阅读说明：本技术 笼型感应电动机以及笼型转子 (Cage-type induction motor and cage-type rotor ) 是由 古川隼人 于 2020-02-11 设计创作，主要内容包括：本发明的笼型感应电动机中抑制导条的发热。笼型感应电动机具备：转子,具有沿轴向延伸被支承为能够旋转的转子轴、安装于转子轴的径向外侧的转子铁心(100)、以及沿周向相互隔开间隔地配置且贯通转子铁心(100)的多个导条(50)；定子,具有配置于转子铁心(100)的径向外侧的定子铁心与沿轴向贯通定子铁心的定子绕组；以及两个轴承,隔着转子铁心(100)在转子轴的轴向的两侧将转子轴支承为能够旋转。多个导条(50)各自的转子铁心(100)内的径向外侧部分随着从径向外侧部分(51)向径向内侧而周向的宽度单调地增大。(The invention provides a cage-type induction motor which can restrain the heating of a conducting bar. A cage-type induction motor is provided with: a rotor having a rotor shaft rotatably supported to extend in an axial direction, a rotor core (100) attached to a radially outer side of the rotor shaft, and a plurality of bars (50) arranged at intervals in a circumferential direction and penetrating the rotor core (100); a stator having a stator core disposed radially outside the rotor core (100) and a stator winding axially penetrating the stator core; and two bearings rotatably supporting the rotor shaft on both sides of the rotor core (100) in the axial direction of the rotor shaft. The width of the radially outer portion of each of the plurality of bars (50) in the rotor core (100) in the circumferential direction increases monotonically from the radially outer portion (51) to the radially inner side.)

1. A cage-type induction motor is characterized by comprising:

a rotor having a rotor shaft extending in an axial direction and rotatably supported, a rotor core attached to a radially outer side of the rotor shaft, and a plurality of bars arranged at intervals in a circumferential direction and penetrating the rotor core;

a stator having a stator core disposed radially outside the rotor core and a stator winding axially penetrating the stator core; and

two bearings rotatably supporting the rotor shaft on both sides of the rotor core in an axial direction of the rotor shaft,

the radially outer portion of each of the plurality of bars in the rotor core has a circumferential width that monotonically increases from the radially outer portion to the radially inner portion.

2. Cage induction motor according to claim 1,

the plurality of conductive bars further have:

a radially inner portion disposed radially inward of the radially outer portion, and having a cross-sectional area perpendicular to a longitudinal direction larger than a cross-sectional area perpendicular to the longitudinal direction of the radially outer portion; and

a coupling portion thermally coupling the radially inner portion and the radially outer portion.

3. Cage induction motor according to claim 1 or 2,

a rotor slot formed in the rotor core through which the bar is inserted communicates with a radial outer surface of the rotor core through an outer opening.

4. A cage rotor is characterized by comprising:

a rotor shaft extending in an axial direction and supported to be rotatable;

a rotor core mounted on a radially outer side of the rotor shaft; and

a plurality of conducting bars which are arranged at intervals in the circumferential direction and penetrate through the rotor core,

the radially outer portion of each of the plurality of bars in the rotor core has a circumferential width that monotonically increases from the radially outer portion to the radially inner portion.

Technical Field

The present invention relates to a cage-type induction motor and a cage-type rotor.

Background

In a cage-type induction motor, generally, the current flowing through the conductor bars of the rotor at the time of starting is several times the rated current. Therefore, a temperature rise due to heat generation of the lead becomes a problem.

In order to secure a starting torque while suppressing a current at the time of starting, a double-squirrel-cage induction motor in which slots are provided on the outer side and the inner side in the radial direction, or a method using a deep-squirrel-cage induction motor in which slots are formed deep in the radial direction is known (see patent documents 1 and 2).

Disclosure of Invention

Problems to be solved by the invention

In both the double-squirrel-cage induction motor and the deep-slot squirrel-cage induction motor, the bar conductors generally have radially outer portions and radially inner portions, and the radially outer portions are made to have a higher resistance than the radially inner portions.

At the time of starting the motor, the frequency of the secondary side is high, and therefore the skin effect is larger than at the time of rated rotation. The current of the conductor bar therefore passes mainly through the radially outer part. As a result, the current of the bar is suppressed to be low.

