The invention relates generally to electric machines for energy conversion, and more particularly to generators and motors having low inductance in the armature circuits of an electric machine. The claimed contra-rotating synchronous electro-mechanical converter (hereinafter referred to as the“converter”) can be used in counter-rotating wind turbine systems, flywheel kinetic energy storage systems, and the like. In the preferred embodiments of the present invention, the converter can have a topology of a flux switching machine which can be a flux switching permanent magnet (FSPM) machine. Such machines can function as motors and/or generators and the like. The converter of the subject invention can also be designed as a synchronous motor or generator or a series-connected motor and generator. In this case, the converter can be used, for example, as a wheel drive in an electric vehicle and/or to regenerate energy during braking.

Background of the invention

Modern applications of electric machines include the use of energy converters, electric motors and generators in particular, which provide an increase in the flux density of electromagnetic energy and operating efficiency due to the use of high coercive force permanent magnets. The use of such permanent magnets reduces the amount of copper in the excitation windings of converters, thereby reducing the total current losses in converters. Replacing coils with permanent magnets changes the design of electric machines. When using permanent magnets, the field of the permanent magnets cannot be“turned off’, which leads to an increase in the height of the rotor teeth needed to start the converter. The constant magnetic flux also causes the motor’s back electromotive force to become linear with speed, resulting in a linear speed to torque relationship, which reduces the converter efficiency.

Most of the approaches to control the efficiency at peak power output for permanent magnet converters have been directed toward electronically controlling the phase excitation angles and current. Such electronic control is effective for modifying the linear speed to torque relation to produce a more hyperbolic speed to torque relationship, but requires increasing the size and ultimately the weight of the converter. In particular, the size and weight of converters is increased to the size and weight of converters using copper windings, which negates the benefits of using permanent magnets in converters.

Description of the prior art

In electric machines, such as motors or generators, internal resistance is an important parameter, together with the total internal resistance of the load, needed to determine the entire system performance. Since the internal resistance of an electric machine is less than the total internal resistance of the load, the output voltage in an electric machine becomes greater than the voltage loss in an EMF source. In the known technical solutions, to ensure the shortest path of resistance in copper windings of an electric machine, a minimal internal resistance and minimization of the power and heat losses are ensured with the heat carried away from the electric machine and dissipated.

In contrast, in the case of a negligible internal inductance, the output voltage will increase as the current frequency is increased due to an increase in the flux change over time. The levels of excitation current can then be reduced by increasing the current frequency, thus avoiding a saturation phenomenon in the electric machine. A decrease in current excitation will compensate for an increase in the current frequency so that the stator core losses will remain almost unchanged. Flux switching machines (FSM) belong to the class of doubly-salient permanent magnet (DPSM) machines described, for example, in the article of A. Mahmoudi*, N.A Rahim and W.P Hew, Axial-flux permanent-magnet machine modeling, design, simulation and analysis, Scientific Research and Essays Vol. 6(12), pp. 2525-2549, publication date June 18, 201 1, available at http://www.academicjoumals.org/SRE. Existing flux switching machines show some disadvantages, including relatively low torque density compared to other permanent magnet machines.

Such disadvantages are described, for example, in US 20140049124 Al , publication date February 20, 2014. This application describes a permanent magnet machine, similar to the claimed electric machine (converter). The converter has two rotors rotating in the same direction. A disadvantage of this machine is possible relatively large magnetic induction losses on the rotors, as evidenced by the diagram in Fig. 2 to the description of the said application. In addition, a similar machine is relatively heavy due to the use of heavy steel rotors.

There is also a rotary electric machine comprising a stator and two rotors described in US20060175923 Al, publication date August 10, 2006. An external rotor is radially arranged outside the stator. An internal rotor is radially arranged inside the stator. The external and internal rotors are provided with permanent magnets and rotate synchronously in the same direction, in contrast to the claimed converter which has rotors with synchronous counter-rotation.

