Asynchronous self-braking electric motor with double squirrel-cage rotor for driving production lines

Abstract

FIELD: electrical engineering.SUBSTANCE: asynchronous self-braking electric motor which contains a stator with an excitation winding, a cylindrical double rotor that has the ability to move axially. A brake spring is installed between the rotor parts. Conical brake pads are provided on the inner surfaces of the bearing shields. The rotor magnetic circuit packs are connected to the shaft by means of splined connections made mirror image relative to the center of the stator magnetic circuit along a helicoidal surface with an axial bevel angle relative to the longitudinal axis of the shaft. Thin-film washers made of dielectric material are fixed to the inner contacting end surfaces of the rotor magnetic circuit packs. The rotor winding rods are made with a bevel relative to the rotor shaft rotation axis, and the direction of rotor rotation coincides with the increase in the axial bevel angle of the rods from the middle to the edges of the magnetic core packages, and the axial bevel angle of the winding rods does not exceed one tooth division of the rotor.EFFECT: possibility of use in explosive zones, a reduction in the intensity of noise and vibration of the electric motor, and a smoothing of the torque curve.1 cl, 3 dwg

Description

[0001] The invention relates to electrical engineering and can be used in units and drive mechanisms with fast and precise automatic stopping when the drive electric motor is operating in one direction, i.e. in production lines.

[0002] A self-braking asynchronous electric motor with a twin squirrel-cage rotor for driving production lines is known (RU Patent No. 2661641, published in Bulletin No. 20 on July 18, 2018). The self-braking asynchronous electric motor comprises a stator consisting of a housing, a laminated magnetic circuit with a cylindrical bore excitation winding, and bearing shields with bearings. Conical brake shoes with rigidly attached brake linings are mounted on the inner surfaces of the bearing shields. The rotor contains a shaft with cylindrical laminated double packs of magnetic circuits, located symmetrically in the axial direction relative to the stator magnetic circuit and coupled to the shaft by means of splined connections with the possibility of axial movement in an air gap formed between its parts with a brake spring installed between them, placed on the shaft.The outer cylindrical surfaces of the dual magnetic core stacks contain slots containing winding rods, the ends of which are short-circuited by rings at the ends of the magnetic cores. The winding rods are arranged axially, mirror-image relative to the center, with a bevel relative to the rotor shaft's axis of rotation. The direction of rotor rotation coincides with the increasing axial bevel angle of the winding rods from the center to the edges of the magnetic core stacks.

[0003] When voltage is applied to the electric motor stator excitation winding, a rotating magnetic field is generated. This field interacts with the currents flowing through the squirrel-cage rotor winding bars. This results in a torque (according to Ampere's law) acting on the magnetic core stacks of the dual rotor. Simultaneously, an axial electromagnetic force is generated, caused by the main magnetic flux and the leakage fluxes of the end faces and the rotor slot bevel. A prototype of this design demonstrated that the component of the axial electromagnetic force caused solely by the interaction of the main magnetic flux and the leakage fluxes of the end faces is small.

[0004] Under this force, the magnetic core stacks, along with the conical hardened plates, move in opposite directions, compressing the brake spring. This causes the air gap 8 between the inner end surfaces of the magnetic core stacks to disappear, the magnetic core stacks are joined together, and the motor brake is released.

[0005] Disconnecting the m-phase stator excitation winding from the power source will cause the electric motor's electromagnetic field energy to decay. This will reduce the rotor speed and, consequently, the main magnetic flux will no longer be able to hold the conical hardened laminations and magnetic core stacks in the operating position. The action of the brake spring causes mutual axial displacement of the conical hardened laminations and magnetic core stacks. Each conical hardened lamination contacts its own brake lining, and an air gap δ is formed between the inner end surfaces of the magnetic core stacks. Friction between the conical mating surfaces of the conical hardened laminations of the rotor and the brake linings causes the rotor and drive mechanism to rapidly stop.

[0006] When voltage is applied, currents will flow in each winding of the dual rotor until the magnetic core stacks close. These currents arise due to the potential difference between the inner and outer sides of the short-circuited rings of each winding of the dual rotor. When the magnetic core stacks close, the inner short-circuited rings of the dual rotor windings connect and short-circuit. Since the inner short-circuited rings of the windings of each dual rotor have different potentials, and the currents flowing through the inner short-circuited rings of each winding of the dual rotor are in opposite directions, a transient process will occur in the rotor winding at the moment of their connection, leading to energy redistribution.A short circuit of currents of equal magnitude but opposite direction flowing through the internal short-circuited rings of each of the windings of the double rotor will occur, which will lead to their mutual compensation through a spark discharge.

