RU2822213C1 - Electric machine - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: electrical machine comprises a stator housing and a rotor sleeve made from non-laminated ferromagnetic material, a shaft, two or more laminated stator packages installed in the housing with axial gaps, in the slots of which there is a multiphase p-pole winding, laminated rotor packages with p/2 teeth, which form pairs with stator packages. One or more excitation coils are fixed on the stator in axial gaps between pairs of stator and rotor packages. Magnets with coercive force of at least 3 kOe are installed in slots of rotor packages. A feature of the invention is the design of the permanent magnets, in which the magnet has an outer section, which widens towards the bottom of the rotor slot, radial size of which is not less than 1/4 of the radial size of the magnet, and the angles formed by the tangent planes to the opposite side surfaces are not less than 20°. Distance from the surface of the magnet facing the stator to the inner surface of the stator package is not more than a tenth of the radial size of the magnet.

EFFECT: improving reliability of electric machine, increasing its efficiency, specific moment and power.

3 cl, 3 dwg

Description

The invention relates to electric machines, in particular to electric machines with permanent magnets on the rotor, and can be used in electric drives and generator sets.

An analogue of the proposed electric machine is the electric machine described in the book “Design of Electrical Machines of Autonomous Objects” authored by A.M. Sugrobova and A.M. Rusakova (M: MPEI Publishing House 2012), having:

- stator housing made of unlaminated ferromagnetic material,

- shaft,

- a bushing made of unlaminated ferromagnetic material mounted on the shaft,

- laminated stator packages installed in the housing with a gap, without rotation relative to each other,

- p-pole winding (p = 2, 4, 6, 8 ... - any natural even number), installed in the slots of the stator packages, made with a coil pitch along the slots of more than one,

- laminated rotor packages with p/2 teeth, installed on a bushing opposite the stator packages and with rotation between adjacent packages by pole division, i.e. at an angle of 360°/p,

- one or more field coils mounted on the stator and installed in each space between the rotor or stator packages.

This and other machines mentioned in this description may also have other components that ensure the structural integrity of the machine: various fasteners; bearings that ensure rotor rotation; bearing shields, etc. To prevent the excitation magnetic flux from closing through the shaft, this shaft and/or bearing shields are made of non-magnetic or weakly magnetic material. In addition, the housing, rotor bushing and shaft can be either solid or consist of separate parts, and the breakdown into parts does not interfere with the flow of magnetic flux through these elements. Also, the p-pole stator winding can either consist of separate windings installed in each of the stator packages, or be common to all packages, that is, the grooved parts of each coil of this winding pass through all the stator packages. The excitation winding can be located in the following areas of the gaps between pairs of stator and rotor packages: the area between the p-pole winding and the rotor bushing, the area between the p-pole winding and the housing.

The disadvantage of this design is the incomplete use of the stator surface, namely: each rotor package forms only half of the total number of poles p of the electric machine. As a result, the specific power of the machine and its efficiency decrease.

Another analogue of the proposed electric machine is an axial inductor machine with hybrid excitation, described in the article “Hybrid Excitation of the Axial Inductor Machine” authored by S. Orlova, V. Pugachov, N. Levin, published in the Latvian Journal of Physics and Technical Sciences (January 2012, 49(1):35-41, DOI: 10.2478/v10047-012-0004-6), developed as an undercar generator, which in addition to the above elements contains magnets with a coercive force of at least 3 kOe (245 kA/m ), installed in the grooves of the rotor packages, and magnetized radially or uniformly, forming only south or only north poles on each rotor package, and the directions of magnetization of these poles on adjacent packages are opposite.

As a result of better use of the stator surface, such a machine increases efficiency and specific torque compared to an axial reluctance machine without magnets. However, the presence of magnets leads to the risk of irreversible demagnetization. To prevent irreversible demagnetization of permanent magnets, the machine is made multi-pole (an analogue with hybrid excitation has 20 poles). Which leads to an increase in the frequency of the supply voltage and an increase in the cost of the inverter. In addition, the armature and field winding currents are limited to prevent demagnetization.

The closest analogue is the machine described in the article “Design Optimization of a Synchronous Homopolar Motor with Ferrite Magnets for Subway Train” authored by Dmitrievsky V.A., Prakht V.A. and Kazakbaev V.M. published in Mathematics (January 2023, 11(3):1-17, DOI: 10.3390/math11030589)

characterized by the fact that :

- has a stator housing made of unlaminated ferromagnetic material,

- has a shaft,

- has a sleeve made of unlaminated ferromagnetic material mounted on the shaft,

- has two laminated stator packages installed in the housing with axial gaps, without angular displacement relative to each other, and with an 8-pole winding installed in the grooves of the stator packages,

