CN111903037B

CN111903037B - Rotor of induction motor and induction motor

Info

Publication number: CN111903037B
Application number: CN201880091130.7A
Authority: CN
Inventors: 小野树; 大熊仁明; 立木宏纪
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2018-03-16
Filing date: 2018-03-16
Publication date: 2021-08-17
Anticipated expiration: 2038-03-16
Also published as: WO2019176107A1; JPWO2019176107A1; JP6667731B2; CN111903037A

Abstract

A rotor (60) of an induction motor comprises: a rotor core (61); and conductor bars (63) that are respectively provided in a plurality of groove portions formed in the rotor core (61). A rotor (60) of an induction motor is characterized by comprising: an end ring (64) that is provided at an axial end of the rotor core (61) and that electrically connects the plurality of conductor bars (63) to each other; an insulating sheet (66) which is an insulating member provided between a wall surface (61a) forming the groove portion and the conductor bar (63); and a die-cast member (65) which is a nonmagnetic conductive material provided between the wall surface (61a) and the insulating sheet (66).

Description

Rotor of induction motor and induction motor

Technical Field

The present invention relates to a rotor of an induction motor, which is an induction-type rotating electrical machine, and an induction motor having the rotor.

Background

The induction type rotating electric machine has a strong structure and is inexpensive in manufacturing cost as compared with the synchronous type rotating electric machine, and is widely used because it can be directly connected to a power supply to start the machine. An induction type rotating electric machine is hereinafter sometimes referred to as an induction machine.

In the induction machine, an alternating current flows through a winding of a stator to generate a rotating magnetic field, and the rotating magnetic field acts on a secondary conductor of a rotor, thereby generating an electromotive force in the secondary conductor of the rotor and flowing a current. The secondary conductor of the rotor is composed of an end ring provided in the rotor core and a rotor bar inserted into the rotor core. An electromagnetic force based on fleming's left-hand rule is generated between the current and the rotating magnetic field, whereby the secondary conductor is stretched in the direction of the rotating magnetic field and the rotor rotates. In the induction machine configured as described above, the rotation efficiency of the rotor can be improved by reducing the resistance of the current path flowing through the secondary conductor.

By using copper having a relatively low resistivity as the material of the rotor bar, the resistance of the secondary conductor may be reduced to improve the rotational efficiency.

Further, the cross current loss caused by the unnecessary current flowing through the rotor is reduced, and the rotation efficiency of the induction machine can be improved. The cross current loss is a loss generated when a potential difference is generated between the secondary conductor and the rotor core when a deflection amount is applied to the secondary conductor, and a current that should not originally flow is caused to flow between the secondary conductor and the rotor core.

As a method for reducing the cross current loss, as disclosed in patent document 1, a method is conceivable in which a wall surface provided in a rotor core and forming a groove portion is impregnated with an insulating agent and then the insulating agent is cured to provide an insulating agent layer on the wall surface. By providing the insulating agent layer, insulation resistance between the wall surface forming the groove portion and the rotor bar is increased, current flowing from the rotor bar toward the rotor core is suppressed, and a cross current loss is reduced.

Patent document 1: japanese patent laid-open No. 2001-25222

Disclosure of Invention

However, according to the method disclosed in patent document 1, in order to form an insulating agent layer on a wall surface of the rotor core on which the groove portion is formed, a groove for applying an insulating agent to the rotor core and a furnace for curing the insulating agent are required. Therefore, if the size of the rotor core is increased, it is necessary to increase the size of the slots and the furnace, and therefore, it is necessary to manufacture the slots and the furnace corresponding to the size of the rotor core, which causes a problem of lowering the production efficiency of the rotor.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a rotor of an induction motor capable of improving production efficiency while suppressing a decrease in rotation efficiency due to a cross-flow loss.

