JPH03285543A - Squirrel-cage rotor - Google Patents

Abstract

PURPOSE:To suppress abnormal torque, vibration, noise or the like due to higher harmonic flux by asymmetrically forming the punched part of steel plates so that the bridge part or the opening at the outer circumferential side is positioned while being shifted by a predetermined distance to one side from the center line of a main section in which a conductor is contained. CONSTITUTION:A plurality of steel plates 3 having punched parts 2 are laminated to form a unit block 4 of a laminated core 1. A slot 5 is formed by the punched part 2 of the steel board 3 so that a bridge part or an opening 5b is formed at a position shifted by a predetermined distance (d) from the center line l of a main part 5a. Rotor diameter D, corresponding number Z of slot in the stator and the number of pole pair (p) satisfy a relation piD/4(Z+p)<=d<=D /4(Z-p). Shifting direction is reversed for every unit block 4a, 4b.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a cage-shaped core having a laminated iron core formed by laminating steel plates each having a plurality of slot forming portions for accommodating conductors formed on the outer periphery thereof. Regarding the rotor.

(Prior art) In general, this type of squirrel cage rotor has a laminated iron core formed by laminating a large number of magnetic steel plates with a plurality of slots formed in advance by punching, etc. on the outer periphery. A squirrel-cage conductor is formed by forming a secondary conductor of aluminum or the like in the slot of the iron core using a casting method, and connecting the ends of the secondary conductor with end rings.

In this case, when the rotor is driven, the magnetic flux that enters the laminated core from the stator through the gap contains harmonic components, and the harmonic components of this magnetic flux cause the secondary conductor to This will generate harmonic electromotive force. However, such harmonic electromotive force acts as abnormal torque on the rotor, resulting in pulsating torque and causing vibration or noise.

Therefore, in order to suppress the adverse effects of such harmonic components, a laminated iron core in which the rotor is so-called skewed has been conventionally used. This is a technique in which the positions of the rotor slots are slightly shifted in the circumferential direction when the steel plates are laminated; for example, there is one in which the positions of the rotor slots are shifted by one pitch of the stator slots as a whole. By doing this, the phase of the electromotive force generated in the secondary conductor is slightly shifted due to the harmonic component of the magnetic flux, so the harmonic component of the electromotive force as a whole is canceled out, and the amount that contributes to abnormal torque is suppressed. It is something that will be done.

Also, the arrangement of slots formed in the stator and rotor,
Depending on the shape, abnormal torque called position torque may occur depending on the relative position of both at the time of starting. In other words, if the amount of skew is less than one pitch of the stator slot, including the above case, the rotor and stator face each other unevenly, so it will be fixed at startup depending on the position. This results in a difference in the magnitude of the torque received from the child. Therefore, in order to suppress such position torque, there are rotors in which the above-mentioned skew amount is further increased to have a skew amount exceeding one pitch of the stator slot. That is, by increasing the skinny amount, the state of facing the stator is prevented from becoming uneven depending on the stop position of the rotor, and the position torque is suppressed.

(Problems to be Solved by the Invention) However, the conventional configuration as described above had the following problems.

That is, when a secondary conductor is housed in a laminated core having skewed slots, it is necessary to form the secondary conductor by casting a metal such as aluminum.

In this case, since the amount of skew is larger than one pitch of the stator slot, a large step may occur in the laminated portion of the steel plate within the slot, and defects such as cavities may occur in the step. occurs. Such defective portions cause the rotor to become unbalanced, resulting in a problem of lowering the stability of the rotational state, especially when rotating at high speeds.

Further, as described above, due to the large amount of skew, the slot cross section of the rotor is not effectively utilized, resulting in problems such as a rise in temperature or deterioration of characteristics.

