JPH1052013A - Induction motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an induction motor having a rotor structure suppressing the increase of its leakage magnetic flux when its rotor has a skew structure. SOLUTION: Forming in a rotor core 4 slots 3 having both enclosed slot structures with applied skews and their maximum circumferential dimensions Wb (maximum widths), alluminum aloys, for example, are cast in the slots 3 to form secondary conductors 5 in them. After forming the secondary conductors 5, in the portion of the outer periphery of the rotor core 4 wherein each slot 3 is positioned, a slit 18 is provided by notching this portion within the scope of the maximum circumferential dimension Wb of each slot 3 in the parallel direction with the rotating shaft of a rotor 1. For example, when providing the slits 18 one by one in all the cross sections of the secondary conductors 5, the slits 18 are formed in the respective regions of the slots 3, each of which ranges from one end side of each slot 3 to its other end side correspondingly to its foregoing maximum dimension Wb, in order intermittently ranging from the lead side of the skew to its delay side. Thereby, the slots 3 are altered from the enclosed type ones into semi-enclosed type ones.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction motor,
In particular, the present invention relates to an induction motor characterized by a slot structure of a rotor of the induction motor.

[0002]

2. Description of the Related Art Noise reduction during operation of an induction motor is an ongoing proposition, and various methods have been proposed. As means for suppressing noise, vibration, and abnormal torque at startup, it is common to use a skew structure for the rotor. However, although providing the skew solves the above-described problems, the power factor of the electric motor decreases because the leakage reactance newly increases.

Here, an induction motor having such a skew structure will be described. FIG. 7 is a partially cutaway perspective view showing the structure of this type of induction motor. In the figure, the induction motor M is basically composed of a rotor 1, a stator 8, a housing 9, and an end bracket 14.

[0004] The rotor 1 is fitted into the outer periphery of the shaft 2 and rotates integrally therewith. A conductor is cast into a rotor iron plate 4 having a slot 3 having a skewed fully closed slot structure. A secondary conductor 5 is formed on both ends of the rotor iron plate 4 and end rings 6 (6A, 6A)
B) is fitted, and cooling fins 7 (7A, 7B) are formed on the outer surface of the end ring 6.

The stator 8 is housed in a cylindrical housing 9 and end brackets 14A and 14B at both ends, and is wound around a slot 11 of a stator core 10 supported on the inner peripheral surface of the housing 9. It has a winding 12. The housing 9 is provided with fixing feet 13 at the lower portion, and end brackets 14 (14A, 14A)
B) is fixed. Here, since the bearings 16 (16A, 16B) provided on both sides of the shaft 2 are supported by the end bracket 14, the rotor 1 is
Is rotatably supported on the inner periphery of the device via a gap.

The slot 3 in the rotor iron plate 4 of the rotor 1 generally has a sectional structure as shown in FIG. That is, in FIG. 8, a secondary conductor 5 is formed in the slot 3 by casting a conductor into a rotor iron plate 4 having a slot 3 having a skewed fully closed slot structure. For this reason, due to the fact that the slot 3 has a fully-closed slot structure, the outer peripheral portion of the rotor 1 becomes the magnetic bridge 17, and the magnetic flux leaks to the same portion, and the power factor decreases due to an increase in the leakage reactance. I do. This increase in the leakage reactance becomes particularly remarkable when the rotor 1 has a skew structure. On the other hand, since magnetic flux containing many harmonic components is concentrated on the magnetic bridge portion 17, there is a problem that the loss increases locally and it is difficult to improve the efficiency.

As a countermeasure against this, Japanese Patent Laid-Open Publication No. 1-2746
As described in JP-A-49-149 and JP-A-56-145753, a method has been proposed in which a rotor slot has a semi-closed slot structure.

[0008]

However, each of the above prior arts has a structure capable of reducing the leakage reactance of the rotor. However, in the invention described in Japanese Patent Application Laid-Open No. 1-274649, the secondary conductor is formed of a rotor slot. It will be cast to the opening. For this reason, a harmonic component of the secondary current flows intensively in the slot opening, causing a problem that the loss increases and the efficiency decreases.

Further, in the invention described in Japanese Patent Application Laid-Open No. 56-145,753, the secondary conductor at the slot opening, which is a problem in the former case, is removed by laser beam irradiation. It is difficult to remove the conductor, and in the case of a skewed rotor, the setting of the irradiation position of the beam is complicated, and the process takes time.

