JP3562287B2 - Control method and control device for induction machine with built-in magnet - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention provides a stator that generates a rotating magnetic field, a rotor that is fixed to a shaft and rotates in the stator, and is disposed in a hollow space formed in the rotor and has a rotating magnetic field of the stator on the outer periphery. The present invention relates to a control method and a control device for an induction machine with a built-in magnet, comprising a magnet holding member rotatably supported on a shaft and having a magnet attached so as to face each other.
[0002]
[Prior art]
Induction motors have been widely used in various industrial fields because they are robust, inexpensive, and do not require speed control. In the past, DC motors were the mainstream when used at variable speeds, but advances in power electronics elements and control technologies such as vector control have enabled variable speed operation of induction motors. It is replacing the motor. The principle of this induction motor is that a current is applied to a primary coil disposed on a stator to generate a magnetic flux, and this magnetic flux generates an induction current on a rotor side, and a torque is generated by an interaction between the magnetic flux and the induction current. Is generated. This existing induction motor has a problem that the magnetic flux generated by the stator bypasses (does not enter the inside of the rotor) and the magnetic flux density in the radial direction of the rotor that contributes to the generation of torque is small.
[0003]
As an induction motor that solves this problem, the present applicant has disclosed an induction motor with a built-in magnet that includes a magnet that rotates in synchronization with a rotating magnetic field of a stator in a rotor. And Japanese Patent Application Laid-Open No. 8-289515. The configuration of the induction machine with a built-in magnet will be described with reference to FIG.
[0004]
A plurality of slots 24 are provided on the inner periphery of the stator 22, and a winding 23 is arranged in each slot 24. A rotor 26 incorporating a car is fixed to the shaft 32. The car is composed of a pair of short-circuit rings 28b (only one is shown in FIG. 6) and a plurality of secondary conductors 28a, similarly to a conventional car-type induction motor. Inside the rotor 26, a steel cylindrical rotor 34 is arranged, and the cylindrical rotor 34 is rotatably supported with respect to the shaft 32 by a pair of bearings (not shown). Four permanent magnets 36 are attached to the outer periphery of the cylindrical rotor 34 in accordance with the number of poles (fields) of the magnet built-in induction machine 20.
[0005]
In the induction machine 20 with a built-in magnet, since the magnet 36 is attached to the surface of the cylindrical rotor 34 so as to face the rotating magnetic field of the stator 22, when the stator 22 is excited and the rotating magnetic field is generated, it is synchronized with this. The tubular member 34 rotates. The magnetic flux generated in the stator 22 is directed toward the magnet 36 facing the stator, and therefore crosses the rotor 26 in the radial direction. That is, since the magnetic flux traverses the rotor 26 in the radial direction, the torque generated in the rotor 26 increases.
[0006]
[Problems to be solved by the invention]
It has been found that the induction motor with a built-in magnet has a higher generated torque, but has a reduced responsiveness during rapid acceleration, deceleration, or reversal as compared with an existing induction motor.
The experimental results of the response will be described with reference to the graph of FIG. FIG. 7A shows a measurement result of an existing induction motor. FIG. 7B shows a measurement result of an induction machine with a built-in magnet. Here, a lamp input with a power factor of 1 and a drive frequency changed from 31.2 KHz (pulse interval of about 3 (ms): rotation speed of 900 rpm) to 50.3 KHz (pulse interval of about 2 (ms): rotation speed of 1500 rpm) (Acceleration time 0.1 S) was measured.
[0007]
Here, the existing induction motor had a rise time of 21.4 (ms), whereas the induction motor with a built-in magnet had a rise time of 24.4 (ms). The delay time of the existing induction motor was 30.8 (ms), while that of the induction motor with a built-in magnet was 31.2 (ms). The settling time of the existing induction motor was 125.4 (ms), while that of the magnet-equipped induction machine was 204.3 (ms). The overshoot time was 50.2 (ms) for the induction motor, while it was 67.0 (ms) for the induction motor with a built-in magnet. Further, the overshoot amount was 5.2% for the induction motor and 29% for the induction motor with a built-in magnet.