On the other hand, in order to avoid the problems caused by mechanically skewing as described above, methods have been proposed in which only the skew effect is obtained without performing skew when laminating steel plates. For example, in the method shown in Japanese Utility Model Publication No. 52-17045, the opening or bridge portion of the slot is formed offset from the center line of the slot, and steel plates are laminated without skewing the main part of the slot. The laminated iron core is constructed using the following methods. As a result, the skew effect of suppressing the adverse effects of harmonic magnetic flux can be obtained, but in this case, since no mechanical skew is performed, the above-mentioned problem caused by the generation of position torque cannot be solved. there were.

The present invention has been made in view of the above circumstances, and its purpose is to suppress abnormal torque, vibration, noise, etc. due to harmonic magnetic flux without increasing the amount of mechanical skew, and to reduce position torque at the time of starting. To provide a squirrel cage rotor that can also suppress

[Structure of the Invention (Means for Solving the Problems) The present invention comprises laminating a predetermined number of steel plates each having a punched part for forming a slot for accommodating a conductor in the outer periphery to form a laminated iron core. The target is a squirrel cage rotor, and the punched portion of the steel plate is such that the bridge portion or opening on the outer circumference side thereof satisfies the following conditions on one side with respect to the center line of the main portion in which the conductor is housed. The laminated iron core is formed into an asymmetrical shape with positions shifted by a distance d, and the laminated iron core is formed by combining a plurality of unit blocks in which a plurality of laminated steel plates are aligned with each other in the direction of the slots, and between each unit block. is characterized in that the slots have different directions and the main portions overlap, and that at least one of the plurality of sets of laminated cores is skewed by a predetermined amount.

However, D = rotor diameter 2: number of slots in the corresponding stator p: number of pole pairs (function) According to the squirrel cage rotor of the present invention, as shown in FIG. A unit block 4 is formed by laminating a plurality of steel plates 3 having a
FIG. 11 shows the case of two unit blocks 4A and 4B). In this case, the slot 5 formed by the punched part 2 of the steel plate 3 is a bridge part or an opening 5b (the slot 5 is shown as a closed type in the figure, and the outer peripheral side is the bridge part 5b) with respect to the main part 5a. ) is formed at a position shifted by a predetermined amount Md from the center 1iIg of the main portion 5a, and the unit block 4
They are arranged so that the direction of shift is opposite for each of A and 4B. Also, each unit block 46.4. In this case, the steel plates 3 are stacked so that the main portion 5a of the slot 5 is skewed by a predetermined amount, and the laminated core 1 as a whole is formed to be skewed by a distance Mg. Therefore, in terms of the outer shape, the main portion 5a of the slot 5 is generally skewed by a distance g with respect to the axis of the rotating shaft.

With this configuration, the electrical characteristics are as follows:
According to the principle described below, a larger skew effect than that obtained by skewing by a distance Mg can be obtained, and it is possible to suppress abnormal torque generation, vibration, and noise associated with rotor drive as much as possible, and also suppress position torque. In other words, the skew effect (
In addition to the mechanical skew effect (hereinafter referred to as a mechanical skew effect), there is a skew effect due to the shape of the slot 5 (hereinafter referred to as a pseudo-skew effect), resulting in a large skew effect.

To explain the above principle, first, using Fig. 2, (1)
Find the pseudo skew coefficient Ksn', then use FIG. 3 to find (II) the mechanical skew coefficient Ksn,
Finally, the skew coefficient Ksn of the present invention (III), which is a combination of both, is determined and its skew effect will be explained.

(1) Pseudo skew coefficient Ksn' FIG. 2 is a diagram showing the laminated core 1' in a state where the laminated core 1 in FIG. 1 is not mechanically skewed (skew ff1g). That is, it consists of unit blocks 4A and 4B formed by laminating similar steel plates 3.

