JP3453072B2 - Slot structure of cage induction motor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotor core element in which a plurality of slots are formed in the circumferential direction, the slots being formed by an upper conductor, a lower conductor, and a slit connecting the upper conductor and the lower conductor. The present invention relates to a slot structure of a squirrel cage induction motor in which a plurality of plates are stacked and an aluminum metal is injected into the slots in this state to integrally cast and form the stacked rotor core element plates.

[0002]

2. Description of the Related Art Conventionally, as a squirrel cage induction motor of this type, there is one shown in FIG.

FIG. 9 is a motor structure diagram showing the inside of a general squirrel cage induction motor M. As shown in FIG.

In this squirrel-cage induction motor M, a stationary stator iron core 2 and a stator coil 3 fixed to the stator frame 1 are arranged in a stator frame 1. Inside the stator core 2, a rotor core 4 that rotates integrally with the rotating shaft 5 is installed.

The rotor core 4 is formed by laminating a plurality of rotor core element plates 8 in the axial direction as shown in FIG. 10 in order to prevent loss due to eddy currents.

Reference numeral 10 shown in FIG. 10 is a plurality of slots formed in the rotor core element plate 8. The slot 10 is composed of an upper conductor 22, a lower conductor 24, and a slit 26 connecting the upper conductor and the lower conductor.

The slots (upper conductor 22, lower conductor 2)
4, by injecting an aluminum-based metal into the narrow gap 26) 10, the rotor core element plates 8 having the plurality of laminated layers are integrally cast-molded to form the rotor core 4, and the cage described in FIG. Form an induction motor.

In general, the rotor (rotating member such as the rotor core 4 and the rotating shaft 5) 20 of the squirrel-cage induction motor having an output of 200 KW or less is stamped from an electromagnetic steel plate having a thickness of about 0.5 mm. It is manufactured by stacking rotor core element plates 8 processed by a die and casting aluminum (not shown) in each slot 10 (through hole formed by continuous slots 10). Further, generally, for 5.5 KW or more, in order to improve the torque characteristics and reduce the starting current, the slot shape into which aluminum is cast is manufactured with a double cage structure.

FIG. 8 is a diagram showing the relationship between the speed and the torque of the cage conductor described in the standard electrical equipment course “Induction machine” published by Tokyo Denki University Press.

The squirrel cage induction motor is standardized by demanding optimum torque characteristics for various loads. In order to deal with this, as shown in the figure, the slot 10 of the rotor 20 is
It is common to change the shape of.

FIG. 8 shows that the speed / torque characteristics are variously changed by changing the selection of the cross-sectional areas of the upper conductor 22 and the lower conductor 24 and the ratio of the height D to the width W of the slit 26. (From the author of Tetsuichiro Nakajima et al., "Induction machine" of Tokyo Denki University Press). Note that FIG. 8 also includes slot shapes other than the double cage structure.

In the squirrel-cage induction motor, various slot shapes as illustrated in FIG. 8 are adopted according to the speed-torque characteristic (required characteristic) to be obtained in this way.

FIG. 7 shows a case where the stator coil 3 wound around the stator core 2 is under the same conditions and the cross-sectional area ratio of the upper conductor 22 and the lower conductor 24 is constant at a ratio of 1: 6, for example. 3 is a graph showing the values of the starting torque Ts, the maximum torque Tm, and the starting current Is with respect to the D (height) / W (width) ratio of the slit 26 (calculated value).

It can be seen that the maximum torque Tm increases as the width W of the slit 26 increases.

FIG. 6 shows an example of characteristics of speed, torque and current when the width W is large (D / W is small) and when the width W is small (D / W is large).

The curve (a) shown in FIG. 6 is obtained by increasing the slit width W of the slot 10, and the curve (b) is shown in the slot 1.
The slit width W of 0 is reduced.

As described above, by changing the slot shape of the rotor, various changes in torque characteristics can be obtained for various loads.

