JPS63274349A - Number of pole change type motor - Google Patents

Abstract

PURPOSE:To improve torque characteristics at the time of revolution at low speed by mounting an armature winding with changeable number of poles, a cage type rotor and a salient pole rotor and setting the quantity of skew of the cage type rotor at the even times of the pole pitches of low-speed poles for the armature winding. CONSTITUTION:A stator core 2 with a plurality of slots are installed to a frame 1, and a coil 3 is wound. The pole number of the coil 3 can be changed by duplex winding, and is composed of a high speed side winding 3a in four-pole concentric winding and a low speed side winding 3b at thirty-two poles. A cage type rotor 7 and a salient pole rotor 9 are fixed concentrically to a shaft 5 rotatably supported to bearings 4, 4. Cage type conductors 6 for the cage type rotor 7 are skewed, and the quantity of the skew is set at the even times of the pole pitches of the low speed side winding 3b. The pole number of salient poles 8 for the salient pole rotor 9 is set to the pole number of thirty-two of the low speed side winding 3b. Accordingly, a skew effectively works on high- speed operation and the title motor functions as an induction motor, and the skew is nullified on low-speed operation and the title motor serves as a synchronous motor, thus generating large torque.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a pole-converting electric motor with improved torque characteristics during low-speed driving.

(Prior Art) In recent years, variable speed operation of electric motors using inverters has been progressing, and there is a demand for widening the variable speed range to 1:100 or more. Particularly recently, not only the hI speed range has been increased, but also applications such as direct drives that require high torque at low speeds have increased, and there is a demand for electric motors that can obtain high torque over a wide speed range. however,
When an induction motor is driven by an inverter, a decrease in torque in the low speed range cannot be avoided, so the fact is that the variable speed range cannot be sufficiently expanded with a single pole number.

Therefore, as a motor used in a wide speed range such as , it is recommended to use an inverter to drive a pole change type induction motor equipped with a switchable armature winding having a large pole ratio such as 4/32 poles. is also being considered.

(Problem to be solved by the invention) However, even if such a maximum conversion type electric motor is used,
The drawback was that the torque was significantly reduced during low-speed operation. The reason for this will be explained below.

Generally, the torque (T) of an induction motor is expressed by the following equation (1).

Tc r2 / ((s rl + r2
) '+8' (XI +X2) ” ) −
(1) rl Knee resistance “2: Secondary resistance x1
Knee leak reactance xl: Secondary leakage reactance S: Slip, secondary resistance r2, leakage reactance X1, xl
is a function of the skew amount of the cylindrical conductor, and these are expressed by the following equations (2) and (3).

r2 C<(1/I()' = (2)xl
+X20CA+ (B/ni') --(3) Here, K is the skew factor, γ is the harmonic order of the air gap magnetic flux, and θ is the skew amount expressed in electrical angle.
It is expressed by the following equation (4).

K m 5in (7θ/2)/(7θ/2)...
-.(4) Now, in a conventional electric motor of this type, the amount of skew is generally one slot pitch of the stator. Therefore, when operating with high-speed poles with a large pole pitch, the skew amount θ expressed in electrical angle is small and the effect of skew on the fundamental wave component can be almost ignored, so only the effect of skew on the harmonic component of the air gap magnetic flux should be considered. Bye. For example, when the number of slots is 36 and the number of high-speed poles is 4, the harmonic order due to the influence of the slots on the air gap magnetic flux is 17.
．． 19, and the skew factor I at that time is
0.059 for the 17th order, -0 for the 19th order,
052, and the skew factor of the fundamental wave component is 0.
This value is extremely small compared to 995. Therefore, the torque due to the slot harmonic adjustment is extremely small, and it is possible to suppress abnormal torque and improve the driving characteristics.

However, during operation using low-speed poles, since the pole pitch is small, the skew amount θ expressed in electrical angle is large, and the influence of skew on the fundamental wave component cannot be ignored. For example, if the skew factor K regarding the fundamental wave component is determined for 32 poles, it will be 0.705, and as a result, the secondary resistance r2 and leakage reactances XI and X2 will increase, and the torque T will decrease significantly. In particular, in an operating state where the slip S is close to 0, the torque T is approximately proportional to the square of the skew factor, so the torque is approximately half of that in the case where there is no skew.

