixed, and the amount of varnish  36  in the stator  3  can be reduced, as compared to a conventional technique. 
       FIG. 29  is a graph showing a difference in magnitude of electromagnetic forces F 1  in the radial direction among connection pattern of the three-phase coils  32  when two coils of the three-phase coils  32  are energized in the magnetization step of the magnetic material  22 . That is,  FIG. 29  is a graph showing a difference in magnitude of the electromagnetic force F 1  in the radial direction generated when magnetization is performed in two-phase electrification in the magnetization step of the magnetic material  22 . Data shown in  FIG. 29  is a result of analysis by an electromagnetic field analysis. 
     In  FIG. 29 , the connection pattern P 3  corresponds to the connection pattern shown in  FIG. 18 . Connection patterns Ex 2  and Ex 3  are comparative examples. In the connection pattern Ex 2 , in the three-phase coils  32  connected by Y connection, the external phase coils  323  are connected to the positive side of the source of electric power for magnetization, the intermediate phase coils  322  are connected to the negative side of the source of electric power, and one end of each internal phase coil  321  is an open end. In the connection pattern Ex 3 , in the three-phase coils  32  connected by Y connection, the intermediate phase coils  322  are connected to the positive side of the source of electric power for magnetization, the internal phase coils  321  are connected to the negative side of the source of electric power, and one end of each internal phase coil  321  is an open end. 
     In the connection pattern Ex 2 , a large current flows through the external phase coils  323  from the source of electric power for magnetization, and electromagnetic forces F 1  generated in the external phase coils  323  are large. In this case, the external phase coils  323  are easily deformed in the radial direction. Accordingly, when the electric motor  1  is applied to a compressor, for example, the external phase coils  323  approach a metal part (e.g., a closed container of the compressor) and it becomes difficult to obtain electrical insulation of the external phase coils  323 . 
     On the other hand, in the connection patterns Ex 3  and P 3 , electromagnetic forces F 1  generated in the external phase coils  323  are smaller than those in the connection pattern Ex 2 . Thus, in performing magnetization with the rotor  2  disposed inside the stator  3 , significant deformation of the three-phase coils  32 , especially the external phase coils  323 , can be prevented. As a result, deformation of the external phase coils  323  is suppressed, and thus electrical insulation of the external phase coils  323  can be obtained. 
       FIG. 30  is a graph showing a difference in magnitude of electromagnetic forces F 2  in the axial direction among connection patterns of the three-phase coils  32  when two coils of the three-phase coils  32  are energized in the magnetization step of the magnetic material  22 . That is,  FIG. 30  is a graph showing a difference in magnitude of the electromagnetic forces F 2  in the axial direction generated when magnetization is performed in two-phase electrification in the magnetization step of the magnetic material  22 . In  FIG. 30 , the connection patterns Ex 2 , Ex 3 , and P 3  correspond to the connection patterns Ex 2 , Ex 3 , and P 3 , respectively, in  FIG. 29 . 
     As shown in  FIG. 30 , with respect to electromagnetic forces F 2  in the axial direction, a large electromagnetic force F 2  in the axial direction is generated in two coils of the three-phase coils  32 , independently of the connection pattern. 
     In the case of two-phase electrification, in the magnetization step of the magnetic material  22 , the connection pattern of the three-phase coils  32  is preferably the connection pattern Ex 3  or P 3  in consideration of electromagnetic forces F 1  in the radial direction. In the connection pattern Ex 3 , since electromagnetic forces F 1  in the internal phase coils  321  are large, in the case of two-phase electrification, connection of the three-phase coils  32  is more preferably the connection pattern P 3 . 
     In the connection pattern Ex 3  or P 3 , however, electromagnetic forces F 2  of the first phase coils connected to the positive side of the source of electric power for magnetization are large. Deformation tends to be large especially in a center portion, that is, the first region  35   a , of each first phase coil. 