By the way, if a well-known aluminum casting rotor is made by using aluminum for a rotor conductor of a motor having a double squirrel cage structure (hereinafter referred to as a double squirrel cage motor), a gap between upper and lower grooves is formed. Aluminum also flows in and the upper and lower conductors are integrated. Therefore, the starting torque is reduced because the characteristics are closer to those of the deep groove squirrel-cage motor rather than the double squirrel-cage motor.

To avoid this problem, a structure as shown in FIG. 12 has been proposed.

In FIG. 12, a solid line (38) is used using an iron plate 36 in which the upper and lower grooves 30, 32 are connected by slanted slits 42.
As indicated by the dotted line (40), the iron plates 36 are alternately stacked for each stacking thickness to prevent the aluminum conductors in the slits 42 from being integrated in the axial direction. Since the intermediate slit is slanted, its effective length becomes long, so that the width of this slit 42 can be widened to improve the inflow of aluminum. As a result, the heat dissipation effect is increased, and at the same time, the height of the iron plate in the radial direction is reduced, and the amount of iron plate used is saved. In addition to this, the shaft of the electric motor can be thickened, and a mechanically strong electric motor can be obtained.

[0021]

However, it is necessary to change the slot shape (the cross-sectional area of the upper conductor 22, the cross-sectional area of the lower conductor 24, the width W of the slit 26, etc.) in accordance with such required characteristics. As the number of types of properties to be increased increases, so many types of core punching molds are required, which is uneconomical.

In addition, the change in the shape of the slot and the change in the characteristics do not always correspond to the calculated predictions, so that a good result is not always obtained by one time (it was often wasted). ).

On the other hand, if the so-called notching fabrication is carried out while reducing the die cost, the working time will be greatly increased, and in any case, the cost will be increased.

The present embodiment has been made in view of such a conventional problem, and reduces the types of punched iron cores (rotor iron core element plates) while achieving optimum motor torque characteristics suitable for various loads. It is an object of the present invention to provide a slot structure for a squirrel cage induction motor that can be easily obtained.

[0025]

According to a first aspect of the present invention, a plurality of slots are formed in the circumferential direction, each slot being composed of an upper conductor, a lower conductor and a slit connecting the upper conductor and the lower conductor. A plurality of laminated rotor core element plates, and in this state, aluminum-based metal is injected into the slots to integrally cast and form the plurality of laminated rotor core element plates. In the slot structure of, among the rotor core element plates stacked above,
At least a part of the rotor core element plates is such that the circumferential center of each slit in the slots formed in a plurality of rotor core element plates is the circumference of the upper conductor and the lower conductor in the same slot. The above-mentioned problem is solved by the structure formed by shifting from the center of the direction.

According to a second aspect of the present invention, an upper conductor, a lower conductor, and a slit connecting the upper conductor and the lower conductor,
A plurality of rotor core element plates each having a plurality of slots formed in the circumferential direction are laminated, and in this state, an aluminum-based metal is injected into the slots, so that the plurality of rotor core element plates are laminated. In the slot structure of the squirrel cage induction motor in which the element plates are integrally cast-molded, at least some of the rotor core element plates among the plurality of laminated rotor core element plates have a plurality of rotor core element plates. The circumferential center of each slit in the formed slot is formed by being displaced from the circumferential center of the upper conductor and the lower conductor in the same slot,
Further, the rotor core plates with the center offset are laminated in a predetermined laminated thickness in a state where the laminating directions are reversed, thereby solving the above problem.

By doing so, it becomes possible to easily manufacture a squirrel-cage induction motor having one (or an extremely small number of) coreless type and having arbitrary motor torque characteristics optimal for various loads.

In the structure shown in FIG. 12, the center of each slit in the slots formed in the rotor core element plate in the circumferential direction is the circle of the upper conductor and the lower conductor in the same slot. Since the structure is not displaced from the center in the circumferential direction, the original function of the present invention cannot be exhibited.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings.

