The present invention describes an electric rotary machine and a method of operation of the electric rotary machine. The electric rotary machine uses electric currents and magnetic materials to convert electric and mechanical energy. Two particular embodiments: three-phase and single-phase are presented.

The purpose of this invention is to come up with a structure and method of operation of a brushless and exciter-free electric rotary machine, whose stator windings can be directly connected to an AC electric power supply of constant angular velocity, like for example 50Hz grid, and the rotor can spin at any angular speed, still reaching close to 100% efficiency. In the state-of the art machines, brushes or an exciter are installed and used to transfer power to or from rotor windings, where brushes are means to directly contact rotor windings from stator and exciter is a contactles device for transfering power to or from rotor. Here we are looking for an electric rotary machine that has no means for tranferring electric power to or from rotor windings other than rotor and stator windings.

The solution is to install a rotor controller on the rotor: connect terminals of rotor windings through rotor power switches to a rotor DC supply and control currents in rotor windings in order to generate at least two magnetic fields rotating at different angular velocities, such that power transfer between rotor windings and rotor DC supply can be balanced.

The major advantages of the disclosed here electric rotary machines and control methods are:

- the rotor of the electric rotary machine doesn't need any brushes, exciters nor any extra elements to transfer electrical power to the rotor, other than rotor windings.

- the terminals of stator windings can be directly coupled to AC electric power supply and if the AC electric power supply is a high or medium voltage supply (above 10kV), there is no need for expensive electronic switches that have to withstand the high voltage of the supply network. Stator can even be connected to such a high voltage supply, for what electronic switches are not available and that eliminates the need of a voltage-reducing transformer that is normally inserted between AC electric power supply grid and the rotary machine.

- the electric rotary machine can rotate at broad range of angular speed, can easily change direction, or mode of operation: generator, or motor, still being supplied from the same AC electric power supply, whose magnitude and frequency is constant. Electric machines disclosed here can also rotate at larger angular velocity than the angular velocity of the supply network WS.

BRIEF DESCRIPTION OF THE DRAWINGS

Further understanding of various aspects of the invention can be obtained by reference to the following detailed description in conjunction with the associated drawings, which are described briefly below. Preferred exemplary embodiments of the subject matter of the invention are described below in conjunction with the attached drawings.

Fig. 1 presents a schematic structure of disclosed electric rotary machine.

Fig. 2 presents a phasor diagram and power transfer diagram for understanding of basic notions

Fig. 3a presents a phasor diagram and power transfer diagram to explain method of operation of the electric rotary machine in motor mode. Fig. 3b presents a phasor diagram and power transfer diagram to explain method of operation of the electric rotary machine in generator mode.

Fig. 4 presents a schematic setup of an arrangement of two electric rotary machines for cancellation of an injection of asynchronous current into a supply grid

Fig. 5 presents a phasor diagram and power transfer diagram to explain method of operation of the setup according to Figure 4.

Fig. 6 presents a schematic setup of an arrangement of two electric rotary machines, wherein the first one is connected to an AC electric power supply and the second one has it's stator windings shorted.

Fig. 7 presents a phasor diagram and power transfer diagram to explain method of operation of the setup according to Figure 6.

Fig. 8 shows a schematic setup of a single-phase version of the electric rotary machine.

Fig. 9 shows the phasor diagram and power transfer diagram to explain method of operation of the single-phase electric rotary machine according to Fig. 8.

Fig. 10a presents a schematic structure of a setup with three single-phase electric rotary machines connected in delta arrangement to three-phase AC electric power supply, while Fig. 10b presents a setup with three single-phase electric rotary machines connected in star arrangement, connected to three- phase AC electric power supply. DESCRIPTION

For best understanding the present invention, we will define notions used in claims that are related to the structure of disclosed electric rotary machine.