However, even in a state where the current of the bar flows through the radially outer portion having a large resistance, heat generation may be a problem. Depending on the case, the conductor may be deformed or broken due to the temperature rise caused by the heat generation.

Therefore, an object of the present invention is to suppress heat generation of a conductor in a cage-type induction motor.

Means for solving the problems

In order to achieve the above object, a squirrel cage induction motor according to the present invention includes: a rotor having a rotor shaft extending in an axial direction and rotatably supported, a rotor core attached to a radially outer side of the rotor shaft, and a plurality of bars arranged at intervals in a circumferential direction and penetrating the rotor core; a stator having a stator core disposed radially outside the rotor core and a stator winding axially penetrating the stator core; and two bearings rotatably supporting the rotor shaft on both sides of the rotor core in an axial direction of the rotor shaft, wherein a radially outer portion of each of the plurality of bars in the rotor core monotonically increases in circumferential width from the radially outer portion to the radially inner portion.

Further, the cage rotor of the present invention includes: a rotor shaft extending in an axial direction and supported to be rotatable; a rotor core mounted on a radially outer side of the rotor shaft; and a plurality of bars arranged at intervals in the circumferential direction and penetrating through the rotor core, wherein a radially outer portion of each of the plurality of bars in the rotor core increases in width in the circumferential direction monotonically from the radially outer portion toward the radially inner side.

Effects of the invention

According to the present invention, in the cage-type induction motor, heat generation of the conductor can be suppressed.

Drawings

Fig. 1 is a longitudinal sectional view showing a structure of a cage-type induction motor according to a first embodiment.

Fig. 2 is a front view showing an electromagnetic steel sheet constituting a rotor core of the cage induction motor according to the first embodiment.

Fig. 3 is a partial cross-sectional view showing a slot portion and a bar of a rotor core of a cage induction motor according to a first embodiment.

Fig. 4 is an equivalent circuit diagram of the secondary side for explaining the operation of the cage induction motor according to the first embodiment.

Fig. 5 is a diagram showing a rotational speed-torque characteristic curve for explaining the operation of the cage induction motor according to the first embodiment.

Fig. 6 is a partial cross-sectional view showing a slot portion and a bar of a rotor core of a cage induction motor according to a second embodiment.

Fig. 7 is a partial cross-sectional view showing a slot portion and a bar of a rotor core of a cage induction motor according to a third embodiment.

Fig. 8 is a partial cross-sectional view showing a slot portion and a bar of a rotor core of a cage induction motor according to a fourth embodiment.

Fig. 9 is a partial cross-sectional view showing a slot portion and a bar of a rotor core of a cage induction motor according to a fifth embodiment.

Description of the reference numerals

10 … rotor, 11 … rotor shaft, 18 … gap, 20 … stator, 21 … stator iron core, 22 … stator winding, 30 … bearing, 40 … frame, 45 … bearing bracket, 50a, 50b … conducting bar, 51a, 51b … radial outside part, 51c … front end part, 52a, 52b … radial inside part, 53a … connecting part, 55 … short circuit ring, 59 … cage conductor, 100 … rotor iron core, 100a … rotor slot, 100b … outside opening, 101 … outer surface, 110 … electromagnetic steel plate, 110a … opening, 110b … outer edge, 111 … slot notch, 112 … outside notch, 200 … cage induction motor

Detailed Description

Hereinafter, a cage induction motor and a cage rotor according to the present invention will be described with reference to the drawings. Here, the same or similar portions are denoted by common reference numerals and overlapping description is omitted.

[ first embodiment ]

Fig. 1 is a longitudinal sectional view showing a structure of a cage-type induction motor according to a first embodiment.

The cage type induction motor 200 has a rotor 10, a stator 20, two bearings 30, a frame 40, and two bearing brackets 45.

The rotor 10 includes a rotor shaft 11 extending in the longitudinal direction, a cylindrical rotor core 100 attached to the radially outer side of the rotor shaft 11, and a cage conductor 59 penetrating the rotor core 100. Rotor core 100 is mounted on the radially outer side of rotor shaft 11. The rotor shaft 11 is rotatably supported by bearings 30 on both sides across the rotor core 100.