     Thus, at each of the coil ends  32   a  of each first phase coil, the lacing material  34  is wound on the first region  35   a  more than the second region  35   b  and the third region  35   c.  In other words, at each of the coil ends  32   a  of each first phase coil, the density of the lacing material  34  in the first region  35   a  is higher than at least one of the density of the lacing material  34  in the second region  35   b  or the density of the lacing material  34  in the third region  35   c.  In the connection pattern Ex 3 , the first phase coils are the intermediate phase coils  322 , and in the connection pattern P 3 , the first phase coils are the internal phase coils  321 . 
     Accordingly, in the connection pattern Ex 3  or P 3 , in performing magnetization with the rotor  2  disposed inside the stator  3 , the lacing material  34  can prevent significant deformation of the first phase coils. 
     Accordingly, deformation of the three-phase coils  323  is suppressed, and thus, performance of the electric motor  1 , for example, electrical insulation of the three-phase coils  32 , can be obtained. 
     In addition, at each of the coil ends  32   a  of each first phase coil, the lacing material  34  only needs to be wound on the first region  35   a  more than at least one of the second region  35   b  or the third region  35   c,  and thus, the number of lacing materials  34  can be reduced, and costs for the stator  3  can be reduced. Accordingly, significant deformation of the three-phase coils  32  can be efficiently prevented. 
     The amount of the varnish  36  adhering to the lacing material  34  in the first region  35   a  only needs to be larger than at least one of the amount of varnish adhering to the lacing material  34  in the second region  35   b  or the amount of varnish adhering to the lacing material  34  in the third region  35   c.  Accordingly, holding power of the lacing material  34  in the first region  35   a  is enhanced. Consequently, the first phase coils can be firmly fixed, and the amount of varnish  36  in the stator  3  can be reduced, as compared to a conventional technique. 
     In a case where the three-phase coils  32  are connected by delta connection, properties shown in  FIGS. 27 through 30  are also obtained. Thus, in the case where the three-phase coils  32  are connected by delta connection, in performing magnetization with the rotor  2  disposed inside the stator  3 , the lacing material  34  can also prevent significant deformation of the first phase coils. Accordingly, deformation of the three-phase coils  323  is suppressed, and thus, performance of the electric motor  1 , for example, electrical insulation of the three-phase coils  32 , can be obtained. 
     In the case there the three-phase coils  32  are connected by delta connection, at each of the coil ends  32   a  of each first phase coil, the lacing material  34  also only needs to be wound on the first region  35   a  more than at least one of the second region  35   b  or the third region  35   c.  In this case, the number of lacing materials  34  can be reduced, and costs for the stator  3  can be reduced. Accordingly, significant deformation of the three-phase coils  32  can be efficiently prevented. 
     In the case where the three-phase coils  32  are connected by delta connection, the amount of the varnish  36  adhering to the lacing material  34  in the first region  35   a  also only needs to be larger than at least one of the amount of varnish adhering to the lacing material  34  in the second region  35   b  or the amount of varnish adhering to the lacing material  34  in the third region  35   c.  Accordingly, holding power of the lacing material  34  in the first region  35   a  is enhanced. Consequently, the first phase coils can be firmly fixed, and the amount of varnish  36  in the stator  3  can be reduced, as compared to a conventional technique. 
     Second Embodiment 
     A compressor  300  according to a second embodiment of the present invention will be described. 
       FIG. 31  is a cross-sectional view schematically illustrating a structure of the compressor  300 . 
     The compressor  300  includes an electric motor  1  as an electric element, a closed container  307  as a housing, and a compression mechanism  305  as a compression element (also referred to as a compression device). In this embodiment, the compressor  300  is a scroll compressor. The compressor  300  is not limited to the scroll compressor. The compressor  300  may be a compressor except for the scroll compressor, such as a rotary compressor. 
     The electric motor  1  in the compressor  300  is the electric motor  1  described in the first embodiment. The electric motor  1  drives the compression mechanism  305 . 
     The compressor  300  includes a subframe  308  supporting a lower end (i.e., an end opposite to the compression mechanism  305 ) of a shaft  4 . 
     The compression mechanism  305  is disposed inside the closed container  307 . The compressor mechanism  305  includes a fixed scroll  301  having a spiral portion, a swing scroll  302  having a spiral portion forming a compression chamber between the spiral portion of the swing scroll  302  and the spiral portion of the fixed scroll  301 , a compliance frame  303  holding an upper end of the shaft  4 , and a guide frame  304  fixed to the closed container  307  and holding the compliance frame  303 . 