[0007] When the electric motor is turned off, when the magnetic circuit packs begin to diverge from each other, the internal short-circuited rings of the double rotor windings will open from each other, which will lead to a spark discharge.

[0008] A disadvantage of this design is that sparking between the internal short-circuited rings of the twin-rotor windings during starting and stopping makes it impossible to use this type of asynchronous electric motor in hazardous areas. Furthermore, a current drop in the rotor windings during starting will lead to a drop in starting torque and, consequently, axial thrust, which degrades the motor's performance.

[0009] In this design, the chamfer of the squirrel-cage rotor slots eliminates or significantly reduces the negative phenomena associated with higher harmonics of the magnetic field and serves to generate axial electromagnetic force.

[0010] The skew value is determined by calculation during the motor design and depends on its dimensions, number of poles, stator-to-rotor slot ratio, and other parameters. According to technical literature and reference books on electrical machine design, the standard and optimal skew value for a squirrel-cage rotor slot does not exceed one rotor tooth pitch, while the magnitude of axial electromagnetic forces arising in asynchronous electric motors is insignificant.

[0011] Increasing the rake angle by more than one tooth pitch of the rotor in this design will lead to an increase in the axial electromagnetic force, but at the same time will lead to a significant increase in the leakage inductive resistance and, as a consequence, to a decrease in starting characteristics and power factor, i.e., its operational and energy characteristics.

[0012] An additional drawback of this design is that the limited ability to increase the rake angle of the winding bars beyond one rotor tooth pitch limits the ability to generate significant axial electromagnetic force, which dramatically reduces braking efficiency and positioning accuracy of the self-braking electric motor and the electric drive as a whole. This ultimately leads to a significant limitation in the application area of ​​this type of electric motor.

[0013] The invention closest in technical essence and achievable result to the claimed invention is the "Self-braking asynchronous electric motor with a double squirrel-cage rotor for driving production lines" (RU Patent No. 2655654, published in Bulletin No. 16 dated May 29, 2018). The electric motor comprises a stator with a cylindrical bore with an excitation winding, a cylindrical double rotor located on the shaft symmetrically in the axial direction relative to the stator magnetic circuit with the possibility of axial movement in the air gap formed by the rotor parts, between which a brake spring is installed, put on the shaft. Conical brake shoes with rigidly fixed brake linings are made on the inner surfaces of the bearing shields.The magnetic core stacks of the cylindrical dual rotor are laminated and assembled from sheets of electrical steel. The outer cylindrical surfaces of these stacks contain slots containing winding rods, the ends of which are short-circuited by rings at the ends of the magnetic cores. The winding rods are arranged mirror-image relative to the center, axially parallel to the machine's axis of rotation. The magnetic core stacks of the cylindrical dual rotor are mated to the shaft via splined joints, mirror-image relative to the center of the stator magnetic core, along a helicoidal surface with an axial bevel angle relative to the longitudinal axis of the shaft. The direction of rotation of the rotor shaft coincides with the increasing axial bevel angle of the splined joints from the shaft edges toward the center.

[0014] When voltage is applied to the electric motor stator excitation winding, a rotating magnetic field is generated. This field interacts with the currents flowing through the squirrel-cage rotor winding bars, resulting in a torque (according to Ampere's law) acting on the magnetic core stacks of the dual rotor. An axial electromagnetic force is generated by the axial magnetic flux and leakage fluxes of the end faces and splined connections, which are mirror images of the stator magnetic core center with an axial bevel angle relative to the longitudinal shaft axis. In this case, the angle of axial bevel of spline joints in helical gears is taken from 7 to 20° (Machine parts and design: a tutorial / V.A. Sultanov, O.R. Karataev, I.I. Khafizov. - Kazan: Kazan University Publishing House, 2021 - 150 p., p. 24).

[0015] In this design, the axial bevel angle of the splined connections from 7 to 20° allows for a significant axial electromagnetic force to be obtained, which increases the braking efficiency and positioning accuracy of the self-braking electric motor and the electric drive as a whole.