In order to solve the above problems and achieve the object, a rotor of an induction motor according to the present invention includes: a rotor core; and conductor bars provided in the plurality of grooves formed in the rotor core, respectively. The rotor of an induction motor is characterized by comprising: an end ring provided at an axial end of the rotor core and electrically connecting the plurality of conductor bars to each other; an insulating member which is an insulating coating film covering the surface of the conductor bar; and a nonmagnetic conductive material provided between a wall surface forming the groove portion and the insulating member, wherein a width of the insulating coating in the axial direction is narrower than a width of the rotor core in the axial direction.

ADVANTAGEOUS EFFECTS OF INVENTION

The rotor of an induction motor according to the present invention has an effect of improving the production efficiency while suppressing a decrease in the rotation efficiency due to the cross-flow loss.

Drawings

Fig. 1 is a diagram showing a structure of an induction motor according to embodiment 1 of the present invention.

Fig. 2 is an oblique view of a rotor of the induction motor shown in fig. 1.

Fig. 3 is an oblique view of a rotor core of the induction motor shown in fig. 1.

Fig. 4 is a diagram showing a state in which an insulating sheet is being inserted into a slot portion of the rotor core shown in fig. 1.

Fig. 5 is an enlarged view of the insulating sheet inserted into the slot portion of the rotor core shown in fig. 4.

Fig. 6 is a diagram showing a state in which the conductor bars are being inserted into the insulating sheet shown in fig. 4.

Fig. 7 is a view showing a state in which end rings are provided at both ends of the rotor core shown in fig. 6.

Fig. 8 is an external view of a conductor bar used in a rotor of an induction motor according to embodiment 2 of the present invention.

Fig. 9 is an oblique view of a rotor core into which the conductor bars shown in fig. 8 are inserted.

Fig. 10 is a cross-sectional view of a rotor having the rotor core and conductor bars shown in fig. 9.

Fig. 11 is a view showing a state in which end rings are provided at both ends of the rotor core shown in fig. 10.

Fig. 12 is a cross-sectional view of the rotor core, the end rings, and the conductor bars shown in fig. 11.

Fig. 13 is a structural diagram of an insulating member provided in a conductor bar according to modification 1 of embodiment 2 of the present invention.

Fig. 14 is a structural diagram of an insulating member provided in a conductor bar according to modification 2 of embodiment 2 of the present invention.

Fig. 15 is a structural diagram of an insulating member provided in a conductor bar according to modification 3 of embodiment 2 of the present invention.

Fig. 16 is an external view of a conductor bar used in a rotor of an induction motor according to embodiment 3 of the present invention.

Detailed Description

Hereinafter, a rotor of an induction motor and an induction motor according to an embodiment of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the embodiments.

Embodiment 1.

Fig. 1 is a diagram showing a structure of an induction motor according to embodiment 1 of the present invention. Fig. 2 is an oblique view of a rotor of the induction motor shown in fig. 1. Fig. 3 is an oblique view of a rotor core of the induction motor shown in fig. 1.

Fig. 1 shows a cross section of an induction motor 100 according to embodiment 1 on one side. In fig. 1, the axial direction, which is the direction in which the central axis AX of the rotor core 61 extends, is the direction indicated by an arrow D1 in fig. 1. The circumferential direction of the central axis AX of the rotor core 61 is the direction indicated by an arrow D2 in fig. 1.

The induction motor 100 includes: a bottomed cylindrical frame 11; an end plate 12 that closes the opening of the frame 11; an annular stator 10 fixed to an inner peripheral surface of the frame 11; a bearing 1 provided at the bottom of the frame 11; and a bearing 2 provided to the end plate 12. The frame 11 and the end plate 12 constitute the casing 3.

The induction motor 100 further includes: a cylindrical rotor 60 provided inside the stator 10; and a shaft 70 rotatably supported by the bearings 1 and 2 and provided inside the rotor 60.

The rotor 60 has a cylindrical rotor core 61 formed by laminating a plurality of steel plates in the axial direction. The rotor core 61 is provided with a plurality of grooves 62. The plurality of grooves 62 are formed so as to be arranged in the circumferential direction near the outer peripheral surface of the rotor core 61, and each of the plurality of grooves 62 extends in the axial direction and penetrates from one end portion to the other end portion of the rotor core 61. Each of the plurality of groove portions 62 has an offset amount in the circumferential direction of the groove portion 62.

