JPS59149786A - Modulation drive type ac motor - Google Patents

Abstract

PURPOSE:To improve the rotating characteristic, responsiveness and to enable to synchronously operate in high efficiency by exciting a stator winding with a waveform amplitude-modulated for a carrier voltage. CONSTITUTION:Modulated voltages 5, 6 are respectively applied to exciting windings 1, 2. In this case, the instantaneous value of the rotary magnetic field is not constant, but becomes alternating magnetic field of the type continued in carrier frequency, and rotated by the modulation frequency. The secondary winding 7 coupled electromagnetically to the windings 1, 2 is provided at the rotor side, and an induced voltage is generated in a shortcircuit of the secondary winding to flow a shortcircuiting current. This shortcircuiting current has carrier frequency, electromagnetic force is generated to the alternating current to obtain a rotary force.

Description

[Detailed Description of the Invention] A motor that performs automatic tracking control of mechanical displacement and speed is a so-called servo motor, and there are two types: a DC motor and a male current motor. The required performance is that the variable speed range is wide and has coordination. In general, the coordination of electric motors is inferior to that of hydraulic or pneumatic control, but with recent advances in electronic control technology, they are becoming increasingly popular. However, in DC motors, the commutator is a drawback in maintenance, so there are so-called plastic motors in which the commutator is replaced with a semiconductor electronic switch.

In this case, since the DC field is provided on the rotor side, the principle is that a semiconductor electronic switch circuit is added to the stator excitation winding of the synchronous motor. On the other hand, in an induction motor, a secondary winding with electromagnetic coupling is provided on the rotor side to the excitation winding on the stator side in the case of a synchronous motor, so the relationship between both windings corresponds to a transformer. The structural principles are different. However, in any electric motor, the electromagnetic attractive force acting between the magnetic poles of the stator and rotor becomes rotational force, and in a DC motor, the armature
The rotational speed of the rotating magnetic field generated in the stator of a synchronous motor and the rotor of an induction motor changes to adjust the number of rotations. This can be said to be that the rotational speed is controlled by changing the frequency of the alternating current voltage that generates the rotating magnetic field. Therefore, a common characteristic is that when the rotational speed is extremely low, such as during startup, the frequency of the alternating current voltage decreases, so that the magnetizing current increases abnormally. Further, if the abnormal magnetizing current is limited, there is a drawback that insufficient rotational force occurs and rotation becomes unstable. To avoid this problem, it is necessary to use a speed-increasing gear to increase the average rotational speed of the servomotor, but this does not improve the rotational force characteristics at low speeds.

The purpose of the present invention is to eliminate the above-mentioned defects in conventional electric motors, and it relates to the development of a new AC electric motor that is characterized by excellent rotational force characteristics, especially at startup and at low rotational speeds. . The basic principle is a way to eliminate the negative influence of conventional electric motors on rotational force due to frequency changes in the alternating current voltage that generates the rotating magnetic field, and this is made possible by introducing a modulated carrier wave, which is common knowledge in communication technology. . Therefore, both in structure and operating principle, it is different from conventional AC electric motors. FIG. 1 is a schematic diagram of each winding arrangement shown in a simple embodiment for specifically explaining the same. In other words, the winding axes cross each other perpendicularly.
When a set of excitation windings (11 (21) are excited with an alternating current voltage of the same frequency, the direction of the combined magnetic field changes depending on the magnitude of each excitation voltage. Assuming that the electrical angle formed by the direction of the magnetic field generated by the winding (1) is θ, if the instantaneous voltage values of both windings are changed according to the image θ and mθ, the combined magnetic field becomes a rotating magnetic field. The waveforms shown by dotted lines (3) and (4) in Figure 2 correspond to the excitation voltage in this case, and there is a phase difference of 90° between them.
It is assumed that 5) and (6) are waveforms obtained by amplitude modulating carrier voltages having the same phase and frequency, and that their peak values match the instantaneous values of dotted lines (3) and (4), respectively. In the present invention, modulated wave voltages (5) and (6) shown in Fig. 2 are added to the excitation winding tl) +21 shown in Fig. 1, respectively, but the instantaneous value of the rotating magnetic field is not constant, This results in an alternating magnetic field that is interrupted by the frequency and is rotated at the modulation frequency. Therefore, we will call it an alternating rotating magnetic field and a motor using this field will be called a modulation drive type motor. Even if the peak value of the magnetizing current of both windings +11 and +21 changes according to (51(f3)), the peak value of the alternating rotating magnetic field, which is the composite magnetic field, is always constant.In the case of Fig. 1, the exciting winding (1) +
21 is on the stator side, and if a secondary winding (7) electromagnetically coupled to this is provided on the rotor side, an induced voltage will be generated in the short circuit of the secondary winding and a short circuit current will flow. This short circuit current has a carrier frequency and generates an electromagnetic force between it and the alternating magnetic field, resulting in a rotational force. However, the magnitude of the induced voltage differs depending on the relative position of both windings, and it does not occur in the secondary winding (where the axis of force is perpendicular to the direction of the alternating magnetic field, but it is maximum in the position where the axis of force is parallel to the direction of the alternating magnetic field). In other words, the rotational force has the property of trying to occupy a stable position where short circuit current no longer flows.Also, the relationship between the excitation winding and the secondary winding is equivalent to that of a transformer, and a strong rotational force is generated due to close electromagnetic coupling. This can be confirmed by the method shown in Figure 3, but in the cross-sectional view shown in Figure 3, the iron core closed magnetic path (
A space is provided in the center of the winding 8), and a rotatable short-circuit winding 01) whose rotating shaft is supported by a bearing (9) is inserted into this space. If the two excitation windings +121 (131) applied to the iron core magnetic path (8) are connected in series and excited with an alternating current voltage, the alternating magnetic field generated in the air gap will cause a current to flow through a short circuit and a rotational force will be generated. It has been experimentally confirmed that this rotational force rotates the short-circuit winding (11) to a stable position where the short-circuit current decreases.Furthermore, the short-circuit winding (11) is forcibly rotated from the stable position by an external force. It has also been confirmed through experiments that no matter which direction it is deflected, it has a restoring force in the direction that occupies a stable position.Since it is an alternating rotating magnetic field that rotates the alternating magnetic field in this case, as shown in Figure 1. It is very clear that the secondary winding in the case of (Since it passes through the center of force, the force that always maintains a stable position even if the direction of the alternating magnetic field changes is used as the synchronous rotational force of the rotor.

