WO2021079175A1

WO2021079175A1 - Electrical machine

Info

Publication number: WO2021079175A1
Application number: PCT/IB2019/059095
Authority: WO
Inventors: Рафаэль ВИРАБЯН; Сергей ДАШКЕВИЧ; Александр КОТОВИЧ
Original assignee: Общество С Ограниченной Ответсвенностью"Хевн Сторм"
Priority date: 2019-10-24
Filing date: 2019-10-24
Publication date: 2021-04-29

Abstract

The invention relates to an electrical machine which comprises a stator having cores with pole tips, and a rotor having permanent magnets and being rotatable in the stator. The stator is equipped with coils that are wound on the cores and interact with the magnets of the rotor across an air gap between the rotor and the stator. The cores with pole tips are arranged at intervals in a circle between inner and outer connecting housings which form a hollow space. Mounted between the cores of the stator is a flow-splitting ring which splits the hollow space of the stator into a space for a liquid for cooling a winding and a space for collecting liquid containing the heat produced by the stator winding. The technical result consists in increasing the specific power and specific torque of an electrical machine.

Description

Electric car

Technology area

The invention relates to an electrical machine that comprises a stator with pole-piece cores and a permanent magnet rotor rotatable in a stator. The stator is equipped with coils wound on cores that interact with the rotor magnets through an air gap between the rotor and stator. The machine can be either a motor or a generator and in many variants can be realized as an axial flux machine. In particular, the present invention relates to an electric machine without a yoke and with a segmented armature, hereinafter referred to as "H-machine".

Prior art

Known H-machine [1], which contains, successive coils wound around rods installed around the circumference of the stator located parallel to the axis of rotation of the rotor. The rotor has two sections containing permanent magnet disks that face both ends of each stator coil. In a known machine, the lines of magnetic induction in any working section pass as follows: through the first coil - into the first magnet on the first section of the rotor, then, through the rotor yoke - onto the adjacent second magnet on the first section, and then, through the second stator coil, adjacent to the first coil into the first magnet on the second section of the rotor, aligned with the second magnet on the first section, and, through the yoke of the second section, into the second magnet in the second section, aligned with the first magnet on the first section. The chain ends through the first spool. In the description of the known machine, the topology of the "H-machine" is given, indicating its advantages due to the reduced amount of iron in the stator, which allows to improve the torque density.

A specific problem for "H - machines" with a high torque density is that at high torques, a significant amount of heat is generated in the coils, which is often the limiting factor for the torques used.

Based on the fact that the magnetic coupling between coils and permanent magnets depends on the strength of the magnetic field created permanent magnets and windings of the stator cores and the permeability of the magnetic system, a core with high magnetic permeability is used, around which the coils are wound. In this case, to reduce the effect of eddy currents, a multilayer or otherwise configured core is used.

Closest to the proposed invention is an electric machine [2], containing a rotor having permanent magnets, and a stator having coils wound on stator rods to interact with magnets through an air gap defined between them, and the rotor is made to rotate relative to the stator around the axis of rotation, and the rods and coils on them are covered with an annular stator housing, and the stator housing contains two mating segments that fix the stator rods and coils in the machine, each stator rod has pole pieces at each end and each segment has parts of cylindrical walls on the inner and outer radii, and a radial wall connecting the parts of the inner and outer cylindrical walls, whereby the two segments mate between the opposing ends of the said parts of the inner and outer cylindrical walls, forming the said stator body, and in which the segments define a chamber throughwhich a cooling medium circulates around the coils to cool them.

Each rod is formed from at least two rod parts, connected to each other by transverse splitting along the cross section of the rod, and each segment is injection molded from reinforced plastics, being molded over the tips of one part of the stator rod to be held and located in the radial wall of the rod part whereby the pole pieces form part of said radial wall.

The disadvantage of the known machine is the high complexity of manufacturing and the sensitivity to the beating of permanent magnet rotors, due to the inefficiency of the cooling system, which leads to increased energy losses. In addition, the disadvantages of the known device are the complexity and cumbersomeness of the coil mounting system.

Brief summary of the essence of the invention.

In accordance with the present invention, there is provided an electrical machine comprising a stator housed in a ring-shaped casing and with pole-piece cores located at intervals around the circumference between the inner and outer connecting housings, forming a hollow space around the axis of the machine for circulation of coolant, on each of which a winding is wound, and two rotors mounted on the shaft with the possibility of rotation relative to the stator around the axis of the machine, each of which contains a set of constants magnets spaced at intervals around the circumference, the first rotor is located on one side of the stator at a distance from the pole pieces of the cores, forming an axial gap between the stator and the first rotor, and the second rotor is located on the opposite side of the stator at a distance from the pole pieces of the cores, forming between the stator and the second rotor is an axial clearance, and a set of permanent magnets of each rotor is located on its side facing the stator, characterized in that a flux-dividing ring is installed between the stator cores, which divides the stator hollow space into a space for liquid of the cooling winding and a space A compartment for collecting liquid with heat received from the stator windings, and each core is formed from at least two parts connected by the ends of the flow dividing ring.

