CH672701A5 - - Google Patents

Description

DESCRIPTION This invention is based on a synchronous motor with permanent magnetic excitation according to the preamble of claim 1. Such a synchronous motor, shown for example in DE-A-2 252 922, is an internal rotor, rod-shaped permanent magnets being arranged in the grooves of the rotor. The longitudinal axis of the permanent magnets is oriented perpendicular to the longitudinal axis of the rotor shaft and tangential to the circumference of the rotor shaft. In the transverse ■

Cut through the rotor, the permanent magnets are located on the same radius line around the rotor shaft. However, this has the disadvantage that such an internal rotor motor only manages relatively low speeds after the centrifugal forces on the permanent magnets become so great at higher speeds that the rotor is open to the mechanical loads that arise, in particular when the permanent magnets are arranged radially outwards Grooves, no longer withstands. The uneven or non-equally spaced arrangement of the cage bars of the short-circuit cage around the circumference of the rotor also results in an unfavorable asynchronous start-up.

The object of this invention is to develop a synchronous motor of the type mentioned at the outset in such a way that it is suitable for significantly higher speeds, such as those which occur when AC is supplied with higher frequencies.

To achieve the object, the invention is characterized by the features specified in the characterizing part of claim 1 and the independent claim 2.

The continuous ring that thus forms on the outer circumference of the rotor and completely surrounds the rotor captures the centrifugal forces of the permanent magnets that occur in the grooves and act radially outwards, and conducts the forces via the spokes remaining in the spaces between the grooves in the radially inner part of the rotor laminated core.

The ring and the spokes are dimensioned in terms of good material utilization and good magnetic and mechanical requirements.

The permanent magnets are advantageously embedded in the grooves in a two-component resin, so that this forms a homogeneous, force-symmetrical rotor body which is capable of absorbing extremely high centrifugal forces. The permissible speed of the synchronous motor according to the invention can therefore be increased significantly compared to known synchronous motors.

A sine field distribution can be approximated by the choice of permanent magnets of different thicknesses or by the omission of magnets in predetermined grooves in the rotor laminated core. This design allows the use of simple punching tools in the single-groove process.

A rare earth-cobalt-sintered connection (SECO) is preferred as the material for the permanent magnets, since such magnets in the rod-like design are cheaper than ceramic magnets and allow a relatively small distance between the air gap and the short-circuit cage. As a result, the asynchronous torque is better.

In order to obtain sufficient induction B in the air gap, the magnetic surface per pole must correspond as closely as possible to the pole surface. The thickness of the permanent magnets depends on the required field strength H.

If the cage bars of the short-circuit cage are arranged between the permanent magnets on the same pitch circle, this is at the expense of the magnets or the achievable flux. In addition, problems arise when soldering the cage bars to a closed short-circuit cage and, moreover, the installation of the permanent magnets is more difficult to accomplish.

The exact shape of the cage bars, which are arranged on a pitch circle radially inward behind the permanent magnets and their position (either on a gap with the permanent magnets or on the same radius beam) is of some importance only in relation to the permissible induction in the remaining iron cross section.

In a further development of the subject of the present application, it is provided that the permanent magnets instead of Giess5

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Cast resin with aluminum. After this operation, the permanent magnets must be magnetized on the finished rotor.

The invention is explained in more detail below with reference to the attached drawing figures in several embodiments.

In the drawings:

Figure 1 shows schematically a view of a rotor according to the invention;

Figure 2 is a partial plan view of a rotor blade according to the invention;

3 shows a partial longitudinal section through a rotor according to the invention, showing the casting or casting of the permanent magnets;

FIG. 4 shows a schematic representation of the induction in the air gap, measured over the angle of rotation with the motor unwound in the plane;

FIG. 5 shows the same form of representation as FIG. 4, but with a different rotor configuration;

Figure 6 shows the same form of representation as Figure 4, but with a different rotor assembly.

In the rotor 1 shown in FIG. 1, the rotor laminated core 26, consisting of individual rotor disks 27 (FIG. 2), is connected to the rotor shaft 2 in a rotationally fixed arrangement. Grooves 28 (FIG. 2) for introducing cage bars 3 of a short-circuit cage 4 are arranged in the rotor laminated core 26. Radially outwards of the grooves 28 for the cage bars 3, grooves 6 are provided for receiving the permanent magnets 8 which are rectangular in cross section.

The longitudinal axes 29 of the grooves 6 run parallel to the longitudinal axis of the rotor shaft 2 and are at a mutual circular distance 31.

For a better overview, a groove 6 is shown cut in full length in FIG. 1, from which it can be seen that a plurality of identical permanent magnets 8 can be inserted into the respective groove 6 lying one behind the other.

The grooves are introduced into the rotor laminated core 26 from the end face 5 of the rotor 1 and are completely closed radially outward in the direction of the outer casing 7, so that the casing 7 is formed by a circumferential, self-contained ring 30, which is formed by the permanent magnets 8 receives radially outward-pointing centrifugal forces and transmits them to the rotor shaft 2 via the respective individual rotor blades 27 of the rotor laminated core 26.