Converters, similar to the mentioned above, are also described in the article of Morenko, K.S. Bi-rotor electric generators for the wind sets / Morenko K. S., Stepanchuk G.V. // Don Agrarian Science Bulletin. - Zemograd: FGBOU VPO AChAA, 201 1. - No.2(14), pp. 66-73. The article describes dual-rotor doubly- fed generators. Disadvantages of similar converters are described above and are eliminated by converters having both rotors counter-rotating in synchronism.

There is also a converter (motor) described in an international application WO 2008/096600, publication date August 14, 2008. The motor comprises a stator having the first and second armatures to form a rotating magnetic field and an internal rotor having the first and second permanent magnets, and an external rotor is arranged between the stator and the internal rotor. The external rotor comprises a rotor body for supporting the first and second dielectric magnetic poles made of a magnetically soft material so that they are inserted into the rotor body. The first dielectric magnetic poles and the second dielectric magnetic poles are aligned in phase. The first and second magnetic dielectric poles are inserted into the rotor body so that they are arrayed in the direction of a common axis of rotation of the converters. Due to biaxial rotation, the external rotor is not only simplified in structure to improve its strength and reliability, but also facilitated in support or assembly by the first and second dielectric magnetic poles in the external rotor. However, the described analogue does not provide for synchronous counter rotation of the external and internal rotors either.

There is also a contactless bi-rotating electromechanical converter described in patent RU 166023 Ul , publication date November 10, 2016. The converter comprises a stator with a magnetic circuit that has a multi-phase ring winding, and two inductor-rotors comprising permanent magnets. The rotors are arranged separately, with the possibility of independent rotation, that is, rotation at different speeds, in contrast to the proposed converter, which is a synchronous machine.

There is also a converter (motor) described in US 6,455,969 B1 , publication date September 24, 2002. The motor comprises a stator, a middle hold down layer, an external rotor and an internal rotor. These rotors comprise the same number of permanent magnets to form a magnetic field and are displaced relative to each other. The stator comprises a plurality of excitation coils the number of which is equal to the number of rotor magnets. The rotors are rotated in opposite directions by supplying polyphaser alternating current to the stator excitation coils. A disadvantage of the described converter is a relatively long magnetic flux path (Fig. 3 and 4) as well as large dispersion fields and magnetic resistance of the converter. An electro-mechanical converter, a hybrid permanent magnet rotor, described in US 20090160391 Al, publication date June 25, 2009 was chosen as a prototype of the present invention. A converter under the prototype can function as a generator and comprises a rotor having a plurality of magnetic poles arranged about a central axis of rotation, a stator including a plurality of stator segments separated by an air gap, each of which has at least two oppositely charged poles, said stator also including a plurality of permanent magnets, each of which has at least two oppositely charged poles and is positioned between a different pair of adjacent stator segments in the magnetic field between the control coils. The control coils are energized to create a flux opposing the flux of the permanent magnets and to create a rotational torque on the rotor poles before those poles align with the poles of the energized control coil stator segment. The permanent magnets on the stator segments are serially arranged along the magnetic flux path. When the current does not flow in the phase windings, this allows the converter to be controlled through the phase windings. In the operation of the described converter, a small amount of the magnetic flux leaks. Such an arrangement of magnetic fluxes in the immediate vicinity of leakage fluxes, inherent in compact multipolar machines, reduces the efficiency of the converter.

Summary of the invention

The basic concept of the invention is the problem of simplifying an electro mechanical converter in design simultaneously increasing the reliability of its operation by modifying the stator and rotor design. An additional advantage of the invention is that it increases the power density and efficiency of the converter in general by applying the parallel flow method in the construction scheme of magnetic circuits of the converter to ensure low inductance and by increasing the frequency of electromotive force (EMF) generated by the converter. Another additional advantage of the invention is that it provides for synchronous rotation of the rotors. The problem is resolved in such a way that the known contra-rotating synchronous electro-mechanical converter that includes a rotor having a plurality of induction poles arranged about a central axis of rotation, a stator that includes a plurality of segments separated by an air gap, each of which has at least two oppositely charged poles, and a plurality of permanent magnets, each of which has at least two oppositely charged poles and is positioned between a different pair of adjacent stator segments according to the invention, the rotor includes at least the first rotor and the second rotor positioned on both sides of the stator, both rotors synchronously rotating about the central axis in opposite directions, the first rotor and the second rotor are composed of a nonmagnetic material, and a plurality of induction poles are composed, at least partially, of a magnetically soft material and are arranged on the first rotor and on the second rotor circumferentially with certain intervals between the poles, and a control coil and an AC induction coil are wound on each stator segment, wherein a plurality of permanent magnets are arranged between the stator segments on a circle that circumscribes the magnetic flux of the stator.