- has two laminated rotor packages with 4 teeth, mounted on a bushing opposite the stator packages and with an angular displacement between the packages by a pole division, that is, at an angle of 45°,

- has an excitation winding fixed to the stator and installed in the axial gap between the stator and rotor packages installed opposite each other,

- has permanent magnets installed in the grooves of the rotor packages, forming only south or only north poles on each rotor package, and these poles on adjacent packages are opposite in direction,

- coercive force of magnets is at least 3 kOe,

- the surfaces of each groove of the laminated rotor package and each magnet contain two flat side sections,

- the gap formed by the surfaces of the rotor teeth and the surfaces of the magnets facing the inner surface of the stator, and the internal surfaces of the stator packages is the same throughout the entire structure,

- a magnet is completely adjacent to the bottom of each groove,

- the sides of the magnets are not adjacent to the sides of the rotor teeth.

Thanks to this, they find themselves outside the strong demagnetizing fields of the windings. Also, to remove permanent magnets from the strong demagnetizing fields of the windings in this machine, chamfers can be made between the flat side surfaces of permanent magnets installed in the grooves of the rotor and the surfaces of these magnets facing the inner surface of the stator for the purpose of further removing magnets from the strongest magnetic windings .

As a result, the reliability of the electrical machine is increased by reducing the demagnetizing force acting on the magnets, preventing the demagnetization of magnets, increasing the current load, as well as increasing the efficiency and power density without increasing the frequency of the supply voltage and the cost of the inverter due to avoiding the location of magnets in the strongest demagnetizing fields of the windings.

To reduce the demagnetizing effect of the field winding field on the magnets, the rotor grooves are made deep, and the magnets are made of large radial width, which increases the mass of the magnets and reduces the size of other parts of the machine, including the armature winding, stator housing and rotor bushing. An increase in the mass of magnets leads to an increase in the price of the machine and to an increase in centrifugal force, which reduces the maximum permissible speed. Reducing the size of the armature winding, stator housing and rotor bushing leads to an increase in the electrical resistance of the winding and magnetic saturation of the housing and bushing. As a result, efficiency decreases.

At the same time, the magnetic field strength is formed not only by the windings, but also by the magnet itself. However, in this solution this field is not generated to prevent demagnetization of the magnets.

Thus, the technical problem solved by the present invention is to further increase the reliability of the electric machine by reducing the demagnetizing force acting on the magnets, preventing demagnetization of the magnets, increasing the current load, increasing the efficiency and power density without increasing the frequency of the supply voltage and the cost of the inverter, reducing the mass of the magnets , as well as an increase in the maximum permissible rotor speed.

The essence of the invention is illustrated by sketches that show:

- fig. 1 is a three-dimensional view of an electrical machine, which is shown with 1/2 of the stator cut out and the rotor shown uncut;

- fig. 2 - part of the cross section of a machine having stator and rotor packages with permanent magnets installed in the rotor slots, corresponding to one tooth division of the rotor;

- fig. 3 explains the algorithm for constructing a magnet cross section.

As can be seen from Fig. The machine stator 1 contains a housing 1 made of solid ferromagnetic material, for example, unalloyed annealed steel. The rotor has a shaft 2, onto which a sleeve 3 made of solid ferromagnetic material is mounted. In housing 1, three laminated stator packages 4 are installed with axial gaps and without rotation relative to each other. Three laminated gear packages of the rotor 6 are installed on the bushing 3 opposite the packages of the stator 4. As a result, there are also axial gaps between the packages of the rotor 6. An 8-pole stator winding 5 is installed in the stator packages 4. The number of rotor teeth is four, that is, two times less than the number of poles of the stator winding. Adjacent rotor packages have a slot shift relative to each other by one rotor pole division equal to 360°/p = 45°, where p = 8 is the number of poles. In each axial gap between pairs of rotor and stator packages installed opposite each other, one or more field winding coils 8 are installed. Permanent magnets 7, magnetized radially or uniformly, are installed in the grooves of rotor packages 6. Magnets 7 with a coercive force of at least 3 kOe only south or only north poles are formed on each rotor package 6, and the magnetization directions of these poles on adjacent packages are opposite. Also in FIG. 1 shows a holder 9 of the excitation coil, fixing it on the stator.

Fig. 2 shows part of the cross section of a machine having stator and rotor packages with permanent magnets mounted on the rotor, corresponding to one tooth division of the rotor. Fig. 2 serves only to illustrate the geometric meaning of the various lettered segments and arcs mentioned below, and the geometric relationships between dimensions shown therein may not correspond to the relationships described below.

The surface of the magnet has a section adjacent to the bottom of the groove of the rotor package 13.

The permanent magnet 7 has an outer section 12, widening towards the bottom of the rotor groove, the radial size of which is at least 1/4 of the radial size of the magnet, and the angles formed by the tangent planes to the opposite side surfaces 10 are less than 20°,

- the distance from the surface of the magnet 11 facing the stator to the inner surface of the stator package 14 is no more than a tenth of the radial size of the magnet.