     A suction pipe  310  penetrating the closed container  307  is press fitted in the fixed scroll  301 . The closed container  307  is provided with a discharge pipe  306  that discharges a high-pressure refrigerant gas discharged from the fixed scroll  301 , to the outside. The discharge pipe  306  communicates with an opening disposed between the compressor mechanism  305  of the closed container  307  and the electric motor  1 . 
     The electric motor  1  is fixed to the closed container  307  by fitting the stator  3  in the closed container  307 . The configuration of the electric motor  1  has been described above. To the closed container  307 , a glass terminal  309  for supplying electric power to the electric motor  1  is fixed by welding. 
     When the electric motor  1  rotates, this rotation is transferred to the swing scroll  302 , and the swing scroll  302  swings. When the swing scroll  302  swings, the volume of the compression chamber formed by the spiral portion of the swing scroll  302  and the spiral portion of the fixed scroll  301  changes. Then, a refrigerant gas is sucked from the suction pipe  310 , compressed, and then discharged from the discharge pipe  306 . 
     The compressor  300  includes the electric motor  1  described in the first embodiment, and thus, has advantages described in the first embodiment. 
     In addition, since the compressor  300  includes the electric motor  1  described in the first embodiment, performance of the compressor  300  can be improved. 
     Third Embodiment 
     A refrigeration air conditioning apparatus  7  serving as an air conditioner and including the compressor  300  according to the second embodiment will be described. 
       FIG. 32  is a diagram schematically illustrating a configuration of the refrigerating air conditioning device  7  according to the third embodiment. 
     The refrigeration air conditioning apparatus  7  is capable of performing cooling and heating operations, for example. A refrigerant circuit diagram illustrated in  FIG. 32  is an example of a refrigerant circuit diagram of an air conditioner capable of performing a cooling operation. 
     The refrigeration air conditioning apparatus  7  according to the third embodiment includes an outdoor unit  71 , an indoor unit  72 , and a refrigerant pipe  73  connecting the outdoor unit  71  and the indoor unit  72  to each other. 
     The outdoor unit  71  includes a compressor  300 , a condenser  74  as a heat exchanger, a throttling device  75 , and an outdoor air blower  76  (first air blower). The condenser  74  condenses a refrigerant compressed by the compressor  300 . The throttling device  75  decompresses the refrigerant condensed by the condenser  74  to thereby adjust a flow rate of the refrigerant. The throttling device  75  will be also referred to as a decompression device. 
     The indoor unit  72  includes an evaporator  77  as a heat exchanger, and an indoor air blower  78  (second air blower). The evaporator  77  evaporates the refrigerant decompressed by the throttling device  75  to thereby cool indoor air. 
     A basic operation of a cooling operation in the refrigeration air conditioning apparatus  7  will now be described. In the cooling operation, a refrigerant is compressed by the compressor  300  and the compressed refrigerant flows into the condenser  74 . The condenser  74  condenses the refrigerant, and the condensed refrigerant flows into the throttling device  75 . The throttling device  75  decompresses the refrigerant, and the decompressed refrigerant flows into the evaporator  77 . In the evaporator  77 , the refrigerant evaporates, and the refrigerant (specifically a refrigerant gas) flows into the compressor  300  of the outdoor unit  71  again. When the air is sent to the condenser  74  by the outdoor air blower  76 , heat moves between the refrigerant and the air. Similarly, when the air is sent to the evaporator  77  by the indoor air blower  78 , heat moves between the refrigerant and the air. 
     The configuration and operation of the refrigeration air conditioning apparatus  7  described above are examples, and the present invention is not limited to the examples described above. 
     The refrigeration air conditioning apparatus  7  according to the third embodiment has the advantages described in the first and second embodiments. 
     In addition, since the refrigeration air conditioning apparatus  7  according to the third embodiment includes the compressor  300  according to the second embodiment, performance of the refrigeration air conditioning apparatus  7  can be improved. 
     Features of the embodiments and features of the variations described above can be combined as appropriate.