[0008]
It is considered that the reason for the decrease in the response is that the tubular rotor 34 cannot follow the change in the rotating magnetic flux at the time of rapid acceleration, deceleration, or reversal, and loses synchronization.
[0009]
The present invention has been made to solve the above-described problem, and an object of the present invention is to provide a control method and a control device of a magnet-responsive induction machine having high responsiveness.
[0011]
[Means for Solving the Problems]
According to the first aspect , a stator that generates a rotating magnetic field, a rotor that is fixed to a shaft and rotates in the stator, and is disposed in a hollow space formed in the rotor, A magnet is attached so as to face the rotating magnetic field, and a magnet holding member rotatably supported on the shaft.
The difference between the speed values of the actual rotation of the rotor and the speed command value for rotating the rotor is determined whether a predetermined value in the following,
When the difference is within a predetermined value, control to keep the magnetizing current constant,
When the difference exceeds a predetermined value, control for increasing the magnetizing current is performed.
[0012]
In the method of controlling a built-in magnet induction machine according to claim 2, in claim 1, as a control to keep the magnetizing current constant, and technical means performs vector control.
[0013]
In the method of controlling a built-in magnet induction machine according to claim 3, in claim 2, technology to enhance the as a control to increase the magnetizing current, according to the difference between the actual speed value and a speed command value magnetizing current Characteristic.
[0014]
In the method of controlling a built-in magnet induction machine according to claim 4, in claim 2, as a control for increasing the magnetizing current, and technical features of increasing the magnetizing current constant value.
[0015]
In order to achieve the above object, in claim 5 , a stator that generates a rotating magnetic field, a rotor that is fixed to a shaft and rotates in the stator, and is disposed in a hollow space formed in the rotor. A magnet attached to the outer periphery of the stator so as to face the rotating magnetic field of the stator, and a magnet holding member rotatably supported on the shaft,
Determine whether the difference between the speed command value for rotating the rotor and the actual speed value of the rotation of the rotor is within a predetermined value,
When the difference is within a predetermined value , control to keep the magnetizing current constant,
When the difference exceeds a predetermined value , a technical feature is that a magnetizing current control means for controlling to increase the magnetizing current is provided.
[0017]
According to the control method of the built-in magnet induction machine according to claim 1, the difference between the actual speed value and a speed command value to determine whether the predetermined value in the following, when the difference exceeds a predetermined value, because it increases the magnetization current, fixed The magnet holding member can follow the rotating magnetic field of the child. For this reason, the responsiveness of the induction machine with a built-in magnet can be improved.
[0018]
According to the control method of the built-in magnet induction machine according to claim 2, the vector control, when the speed change is small, to keep the magnetizing current constant, it is possible to easily control the speed built-in magnet induction machine.
[0019]
According to the control method of the induction motor with a built-in magnet of claim 3 , when the speed change is large, the magnetizing current is increased according to the difference between the speed command value and the actual speed value. Is large, the magnet holding member can follow the rotating magnetic field of the stator.
[0020]
According to the control method of the built-in magnet induction machine according to claim 4, when the speed change is large, increasing the magnetizing current constant value. For this reason, complicated calculations are unnecessary and control is easy.
[0021]
According to the control device of the induction machine with a built-in magnet of the present invention, it is determined whether the difference between the speed command value and the actual speed value is within a predetermined value, and when the difference exceeds the predetermined value, the magnetizing current is increased. The magnet holding member can follow the rotating magnetic field. For this reason, the responsiveness of the induction machine with a built-in magnet can be improved.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a control method and a control device of an induction machine with a built-in magnet according to a first embodiment of the present invention will be described with reference to the drawings.
FIG. 1A shows a longitudinal section of a three-phase four-pole cage-type magnet-equipped induction machine 40 according to the first embodiment of the present invention, and FIG. 1B shows a transverse section of the rotor 26. As shown in FIG. 1A, a plurality of slots 24 are provided on the inner periphery of the stator 22, and a winding 23 is arranged in each slot 24. The stator 22 is the same as the conventional cage induction motor.
