JP6660667B2 - Rotating electric machine and its rotor - Google Patents

Description

  The present invention relates to a rotor of a rotary electric machine having a cage secondary conductor, and more particularly to a rotor suitable for an induction motor or the like using a conductor bar.

  The squirrel-cage induction motor has a squirrel-cage rotor and a stator that generates a rotating magnetic field.The squirrel-cage rotor has a rotor shaft, a rotor core in which a plurality of electromagnetic steel plates are laminated, a plurality of conductor bars and And a secondary conductor comprising an end ring. The secondary conductor is formed by filling a plurality of slots formed in the rotor core with a conductive material in a molten state.

  In the conventional cage-type induction motor, Patent Documents 1 and 2 disclose a known example of a joint shape between a conductor bar and an end ring in which a slot in an electromagnetic steel plate or an end plate near an end ring is enlarged to cut a conductor bar. It is disclosed that the area is increased. Patent Document 3 discloses a conventional technique for chamfering a rotor slot.

JP 2014-147253 A JP 2011-10498 A JP 2009-11067 A

  Patent Literature 1 discloses that in each conductor bar, the strength of the joint portion between the conductor bar and the end ring is reduced by forming the end portion in the axial direction so as to draw an arc having a larger outer radius than the center portion in the axial direction. It is disclosed to increase the damage of the secondary conductor due to the centrifugal force accompanying the high-speed rotation. According to Patent Document 2, the rotor core has a configuration in which end plates are provided at both ends of an electromagnetic steel plate, and the end plate has a slot area larger than that of the electromagnetic steel plate to reduce current concentration and reduce stress. It is disclosed to reduce concentration. Patent Document 3 discloses that by forming chamfers around slots of an electromagnetic steel sheet located at both ends in the axial direction of a rotor core, high tensile stress generated at the base of a conductor bar and a short-circuit ring is reduced. Is disclosed.

However, when the squirrel-cage induction motor is used for a low-temperature gas transfer pump such as liquefied natural gas (LNG) or liquid nitrogen (LN ₂ ), or when used as a power source in outer space, the ambient environment must be from -100 ° C. When the temperature drops to about -200 ° C, the material of the conductor bar and the end ring constituting the secondary conductor has a larger linear expansion coefficient than the material of the magnetic steel sheet. appear. The generation of the stress due to the temperature change is not limited to the extremely low temperature environment, and the generated stress may damage the secondary conductor. However, Patent Documents 1 to 3 do not suggest this problem at all.

  An object of the present invention is to solve this problem and to provide a robust and reliable rotor for a rotating electrical machine even when the temperature changes in a low-temperature environment or the like.

  Other objects and features of the present invention will become apparent from the following description and the following description of embodiments.

In order to solve the above-described problems, to give an example of a typical "rotating electric machine" of the present invention, the rotating electric machine has a stator and a rotor, and the rotor has a rotor shaft and a cylindrical body in which electromagnetic steel sheets are laminated. A rotor core, a plurality of rotor slots circumferentially spaced around an outer peripheral surface of the rotor core, a conductor bar embedded in the rotor slot, and the rotor core. An end ring that is installed at both ends of the conductor bar and short-circuits each of the conductor bars to form a cage-shaped secondary conductor, wherein the secondary conductor is made of a conductive material filled in a molten state. is intended to be formed, the large linear expansion coefficient than the magnetic steel sheets in the axial end of the rotor core, includes an end plate of a material linear expansion coefficient smaller than that of the secondary conductor, the electrical steel sheet diameter and Ri diameter equal der of said end plate, said rotating The inner surface in the vicinity of the axial end portion of the slot comprises an interference suppression layer, the axially central portion of the rotor slots is characterized in that there is no the interference suppression layer.

In addition, to give an example of a typical "rotor of a rotating electric machine" of the present invention, a cylindrical rotor core in which electromagnetic steel sheets are laminated, and a circumferential interval around an outer peripheral surface of the rotor core are provided. A plurality of rotor slots, conductor bars embedded in the rotor slots, and short-circuited connection between the conductor bars provided at both ends of the rotor core to form a cage-shaped secondary conductor. End ring, and a rotor shaft, the rotor of the rotating electrical machine comprising: the secondary conductor is formed of a conductive material filled in a molten state, the rotor core wherein the axial end portion larger linear expansion coefficient than the electromagnetic steel sheet, provided with an end plate of a material linear expansion coefficient smaller than that of the secondary conductor, Ri diameter as the same der of the end plate of the electrical steel sheet Interferes with the inner surface near the axial end of the rotor slot Comprising a control layer, the axially central portion of the rotor slots is characterized in that there is no the interference suppression layer.