In a preferred embodiment of the present invention, the poles of the first rotor can be displaced from the poles of the second rotor by half a pole pitch.

In another preferred embodiment of the present invention, a plurality of switches composed of a magnetically soft material, arranged about a central axis of rotation can be used as the poles of the first rotor and the second rotor.

In yet another preferred embodiment of the present invention, a plurality of switches can be arranged on a disc composed of a nonmagnetic material.

In yet another preferred embodiment of the present invention, the first rotor and the second rotor can have a serrated surface.

In yet another preferred embodiment of the present invention, teeth of the first rotor can be combined with teeth of the second rotor and vice versa within one stator segment. In yet another preferred embodiment of the present invention, the control coils are connected in series, and the AC induction coils are connected in series in such a way that they form at least two, first and second, parallel branches.

In yet another preferred embodiment of the present invention, each of the permanent magnets composed of a magnetically hard material and placed adjacent to and between each of the stator segments composed of a magnetically soft material to form a continuous ring and in a manner where their magnetic poles are opposing.

In yet another preferred embodiment of the present invention, each stator segment can be H-shaped forming teeth on the upper side of the stator and on the lower side of the stator.

In this case, the teeth on the upper side of the stator and on the lower side of the stator can form segmented ring-shaped pole pieces with control coils and AC induction coils wound on them. Also in this case, the upper side of the stator and the lower side of the stator can have 6n teeth and each rotor has 6n±2 poles, where n is < 2.

In yet another preferred embodiment of the present invention, synchronous rotation of both rotors in opposite directions about the central axis can be enabled by a counter-rotating means. In such a case, said counter-rotating means can be arranged as a mechanical counter-rotating device or as an electronic counter-rotating means.

In this case, a planetary gear reducer having a gear ratio i = -1 connected to the first rotor and the second rotor can be used as a mechanical counter-rotating device.

Also in this case, a controller equipped with sensors for tracking the position of the rotors for switching the control coils can be used as an electronic counter rotating means. In yet another preferred embodiment of the present invention, the first rotor and the second rotor are equipped with the same number of switches displaced angularly relative to the control coils and the AC inductive coils.

For the solution of the problem according to the subject invention, an electro-mechanical device with permanent magnets, namely a contra-rotating synchronous electro-mechanical converter that functions as a motor and as a generator, is provided.

The converter features a plurality of control coils and AC induction coils (phase coils) needed to collect energy in the generator mode. The converter includes a plurality of permanent magnets (at least two) arranged on the stator, bearings and structural components and a novel contra-rotating means which can be made as a mechanical counter-rotating device or as an electronic counter rotating means. The parallel flow method applied in the construction of magnetic circuits (magnetic flux paths) according to the invention increases the converter power density nearly twofold compared with conventional converters.

Advantageously, the use of separate coils (control coil and AC induction coil) wound on each stator segment, simplifies the converter in design and increases reliability of its operation in contrast to distribution windings as in similar structures from the prior art.

Moreover, the stator does not have a fixed yoke which serves only as a skeleton for mounting pole pieces and is an obstacle in the path of the magnetic flux and is a source of significant losses in iron. The absence of yoke advantageously eliminates these losses and significantly improves the efficiency of the converter, especially at high rotational speeds of the rotors.

