JPS6149901B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a method for magnetizing the rotor of a permanent magnet synchronous motor, and particularly to a method for magnetizing a rotor of a permanent magnet synchronous motor equipped with a squirrel cage winding for self-starting. This invention relates to a rotor magnetization method.

[Background of the invention]

Many synchronous motors, such as those used in the winding systems of spinning factories, are operated in parallel at the same speed.
Therefore, the electric motor itself is required to be capable of self-starting, and to be capable of synchronous pull-in with load inertia and a load on its back.

Conventionally, this type of motor is started as an induction motor, and after synchronous pull-in, is operated as a synchronous motor using the magnetic force of a permanent magnet. Therefore, the electric motor has characteristics of both an induction motor and a synchronous motor. For this reason, in this type of electric motor, the stator is not particularly different from that of a normal electric motor, but the rotor has a special structure, and various structures have been proposed depending on the number of poles, magnet material, etc.

FIGS. 1 and 2 show an example thereof.

In these figures, reference numeral 1 denotes a rotating shaft, and both ends thereof are rotatably supported by bearings provided on the outer frame of a stator (not shown). This rotating shaft 1
A laminated rotor core 2 is press-fitted into the rotor core 2, and a large number of squirrel cage conductors 3 are provided on the outer periphery of the rotor core 2. Both ends of the squirrel cage conductors 3 are short-circuited by end rings 4A and 4B. A squirrel cage winding forming a closed circuit is formed.

Furthermore, four permanent magnets 5 are provided on the inner peripheral side of the rotor core 2 at intervals in the circumferential direction. These permanent magnets 5 are magnetized in the circumferential direction so that sides corresponding to the circumferential direction of adjacent permanent magnets have the same polarity. The spaces on both sides of the permanent magnet 5 in the radial direction are filled with aluminum 6, which is the same material as the cage-shaped conductor 3, and prevents the alternating current magnetic field from acting on the permanent magnet 5.

The thin iron plates constituting the rotor core 2 are the rotating shaft 1,
Since the rotor is punched in a shape with parts corresponding to the squirrel cage conductor 3, the permanent magnet 5, and the aluminum portion 6 on the side of the magnet removed, the rotor as a whole does not have sufficient strength against centrifugal force. Therefore, as a reinforcing member against this centrifugal force, a reinforcing pin 7 is inserted through the center of the magnetic pole, and both ends of this reinforcing pin are supported by end plates 8A and 8B.

In the rotor having this structure, either alnico or ferrite can be used as the material for the permanent magnets 5. Further, the magnetic flux of the permanent magnet 5 leaks between the poles due to the innermost circumferential part 9 and the outer circumferential part 10 of the rotor core 2, but by providing these connecting short circuit parts 9 and 10, the rotor core 2 is configured. Even if the parts corresponding to the rotating shaft 1, squirrel cage conductor 3, permanent magnet 5, etc. are removed from the thin iron plate, it can still be punched out as a single connected plate, making it easy to stack the thin iron plates.

By the way, in this kind of permanent magnet type synchronous motor,
The synchronous pull-in torque is determined by the gradient of torque at a speed near the synchronous speed of the induction motor and the magnitude of the escape torque of the synchronous motor. The larger the torque, the greater the retracting torque. and,
This torque gradient is determined by the size of the squirrel cage conductor. Therefore, it is preferable that the size of the squirrel cage conductor of the rotor is as large as possible.

However, in the conventional structure, for example, in the structure shown in FIG. To become
The cross-sectional area perpendicular to the magnetization direction becomes small, and a sufficient amount of magnetic flux cannot be obtained.

Also, a rotor in which permanent magnets are magnetized in the radial direction has been proposed, but in this case, the angle occupied by the circumferential width of the permanent magnet is within the range of 2π/P, so the circumferential width of the permanent magnet is In order to increase the size and increase the cross-sectional area perpendicular to the magnetization direction, the permanent magnet must be placed as close to the outer circumference of the rotor core as possible.
This ultimately results in a reduction in the thickness of the core back that can be used as an induction motor, that is, the iron core portion between the permanent magnet and the squirrel cage conductor, which leads to undesirable consequences for the motor, such as an increase in starting current.

Therefore, a permanent magnet type synchronous motor as shown in FIG. 3 has been proposed which eliminates these drawbacks and has good starting characteristics and synchronous operation characteristics (see, for example, Japanese Utility Model Application Publication No. 49-26009). In Figure 3,
The figure shows a six-pole rotor structure, and the same reference numerals as in FIGS. 1 and 2 represent the same or equivalent parts.

A laminated rotor core 2 is press-fitted onto the rotating shaft 1, and a large number of squirrel cage conductors 3 are provided on the outer periphery of the rotor core 2, as in the prior art example.