[0016] Under this force, the magnetic core stacks, along with the conical hardened plates, move in opposite directions, compressing the brake spring. This causes the air gap 5 between the inner end surfaces of the magnetic core stacks to disappear, the magnetic core stacks are joined together, and the motor brake is released.

[0017] Disconnecting the m-phase stator excitation winding from the power source will cause the electric motor's electromagnetic field energy to decay. This will cause the rotor speed to decrease, and, consequently, the main magnetic flux will be unable to hold the conical hardened laminations and magnetic core stacks in their operating position. Moreover, the rotor magnetic core stack speed will decrease faster than the drive mechanism speed due to the large difference in their moments of inertia. The difference in the speeds of the rotor magnetic core stacks and the drive mechanism will contribute to the rotor magnetic core stacks receiving additional acceleration due to the excess torque of the drive mechanism, accelerating their twisting along the splined connections from the center of the stator magnetic core to the braking device.Additionally, the action of the brake spring causes mutual axial displacement of the conical hardened plates and the magnetic core stacks. Each conical hardened plate contacts its own brake lining, and an air gap δ is formed between the inner end surfaces of the magnetic core stacks. The friction between the conical mating surfaces of the rotor's conical hardened plates and the brake linings causes the rotor and drive mechanism to rapidly stop.

[0018] When voltage is applied, currents will flow in each winding of the dual rotor until the magnetic core stacks are closed. These currents arise due to the potential difference between the inner and outer sides of the short-circuited rings of each winding of the dual rotor. When the magnetic core stacks close, the inner short-circuited rings of the dual rotor windings connect and short-circuit. Since the inner short-circuited rings of the windings of each dual rotor have different potentials, and the currents flowing through the inner short-circuited rings of each winding of the dual rotor are in opposite directions, a transient process will occur in the rotor winding at the moment of their connection, leading to energy redistribution.A short circuit of currents of equal magnitude but opposite direction flowing through the internal short-circuited rings of each of the windings of the double rotor will occur, which will lead to their mutual compensation through a spark discharge.

[0019] When the electric motor is turned off, when the magnetic circuit packs begin to diverge from each other, the internal short-circuited rings of the double rotor windings will open from each other, which will lead to a spark discharge.

[0020] A disadvantage of the prototype is that sparking between the internal short-circuited rings of the twin-rotor windings during starting and stopping makes it impossible to use this type of asynchronous electric motor in hazardous areas. Furthermore, a current drop in the rotor windings during starting will lead to a drop in starting torque and, consequently, in the axial thrust generated by the chamfered spline connections, which degrades the motor's performance.

[0021] Furthermore, the presence of short-circuited windings on a double rotor, the rods of which are located parallel to the axis of rotation of the rotor shaft, allows higher harmonics to create large additional moments (Geyler B., Gamata V. Higher harmonics in asynchronous machines / Translated from English edited by E.G. Kaganov. - Moscow: Energia, 1981. - 352 p., pp. 108, 116, 120, 203). In this case, additional moments appear mainly during the starting process and changes in the rotor speed, leading to the appearance of dips and peaks (reactive moments) of the torque and an increase in the intensity of noise and vibration of the electric motor, which entails a deterioration in its operational characteristics.

[0022] All this ultimately leads to a limitation of the scope of application of this type of electric motors.

[0023] The objective of the proposed invention is to improve the electric motor, allowing to expand the scope of its application.

[0024] The technical result of the claimed invention is to expand the scope of application due to the possibility of using electric motors in explosive zones, reducing the intensity of noise and vibration of the electric motor, leveling the torque curve, preventing the occurrence of dips and peaks during start-up and operation.

