RU2264022C2 - Rotor magnetic system and its manufacturing process - Google Patents

Abstract

FIELD: electrical engineering; mechanical design of rotor systems for permanent-magnet commutatorless electrical machines.

SUBSTANCE: proposed rotor magnetic system has electric steel stampings and N-S radially saturated magnets in the form of rectangular parallelepipeds uniformly disposed within stack of rotor stampings over its circumference. Rotor magnetic system section is assembled of four stacks joined by bars whose length is not smaller than that of section; like-polarity magnets alternately disposed in tandem are offset in axial direction through one fourth of stator slot angular pitch. Rotor magnetic system manufacturing process includes fabrication of two types of stampings wherein key slot and fixation holes for assembling stacks in section are offset relative to magnet holes through angles equal to (1/8)(360/Z) and (3/8)(360/Z) of stator slot angular pitch, respectively, where Z is double product of phase number by pole pair number and slot number per rotor pole and stator slot. Stacks whose number should be a multiple of four are assembled by installing magnets in them and joined in sections so as to ensure relative displacement of magnets in stacks arranged in tandem by one fourth of stator slot angular pitch. Alternative manufacturing process for rotor magnetic system includes fabrication of three types of stampings wherein key slot and holes for assembling stacks in section are offset relative to holes for fixation of magnets through angles equal to (3/40)(360/Z), (9/40)(360/Z), and (15/40)(360/Z) of stator slot angular pitch, respectively. Then stacks whose number should be a multiple of six are assembled by installing magnets in them and joined in sections so that magnets are relatively offset in stacks arranged in tandem by one sixth of stator slot angular pitch.

EFFECT: enhanced performance characteristics of commutatorless magnetoelectric machines, facilitated rotor manufacture, enlarged functional capabilities of such machines.

10 cl, 6 dwg

Description

The invention relates to the field of electrical engineering and relates to the design of magnetic systems of rotors of brushless electric machines with permanent magnets. The inventive method and device can be used both in electric motors and generators, and can improve the technical characteristics of electrical machines of these classes.

When converting electrical energy into mechanical energy and vice versa - mechanical into electrical energy, the magnetic flux associated with permanent magnets is called the magnetic flux of excitation. A device that generates a magnetic field flux is called an inductor. A rotor with permanent magnets of a certain shape and thickness placed on it is used as an inductor.

Due to the gear structure of the stator, the conductivity for the magnetic flux under the pole pieces turns out to be variable, which leads to fluctuations in the magnetic flux and causes either the appearance of additional higher-order emfs in the stator conductors for the generator or torque pulsation for the electric motors, which affects the technical characteristics of these machines. To eliminate these phenomena in machines with electromagnetic excitation, phase windings placed on the stator are stacked with an inclination to the longitudinal axis of the machine. To suppress the nearest additional harmonics, the value of the bevel slopes of the stator grooves is also selected. However, this leads to a rise in the cost of manufacturing the winding and worse use of the machine, since the coefficient of use of the groove decreases [1, p. 76].

Reducing additional harmonics can be achieved by skewing the pole tips of the rotor and by shifting the poles themselves [1, p. 76]. Known forms of pole pieces with beveled edges along the entire length of the rotor, and with stepped edges. However, in this case, the magnetic flux of the excitation is formed due to the passage of current through the winding located in the grooves of the rotor. The manufacturing technology of rotors with electromagnetic excitation is difficult, and for long machines, in which the ratio of the stator length to its diameter is more than two, it is also difficult to implement due to the decrease in stiffness of the shaft on which the magnetic system is located.

A well-known rotor of a downhole generator [2, p.1-8], in which the inductor has a considerable length and is made of permanent magnets of a ring-shaped shape with a hole in the center. Ring-shaped magnets are interconnected due to protrusions and depressions made along the diameter of the magnets. This design allows the rotor to be long enough, but the open surface of the rotor does not allow it to be used in aggressive liquids due to the destruction of magnets. They also lack bias, which suppresses additional harmonics of the created electromotive force.