In the part near the inner circumference of the rotor core 2, there is an angle that equally divides the circumference by the number of poles P (P = 6 in this case).
Arc-shaped permanent magnets 11 having an angle larger than 2π/P=60 degrees are provided in the same number as the number of pole pairs (P/2=3). The magnetization direction of these permanent magnets 11 is the radial direction, which is the same direction. That is, the outer circumferential side is the N pole, and the inner circumferential side is the S pole.

Between the poles of the rotor core 2, inter-pole slits 12 are formed. These inter-pole slits 12 extend from both ends of each permanent magnet 11 to near the inside of the squirrel-cage conductor 3, and at the outer end near the squirrel-cage conductor 3 are located at positions that divide the circumference into approximately P equal parts. The poles are arranged so that they gradually widen as they go inward.

Here, the width of the inner circumference side iron core part 13 of the permanent magnet 11 is set to such a size that magnetic saturation does not occur even if half the magnetic flux of the permanent magnet 11 passes through, and the width of the iron core part 14 between adjacent permanent magnets 11 is set to a size that does not cause magnetic saturation even if half the magnetic flux of the permanent magnet 11 passes through. It is necessary to set each dimension to such a size that magnetic saturation does not occur even if all 12 magnetic fluxes pass through.

In addition, from the stator side (not shown), the S pole of the rotor,
In other words, the magnetic flux entering the image pole is transferred to the iron core 15,
14, it reaches the permanent magnet 11, from there it reaches the N pole, and returns to the stator side again.

In the rotor configured as described above, the circumferential width of the permanent magnets 11 can be made larger than 2π/P, so even if the permanent magnets 11 are arranged on the inner circumferential side, they can be arranged on the outer circumferential side. It is possible to obtain a cross-sectional area perpendicular to the magnetization direction that is substantially similar to . Furthermore, by arranging the permanent magnets 11 as close to the inner circumferential side as possible, the core back can be thick enough to be used as an induction motor.
Since the current at the time of starting can be reduced and the thickness of the squirrel cage conductor can be made sufficiently large, the torque gradient of the induction motor can be increased and the synchronous pull-in torque can also be increased.

By the way, when manufacturing such a rotor, if pre-magnetized permanent magnets are used, the magnetic properties of the permanent magnets may deteriorate due to the heat generated when die-casting the cage windings, or the cage windings may deteriorate. After the shape winding is formed, the iron plates that make up the core are integrated and do not move relative to each other, making it extremely difficult to insert a permanent magnet into the core.
It is desirable to magnetize the permanent magnets after assembling the rotor. However, since there is an image pole as mentioned above, each permanent magnet must be magnetized in the same direction (in the radial direction), but if you try to magnetize one permanent magnet, the polarity of the other permanent magnet will change. Since the permanent magnets are reversed, it is difficult to magnetize all the permanent magnets in the same direction after the rotor is assembled.

[Purpose of the invention]

An object of the present invention is to provide a magnetization method that can easily magnetize the rotor of a hexapole permanent magnet type synchronous motor having image poles of this type after assembly.

[Summary of the invention]

In order to achieve this object, the present invention uses a rare earth magnet with high demagnetization resistance as the magnet material of the permanent magnet member, and also uses three permanent One of the magnet members is made to correspond to the other magnetic pole part with a large polar arc, and the magnetizing coil wound around the magnetizing iron core is energized to create a large magnetic field in one permanent magnet member. The present invention is characterized in that the magnetization step of applying a small magnetic field to each of the other two permanent magnet members is sequentially performed for each of the three permanent magnet members.

[Embodiments of the invention]

Hereinafter, a method of magnetizing a rotor according to an embodiment of the present invention will be explained with reference to FIG.

Regarding FIG. 4, 15 is a magnetizing core, 15a,
Reference numeral 15b indicates the magnetic pole portions, one magnetic pole portion 15a with a smaller polar arc has an angle of approximately 2π/P (in this case π/3), and the other magnetic pole portion 15b with a larger polar arc has an angle of approximately (2π/P). It has an angle of ×3 (π in this case). A magnetizing coil 16 is wound around the magnetizing iron core 15, and is connected to a DC power source 18 via a switch 17, thereby forming a magnetizing device.

To magnetize the rotor using this magnetizing device,
As shown in the figure, one of the magnetic poles having the permanent magnet 11 of the rotor is attached to one magnetic pole part 15a of the magnetizing core 15 having a small polar arc, and a permanent magnet is attached to the other magnetic pole part 15b having a large polar arc. The parts extending from the other magnetic pole having the permanent magnet 11 to the further other magnetic pole having the permanent magnet 11 are made to face each other, and the switch 17 is closed.
The magnetizing coil 16 is energized. In this way, a sufficiently large magnetic field is applied to the magnetic pole side of the rotor facing the one magnetic pole part 15a with a small polar arc, and a sufficiently large magnetic field is applied to the magnetic pole side of the rotor facing the other magnetic pole part 15b with a large polar arc. Since a smaller magnetic field will be applied compared to this, the rotor is rotated and the permanent magnet 1
By doing this for each magnetic pole having 1, that is, three times in total, all the permanent magnets 11 can be magnetized.