[0023]
As shown in FIG. 1B, the rotor 26 is fixed to a shaft 32, and the shaft 32 is rotatably supported by a pair of bearings 30A and 30B. The rotor 26 includes a rotor 28b on which a plurality of secondary conductors 28a are arranged, and frame rings 28C and 28D. Inside the stator 26, a steel cylindrical rotor 34 is provided, and the cylindrical rotor 34 is rotatably supported on the shaft 32 by a pair of bearings 38A and 38B. Four permanent magnets 36 are attached to the outer periphery of the cylindrical rotor 34 in accordance with the number of poles (fields) of the stator 22. The permanent magnet 36 is formed of a neodymium-iron-boron magnet.
[0024]
In the induction machine 40 with a built-in magnet, when a three-phase alternating current is applied to the winding 23 of the stator 22, a rotating magnetic field is generated in the direction of arrow A in the drawing. When the magnetic flux of the rotating magnetic field crosses each of the secondary conductors 28a of the rotor 26, a speed electromotive force is generated in the secondary conductor 28a, and a current flows in the secondary conductor 28a due to the speed electromotive force. The interaction between the current and the magnetic flux generates a torque to rotate the rotor 26 in the same direction as the magnetic field. This rotation speed has a slip in relation to the generated torque and is lower than the speed of the rotating magnetic field on the stator 22 side. On the other hand, since each permanent magnet 36 is attracted by the magnetic force generated on the stator side, the cylindrical rotor 34 rotates almost completely in synchronization with the rotating magnetic field generated on the stator 22 (accurately, slightly Has an angular delay). In the induction machine 20 with a built-in magnet, the magnetic flux is directed to the opposing permanent magnet 36, so that the magnetic flux crosses the secondary conductor 28 a of the rotor 26 in the radial direction. That is, since the magnetic flux crosses the secondary conductor 28a in the radial direction, the torque generated in the rotor 26 increases. Further, since the magnetic flux is supplied from the permanent magnet 36, the amount of the magnetizing current can be reduced, and the power factor increases.
[0025]
The principle of generation of this torque will be described in more detail with reference to FIG. As shown in FIG. 2A, the lines of magnetic force 90 from the winding 23 go to the facing permanent magnet 36, and the lines of magnetic force 90 from the permanent magnet 36 go to the facing winding 23. That is, the magnetic flux is directed in the radial direction of the rotor 26. Therefore, the velocity electromotive force e in one secondary conductor 28a which is relatively moving at a velocity v with respect to the magnetic flux B in the direction of the arrow C with the rotation of the rotating magnetic field is the effective magnetic flux according to the Fleming right hand rule. It is the product of the component and the velocity. Here, the effective magnetic flux component is a component in a direction perpendicular to the relative movement direction C (that is, in a radial direction of the rotor). Here, since the magnetic flux is directed in the radial direction, all the magnetic fluxes B Will work effectively. Therefore, the speed electromotive force e is represented by vBL (where L represents the length of the secondary conductor 28a).
[0026]
Further, the force F generated in the secondary conductor 28a will be described with reference to FIG. The current i flowing through the secondary conductor 28a is represented by i = e / R, where R is the resistance of the secondary conductor 28a. The force F generated by the interaction between the current and the magnetic flux in the secondary conductor 28a is the product of the magnetic flux B and the current i due to the speed electromotive force e according to Fleming's left hand rule, and F = (i × B) L Is represented by Since the generated force F is generated in a direction perpendicular to the magnetic flux B directed in the radial direction (that is, a tangential direction of the rotor 26), the generated force F is generated in a direction for rotating the rotor 26. Therefore, all the forces generated in the secondary conductors 28a are effectively used as the torque of the rotor 26.
[0027]
Subsequently, a control mechanism of the magnet-equipped induction machine 40 will be described with reference to FIG. An encoder 60 for detecting the number of rotations is attached to the magnet-equipped induction machine 40. The rotation speed detected by the encoder 60 is input to the control device 80. The control device 80 detects the amount of current applied to the induction machine with a built-in magnet 40 and the power factor of the current, and controls the rotation speed of the induction machine with a built-in magnet by adjusting the applied voltage and the frequency. Here, the control device 80 normally controls the torque by making the field constant and increasing / decreasing the secondary current by the vector control method. When the speed change is large, the field is strengthened, the followability of the cylindrical rotor 34 on which the permanent magnet 36 is mounted to the rotating magnetic field is increased, and the response is improved.