According to the preferred and additional features given in the dependent items: inner and outer, relative to the stator cores, the connecting housings are cylindrical, hermetically fixed between the stator housings, which are installed on the mounting surface of the machine end shields; a flux-dividing ring, which ensures the redirection of the magnetic fluxes of the stator cores towards the gaps between the permanent magnets of the rotor and the stator cores, where the gap value is determined to be less than the set nominal gap value, while providing additional torque on the rotor due to small gaps (the torque is inversely proportional to the square of the gap); the flux-dividing ring by its surfaces is connected with the stator cores by the sides opposite to its pole pieces; the first contact surface of the rotor is located axially on the shaft, to determine the axial position of the first rotor, and the second contact surface of the rotor is axially separated from the first contact surface of the rotor, to determine the axial distance between the first and second rotors and to determine the axial air clearances between the first rotor and stator and the second rotor and stator; stator cores are made of soft magnetic iron-based composite powder;

An electrical machine is a motor or generator.

The invention is illustrated by drawings:

Figure 1 shows an electric machine with permanent magnets;

Figure 2 is a section along the axis of the engine and along the axis of the suction nozzle;

In Fig.Z - section A - A along the axis of the engine and along the axis of the injection nozzle;

Figure 4 is a section along the axis of the terminal box of the axis of the fittings: pumping and suction;

Figure 5 is a section along the axis of the engine and the terminal box;

Figure 6 is a diagram of the magnetic fluxes along the cores and the ring, between the windings and magnets;

Figure 7 is a section BB along the axis of the thicknesses of the permanent magnets;

The following symbols are used in these drawings:

1-bearing shield; 2-bearing shield; 3 - stator body; 4- stator housing; 5-outer connecting body; 6-inner connecting body; 7-winding; 8-core; 9-shaft rotor; 10- w / bearing; 11 - rotor; 12-rotor; 13 - permanent magnet; 14-ring of distribution of streams; 15-volume for the incoming coolant; 16-volume for liquid after collecting heat from windings and cores; 17-fitting for fluid supply; 18- connection for pumping out the heated liquid; 19-bearing cover; 20-shaft exit cover; 21 - sealing ring; 22-hairpin; 23 - a box of conclusions; Electric machine design:

The electrical machine consists of assembled shields of bearing housings 1 and 2 and stator 3 and 4, while stator 3 and 4 are connected by means of hermetically sealed connections with an outer connecting casing 5 and an inner connecting casing 6, forming a sealed space for the arrangement of windings 7 and cores 8. Shaft the rotor 9 is installed in the bearings 10 of the shields 1 and 2. On the shaft 9 are the rotor 11 and 12, with permanent magnets 13 built into them 13. Between the cores 8, with the windings 7, there is a flow distribution ring 14, which with its outer cylindrical surface with the body surface connecting outer 5, forms a volume for the incoming cooling liquid 15. The inner cylindrical surface of the ring 14 together with the outer cylindrical surface of the inner connecting body 6 forms a volume for the liquid after collecting heat 16. The volume 15 is connected with the nozzle 17, and the volume 16 with the nozzle 18. The liquid inlet 17 is installed on the outer connecting body 5 and connects the volume for the incoming coolant 15 with the outlet channel of the cooling unit (not shown in the figures). The nozzle for pumping out the heated liquid 18 is installed on the outer connecting body 5 and through the hole in the flow distribution ring 14 is connected to the volume for the liquid 16 after collecting heat from the windings 7 and cores 8. The nozzle 18 is connected to the inlet channel of the cooling unit (not shown in the figures) ... Bearings 10 are installed in shields 1 and 2 and are supports for shaft 9, which carries rotors 11 and 12 with magnets 13. Bearing caps 19 and shaft outlet cover 20 are mounted on shields 1 and 2, respectively.

The stator housings 3 and 4 of the electric machine are housings with sector recesses made along its perimeter and cores 8 fixed in the recesses with a similarly shaped working winding 7. Each flat end of the core on the rotor side is equipped with a pole piece in order to increase the area for the passage of the magnetic flux from the cores 8. Corresponding grooves are made in the housing, due to which the fixation of the cores 8 is provided, which makes it possible to increase the compactness of the electric machine.