In this case, the mechanical load on the rotor governs the angle of deviation of the secondary winding (7) from its stable position, and thus the value of the short-circuit current, and also changes the load current of the excitation winding (11 [2+). Yes, as the load increases, the short circuit current naturally increases, increasing the rotational force to balance the load, but this is not directly related to the rotation speed.

Therefore, the lack of rotational force of the starting board at low rotational speeds, which is a defect of conventional electric motors, is thereby eliminated, and this is also an excellent feature of the present invention. However, although the deviation angle increases with load, it can be reduced by increasing the number of poles of the excitation winding. Next, the influence of frequency on the magnetizing current of the excitation winding is determined by the carrier frequency and not by the modulation frequency. For example, in Figure 2, even if the change in the modulation waveform is stopped at an arbitrary moment and the carrier waveform becomes a continuous waveform with a constant peak value,
The magnetizing current does not increase abnormally. Furthermore, since the effect of the short-circuit current is not lost, rotational force is present, and the motor can be stopped instantaneously or operated intermittently. This is different from conventional electric motors, and makes it possible to eliminate defects that could hardly be expected with this method.

In short, a modulation drive motor has the synchronous drive characteristics of a synchronous motor, but since there is no DC excitation winding or permanent magnet on the rotor side, it is structurally closer to a hysteresis motor. The rotor of a hysteresis motor consists solely of a cylindrical magnetic material, which is magnetized by a rotating magnetic field and operates synchronously. In this rotor, the magnetic field is created by the excitation winding, but in the rotor of a modulation drive motor, the alternating magnetic field is likewise created by the excitation winding. Even if there is a shorted winding, the magnetomotive force generated by the current is canceled out by the load current of the excitation winding, just as in the case of a transformer, so there is no change in the alternating magnetic field, and in this sense, the shorted winding It has nothing to do with existence. However, due to the principle of FIG. 3, a strong synchronizing force is added because of the balancing effect that regulates the position of the shorted winding with respect to the direction of the alternating magnetic field. Alternatively, a modulation drive type motor can be considered to be a hysteresis motor that is given a strong synchronizing force using a type of AC electromagnet. In particular, if the carrier frequency is made to match the frequency of the alternating current voltage applied to the excitation winding of the hysteresis motor, the rotational speed naturally tends to drop significantly. However, it can be said that this is more suitable for direct drive type servo motors that often use speed increasing gears. Since gear wear is unavoidable in servo motors,
Recently, there are signs that a direct drive system other than this is being adopted. In order to match the rotation speed in both cases, it is only necessary to relatively increase the carrier frequency, which is not easy, but the carrier power source is a single-phase power source, which makes the equipment relatively simple. . In the case of FIG. 1, a rotating magnetic field was obtained with two sets of windings, but the principle of the present invention is the same even when generating a rotating magnetic field using six-phase or multi-phase excitation windings. Structurally, a short-circuited secondary winding is used to avoid introducing current into the rotor from the outside, but the explanation so far has focused exclusively on this case. However, in reality, it is also possible to load an appropriate impedance to the secondary winding or intervene with a rectifier to compensate for the power factor and rotational force. For example, there is a method in which a rectifier is inserted in series in a short circuit, and the electromagnetic force between the DC component included in the current and the DC magnetic field component of the alternating magnetic field is simultaneously used as a conventional synchronous motor.