Known magnetic circuit of an electric machine [3, p.1-2], in which to improve the vibro-acoustic characteristics make bevel teeth. The rotor magnetic circuit is assembled from plates having curvature mating with the surface of the yoke, and, in addition, each tooth is curved along a helix. This allows you to get beveled grooves on the rotor. Either an excitation winding, as, for example, for synchronous machines, or a squirrel cage, as for asynchronous, can be placed in these beveled grooves. However, permanent magnets are not used in machines of these classes.

Known rotor of an electric machine [4, p.1-4], which is made of two identical axial magnetic circuits, separated by a non-magnetic insert. The magnetization of N-S permanent magnets in these blocks has the opposite direction, and the magnets themselves are attached due to the fit along the side faces. At the same time, the magnets remain open, which does not allow them to be used when working in aggressive environments or under high pressure, and also limits the increase in speed due to the action of the centrifugal forces pulling them out of the rotor on the magnets.

Known submersible motor with permanent magnets [5, p.1-2], in which the permanent magnets are placed on the rotor in solid pieces over the entire length of the rotor. With this design of the electric motor, a reduction in the ripple of the moment due to the design of the rotor can be carried out only by increasing the number of magnets placed on the rotor. This is possible with a constant size of the magnets mounted on the rotor only by increasing the diameter, which is unacceptable for submersible electric motors, or by decreasing the pitch between the magnets while reducing their size, which changes their technical characteristics and leads to a deterioration in the machine's processability.

The rotor of an electric machine is also known [6, pp. 1-6], which is made by batching with permanent magnets laid in grooves with tangential magnetization N-S. With this design of the rotor, it is not possible to reduce ripple of the torque in the motor mode or suppress additional harmonics of the electromotive force in the generator mode. In addition, since there are gaps at the top, and the magnets have a surface that extends outside the rotor, the use of such machines for working in aggressive environments is impossible.

The fundamental differences in the designs of the rotors of electric machines and their magnetic systems allow us to conclude that the proposed design of the magnetic system of the rotor of a magnetoelectric submersible machine and the method of its manufacture are new. The use of the claimed design improves the technical characteristics of electrical machines, both by suppressing additional harmonics of the emf in the generators, and by reducing the ripple of the torque in the electric motors, and the inventive method of manufacturing a magnetic system improves the manufacturability of the rotor design by reducing the number of different parts and simplifying the manufacturing technology plates. With this design of the magnetic system, it is also possible to reduce the diameter of the rotor while maintaining the technical characteristics of the machine at the same level, or if the diameter is constant, the length of the machine can be reduced. Due to the placement of permanent magnets in the body of the rotor, the restrictions on the operation of the machine in aggressive environments and with the use of liquid cooling are removed.

The closest in essence is the rotor of an electric machine with a magnetic system, described in [1, p. 73-77] and taken as a prototype.

The aim of the invention is to increase the technical characteristics of brushless magnetoelectric machines and improve the manufacturability of the design of their rotors, which will expand the scope of application of electric machines of this class.

The goal is achieved through the use of a new design of the magnetic system of the rotor and the method of its manufacture. The design of the magnetic system is one or more sections consisting of complete packages, the number of which is a multiple of four. Within the length of one full section, the magnets of the same name located inside the package of plates are displaced along the length of the section relative to each other by one fourth of the angular pitch of the stator grooves φ, so that the total displacement is three fourth of the angular pitch of the stator grooves. This arrangement of magnets on the rotor allows, in combination with their number (four and six), optimally in terms of cost-quality ratio to eliminate the influence of additional harmonics of the emf for generators, or torque pulsation for electric motors and significantly simplify the manufacturing technology of the rotor magnetic system. In this case, the manufacture of plates for packages of the magnetic system of the rotor is carried out in a special way, so that to obtain a displacement of the magnets by three quarters of the angular pitch of the stator grooves, either four packages made using only two types of plates or six packages made using only three types of plates .

The invention consists in the following. In a magnetoelectric machine, the rotor poles are formed by permanent magnets 13 (Fig.3) with a radial magnetization of N-S. To install the magnets used packages in the assembly 12, consisting of plates of electrical steel 1, 7 (figure 1) and 8, 9 (figure 2). Magnets with a radial magnetization 13 (figure 3) are installed in the holes 17 obtained after assembly of the packages due to the holes 2 (figure 1, 2) in the plates. The holes 2 are made in such a way that an air gap 16 remains between the sides of the magnets and the package body, which reduces the flux of scattering of the magnets. When assembling the package, this air gap can be filled with adhesive for additional fixation of the magnets 13 in the axial direction and increase the rigidity of the structure. The number of magnets is related to the number of pole pairs by the dependence

N = 2p

where N is the number of magnets on the rotor;

p is the number of pairs of poles.