  ADVANTAGE OF THE INVENTION According to this invention, the rotor of a durable and highly reliable rotating electric machine can be provided even at the time of temperature changes, such as a low temperature environment.

FIG. 2 is a partial sectional view of a rotor of the squirrel-cage induction motor according to the first embodiment of the present invention. It is a fragmentary sectional view of the rotor of the cage induction motor of Example 2 of the present invention. It is a fragmentary sectional view of the rotor of the cage induction motor of Example 3 of the present invention. FIG. 10 is a view illustrating a shape of an end plate portion of a rotor core according to a third embodiment of the present invention. It is a fragmentary sectional view of the rotor of the cage induction motor of Example 4 of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings for describing the embodiments, elements having the same functions are denoted by the same names and reference numerals, and repeated description thereof will be omitted.

  FIG. 1 is a partial sectional view of a rotor of a squirrel-cage induction motor according to Embodiment 1 of the present invention. The rotor 10 includes a rotor core 21, a cage-shaped secondary conductor 30, and a rotor shaft 11 installed on the inner peripheral side of the rotor core 21. A plurality of rotor slots 22 are provided in the vicinity of the outer peripheral surface of the rotor core 21 at intervals in the circumferential direction. The cage-shaped secondary conductor 30 is composed of conductor bars 31 embedded in the rotor slots 22 and end rings 32 installed at both ends of the rotor core 21 and short-circuiting the respective conductor bars 31. . The secondary conductor 30 is formed by filling a plurality of rotor slots 22 of the rotor core 21 with a conductive material in a molten state by die casting or the like. The rotor core 21 has a configuration in which end plates 24 are laminated on both ends of a laminated electromagnetic steel plate 23. The end plate 24 is formed of a material having a higher linear expansion coefficient than the electromagnetic steel plate 23 and a lower linear expansion coefficient than the secondary conductor 30.

The linear expansion coefficient of the magnetic steel sheet 23 whose main component is iron is about 12 × 10 ⁻⁶ / K near normal temperature, and about 9 × 10 ⁻⁶ / K near the extremely low temperature of -100 ° C. to −200 ° C. The linear expansion coefficient of the secondary conductor 30 whose main component is made of aluminum is about 21 × 10 ⁻⁶ / K near normal temperature, and about 16 × 10 ⁻⁶ / K near similar low temperature. Further, the boiling point of LNG is -162 ° C., the boiling point of the LN ₂ is -196 ° C., or when the surrounding environment of the rotor 10 is these refrigerant, when the ambient temperature of the rotor 10 is greatly lowered to room temperature Then, the temperature of each member constituting the rotor 10 reaches an extremely low temperature of about −200 ° C. to about −200 ° C., and thermally shrinks. Due to the difference in the coefficient of linear expansion described above, the secondary conductor 30 undergoes a larger dimensional change with respect to the rotor core 21, so that the secondary conductor 30 and the rotor core 22 near the bottoms at both ends of the rotor slot 22. Are concentrated due to the interference, and tensile stress in the axial direction and shear stress in the radial direction are generated at the boundary 33 between the conductor bar 31 and the end ring 32. In particular, when the rotor size is larger than that of a medium-sized machine, the generated stress increases, which causes a reduction in the material life of the secondary conductor 30.

  According to the present embodiment, the end plates 24 at both ends of the rotor core 21 are made of a material having a coefficient of linear expansion larger than that of the electromagnetic steel plate 23 and smaller than that of the secondary conductor 30, so that the above-described cryogenic environment or the like can be used. When the temperature changes, the stress generated at the boundary portion 33 is reduced. In particular, by making the linear expansion coefficient of the end plate 24 closer to the linear expansion coefficient of the secondary conductor 30 as compared with the electromagnetic steel sheet 23, the radial shear stress acting on the boundary portion 33 is reduced even when the temperature changes, and the secondary It is possible to suppress a reduction in the material life of the conductor 30. Further, a robust and highly reliable rotor for a rotating electric machine can be provided.

  The rotating electric machine having the rotor according to the present embodiment suppresses a reduction in the material life of the secondary conductor due to a temperature change. For example, liquefied natural gas or liquid exposed to an extremely low temperature environment of about −100 ° C. to −200 ° C. It is suitable for an electric motor for a pump for transporting a low-temperature gas such as nitrogen.