Between the magnets 13 and the cores 8, there are air gaps "S" (Fig. 6). As is known from the theory of electric motor construction, the air gaps "S" should be as small as possible in order to reduce the reluctance in the magnetic circuit.

The design described allows a minimum air gap to be created with few manufacturing tolerances that can be agreed upon when assembling the engine. Since the bearings 10 represent a relatively significant source of idle movements in the axial direction, it is necessary to select the bearings 10 with small clearances or to adjust the relative position of the bearings 10 of the shields 1 and 2.

Of course, in the axial direction it is difficult to make the necessary fit. However, in addition to bearings, there are a minimum of other engine parts, the tolerances of which are imposed and require more air clearance "S". One of the important units is the rotors 11 and 12 themselves, which, with their end runout, significantly affect the size of the clearances "S". In addition, the general design principle of motors requires that the magnets 13 and windings 7 with cores 8 are located as far as possible from the axis of the shaft 9 of the rotors 11 and 12 so that the magnetosheating force acting between the cores 8 and the magnets 13 is converted into a maximum torque relative to shaft axes 9.

Since the flux distribution ring 14 is made of a composite, soft magnetic material (Fig. 6), the additional, shortest path of the magnetic flux is advantageous, since it reduces the requirement for limiting the magnetic flux itself and allows an alternative return path for each circuit: magnet 13 winding 7 - magnet 13. The total magnetic resistance reduces the energy consumption of the winding 7, which is closed along the minimum path.

To ensure the tightness of the connections of the outer connecting body 5 and the inner connecting body 6 with the stator bodies 3 and 4, rings 21 are installed.

The entire structure forming the motor, bearing shields 1 and 2, stator housings 3 and 4, connecting housings 5 and 6 are connected by pins 22. In addition, a terminal box 23 is installed on the stators housings 3 and 4 to connect the windings 7 with the engine control unit.

It should be noted that the axial force applied to each rotor is significant due to the magnets, and it increases if the air gap decreases, and can be on the order of 7500N per rotor. As a result, the axial support of the rotors is extremely important and thus the bearings 10 between stators 4 and 5 and rotors 11 and 12 will provide a rigid and reliable response to this force.

If the rotors are ideally located on both sides of the stator, then the axial force is zero, but this requires tight design tolerances and tight assembly of the bearings 10 to the shaft 9, which may require increased assembly costs.

As mentioned earlier, the flow distribution ring 14 and the cores 8 in the presented invention are made of a composite, soft magnetic material by powder metallurgy methods. In some versions, it is also permissible to combine and manufacture from electrical steel. Soft magnetic materials are used for a variety of applications such as core materials in inductors, stators and rotors for electrical machines, drives, sensors and transformer cores. Traditionally, soft magnetic cores such as rotors and stators in electrical machines are made from multilayer steel laminates. Soft magnetic composites can be based on soft magnetic particles, usually iron based, with an electrically insulating coating on each particle. Molding takes place by compacting isolated particles together with lubricants and / or binders using a traditional powder metallurgy process. Using this technology, such components can be manufactured with a greater degree of design freedom.

The present invention relates to the use of a soft magnetic iron-based composite powder, the particles of which are coated with a carefully selected coating that imparts material properties suitable for the production of motor stator cores. An inductor or core is a passive electrical component that can store energy in the form of a magnetic field created by an electric current passing through the component. The ability of inductors to store energy, inductance "L" is measured in Henry "H". Typically, an inductor is an insulated wire wound in a coil. The electric current flowing through the turns of the coil creates a magnetic field around the coil, the field strength being proportional to the current and the unit of turns (coil length). The alternating current will create an alternating magnetic field that will induce a voltage that opposes the change in the current that created it.

Ferromagnetic or iron core inductors use a magnetic core made of a ferromagnetic or ferrimagnetic material such as iron or ferrite to increase the inductance of the coil by several thousand by increasing the magnetic field due to the higher permeability of the core material.

The permeability, "P", of a material is a measure of its ability to carry magnetic flux or its ability to be magnetized. Permeability is defined as the ratio of the induced magnetic flux "B" and measured in newtons / amperes ^x meter or in volts ^x seconds / meter ² to the magnetizing force or field strength indicated by "H" and measured in amperes / meter (A / m). Therefore, magnetic permeability is measured in volts ^x second / ampere ^x meter. Usually, the magnetic permeability is expressed as the relative permeability cg = p / cO, relative to the permeability of free space, p0 = 4 ^x II ^x 10-7-Vs / Am.