The plates are interconnected by adhesive. For additional connection, rods 15 are used. Packages are assembled in sections and fastened together using rods 14.

Thus, in the plates must necessarily be holes 2 (Fig. 1, 2) for installing magnets, holes 4 (Fig. 1) and 10 (Fig. 2) for connecting packages to a section and one groove 5 (Fig. 1) and 11 (figure 2) or more, coupled with an opening for the shaft 6, for connecting the section as a whole with the rotor shaft. Sheets in packages are connected by an adhesive. But also in the plates there may be holes 3 (Figs. 1, 2) for connecting them into a package due to additional rods. To eliminate the influence of connecting rods on the characteristics of the machine, these holes must have a plane of symmetry. The number of holes 4 and 10 is selected from the condition of stiffness of the section and their number must be at least three, and these holes must have at least one plane of symmetry.

Thus, in the plates there can be from two to three groups of holes: the first group - holes 2 (Fig. 1, 2) for magnets, the second group - openings for connecting packages to section 4 (Fig. 1) and 10 (Fig. 2 ) and keyways 5 (Fig. 1) and 11 (Fig. 2) and the third group - holes for connecting the plates into packages 3 (Figs. 1, 2). Packets are collected from each type of plate (FIG. 3). With a certain placement of the listed groups of holes relative to each other, for the manufacture of four types of plates and, accordingly, the assembly of four types of packages, only two dies are required. If they are not made by stamping, with such a mutual arrangement of all the holes for the manufacture of the rotor magnetic system, only two types of plates will be required, which also simplifies the manufacturing technology of the rotor magnetic system of the magnetoelectric machine and the entire machine as a whole.

Magnets are made by powder metallurgy methods and therefore, to ensure their quality, they must be of simple shape. The most common magnets are rectangular parallelepipeds. However, if in the prototype the poles of the rotor and, accordingly, the excitation flux are formed due to the excitation winding located on the rotor, which has an inclination to the longitudinal axis due to the displacement of the pole pieces, then the fundamental difference in the design of the rotor of the magnetoelectric machine is, on the one hand, and the rectangular shape the magnets themselves, on the other hand, do not allow in the same way to obtain a continuous displacement of the poles of the rotor along its length. The problem is solved by sequential discrete displacement of rectangular magnets by a total value equal to three fourth of the angular pitch of the stator slots φ (Fig. 4). For this, from the plates 1 (FIG. 1) and 8 (FIG. 2) having an offset of the first group of holes relative to the second, i.e. the angle between the axes aa and bb, equal to α in the first case, and between the axes bb and dd, equal to β in the second, collect packets 1 and 2. Packets 3 and 4, in which the angles are are equal to + α and + β, respectively, obtained by turning packages 1 and 2 around the axes BB and AA on an angle of 180 degrees. In this case, after assembling the packages into a single section connected by rods 14, the magnets are displaced relative to each other in successive packages by one fourth of the angular pitch of the stator grooves φ. The total angle displacement within one section is three fourth of the angular pitch of the stator grooves φ, which suppresses additional harmonics of the emf for generators and torque pulsations for motors. The plates are interconnected due to the adhesive composition or rods of magnetic material 15.

To obtain a three-fourths displacement of the angular pitch of the stator slots, four packets are necessary. For the manufacture of four bags, four types of plates are generally necessary. In the event that the plates are made by stamping, four different stamps are necessary. Using the inventive method of manufacturing plates to create a magnetic system, only two types of plates are sufficient, and, accordingly, in the manufacture of plates by stamping, which is advantageous in the production of a large number of products, two stamps are sufficient.

