JPH07163108A - Induction motor - Google Patents

Abstract

PURPOSE:To obtain an induction motor having excellent characteristics by employing a rotor structure where a short circuit ring can be formed between blocks using a conventional inserter. CONSTITUTION:In an induction motor where secondary conductors are inserted into closed slots 6 made in a rotor 1 to constitute a squirrel-cage winding, a first core section 5 having a wide slot 7 of closed structure is provided in the axial center of the core of the rotor 1 and second and third narrow core sections 4A, 4B having closed structure are provided on the opposite sides of the first core section 5. The wide slot part 7 of the first core section 5 is superposed on the narrow slot parts 6A, 6B of the second and third core sections 4A, 4B. The slots 7 superposed on the first to third core sections 4A, 5, 4B are communicated thus short-circuiting the secondary conductors in the axial center of the rotor core.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction motor, and more particularly to a rotor structure for an induction motor in which a secondary conductor is cast to form a cage winding.

[0002]

2. Description of the Related Art Noise reduction during the operation of an induction motor is a constant proposition, and various methods have been proposed. Generally, in order to prevent abnormal torque, vibration, and noise from occurring during operation of the induction motor, skew is applied to this type of induction motor. However, although noise can be reduced by providing the skew, an induced voltage difference is generated between the secondary conductors, a transverse current is generated through the rotor core, and a cross current loss is generated to reduce the efficiency of the motor. A new problem arises. As a measure for reducing this cross current loss, as described in JP-A-57-49357, a method of dividing the rotor core into two blocks and providing a short-circuit ring between the blocks to short-circuit between the secondary conductors is known. Well known,
It has been implemented.

[0003]

However, in order to form the short-circuit ring of the above-mentioned prior art by casting between blocks, a new casting device dedicated to casting the short-circuit ring is required. Therefore, although the above-mentioned conventional technique is effective in reducing the cross current loss, it is necessary to introduce a dedicated machine, resulting in a high manufacturing cost. Therefore, there has been a demand for an induction motor capable of forming a short-circuit ring having the same function as the above-mentioned conventional example in a casting device that has been conventionally used.

The present invention has been made in view of such a background, and an object thereof is to realize a rotor structure capable of forming a short-circuit ring between blocks by a conventional casting device,
This is to provide an induction motor with good characteristics at low cost.

[0005]

[Means for Solving the Problems] The above object is to provide a stator,
A rotor disposed rotatably with respect to the stator via an air gap, a plurality of slots are provided in the stator core of the stator, and the stator winding of the stator winding is provided in the slots. In the induction motor in which each coil is inserted, a plurality of closed slots are provided in the rotor core of the rotor, and a secondary conductor is cast into the closed slots to form a cage winding. A first iron core portion having a slot having a wide closed slot structure is provided at a central portion in the axial direction of the child iron core, and second and third slots having narrow closed slot structure slots on both sides of the first iron core portion. The core part of
These iron cores are superposed so that the slot portions of the wide closed slot structure of the first iron core portion and the slot portions of the second and third iron core portions having the narrow closed slot structure partially overlap each other, and It is achieved by connecting the overlapping slots of the third to third core parts to short-circuit the secondary conductor at the axial center part of the rotor core.

In this case, the number of slots having a wide closed slot structure formed in the first iron core portion is equal to the number of slots having a narrow closed slot structure formed in the second and third iron core portions. The slot positions of the wide closed slot structure formed in the first iron core portion and the slot positions of the narrow closed slot structure formed in the second and third iron core portions And can be provided in different positions. As the different positions, for example, the slot position of the wide closed slot structure and the slot position of the narrow closed slot structure may differ by 0.5 slot pitch. Furthermore, the outer peripheral portion of the first iron core portion may be cut to expose the short-circuited portion in which the secondary conductor is cast.

[0007]

The rotor core is divided into two blocks of the second and third core parts, the rotor core of each block is provided with a slot having a narrow closed slot structure, and a wide closed slot is provided between these blocks. A first iron core portion having a slot having a slot structure is provided, and the first and second iron core portions have a portion where at least the narrow slot and the wide slot overlap with each other. Sandwich. As a result, the outer ends of the second and third iron core parts communicate with each other through the slot. Therefore, when the secondary conductor is cast in this state, the secondary conductor cast in the narrow slot portions of the second and third iron core portions in the first iron core portion is short-circuited, and the same as in the short-circuit ring. It will have a function.