That is, in this case, as shown in FIG. 4, the magnetic fluxes Φ6 and Φ8 that enter the unit blocks 4^ and 4u from the stator side through the gap have different inflow paths and have a phase difference α(@
, air angle) occurs. Secondary conductor 6 due to magnetic flux Φ^ and ΦB
If the voltages induced in are respectively eA and e8, a phase difference α similarly occurs. This phase difference α is caused by the distance 111f2d, which corresponds to the difference between the magnetic paths of the magnetic fluxes Φ6 and Φ8. Specifically, it is calculated by the following equation using the number of pole pairs p and the pole pitch τ expressed by the outer diameter of the laminated iron core 1. It is given as follows.

p On the other hand, the induced voltages eA and e are each expressed as vector quantities as shown in Fig. 5, and the voltage e actually generated in the rotor conductor 6 is expressed as the sum of these e-eA + eB. is the value given.

The magnetic fluxes Φ6 and Φ8 contain harmonic components, and thereby the induced voltages eA and e9 also have harmonic components. However, since there is a phase difference α between the two, the degree of the harmonic component included in the induced voltage e, which is the combined value of these, becomes a different value depending on each order.

A pseudo skew coefficient K s n ′ indicating the degree of harmonic components included in such an induced voltage e is given by the following equation.

Also, in the n-th harmonic, the phase angle α becomes n times, so if α is replaced by nα, the pseudo skew coefficient Ksn' expressed by equation (2) can be expressed as the following equation. Ru.

Now, if the thicknesses of unit blocks 4A and 4B are the same, leA l-1ee I, and as shown by the vector in the conceptual diagram in Figure 5, the value of the denominator of equation (2) is the line segment O.
It is equal to twice the length of A, 2r.

Further, the size of the sum of vectors in molecules of the same size is equal to the length q of the line segment OB in the figure. When these values are expressed in accordance with equation (2), they are calculated as follows.

(II) Mechanical skew coefficient Ksn'' FIG. 3 shows that the steel plate 3 of the laminated core 1 in FIG. This is a diagram showing a laminated iron core 1' formed by performing the skew amount g). (Therefore, a unit block cannot be formed.) In this case, since it is mechanically skewed, the The phase of the magnetic flux differs depending on the position.Here, if the phase difference at both ends is θ (electrical angle), the skew mg can be expressed as follows.

gπ θ = □ τ (5) The skew coefficient Ks' expressed in (6) is as follows.

p In addition, in this case, the induced voltage e generated in the secondary conductor 6 is considered in the vector diagram shown in FIG. 6 in the same manner as described above.
It is expressed by the length of the chord OC which is a composite of vectors whose directions are sequentially bent like an arc S due to mechanical skew, so if the length of the arc OC is S5 and the length of the chord OC is t, then
The skew coefficient KS is expressed as follows.

(III) Skew coefficient Ksn of the present invention Next, to explain the case of the present invention, since the skew coefficient of 6 is a combination of the above two cases, it can be expressed based on the vectors in FIGS. 5 and 6. , as shown in the following equation.

s R' θ Also, in the n-th harmonic, the phase angle θ becomes n times, so if we replace θ with nθ, we end up with 1 equation.Since we are considering the same laminated core 1, the line segment OB Since it is known that the lengths q and S of the arc OC and the length q of the arc OC are equal, the following relationship holds true.

θ Therefore, by substituting this equation (9) into equation (8), we get, and from this result, when compared with equation (3) and equation (6),
The skew coefficient Ks in the present invention can be expressed as follows.

Ks-Ks'·Ks'-(11) In other words, it is expressed as the product of the respective skinny coefficients.

Furthermore, in the 0th harmonic, the phase angles α and θ are each multiplied by n, so by substituting it into equation (10) and comparing it with equations (4) and (7), the following equation is obtained.

Now, it is generally well known that harmonics that tend to generate abnormal torque, vibration, or noise are caused by groove harmonics caused by stator slots, but the order μs of the harmonics is It is expressed as

μ, = − soil 1 (13) (However, 2 is the number of stator slots) Therefore, the value of the skew coefficient Ksn in the case of the present invention at the order shown in the above formula (13) is given by the formula ( 12) is calculated as follows. That is, first, with respect to the range (A) of the set distance 11XId, the range of the phase difference α is calculated from equation (1) as follows:
14) z+p z+p Based on this result, first find the case of the first order (n - 1) of the skew coefficients Ksn shown in equation (12). (a) Lower limit of α, 8, p - 2 ), the values of equations (15a) and (15b) are eO
The value of s becomes approximately 1, and the value of the remaining part is also generally θ
Since the value of is small, it becomes approximately 1, so it can be regarded as approximately 1 as a whole.