  Second Embodiment FIG. 2 is a partial cross-sectional view of a squirrel-cage induction motor rotor according to a second embodiment of the present invention. An interference suppression layer 41 is provided near both ends of the rotor slot 22 of the rotor core 21. Then, the secondary conductor 30 is formed by filling the plurality of rotor slots 22 of the rotor core 21 with a conductive material in a molten state. Examples of the interference suppression layer 41 include chromium oxide and unsaturated polyester resin conventionally used as a rotor slot insulating material. In the present embodiment, the unsaturated polyester resin is more preferable depending on the form of the material. It is suitable.

  By providing the interference suppression layers 41 near both ends of the rotor slot 22, direct contact between the rotor slot 22 and the secondary conductor 30 at the end of the rotor core can be avoided. Is obtained, it is possible to reduce the interference between the rotor slot 22 and the secondary conductor 30 at the time of a temperature change such as when the temperature is extremely low, and to reduce the stress generated at the boundary 33 between the conductor bar 31 and the end ring 32. . The effect of the present embodiment is greater when used in combination with the first embodiment.

  Third Embodiment FIG. 3 is a partial sectional view of a rotor of a squirrel-cage induction motor according to a third embodiment of the present invention. In the third embodiment, in the rotor core 21, the slot shape of the end plate 24 is gradually increased toward the end with respect to the slot shape of the electromagnetic steel plate 23.

  FIG. 4 shows the shape of the end plate 24 of the rotor core 21 excluding the secondary conductor 30. The figure on the right side of FIG. 4 is a view of the end plate 24 viewed from the axial direction of the rotor shaft, and reference numerals 22a, 22b, and 22c represent the shapes of the rotor slots. 4 (A), (B), and (C) on the left side of FIG. 4 show the shape of the end plate 24 and the like viewed from a direction perpendicular to the axis of the rotor slot 22. From the viewpoint of relieving stress concentration, the change in the size of the slot shape of the end plate 24 does not necessarily have to be a step-like shape as shown in FIG. 4A, and a plurality of end plates 24a and 24a as shown in FIG. Even if the size of the end plates 24b is uniformly changed in one stage, or the size of the end plates 24a and 24b is continuously changed as shown in FIG. good.

  By gradually increasing the slot shape of the end plate 24 toward the end, the contact between the bottoms at both ends of the rotor slot 22 of the rotor core 21 and the secondary conductor 30 is dispersed, and stress concentration is reduced. At the same time, the mechanical strength of the boundary 33 can be increased by increasing the cross-sectional area of the boundary 33 between the conductor bar 31 and the end ring 32. In this embodiment, the effect is further enhanced by using it in combination with the first embodiment.

  FIG. 5 is a partial sectional view of a rotor of a squirrel-cage induction motor according to Embodiment 4 of the present invention. This embodiment is a combination of the second embodiment and the third embodiment.

  As shown in the third embodiment, in the rotor core 21, the slot shape of the end plate 24 is gradually increased toward the end with respect to the slot shape of the electromagnetic steel plate 23. Then, the interference suppression layer 41 is provided near both ends of the rotor slot 22 of the rotor core 21, that is, near the slot of the end plate 24, in which the slot shape is gradually increased toward the end.

  According to the present embodiment, stress concentration is more effectively achieved by providing the interference suppression layer 41 of the second embodiment mainly in the space created by enlarging the slot shape of the end plate 24 in the third embodiment. Can be alleviated. In addition, the effect of the present embodiment is further enhanced by using it in combination with the first embodiment.

The fifth embodiment defines the material of the end plate, and will be described with reference to FIG. In this embodiment, an austenitic stainless steel or nickel steel is used as the material of the end plate 24 in the first embodiment. Both are materials having improved low-temperature brittleness with respect to ordinary steel, and are suitable as materials for forming the end plate 24 of the present invention. Among the austenitic stainless steels, a typical 18Cr-8Ni steel (SUS304) has a linear expansion coefficient of about 17 × 10 ⁻⁶ / K at around normal temperature and about 15 × 10 at extremely low temperature of −100 ° C. to −200 ° C. ⁻⁶ / K, which is an intermediate value with respect to the linear expansion coefficient of the electromagnetic steel sheet 23 and the secondary conductor 30, and is generated at the boundary 33 between the conductor bar 31 and the end ring 32 by applying to the end plate 24. Stress can be reduced. Nickel steel has a feature that the coefficient of linear expansion changes greatly depending on the ratio of the amount of Ni. However, since 18% Ni to 20% Ni steel takes a value of about 20 × 10 ⁻⁶ / K at room temperature, An effect similar to that of the aforementioned 18Cr-8Ni steel is obtained. In addition, the present embodiment further enhances the effect when used in combination with the second to fourth embodiments.