[0025] The technical result is achieved in that the asynchronous self-braking electric motor with a double squirrel-cage rotor for driving production lines contains a stator with a cylindrical bore with an excitation winding, a cylindrical double rotor located on a shaft symmetrically in the axial direction relative to the stator magnetic circuit with the possibility of axial movement in an air gap formed by parts of the rotor, between which a brake spring is installed, put on the shaft, bearing shields with bearings, on the inner surfaces of which conical brake shoes with rigidly fixed brake linings are made, wherein the magnetic circuit packs of the cylindrical double rotor are made laminated and assembled from sheets of electrical steel, on the outer cylindrical surfaces of which grooves are made with winding rods located in them, the ends of which are short-circuited at the ends of the magnetic circuits by rings, wherein the winding rods,the magnetic circuits located in the slots are arranged mirror-image relative to the center in the axial direction, and the magnetic circuit packages of the cylindrical dual rotor are coupled to the shaft by means of splined connections that are made mirror-image relative to the center of the stator magnetic circuit along a helicoidal surface with an axial bevel angle relative to the longitudinal axis of the shaft, and the direction of rotation of the rotor shaft coincides with an increase in the axial bevel angle of the splined connections from the edges of the shaft to the middle, while thin-film washers made of dielectric material are fixedly fixed on the inner contacting end surfaces of the magnetic circuit packages of the cylindrical dual rotor, at the same time, the slots are made with winding rods located in them with a bevel relative to the axis of rotation of the rotor shaft, and the direction of rotation of the rotor coincides with an increase in the axial bevel angle of the winding rods from the middle to the edges of the magnetic circuit packages,where the angle of the axial bevel of the winding rods does not exceed one tooth division of the rotor.

[0026] The presence of a bevel of the winding rods in the slots not exceeding one tooth division of the rotor of doubled rotor magnetic circuit packs levels out the torque curve, reduces torque dips during starting and operation of the electric motor (Geyler B., Gamata V. Higher harmonics in asynchronous machines / Translated from English edited by E.G. Kaganov. - Moscow: Energia, 1981. - 352 p., p. 172), reduces the intensity of noise and vibration (Geyler B., Gamata V. Higher harmonics in asynchronous machines / Translated from English edited by E.G. Kaganov. - Moscow: Energia, 1981. - 352 p., p. 227) and ensures high operational and energy characteristics.

[0027] Asynchronous electric motors are widely used in hazardous areas because their design eliminates the need for brush-collector assemblies, which are prone to sparking.

[0028] Complete elimination of sparking between the internal short-circuited rings of the double rotor windings during starting and stopping, due to the insulation of the internal surfaces of the magnetic circuit packages of the cylindrical double rotor with the windings, makes it possible to use this type of asynchronous electric motors in explosive zones.

[0029] Furthermore, the insulation between the internal surfaces of the magnetic core stacks of a cylindrical dual rotor and the windings during start-up, when the magnetic core stacks close, increases the current in the rotor windings, the starting torque, and, consequently, the axial thrust, improving its performance. All of the above will expand the scope of application of this type of electric motor.

[0030] Fig. 1 shows the general view of an asynchronous self-braking electric motor with a double squirrel-cage rotor for driving production lines.

[0031] Fig. 2 shows a general view of the double rotor magnetic core packs with slots containing short-circuited windings located in them.

[0032] Fig. 3 shows the removal of section A.

[0033] An asynchronous self-braking electric motor with a double squirrel-cage rotor for driving production lines comprises a housing 1, in which a laminated magnetic circuit of a stator 2 is placed, having a cylindrical bore with an m-phase excitation winding of the stator 3.

[0034] The magnetic core packs 4.5 of the cylindrical twin rotor are laminated with slots on the outer cylindrical surfaces in which the winding bars 6, 7 are located, the ends of which are short-circuited at the ends of the magnetic core packs 4, 5 by rings 8, 9 and 10, 11, respectively. The slots with the winding bars 6.7 are arranged mirror-image relative to the center of the magnetic cores in the axial direction, parallel to the machine rotation axis. The magnetic core packs 4, 5 have the ability to freely move in opposite directions along the shaft 12 and are connected to it by means of splined connections 13. In this case, splined connections 13 are made mirror-image relative to the center of the stator magnetic core 2 along a helicoidal surface with an axial bevel angle α of the splined connections 13 relative to the longitudinal axis of the shaft 12.When designing and manufacturing this electric motor, it is necessary to consider the tasks required of the specific electric drive and to be extremely careful when selecting the axial bevel angle α of spline joints 13 relative to the longitudinal axis of shaft 12, as this will affect the machine's performance. Increasing the axial bevel angle α of spline joints 13 relative to the longitudinal axis of shaft 12 will proportionally increase the axial electromagnetic force.

[0035] The use of splined connections 13 for aligning shaft 12 with magnetic circuit packs 4, 5 allows for precise centering of magnetic circuit packs 4, 5 of the rotor in relation to the magnetic circuit of the stator 2 and for having a safety margin under dynamic loads with relative axial movement.