At this time, the magnetizing magnetic field is large, that is, the magnetic pole part 15
No matter what polarity the permanent magnet 11 on the side facing a is magnetized, it is magnetized in the direction of the magnetizing magnetic field, so there is no problem. Permanent magnet 11 on the opposite side
However, if the permanent magnet 11 is magnetized in the direction of the magnetizing magnetic field, problems will occur.
It is necessary to use a material having a larger demagnetizing strength than the small magnetizing magnetic field of 5b.

When magnetized using a magnetization device in which the magnetic field of the magnetic pole part 15a is approximately 25 kOe and the magnetic field of the magnetic pole part 15b is approximately 12.5 kOe, the magnetic pole part 15a is strongly magnetized by the large magnetic field of approximately 25 kOe. Permanent magnets are approximately
Since the magnetic force is maintained up to a demagnetizing field of 25 kOe, the polarity will not be reversed even if the magnetic pole portion 15b receives a small demagnetizing field of approximately 12.5 kOe. Moreover, the magnetic pole part 15b
The permanent magnet, which is weakly magnetized by a small magnetic field of approximately 12.5 kOe, is reversed in polarity and magnetized to a desired polarity when subjected to a large demagnetizing field of approximately 25 kOe at the magnetic pole portion 15a.

Therefore, in this example, as a magnet material having such properties, a rare earth magnet such as Samarium Cobalt SmCo is used, and its residual magnetic flux density Br is 8 kG, resistance force Hc is 7.95 kOe, and iHc is
25kOe material is used.

In addition, in this example, as shown in FIG.
Although we have described the case in which a single arc-shaped permanent magnet is used as a permanent magnet member to magnetize a rotor, it is also possible to use a plurality of plate-shaped permanent magnets 19, which are easy to manufacture, as shown in Fig. 5. It can also be applied to the magnetization of a rotor that is

[Effects of the Invention] As explained above, according to the present invention, the rotor of a six-pole permanent magnet synchronous motor having image poles with excellent starting characteristics and synchronous operation characteristics can be easily attached after assembly. Can be magnetized. As a result, the magnetic properties of the permanent magnet member, which is previously magnetized by the heat during die-casting of the squirrel cage winding, are prevented from deteriorating, and the work of inserting the permanent magnet member into the iron core is also simplified. It becomes easier.

[Brief explanation of the drawing]

Fig. 1 is a vertical side view showing an example of a rotor of a conventional permanent magnet type synchronous motor, Fig. 2 is a sectional view taken along line A-A in Fig. 1, and Fig. 3 is an example in which the magnetization method of the present invention is applied. A vertical side view showing an example of a rotor of a permanent magnet type synchronous motor, FIG. 4 is a schematic configuration diagram showing a magnetizing device for carrying out the magnetizing method of the present invention, and FIG. 5 is a schematic diagram showing a magnetizing device to which the present invention is applied. FIG. 7 is a longitudinal sectional side view showing another example of the rotor of the permanent magnet type synchronous motor. 1... Rotating shaft, 2... Rotor core, 3... Squirrel cage conductor, 11, 19... Permanent magnet, 15... Iron core for magnetization, 15a, 15b... Magnetic pole part, 16... For magnetization coil.

Claims (1)

[Claims] 1. A rotating shaft, a rotor core fixed to the rotating shaft, a squirrel-cage winding provided on the outer periphery of the rotor core, and a squirrel-cage winding provided inside the cage-shaped winding of the rotor core. and three permanent magnet members extending in the circumferential direction arranged at approximately equal intervals in the circumferential direction, and these three permanent magnet members are magnetized in the radial direction and in the same direction, and the permanent magnet members are In a method for magnetizing a rotor of a permanent magnet type synchronous motor in which three image poles are formed in the circumferential direction, a rare earth magnet is used as the magnet material of the permanent magnet member, and a pole in a magnetizing iron core of a magnetizing device is used. One of the three permanent magnet members in the assembled rotor is attached to one of the magnetic pole parts with a smaller arc, and the other two are attached to the other magnetic pole part with a larger polar arc.
The magnetizing coils wound around the magnetizing iron core are energized to apply a large magnetic field to one permanent magnet member and a small magnetic field to the other two permanent magnet members. A method of magnetizing a rotor of a permanent magnet type synchronous motor, characterized in that the steps are performed sequentially for each of three permanent magnet members.