JPH0956127A - Ac induction motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve efficiency without increasing the cost of equipment. SOLUTION: An AC induction motor is provided with a rotor 7 having a rotor winding which receives the action of a rotating magnetic field generated by a set of exciting windings 4, 5, 6 provided on a stator side to generate rotational torque. A plurality of permanent magnet members 11 to 16 disposed with intervals around the rotor 7 in accordance with the generation pattern of the rotating magnetic field and a magnetic-line-of-force control device 20 for generating in the space of an action an auxiliary rotating magnetic field synchronized with the rotating magnetic field by changing the number of magnetic lines of force with a phase shifted which is given from the permanent magnet member to the space 2A of an action are provided, and efficiency is improved by the auxiliary rotating magnetic field.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an AC induction motor, and more particularly to an AC induction motor capable of improving a power factor at a low load.

[0002]

2. Description of the Related Art A three-phase induction motor most widely used as an AC induction motor will be described as an example. The three-phase induction motor is a squirrel-cage driven by a rotating magnetic field generated by supplying a three-phase AC to a stator winding. Alternatively, the rotor of the wire-wound rotor is caused to generate an electromotive force due to electromagnetic induction, and a rotating torque is applied to the rotor by an electromagnetic force according to Fleming's left-hand rule generated between a short-circuit current and a magnetic flux flowing thereby.

As described above, in the induction motor, the magnetic flux generated by the primary winding of the stator cuts the secondary winding of the rotor,
It is similar to a transformer in that it induces a voltage due to an electromagnetic induction action in the secondary winding to flow a secondary current, and requires an exciting current. This exciting current is not effective energy.

[0004]

Since the induction motor is constructed as described above, the power factor is good at full load, but the power factor is remarkably reduced at light load, especially at no load. This is because the lighter the load, the greater the load on the power supply side with respect to the stator-side magnetizing current required to create the rotating magnetic field. Therefore, there is a problem that the reactive current increases due to the decrease in power factor.
To solve this problem, a method of using an AC commutator machine such as a Serbias phase advance machine to perform secondary excitation from an external power source on the secondary side has been conventionally used. However, in the case of this secondary excitation, the system becomes large, which causes another problem that the equipment cost rises.

It is an object of the present invention, therefore, to provide an AC induction motor whose efficiency can be improved without increasing equipment costs.

[0006]

The feature of the present invention for solving the above-mentioned problems is to provide a stator side in order to generate a rotating magnetic field in a predetermined working space by a set of externally applied multiphase alternating currents. AC induction motor including a set of excitation windings, and a rotor rotatably arranged in the working space, the rotor winding including a rotor winding for acting on the rotating magnetic field to generate a rotating torque. In, a plurality of permanent magnet members arranged at intervals around the rotor according to the generation pattern of the rotating magnetic field, and the number of magnetic force lines applied from the permanent magnet member to the working space are out of phase. And a magnetic field line control device for generating an auxiliary rotating magnetic field that is changed and synchronized with the rotating magnetic field in the working space.

For example, in the case of a three-phase AC induction motor, three exciting windings are provided on the stator side at intervals of 120 degrees, and exciting currents having different phases of 120 degrees are supplied from the three-phase AC power source to each exciting winding. By being passed through the excitation winding, a rotating magnetic field is generated in the working space where the rotor is provided. The rotor is provided with a cage or winding type rotor winding,
A voltage is induced in the rotor winding by the rotating magnetic field generated by the exciting winding, and the short-circuit current generated in the rotor winding thereby acts on the rotating magnetic field to generate a rotating torque in the rotor.

Since the auxiliary rotating magnetic field synchronized with the above-mentioned rotating magnetic field is generated by using the permanent magnet member, the N magnetic pole and the S magnetic field are used.
Plural sets of two permanent magnet members are provided so as to sandwich the rotor with the magnetic poles. In an example of a preferred embodiment showing the case of a three-phase AC induction motor, three sets of permanent magnet members are arranged so as to be offset by 120 degrees.

A magnetic force line control device is provided to change the number of magnetic force lines applied to the working space from these three sets of permanent magnet members by shifting the phases, thereby generating an auxiliary rotating magnetic field in synchronization with the rotating magnetic field.

The magnetic force line control device may be composed of, for example, a magnetic force line controller including an electromagnet provided for each permanent magnet member in order to control the magnetic force line from the permanent magnet member. In this case, it is desirable that one end of the electromagnet, which is the magnetic force line controller, is brought into close contact with one magnetic pole of the corresponding permanent magnet member and the other end is brought into close contact with the other magnetic pole of the corresponding permanent magnet member. In this configuration, for example, the direction and the magnitude of the exciting current to each electromagnet are changed in consideration of the change pattern of the predetermined rotating magnetic field, so that the number of magnetic force lines applied from the permanent magnet member to the action space is correlated with each other. It is possible to generate an auxiliary rotating magnetic field that rotates in synchronization with the rotating magnetic field as a whole.