градусов, а другую пластину так, что в ней группа отверстий и шпоночного паза 10, 11 (фиг.2) окажется повернутой относительно группы отверстий под магниты 2 (фиг.2), которая жестко связана с группой отверстий для соединения пакета 3 (фиг.3) на угол β, абсолютная величина которого равна

градусов, то при повороте этих пластин вокруг своих осей А-А (фиг.1) и Б-Б (фиг.2) получаются еще два вида пластин, так, что при сборке секции из пакетов получается, что одноименные магниты равномерно по углу (фиг.4) смещены по длине секции на три четвертых углового шага пазов статора с шагом одна четвертая углового шага пазов статора. Количество пазов статора Z определяется выражениемThe essence of the proposed method of manufacturing a magnetic system of the rotor of a magnetoelectric machine is as follows. If you make one plate so that in it a group of holes and a keyway 4, 5 (Fig. 1) is turned relative to a group of holes for magnets 2 (Fig. 1), which is rigidly connected to a group of holes for connecting the package 3 (Fig. 1) ) by an angle α whose absolute value is equal to

degrees, and another plate so that in it a group of holes and a keyway 10, 11 (FIG. 2) is turned relative to the group of holes for magnets 2 (FIG. 2), which is rigidly connected to the group of holes for connecting the package 3 (FIG. 3) by angle β, the absolute value of which is equal to

degrees, when these plates rotate around their axes A-A (Fig. 1) and B-B (Fig. 2), two more types of plates are obtained, so that when assembling a section from packages, it turns out that the magnets of the same name are uniformly in angle ( 4) are displaced along the length of the section by three fourth angular pitch of the stator grooves with a step of one fourth of the angular pitch of the stator grooves. The number of stator slots Z is determined by the expression

Z = 2 · m · p · q,

where m is the number of phases of the machine;

p is the number of pole pairs of the machine;

q is the number of grooves per rotor pole and stator phase.

Since the Z value for machines of this class of this design is in the range 12-36, the number of phases has a standard value of three, and the q value for a submersible machine design must have an integer value and the number of pole pairs p must be even, the limits of variation of p values , q and Z are very limited and have optimal values for each design of an electric machine, and especially when it is used as an electric motor of submersible pumps for oil production. The q value must necessarily be an integer, since submersible machines operating at great depths perform high voltage to reduce cable losses, and the conductors in the stator groove to increase the reliability of the machine should be only one phase. This can be achieved when the stator windings are single-layer diametrical, for which the q value is an integer.

,

,

соответственно, где Z представляет собой удвоенное произведение количества фаз на число пар полюсов и число пазов на полюс ротора и фазу статора. Однако в этом случае незначительное улучшение характеристик магнитной системы ведет к существенному удорожанию конструкции.If necessary, it is possible to obtain a magnetic system in which the section will consist of six packets. In this case, three types of plates will be required, in which the group of holes for magnets with holes for connecting into packages is rotated relative to the group of holes for connecting packages in a section and keyway at angles whose absolute values are equal

,

,

respectively, where Z is the double product of the number of phases by the number of pole pairs and the number of grooves per rotor pole and stator phase. However, in this case, a slight improvement in the characteristics of the magnetic system leads to a significant increase in the cost of the structure.

Since the claimed design in itself is new, then, accordingly, the method of its production is new and has no analogues. The authors are not aware of the use of such technologies for the manufacture of plate plates.

The magnetic system of the rotor, depending on the required characteristics, can be formed using either one section (Figs. 4, 5) or several sections (Fig. 6). In this section can be of different lengths. If the minimum length of the section is needed, then only four packets are used (Fig. 4). If it is necessary to increase the length of the magnetic system of the rotor, then the number of packets is applied, a multiple of four, and the packets of the same name are located next to each other (figure 5). Moreover, all these packages are in one section. If there are three types of plates, the number of packets in the section will be a multiple of six. Moreover, all the principles of building a magnetic system remain the same.

If it is necessary to unload the bearings of the machine from the action of an external force constantly acting in the axial direction, then a rotor is used, in which the magnetic system is formed by one section consisting of four packets, as shown in Fig. 4, or by a section formed by a multiple increase in the number of similar packets in the section (figure 5). In this case, the displacement of the magnets clockwise or counter to the magnet in the first packet is selected depending on the direction of action of the external force. Rotors with such a magnetic system are especially convenient when used in pump motors to lift liquids to high heights.