The cage conductor 59 has a plurality of conductive bars 50 and two shorting rings 55. The plurality of bars 50 are arranged at intervals in the circumferential direction and penetrate through the rotor core 100. The short-circuit rings 55 are disposed on both outer sides of the rotor core 100 in the axial direction, and are coupled to the plurality of bars 50, respectively, to electrically couple the bars 50 to each other.

The stator 20 includes a stator core 21 and a stator winding 22. The stator core 21 is cylindrical and is disposed radially outward of the rotor core 100 via the air gap 18. The stator winding 22 penetrates the stator core 21.

The frame 40 is disposed radially outward of the rotor core 100 and the stator 20, and houses them. Bearing brackets 45 are attached to both ends of the frame 40. Each bearing bracket 45 statically supports the bearing 30.

Fig. 2 is a front view showing an electromagnetic steel sheet constituting a rotor core of the cage induction motor according to the first embodiment. Rotor core 100 includes a plurality of electromagnetic steel plates 110 stacked in the axial direction.

Each of the electromagnetic steel plates 110 is a circular plate having an opening 110a formed at the center thereof, through which the rotor shaft 11 passes. A plurality of slot notches 111 are formed inside the outer edge 110b of the magnetic steel sheet 110 in the radial direction at intervals in the circumferential direction.

Each slot notch 111 communicates with the radial outside by an outer notch 112 formed in the outer edge 110b of the magnetic steel sheet 110.

Fig. 3 is a partial cross-sectional view showing a slot portion and a bar of a rotor core of a cage induction motor according to a first embodiment.

By laminating the magnetic steel sheets 110, the rotor slot 100a and the outer opening 100b having the radial length L1 are formed in the rotor core 100 by the slot notches 111 and the outer notches 112 formed in the magnetic steel sheets 110.

Each rotor slot 100a is provided with a bar 50 having a shape corresponding to the shape of the rotor slot 100 a. In other words, rotor core 100 is formed with rotor slots 100a for passing through bars 50 corresponding to the shape of bars 50. Each bar 50 is inserted from one end of the rotor core 100 in the axial direction, and then both sides are connected to the short ring 55.

The cross section of the bar 50 is a trapezoidal shape whose entire cross section is radial in the height direction, and has a shape of one side lacking the middle in the height direction. Specifically, the present invention includes a radially outer portion 51, a radially inner portion 52, and a coupling portion 53.

The radially outer portion 51 is a trapezoid having a height direction as a radial direction, and a radially inner bottom side is longer than a radially outer upper side. The radially inner portion 52 is disposed radially inward of the radially outer portion 51 in a shape similar to the radially outer portion 51, and has upper and lower sides longer than the radially outer portion 51.

The coupling portion 53 couples the radially outer portion 51 and the radially inner portion 52. The coupling portion 53 is configured such that one side thereof connects respective oblique sides of the radially outer portion 51 and the radially inner portion 52. In fig. 3, a side of the coupling portion 53, the oblique side of the radially outer portion 51, and the oblique side of the radially inner portion 52 are formed on the same straight line, but the present invention is not limited thereto. The positions may be different from each other in the same straight line.

In this way, the radially outer portion 51 and the radially inner portion 52 are shaped so as to have a smaller width in the circumferential direction outward in the radial direction. The cross-sectional area of the radial outer portion 51 in the longitudinal direction, i.e., in the cross-section perpendicular to the rotation axis direction, is smaller than the cross-sectional area of the radial inner portion 52 in the cross-section. Thus, the radially outer portion 51 has a greater electrical resistance than the radially inner portion 52.

The connection portion 53 has a cross-sectional area or a circumferential width sufficient to move heat from the radially outer portion 51 to the radially inner portion 52, which are at a high temperature, at the time of activation.

The shape of the rotor insertion slot 100a has a shape corresponding to the shape of the bar 50. Is sized to be inserted into the bar 50 with the outer surface of the bar 50 being substantially closely adhered to the inner surface of the rotor insertion slot 100 a.

The rotor slot 100a communicates with an outer surface 101, which is an outer surface of the rotor core 100 in the radial direction, through an outer opening 100 b.

