RU231957U1 - Rotor of an electric machine with permanent magnets - Google Patents

Abstract

The utility model relates to electrical engineering. The technical result is a reduction in losses from eddy currents. The rotor of an electric machine contains a rotor core with incorporated permanent magnets located in groups along a circumference in close proximity to the outer surface of the magnetic circuit, internal cavities, and grooves made on the outer surface of the magnetic circuit in the gaps between the poles perpendicular to the end parts of the poles. To achieve the technical result, the rotor core is made of a package of plates made of thin-sheet laminated electrical isotropic steel, electrically insulated from each other. Each rotor pole is formed by a group containing three permanent magnets located at two levels relative to the rotor rotation axis. In each group, at the level closest to the rotor rotation axis, there are two permanent magnets identical in size and characteristics. The permanent magnets are made in the form of a set of plates connected to each other in a permanent connection, for example, by gluing. The internal cavities are located with ferromagnetic gaps in the rotor core between its poles. 5 z.p. f-ly, 5 fig.

Description

Field of technology

The utility model relates to electrical engineering, in particular to electric machines with permanent magnets in the rotor, and can be used in traction synchronous electric motors and electric generators in electric transport.

State of the art

The prior art discloses a rotor of an electric machine, which includes a magnetic circuit on the surface of which permanent magnets are placed in pairs with the same poles, and the distance between the magnets of a pair is less than between adjacent magnets of different pairs (patent RU 2273084, published 27.03.2006). According to the known solution, the distance between the magnets in a pair is less than the distance between the pairs of magnets. The adjacent side surface of each of the magnets of one pair forms an angle with a plane passing through the outer edge of the corresponding magnet and the rotor axis that is different from zero and is within the range from 0 to 30 geometric degrees. That is, as can be seen from Fig. 1 to the description of the known solution, the magnets have a cross-section of a rather complex shape.

The disadvantages of the known solution include the increased labor intensity of manufacturing an electric machine, associated with the need to manufacture magnets that have a complex spatial shape.

The closest in terms of the set of essential features - the prototype of the claimed utility model - is the rotor of an electric machine with permanent magnets, containing a magnetic circuit with incorporated permanent magnets, located in groups along the circumference in close proximity to the outer surface of the magnetic circuit, internal cavities between the said magnets and grooves made on the outer surface of the magnetic circuit in the gaps between the poles perpendicular to the end parts of the poles (patent RU 2579011, published 03/27/2016). According to the known solution, each group of permanent magnets forming a pole contains two permanent magnets located in a common plane.

It is known that when designing rotors of electrical machines with built-in (incorporated) permanent magnets, there is a layout problem of magnet placement. To solve it, the magnets of each pair must be installed with a rotation relative to each other at a certain angle, so that they do not form a common plane, that is, the pole must be made in the form of a so-called reverse V-shaped profile (Smirnov A.Yu. "Features of Design and Analysis of High-Speed Synchronous Machines with Permanent Magnets on the Rotor". / Proceedings of the Nizhny Novgorod State Technical University named after R.E. Alekseev. - 2013. - No. 4 (101). P. 231-235). In this case, the magnets occupy less space between the shaft and the outer surface of the rotor, which allows, on the one hand, to increase the mechanical strength of the rotor, and, on the other hand, to reduce its outer diameter, thereby limiting the radial forces capable of destroying it.

The disadvantages of the known solution include the limitations it imposes in terms of strength, which is associated with the arrangement of the electromagnets in the rotor in one plane in each pair.

Disclosure of a utility model

In the context of this application, the following terms will be used as synonyms:

- "magnetic circuit" and "rotor core",

- "ferromagnetic gaps", "bridges", "jumpers",

- "internal cavities", "internal non-magnetic pockets",

- "rotor core", "core", "magnetic circuit".

The technical task is to create a design for the rotor of an electric machine with permanent magnets (hereinafter referred to as the rotor), which allows increasing the efficiency coefficient (hereinafter referred to as the COP) of the electric machine while maintaining the strength of the rotor.