More specifically, the secondary conductor is formed by a conventional casting apparatus by shifting the slot positions in the iron core shape having a narrow slot structure and the iron core shape having a wide closed slot structure by, for example, 0.5 slot pitch. In addition, it is possible to form a short-circuit ring that short-circuits each secondary conductor between the iron core blocks. That is, since there is no space for hot water (aluminum, etc.) to flow out between the iron core blocks at the time of casting, the secondary conductor can be formed by the conventional casting apparatus, and the secondary conductor is short-circuited by the short-circuit ring, so that the secondary The transverse voltage does not flow through the iron core due to the induced voltage difference generated between the conductors, and the occurrence of cross current loss can be reduced.

[0009]

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

FIG. 1 is a front view of a squirrel cage rotor according to one embodiment of the present invention, and FIG. 2 is a perspective view showing a structure of an induction motor according to the present invention with a part of a stator cut away. 1 and 2, the induction motor basically includes a rotor 1 and a stator 2.

The rotor 1 is provided with second and third iron core portions 4A, 4B having a narrow closed slot structure on the shaft 3, and is formed into a V-shaped skew (slotted by a chain line so that the form of the V-shaped skew can be seen). 6 is specified). A first iron core portion 5 having a wide closed slot structure is provided between the second iron core portion 4A and the third iron core portion 4B, and the second and third iron core portions 5 are provided.
The stacking positional relationship between the iron core portions 4A, 4B and the first iron core portion 5 is shifted by 0.5 slot pitch, as indicated by the chain line at the position of the slot 7 of the first iron core portion 5. The core portions 4A, 4B, 5 are formed by stacking a plurality of cores.

The first to third iron core portions 4A, 4B and 5 thus laminated are high temperature hot water (not shown) in at least one of the second and third iron core portions 4A and 4B in a pouring machine. Of the end rings 8A, 8B and the cooling fins 9A, respectively, outside the second core part 4 and the third core part 5 together with the secondary conductor 10 as shown in the sectional view of FIG. 9B and 9B are formed at the same time.

The stator 2 supports a stator core 12 on the inner circumference of a housing 11, and a stator winding 13 is wound inside the slot. On the lower side of the housing 11 are fixing feet 1.
4 are provided. Further, end brackets 15A and 15B are provided on both sides of the housing 11 and fixed to the housing 11 with bolts 16. Further, since the bearings 17A and 17B provided on both sides of the shaft 3 are supported by the end brackets 15A and 15B, the rotor 1
Are supported on the inner circumference of the stator core 12 via a gap. A guide 18 for cooling air is provided inside the end bracket 15A.

3 and 4 show the shape of the iron core according to the embodiment. FIG. 3 is a front view of the iron core of the first iron core portion, and FIG.
[Fig. 4] is a front view of the iron cores of the second and third iron core portions. In FIG. 3, on the side closer to the outer peripheral portion of the iron core of the first iron core portion 5, slots 7 having a wide slot shape and narrow teeth 20 are concentrically arranged side by side at equal angles. Similarly, in FIG. 4, the slots 7 of the iron cores of the second and third iron core portions 4A and 4B are arranged in the same position at the same position as the slots 6 each having a narrow slot shape and the wide teeth 19 concentrically and at equal angles. ing. As can be seen from FIGS. 3 and 4, the slot 7 is wider than the slot 6, and therefore, when the center of the slot 6 and the center of the tooth 20 are overlapped with each other, the space of the slot 6 is not closed by the tooth 20.

FIG. 5 shows a sectional shape of a rotor core composed of the first to third core portions 4A, 4B and 5 shown in FIGS. 3 and 4, more specifically, as shown in FIG. The core portion 5 is sandwiched between the second and third core portions 4A and 4B and aluminum is cast into the secondary conductor 10 and the end rings 8A and 8A.
3A and 3B when the B and the cooling fins 9A and 9B are formed, the cross sections at the A positions in FIGS.

In FIG. 5, the teeth 19A, 19B and the teeth 20 have been touched before, but since they are displaced by 0.5 slot pitch, the secondary conductor 10 has end rings 8A, 8B.
The first ring corresponding to the intermediate ring 21
All the slots 7 of the iron core part 5 are also short-circuited.