The simplest means for ensuring this synchronization is to excite the stator-side excitation winding and the electromagnet with the same current from the three-phase AC power supply.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION An example of an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing the structure of a two-pole three-phase AC induction motor 1 according to the present invention. In FIG. 1, 2 is a frame, 3 is a stator core fixed to the frame 2 by a known means (not shown), and 4 to 6 are excitation windings provided on the stator core 3. 4 to 6 are arranged so as to be offset by 120 degrees in the circumferential direction of the stator core 3.

Voltages of R phase, S phase, and T phase of the three-phase AC power supply PW are applied to the respective ends of the excitation windings 4 to 6 through terminals U, V, W of the terminal plate TB. The other ends of the excitation windings 4 to 6 are commonly connected and grounded.

FIG. 2 shows the three-phase AC power source P in this way.
The waveforms of the exciting currents Ia, Ib, Ic supplied from W to the exciting windings 4, 5, 6 are shown. The exciting currents Ia, Ib, and Ic are alternating currents having a sinusoidal waveform whose phase is shifted by 120 degrees, and as a result, the action space 3A surrounded by the stator core 3 has its direction rotated with the passage of time. A magnetic field, that is, a rotating magnetic field Φ is formed.

In FIG. 3, the flow direction of each current to the windings 4, 5, 6 and the direction of the rotating magnetic field Φ at that time at each timing of times T1 to T7 shown in FIG. 2 are indicated by arrows. There is. The configuration itself for applying a three-phase AC voltage to the exciting windings 4, 5, and 6 to generate a rotating magnetic field as shown in FIG. 3 is known per se, and a detailed description thereof will be omitted.

Returning to FIG. 1, in the working space 3A of the three-phase AC induction motor 1, a rotor 7 fixed to a rotary shaft 8 rotatably supported at both ends of the frame 2.
Are provided coaxially with the stator core 3. The rotor 7 is provided with a squirrel cage conductor (not shown) as a rotor winding, and the rotating magnetic field Φ generated by passing the exciting current to the exciting windings 4, 5 and 6 as described above causes the action space 3A. That is, when applied to the stator 7, an electromotive force is generated in the rotor winding and a short-circuit current flows there. As a result, a rotating torque is generated in the rotor 7 due to the action between the magnetic field generated by the short-circuit current and the rotating magnetic field Φ, and the rotor 7 rotates.

In the three-phase AC induction motor 1, the auxiliary rotating magnetic field φ synchronized with the rotating magnetic field φ generated by passing the exciting currents Ia, Ib, Ic through the exciting windings 4, 5, 6 is utilized by using a permanent magnet. A plurality of permanent magnet members 11 to 16 are provided between the frame 2 and the stator core 3 in order to generate them in the action space 3A, and magnetic force line control for controlling magnetic force lines from these permanent magnet members 11 to 16. A device 20 is provided.

In the embodiment shown in FIG. 1, the permanent magnet member 11 is arranged so as to face the permanent magnet member 12 with the rotor 7 interposed therebetween, and the S magnetic pole of the permanent magnet member 11 and the permanent magnet member. The 12 N magnetic poles face each other, and thereby one pair of permanent magnets P1 is formed. Similarly, the permanent magnet member 13 and the permanent magnet member 14 are different permanent magnet pairs P2.
Forming a permanent magnet member 15 and a permanent magnet member 16
Form a further permanent magnet pair P3. Then, these three pairs of permanent magnets P1, P2, P3 are 12
They are placed 0 degrees apart.

In the structure shown in FIG. 1, salient pole pieces 11A to 16A curved along the outer peripheral surface 3B of the stator core 3 are provided at the respective inward ends of the permanent magnet members 11 to 16. As a result, a more uniform auxiliary rotating magnetic field φ can be formed with respect to the rotor 7. However, the formation of these salient pole pieces 11A to 16A can be omitted.

The magnetic force line controller 20 includes a permanent magnet member 11
To electromagnets 21 to 16 respectively provided corresponding to
It consists of 26. These electromagnets 21 to 26 function as magnetic force line controllers for controlling the magnetic force lines emitted from the corresponding permanent magnet members 11 to 16. As with the permanent magnets 11-16, these electromagnets 21-26
Also two opposing electromagnets 21 and 22, 23 and 24,
And 25 and 26 are paired respectively.