The technical result consists in reducing losses due to eddy currents.

The solution to the technical problem is achieved through the combined use of the following design measures:

- making the rotor core from a package of thin-sheet laminated electrical isotropic steel plates, electrically insulated from each other;

- the implementation of each rotor pole by a group containing three permanent magnets incorporated into the rotor core, located at two levels relative to the rotor rotation axis, while in each group at the level closest to the rotor rotation axis, two permanent magnets of identical size and characteristics are located,

- the production of permanent magnets in the form of a set of plates connected to each other in a permanent connection, for example, by gluing,

- placement of internal cavities with ferromagnetic gaps in the rotor core between its poles.

The novelty of the proposed technical solution is the implementation of the core from a package of plates made of thin-sheet laminated electrical isotropic steel, electrically insulated from each other, the implementation of each rotor pole as a group containing three permanent magnets incorporated into the rotor core, located at two levels relative to the rotor rotation axis, while in each group at the level closest to the rotor rotation axis, two permanent magnets of the same size and characteristics are located, the implementation of permanent magnets in the form of a set of plates connected to each other in a permanent connection, for example, by gluing, the placement of internal cavities with ferromagnetic gaps in the rotor core between its poles.

The permanent magnets incorporated into the core are made using rare earth metals. Each of the permanent magnets included in the group forming the rotor pole is made as a set of plates made of magnetic material, connected to each other in a permanent connection, for example, glued together.

Each rotor pole is formed by a group containing three incorporated permanent magnets located at two levels relative to the rotor rotation axis. At the level closest to the rotor rotation axis, a pair of permanent magnets identical in size and characteristics are located. The third permanent magnet included in each pole is located at a level remote from the rotor axis and may have dimensions and characteristics different from the permanent magnets located at the previous level. In the context of the present application, the said levels are conventionally defined as lower and upper, respectively.

The use of groups of individual magnets instead of single magnets of the same volume allows to reduce losses from eddy currents in magnets and to increase the length of the leakage field closure. In addition, the presence of two levels of placement with permanent magnets located on them allows to improve the shape of the electromotive force (hereinafter - EMF) in the air gap of the electric machine. The direction of magnetization of groups of permanent magnets of adjacent poles is opposite.

Adjacent rotor poles are separated by ferromagnetic gaps. According to the applicant's experience, the width of the ferromagnetic gaps between adjacent internal cavities should not exceed 1 mm. The width of the internal cavities should also not exceed 1 mm. In order to ensure the strength of the core, the corners of the internal cavities are rounded.

On the outer surface of the rotor core in the bridge area, slots are made. This is done so that the air gap in the areas between the rotor poles is larger than in the areas above the center of the pole (on the cylindrical sections of the core). This ensures the required ratio between the inductances along the longitudinal and transverse magnetic axes of the rotor. In addition, due to the presence of slots, losses in the rotor are reduced, causing heat generation in this area.

The number of slots is determined by the number of rotor poles. The slots can be made in any way known from the prior art.

The presence of non-magnetic cavities (pockets) in the core body, including near the edges of the permanent magnets, allows for an increase in the scattering path length, thereby improving the shape of the field in the gap and, as a consequence, increasing the EMF, reactive torque and efficiency.

Between the permanent magnets installed at the lower level, a jumper made of a steel plate (sheet) is made. The jumper provides additional mechanical strength to the core.

Other design features, including dimensions, their ratios, grades of materials used, technologies for producing parts and assembling the product, not disclosed in the materials of this application, are not subject to patent protection.

Brief description of the drawings

Fig. 1 shows a general view of the rotor magnetic system.

Fig. 2 shows a rotor segment.

Fig. 3 shows the distribution of magnetic induction in the air gap obtained in the first example of implementing the proposed utility model.

Fig. 4 shows the distribution of magnetic induction in the air gap obtained in the second example of implementing the proposed utility model.

Fig. 5 shows the magnetic field lines in a rotor segment made in accordance with the proposed utility model.