Therefore, when there is a difference in induced voltage between the secondary conductors in each slot, since the specific resistance of the short-circuit ring 21 is smaller than the specific resistance of the iron core portions 4A and 4B, a transverse current flows through the short-circuit ring 21. Since the resistance is small, the generated cross current loss is small. In addition, when the rotor is exposed to a harmonic magnetic field, such as when it is controlled by an inverter, the impedance on the rotor side is small, so a harmonic current that suppresses the harmonic magnetic field will flow, reducing vibration and noise. is there.

FIG. 6 is a sectional development view showing a sectional shape of a rotor core according to another embodiment of the present invention. In the figure, the difference from FIG.
Aligned with the center of slot 6 of A, 4B, the other is core part 4
It is centered on the teeth 19A and 19B of A and 4B. As a result, the short-circuit ring 21 in which the secondary conductor 10 is short-circuited in all the slots 6 and 7 can be reliably formed.

FIG. 7 is a sectional development view showing a sectional shape of a rotor core according to another embodiment of the present invention. In the figure, the difference from FIG. 5 is that the center positions of the teeth 19A and the teeth 19B are shifted by 0.5 slot pitch, and the teeth 20
One of the positions is aligned with the center of the slot 6 between the teeth 19A, and the other is aligned with the center of the slot 6 between the teeth 19B. This allows all slots 6,7
It is possible to reliably form the short-circuit ring 21 in which the secondary conductor 10 is short-circuited at the portion.

In the present embodiment, the iron core is present above the short-circuit ring 21, but as shown in FIG. 8, the iron core above the short-circuit ring 21 is connected to the rotor 1 due to the leakage flux. It goes without saying that it may be deleted when processing the outer peripheral surface of. By doing so, the secondary conductor 10
It is possible to improve the cooling performance of the rotor 1, and thus the cooling performance of the rotor 1.

FIG. 9 is a front view showing the shape of the first iron core portion 5 according to another embodiment of the present invention. The slot has a wide closed slot structure set wider than that of the embodiment shown in FIG. 7 and narrow teeth 20 are provided, and the number of slots 7 is the same as the second and third iron core portions 4A and 4B shown in FIG.
The number of slots 6 is less than the number of slots. From these figures, the slot 7 is significantly wider than the slot 6, so if the center of the slot 6 and the center of the tooth 20 are aligned,
The space of slot 6 is not blocked by teeth 20
It can be seen that the coupling between the secondary conductor 10 and the short-circuit ring 21 can be further strengthened. Needless to say, also in this embodiment, the arrangements shown in FIGS. 6 and 7 can be selected. Further, in this embodiment, an induction motor having a V-shaped skew is shown, but it goes without saying that a general straight skew may be used.

[0022]

As is apparent from the above description, the present invention configured as described above has the following effects.

That is, a first iron core portion having a slot having a wide closed slot structure is provided in the central portion in the axial direction of the rotor iron core, and narrow slots having a closed slot structure are provided on both sides of the first iron core portion. The second and third iron core portions having the same are provided, and at least a part of the wide closed slot structure slot of the first iron core portion and the slot having the narrow closed slot structure of the second and third iron core portions are overlapped. According to the invention of claim 1, wherein the overlapping slots of the first to third iron core portions are communicated with each other to short-circuit the secondary conductor at the axial center portion of the rotor iron core. Since there is no space for the hot water to flow between the iron cores of the
The secondary conductor and the short-circuit ring are integrally formed. As a result, the transverse current does not flow through the iron core due to the induced voltage difference generated between the secondary conductors, the occurrence of cross current loss can be reduced, and an inexpensive and excellent induction motor can be provided.

The number of slots having a wide closed slot structure formed in the first iron core portion is larger than the number of slots having a narrow closed slot structure formed in the second and third iron core portions. The invention according to claim 2, wherein the number of slots is set small, the position of the slot of the wide closed slot structure formed in the first iron core portion and the narrow closed slot structure formed in the second and third iron core portions The invention according to claim 3, wherein the slot positions are different from each other, and the slot positions of the wide closed slot structure formed in the first iron core part, and the second and third iron core parts. The slot position of the closed slot structure having a narrow width is different by 0.5 slot pitch.
According to the described invention, since the communication between the slots can be ensured, there is an effect that a short circuit of the secondary conductor can be surely performed in addition to the above effect.