FIG. 3 shows the embedding of the permanent magnets 8 in the associated grooves 6 of the rotor laminated core 26. In die672 701

sem operation with a rotor 1 upright on the lower end face, a fitting 10 is fastened with an internal sealing ring 12, which prevents the casting resin 11 poured into the groove 6 at the top from escaping at the bottom.

The upper end face 5 of the rotor laminated core 26 encloses an upper molding 9, as a result of which the casting resin 11 can be easily poured from a suitable container into the open-top groove 6, in which, as can be seen, several permanent magnets 8 of the same type have already been introduced one after the other.

In order to achieve a sufficient flow of the synthetic resin in the groove 6 around the permanent magnets 8, it is advantageously heated to about 120 ° C. and then poured in. After the casting resin has hardened, a rotor with high mechanical strength is created which is also capable of absorbing high centrifugal forces. The permanent magnets 8 advantageously have a play of approximately 0.1 mm in the grooves 6 in order to ensure that the synthetic resin flows past.

FIG. 4 shows the simplest case of a field distribution, namely that of a rectangular field distribution 20, which is achieved in that the magnet arrangement 23 is made in the development in such a way that a row of equally strong permanent magnets with, for example, north polarity at the top has the same row of equally strong Permanent magnets with south polarity on top follow. The ideally desired sinusoidal curve 19 is only insufficiently approximated.

A better approximation to a sinusoidal curve 19 is shown in the exemplary embodiment according to FIG. 5, where grooves 6 remain empty at certain points, i.e. are not occupied with permanent magnets 8. A “0” is entered at this point in the schematically illustrated magnetanoidization 24.

The resulting rectangular field distribution, designated 21, is characterized in that in the area of the “0” passages of the sinusoidal curve 19, the magnetic induction B in the area of the gap 22 is “0”. The rectangular field distribution 21 is thus narrower over the angle of rotation.

6 shows, as a further exemplary embodiment, a better approximation of the field distribution 32 to the sinusoidal curve 19. The magnet arrangement 25 is made here in such a way that permanent magnets 8a of half the thickness are installed in the associated groove 6 in the region of the “0” passage of the curve 19 , which is shown schematically in the diagram with the symbols N-2 and S-2.

According to a further embodiment, the magnet arrangement 25 according to FIG. 6 can also be combined with the magnet arrangement 24 according to FIG. 5.

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3 sheets of drawings

Claims (8)

672 701 1. Synchronous motor with permanent magnetic excitation, in which a short-circuit cage for asynchronous starting is arranged in the grooves of a rotor laminated core and rod-shaped permanent magnets are arranged in further grooves, characterized in that the permanent magnets (8) radially outward of the cage rods (3) of the short-circuit cage (4) located closed grooves (6) within the circumferential surface of the rotor laminated core (26) are arranged at a distance therefrom, the outer walls of these grooves (6) integrally connected to the rotor laminated core (26) via the useful spaces form a closed rotor jacket (7) which introduces the centrifugal force acting on the permanent magnets (8) during operation via spokes remaining in the spaces between the grooves into the radially inner part of the laminated core. 2.Synchronous motor with permanent magnetic excitation, in which a short-circuit cage for asynchronous starting and in rod-shaped permanent magnets are arranged in the grooves of a rotor laminated core, characterized in that the permanent magnets (8) and the cage bars (3) of the short-circuit cage (4) on the same pitch circle and in each case in closed grooves (6) of the rotor laminated core (26) are arranged, the outer walls of these grooves (6, 28) connected in one piece to the laminated rotor core (26) via the usable spaces form a closed rotor casing (7) which forms the during operation, centrifugal force acting on the permanent magnets (8) and the cage bars (3) introduces spokes remaining in the spaces between the grooves (6, 28) into the radially inner part of the laminated core. 2nd PATENT CLAIMS 3. Synchronous motor according to claim 1 or 2, characterized in that the permanent magnets (8) in the closed grooves (6) of the rotor laminated core (26) are embedded for fixing in plastic casting resin. 4. Synchronous motor according to one of claims 1-3, characterized in that the closed grooves (6) for receiving the permanent magnets (8) to approximate a sinusoidal induction (curve 19) in the air gap in the boundary region of the magnetic poles are unoccupied (Fig 5). 5. Synchronous motor according to one of claims 1-3, characterized in that in the closed grooves (6) for receiving the permanent magnets (8) for approaching a sinusoidal induction (curve 19) in the air gap in the boundary region of the magnetic poles, sheet metal strips are inserted . 6. Synchronous motor according to one of claims 1-3, characterized in that the closed grooves (6) for receiving the permanent magnets (8) to approximate a sinusoidal induction (curve 19) in the air gap in the boundary region of the magnetic poles with permanent magnets (8a ) less thickness are occupied (Fig. 6). 7. Synchronous motor according to one of claims 1-6, characterized in that the material of the permanent magnets (8, 8a) is a rare earth cobalt sintered connection. 8. Synchronous motor according to claim 1 or 2, characterized in that the permanent magnets are cast with aluminum for fixing.