[0028]
The operation of controlling the magnetizing current (magnetizing current control means) by the control device 80 will be described in more detail with reference to the flowchart of FIG.
First, the control device 80 determines whether the difference between the speed command value and the actually measured value of the speed input from the encoder 60 is equal to or larger than the threshold δ, that is, whether the difference between the speed command value and the actually measured speed value is large. (S12). Here, when the difference is smaller than the threshold value δ (No in S12), that is, when there is no speed change and when the speed change is small, the magnetic flux amount is set to a fixed value φ0 and the magnet is controlled by the vector control method. The built-in induction machine 40 is controlled (S14). Here, when the amount of magnetic flux is φ0, the magnetizing current does not flow because the magnetic flux is supplied only by the permanent magnet 36. Alternatively, a part of the magnetic flux may be supplied by the permanent magnet 36, and the shortage may be supplied by the magnetizing current.
[0029]
On the other hand, when the difference between the speed command value and the actually measured speed value is equal to or larger than the threshold value δ (Yes in S12), that is, when the speed change is large, the control for keeping the magnetic flux amount constant is interrupted, and the magnetic flux amount ( The magnetizing current is increased according to the difference between the speed command value and the actual speed value (S16). Here, a value obtained by multiplying the constant k by the difference between the speed command value and the actual speed value is added to the constant magnetic flux amount φ0 as a control target value as the magnetic flux amount. As a result, the field is strengthened, the followability of the cylindrical rotor 34 on which the permanent magnet 36 is mounted to the rotating magnetic field is increased, and the response is improved. Then, the torque is made to respond to the command value at a high speed by changing the secondary current. In the control method of the first embodiment, the magnetizing current is increased according to the difference between the speed command value and the actual speed value. Therefore, even when the difference between the speed command value and the actual speed value is large, the control method is fixed. The cylindrical rotor 34 can follow the rotating magnetic field of the child 22.
[0030]
Subsequently, the control operation of the magnetizing current (magnetizing current control means) by the control device according to the second embodiment of the present invention will be described with reference to the flowchart of FIG. The configuration of the induction machine with a built-in magnet and the configuration of the control device according to the second embodiment are the same as those of the first embodiment described above with reference to FIGS.
[0031]
First, the control device 80 determines whether the difference between the speed command value and the actually measured value of the speed input from the encoder 60 is equal to or larger than the threshold δ, that is, whether the difference between the speed command value and the actually measured speed value is large. (S22). Here, when the difference is less than the threshold value δ (No in S22), that is, when there is no speed change and when the speed change is small, the magnetic flux amount is set to a constant value φ0 and the magnet is controlled by the vector control method. The built-in induction machine 40 is controlled (S24). Here, since the magnetic flux is supplied only by the permanent magnet 36, no magnetizing current flows. Alternatively, a part of the magnetic flux may be supplied by the permanent magnet 36, and the shortage may be supplied by the magnetizing current.
[0032]
On the other hand, when the difference between the speed command value and the actually measured speed value is equal to or larger than the threshold value δ (Yes in S22), that is, when the speed change is large, the control for keeping the amount of magnetic flux constant is temporarily stopped. (Magnetizing current) is increased from φ0 to a constant value φK (S26). As a result, the field is strengthened, the followability of the cylindrical rotor 34 on which the permanent magnet 36 is mounted to the rotating magnetic field is increased, and the response is improved. In the first embodiment described above, the amount of magnetic flux is increased in accordance with the difference between the speed command value and the actual speed value. However, in the second embodiment, the amount of magnetic flux is set to φK (constant) higher than φ0. Value). Thereafter, 1 is added to the variable n representing the elapsed time (S28), and it is determined whether the value of the variable n exceeds a preset constant m, that is, whether a certain time has elapsed (S30). Here, until the value of the variable n exceeds the constant m, that is, until a predetermined time has elapsed (No in S30), the process returns to step 26, and the high magnetic flux amount φK is maintained. Then, when the predetermined time has elapsed (Yes in S30), the process returns to step 22, and it is determined again whether the difference between the speed command value and the actually measured speed value is equal to or larger than the threshold value δ. In the control method of the second embodiment, the speed command value is increased irrespective of the difference between the speed command value and the actual speed value. Therefore, there is no need to calculate the magnetic flux command value, and the control is easy. There is.