In the absence of an external force that is constantly acting in the axial direction to unload the bearings of the machine, or to eliminate the influence of the axial force of the machine itself, to ensure high-quality regulation, a magnetic system is used, consisting of an even number of sections, in which one half of the sections has a displacement of the magnets relative to the other half of the sections in the opposite direction. A magnetic system, consisting, for example, of two sections, is presented in Fig.6. In this case, the sections can be arranged in random order.

The special advantages of this design of the magnetic system of the rotor of a magnetoelectric machine include the fact that it is possible to change the length of the magnetic system by reducing the thickness of the packets while maintaining the magnet displacement step. This allows for stators with one pitch of grooves, but with different lengths, to use the same component plates.

Thus, the inventive device, the rotor magnetic system and the method of its manufacture meet the criteria of the invention of "novelty" and can improve the technical characteristics of brushless magnetoelectric machines using the inventive device and simplify their manufacturing technology and expand the scope of application of electric machines of this class.

The need to use the inventive rotor magnetic system arises when using brushless magnetoelectric machines in submersible pumps for oil production, operating in an aggressive environment where large capacities, limiting radial dimensions, liquid cooling or good adjusting properties are required.

Literature

1. Ivanov V.I. Synchronous machines. Leningrad, VETA-KUBUCH, 1934, 339 p.

2. RF patent RU No. 2183043. Downhole generator rotor.

3. USSR Copyright Certificate SU No. 1105981. Magnetic circuit of an electric machine.

4. RF patent RU No. 2178615. The rotor of an electric machine.

5. Application No. 98103834/09, 03.03.1998. Permanent magnet submersible motor.

6. Description of the invention to the copyright certificate SU 1098070.

Claims (10)

1. The rotor magnetic system, consisting of plates of electrical steel and magnets in the form of rectangular parallelepipeds, having a radial magnetization NS, placed uniformly around the circumference inside the packages assembled from the plates, characterized in that the section of the magnetic system of the rotor is formed by four packages connected by rods not less than the length of the section, with the offset of the magnets of the same name, sequentially located one after another, in the axial direction by one fourth of the angular pitch of the stator slots. 2. The rotor magnetic system according to claim 1, characterized in that the plates in the packages are interconnected by an adhesive composition. 3. The rotor magnetic system according to claim 1, characterized in that the plates in the packages are interconnected by rods having at least one plane of symmetry. 4. The rotor magnetic system according to claim 1, characterized in that the plates in the packages are interconnected by rods having at least one plane of symmetry and an adhesive composition. 5. The rotor magnetic system according to one of claims 1 to 4, characterized in that the section is made with additional packets, with the total number of packets being a multiple of four, and the packets of the same name are arranged sequentially one after another. 6. The magnetic rotor system according to one of claims 1 to 4, characterized in that it is equipped with additional sections, each of which consists of four packages. 7. The magnetic system according to claim 6, characterized in that in the sections the direction of the angular displacement of the magnets of the same name alternates. 8. The rotor magnetic system according to one of claims 1 to 4, characterized in that the cavities formed by the side faces of the magnets and the body of the package due to the shape of the hole are filled with an adhesive. 9. A method of manufacturing a rotor magnetic system, which consists in the fact that two types of plates are made in which the keyway and the holes for connecting the packets into the section are offset from the magnet hole by angles equal to

and

the angular pitch of the stator grooves, respectively, where Z is the double product of the number of phases by the number of pole pairs and the number of grooves per rotor pole and stator phase, collect the number of packets that is a multiple of four by installing magnets in them and connect the packets in sections so that they provide an offset magnets relative to each other in sequentially arranged packets one fourth of the angular pitch of the stator slots. 10. A method of manufacturing a rotor magnetic system, which consists in the manufacture of three types of plates, in which the keyway and the holes for connecting the packets into the section are offset from the hole for the magnets by angles equal to

,

and

the angular pitch of the stator grooves, respectively, where Z is the double product of the number of phases by the number of pole pairs and the number of grooves per rotor pole and stator phase, collect the number of packets that is a multiple of six by installing magnets in them and connect the packets in sections so that they provide an offset magnets relative to each other in successive packets of one sixth of the angular pitch of the grooves of the stator.

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