One of the important parameters for improving the characteristics of the soft magnetic component is to reduce its core loss characteristics. When a magnetic material is exposed to an alternating field, energy losses occur due to both hysteresis losses and eddy current losses. The loss of hysteresis is proportional to the frequency of alternating magnetic fields, while the loss of eddy currents is proportional to the square of the frequency.

Thus, at high frequencies, the eddy current loss is of great importance, which must be taken into account in order to reduce eddy current losses and maintain a low level of hysteresis losses. This implies that it is desirable to increase the resistivity of the magnetic cores.

In search of ways to improve the resistivity, various methods have been used and proposed. These methods rely on the application of electrically insulating coatings or films to the powder particles before the particles are compacted. Currently, there are a large number of patent publications that describe various types of electrical insulating coatings.

The advantages of a composite, magnetic material over electrical steel are undeniable and provide the widest application in electrical machines with increased power density, especially with high rotation speeds, where electrical steel has large losses.

Electric machine operation.

When a sinusoidal voltage is applied to the windings 7 of the stators 3 and 4 of the machine in the cores 8, an electromagnetic field rotating relative to the axis of the shaft 9 of the rotors 11 and 12 appears with a frequency of supply from the power supply. The electromagnetic field through the working gaps between the cores 8 and permanent magnets 13 through the flow distribution ring 14 penetrates and interacts with the force fields of permanent magnets 13, providing the appearance of a torque on the rotors 11 and 12. The magnitude of the torque on the rotors 11 and 12 depends on the value of the current supplied to the windings 7. The number of revolutions of the shaft is 9 s rotors 11 and 12 depends on the frequency of the sinusoidal voltage applied to the stator windings 7 of the machine. As a rule, a high value of torque is required at low rotational speeds of shaft 9, and, therefore, currents of high values pass through the windings 7 with the result of heating the copper wires of the winding 7. Heat from the windings 7 is transferred to the cores 8, the stator housings 3 and 4 and into liquid in volumes 15 and 16, which, in general, causes a rise in the temperature of all parts of the machine. Heat, in accordance with the law of heat transfer, heats the liquid located in the volumes 15 and 16 and around the windings 7 and the ring 14. The liquid is constantly pumped by the pump of the cooling unit through the nozzles 17 and 18 through the volume for the incoming liquid 15 and the volume 16 for the liquid after collecting heat from windings and cores, where excess heat is then removed by the air flow from the fan of the cooling unit (not shown in the figures), thereby ensuring the temperature regime of the machine in the required range. When operating at high speeds of the rotors 11 and 12, the currents in the windings 7, as a rule, decrease and the heat fluxes from the copper resistive resistance of the windings 7 decrease, but due to an increase in the frequency of magnetic fluxes due to induction heating from the windings 7, the temperature of the cores 8 increases and rotors 11 and 12. Liquid in volumes 15 and 16 provides heat transfer from induction heating of cores 8. At the same time, an increase in heat flux from induction heating of cores 8 and flow distribution ring 14, with an increase in the rotational speed of the rotors, will cause an increase in the flow of coolant from the cooling unit and will reduce the increasing heat build-up in the material of the cores 8 of the ring 14.

The location of cavities with a volume for liquid in all stator housings 3 and 4 along the outer connecting body 5 and the inner connecting body 6 allows for the most efficient cooling both inside the most heating elements of the winding 7 and outside.

During operation (Fig. 6) in each core 8 there is a magnetic flux created by the windings 7. The magnetic flux is closed through the magnets, while crossing the gaps between the cores 8 and the magnets 13, where a shear force arises in accordance with Ohm's law, which creates a torque on the rotors 11 and 12, which is transmitted to the shaft 9 and is used for the intended purpose of the machine. In the proposed scheme, the magnetic fluxes of the opposing cores 8 are added, crossing the flux distribution ring 14. The scheme operates at nominally identical working clearances (Sa = Sd = Sb = Sg).

However, due to errors in assembly, manufacturing of rotors, temperature deformations, the gaps between the cores 8 and the magnets 13 within one revolution of the shaft 9 may change. The size of the gap affects not only the magnitude of the resistance to magnetic flux, but also determines the amount of torque on the shaft. As a result, with an increase in the gap, the resistance to the magnetic flux increases and, in addition, the value of the created torque on the shaft 9 decreases, and with a decrease in the gap, the resistance to the magnetic flux created in the cores decreases, but the value of the created torque on the shaft 9 increases.

Thus, due to the location of the flux dividing ring 14 between the cores 8, we obtain the ability to control the magnitude of the magnetic fluxes through the gaps.