Further, the rotor 60 includes: a conductor bar 63 provided inside the plurality of groove portions 62; end rings 64 which are end-winding rings provided at both ends of the rotor core 61 in the axial direction and connect the plurality of conductor bars 63; and a die-cast member 65 which is a nonmagnetic conductive material.

As the material of the conductor bar 63, a nonmagnetic conductor material such as aluminum, an aluminum alloy, copper, or a copper alloy can be exemplified.

Next, a method of manufacturing the rotor 60 will be described with reference to fig. 4 to 7. Fig. 4 is a diagram showing a state in which an insulating sheet is being inserted into a slot portion of the rotor core shown in fig. 1. Fig. 5 is an enlarged view of the insulating sheet inserted into the slot portion of the rotor core shown in fig. 4. Fig. 6 is a diagram showing a state in which the conductor bars are being inserted into the insulating sheet shown in fig. 4. Fig. 7 is a view showing a state in which end rings are provided at both ends of the rotor core shown in fig. 6.

In manufacturing the rotor 60, first, the rotor core 61 and the insulating sheet 66 having a V-shape as viewed in the axial direction are manufactured.

The insulating sheet 66 is formed into a V-shape as shown in fig. 4 by folding an insulating sheet made of a material having high heat resistance, such as meta-aramid or mica.

Next, one end portion in the axial direction of the manufactured insulating sheet 66 is folded back, whereby a folded-back portion 661 in a collar shape is formed in the insulating sheet 66. The insulating sheet 66 formed with the folded portion 661 is inserted into the groove portion 62. The V-shaped apex of the insulating sheet 66 faces the central axis side. The other end portion of the insulating sheet 66 inserted into the groove portion 62 is also provided with the same folded portion 661.

Next, as shown in fig. 6, the strip-shaped conductor bars 63 are inserted into the inner sides of the insulating sheets 66 inserted into the groove portions 62. When the conductor bars 63 are inserted into the insulating sheet 66, the inner surface of the insulating sheet 66 is pressed by the conductor bars 63, and the insulating sheet 66 is spread toward the wall surfaces forming the groove portions 62.

By providing the folded portions 661, even when the conductor bars 63 are inserted into the insulating sheet 66 inserted into the groove portions 62, the insulating sheet 66 is brought into contact with the conductor bars 63, and the folded portions 661 are hooked to the end portions of the rotor core 61, thereby suppressing the movement of the insulating sheet 66 in the axial direction. Therefore, the production efficiency of the rotor 60 is improved compared to the case where the folded-back portions 661 are not provided.

Then, as shown in fig. 7, the nonmagnetic conductive material is used as a die-cast material, and the end rings 64 and the die-cast member 65 are provided on the one end surface 61b and the other end surface 61c of the rotor core 61 in the axial direction, respectively. The 2 end rings 64 and the die-cast member 65 are collectively formed by die-casting.

The end ring 64 has a function of electrically connecting the plurality of conductor bars 63 to each other and a function of fixing each of the plurality of conductor bars 63 to the rotor core 61.

The die-cast member 65 is provided in the gap between the wall surface 61a forming the groove portion 62 and the insulating sheet 66 and the gap between the conductor bar 63 and the insulating sheet 66.

Further, a method of forming the secondary conductor in the groove portion 62 includes a method of forming the secondary conductor by die casting by flowing a molten die casting material into the groove portion 62 without providing the conductor bar 63 in the groove portion 62 in advance. As described above, when the secondary conductor is formed in the groove portion 62 in a state where the conductor bar 63 is not inserted into the inside of the insulating sheet 66, the end portion in the axial direction of the insulating sheet 66 is buckled by the die-casting pressure, and there is a possibility that the buckled end portion in the axial direction of the insulating sheet 66 enters the groove portion 62.