[0036] Between the magnetic circuit packs 4, 5 on the shaft 12, there is a brake spring 14, which decompresses them in the absence of voltage on the m-phase excitation winding of the stator 3, forming an air gap 5. The total length of the double magnetic circuit packs 4, 5 with the compressed brake spring 14 without an air gap δ is equal to the length of the stator magnetic circuit 2.

[0037] Bearing shields 15, 16 are fastened in housing 1 by means of bolts 17, 18. Shaft 12 is based in bearing shields 15, 16 by means of radial bearings 19, 20, the inner rings of which rest against its projections, and the outer rings are fixed in bearing shields 15, 16 by means of covers 21, 22 by means of bolts 23, 24. Between the magnetic circuit of stator 2 and the packs of magnetic circuits 4, 5 there is a working air gap, which allows the rotor to rotate relative to the magnetic circuit of stator 2 on radial bearings 19, 20.

[0038] On the outer end surfaces of the magnetic circuit packs 4, 5 of the double rotor, conical hardened plates 29, 30 are rigidly fixed. On the inner side of the bearing shields 15, 16, conical brake shoes 25, 26 are made in the form of projections, on which brake linings 27, 28 are rigidly fixed. Uniform wear of the brake linings 27, 28 of the braking device is ensured under the condition that at the manufacturing and assembly stage, a symmetrical arrangement in the axial direction of the cylindrical rotor pack, consisting of two magnetic circuit packs 4, 5, is carried out to the magnetic circuit of the stator 2 and a mirror arrangement of the slots with the rods of the windings 6, 7 located in them relative to its center is carried out.

[0039] Thin-film washers 31 made of dielectric material are fixedly attached to the inner contacting end surfaces of the magnetic circuit packs 4, 5 of the cylindrical double rotor (Fig. 3).

[0040] The thickness of thin-film washers 31 varies from fractions of a nanometer to several microns and therefore their presence will not affect the performance of the electric motor.

[0041] The asynchronous self-braking electric motor with double squirrel-cage rotor for driving production lines operates as follows.

[0042] The phase sequence of the voltage supplied to the m-phase stator excitation winding is pre-coordinated so that the direction of rotation of shaft 12 coincides with an increase in the axial bevel angle α of splined joints 13 from its edges to the center. When voltage is applied to the m-phase stator excitation winding 3, the main magnetic flux and leakage fluxes arise, which intersect the working air gap, magnetic core stacks 4, 5, and the air gap δ.

[0043] Under the action of the axial electromagnetic force caused by the main magnetic flux and the leakage fluxes of the end parts (due to the tendency of the electric motor rotor to be located in the “magnetic middle” in relation to the stator, that is, in the position in which the magnetic resistance of the air gap δ has the smallest value, which corresponds to the most advantageous energy position), the conical hardened plates 29, 30 together with the packs of magnetic circuits 4, 5 move counter-moving, sliding along the splined connections 13 along the shaft 12, thereby compressing the brake spring 14, the thin-film washers 31 made of dielectric material are connected to each other and the motor is released.

[0044] At the same time, the main magnetic flux intersects the magnetic core stacks 4, 5 with the winding bars 6, 7 located thereon. The ends of these winding bars are short-circuited at the ends of the magnetic core stacks 4, 5 by rings 8, 9 and 10, 11, respectively, and induces an EMF in them. Since the ends of the winding bars 6, 7 are short-circuited, forming a closed circuit, current will flow through them. The rotating magnetic field, interacting with the currents flowing through the rotor winding bars 6, 7, will generate a torque (according to Ampere's law), which will act on the magnetic core stacks 4, 5 of the dual rotor.

[0045] Bearing shields 15, 16 are secured in housing 1 by means of bolts 17, 18. In this case, shaft 12 is based in bearing shields 15, 16 by means of radial bearings 19, 20, the inner rings of which rest against its projections, and the outer rings are fixed in bearing shields 15, 16 by means of covers 21, 22 by means of bolts 23, 24. Between stator magnetic circuit 2 and magnetic circuit packs 4, 5 there is a working air gap, which makes it possible for magnetic circuit packs 4, 5 of the rotor to simultaneously rotate relative to stator magnetic circuit 2 on radial bearings 19, 20 and to move in the axial direction along shaft 12 on splined connections 13.

