KR910000879B1 - Polar switch type electric motor - Google Patents

Abstract

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Description

Polar switch type electric motor

1-7 show one embodiment of the invention, in which FIG. 1 is a partial cross-sectional view of the rotor.

2 is a partial cross-sectional view of the motor.

3 is a coil arrangement diagram of the high-speed winding.

4 is a coil arrangement diagram of a low-speed winding.

5 is the magnetic force waveform of the low-speed winding.

6 is a speed-torque characteristic diagram in operation by the high-speed winding.

7 is a speed-torque characteristic diagram in operation by a low-speed winding.

8 is an equivalent view of FIG. 1 showing a variation of the rotor.

9 is a coil development diagram showing a modification of the low-speed winding.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pole number switching type motor that aims at improving torque characteristics during low speed operation.

Conventionally, for example, in the case of a machine tool, a control method of lowering the machine speed first and then operating a brake when the target position is approached for the purpose of improving the feeding position accuracy is often adopted. Pole-switched induction motors with large pole-number ratios are used.

However, in such a pole number switching type induction motor, there is a problem in that the torque decrease during the low speed operation is severe. I'll explain why.

In general, the torque (T) of an induction motor is represented by the following equation (1).

Where m: stator constant, s: slip, v: phase voltage, ω ₀ : synchronous angular velocity, r ₁ : primary resistance, r ₂ : primary converted secondary resistance, x ₁ : primary liquid reactance, x ₂ : 1st conversion 2nd liquidity reactance.

As is apparent from Equation (1) above, the torque T becomes a function of the resistances r ₁ and r ₂ and the liquid reactance x ₁ and x ₂ , and as they increase, the torque T decreases. By the way, since the number of poles increases on the low speed side in the pole switch type induction motor, their motor constants increase as described below.

(1) As the number of poles increases, the number of turns of the stator winding increases, so that the primary resistance r ₁ and the primary liquid reactance x ₁ increase.

(2) The primary converted secondary resistance (r ₂ ) and the primary converted secondary liquid reactance (x ₂ ) are proportional to the number of turns ² × poles, so when the poles are large, r ₂ and x ₂ become extremely large.

As a result, in the induction motor of the pole-number conversion type, the torque decreases or worsens at the low speed side where the pole number becomes large.

In general, skew is provided to the dense conductor of the rotor of an induction motor to suppress noise and abnormal torque during high speed operation, but this also causes a decrease in torque during low speed operation. That is, the secondary resistance (r ₂ ) and the liquid reactance (x ₁ , x ₂ ) are constants of the screw amount of the thick conductor, and these are represented by the following formulas (2) and (3).

Here, K is a skew factor, where r is the harmonic order of the gap magnetic flux, and the skew amount expressed by the electric angle is represented by the following equation (4).

By the way, in this type of conventional motor, the amount of skew is generally one slot pitch of the stator. Therefore, during high speed operation with a large pole pitch, the skew amount? Is represented by the electric angle, and the influence of the skew on the fundamental wave component can be almost ignored. Therefore, only the influence of the skew on the harmonic component is considered. For example, when the number of slots is 36 and the number of poles of the high-speed pole is 4, the harmonic order due to the influence of the slot of the gap magnetic flux is 17th and 19th order, and the skew factor K at that time is 0.059 and 19th order for the 17th order. As regards this, the value is -0.052, which is extremely small compared to the skew factor 0.995 of the fundamental wave component. Therefore, the torque due to the slot harmonics is extremely small, and the abnormal torque can be suppressed to improve the operating characteristics.

However, at low speed operation, the pole number is large and the pitch is small, so the amount of skew? Represented by the electric angle is large, and the influence of the skew on the fundamental wave component cannot be ignored. For example, when the skew factor (K) for the fundamental wave component is obtained at 32 poles, the value becomes small as 0.705. As a result, the secondary resistance (r ₂ ) and the liquid reactance (x ₁ , x ₂ ) become large, and the torque T Is greatly reduced. In particular, in the operating state where the slip s is close to zero, the torque T is approximately proportional to the square of the skew factor K, so the torque is about 1/2 compared with the case where there is no skew.

As described above, the conventional pole number switch type induction motor has a problem that the torque reduction during the operation at the low speed side cannot be avoided.

SUMMARY OF THE INVENTION An object of the present invention is to provide a pole switching motor capable of preventing torque reduction during low speed operation without damaging the characteristics of the motor during high speed operation.