On the other hand, the skew coefficient Ksn due to the μS-order harmonic shown in equation (13) is expressed by the following equation corresponding to each of the upper and lower limits of the distance d.

(b) The upper limit of α, where the values are in any order. Among the values in equation (16), the value of eOs is, as mentioned above, generally the number of slots in the stator, 2, is larger than the number of pole pairs, p. By doing so, it can be approximated as follows.

Here, in the general case, since the number of stator slots 2 is larger than the number of pole pairs p (for example, z-4, the formula (
16) can be approximated as shown in the following equation.

When the phase differences α and θ are substituted into equation (12) using equations (1) and (5) and the skinny coefficient Ksn is determined, the following equation is obtained.

As a result, the μ8th order skinny coefficient Ksn, which adversely affects the rotor, shown in equation (13) can be made approximately zero regardless of the chain of phase difference θ corresponding to the size of the mechanical skew. be. Therefore, in any case, the skew coefficient can be set to approximately 1 for the first-order component of the voltage induced in the conductor, which effectively acts as the rotational force of the rotor, and abnormal torque, vibration, or The induced voltage of the harmonic component of order μ5, which causes noise, can be reduced as much as possible, and a large skinny effect can be obtained.

Now, the position torque generated based on the relative positional relationship between the stator and rotor at the time of starting will be explained.

First, the mechanical skew mg in the present invention and here,
Regarding the laminated core 1' described above, as shown from the outer circumferential side in FIG. The skew Ig for obtaining substantially the same skew effect is expressed as shown in FIG.

g = b -2d (20) In other words, compared to the case of only mechanical skew, the amount of skew is only 2d smaller. Now, Figure 7(a)
Considering the case where the mechanical skew ah shown in is required for one pitch or more of the stator slot, for example, if the value of d is d - (πD) / (42), the skew Qg in the case of the present invention is calculated by the following formula. It can be obtained as a condition like . That is, the skew coefficient Ksn derived in this way
FIG. 8 shows the results of calculations according to various conditions.

In this case, the coefficient Ksn when performing conventional skew
The values of Ksn' and
) and formula (7).

As can be seen from this result, when conventional skewing is performed, the value of distance d becomes a large value of 0.6 or more even in the range of formula (A), whereas As shown, in the case of pseudo-skew, the value is 0.1 or less or in the vicinity thereof, and in the present invention, this value is further reduced to about 0.6 times, and a sufficiently large skew effect is obtained. I understand.

(Example) Hereinafter, an example in which the present invention is applied to a motor will be described with reference to FIGS. 9 to 312.

First, in FIG. 11 showing the overall configuration in cross section, the stator 11 consists of a stator core 12 and a stator winding 13 housed in a slot (not shown). It is formed by stacking stamped steel plates 4 without skewing.

The squirrel cage rotor 15 consists of a rotating shaft 16 supported by a bearing (not shown) and a laminated core 17 fitted into the rotating shaft 16. The laminated core 17 has a number of slots 18 formed along its outer periphery. ing.

A secondary isometric body 19 of an aluminum cap is housed in the slot 18 of the laminated core 17 by casting, and an end ring 20 is provided at the end thereof to form a squirrel cage conductor 21 .

Next, the squirrel cage rotor 15 will be described in detail.

The steel plate 22 constituting the laminated core 17 is a disc-shaped one made of silicon steel plate, cold-rolled steel plate, etc. and has an outer diameter of D, and has a predetermined interval on the outer periphery as shown in FIG. A large number of punched portions 23 for forming the slots 18 are formed.