This embodiment has the same basic structure as the squirrel-cage induction motor described with reference to FIG. 9, and therefore a duplicate description will be omitted.

As described in "Prior Art" in FIG. 10, a plurality of slots forming the rotor core element plate are formed in the circumferential direction X of the rotor core element plate, and the upper conductor and the lower part are formed. It is composed of a conductor and a slit connecting the upper conductor and the lower conductor.

Then, in the state where a plurality of rotor core element plates are laminated, aluminum-based metal is injected into the slots to integrally cast a plurality of laminated rotor core element plates.

This casting method is no different from the conventional squirrel cage induction motor. A major difference of the present embodiment from the conventional one is the structure of the slot.

An enlarged view of the conventional slot structure is shown in FIG. 11, and an enlarged view of the slot structure of the present embodiment is shown in FIG. 1 for comparative explanation.

It should be noted that the last two digits of the same or similar parts as in the prior art are given the same reference numerals in the drawings, and detailed description thereof will be omitted.

As shown in FIG. 11, the slot 1 is conventionally used.
The center P1 in the circumferential direction X of the slit 26 at 0 and the center P2 in the circumferential direction of the upper conductor 22 and the lower conductor 24 all coincided (P1 = P2).

In the state where the rotor core element plates 8 having such a slot shape are stacked (shown in FIG. 11).
FIG. 5 shows a cross section taken along the line VV of the arrow.

FIG. 5 conceptually shows the flow of the leakage magnetic flux in the lower conductor 24 in a state where aluminum is cast in the slot 10, in which a plurality of rotor core element plates 8 are arranged vertically in the plane of the drawing. They are stacked (the vertical direction corresponds to the axial direction of the rotor 20). With such a structure, when the squirrel cage induction motor is started, leakage magnetic flux as indicated by an arrow is generated. The flow of the leakage magnetic flux passes through the slit 26 of the slot 10 as shown in the figure. Here, the total amount of the leakage magnetic flux that passes through is φ3.

Next, the slot structure in this embodiment will be described with reference to FIG.

In this embodiment, the center (line) P1 in the circumferential direction of the rotor core of the conventional slit 26 is the slot 1
0 Center (line) that is exactly at the center of the conductors above and below itself
Unlike that formed on the P2, as shown in FIG. 1, the (all) rotor core element plates 108 have a plurality of slits 126 in the slots 100 formed in the rotor core element plates 108. The center P′1 in the circumferential direction X is set to the upper conductor 122 and the lower conductor 12 in the same slot 100.
4 is displaced from the center P′2 in the circumferential direction of P4 (P′1 ≠
P'2) is adopted (hereinafter, this is simply referred to as shifting the slit from the center).

In the embodiment shown in FIG. 1, the right end surface 126a of the slit 126 on the paper surface is the right end surface 122a of the upper conductor 122.
And the same end face as the right end face 124a of the lower conductor (the same straight line)
I am trying to become.

As described above, the slit 126 is formed in the slot 100.
Rotor core element plate 108 formed by shifting from the center of the
FIG. 2 shows a cross section taken along the line II-II in the case where the layers are stacked while reversing the stacking direction at regular intervals L.

The arrow in FIG. 2B represents the leakage magnetic flux flowing through (the slit 126 of the slot). This FIG. 2 (B) corresponds to a leakage magnetic flux which is substantially the same as that explained in FIG. 5 of the related art.

That is, when the squirrel-cage induction motor shown in FIG. 5 is operated under the same conditions, the same amount of leakage flux φ3 flows.

On the other hand, in this embodiment, as described above, the slit 126 is displaced from the center, and the rotor core element plates 108 are reversed in the direction of their laminated thickness at regular intervals L. Slot slot 1 as shown in FIG.
There is a leakage magnetic flux φ3 ′ that does not pass (avoid) 26.