Next, the responsiveness of a servo motor varies greatly depending on the inertia and rotational speed of the rotor, and these must be reduced. −
To reduce inertia by 1, it is necessary to reduce the size and weight.

It is common knowledge that conventional electric motors can be made smaller and lighter by increasing the power frequency, but at the same time the rotational speed increases and the inertial energy accumulated by the servo motor impedes coordination, so this is not practical. will not be adopted. On the other hand, in a modulation drive type electric motor, as mentioned above, the increase in carrier frequency is unrelated to the number of revolutions, so it has the advantage that the frequency can be increased arbitrarily to make the motor smaller and lighter. However, the impedance drop increases as the frequency increases, as in the case of high-frequency transformers, and since the frequency can be increased without limit, tf
It's so cool. In some cases, it may be necessary to load the short-circuit secondary winding with a suitable impedance to take advantage of the resonance effect while preventing the short-circuit current from decreasing. Furthermore, if a high-frequency powder-molded magnetic material is used in the magnetic circuit, the weight can be reduced due to the difference in specific gravity from the laminated silicon steel plates of conventional motors. For example, ferrite-based magnetic materials are expected to reduce the weight of electric motors by more than 30%. In addition, the molded iron core simplifies the assembly of the electric motor, which indirectly enables economical production of electric motors and facilitates robot production. In particular, since the average rotational speed is low in the direct drive system, the rotational inertia energy can be significantly reduced by increasing the carrier frequency, making use of the synergistic effect of reducing the size and weight of the iron core and reducing the specific gravity of the compacted magnetic material. This makes it possible to create an ideal servo motor. This is not possible with conventional electric motors, but it is a feature that can only be expected due to the rotational force characteristics of modulation drive type electric motors and the possibility of making them smaller and lighter. It must be added that the operating principle of the present invention is that the waveform distortion is low and the loss is low, so the high efficiency performance helps in this respect.

In conclusion, modulation drive motors have excellent torque characteristics, improved coordination, high efficiency, and synchronous operation, making them the most suitable for digital control. This indirectly has the effect of facilitating the manufacture of electronic devices for power supplies as well as amplifiers. In addition, since the structure is simple and does not require any mechanical conductive parts such as commutators or slip rings, it has the advantage of improving reliability and is not limited by the capacity of the motor. In particular, it can be said that it is of great significance to provide a theoretical basis that can fundamentally eliminate the defects of conventional electric motors in terms of its operating principle.

Therefore, it can be pointed out that there are great implementation effects and expectations for improving the technical level of general control equipment.

[Brief explanation of the drawing]