When the insulating sheet 66 is buckled as described above, a portion where the insulating sheet 66 is not present is generated between the wall surface 61a forming the groove portion 62 and the die-cast member 65 provided in the groove portion 62. Therefore, the insulation resistance between the rotor core 61 and the die-cast member 65 shows a lower value than when the insulation sheet 66 is not buckled. Therefore, the cross flow loss generated in the rotor 60 has a larger value than the cross flow loss generated in the rotor 60 when the insulation sheet 66 is not buckled.

Further, the groove portion 62 may be closed by the crimped insulating sheet 66. In this case, the passage of the die-casting material into the groove portion 62 is hindered, and there is a possibility that a portion where the die-casting material is not filled in the space inside the insulating sheet 66 is generated. In this case, the rotational efficiency of the rotor 60 is reduced as compared with the case where the insulating sheet 66 is not buckled.

According to the rotor 60 of embodiment 1, since the conductor bars 63 are provided inside the insulating sheet 66, even when die-casting pressure is applied to the insulating sheet 66, the insulating sheet 66 is supported by the conductor bars 63, and thus buckling of the insulating sheet 66 can be suppressed.

Therefore, after the die cast member 65 is formed, the insulating sheet 66 can be interposed between the conductor bars 63 and the rotor core 61. Therefore, the insulation resistance between the rotor core 61 and the die-cast member 65 is higher than that when the insulation sheet 66 is buckled. As a result, the cross-flow loss generated in the rotor 60 has a value lower than that of the cross-flow loss generated in the rotor 60 when the insulating sheet 66 is buckled.

Further, since the passage of the die-cast material into the groove portion 62 is not hindered, it is possible to suppress the occurrence of a portion not filled with the die-cast material in the space inside the insulating sheet 66. Therefore, the rotation efficiency of the rotor 60 is improved as compared with the case where the insulating sheet 66 is buckled, and the conductor bars 63 inserted into the inside of the insulating sheet 66 can be firmly fixed by the die-cast material.

Further, according to embodiment 1, since there is no need to provide an insulating agent layer on the wall surface 61a where the groove portion 62 is formed, a groove for applying an insulating agent to the rotor core 61 and a furnace for forming an insulating agent layer by curing the insulating agent are not required. Therefore, even when the size of the rotor core 61 is increased, the production of the slots and the furnace corresponding to the increased size of the rotor 60 is not required, and the production efficiency of the rotor 60 is improved.

In addition, the rotor core 61 needs to be heated to form the insulating agent layer, and the time required for the heating is long. According to the rotor 60 of embodiment 1, since the step of forming the insulating agent layer on the wall surface 61a where the groove portion 62 is formed is not required, the production efficiency of the rotor 60 is greatly improved.

Among the materials of the conductor bars 63, a material having a smaller specific resistance is selected preferentially than a material having a lower melting point in the nonmagnetic conductor material, and thereby the rotational efficiency of the rotor 60 can be improved. In the material used for die casting, a material having a lower melting point is preferably selected as the nonmagnetic conductive material than a material having a lower specific resistance, whereby the production efficiency of the rotor 60 can be improved. Therefore, for example, by selecting copper as the material of the conductor bars 63 and aluminum as the material of the end ring 64 and the die-cast member 65, the rotational efficiency and the production efficiency of the rotor 60 can be improved.

Embodiment 2.

Fig. 8 is an external view of a conductor bar used in a rotor of an induction motor according to embodiment 2 of the present invention. In the conductor bars 63 used in the induction motor 100 according to embodiment 2, the portions of the surfaces of the conductor bars 63 near the center in the axial direction are covered with the insulating coating 90, and the portions near the ends in the axial direction are not covered with the insulating coating 9.

As the material of the insulating film 90, a material having high heat resistance such as silica or mica can be exemplified. For example, a highly heat-resistant material is sprayed on the surface of the conductor bar 63 at a portion near the center in the axial direction by a sprayer, and then the conductor bar 63 is heated and dried to form the insulating coating 90. The method of forming the insulating film 90 is not limited to this, and the insulating film 90 may be formed on the surface of the conductor bar 63 by a plating action using an aqueous solution containing a material having high heat resistance as an electrolyte.