As described above, in the conventional pole change type electric motor, there is a problem in that in order to improve the operating characteristics on the high speed side, it is impossible to avoid a decrease in torque during operation on the low speed side.

SUMMARY OF THE INVENTION Therefore, it is an object of the present invention to provide a maximum conversion type electric motor that can prevent a decrease in torque on the low speed side without impairing the operating characteristics on the high speed side.

[Structure of the Invention] (Means for Solving the Problems) The pole changeable motor of the present invention includes an armature winding that can change the number of poles on a stator core, and a cylindrical conductor on a common shaft. A cylindrical rotor having a cylindrical rotor and a salient pole rotor having a plurality of salient poles are provided, and the skew amount of the cylindrical conductor is set to an even multiple of the pole pitch of the low speed poles of the armature winding. It has the following.

(Function) During high-speed operation, the motor rotates as an induction motor due to the induced torque generated between the rotating magnetic field by the high-speed pole and the cylindrical conductor. In this case, since the amount of skew of the cylindrical conductor is sufficiently small compared to the pole pitch of the high-speed pole, the schiero θ expressed in electrical angle is also small, making it possible to suppress abnormal torque and obtain good operating characteristics as in the conventional case. can.

On the other hand, during low-speed operation, the skew amount of the cylindrical conductor is an even number multiple of the pole pitch of the low-speed pole, so the skew factor is 0, which is clear from equations (2) and (3). to the secondary resistance r2 and leakage reactance X1+X2
becomes significantly large, so the cylindrical rotor has an induced torque T
rarely occurs. However, since the salient pole rotor has a plurality of salient poles, a large reluctance torque is generated between the rotating magnetic field of the low-speed pole and the salient pole rotor, and the rotor rotates as a synchronous motor.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

First, in FIG. 1 showing the overall configuration, 1 is a motor frame, 2 is a stator core with, for example, 36 slots, and 3 is an armature winding wound around the stator core. The armature winding 3 has a double winding structure, for example, so that the number of poles can be changed, and is composed of a high-speed side winding 3a of 4-pole concentric winding and a low-speed side winding 3b of 32 poles.

First, the high-speed side winding 3a will be described. This is constituted by general four-pole overlapping winding, and the specific winding arrangement is shown in FIG. 3.

Here, the U-phase windings are numbers 1, 2.3, 19.20°21
The conductors in each slot and numbers 10.11, 12.28,
The connection is such that the direction of current flow is opposite to that of the conductor in each slot of 29.30. Also, is the V phase winding number? ,
Conductors in each slot of 8, 9, 25, 26.27 and number 16.17.1g.

This is a connection in which current flows in the opposite direction to the conductors in each slot of 34, 35, and 36. And the W phase winding is number 13
, 14, 15.31, 32.33 and the conductors in the slots numbered 22, 23, 24.4, 5.6 are wire connections in which current flows in opposite directions. The low-speed side winding 3b is the same as that detailed in Japanese Patent Publication No. 57-27654, with a coil arranged in each slot as shown in Fig. 4, and an upper coil and a lower coil for each phase. The wire is connected to the coil so that current flows in the opposite direction.

On the other hand, in FIG. 1, reference numeral 4 indicates a pair of bearings provided on the motor frame 1, and reference numeral 5 indicates a shaft rotatably supported by the bearing 4. The rotors of are fixed concentrically. one is second
As shown in Figure (A), a cylindrical rotor 7 is equipped with a well-known cylindrical conductor 6, and the other one is equipped with several m salient poles 8 on its outer peripheral surface as shown in Figure 2 (B). This is a salient pole rotor 9 equipped with a salient pole rotor 9. The cylindrical conductor 6 of the cylindrical rotor 7 is skewed, and the amount of skew is set to an even number multiple, for example twice, of the pole pitch of the low-speed winding 3b. Further, the salient pole rotor 9 is formed by punching an iron plate into a shape having several protruding pieces on the outer periphery and stacking a predetermined number of these pieces so that the salient poles 8 extend in the axial direction.
The number of salient poles 8 is set to be the same as the number of poles 32 of the low-speed winding 3b, for example.