In the first invention of the present invention, a rotor of a pole-switched electric motor having a stator wound with an armature winding that can be pole-switched for high speed or a low speed and a rotor having a thick conductor is n of the number of poles for the low speed of the armature winding. It was assumed that it had magnetic anisotropy which became the pole number of double (n is positive integer).

In the second invention of the present invention, the rotor of the pole-switch type electric motor having a stator wound with an armature winding that can be pole-switched for high speed or low speed and a rotor having a thick conductor is used for the low speed pole of the armature winding. It was assumed that the magnetic anisotropy was n times (n is a positive integer) and the skewed conductors were skewed.

When operating with a low speed armature winding, the rotor is given magnetic anisotropy, so the reluctance torque generated between the rotor and the rotor generated by the armature winding mainly acts and rotates as a reluctance motor. In this case, the rotor can obtain a large torque in synchronization with the rotor field.

On the other hand, since the number of poles of magnetic anisotropy given to the rotor when operating by using the high-speed armature winding has no effective relationship between the number of poles of the high-speed armature winding, the reluctance torque is hardly generated and only the induction torque is effectively generated. It is rotated as a normal induction motor.

Furthermore, when skewing the dense conductors, the amount of skew can be selected to further reduce the induction torque remaining when the low-speed armature winding is used to operate, so that the reluctance torque can be utilized more effectively.

In this case, when the high speed armature winding is used for operation, the amount of skew represented by the electric angle becomes small, which does not impede the generation of induction torque, and can suppress the abnormal torque due to the expected skew.

An embodiment of the present invention will be described below with reference to FIGS. 1 to 7.

FIG. 2 is a partial sectional view showing the overall configuration of the present embodiment. In FIG. 2, the stator iron core 2 having 36 slots is fixed inside the cylindrical motor frame 1, and the stator is fixed. The armature winding 3 is wound around the iron core 2. In addition, the rotor 4 is freely rotated inside the stator iron core 2 via a bearing 5 provided in the motor frame 1. The armature winding 3 has a double winding structure so that the number of poles can be used interchangeably, and is composed of, for example, a high speed winding 3a of four poles and a low speed winding 3b of 32 poles.

First, the high speed side winding 3a will be described in detail. This is constituted by a general four-pole overlapping winding, and as shown in FIG. That is, the U-phase winding is delivered to each slot of slot numbers 1,2,3,10,11,12,19,20,21,28,29,30, and the numbers 1,2,3,19,20, The conductor in each slot of 21 and the conductor in each slot of Nos. 10, 11, 12, 28, 29, and 30 are reversed in the direction in which current flows. In addition, the V-phase winding is delivered to each slot of No. 7,8,9,16,17,18,25,26,27,34,35,36, and each of No. 7,8,9,25,26,27 This is the connection through which current flows in the reverse direction between the conductor in the slot and the conductor in the slots 16, 17, 18, 34, 35 and 36.

And the W-phase winding is inserted into each slot of the number 13,14,15,22,23,24,31,32,33,4,5,6, and the angle of the number 13,14,15,31,32,33 It is a wiring through which current flows in the reverse direction from the conductor in the slot and the conductor in the slots 22, 23, 24, 4, 5 and 6.

Moreover, the low speed side winding 3b is the same as that described in Unexamined-Japanese-Patent No. 57-27654, and a coil is arrange | positioned in each slot as shown in FIG. That is, the upper coil of the U-phase winding is delivered to each slot of numbers 1,6,8,10,15,17,19,24,26,28,33,35, and the lower coil of the U-phase winding has the number 2, 7,9,11,16,18,20,25,27,29,34,36 are delivered to each slot and reverse current flows through the upper coil and the lower coil. The upper coil of the V-phase winding is numbered 2, 4, 9, 11, 13, 18, 20, 22, 27, 29, 31, 36, respectively, and the lower coil of the V-phase winding is numbered , 1, 3, 5, 10, 12, 14, 19, 21, 23, 28, 30, 32, respectively, and the upper coil and the lower coil, the reverse current flows. The upper coils of the W-phase windings are delivered in slots 3, 5, 7, 12, 14, 16, 21, 23, 25, 30, 32, 34, and the lower coils of the W-phase windings are numbered 4, 6,8,13,15,17,22,24,26,31,33,35 are delivered to each slot, and current flows in the upper coil and the lower coil in the reverse direction.