Fig. 3 explains an example of constructing a cross section of a magnet.

MM’ is the surface of the magnet adjacent to the bottom of the groove of the rotor package.

DCC’D’ is the outer section that widens towards the bottom of the rotor slot. The surface DCC'D' facing the stator is represented by the curve CC'. The lateral surfaces are represented by curves DC and C'D'.

Points K and K' are selected on the curves DC and C'D' at the same distance from the center of rotation O. Since DCC'D' is a widening section, the length of the segment KK' increases as it moves in this direction.

The maximum segment cut off from the ray drawn through the axis of rotation of the rotor O by curves DD’ and CC’ is the radial size of the outer section h.

The maximum segment cut off from the beam drawn through the axis of rotation of the rotor O by curves MM' and CC' is the radial size of the magnet section H. h ≥ H/4.

The inner surface of the stator package is a cylinder inscribed in the stator package. In the projection shown in Fig. 2. it is represented by a circle.

The maximum segment cut off from the beam drawn through the axis of rotation of the rotor O by curves CC’ and the projection of the inner surface of the stator package is the distance from the surface of the magnet to the inner surface of the stator δ. δ ≤ 0.1 H.

The tangents to the DC and C'D' curves at any arbitrary points, selected one at a time on these curves, form an angle of at least 20 mechanical degrees, which ensures the widening of the DCC'D' magnet section towards the bottom of the groove.

The magnetization of a permanent magnet creates a magnetic flux, which, covering the distance from the surface of the magnet facing the stator to the inner surface of the stator package, creates a magnetomotive force aimed at demagnetizing the magnet. Provided that the distance from the surface of the magnet facing the stator to the inner surface of the stator package is no more than a tenth of the radial size of the magnet, this magnetomotive force is not large enough to demagnetize the magnet.

Due to the fact that in the outer section, which widens towards the bottom of the rotor groove, the angles formed by the tangent planes to the opposite side surfaces are at least 20°, the deeper parts of the widening section of the magnet create a magnetic field strength in the more outer parts, which prevents the demagnetizing effect of the windings .

Due to the shape of the magnet, the deeper parts of the expanding section, on the contrary, are subject to a demagnetizing effect due to the MMF that occurs when covering the distance from the surface of the magnet to the surface of the stator. However, they are affected by the weaker demagnetizing field of the windings. As a result of the fact that the radial size of the expanding section is at least ¼ of the radial size of the magnet, demagnetizing factors are not sufficient to demagnetize the magnet even with increasing current in the windings.

In addition, the magnetic field strength generated by the magnet itself, which prevents the magnet from demagnetizing, prevents the magnet from demagnetizing even if the height of the rotor slot and the radial size of the magnet are reduced, which reduces its mass and the centrifugal force acting on it. Therefore, the rotation speed of the rotor can be increased without the risk of destruction.

The technical result of the proposed solution is to increase the reliability of the electric machine by reducing the demagnetizing force acting on the magnets; preventing magnet demagnetization; increasing current load; increasing efficiency and power density without increasing the frequency of the supply voltage and the cost of the inverter; reducing the mass of the magnets, as well as increasing the maximum permissible rotor speed.

Claims (15)

1. Electric machine, characterized in that: - has a stator housing made of unlaminated ferromagnetic material, - has a shaft, - has a sleeve made of unlaminated ferromagnetic material mounted on the shaft, - has two or more laminated stator packages installed in the housing with axial gaps, without angular displacement relative to each other, and with a p-pole winding (p = 2,4,6,8... – even number) installed in the slots of the stator packages , - has laminated rotor packages with p/2 teeth, mounted on a bushing opposite the stator packages and with an angular displacement between adjacent packages by pole division, that is, at an angle of 360°/p, - has one or more annular field coils mounted on the stator and installed in each axial space between pairs of stator and rotor packages installed opposite each other, - has permanent magnets installed in the grooves of the rotor packages, forming only south or only north poles on each rotor package, and these poles on adjacent packages are opposite in direction, - coercive force of magnets is at least 3 kOe, - the surface of the magnet has a section adjacent to the bottom of the groove of the rotor package, wherein: - the permanent magnet has an outer section that widens towards the bottom of the rotor groove, the radial size of which is at least 1/4 of the radial size of the magnet, and the angles formed by the tangent planes to the opposite side surfaces are at least 20°, - the distance from the surface of the magnet facing the stator to the inner surface of the stator package is no more than a tenth of the radial size of the magnet. 2. An electric machine according to claim 1, in which the permanent magnets are magnetized radially. 3. An electric machine according to claim 1, in which the permanent magnets are uniformly magnetized.