Design of a rotor comprising at least a first rotor and a second rotor that are arranged on both sides of a stator and are rotated synchronously about the central axis in opposite directions (counter-rotating scheme) makes it possible to almost double the torque per unit volume compared with a converter having one rotor. Two rotors, which in the process of the converter operation change the position of their switches relative to the stator magnetic poles and are displaced relative to each other due to H-shaped stator segments, reduce a pole pitch and ultimately increase the converter efficiency. In the preferred embodiments of the present invention, the converter can have a topology of a flux switching machine which can be a flux-switching permanent magnet (FSPM) machine. This enables others skilled in the art to utilize such machines as motors and/or generators.

Placement of each of the permanent magnets composed of a magnetically hard material adjacent to and between each of the stator segments composed of a magnetically soft material to form a continuous ring and in a manner where their magnetic poles are opposing, and their placement between H-shaped stator segments about a central axis of rotation on a circle that circumscribes the magnetic flux of the stator makes it possible to increase the converter torque and ultimately its power density. Testing of the converter according to the subject invention as a motor confirmed an increase in the torque more than by 40% compared to conventional flux-switching devices.

Utilization of two rotors (the first rotor and the second rotor) rotating in opposite directions and equipped with a plurality of switches composed of a magnetically soft material makes possible providing magnetic flux modulators arranged on a disc composed of a nonmagnetic material and rotating about a central axis of rotation which enables collection of output power separately from the first rotor and from the second rotor and from the AC induction coils.

The converter according to the subject invention provides little cogging forces, high efficiency operation, and a high magnetic flux density (magnetic flux per area of the magnet gaps). Due to the above-described rotor and stator pole geometries and spacing relationships the converter can be arranged to operate as either a single-phase and multi-phase generator and/or motor. Each stator segment has an H-shape forming segmented ring-shaped pole pieces with control coils and AC induction coils positioned on them which enables providing wedge-shaped magnets of the first rotor and the second rotor relative to the central axis of rotation, with a wedge-shaped width which increases as the distance from the stator grows. Such shape of magnets enables rotation of the pole pieces of the stator with a high speed of rotation of the rotor parts without the need for additional fastening of the magnets, which simplifies the design of the converter and increases the reliability of its operation.

In one of the preferred embodiment of the present invention, the converter includes a contra-rotating means for providing synchronous rotation of the first rotor and the second rotor. Such means can be arranged as a mechanical gear with a gear ratio i = -1 or as a differential gear with a fixed central gear or as a planetary gear or epitrochoidal gear with intermediate bodies or anti-rotation gear shown in FIG. 2. Alternatively, synchronization of the first rotor and the second rotor can be implemented using a controller equipped with rotor position sensors for switching control coils in the converter, for example, Hall Effect sensors for sensing the rotation angle of each rotor.

Placement of 6n teeth on the upper side of the stator and the lower side of the stator and provision of each rotor with 6n±2 poles, where n is < 2 makes it possible to increase the winding factor which shows the level of efficiency of the winding use and evidences greater efficiency of operation and compactness of the converter. The described configuration is most appropriate when each stator tooth is a core for the winding holding one separate control coil or an AC induction coil (“concentrated winding”).

Brief description of the drawings

The claimed invention is illustrated by the following example of embodiment of the converter, its operation and the achievement of technical result, and by the following drawings: Fig. 1 is a general view of a converter with a partial sectional view in accordance with an embodiment of the present invention;

Fig. 2 is a diagram illustrating a longitudinal section of the converter in accordance with an embodiment of the present invention; Fig. 3 is a diagram illustrating a cross-section of the converter with a radial magnetic flux in accordance with the second embodiment of the present invention;

Fig. 4 is a diagram of open circuited lines of magnetic fluxes of the converter in its cross section in accordance with an embodiment of the present invention; Fig. 5 is a fragment of calculation of lines of magnetic fluxes in a 3D Id- shaped two-pole stator with upper and lower switches at the moment of maximum magnetic induction, view from the outside of the stator;

Fig. 6 is a fragment of calculation of lines of magnetic fluxes in a 3D H- shaped two-pole stator with upper and lower switches at the moment of maximum magnetic induction, view from the lower switch side;

Fig. 7 is a general view of an axial (edge-bonded) converter constructed with a stator and two rotors in accordance with an embodiment of the present invention.

