JPH01129738A - Motor or squirrel-cage induction motor - Google Patents

Abstract

PURPOSE:To improve operation efficiency, by arranging outer slots alternately which are composed of two kinds, large and small slots, and by arranging inner slots in radius direction of the small outer slots. CONSTITUTION:Outer slots are large slots A' and small slots A''. Inner slots are slots B' extending radially to the small outer slots A''. The large outer slots A' and small slots A'' are alternately arranged concentrically close to the circumference of a rotor. The inner slots B' are arranged so as to extendingly situated internally in the radius direction and to connect to the small outer slots A''. Furthermore, the inner slots B' is projected circumferentially at the intermediate section between the end and the connected section to the small outer slots A'', causing the adjacent inner slots B' to approach mutually as much as possible. Thus, the width can be made maximum as much as possible and the cross section increases remarkably.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to the structure of the rotor of a squirrel cage induction motor, and more specifically to increasing the cross-sectional area of the inner slot of the rotor of a double squirrel cage induction motor. This relates to improvements to the structure to achieve this goal.

[Prior Art] In squirrel cage induction motors, an aluminum die-cast lobe as shown in Fig. 1 is generally used, but in order to improve efficiency by reducing the starting current and increasing the starting torque. A double squirrel cage rotor with a rotor slot shape as shown in Figure 4 was used. In such a double squirrel cage induction motor, the rotor slot Ao
When conductor bars A and B are inserted into these as two stages inside and outside of and Bo, and their respective ends are short-circuited with an end ring (not shown), the leakage magnetic flux of inner conductor B increases,
At the time of starting when the secondary slip frequency is high, the current distribution is determined by the actance component, and most of the current flows through the high resistance conductor A, so the starting characteristics are improved. On the other hand, when driving,
Since the secondary slip frequency is small, a large amount of current flows through the inner conductor B, which has a low resistance, so that the secondary copper loss can be suppressed to a relatively modest value.

[Problems to be Solved by the Invention] In order to improve the efficiency of the induction motor in a steady operating state, it is necessary to increase the cross-sectional area of the inner conductor B. However, in FIG. 4 showing the rotor of a conventional double squirrel cage induction motor, let Ao be the outer slot, Bo be the inner slot, and let the spacing between the outer slots be a and the spacing between the inner slots be b. If the spacings a and b between the slots are reduced, the magnetic flux density will be increased, but these dimensions can be roughly determined depending on the diameter of the rotor and the number of rotors.

On the other hand, if the cross-sectional area of the inner slot B can be increased, the copper loss will be reduced and the operating efficiency will be improved, but as is clear from Fig. 4, when considering the two adjacent slots B1 and B2, slot B+ is In sector OLM, slot B2 is in sector 0MN;
There is a common radius OM between them, and even if we try to increase the cross-sectional area of both slots B and B2 by making them as close to this radius OM as practically possible, B and B2 will become too close. As a result, the bo through which the magnetic flux passes becomes smaller and the magnetic flux density becomes larger, so the no-load becomes large, and there is a limit to the deterioration of the motor characteristics, which is inconvenient, so the extent to which the cross-sectional area can be increased is not very large. do not have.

From this point of view, it was considered impossible to significantly increase the cross-sectional area of the inner conductor B.

[Means for Solving the Problems] In the present invention, the starting characteristics determined by the magnetic flux density between the secondary slots and the outer conductor are the same as or slightly higher than the current state, and the cross-sectional area of the inner conductor B is By significantly increasing the size, the operating efficiency was improved and the problem was solved.

As a concrete solution, as shown in Fig. 2, there are two types of outer slots, large Ao and small A'', and one type of inner slot is B', which extends in the radial direction continuously from the small outer slot A''. chisel and large outer slot A°
and small slots A'' are arranged concentrically and alternately near the outer circumferential edge of the rotor, and the inner slots are interleaved with the smaller outer slots A.
and furthermore, this inner slot B° is arranged so as to extend continuously and radially inwardly thereto, and in the intermediate part between its radially inner end and the smaller outer slot A" which connection,
Adjacent circumferentially protruding inner slots are brought as close together as possible to maximize their width and greatly increase their cross-sectional area.

Since there are two types of outer slots, large Ao and small A", and they are arranged alternately, the total number of outer slots is the same, but
The spacing between the larger slots A° is greatly increased, and the number of inner slots B°, which are arranged as extensions of the smaller slots A” arranged between them, is halved;
The scope for increasing the circumferential width can be significantly increased, allowing the total cross-sectional area of the entire inner slot to be significantly increased.