The punched portion 23 has a main portion 23g on the inner peripheral side and a bridge portion 23b for generating a skew effect arranged in the following relationship. That is, the position of the bridge portion 23b is a predetermined distance +! from the center line g of the main portion 23a. They are arranged so as to be shifted to one side by ld. And distance M
d is a value that satisfies the condition shown in the above-mentioned formula (A),
It is set as follows.

A predetermined number of such steel plates 22 are laminated so that the positions of the punched parts 23 are slightly shifted in the circumferential direction, and a total thickness of L is 17 mm.
A unit block 24 having a thickness of 2 is formed, and the skew m at both ends thereof is set to be g/2. This unit block 24 and the punching part 2 formed as the same sphere.
The unit block 25 in which 3 is placed upside down is inserted into the punching section 2.
The main parts 23a of the three main parts 23a are combined so as to overlap to form the laminated core 17 (see FIG. 9). Therefore, when the slots 18 of the laminated core 17 are viewed in the axial direction of the rotating shaft 16, as shown in FIG. This results in a positional relationship that is skewed by a distance g as a whole.

According to this embodiment configured in this way, the following skew effect can be obtained in the rotating state.

That is, since the distance d described above is set as shown in equation (a), the value of the phase difference α corresponding to equation (13) is πp (b). Therefore, the skew coefficient Ksn is expressed by the formula (15a)
, (15b) and equation (15), the following values are obtained.

(a) For 1st order (n-1) (b) For 88th order Cμs-(z/p)±1] Now, for example, let us assume that the number of slots 2 in the stator is 36, and the number of pole pairs p is 2. If the skinny amount g is calculated as one pitch of the stator slot (g-πD/z), it will be as shown in FIG. 12. As a result, the value of the skinny coefficient Ksn in equation (c) is 0. Since it is 995, consider it to be approximately 1,
Also, the value of the skew coefficient Ksn in equation (d) is 17
Next, the 19th order is 0.058 and 0.052, respectively, so it can be considered as approximately zero.

From this result, when comparing the mechanical skew coefficient Ksn' and the pseudo skew coefficient Ksn in the case of the conventional skew and the skew coefficient Ksn in this example, it is found that the 17th order 61
Looking at the ninth-order groove harmonic, the skew coefficient K s n of this example is reduced to about 926 compared to the mechanical skew coefficient K s n , and the pseudo skinny coefficient K
It can be seen that sn' is also reduced to about 60%. Therefore, since the harmonic torque is reduced, the generation of abnormal torque is suppressed as much as possible, and the generation of vibration and noise is also reduced.

Further, the position torque generated depending on the relative positional relationship of each slot between the stator 11 and the rotor 15 at the time of startup is also reduced to a greater extent than in the case of only mechanical skew. In other words, the skew ah, which essentially acts as a skinny effect in this example, is calculated by the above equation (
By substituting equation (a) and the value of g based on 20), we get the following.

2 As a result, the skew amount is actually 1.5 times the mechanical skew amount g and the skew effect is obtained, and the position torque can be suppressed to a greater extent.
Moreover, even in this case, it is possible to prevent a decrease in rotational characteristics and an abnormal temperature rise without reducing the effective cross-sectional area of the slots 18 of the rotor 15.

FIGS. 13(a), (b) and (C) show modifications of the above embodiment, in which the unit blocks 24 and 25 are
Instead, it is constructed by changing their mechanical skew.

That is, in the same figure (a), unit blocks 26 and 2
7, only one unit block 26 is mechanically skewed to form a laminated core 28. Same figure (b)
In this example, a laminated core 31 is constructed by reversing the mechanical skew directions of unit blocks 29 and 30. Furthermore, in the same figure (C), four unit blocks 32 to 35 are used, and the mechanical skew amounts are set to gl to g4, respectively, and the sum of these skew amounts is the above-mentioned skew m
The laminated iron core 36 is constructed so that it becomes g. With this configuration as well, the skew effect as the sum of the mechanical skew and the pseudo skew can be obtained in the same manner as in the above-described embodiment.