The operation of the cage induction motor 200 of the present embodiment configured as described above will be described below.

Fig. 4 is an equivalent circuit diagram of the secondary side for explaining the operation of the cage induction motor according to the first embodiment. The secondary side being a closed circuit, formed by a voltage E generated on the secondary side₂Corresponding power supply, and secondary side resistor r arranged in series with the power supply₂And a secondary side reactance x₂And (4) forming. The equivalent resistance of the secondary side in the slip (in English: slip) s is r₂And s. Here, if the rated rotation speed is set to n₀When the rotation speed n is equal to s, (n) represents slip s₀－n)/n₀And (4) defining.

At this time, the current I of the secondary side₂And the torque T is obtained by the following formulas (1), (2), respectively:

I₂＝E₂/√[(r₂/s)²+(x₂)²]···(1)

T＝K·s(E₂)²r₂/[(r₂)²+(sx₂)²]···(2)

in particular, since s is 1 at the time of starting, the starting current I2s and the starting torque Ts are obtained by the following expressions (3) and (4), respectively. Where K is a constant taking into account mechanical losses.

I₂s＝E₂/√[(r₂)²+(x₂)²]···(3)

Ts＝K·(E₂)²r₂/[(r₂)²+(x₂)²]···(4)

Fig. 5 is a diagram showing a rotational speed-torque characteristic curve for explaining the operation of the cage induction motor according to the first embodiment. The horizontal axis represents the rotational speed n, n₀Is the nominal rotational speed. The vertical axis is the torque T.

Curve A1 is the resistance r of the secondary side₂Is r₂₁The curve A2 represents the resistance r on the secondary side₂Is r₂₂Rotational speed-torque characteristics of time, shown as r₂₂＞r₂₁The case (1). Now, denoted as r₂₂＝k·r₂₁. Where k is a number greater than 1.

As shown in FIG. 5, the resistance on the secondary side is r₂₂In the case where the secondary side resistance is r₂₁K times, the secondary side resistance is made r according to the ratio transition₂₁Rotational speed-torque characteristic curve A1 at rated speed n₀That is, the rotation speed-torque characteristic curve a2 is obtained when s is 0 and the starting point is k times larger in the direction in which s is larger.

Generally, the rotation speed-torque characteristic of the induction motor increases monotonically toward a peak value when n is increased from the start (n is 0). Thus, the cranking torque T2 in the rotation speed-torque characteristic curve a2 is larger than the cranking torque T1 in the rotation speed-torque characteristic curve a 1.

Although the details are omitted, the resistance r of the secondary side₂₂(＝k·r₂₁) The starting current in the case of (2) is larger than the resistance r on the secondary side₂₁The starting current in the case of (2) is small.

In the first embodiment, at the time of starting, the relative speed of the rotor 10 and the rotating magnetic field due to the stator winding 22 is large. That is, the frequency of the magnetic field in which conducting bar 50 is located is large. As a result, the frequency of the induced current flowing through the conductive bar 50 is large. Thus, under the skin effect, the current flowing through the conductor 50 is biased to a portion radially outside the conductor 50.

A radially outer portion 51, which is a radially outer portion of the bar 50, has a smaller width in the circumferential direction toward the radially outer side. That is, at the time of starting, the cross-sectional area of the portion of conducting bar 50 through which the starting current flows is small, and therefore, the resistance is large. As a result, as described with reference to fig. 4 and 5, a large starting torque can be secured while suppressing the starting current.

On the other hand, if the conductor is in the rated state, the current flows also through the radially inner portion 52 of the conductor 50, and the resistance value of the conductor 50 can be reduced while securing a sufficient cross-sectional area, thereby suppressing copper loss during rated operation.

At the time of activation, heat generated in the radially outer portion 51 is transferred to the radially inner portion 52 through the connection portion 53 by heat conduction. The radially inner portion 52 has a sufficiently large heat capacity compared to the radially outer portion 51, and therefore a temperature rise is suppressed. The cross-sectional area through which heat is conducted through the connecting portion 53 is sufficiently large, and temperature distribution in the lead 50 is hardly generated.

As described above, in the cage-type induction motor 200 of the present embodiment, heat generation of the lead 50 can be suppressed.