[0033]
Although the cage-type induction motor has been exemplified in the above-described embodiment, the control method and the control device of the present invention can suitably control the winding-type induction motor. Similarly, an induction motor incorporating a permanent magnet 36 is illustrated as an example of an induction motor with a built-in magnet, but the control method and apparatus of the present invention can also enhance the responsiveness of an induction motor with a built-in electromagnet.
[0034]
【The invention's effect】
As described above, according to the present invention, when the speed is changed, the magnetizing current is increased, so that the cylindrical rotor can follow the rotating magnetic field of the stator. It becomes possible.
[Brief description of the drawings]
FIG. 1A is a longitudinal section of an induction machine with a built-in magnet according to a first embodiment of the present invention, and FIG. 1B is a cross-sectional view of a rotor of the induction machine with a built-in magnet. is there.
FIGS. 2A and 2B are explanatory diagrams of a speed electromotive force and a generated torque of the induction machine with a built-in magnet according to the first embodiment.
FIG. 3 is a block diagram illustrating a control mechanism of the induction machine with a built-in magnet according to the first embodiment.
FIG. 4 is a flowchart illustrating a process performed by a control device of the induction machine with a built-in magnet according to the first embodiment;
FIG. 5 is a flowchart illustrating a process performed by the control device for the induction machine with a built-in magnet according to the second embodiment.
FIG. 6 is a cross-sectional view illustrating a configuration of an induction machine with a built-in magnet.
FIG. 7A shows a measurement result of responsiveness of an existing induction motor, and FIG. 7B shows a measurement result of responsiveness of an induction motor with a built-in magnet.
[Explanation of symbols]
Reference Signs List 20 induction machine with built-in magnet 22 stator 26 rotor 28a secondary conductor 34 cylindrical rotor (magnet holding member)
36 permanent magnets (magnets)
60 encoder 80 control device

Claims (5)

A stator that generates a rotating magnetic field, a rotor that is fixed to a shaft and rotates in the stator, and is disposed in a hollow space formed in the rotor, and has an outer periphery that faces the rotating magnetic field of the stator. A magnet is attached to the magnet, and a magnet holding member rotatably supported on the shaft, the control method of the magnet built-in induction machine comprising:
The difference between the speed values of the actual rotation of the rotor and the speed command value for rotating the rotor is determined whether a predetermined value in the following,
When the difference is within a predetermined value, control to keep the magnetizing current constant,
When the difference exceeds a predetermined value, control for increasing the magnetizing current is performed. As a control to keep the magnetizing current constant control method according to claim 1 of the built-in magnet induction machine and performing vector control. 3. The control method for an induction machine with a built-in magnet according to claim 2 , wherein, as the control for increasing the magnetizing current, the magnetizing current is increased according to a difference between a speed command value and an actual speed value. 3. The control method for an induction machine with a built-in magnet according to claim 2 , wherein the control for increasing the magnetizing current includes increasing the magnetizing current by a constant value. A stator that generates a rotating magnetic field, a rotor that is fixed to a shaft and rotates in the stator, and is disposed in a hollow space formed in the rotor, and has an outer periphery that faces the rotating magnetic field of the stator. A magnet is attached to the magnet, and a magnet holding member rotatably supported on the shaft, the control device of the induction machine with a built-in magnet, comprising:
Determine whether the difference between the speed command value for rotating the rotor and the actual speed value of the rotor rotation is within a predetermined value,
When the difference is within a predetermined value , control to keep the magnetizing current constant,
When the difference exceeds a predetermined value, a magnetizing current control means for performing control for increasing the magnetizing current is provided.

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