[Example] Fig. 3 is a schematic diagram showing the shape, arrangement, and dimensions of a new slot of a rotor in which the total cross-sectional area of the inner slot has been significantly increased according to the present invention, and Fig. 5 is a schematic diagram showing a conventional slot for comparison. FIG.

In Figures 3 and 5, the rotor has a diameter of 206 mm, and the total number of large slots A'' and small slots A'' is 56.
° and the small slot A” each have a diameter of 7rII
At the radially inner end of the small slot A" at m and 4raI11, an inner slot B° is formed which continuously extends further radially inwardly, and this slot B° is formed at the radially inner end of the small outer slot A". From the end, the width increases in the radial and circumferential directions to a maximum width of IO, 7 mm, and then decreases in the radial and circumferential directions, terminating in an arc of 2.65 mm. These terminal ends have a radius of 13 mm from the axis.
It lies on a circumference of 0 mm, and the distance from each end to the maximum width position of the slot is 27 m+a.

For comparison, in the conventional rotor shown in FIG. 14.3 radially inward from the position of
+n+a has a width of 3.2mm and a length of 14.3m.
It has an n+ rectangular cross section, and the outer slot A and the inner slot B are connected by a narrow communication groove C with a width of 1.2 mm.

The distance between the large slot A° and the small slot A'' formed in this way and constituting the outer slot of the present invention is ao, and the inner slot B.

If the distance between the outer slots A and the inner slot B according to the conventional technology to be compared is set as a, and the distance between the inner slots B is set as b, the table below shows the comparison. .

Slot code on uninhabited unit a b a'b' dimension m
n+ 5.39 4.93 5.62 4.94
From this result, a and a', b and bo each have extremely close values.

Next, from the dimensions shown in FIGS. 3 and 5, the cross-sectional areas of the outer slot and the inner slot of the conventional slot and the slot of the present invention are compared as follows.

Cross-sectional area of the upper outer slot of the outer slot (code A) (code A'+A'') 1479 1429 1479 1429 1479 1429 1479

Cross-sectional area of inner slot (code B) (code B') m
m” 2563 5726 total mm24
042 7155 From this result, the total cross-sectional area of the slots of the present invention is 7155a+m'', which is 77% greater than the total cross-sectional area of the conventional slots, which is 4042+am''. Therefore, secondary copper loss can be reduced by 77%.

[Effect] According to the slot structure of the present invention, there are two types of outer slots, Ao and A'', which are arranged alternately, and the inner slot is arranged radially inward of the smaller slot. Simple configuration reduces the number of internal slots by half
However, the total cross-sectional area increases by 77%, and secondary copper loss can be reduced by 77%, which greatly contributes to improving efficiency during operation of the induction motor.

[Brief explanation of the drawing]

FIG. 1 is a schematic side view and front view of a solid rotor, FIG. 2 is a schematic side view showing the shape and arrangement of the rotor slots according to the present invention, and FIG. 3 is a diagram showing the shape and dimensions of the rotor slots according to the present invention. FIG. 4 is a schematic side view showing the shape and arrangement of a conventional rotor slot, and FIG. 5 is a schematic side view showing the shape and dimensions of a conventional rotor slot. Symbols in the drawing Ao: Larger outer slot, A": Smaller outer slot, Bo: Inner slot, a: Distance between outer slots A° and A", 2b = Between adjacent inner slots B° interval. Agent Patent attorney Takeo Goto Agent Patent attorney Haruya Sai Fuji Agent Patent attorney Fujimoto Hirakaki 3 Figure A' Two larger outer slots A'': Smaller outer slots B': Inner slots a: Outside Distance 2b between slots A and 8: Distance between adjacent inner slots B' Fig. 1

Claims (1)

[Claims] In the rotor of a squirrel-cage induction motor: The slot portions are of two types, large and small, arranged concentrically and alternately and at regular intervals parallel to the rotation axis along the outer periphery of the rotor. an equal number of outer slot groups; a group of inner slots extending radially inwardly, continuous with the radially inner end of the smaller slots in said outer slot group, each inner slot at a radially intermediate portion thereof; A rotor for a squirrel-cage induction motor, characterized in that the rotor is comprised of an inner slot group whose cross-sectional area is increased by expanding in the circumferential direction.