The present invention has been made in view of the above points, and an object thereof is to provide an induction motor having a rotor structure capable of suppressing an increase in leakage magnetic flux when the rotor has a skew structure. . Another object is to provide an induction motor having a rotor structure that can suppress an increase in leakage magnetic flux without requiring a complicated process.

[0011]

In order to achieve the above object, the present invention is directed to a stator and a rotor which are opposed to each other via a gap, and a plurality of slots are provided in a stator core of the stator. In the induction motor, each coil of the stator winding is inserted therein, and a number of skewed closed slots are provided in the rotor core of the rotor, and a plurality of secondary conductors are cast in the closed slots. The outer peripheral portion of the rotor core where the closed slot is located is within the range of the maximum circumferential dimension of the closed slot and smaller than the longitudinal dimension of the rotor core, and has a depth within the closed slot. The slit is provided to reach the secondary conductor.

In this case, it is preferable that the slit is provided in parallel with the axis of the rotor. Further, it is preferable that at least one slit is provided in each of the closed slots.

Further, the rotor core is divided into a plurality of regions in the axial direction, and the slits are sequentially arranged from the leading side of the skew with respect to the rotating direction of the rotor to the lag side in each of the regions of each closed slot. It can also be provided parallel to the axis of the child.

Further, the rotor core is divided into a plurality of regions in the axial direction, and the slits are formed in the respective regions so that the slits alternate in both the axial direction and the circumferential direction of each closed slot. The skew may be provided parallel to the axis of the rotor from the leading side to the lagging side in the direction.

Further, the slit may be provided in parallel with the axis of the rotor only on the leading side of the skew with respect to the rotation direction of the rotor and only on the end side of the rotor core.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

[First Embodiment] FIG. 1 is a plan view of a rotor of an induction motor according to a first embodiment of the present invention. In FIG. 1, a rotor 1 according to the present embodiment includes a shaft 2
And the rotor iron plate 4 fitted and laminated on the shaft 2
And a pair of end rings 6 (6A, 6B) located at both ends of the rotor iron plate 4. The rotor iron plate 4 is provided with a skewed slot 3 having a maximum dimension (maximum width) in the circumferential direction and a skewed fully closed slot structure. The secondary conductor 5 is formed in the slot 3 by casting aluminum or an aluminum alloy. After the secondary conductor 5 is formed by casting in this way, the outer peripheral portion of the portion of the rotor core 4 where the slot 3 is located is provided within the range of the maximum circumferential dimension Wb of the slot 3 and the rotor 1 A slit 18 is provided by cutting a notch in a direction parallel to the rotation axis (shaft 2). FIG. 1 shows a case where one slit 18 is provided in each of the cross sections of all the secondary conductors 5. In other words, when the slit 18 is provided in parallel, each of the regions from the one end side corresponding to the maximum dimension Wb of the slot 3 to the other end side (here, divided into three regions R1, R2, R3). The slot 18 is extended from the leading side of the skew to the lag side by 18
a, 18b, 18c, 18 for slot 3b
a ′, 18b ′, 18c ′, 1 for slot 3c
8a ", 18b", 18c ", and so on. The leading side of the skew refers to the side located forward with respect to the rotation direction of the rotor 1. Although aluminum or an aluminum alloy is used as the secondary conductor in this example, it goes without saying that a conductive material such as copper can also be used.

When the slit 18 is formed as described above,
For example, in the AA 'cross section shown in FIG. 2, the slit 3 has a cut (radial height Hs) reaching the secondary conductor 5 substantially at the center of the slot 3 in the circumferential direction. That is, in FIG. 2, the rotor iron plate 4 of the rotor 1 has a slot 3 in which the secondary conductor 5 is cast, and a slit 18 is formed on the outer peripheral portion of the rotor core 4 where the slot 3 is located. It is formed within a range of the maximum direction dimension Wb and in a direction parallel to the rotation axis (shaft 2) of the rotor 1. On the other hand, since the slot 3 of this type of rotor 1 has a skew structure as described above, the formation position of the slit 18 is shifted in the circumferential direction of the slot 3, and the relative positions of the two are as shown in FIGS. It will be different. Here, FIG.
FIG. 4 is a sectional view taken along line B ′, and FIG. 4 is a sectional view taken along line CC ′ in FIG. For this reason, Hs which is the radial height of the slit 18 in FIG. 2 is set so that the structure of the slot 3 has a semi-closed slot shape in each of the cross sections shown in FIGS. That is, Hs is determined so that the secondary conductor 5 can be visually confirmed inside the slit 18 from the outer peripheral side of the rotor 1. Here, the radial height Hs of the slit 18
Hs> Hb in relation to the thickness Hb of the magnetic bridge 17 shown in FIG.