[ second embodiment ]

Fig. 6 is a partial cross-sectional view showing a slot portion and a bar of a rotor core of a cage induction motor according to a second embodiment.

The second embodiment is a modification of the first embodiment. The rotor core 100 according to the second embodiment includes the rotor slot 100a and the bar 50 having different shapes from those of the first embodiment. Otherwise, the same as the first embodiment.

In the second embodiment, the circumferential position of the coupling portion 53a is arranged at the circumferential center of the radially outer portion 51 and the radially inner portion 52.

With this configuration, the front and back sides are not distinguished from each other in the production of the electrical steel sheet, and the burden on management can be reduced. In addition, there is no need to manage the difference in the direction of the guide bar 50 during assembly, and the burden can be reduced. Further, the selection width of the shape of the conductor 50 is enlarged in design.

[ third embodiment ]

Fig. 7 is a partial cross-sectional view showing a slot portion and a bar of a rotor core of a cage induction motor according to a third embodiment.

The third embodiment is a modification of the first embodiment. In the third embodiment, the outer opening 100b formed in the rotor core 100 in the first embodiment is not formed.

This configuration can be adopted when the heat generation in lead 50 is not so large that heat radiation from the outside opening is not necessary. As a result, the distance L2 between the bar 50 and the outer surface 101 for overcoming the centrifugal force of the bar 50 can be made smaller than the length L1 in the first embodiment. As a result, the gap between stator winding 22 and conducting bar 50 is reduced, and the magnetic coupling force is increased, which also contributes to an improvement in efficiency.

[ fourth embodiment ]

Fig. 8 is a partial cross-sectional view showing a slot portion and a bar of a rotor core of a cage induction motor according to a fourth embodiment.

The fourth embodiment is a modification of the first embodiment. The rotor core 100 according to the fourth embodiment includes rotor slots 100a and bars 50a having different shapes from those of the first embodiment. Otherwise, the same as the first embodiment.

The cross-sectional shapes of the radially outer portion 51a and the radially inner portion 52a of the guide bar 50a in the present embodiment are trapezoidal as a whole. Alternatively, the shape of the connection portion 53 in the first embodiment may be regarded as a trapezoid.

In the fourth embodiment thus formed, the bar 50a has a simple shape, and therefore, the burden of processing or management in manufacturing the bar 50a and the electromagnetic steel sheet 110 is reduced.

[ fifth embodiment ]

Fig. 9 is a partial cross-sectional view showing a slot portion and a bar of a rotor core of a cage induction motor according to a fifth embodiment.

The fifth embodiment is a modification of the fourth embodiment. The rotor core 100 according to the fifth embodiment includes rotor slots 100a and bars 50b having different shapes from those of the fourth embodiment. Otherwise, the same as the fourth embodiment.

The conductor bar 50a in the fourth embodiment linearly increases in width in the circumferential direction from the radially outer side to the inner side in the sectional shape.

On the other hand, the guide strip 50b in the fifth embodiment has a shape in which the circumferential width is linearly expanded from the radially outer side to the radially inner side in each of the radially outer portion 51b and the radially inner portion 52b and the radially outer portion 51b and the radially inner portion 52 b. Conversely, the circumferential width decreases more than linearly toward the radially outer side. The distal end portion 51c is formed not to have an acute angle but to have a rounded shape with a certain curvature.

In the present embodiment thus formed, the passage of the current at the time of starting in the bar 50b can be further narrowed, and the effects of reducing the starting current and securing the starting torque can be further improved.

[ other embodiments ]

The embodiments of the present invention have been described above, but the embodiments are provided as examples and are not intended to limit the scope of the invention. For example, in the embodiment, a case of a horizontal-type rotating electrical machine in which the rotor shaft 11 extends in the horizontal direction is described as an example, but the present invention is not limited to this. A vertical cage induction motor having a rotor shaft extending in the vertical direction may be used.

In addition, the features of the respective embodiments may be combined. The embodiments may be implemented in other various manners, and various omissions, substitutions, and changes may be made without departing from the spirit of the invention. The embodiments and modifications thereof are included in the scope and gist of the invention, and are also included in the scope and equivalents of the invention described in the claims.