According to the invention of claim 5, wherein the outer peripheral portion of the first iron core portion is cut to expose the cast-in portion (short-circuited portion) of the secondary conductor, in addition to the above effects, the secondary conductor and, by extension, rotation This has the effect of efficiently cooling the child.

[Brief description of drawings]

FIG. 1 is a front view of a squirrel cage rotor according to an embodiment of the present invention.

FIG. 2 is a perspective view in which a stator of an induction motor according to the present invention is partially cut away.

FIG. 3 is a front view showing the shape of the first core portion of the rotor according to the embodiment.

FIG. 4 is a front view showing the shapes of second and third iron core portions of the rotor according to the embodiment.

FIG. 5 is a cross-sectional view showing a cross-sectional shape of the rotor core taken along line A of the rotor formed by combining the first to third iron core parts according to the embodiment and casting the secondary conductor. .

FIG. 6 is a cross-sectional view showing a cross-sectional shape of a rotor core according to another embodiment.

FIG. 7 is a sectional view showing a sectional shape of a rotor core according to still another embodiment.

FIG. 8 is a front view of a squirrel-cage rotor according to another embodiment in which the outer periphery of the short-circuit ring portion is cut.

FIG. 9 is a front view of a first iron core portion having a wide slot structure formed with a smaller number of slots than the second iron core portion.

[Explanation of symbols]

 1 Rotor 2 Stator 3 Shaft 4A Second Iron Core Part 4B Third Iron Core Part 5 First Iron Core Part 6, 7 Slot 8A, 8B End Ring 9A, 9B Cooling Fin 10 Secondary Conductor 11 Frame 12 Stator Iron Core 13 Stator winding 15A, 15B End bracket 19A, 19B, 20 Teeth 21 Shorting ring

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroyuki Mikami 7-1, 1-1 Omika-cho, Hitachi-shi, Ibaraki Hitachi Ltd. Hitachi Research Laboratory (72) Inventor Mika Takahashi Seven, Mika-machi, Hitachi-shi, Ibaraki 1-chome 1 Hitachi Ltd. Hitachi Research Laboratory (72) Inventor Shoji Senoo 4-6 Kanda Surugadai, Chiyoda-ku, Tokyo Hitachi Industrial Co., Ltd. Industrial Equipment Division (72) Inventor Tsuyoshi Omata Kanda, Chiyoda-ku, Tokyo Surugadai 4-6, Hitachi, Ltd. Industrial Equipment Division

Claims (5)

[Claims] 1. A stator, and a rotor rotatably arranged with respect to the stator via an air gap,
The stator core of the stator is provided with a plurality of slots, the coils of the stator winding are inserted in the slots, and the rotor core of the rotor is provided with a plurality of closed slots. An induction motor having a cage winding formed by casting a secondary conductor in the closed slot, wherein a first iron core portion having a slot having a wide closed slot structure is provided in a central portion in the axial direction of the rotor iron core. At the same time, second and third iron core portions having narrow closed slot structure slots are provided on both sides of the first iron core portion, and the first iron core portion has a wide closed slot structure slot and the second and third iron core portions. At least a part of slots having a narrow closed slot structure of the third core portion are overlapped, and the overlapped slots of the first to third core portions are made to communicate with each other so that the cast secondary conductor is connected to the rotor core. Short-circuited in the axial center of Induction motor characterized by 2. The number of slots having a wide closed slot structure formed in the first iron core portion is equal to the number of slots having a narrow closed slot structure formed in the second and third iron core portions. The induction motor according to claim 1, wherein the number is set smaller than the number. 3. A position of a wide slot of the closed slot structure formed in the first iron core portion and a position of a narrow slot of the closed slot structure formed in the second and third iron core portions. The induction motor according to claim 1 or 2, wherein and are provided at different positions. 4. The slot of the wide closed slot structure formed in the first iron core portion and the narrow closed slot structure formed in the second and third iron core portions at different positions. 4. The induction motor according to claim 3, wherein the slot is different from the slot of the slot by 0.5 slot pitch. 5. The outer peripheral portion of the first iron core portion is cut,
The induction motor according to any one of claims 1 to 4, wherein a cast portion of the secondary conductor is exposed.