By configuring the rotor 1 of the induction motor M as described above, the leakage magnetic flux generated in the magnetic bridge portion 17 can be greatly reduced by the slit 18, so that the power factor can be improved by reducing the leakage reactance. In addition, efficiency can be improved by reducing the loss. Further, when the slit 18 is provided in a direction parallel to the rotation axis of the rotor 1 (the axis of the shaft 2), positioning for the slit processing is easy and the process time can be shortened. can do.

[Second Embodiment] FIG. 5 is a plan view of a rotor of an induction motor according to a second embodiment of the present invention. This embodiment is similar to the slit 18 of the first embodiment.
However, in the axial direction from the skew advance direction to the skew advance direction,
In this embodiment, the slits 18 are formed alternately in both the axial direction and the circumferential direction, as shown in FIG. 5, while the slits 18 are formed in all of the divided regions R1, R2, and R3. The number of slits 18 is greatly reduced. That is, in the first embodiment, the slits 18 are arranged in each of the regions R1, R2, and R3 of the three rows of slots 3a, 3b, and 3c shown in FIG. Although it is formed stepwise, in this second embodiment, the slit 18b formed in the region R2 in FIG. 1 is omitted for the slot 3a, and the regions R1 and R1 are formed for the slot 3b.
R3 slits 18a'18c 'are omitted and slot 3
As for c, the slit 18b ″ in the region R2 is omitted. Since all other components are configured in the same manner as in the first embodiment, overlapping descriptions are omitted.

Unnecessary slit 1 is formed on the outer peripheral surface of rotor 1
It is known that the provision of 8 increases the pulsating component of the gap permeance and the equivalent gap length, and the pulsating component of the gap permeance is one of the causes of loss and lowers the efficiency. It is also known that an increase in the length leads to a decrease in the excitation reactance, which leads to a reduction in power factor and a reduction in efficiency due to an increase in copper loss.

In contrast, in the second embodiment shown in FIG. 5, an increase in the equivalent gap length due to the provision of the slit 18 can be suppressed, and the effect of providing the slit 18 can be utilized.

[Third Embodiment] In the case of an induction motor employing a skew structure, the distribution of the magnetic flux density at the outer periphery of the rotor in the direction of the rotating shaft is determined by the skew leading side with respect to the rotating direction of the rotor. It is known that the temperature of the rotor in this portion also locally rises.
FIG. 6 is a plan view of a rotor of an induction motor according to a third embodiment for solving this problem. This embodiment is characterized in that the slit 18 is provided only on the leading side of the skew in the rotation direction of the rotor 1 and on the end side of the rotor core 4 with respect to the embodiment of FIG.

That is, in this embodiment, as shown in FIG. 6, the slits 18a, 18a ', 18a "are formed only in the portions corresponding to the region R1 of each of the slots 3a, 3b, 3c, and the other regions R2, R3 Are not formed with slits 18, and the other parts are configured in the same manner as the other embodiments.

By providing the slits 18 in this way, it is of course possible to greatly suppress the leakage flux in the portion where the magnetic flux density is high, but the gap length in the portion is increased equivalently, so that the gap The reluctance can be increased and the non-uniformity in the distribution of the magnetic flux density in the rotation axis direction can be corrected. Therefore, it is possible to obtain an induction motor in which the rotor temperature is well-balanced, with the generated loss caused by the magnetic flux density not being concentrated on a local portion.

