SAID ROTOR

The present invention refers to a rotor for an electrical machine comprising air cooling elements, and to an electrical machine comprising said rotor.

In particular, the invention refers to the air cooling of an electrical machine with internal magnets, more in particular a synchronous reluctance electrical machine of the type with permanent magnets.

An electrical machine typically comprises a fixed parts, the stator, and a mobile part, the rotor, arranged coaxially one inside the other. Typically, the rotor is placed inside the stator, which comprises electric oils adapted to generate a magnetic field, which allows rotating the rotor. The rotor typically comprises a body composed of a pack of sheets and placed on a rotation shaft. In the electrical motors with permanent magnets, the sheets comprise seats for the permanent magnets. In the electrical machines, and in particular in high-performance electrical motors with permanent magnets, it is necessary to reduce the temperatures which are reached in the rotor and in the magnets themselves, to avoid the loss of magnetization and the consequent performance drop.

For example, if magnets are too hot, the magnetic flux is less intense, which implies a loss of torque and therefore a worsening of the electrical machine performances .

The different electromagnetic components of an electrical machine, as well as some insulating materials used in the parts of the electrical machine, are sensitive to heating produced by the operation and their cooling is mandatory to dissipate heat in order to preserve a good efficiency of the machine, to extend its life and to limit its maintenance.

Patent application W02018069030 of the Applicant is known, and discloses an electrical machine which integrates a cooling system comprising two fans assembled fixed on the rotor shaft, next to the two ends of the rotor, each fan facing a flange, said fans being adapted to create an air flow to dissipate heat. Advantageously, each flange comprises wings adapted to direct the air flow created by each internal fan radially towards the heads of the stator coils, along a direction parallel to the rotor axis at the level of the coil heads.

These known electrical motors have the problem that they do not allow obtaining a good cooling of the rotor, in particular of its internal part.

Object of the present invention is solving this problem, by providing a rotor for an electrical machine comprising air cooling elements, and an electrical machine comprising said rotor, which allow improving the cooling of the rotor.

The above and other objects and advantages of the invention, as will result from the following description, are obtained by a rotor for an electrical machine comprising air cooling elements, and an electrical machine comprising said rotor, as claimed in the independent claims.

Preferred embodiments and non trivial variations of the present invention are the subject matter of the dependent claims .

It is intended that all enclosed claims are an integral part of the present description.

It will be immediately obvious that numerous variations and modifications (for example related to shape, sizes, arrangements and parts with equivalent functionality) can be made to what is described, without departing from the scope of the invention, as appears from the enclosed claims.

The present invention will be better described by some preferred embodiments thereof, provided as a non-limiting example, with reference to the enclosed drawings, in which:

Figure 1 shows an exploded view of a rotor for an electrical machine according to the invention;

Figure 2 shows a perspective cut-away view of a rotor for an electrical machine according to the invention; and

Figure 3 shows a side sectional view of a rotor for an electrical machine according to the invention.

With reference to the Figures, the electrical machine of the invention comprises: a stator; a rotor 10 comprising at least two lamellar packs 3 mutually separated by a separation zone 14 and fastened to a rotation shaft 1 assembled rotating inside the stator, each lamellar pack 3 comprising at least one opening 12 configured to allow the passage of an air flow coming from outside the rotor 10 towards inside the rotor 10; in particular, the opening 12 is configured to allow the passage of the air flow coming from outside the rotor 10 of the separating zone 14 between the two lamellar packs 3.

In a preferred way, the lamellar packs 3 each comprise at least one hole 12 and are separated by a central spacer 2, integral with the rotation shaft 1 and interposed between the lamellar packs 3, said central spacer 2 being preferably shaped with arms and configured to direct an air flow from the hole 12, obtained along the lamellar packs 3, through the separating zone 14 between the two lamellar packs 3 towards the external circumference of said lamellar packs 3; preferably, the electrical machine of the invention comprises a first and a second centrifugal fan 7, assembled fixed on the rotation shaft 1 next to a first and a second end of the rotor 10, and comprising internal arms 9 shaped to direct the air flow through the holes 12 obtained along the lamellar packs 3, and external wings 13 configured to direct the air flow towards the heads of the stator coils.

Preferably, each lamellar pack 3 is composed of a plurality of sheets 11, each sheet 11 comprising a central hole 31, inside which the shaft 1 is fastened, a plurality of seats 3, 4, 5 adapted to house permanent magnets and a plurality of holes 12, obtained in the part of each sheet 11 included between the central hole 31 and the seats 3, 4, 5, and adjacent to the rotation shaft 1, preferably said holes 12 being mutually at the same distance; in a preferred way, said sheets 11 are overlapped so that the respective holes 12 are mutually overlapped to form openings of the lamellar packs 3, which allow the passage of the air flow coming from outside the rotor 10, preferably from the internal arms 9 of the centrifugal fan 7, towards inside the rotor 10, preferably towards the central spacer 2.

In a preferred way, the central spacer 2 integral with the rotation shaft 1 and interposed between the lamellar packs 3 is shaped with arms 22 placed next to the spaces between the holes 12 obtained along the lamellar packs 3 and comprises a central hole 21 inside which the rotation shaft 1 is fastened.

Preferably, each centrifugal fan 7 comprises: a plurality of internal arms 9, placed in the part of the centrifugal fan 7 adjacent to the rotation shaft 1 and placed next to the spaces between the holes 12 obtained along the lamellar packs 3; a plurality of external wings 13 placed next to the external circumference of the centrifugal fan 7; a central hole 71 inside which the rotation shaft 1 is fastened.

When operating, the cooling of the rotor 10 is obtained by means of air circulation inside the holes 12 of the lamellar packs 3, which when flowing removes heat from the heated zones and gives it to the external walls of the rotor 10, which are forcedly cooled.

In particular, air is sucked by the central spacer 2, preferably by its arms 22, through the holes 12 obtained on the lamellar packs 3 of the rotor 10, and is pushed towards the external circumference of the rotor 10 through the separating zone 14 between the lamellar packs 3, in the spaces included between the arms 22 of the central spacer 2.

The air circulation in the holes 12 of the lamellar packs 3 is further enabled by the internal shaped arms 9 of the centrifugal fan 7, while the external wings 13 create an external air flow for cooling the stator.

Advantageously, the rotor 10 of the invention, due to the internal air circulation inside the rotor 10, allows reducing the temperatures reached in the rotor and in the magnets, to avoid losing magnetization and the consequent performance drop of the electrical machine.