JPH1127887A - Cage-shaped rotor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cage-shaped rotor which can reduce lateral flow loss. SOLUTION: This rotor 21 has an iron core 23, where flat rolled magnetic steel sheets are stacked in an axial direction under the condition such that they are insulated from one another, and a rotor bar 25 which is set in a slot 24 made at the periphery of this iron core 23, and also has fixing parts 27 where rotor bars 25 are stuck fast firmly to the iron core 23, at plural places in the axial direction of the slot 24. Then, the fixing parts 27 are arranged, so that the fellow adjacent fixing parts 27 in the circumferential direction out of these fixing parts 27 do not overlap each other in the axial direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cage rotor of a cage rotating electric machine.

[0002]

FIG. 3 is a front view of a cage rotor of a conventional cage induction motor, and FIG. 4 is an enlarged sectional view of a fixing portion provided on the cage rotor.

As shown in FIG. 3, an iron core 3 is fixed to an outer periphery of a shaft 2 which is a rotating shaft of the cage rotor 1. The iron core 3 is formed by laminating electromagnetic steel sheets having a surface coated with an insulating film in the axial direction (left-right direction in FIG. 3). A plurality of slots (grooves) 4 are formed in the outer peripheral portion of the iron core 3 in the axial direction and at predetermined intervals in the circumferential direction. In the slots 4, rotor bars (copper bars) 5 as rotor conductors are respectively provided. Mated. Both ends of the rotor bar 5 are connected to an end ring 6.

[0004] The iron core 3 and the rotor bar 5 are brought into close contact with each other at a plurality of locations in the axial direction of the slot 4 so that the rotor bar 5
Is fixedly provided to the iron core 3.
Since the rotor bar 5 is subjected to electromagnetic force and thermal stress at the time of starting, centrifugal force during operation, and the like, the fixing portion 7 is provided to withstand these forces.

[0005] The fixing portion 7 is formed by a method shown in FIGS. That is, as shown in FIG.
4 by deforming the outer peripheral portion (ie, the iron core 3).
As shown in FIG. 3B, the end of the rotor bar 5 is deformed by hitting the slug 11 with a hammer (not shown) so that the iron core 3 and the rotor bar 5 are brought into close contact with each other.
Is firmly fixed to the iron core 3. The work of fixing the rotor bar 5 to the iron core 3 by deforming the iron core 3 or the rotor bar 5 with a rag and a hammer is generally called caulking. The length L ₂ of the fixing unit 7 is generally 10~30mm
It is.

[0006]

In the above-described conventional cage rotor 1, as shown in FIG. 3, the fixing portions 7 of all the slots 4 are provided at the same position in the axial direction. This is because workability and fixing of the rotor bar 5 are considered. However, since the fixing portions 7 adjacent to each other in the circumferential direction are at the same position in the axial direction, the cross current (current) I flows through the iron core 3 (through the electromagnetic steel sheet) as indicated by an arrow in FIG. It is in an easy state. When the cross flow I flows, a cross flow loss occurs, and the temperature of the cage rotor 1 increases.

[0007] The cage rotor of most cage-type induction motors generally has oblique slots (skew slots).
However, the cross flow loss is particularly likely to occur in the cage rotor having the slanted slots. FIG. 5 is a front view of a cage rotor of a conventional cage induction motor having oblique slots.

As shown in FIG. 1, an iron core 13 is provided on an outer periphery of a shaft 12 which is a rotating shaft of the cage rotor 11. The iron core 13 is formed by laminating electromagnetic steel sheets having a surface coated with an insulating film in the axial direction (the horizontal direction in FIG. 5). In the outer peripheral portion of the iron core 13, slots (grooves) 14 extending in the axial direction are formed at predetermined intervals in the circumferential direction and oblique to the axial direction. The oblique slots 14 are rotor conductors. Rotor bar (copper bar)
15 are fitted respectively. Both ends of the rotor bar 15 are connected to an end ring 16.

The reason why the oblique slots 14 are employed in the cage rotor 11 is to improve the abnormal torque at the time of starting and the electromagnetic noise due to slot harmonics.

However, since the rotor bar 15 is not insulated, the induced voltage difference between the rotor bars 15 causes
As shown by the arrow in FIG. 5, the cross current I (through the electromagnetic steel sheet) is passed through the iron core 13 between the rotor bars 15 circumferentially adjacent to each other.
Will flow. In particular, although not shown, if the above-described fixing portion is provided in the oblique slot 14, that is,
Similarly to FIG. 4, when the fixing portion in which the iron core 13 or the rotor bar 15 is closely adhered to the iron core 13 or the rotor bar 15 is provided at the same position in the axial direction, the cross current I becomes easy to flow. As a result, the cross flow loss increases, and the temperature of the cage rotor 11 increases.

Accordingly, an object of the present invention is to provide a squirrel-cage rotor capable of reducing cross flow loss in view of the above-mentioned prior art.