The clearances (Sb + Sg) are larger than (Sa + Sd). Magnetic fluxes from both cores "F1" and "F3" intersect (Sb + Sg) and (Sa + Sd), and the flux from cores "F2 and" F4 ", due to the low resistance to fluxes, will be closed through the material of the ring 14 with the result of additional creation of a torque moment on shaft 9 due to a short circuit (low resistance to magnetic flux).

Conclusion: With inequalities in the values of the gaps, the cores closest to the gaps will close through the ring 14 and the smaller adjacent gaps, which will reduce the energy consumption of the cores as a result of an increase in the torque on the shaft 9 from this group of cores. The torque on the shaft 9 is inversely proportional to the square of the clearance. This result is obtained as a result of increased flow with low resistance to the small circle flow itself.

When starting synchronous motors, to which this electric machine, made according to the invention belongs, the starting current in the stator winding increases 5-7 times compared to the nominal. With prolonged operation in this mode at low or close to zero speed, strong overheating of the windings occurs until the engine fails.

The proposed invention, due to the effective intensive cooling of areas with a high concentration of thermal energy and reduced losses of magnetic fluxes of the cores, will increase the power and torque of an electric machine for use when operating at low speeds with a long duration of starting loads.

The invention relates to the field of electrical engineering and concerns the execution of electrical machines filled with a coolant, mainly synchronous motors, and can be used in the electric drive of systems with a long duration of starting loads when operating at low speeds, for example, in transport equipment, generating equipment for hydro and wind installations.

The electric car can be used to drive all-electric and hybrid vehicles.

The purpose of the invention is to simplify the design and improve the quality of cooling of the windings and cores, reduce the losses of magnetic fluxes with a decrease in thermal losses of the motor as a whole.

The technical result is an increased specific power and specific torque of an electric machine. Ensuring its operation at the same time both at a low number of revolutions with a long duration and frequent repetition of starting loads, and at a high number of rotor revolutions by efficient cooling of actively heating elements of an electric machine in the entire range of possible rotor revolutions.

Links

[1] TJ Woolmer and MD McCulloch "Analysis of the Yokeless and Segmented Armature Machine", International Electric Machines and Drives Conference (IEMDC) International Electric Machines and Drives Conference (IEMDC), 3-5 May 2007;

[2] RF Patent 2551844 C2

Claims

Claim.

1. An electrical machine containing a stator placed in a ring-shaped housing with cores with pole pieces, which are located at intervals around the circumference between the inner and outer connecting bodies, forming a hollow space around the machine axis for circulation of coolant, on each of which a winding is wound, and two rotor mounted on the shaft with the possibility of rotation relative to the stator around the machine axis, each of which contains a set of permanent magnets spaced at intervals around the circumference, the first rotor is located on one side of the stator at a distance from the pole pieces of the cores, forming an axial gap between the stator and the first rotor , and the second rotor is located on the opposite side of the stator at a distance from the pole pieces of the cores, forming an axial gap between the stator and the second rotor, and a set of permanent magnets of each rotor is located on its side facing the stator, characterized in that between the cores and a stator, a flow-dividing ring is installed, which divides the stator hollow space into a space for liquid in the cooling winding and a space for collecting liquid with heat received from the stator windings, each core being formed from at least two parts connected by the ends of the flow-dividing ring.

2. An electric machine according to claim 1, wherein the inner and outer, with respect to the stator cores, are cylindrical connecting housings, hermetically fixed between the stator housings, which are mounted on the mounting surface of the machine end shields.

3. An electric machine according to claim 2, comprising a flux-dividing ring, which redirects the magnetic fluxes of the stator cores towards the gaps between the permanent magnets of the rotor and the stator cores, the gap value is determined to be less than the specified nominal gap value, while providing additional torque on the rotor due to small clearances (torque is inversely proportional to the square of the clearance).

4. The electric machine according to claim 3, in which the flux-dividing ring is connected by its surfaces with the stator cores by the sides opposite to its pole pieces. ^ ί? .1 (n7 _m 1 / weight machine according to any of pi. 1-4, in which _{ ? h £? d ^ 91? R? ⁵ l ^ the active surface of the rotor is located in the axial direction on the shaft, to determine the axial the position of the first rotor, wherein the second rotor contact surface is axially separated from the first rotor contact surface, to determine the axial distance between the first and second rotors and to determine the axial air gaps between the first rotor and stator and the second rotor and stator.

6. Electric machine according to any one of paragraphs. 1-5, in which the stator cores are made of a soft magnetic iron-based composite powder.

7. Electric machine according to any one of paragraphs. 1-6 represents an engine or generator.