On the other hand, the rotor 4 has, for example, 44 concentrated conductors 6 injected into the totally closed slot 4a as shown in FIG. Skew is given to this thick conductor 6, and the amount of skew is set to about 2 poles of the 40-pole component which is a harmonic component among the gap magnetic flux which the low speed side winding 3b produces. As shown in FIG. 1, thirty-two protruding poles 7 are formed on the outer periphery of the rotor 4 at equiangular intervals. This is formed in the form of extending in the axial direction of the rotor 4, for example, by drilling each iron plate constituting the rotor 4 into a shape having 32 protruding pieces on the outer circumference and stacking a predetermined number thereof.

Magnetic anisotropy is provided to the rotor 4 by this protruding pole 7. The number of poles 32 of the protruding pole 7 is the same as the number of poles 32 of the low speed side winding 3b of the armature winding 3.

Next, the operation of the above configuration will be described. When the high-speed winding 3a is energized, a four-pole rotor field is formed, induction torque is generated between the dense conductors 6, and the rotor 4 is rotated. At this time, since the number of poles of the magnetic field is 4 and the number of the protruding poles 7 of the rotor 4 is 32, the reluctance torque is hardly generated and the induction torque has good torque characteristics as usual by the induction torque. Is rotated. In this case, the presence of a large number of projecting poles 7 causes pulsation in the gap's permeability, which increases the harmonic content of the gap magnetic flux, thereby affecting the torque characteristics at a speed of slip close to one. You can think of it. In practice, however, as shown in the speed-torque characteristic shown in FIG. 6, only a slight pulsation is recognized in the speed region where the slip is close to 1 (the region indicated by A in the figure), and practically no problem occurs.

는 실극간에 형성된 허극을 나타내고 계 32극이 형성되어 있다. 이 저속극의 극수 32는 회전자(4)의 돌출극(7)의 극수 32와 동수이므로 동기속도 부근에서 큰 리럭턴스 토오크가 발생되어 결국 회전자(4)는 동기속도로 회전된다. 이로 인해서 32극의 회전자계와 농형도체(6)와의 사이에는 슬립이 생기지 않으므로 기본파(32극)의 회전자계에 의한 유도토오크는 전혀 생기지 않는다. 또 일반적으로는 저속도의 회전자계에서는 갭자속 분포에 큰 고조파성분을 포함하는 경우가 많다.On the other hand, when energizing the low-speed winding 3b, it rotates as a reluctance motor at a synchronous speed as follows. The magnetic force distribution by the low-speed winding 3b becomes as shown in FIG. 5, for example, when each of the U-phase current is 1, the V-phase and the W-phase current are -0.5. In the same figure, N represents a real pole,

Represents a virtual electrode formed between the real electrodes and a 32-pole system is formed. Since the number of poles 32 of the low speed pole is the same as the number of poles 32 of the protruding pole 7 of the rotor 4, a large reluctance torque is generated near the synchronous speed, and the rotor 4 is rotated at the synchronous speed. Thus, no slip occurs between the 32-pole rotor and the dense conductor 6, so that no induced torque is generated by the rotor of the fundamental wave 32 pole. In general, large harmonic components are often included in the gap magnetic flux distribution in a low-speed rotor magnetic field.

In the low speed side winding 3b of this embodiment, a 40-pole component is included as such a harmonic component, and there exists a possibility that the induction torque produced by this component may reduce reluctance torque. In the present embodiment, however, the skew amount corresponding to the electric angle is approximately 2 times the pole pitch of the 40-pole component of the dense conductor 6, so that the skew amount becomes 2π so that the skew factor becomes zero (0). Induction torque is not generated for the harmonic components of the pole, so there is no fear of reducing the reluctance torque. In addition, the speed-torque characteristics in low speed operation are the same as those shown in FIG. When switching to the low-speed winding 3b during high speed operation, the motor enters the fourth upper limit of the graph, generates a large deceleration torque, follows the curve indicated by the solid line, and finally reaches the point B and rotates at a synchronous speed of 32 poles. The dashed line in the same figure shows the torque curve of the conventional example which rotates the low speed side of 32 poles as an induction motor, and compared with this, it is clear that in this embodiment, about 3 times or more of the conventional torque at low speed operation is obtained.

As described above, in the present embodiment, the high speed is operated as an induction motor, and the low speed is operated as a reluctance motor, so that the torque reduction, which has been a problem at the time of low speed operation, can be prevented. Both torque and low-speed operation can obtain good torque characteristics.

Furthermore, since the rotor is provided with the projecting pole 7 to give magnetic anisotropy, the structure is extremely simple. For example, the above-mentioned effect can be obtained simply by replacing the rotor of the existing pole-numbered conversion motor. Is extremely wide.