Foregoing examples and drawings have been presented for purposes of illustration and description and are not intended to be exhaustive or to limit the number of possible embodiments of the invention according to the above mentioned features.

Detailed description of the invention and its embodiments

In accordance with an embodiment of the present invention, a contra rotating synchronous electro-mechanical converter can be designed as a flux- switching permanent magnet (FSPM) synchronous generator (Fig. 1). For illustrative purposes, said generator is shown single-phase and 48-pole, but it should be understood that there is no limit to the number of magnets and to the number of poles.

The generator includes a stationary stator 1 and a rotor comprising a first rotor 2 and a second rotor 3 positioned on both sides of the stator 1. The first rotor 2 and the second rotor 3 are made of nonmagnetic material and rotate synchronously about a central axis 0-0 in opposite directions.

The first rotor and the second rotor comprise a plurality of induction poles made as switches 4 and 5 and arranged about the central axis of rotation 0-0. The induction poles 4 and 5 are composed of a magnetically soft material and are arranged on the first rotor and on the second rotor circumferentially with certain intervals.

A stator 1 comprises ferromagnetic H-shaped segments 6 and permanent magnets having N poles 7 and permanent magnets having NS poles 8 designed to create the main magnetic field of the converter. In one aspect, the stator 1 can includes 24 H-shaped segments that form teeth on the upper side of the stator 1 and on the lower side of the stator 1. In this case, the total number of teeth of 6 H- shaped segments is 96, with 48 teeth on the upper side and on the lower side of the stator 1. Each stator segment 6 is separated by an air gap and has at least two oppositely charged poles 9 and 10. Each of the permanent magnets 7 and 8 is positioned between a different pair of adjacent segments 6 of the stator 1.

Each of the permanent magnets 7 and 8 composed of a magnetically hard material are placed adjacent to and between each of the stator segments 6 composed of a magnetically soft material and the poles of the permanent magnets 7 and 8 are arranged in an N-S-N-S manner.

Copper control coils 1 1 are designed to switch a magnetic flux and AC induction coils 12 and 13, where EMF is induced, are wound on the teeth of each segment 6 of the stator 1. The teeth have a segmented ring-shaped form formed by the H-shaped segments 6.

Alternatively, the teeth can have two opposite parts of the stator 1 directed to the first rotor and to the second rotor, respectively. In this case, the teeth of the stator 1 are made without pole pieces, thereby allowing mounting of individual coils by their engaging with the H-shaped teeth of the stator 1. In this case, the coils are made separately.

The control coils 1 1 of all segments 6 of the stator 1 are connected in series in the amount of 96 coils, according to an embodiment of the present invention. The AC induction coils 12 and 13 are connected in series in such a way that they form at least two parallel branches, 48 coils in each branch, according to an embodiment of the invention.

All the above mentioned coils can be composed of any suitable material known from the prior art. For example, the coils can be made of copper, although embodiments of the invention are not limited to the said material.

The segments 6 are separated from each other by an air gap and are held by an inner diamagnetic disk 14 and an outer diamagnetic disk 15.

The stator 1 can have a modular structure that simplifies its manufacture. Each such module can include several segments 6 and be made of a magnetically soft material (for example, sheet molding compound (SMC)) or silicon steel with a built-in magnet (for example, PM), and the coils 1 1, 12 and 13 can be wound around a material with a built-in magnet.

Each phase of the converter can have one or more control coils 1 1 and AC induction coils 12 and 13. Where the stator 1 has a modular structure, the number of modules is determined by the number of turns of the coils multiplied by the number of phases in the converter. In this case, the inverse EMF is sinusoidal, even if the windings of the above-mentioned coils are concentrated and their connection circuit is open if the converter is arranged as a three-phase electric machine. In general, the stator 1 may well be positioned inside a nonmagnetic material, such as, for example, epoxy resin or aluminum.