First, the electromagnets 21 and 22 will be described.
The electromagnet 21 is formed by winding a coil 21B around a U-shaped magnetic core 21A, one end of the magnetic core 21A is closely attached to the S magnetic pole end of the permanent magnet member 11 as shown in the figure, and the other end is an N magnetic pole of the permanent magnet member 11. Extremely close contact as shown. The magnetic core 21A and the permanent magnet member 11 are firmly connected to each other by an appropriate connecting member (not shown), so that the required close contact between the magnetic core 21A and the permanent magnet member 11 is maintained. There is.

The electromagnet 22 is also composed of a magnetic core 22A and a coil 22B wound around the magnetic core 22A, and is closely connected to the permanent magnet member 12 as in the case of the electromagnet 21.

As described above, a magnetic path formed by the magnetic core 21A of the electromagnet 21 is provided between the N magnetic pole end and the S magnetic pole end of the permanent magnet member 11. Therefore, no current is flowing through the coil 21B, or even if a current is flowing through the coil 21B, the current is applied so that each end of the magnetic core 21A has a magnetic polarity opposite to the corresponding magnetic polarity of the permanent magnet member 11. When flowing, almost all of the magnetic force lines from the permanent magnet member 11 return from the N magnetic pole to the S magnetic pole through the magnetic core 21A, and the magnetic force lines from the permanent magnet member 11 appear in the action space 3A. There is no going. On the contrary, coil 21B
When each end of the magnetic core 21A has the same magnetic pole property as the corresponding magnetic pole property of the permanent magnet member 11 due to the current flowing in the magnetic core 21, the magnetic flux from the permanent magnet member 11 cannot pass through the magnetic core 21A. The lines of magnetic force emitted from the N magnetic pole of the permanent magnet member 11 can pass through the working space 3A. That is, the electromagnet 21 provided corresponding to the permanent magnet member 11
Depending on the direction and magnitude of the current flowing through the coil 21B, it is possible to control the number of lines of magnetic force that exit the permanent magnet member 11 and reach the working space 3A.

On the other hand, by controlling the direction and magnitude of the current flowing through the electromagnet 22 combined with the permanent magnet member 12, the number of lines of magnetic force that exit the permanent magnet member 12 and reach the working space 3A is similarly set. Can be controlled.

By the way, the coil 21B and the coil 22B are connected in series, and the R-phase voltage of the three-phase AC power supply PW is applied to the coil 21B and the coil 22B as shown in FIG. Therefore, the control of the magnetic lines of force of the corresponding permanent magnet members 11 and 12 is executed in the same phase by the electromagnets 21 and 22. Therefore, when the exciting current Ia shown in FIG. 2 increases with a positive value, the permanent magnet member 1 is correspondingly increased.
From the N magnetic pole 2 through the working space 3A to the permanent magnet member 11
The number of magnetic lines of force reaching the S magnetic pole of increases and the exciting current Ia
When is a negative value, the number of magnetic force lines reaching the S magnetic pole of the permanent magnet member 11 from the N magnetic pole of the permanent magnet member 12 through the action space 3A becomes almost zero.

That is, at the timing of time T1 in FIG. 2, the magnetic field generated in the working space 3A by the pair of permanent magnet members 11 and 12 is controlled by the electromagnets 21 and 22 to be the maximum, and the rotating magnetic field Φ (FIG. An auxiliary magnetic field by the permanent magnet members 11 and 12 is superimposed on (a) of 3.

Although the magnetic force line control for one permanent magnet pair P1 has been described above, the magnetic force line control for the other permanent magnet pairs P2, P3 is similarly executed using the electromagnets 23-26. That is, the U-shaped magnetic cores 23A to 26A of the electromagnets 23 to 26 correspond to the corresponding permanent magnet members 13 to 16 respectively.
Similarly, it is closely attached and connected. The coil 23B and the coil 24B, which are wound around the coil 23B and the coil 24B, are connected in series and a S-phase voltage is applied as shown in the figure, and the coil 25B and the coil 26B are connected in series and a T-phase voltage is applied. Has been done.

Therefore, the strength of the auxiliary magnetic field given to the working space 3A by the permanent magnet pair P2 is the exciting current Ib.
Of the auxiliary magnetic field, which changes in accordance with the change of the magnetic field, and is applied to the working space 3A by the permanent magnet pair P3.
It will change according to the change of.