[0046] Since the magnetic circuit packs 4, 5 of the dual rotor are movably coupled in the axial direction with the shaft 12 by means of splined connections 13, which are made mirror image relative to the center of the magnetic circuit of the stator 2 along a helicoidal surface with an angle α of the axial bevel of the splined connections 13 relative to the longitudinal axis of the shaft 12, then when the rotor shaft 12, which is fixedly connected to the drive mechanism, is braked, the magnetic circuit packs 4, 5 of the dual rotor, under the influence of torque, will be wound along the splined connections 13 to the center of the magnetic circuit of the stator 2, located fixedly in the housing 1, additionally increasing the existing axial electromagnetic force F and thereby accelerating the moment in time at which the dual parts of the magnetic circuit packs 4, 5 of the rotor will completely move away from the brake linings 27, 28, and the rotor will be released from the braking device. During the starting process, the air gap δ is reduced to zero and then does not affect the engine operating mode.

[0047] Disconnecting the m-phase excitation winding of stator 3 from the power source will lead to the attenuation of the electromagnetic field energy of the electric motor. This will cause a gradual decrease in the rotor speed and, accordingly, the main magnetic flux will be unable to hold the conical hardened laminations 29, 30 together with the magnetic core stacks 4, 5 in the operating position. Moreover, the decrease in the rotational speed of the rotor magnetic core stacks 4, 5 will occur faster than the decrease in the speed of the drive mechanism due to the large difference in their moments of inertia. The difference in the speeds of the rotor magnetic core stacks 4, 5 and the drive mechanism will contribute to the fact that the rotor magnetic core stacks 4, 5 receive additional acceleration due to the excess torque of the drive mechanism for accelerated twisting them along the splined connections 13 from the center of the stator magnetic core 2 to the braking device.In addition, the presence of an angle α of the axial bevel of the splined connections 13 relative to the longitudinal axis of the shaft 12 when twisting the magnetic circuit packs 4, 5 of the rotor along the splined connections 13 from the center of the magnetic circuit of the stator 2 to the braking device makes it possible to increase the axial electromagnetic force F due to the additional effect of the reaction of the splined connections 13 on the magnetic circuit packs 4, 5 of the rotor and will contribute to an increase in braking efficiency and positioning accuracy.

[0048] In addition, the brake spring 14 causes a mutual axial displacement of the conical hardened plates 29, 30 together with the magnetic circuit packs 4, 5. In this case, each conical hardened plate 29, 30 comes into contact with its brake lining 27, 28, and an air gap δ is formed between the inner end surfaces of the magnetic circuit packs 4, 5. As a result of friction of the conical mating surfaces of the conical hardened plates 29, 30 of the rotor and the brake linings 27, 28, rigidly fixed on the conical brake shoes 25, 26, the rotor stops.

Claims

An asynchronous self-braking electric motor with a double squirrel-cage rotor for driving production lines, comprising a stator with a cylindrical bore with an excitation winding, a cylindrical double rotor located on a shaft symmetrically in the axial direction relative to the stator magnetic circuit with the possibility of axial movement in an air gap formed by parts of the rotor, between which a brake spring is installed, put on the shaft, bearing shields with bearings, on the inner surfaces of which conical brake shoes with rigidly fixed brake linings are made, wherein the magnetic circuit packs of the cylindrical double rotor are made laminated and assembled from sheets of electrical steel, on the outer cylindrical surfaces of which grooves are made with winding rods located therein, the ends of which are short-circuited at the ends of the magnetic circuits by rings, wherein the winding rods,the magnetic circuits located in the slots are arranged mirror-image relative to the center in the axial direction, and the magnetic circuit packages of the cylindrical dual rotor are coupled to the shaft by means of splined connections that are made mirror-image relative to the center of the stator magnetic circuit along a helicoidal surface with an axial bevel angle relative to the longitudinal axis of the shaft, and the direction of rotation of the rotor shaft coincides with an increase in the axial bevel angle of the splined connections from the edges of the shaft to the middle, characterized in that thin-film washers made of a dielectric material are fixedly fixed on the inner contacting end surfaces of the magnetic circuit packages of the cylindrical dual rotor, at the same time the slots are made with winding rods located in them with a bevel relative to the axis of rotation of the rotor shaft, and the direction of rotation of the rotor coincides with an increase in the axial bevel angle of the winding rods from the middle to the edges of the magnetic circuit packages,where the angle of the axial bevel of the winding rods does not exceed one tooth division of the rotor.

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