That is, in this embodiment, the rotor core element plates 108 have the same center P'1 in the circumferential direction X of the slits 126 in the slots 100 formed in the rotor core element plates 108. Upper conductor 122 in slot
And the lower conductor 124 is formed by being displaced from the center P′2 of the lower conductor 124 in the circumferential direction X, and the rotor core element plates 108, which are displaced from the center, are laminated in a state of being inverted by a predetermined stack thickness L. As a result, the leakage magnetic flux of the lower conductor is the sum of φ3 that crosses the slot slit W and φ3 ′ that bypasses the cut portion of the slit 126 through the core lamination direction (φ3 + φ).
3 '). That is, the leakage magnetic flux is increased by φ3 ′ as compared with φ3 in the conventional slot structure.

The increase in the leakage magnetic flux means that the same effect as that obtained by reducing the slit width W can be obtained. That is, (φ3 + φ3 ′) ∝1 / (W−ΔW).

For example, if the inverted product thickness L of the rotor core element plate 108 is reduced, φ3 'increases, so φ
3 '/ φ3 will increase. Therefore, as a result, it is synonymous with reducing the slit width W.

In this case, by reversing the lamination direction of the rotor core element plates 108 at a certain interval L, the aluminum conductor portion existing in the slit 126 is cut off, so that no current flows. The effect of the heavy cage structure can be obtained even more effectively.

Further, by changing the interval L of the reverse lamination, it becomes possible to easily manufacture a squirrel-cage induction motor having different torque characteristics by using one type of iron core die, which greatly shortens the manufacturing time and significantly. Cost reduction.

The rotor core element plates (electromagnetic steel plates) generally used in the squirrel cage induction motor have concrete numerical values on both sides of a plate thickness of 0.5 mm (which may be 0.65 mm in USA). An electric insulating coating of about 0.5 to 1 μm is coated, and when these are laminated, some voids exist in the laminating direction. The ratio of the voids to the rotor core element plate 108 is 2 to 3%.

The slit 126 is not limited to the shape shown in FIG. 1, but may be the shape shown in FIGS. 3 (A) and 3 (B).

3A and 3B, the centers P ″ 1 and P ″ ″ 1 in the circumferential direction X of the slits 226 and 326 in the slots 200 and 300 respectively correspond to the same slot 20.
Centers P ″ 2, P ″ in the circumferential direction X of the upper conductors 222, 322 and the lower conductors 224, 324 at 0, 300.
It is formed by shifting from '2.

As is clear from the figure, the slit 226,
The center P ″ 1 of the circumferential direction X of 326 is set to the upper and lower conductors 222,
The ends 322, 324, and 324 are formed so as to be shifted further to the right side (outside the slot) of the drawing than the end faces (broken line).

By doing so, it is possible to further increase the difference in characteristics obtained when the stacking directions are reversed.

As described above, the present invention is not particularly limited to the form shown in FIG. 1 and may have various forms. Two or more of these different shapes may be mixed in one rotor.

Further, in the present invention, it is not necessary that all the rotor core element plates have the slots having the "center deviation" as described above, but the slots have the same centers as in the conventional case. The rotor core element plate may be partially mixed and left. For example, as shown in FIG. 4 (A), a conventional rotor core element plate 108A whose centers coincide with each other.
The rotor core element plates 108B that do not correspond to the above may be alternately laminated in sequence (while the 108B is appropriately inverted). Further, as shown in FIG. 4B, the rotor core element plates 108 are not arranged at regular intervals, but for example, the laminated thicknesses L1 and L2.
May be changed. The laminated thickness is not limited to L1 and L2, but the laminated thickness may be L3 and L as shown in FIG.
There may be several types such as 4, L5, L6, L7 ... By doing so, it becomes possible to set the torque with a higher degree of freedom.