In addition, this invention is not limited to the said Example, For example, the following modifications are possible.

(1) The number of poles of the protruding pole may be a multiple of the number of poles of the protruding pole and the number of poles of the low speed side may be doubled even if the number of poles of the protruding pole is not necessarily the same as that of the low speed side pole.

(2) In order to give the rotor magnetic anisotropy, even if it does not necessarily form the protruding pole 7 as in the above embodiment, as shown in FIG. You may have polarity. In such a case, it is needless to say that the number of teeth 8 must be in the same or drainage relationship with the low speed pole water.

(3) In the above embodiment, the width dimension of the protruding pole 7 is set so that the proximal end or the proximal side is the same, but the present invention is not limited thereto, and the protruding pole 7 may have a narrower shape as the proximal end.

(4) In the above embodiment, since the harmonic component of 40 poles is generated due to the characteristics of the low-speed winding 3b, about 2 poles of about 40 poles are applied to the dense conductor 6 so as to offset the induced torque caused by the harmonic component. If the harmonic content at low speed is small, such skew can be omitted. In this case, the skew of one slot pitch of the stator slot improves the characteristic at high speed.

Alternatively, the amount of skew given to the dense conductor 6 may be set to, for example, twice the pole pitch of the low-speed winding 3b, for example, to suppress the induction torque during low-speed operation.

(5) In the above embodiment, the case where the low speed side pole number is 32 poles is illustrated. However, the present invention is not limited to this. For example, 24 poles may be used, and the high speed side pole number is not limited to 4 poles. Of course it can.

(6) The number of concentrated conductors is not limited to 44 as shown in the above embodiment, but may be set to an appropriate number, for example, 28 and so on. In this case, it is possible to select independently of the number of poles of the protruding poles. There is no need to reconsider.

(7) In addition, in the case of a stator having 36 slots, the low speed side winding 3b may wind a three-phase winding as shown in FIG. 9, and in FIG. 9, the terminals U ₁ -U ₂ , V ₁ -V ₂ , and W ₁ -W ₂ in turn energize each adjacent tooth of the stator ₂ , and the protruding poles 7 of the rotor 4 project, for example, in 48 cases. The rotor 4 is rotated by 1/3 of the pole pitch. As a result, the electric motor is driven as a stepping motor by the reluctance torque, and a large torque can be obtained.

In this case, if the position of the rotor 4 is detected and the low-speed winding 3b is energized sequentially, it can be operated as a so-called switched reluctance motor.

As described above, according to the present invention, since the rotor is subjected to magnetic anisotropy, the pole-changeable motor has a reluctance torque during operation by a low speed winding even though the rotor is rotated by an induction torque during operation by a high speed winding. Is driven by. Therefore, the torque characteristic at low speed operation can be improved, without impairing the characteristic at high speed operation. In addition, when the rotor is further skewed, the residual induction torque during low speed operation can be suppressed, so that the reluctance torque can be utilized more effectively.

Claims (7)

In a pole-switched electric motor having a stator (2) to which an armature winding (3) capable of switching poles for high speed or a low speed and a rotor (4) having a thick conductor (6), the armature winding (3) A pole switching motor comprising the rotor (4) having magnetic anisotropy, the number of poles being n times (n is a positive integer) of the number of poles for low speed. 2. The pole change type electric motor according to claim 1, wherein the rotor (4) has a protruding pole (7). The pole switch type electric motor according to claim 1, wherein the thick conductor (6) of the rotor (4) is accommodated in an open slot. In a pole-switched electric motor having a stator (2) to which an armature winding (3) capable of switching poles for high speed or a low speed and a rotor (4) having a thick conductor (6), the armature winding (3) Pole-switched type, characterized in that the rotor (4) having magnetic anisotropy, which is n times the number of poles for low speed (n is a positive integer), is given skew to the dense conductor (6). Electric motor. 5. The skew amount given to the dense conductor 6 is set equal to the even multiple of one pole of the harmonic component of the gap magnetic flux formed by the low speed side winding 3b of the armature winding 3. Pole-switched electric motor. 5. The pole-number switch type electric motor according to claim 4, wherein the amount of skew given to the dense conductor (6) is set equal to the even multiple of the pole pitch of the low speed side winding (3b) of the armature winding (3). 5. The pole-number switch type electric motor according to claim 4, characterized in that the amount of skew given to the thick conductor (6) is set equal to one slot pitch of the slot of the stator (2).

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