Next, the operation of the above configuration will be explained. High speed side winding 3a
When energized, a four-pole rotating magnetic field is formed, and the cylindrical conductor 6
An induced torque is generated between the cylindrical rotor 7 and the cylindrical rotor 7, and output is taken out from the shaft 5. At this time, almost no reluctance torque is generated in the salient pole rotor 9, and due to the induction torque, the salient pole rotor 9 rotates as an induction motor having good torque characteristics like a normal rotor.

On the other hand, when the low-speed winding 3b is energized, it rotates as a synchronous motor at a synchronous speed in the following manner. For example, when the U-phase current is 1 and the V-phase and W-phase currents are -0 and 5, the magnetomotive force distribution due to the low-speed side winding 3b is as shown in FIG. 5. In the figure, N indicates a real pole, and ■ and ■ indicate imaginary poles formed between the real poles, and a total of 32 poles are formed. The number of low-speed poles is 32, and the number of salient poles of the rotor 4 is 7.
Since the number of poles is the same as 32, a large reluctance torque is generated near the synchronous speed, and as a result, the salient pole rotor 9 rotates at the synchronous speed and the output is also taken out from the shaft 5. In this case, the cylindrical conductor 6 of the cylindrical rotor 7 is skewed by twice the pole pitch of the low-speed poles, and the skew amount θ expressed in electrical angle is 2π, so the skew factor is is O for the fundamental wave (γ-1) as is clear from equation (4), and no induced torque is generated between the cylindrical conductor 6 and the fundamental wave (γ-1). As a result, only the reluctance torque generated in the salient pole rotor 9 is used as a synchronous motor.

In this way, according to this embodiment, during high-speed operation, the motor rotates as an induction motor with effective skew, and during low-speed operation, the skew is disabled and the motor rotates with a large torque as a synchronous motor using reluctance torque. While maintaining excellent driving characteristics, it can be operated without causing a decrease in torque in the low speed range, which has been a problem in the past. Moreover, during low-speed operation, it rotates at a constant synchronous speed without slipping, so when operating at high speed to a target position and then switching to low-speed operation to perform positioning control, it is extremely fast compared to conventional induction motors. Accurate positioning control becomes possible.

In the above embodiment, the stator winding was made into a fi'a configuration that can convert the number of poles to 4/32 poles, but the pole number ratio could be changed to 4/30 poles or 2/32 poles.
Of course, other pole number ratios such as 20 poles may also be used.
In addition, it is not limited to those that change the number of poles using the double winding method.
Of course, the pole number conversion may be performed using the l1i-winding method. Furthermore, even if the rotor position is detected during low speed operation and the armature windings are sequentially energized to operate as a so-called switched reluctance smoke mode, the same effect as in the embodiment 1) can be obtained. .

[Effects of the Invention] As described above, the present invention includes an armature winding that can change the number of poles, a cage rotor, and a salient pole rotor, and the skew amount of the cage rotor can be adjusted by changing the skew amount of the cage rotor. The characteristic is that the pitch of the low-speed poles of the line is set to an even number multiple of the pole pitch.This allows operation with excellent driving characteristics by taking advantage of the skew during high-speed operation, and allows operation with large reluctance torque during low-speed operation. Therefore, it is possible to significantly improve the torque characteristics on the low speed side without impairing the driving characteristics on the high speed side, which is an excellent effect.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, in which Fig. 1 is a partial cross-sectional view of the electric motor, Fig. 2 is a partial cross-sectional view of the rotor, Fig. 3 is a coil arrangement diagram of the high-speed side winding, and Fig. 4 is a low-speed side winding. The coil arrangement diagram of the side winding, and FIG. 5 is a magnetomotive force waveform diagram of the low speed side winding. In the drawing, 3 is the armature winding, 3a is the high-speed side winding, 3b is the low-speed side winding, 5 is the shaft, 7 is the cage conductor, 7 is the cage rotor, 8 is the salient pole, and 9 is the salient pole. It is a rotor.

Claims (1)

[Claims] 1. An armature winding whose number of poles can be changed is provided on the stator core, and a cage rotor having a cage conductor and a salient pole rotor having a plurality of salient poles are provided on a common shaft, 1. A pole-converting motor, characterized in that the skew amount of the cage conductor is set to an even multiple of the pole pitch of the low-speed poles of the armature winding.