  Although the squirrel cage induction motor has been described in each of the above embodiments, the present invention is not limited to the motor, but can be applied to a rotor of a rotating electric machine including a generator.

  ADVANTAGE OF THE INVENTION According to this invention, a robust and highly reliable rotating electric machine can be provided, and this invention can be used for all the rotating electric machines provided with a cage rotor. In particular, it is suitable for a low-temperature electric motor having a large temperature change, for example, an electric motor for a low-temperature gas transfer pump for liquefied natural gas or liquid nitrogen.

Reference Signs List 10 rotor 11 rotor shaft 21 rotor core 22 rotor slot 22a rotor slot (first end plate portion)
22b Rotor slot (second end plate)
22c Rotor slot (electromagnetic steel plate)
23 Electromagnetic steel plate 24 End plate 24a First end plate 24b Second end plate 30 Secondary conductor 31 Conductor bar 32 End ring 33 Boundary part 41 Interference suppression layer

Claims (10)

A rotor having a stator and a rotor, wherein the rotor is provided with a rotor shaft, a cylindrical rotor core formed by laminating electromagnetic steel plates, and a circumferential interval around an outer peripheral surface of the rotor core. A plurality of rotor slots, a conductor bar embedded in the rotor slot, and an end ring which is installed at both ends of the rotor core and short-circuits the conductor bars to form a cage-shaped secondary conductor. A rotating electric machine comprising:
The secondary conductor is formed of a conductive material filled in a molten state,
An axial end of the rotor core has a larger linear expansion coefficient than the electromagnetic steel sheet, and has an end plate made of a material having a smaller linear expansion coefficient than the secondary conductor,
Wherein Ri diameter equal der diameter and said end plate of electromagnetic steel sheets,
A rotating electric machine comprising: an interference suppression layer provided on an inner surface near an axial end of the rotor slot; and the interference suppression layer does not exist at an axial center of the rotor slot . The rotating electric machine according to claim 1,
The size of the rotor slot is larger at the axial end than at the axial center,
A rotating electric machine, wherein the slot shape of the end plate is gradually increased toward the end with respect to the slot shape of the electromagnetic steel sheet. In the rotating electric machine according to claim 1 or 2 ,
Rotating electric machine, wherein the material of the interference suppression layer is chromium oxide or unsaturated polyester resin. In the rotating electric machine according to any one of claims 1 to 3 ,
A rotating electric machine wherein the material of the end plate is austenitic stainless steel or nickel steel. The rotating electric machine according to any one of claims 1 to 4 , wherein the rotating electric machine is used at a low temperature of about -100 ° C to -200 ° C. The rotating electric machine according to any one of claims 1 to 5 , wherein the rotating electric machine is a motor for a low-temperature gas transfer pump. A cylindrical rotor core in which electromagnetic steel sheets are laminated, a plurality of rotor slots installed in the vicinity of the outer peripheral surface of the rotor core at intervals in the circumferential direction, and a conductor bar embedded in the rotor slot And an end ring that is installed at both ends of the rotor core and short-circuits the respective conductor bars to form a cage-shaped secondary conductor, and a rotor shaft, and a rotor of a rotating electric machine, comprising:
The secondary conductor is formed of a conductive material filled in a molten state,
An axial end of the rotor core has a larger linear expansion coefficient than the electromagnetic steel sheet, and has an end plate made of a material having a smaller linear expansion coefficient than the secondary conductor,
Wherein Ri diameter equal der diameter and said end plate of electromagnetic steel sheets,
A rotor for a rotating electrical machine , comprising: an interference suppression layer provided on an inner surface near an axial end of the rotor slot; and the interference suppression layer does not exist at an axial center of the rotor slot . The rotor of the rotating electric machine according to claim 7 ,
The size of the rotor slot is larger at the axial end than at the axial center,
A rotor of a rotating electrical machine, wherein a slot shape of the end plate is gradually increased toward an end with respect to a slot shape of the electromagnetic steel sheet. In the rotor of the rotating electric machine according to claim 7 or 8 ,
The rotor of a rotating electric machine material of the interference suppression layer, characterized in that chromium oxide or unsaturated polyester resin. The rotor according to any one of claims 7 to 9,
A rotor for a rotary electric machine, wherein a material of an end plate used for an axial end of the rotor core is austenitic stainless steel or nickel steel.

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