In the examples shown in FIGS. 1, 5 and 6, the area is such that the length Ls of the slit 18 in the direction of the rotation axis is made as long as possible with respect to the maximum circumferential width Wb of the slot 3. Although the length is set to be equal to R1, R2, and R3, it is needless to say that the leakage reactance and the equivalent gap length can be finely adjusted by arbitrarily adjusting the length Ls. Further, in consideration of the increase in the equivalent gap length due to the slit installation, by providing at least one slit within the dimension range in the rotation axis direction of the secondary conductor, the characteristics of the motor according to the conventional structure shown in FIG. It is clear from the above embodiments that the characteristics can be improved. Further, in these embodiments, the slit 18 is formed parallel to the axis of the rotating shaft (shaft 2). However, the slit 18 does not need to be particularly parallel unless the easiness of machining is considered.

[0027]

As is apparent from the above description, according to the present invention, the leakage magnetic flux caused by the skew structure and the closed slot structure of the rotor is greatly reduced by forming the slit reaching the slot. So you can
The power factor can be improved by reducing the leakage reactance and the efficiency can be improved by reducing the loss, whereby an induction motor having good characteristics can be obtained.

Further, when slits are provided in a direction parallel to the rotation axis of the rotor, positioning for slit processing is easy, and the time required for processing including setup time can be shortened. An induction motor having characteristics can be provided at low cost.

[Brief description of the drawings]

FIG. 1 is a plan view of a rotor of an induction motor according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of a main part of the rotor slot, taken along line AA ′ of FIG. 1;

FIG. 3 is a cross-sectional view of a main part of the rotor slot taken along a line BB ′ in FIG. 1;

FIG. 4 is a cross-sectional view of a main part of the rotor slot taken along a line CC ′ in FIG. 1;

FIG. 5 is a plan view of a rotor of an induction motor according to a second embodiment of the present invention.

FIG. 6 is a plan view of a rotor of an induction motor according to a third embodiment of the present invention.

FIG. 7 is a partially cutaway perspective view showing a structure of an induction motor according to a conventional example.

FIG. 8 is a sectional view of a main part showing a closed slot structure of a rotor of an induction motor according to a conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Rotor 2 Shaft 3, 3a, 3b, 3c Slot 4 Rotor core 5 Secondary conductor 6 End ring 7 Cooling fin 8 Stator 9 Housing 10 Stator core 11 Stator slot 12 Stator winding 13 Feet for fixing 14 End Bracket 15 Bolt 16 Bearing 17 Magnetic Bridge 18, 18a, 18b, 18c, 18a ', 18b'1
8c ', 18a ", 18b", 18c "Slit R1, R2, R3 regions

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Mika Takahashi 7-2-1, Omika-cho, Hitachi City, Ibaraki Pref. Hitachi, Ltd. Power and Electricity Development Division (72) Inventor Kenzo Kajiwara Sachiyuki Hitachi, Ibaraki 3-1-1, Machi-cho, Hitachi, Ltd.Hitachi Plant (72) Inventor Shoji Senoo 7-1-1, Higashi-Narashino, Narashino-shi, Chiba Industrial Machinery Division, Hitachi, Ltd.

Claims (6)

[Claims] 1. A stator and a rotor are opposed to each other via a gap, a number of slots are provided in a stator core of the stator, and each coil of a stator winding is inserted into the slots. In an induction motor in which a number of skewed closed slots are provided in a rotor core of a rotor and a plurality of secondary conductors are cast in the closed slots, the closed core is provided around an outer peripheral portion of the rotor core where the closed slots are located. A slit is provided within the maximum circumferential dimension of the slot, smaller than the longitudinal dimension of the rotor core, and having a depth reaching the secondary conductor in the closed slot. Induction motor. 2. The induction motor according to claim 1, wherein the slit is provided in parallel with a rotation axis of the rotor. 3. The induction motor according to claim 2, wherein at least one slit is provided in each of the closed slots. 4. The rotor core is divided into a plurality of regions in an axial direction, and the slit is provided in each of the regions of each closed slot in order from a leading side of a skew in a rotating direction of the rotor to a lagging side. The induction motor according to claim 2, wherein: 5. The rotor core is divided into a plurality of regions in the axial direction, and the slits are formed in the respective regions so that the slits are alternately arranged in the axial direction and the circumferential direction of each closed slot. The induction motor according to claim 2, wherein the skew is provided in order from a leading side to a lagging side in the direction. 6. The induction motor according to claim 2, wherein the slit is provided only on the leading side of the skew with respect to the rotation direction of the rotor and only on the end side of the rotor core.