Implementation of a utility model

The rotor is a core 1 with permanent magnets 2, 3, 4 incorporated into it.

In Fig. 1 the core 1 is shown in an image simulating perspective. In reality the core 1 has a cylindrical outer shape. In the core 1 there are cavities for installing permanent magnets 2, 3, 4, ferromagnetic gaps 5 between the internal cavities 6, internal non-magnetic pockets 7 and grooves 8 on the outer surface of the core 1.

Permanent magnets 2, 3 and 4 are made using rare earth materials.

Permanent magnets 3 and 4 are located at the lower level, and permanent magnet 2 is located at the upper level.

The specific energy of magnets 3 and 4 is less than the specific energy of magnet 2.

The magnetization vector of magnets 2, 3 and 4 is located in the radial direction of the rotor.

Between permanent magnets 3 and 4 a jumper 9 is made from a sheet of steel.

Fig. 3, as a first example of implementation, shows the distribution of magnetic induction in the air gap when using permanent neodymium magnets made of N52UH material at both levels (permanent magnets 2, 3, 4).

Fig. 4 shows, as a second embodiment example, the distribution of magnetic induction in the air gap when using a permanent neodymium magnet made of N52UH material as magnet 2. In this case, permanent neodymium magnets made of N38SH material were used as permanent magnets 3 and 4.

The adjacent rotor poles are separated by ferromagnetic gaps 5. The presence of slots 8 on bridges 5 results in the air gap in the slot 8 zone being larger than under the middle of the pole - on the cylindrical sections of core 1. This ensures the required ratio between the inductances along the longitudinal and transverse magnetic axes of the rotor. In addition, due to the presence of slots 8, internal cavities 6 and internal non-magnetic pockets 7, the losses in the rotor causing heat generation are reduced.

The presence of internal non-magnetic pockets 7 in the body of the core 1 near the edges of the permanent magnets 2, 3, 4 allows increasing the length of the scattering path, due to which an improvement in the shape of the field in the gap is achieved and, as a consequence, an increase in the EMF, torque and efficiency. This effect is illustrated by the image in Fig. 5.

The proposed design of the rotor of an electric machine with permanent magnets is oriented towards the use of existing serial production technologies. In particular, the rotor core is made of serially produced steel sheet metal (electrical steel), and the permanent magnets are manufactured using known technologies. Assembly also does not require the development of processes that are fundamentally different from those currently used in industry. This allows us to speak about the industrial applicability of the proposed utility model.

Claims (6)

1. A rotor of an electric machine with permanent magnets, comprising a rotor core with incorporated permanent magnets arranged in groups around a circumference in close proximity to the outer surface of the magnetic circuit, internal cavities, and slots made on the outer surface of the magnetic circuit in the spaces between the poles perpendicular to the end portions of the poles, characterized in that the core is made from a package of plates made of thin-sheet laminated electrical isotropic steel, electrically insulated from each other, each rotor pole is formed by a group containing three permanent magnets incorporated into the rotor core, arranged at two levels relative to the rotor rotation axis, wherein in each group at the level closest to the rotor rotation axis, two permanent magnets of the same size and characteristics are located, the permanent magnets are made in the form of a set of plates connected to each other in a permanent connection, for example, by gluing, the internal cavities are located with ferromagnetic spaces in the rotor core between its poles. 2. The rotor according to paragraph 1, characterized in that the third permanent magnet, located at a level remote from the rotor axis, has dimensions and characteristics that differ from the permanent magnets located at a level closest to the axis. 3. Rotor p. 1, characterized in that the permanent magnets are made using rare earth metals. 4. The rotor according to item 1, characterized in that the groove located on the outer surface of the rotor and separating adjacent poles of the rotor from each other has lateral sides parallel to the axis of rotation of the rotor. 5. The rotor according to item 1, characterized in that internal non-magnetic pockets are made in the body of the rotor core near the edges of the permanent magnets. 6. The rotor according to item 1, characterized in that a jumper made of a steel plate is made between the permanent magnets located at the lower level.