Fig. 9 is an oblique view of a rotor core into which the conductor bars shown in fig. 8 are inserted. Fig. 10 is a cross-sectional view of a rotor having the rotor core and conductor bars shown in fig. 9. Fig. 11 is a view showing a state in which end rings are provided at both ends of the rotor core shown in fig. 10. Fig. 12 is a cross-sectional view of the rotor core, the end rings, and the conductor bars shown in fig. 11.

Fig. 9 and 10 show a state in which the conductor bars 63 are inserted into the plurality of groove portions 62 so that the center positions of the conductor bars 63 in the axial direction coincide with the center positions of the rotor core 61 in the axial direction.

In fig. 10, the width of the portion where the insulating coating 90 is formed within the length of the conductor bar 63 in the axial direction is indicated by Y. The width from one end face to the other end face of the rotor core 61 in the axial direction is represented by X. In the rotor 60A according to embodiment 2, the width Y of the insulating film 90 in the axial direction is set to a value shorter than the width X of the rotor core 61 in the axial direction in consideration of assembly tolerance.

The reason for the above-described configuration is that, as shown in fig. 11 and 12, it is necessary to electrically connect the plurality of conductor bars 63 to each other via the end rings 64. The end ring 64 is formed by die casting using a die casting material after the conductor bars 63 are inserted into the groove portions 62.

Due to assembly tolerances of components constituting the rotor 60, manufacturing errors when forming the insulating coating 90, and the like, when the end ring 64 is provided in a state where the insulating coating 90 is formed at a portion protruding from an end of the rotor core 61 in the conductor bars 63 inserted into the rotor core 61, the plurality of conductor bars 63 are separated from each other, and the secondary resistance increases. The increase in the secondary resistance reduces the rotational efficiency of the rotor 60, and reduces the output of the induction motor 100.

In the induction motor 100 according to embodiment 2, since the portions close to the end portions of the conductor bars 63 are not covered with the insulating coating 90, the plurality of conductor bars 63 are electrically connected to each other when the end rings 64 are provided, and an increase in the secondary resistance is suppressed.

Further, according to the induction motor 100 according to embodiment 2, since the same effects as those of embodiment 1 can be obtained and the insulating sheet 66 does not need to be inserted into the groove portion 62, the rotor 60A can be easily manufactured even when the sectional area of the groove portion 62 of the rotor core 61 is small.

Since the heat capacity of the conductor bars 63 is smaller than the heat capacity of the rotor core 61, the insulating coatings 90, which are insulating agent layers, can be provided on the conductor bars 63 in a shorter time using an oven having a smaller heat capacity than when the rotor core 61 is placed in the oven and the insulating agent layers are provided on the wall surfaces 61a where the groove portions 62 are formed. Therefore, in embodiment 2, the production efficiency of the rotor 60A can be improved as compared with the case where the rotor core 61 is placed in the furnace.

Fig. 13 is a structural diagram of an insulating member provided in a conductor bar according to modification 1 of embodiment 2 of the present invention. The conductor bar 63 shown in fig. 13 is provided with a plurality of insulating members 90A. The plurality of insulating members 90A are provided apart from each other in the axial direction.

The insulating members 90A may be provided on the surface of the conductor bar 63 by masking the surface of the conductor bar 63 so as to be separated from each other in the axial direction at a plurality of locations and then spraying a material having high heat resistance onto the conductor bar 63, or may be provided on the conductor bar 63 by plating a material having high heat resistance.

In addition, in each of the plurality of insulating members 90A, an insulating member formed in a ring shape using a material having high heat resistance may be fitted to the conductor bar 63.

Fig. 14 is a structural diagram of an insulating member provided in a conductor bar according to modification 2 of embodiment 2 of the present invention. The conductor bar 63 shown in fig. 14 is provided with a spiral insulating member 90B. The insulating member 90B may be formed by applying a spiral mask on the surface of the conductor bar 63 and then applying a material having high heat resistance to the conductor bar 63 by spray coating, or may be formed by applying a material having high heat resistance to the conductor bar 63 by plating coating.

The insulating member 90B may be formed by spirally winding a strip-shaped insulating sheet having high heat resistance around the conductor bars 63.