In the above embodiment, the slot 18 is fully open, but the slot 18 is not limited to this, and may be half open.
A double cage type or a deep groove cage type other than the normal cage type may be used, and the value of the distance Md is set as shown in formula (A), but is not limited to this, and can be within the range shown in formula (A). It's good to have.

Further, in each of the above embodiments, the case where two or four 171st blocks are provided has been described, but the gist of the present invention is that the structure is not limited to this, and may be provided with three or five or more blocks. Various modifications are possible without departing from the above.

[Effects of the Invention] As explained above, according to the squirrel cage rotor of the present invention,
The laminated iron core is composed of a plurality of unit blocks, and the bridge part or the opening of the slot in these unit blocks is set at a distance d within the range shown by formula (A) from the center line of the main part, so this alone can reduce the skew. The same effect as that obtained by applying skew is obtained, and since a predetermined amount of skew is applied to at least one unit block, an even greater skew effect can be obtained than when only mechanical skew is applied. As a result, the rotor can minimize the generation of abnormal torque due to harmonic components, as well as the generation of vibration and noise. The excellent effect of suppressing the position torque without applying a large mechanical skew is demonstrated.

[Brief explanation of the drawing]

Figures 1 to 8 are principle diagrams for explaining the present invention in detail, Figure 1 is a partially cutaway perspective view of the appearance of the laminated core, and Figure 2 is for determining the pseudo skinny coefficient. Figure 3 is a diagram equivalent to Figure 1 for determining the mechanical skew coefficient, Figure 4 is an explanatory diagram showing the state of magnetic flux entering the slot, and Figure 5 is a diagram equivalent to Figure 1 for determining the mechanical skew coefficient. FIG. 6 is an explanatory diagram showing the induced electromotive force. FIG. 6 is an explanatory diagram showing the mechanical skew effect. FIGS. 7(a) and (b) are the laminated core with only mechanical skew and the laminated core of this example. An explanatory diagram of the position torque reduction effect shown from the outer circumferential side,
FIG. 8 is a diagram showing various calculation examples. Figures 9 to 1
Fig. 2 shows an embodiment of the present invention, Fig. 9 is a partially cutaway perspective view of the appearance of the laminated core, Fig. 10 is a partial plan view of the steel plate, and Fig. 11 is a vertical cross-sectional side view of the overall configuration. 12 are diagrams showing calculation results of skew coefficients, and FIG. 13 is a diagram corresponding to FIG. 7 showing a modification of the above embodiment. In the drawings, 1.1', 1', 17.28.31 and 36
2, 2' and 23 are punched parts, 3.3' and 22 are steel plates, 4A, 4B, 24.25, 26. 27
．． 29. 30. 32. 33. 34 and 35 are unit blocks, 5.5' and 18 are slots, 5a and 23g are main parts, 5b and 23b are bridge parts (or openings), 6 and 19 are secondary conductors, 11 is a stator, 12 1 is a stator core, 15 is a squirrel cage rotor, 16 is a rotating shaft, 20 is an end ring, and 21 is a squirrel cage conductor.

Claims (1)

[Scope of Claims] 1. In a squirrel cage rotor formed by laminating a predetermined number of steel plates having punched parts for forming slots for accommodating conductors on the outer periphery to form a laminated iron core, the steel plate The punched part is formed in an asymmetrical shape such that the bridge part or opening on the outer peripheral side is shifted to one side by a distance d that satisfies the following condition with respect to the center line of the main part in which the conductor is housed. The laminated core is constructed by combining a plurality of unit blocks in which a plurality of the steel plates are laminated so that the directions of the slots are the same, and the directions of the slots are different between the unit blocks, and the main portion is A squirrel cage rotor characterized in that the plurality of laminated cores are configured to overlap each other, and at least one of the plurality of sets of laminated cores is skewed by a predetermined amount. πD/4(z+p)≦d≦πD/4(z+p) However, D
: Rotor diameter z: Number of corresponding stator slots p: Number of pole pairs