Further, as shown in FIG. 4 (C), it may be reversed at irregular intervals. As shown in FIG. 4 (D), a plurality of rotor core element plates having a slit 126 offset from the center are used. (Three types of distances from the center to the slit in the figure are H1, H2, and H3: 108C, 108D, and 108E) may be prepared and laminated while being compounded and inverted. Of course, (D)
In the case of also, the rotor core element plate having the slots where the centers of the slits coincide with each other may be partially mixed and left.

[0059]

As described above, according to the present invention, a variety of squirrel cage induction motors having different torque characteristics can be easily manufactured by one type (or only a few types) of the core removal type die. Further, the excellent effect that the effect of the double squirrel cage structure can be more effectively exhibited can be obtained.

[Brief description of drawings]

FIG. 1 is a front view showing a main part of a slot of a rotor core element plate according to the present embodiment.

FIG. 2 is a sectional view taken along the line II-II in FIG. 1 when a plurality of rotor core element plates in FIG. 1 are stacked.

FIG. 3 is a front view showing a main part of a slot of a rotor core element plate of another embodiment.

4 is a cross-sectional view corresponding to FIG. 2 when a plurality of rotor core element plates according to another embodiment are stacked.

5 is a cross-sectional view taken along the line VV in the arrow when a plurality of rotor core element plates in FIG. 11 are stacked.

FIG. 6 is a graph showing starting torque, maximum torque, and starting current when the width of the slit is changed.

FIG. 7 is a graph showing the values of the starting torque Ts, the maximum torque Tm, and the starting current Is with respect to the (height) / (width) ratio of the slit.

FIG. 8 is a graph showing the speed / torque characteristics with respect to the cross-sectional area of the upper conductor and the lower conductor and the ratio of the height to the width of the slit.

FIG. 9 is a structural diagram of a conventional squirrel-cage motor

FIG. 10 is a front view showing the entire conventional rotor core element plate.

FIG. 11 is an enlarged front view of a slot of a conventional rotor core element plate.

FIG. 12 is a front view showing another conventional example of the slots of the rotor core element plate.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Stator frame 2 ... Stationary stator core 3 ... Stator coil 4 ... Rotor core 6 ... Rotor bar 8 ... Rotor core element plate 10, 100 ... Slot 12 ... End rings 22, 122 ... Upper conductor 24, 124 ... Lower conductors 26, 126 ... Gap Ts ... Starting torque Tm ... Maximum torque Tm ... Starting current D ... Gap height W ... Gap width X ... Circumferential direction P'1 ... Gap in slot Center P′2 in the circumferential direction of the above ... Centers L, L1, L2 in the circumferential direction of the upper conductor and the lower conductor in the slot ... Stacked thickness

Claims (2)

(57) [Claims] 1. A plurality of rotor core element plates, each having a plurality of slots formed in the circumferential direction, each slot being composed of an upper conductor, a lower conductor, and a slit connecting the upper conductor and the lower conductor. In this state, in the slot structure of the squirrel-cage induction motor in which the aluminum-based metal is injected into the slot to integrally cast and form the rotor core element plates having the plurality of laminated layers, At least a part of the rotor core element plates among the slave core element plates is such that the circumferential center of each slit in the plurality of slots formed in the rotor core element plate is the upper part in the same slot. A slot structure for a squirrel-cage induction motor, characterized in that the conductor and the lower conductor are formed so as to be displaced from the circumferential center. 2. A plurality of rotor core element plates each having a plurality of slots formed in the circumferential direction, the slots being formed by an upper conductor, a lower conductor, and a slit connecting the upper conductor and the lower conductor. In this state, in the slot structure of the squirrel-cage induction motor in which the aluminum-based metal is injected into the slot to integrally cast and form the rotor core element plates having the plurality of laminated layers, At least a part of the rotor core element plates among the slave core element plates is such that the circumferential center of each slit in the plurality of slots formed in the rotor core element plate is the upper part in the same slot. The rotor core plate is formed by displacing from the center of the conductor and the lower conductor in the circumferential direction, and the rotor core plates with the centers offset Slot structure of squirrel-cage induction motor, characterized in that the layers.