Fig. 15 is a structural diagram of an insulating member provided in a conductor bar according to modification 3 of embodiment 2 of the present invention. The conductor bar 63 shown in fig. 15 is provided with an eye-needle-shaped insulating member 90C. The insulating member 90C may be formed by winding a needle-eye-shaped insulating sheet having high heat resistance around the conductor bars 63, or may be formed by attaching a needle-eye-shaped cylindrical body having high heat resistance to the conductor bars 63.

By providing any one of the insulating

members

90A, 90B, and 90C to the conductor bars 63, the amount of material used for the insulating members can be reduced, and therefore, the manufacturing cost of the rotor 60A can be reduced.

Embodiment 3.

Fig. 16 is an external view of a conductor bar used in a rotor of an induction motor according to embodiment 3 of the present invention. In the induction motor 100 according to embodiment 3, the conductor bars 63A are used instead of the conductor bars 63 shown in fig. 6.

The conductor bar 63A is formed of a plurality of thin wires 63 b. The plurality of thin wire materials 63b are bundled by an insulating sheet 91. The insulating sheet 91 before bundling the plurality of thin wire members 63b is in a band shape. The strip-shaped insulating sheet 91 is wound in a state where a plurality of thin wire materials 63b are bundled, thereby forming 1 conductor bar 63A.

In embodiment 3, the same effects as those of embodiment 1 can be obtained, and by changing the wire diameters of the plurality of thin wires 63b and changing the use of the thin wires 63b according to the change, the cross-sectional shape orthogonal to the axial direction of the conductor bar 63A can be easily changed in accordance with the cross-sectional shape orthogonal to the axial direction of the groove portion 62. Therefore, the shape of the conductor bars 63A can be made to correspond to various types of rotor cores 61 having different sectional shapes of the groove portions 62, and therefore, the production efficiency of the rotor 60 is improved.

The configuration described in the above embodiment is an example of the content of the present invention, and may be combined with other known techniques, and a part of the configuration may be omitted or modified without departing from the scope of the present invention.

Description of the reference numerals

1. 2 bearing, 3 casing, 10 stator, 11 frame, 12 end plate, 60A rotor, 61 rotor iron core, 61a wall surface, 61B one end surface, 61C other end surface, 62 slot part, 63A conductor bar, 63B thin wire, 64 end ring, 65 die casting component, 66, 91 insulation sheet, 70 shaft, 90 insulation coating, 90A, 90B, 90C insulation component, 100 induction motor, 661 folded back part.

Claims

1. A rotor of an induction motor, comprising:

a rotor core;

conductor bars provided in a plurality of grooves formed in the rotor core, respectively;

an end ring provided at an axial end of the rotor core and electrically connecting the plurality of conductor bars to each other;

an insulating member which is an insulating coating film covering the surface of the conductor bar; and

a nonmagnetic conductive material provided between a wall surface forming the groove portion and the insulating member,

the width of the insulating coating in the axial direction is narrower than the width of the rotor core in the axial direction.

2. The rotor of an induction motor according to claim 1,

the material of the conductor bars is copper,

the non-magnetic conductor material and the end ring are each aluminum.

3. The rotor of an induction motor according to claim 1 or 2,

the conductor bar is integrally formed by bundling a plurality of wires.

4. A rotor of an induction motor, comprising:

a rotor core;

a plurality of insulating members covering a part of the surface of the conductor bar, the insulating members being disposed apart from each other in the axial direction; and

and a nonmagnetic conductive material provided between a wall surface forming the groove portion and the plurality of insulating members.

5. A rotor of an induction motor, comprising:

a rotor core;

an insulating member covering a part of a surface of the conductor bar at spirally spaced intervals; and

and a nonmagnetic conductive material provided between the wall surface forming the groove portion and the insulating member.

6. A rotor of an induction motor, comprising:

a rotor core;

an eyelet-shaped insulating member that covers a surface of the conductor bar; and

7. An induction motor, comprising:

a rotor of the induction motor of any one of claims 1 to 6; and

a stator provided with the rotor inside.