Fig. 1 shows an embodiment of the present invention shown in a simple diagram of the winding arrangement, and Fig. 2 shows the voltages of two sets of excitation windings that intersect perpendicularly to each other, which are necessary to generate an alternating rotating magnetic field. The modulation waveform of FIG. 3 is a reference diagram for explaining the rotational force that the short-circuited secondary winding that is electromagnetically coupled to the excitation winding receives from the alternating magnetic field, flN21...・・・Stator side excitation winding, f3) (4) ・・・・・・・・・・・・・・・AC voltage waveform required for a conventional AC motor to generate a rotating magnetic field, (
5)(6)・・・・・・・・・The present invention uses the AC voltage waveform and (force) necessary for generating an alternating rotating magnetic field.
...Rotor side short-circuited secondary winding having electromagnetic coupling to the excitation winding of the present invention, (8) ...... Iron core magnetic path in the reference diagram, (9) ( 101・・・・・・・・・・・・
...Bearing that supports the rotating shaft in the air gap of the iron core magnetic path, (I9・
・・・・・・・・・・・・・・・ Short-circuited winding directly connected to the rotating shaft, Q2 +l dry ・・・・・・・・・・・・
・・・・・・Excitation winding that excites the iron core magnetic path. Patent Applicant Takashi Take Procedural Amendment (Method) March 16, 1981 1, Case Description 1982 Patent Application No. 188838
No. 2, Title of the invention Modulation drive type AC motor ・3,
Phone number of the person making the amendment: (03) 4] 4-5080 4. Date of amendment order: February 2, 1980 5. Date of sending of amendment order: February 22, 1980 6. Target of amendment
Brief explanation of the drawings 7, ``Procedures to explain rotational force'' in the second line from the top of page 13 of the specification of the contents of the amendment Amendment document January 2nd, 1980 1, Indication of the case 1982 patent Application No. 188838 2, Name of the invention Modulation drive type AC motor 3, Relationship with the amended case Patent applicant Seta Gayakudaita (Address) 5-20-13 Daita, Setagaya-ku, Tokyo Telephone (
03) (414) 5080 4. Subject of amendment Specification correction Part 1. Correct rlJ in line 14 of page 1 to “follow” 2. Page 2 3
Corrected "vertical" to "subordinate" in line 3. Corrected "correspondence of" in line 7 of page 2 to "correspondence of" 4. Delete "therefore" in line 6 of page 3. 5. 6. Corrected "Magnetization because the wave number of AC voltage decreases" in lines 7 to 8 on page 3 to [starts up if the power supply voltage remains constant] 6. Delete "magnetization" on line 9 on page 3, line 11 on page 73 8. Insert “common phase” after “same frequency” in line 7 on page 4. 9. Add “alternate magnetic field” in line 2 on page 5. Insert "The alternating current component is" in front] 0.5, line 14, "The size of is different depending on the relative position of both windings" is changed to "ha" 11.6, line 16, "is" Corrected “vertical” to “subordinate” 12, 9
Page 3, line 1 hysteresis" was corrected to "synchronization" 13. Page 100, line 4, "DC magnetic field component of alternating magnetic field" was changed to "
Corrected to "Rotating magnetic field generated by modulated wave components included in Figure 2 (5) and (6)" 14. On page 100, line 8, "rotational speed" is replaced with "rotational force", and "these" are replaced with "inertia", respectively. Correction 15. Delete “possibility” on page 11, line 18 16.13
Delete “Reference figure” on page 18 line (above) Procedural amendment to the Commissioner of the Japan Patent Office 1, Indication of case: Patent Application No. 188838 of 1982, 2, Title of invention Modulation drive type AC motor 3, Amended Relationship with the patent applicant's case 4. Date of amendment order: February 24, 1980 (Delivery date: February 28, 1980) 5. Subject of amendment: Procedural amendment filed on January 20, 1980 Correction target column 6
Based on the instruction for amending the content of the amendment, paragraphs 1 and 16 of the corrections attached to the procedural amendment submitted on January 20, 1980, have been amended as shown in the attached document. No change). 1.
, l', i5G, 3.28 Attachment 1゜2, Claims (1) An electromagnetic coil is connected to the stator-side excitation winding and the excitation winding, which are excited by a predetermined frequency carrier AC voltage that can be amplitude modulated at any period. The excitation winding arrangement and transport necessary to form a rotating magnetic field at the modulation frequency of two sets of magnetic fields generated in the magnetic circuit with a carrier frequency and a modulation frequency. Equipped with a secondary winding arrangement necessary to flow a short-circuit current by the electromagnetic induction effect of the frequency, the rotor follows the rotating magnetic field synchronously while utilizing the electromagnetic force generated between the short-circuit current and the field. A modulation drive type AC motor characterized by adjusting the rotation speed by changing the modulation frequency. (2) A motor structure that makes it possible to reduce the size and weight by increasing the frequency by utilizing the characteristic that the carrier frequency in a modulation drive type AC motor does not affect the rotation speed. 16″
Remove ``reference figure'' on page 13, line 8.

Claims (2)

[Claims] (1) Consisting of a stator-side excitation winding excited with a predetermined frequency carrier AC voltage whose amplitude can be modulated at any period, and a rotor-side short-circuited secondary winding having electromagnetic coupling to the excitation winding, the carrier frequency and Among the two sets of fields generated in the magnetic circuit at the modulation frequency, the excitation winding arrangement is necessary to form a rotating magnetic field at the modulation frequency, and the secondary winding is necessary to flow a short-circuit current through the electromagnetic induction effect of the carrier frequency. The rotor is made to follow the rotating magnetic field synchronously by using the electromagnetic force generated between the short-circuit current and the field, and the number of rotations is adjusted by changing the modulation frequency. A modulation-driven AC motor with (2) A motor structure that makes it possible to reduce the size and weight by increasing the frequency by utilizing the characteristic that the carrier frequency in a modulation drive type AC motor does not affect the rotation speed.