From the above description, since the auxiliary magnetic field generated in the working space 3A by the permanent magnet pairs P1 to P3 is a combined magnetic field of these, the currents Ia and Ia which are 120 degrees out of phase with each other.
For the same reason that the rotating magnetic field Φ is formed by the excitation by b and Ic, the magnetic field lines of the permanent magnets 11 to 16 are controlled as described above in response to the current flowing through the corresponding electromagnets.
An auxiliary rotating magnetic field φ synchronized with the rotating magnetic field Φ is formed in the working space 3A.

As a result, the rotor 7 has an auxiliary rotating magnetic field φ.
A combined rotating magnetic field Φ + φ, which is formed by superimposing an auxiliary rotating magnetic field φ synchronized with this, acts on the rotor winding of the rotor, and a rotating torque is generated in the rotor 7. . In order to completely synchronize the two, each exciting current supplied to the exciting windings 4 to 6 and the electromagnets 21 to
It is necessary that the phase with respect to the current supplied to 26 be set to a predetermined value. Therefore, a phase adjusting means for adjusting the phase difference may be provided so that the rotating magnetic field Φ and the auxiliary rotating magnetic field φ can be more completely synchronized.

By the way, the magnetic flux number Q which determines the strength of each electromagnet acting as a magnetic force line controller is proportional to the number of turns N of the coil and the value of the current I flowing therethrough, and therefore becomes Q∝I × N. . Since the maximum value of the number of magnetic fluxes Q required for controlling the lines of magnetic force is a predetermined constant value, if the number of turns N of the coil of the electromagnet is increased, the value of the current value I for excitation will be small. By the way, since the DC supply energy to each electromagnet is V × I when the applied voltage is V, the energy required for controlling the lines of magnetic force can be reduced by reducing the value of I. In this way, the permanent magnet is used to generate the auxiliary rotating magnetic field φ with a small energy in the working space 3A by superimposing the auxiliary rotating magnetic field φ on the rotating magnetic field Φ, whereby the efficiency of the three-phase induction motor 1 is improved, especially when the load is low. The efficiency can be improved significantly. In addition, although the case where the normal electromagnet is used has been described in the above embodiment, the efficiency can be further improved by using the superconducting magnet as the electromagnets 21 to 26.

In the configuration shown in FIG. 1, the excitation windings 4, 5,
Although the same currents as the currents Ia, Ib, and Ic for exciting 6 are used as the currents for exciting the coils 21B to 26B of the electromagnets 21 to 26, the currents for exciting the electromagnets 21 to 26 are, for example, It is obtained by using another three-phase AC power source or by extracting three sine wave signals having different phases by 120 degrees from an appropriate sine wave generating circuit, and the currents thus produced are called currents Ia, Ib, Ic. It may be configured to synchronize with an appropriate synchronizing circuit and supply to the coils 21B to 26B of the electromagnets 21 to 26.

[0034]

According to the present invention, a rotating magnetic field is generated by the exciting coil provided on the side of the stator, and the magnetic force lines from the permanent magnet member are controlled by the magnetic force line controller to synchronize with the rotating magnetic field. The auxiliary rotating magnetic field is generated efficiently with a small amount of energy, and the combined rotating magnetic field is applied to the rotor windings to obtain the rotating torque of the rotor. Therefore, the power factor is reduced especially at low load. The efficiency of the case can be significantly improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an example of an embodiment of an AC induction motor according to the present invention.

FIG. 2 is a current waveform diagram showing a waveform of a current for excitation shown in FIG.

FIG. 3 is an explanatory diagram for explaining a temporal change in a direction of a rotating magnetic field generated in an action space by the excitation winding of FIG. 1 based on a current waveform diagram shown in FIG.

[Explanation of symbols]

 1 3 Phase Induction Motor 3 Stator Core 3A Working Space 4, 5, 6 Excitation Winding 7 Rotor 11 to 16 Permanent Magnet Member 20 Magnetic Field Line Control Device 21 to 26 Electromagnets Ia, Ib, Ic Current PW 3 Phase AC Power Supply

Claims (1)

[Claims] 1. A set of exciting windings provided on the stator side for generating a rotating magnetic field in a predetermined working space by a set of multi-phase alternating currents applied from the outside, and an exciting winding acting on the rotating magnetic field. In an AC induction motor, comprising a rotor winding for generating a rotation torque, and a rotor rotatably arranged in the working space, in the vicinity of the rotor according to a generation pattern of the rotating magnetic field. A plurality of permanent magnet members arranged at intervals and an auxiliary rotating magnetic field synchronized with the rotating magnetic field in the working space by changing the number of magnetic force lines applied from the permanent magnet member to the working space by shifting the phase. An alternating current induction motor, comprising: a magnetic force line control device for generating the magnetic force line.