[0012]

A cage rotor according to the present invention, which solves the above-mentioned problems, comprises an iron core formed by laminating electromagnetic steel sheets in an axial direction in a state in which they are insulated from each other, and an outer peripheral portion of the iron core. A rotor bar fitted into the slot, and the iron core and the rotor bar are brought into close contact with one or more locations in the axial direction of the slot to firmly fix the rotor bar to the iron core In the cage rotor having the fixed portion described above, the fixed portion is arranged such that the fixed portions adjacent to each other in the circumferential direction among the fixed portions do not overlap each other in the axial direction.

Therefore, according to the cage rotor of the present invention, since the magnetic cores of the iron core are insulated from each other, the current hardly flows in the axial direction (the laminating direction). By preventing the adjacent fixing portions from overlapping each other in the axial direction, the cross flow becomes difficult to flow.

[0014]

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

FIG. 1 is a front view of a cage rotor of a cage induction motor according to an embodiment of the present invention. As shown in the figure, an iron core 23 is fixed to an outer periphery of a shaft 22 which is a rotating shaft of the cage rotor 21. This iron core 23
Is formed by laminating electromagnetic steel sheets having a surface coated with an insulating film in the axial direction (the horizontal direction in FIG. 1). A plurality of slots (grooves) 24 are formed in the outer peripheral portion of the iron core 23 in the axial direction and at predetermined intervals in the circumferential direction, and the slots 24 include a rotor bar (copper bar) 25 as a rotor conductor.
Are fitted respectively. Both ends of the rotor bar 25 are connected to an end ring 26.

At a plurality of positions in the axial direction of the slot 24, there are provided fixing portions 27 for firmly fixing the rotor bar 25 to the iron core 23 by bringing the iron core 23 into close contact with the rotor bar 25. In these fixing portions 27, similarly to FIG. 4, the iron core 23 or the rotor bar 25 is deformed so that the iron core 23 and the rotor bar 25 are brought into close contact with each other.

[0017] Then, the fixed portion 27, arranged as the fixed portion 27 adjacent to each other in the circumferential direction of the fixing portion 27 does not overlap each other in the axial direction with a constant interval L ₁ in the axial direction Have been.

Therefore, according to the cage rotor 21 according to the present embodiment, since the magnetic steel sheets forming the iron core 23 are insulated from each other, current flows in the axial direction (stacking direction). Since it is difficult to prevent the cross current from flowing, it is difficult for the fixing portions 27 adjacent in the circumferential direction to overlap each other in the axial direction.

Therefore, the cross flow loss can be significantly reduced. By reducing the cross current loss, the squirrel-cage induction motor including the squirrel-cage rotor 21 becomes a highly efficient squirrel-cage induction motor. Further, the temperature of the cage rotor 21 is lowered by reducing the cross flow loss. This is particularly effective for a safety-enhanced explosion-proof electric motor having a rotor temperature limitation.
In addition, by reducing the cross flow loss, the pull-up torque of the electric motor (the minimum torque in the starting torque characteristics of the electric motor)
Increase. If the cross flow loss is large, the torque decreases as shown by the dotted line in FIG.

That is, the cage rotor 2 according to the present embodiment
According to 1, the cross flow loss can be greatly reduced without affecting the fixing strength between the rotor bar 25 and the iron core 23, and a high-performance squirrel-cage induction motor can be obtained. This effect is particularly remarkable in a cage rotor having oblique slots in which a cross flow loss easily occurs.

[0021]

As described above in detail with the embodiments of the present invention, according to the squirrel-cage rotor of the present invention, since the magnetic steel sheets constituting the iron core are insulated from each other, the shaft Since it is difficult for the current to flow in the direction (stacking direction), by preventing the fixed portions adjacent in the circumferential direction from overlapping each other in the axial direction, it becomes difficult for the cross current to flow.

As a result, the cross current loss can be greatly reduced without affecting the fixing strength between the rotor bar and the iron core, and a high-performance squirrel cage electric machine can be obtained.

[Brief description of the drawings]

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

FIG. 2 is a graph showing torque characteristics of the squirrel-cage induction motor.

FIG. 3 is a front view of a cage rotor of a conventional cage induction motor.

FIG. 4 is an enlarged sectional view of a fixing portion provided in the cage rotor.

FIG. 5 is a front view of a cage rotor of a conventional cage induction motor having oblique slots.

[Explanation of symbols]

 21 Cage rotor 22 Shaft 23 Iron core 24 Slot 25 Rotor bar 26 End ring 27 Fixing part

Claims (1)

[Claims] An iron core formed by laminating electromagnetic steel sheets in an axial direction in a state in which they are insulated from each other, a rotor bar fitted in a slot formed in an outer peripheral portion of the iron core, and a shaft of the slot. In a cage rotor having a fixed portion in which the iron core and the rotor bar are brought into close contact with each other at one or more positions in the direction and the rotor bar is firmly fixed to the iron core, the fixed portion is fixed. A cage-shaped rotor in which fixed portions adjacent in the circumferential direction of the portions are arranged so as not to overlap with each other in the axial direction.