Permanent magnets 7 and 8 are arranged between the stator segments 6 on a circle that circumscribes the magnetic flux of the stator 1. The permanent magnets 7 and 8 can be made of any suitable material known from the prior art, for example, of neodymium boron ferrite (NdFeB) or aluminum alloy, nickel and cobalt (Alnico), although embodiments of the invention are not limited to these materials. In the described embodiment, the permanent magnets 7 and 8 are made of NdFeB-30 (neodymium iron boron). According to the above-mentioned embodiment of the present invention, the number of magnets in the upper and in the lower part of the stator 1 is 24.

Induction poles 4 of the first rotor 2 are displaced from induction poles 5 of the second rotor 3 by half a pole pitch. The first rotor 2 and the second rotor 3 have a serrated surface, i.e. the first rotor 2 has teeth 16 and the second rotor 3 has teeth 17. Teeth 16 are combined with teeth 17 and vice versa within one H-shaped segment 6 around a circle.

Each of the first rotor 2 and the second rotor 3 comprises an equal number of switches 4 and 5 composed of a magnetically soft material that are displaced angularly relative to the control coils and the AC inductive coils in a manner that they are able to rotate about the central axis of rotation 0-0 on a disc composed of a nonmagnetic material of the rotor 2 and the rotor 3. In a preferred embodiment of the present invention, each of the rotors 2 and 3 has 12 ferromagnetic switches 4, 5.

The rotors 2 and 3 rotate in opposite directions for rotational velocity addition and elimination of the effect of torque. Synchronous rotation of the first rotor 2 and the second rotor 3 about the central axis 0-0 in opposite directions can be enabled by a counter-rotating means arranged, for example, as a mechanical counter-rotating device 18. In this case, a planetary gear reducer having a gear ratio i = -1 connected to the first rotor 2 and the second rotor 3 can be used as a mechanical counter-rotating device.

A counter-rotating means can also be arranged as an electronic counter rotating means, for example, as a controller equipped with sensors for tracking the position of the rotors 2 and 3 for switching the control coils 1 1.

The principle of operation of the above-described converter according to the subject invention is based on the pulsed switching of the direction of the magnetic field depending on the position of the switches 4 of the first rotor 2 (magnetic lines 19 in Fig. 4) and the switches 5 of the second rotor 3 (magnetic lines 20 in Fig. 4) relative to magnetic poles of the stator 1. Permanent magnets 7 and 8 create the main magnetic field of the stator 1. Switches 4 and 5 of the first rotor 2 and the second rotor 3 move in opposite directions and interact with the main magnetic field of the stator 1. Once an axis 21 of the pole of the stator 1 has rotated into alignment with the switches 4 and 5, a current pulse is applied to the control coils 1 1 (as shown in the lower part of Fig. 4). When this happens, the magnetic field is displaced into the switch 5. Thus, magnetic circuits 22 are created which pass through the switches 4 and 5.

Upon further movement of switches 4 and 5, the magnetic circuit breaks causing induction of back EMF in the AC induction coils of the first branch 12. At the same time, the EMF is zero in the AC induction coils of the second branch 13. Once the magnetic axis 21 of the switch 5 aligns with the next magnetic pole of the stator 1 , a pulse is applied to the control coils 11 having an opposite polarity. The direction of lines of magnetic fluxes is reversed. The movement of switches 4 and 5 breaks the magnetic circuit 22 of the stator 1 and back EMF is induced in the AC induction coils of the second branch 13, the EMF is zero in the AC induction coils of the first branch 12. In the coils 12 and 13 of the first and second branches, the EMF is alternately induced from 0 to the maximum value.

Since the movement of the switches causes a sinusoidal dependence of displacement of the magnetic field, induction of back EMF in the coils 12 and 13 and is a sinusoidal AC voltage. EMF in the coils 12 and 13 of the first and second branches is displaced by 90 electrical degrees.

When using the converter as a generator, each of the rotors can be mounted on a shaft 23 of the wind turbine.

Alternatively, the teeth on the upper side of the stator 1 and on the lower side of the stator 1 can form segmented ring-shaped pole pieces with control coils 1 1 and AC induction coils 12 and 13 wound on them.