The setup of rotary machines comprising a stator (1) and a rotor (2,) where the stator (1) further comprises a stator core made of soft magnetic material and at least one stator winding (3) made of conductive material and the rotor (2) comprises a rotor core made of soft magnetic material and plurality of rotor windings (6) made of conductive material. Since during operation, here magnetization of rotor (2) and/or stator (1) can change, in order to minimize power losses, both stator and rotor cores are made of soft magnetic material, whose coercivity is below 100 A/m. Different geometrical arrangements of the electric rotary machine are covered by this invention: axial and radial with outer, or inner rotor.

Rotor windings (6) and/or stator windings (3) contain certain number of loops of wire, or tape, or rod, or other shape, made of an electrically conductive material like for example copper or aluminium and wound around parts of rotor or stator core. Different geometrical arrangements like cylindrical or salient pole windings are possible, but preferred and typical are cylindrical windings. In a typical case number of stator windings (3) and rotor windings (6) is three, but the disclosure is not limited to this particular number and also number of stator windings (3) doesn't need to be equal to the number of rotor windings (6). Every winding has two terminals (7), (14) which can be electrically connected to each other, or to further components. In many cases, terminals of stator windings (14) or rotor windings (7) can be connected to other terminals of other windings and arranged in a known star or delta connection. In an arrangement of plurality of machines (M1), (M2),..., particular terminals of stator windings (14) of one machine (M1) can be connected to corresponding terminals of stator windings (14) of another machine (M2), so (M1) and (M2) are connected in parallel. Finally, the two terminals of a winding (7), (14) can be shorted by a low-resistive connection between them.

The electric rotary machine disclosed here is supposed to be connected to an AC electric power supply (4), whose angular frequency WS and voltage magnitude is defined. Typically, it is a widely available three-phase supply grid, output of a transformer, output of an inverter, or one-phase supply, but the disclosure in general is not limited to those cases. The AC electric power supply (4) can be electrically coupled to terminals of stator windings (14) either directly, or through a switch unit (5) comprising a plug, or mechanically- controlled switch, or relay, or electric fuse, or other electrical switching component, or combination of above mentioned switching components, wherein during steady-state operation of the electric rotary machine, the connection is not supposed to change: terminals of stator windings (14), that are electrically connected to particular phases of AC electric power supply (4) remain connected and terminals that are disconnected remain disconnected. The switch unit (5) might be used to connect or disconnect the electric rotary machine to the AC electric power supply (4), or perform a safety function, or to change configuration of what terminals of stator windings (14) are connected to what phases of AC electric power supply (4).

The rotor (2) comprises a rotor controller (8), wherein rotor switches (9) are used to connect terminals of rotor windings (6) to different terminals of rotor power supply (11) and the rotor switches (9) directly control electric currents of rotor windings (6). There are different types of known devices that can be used to implement rotor switches (9), like: MOS power transistors (13), BJT transistors, IGBT transistors and others. Whatever type of device is used, it has to be able to conduct desired currents of rotor winding in the on-state, withstand voltages induced in rotor windings in the off-state and switch on and off at significantly faster rate than the frequency of AC electric power supply (4). Typically required switching frequencies of rotor switches (9) are between one kHz and tens of kHz range. Very often a rotor switch (9) comprises a diode that always allows current flow in one direction. In some cases the diode is a inherent part of the rotor switch - for example in case of MOS power transistors, or the diode might be a separate device extra added - for example in case of an IGBT transistor.

The switch driver (10) function is to deliver control signals: in electrical or optical form, to each of rotor switches (9) in that way controlling electrical conduction of rotor switches (9). The function of switch driver (10) might also include performing necessary calculation or regulation or signal-processing tasks in order to determine control signals to rotor switches. To facilitate this task, the switch driver (10) might contain known and available on the market components like inverter drivers, micro-controllers etc. It is also possible that part of switch driver (10) functionality is implemented on the same physical component together with rotor switches (9). The operation of the switch driver (10) might be controlled by software.

The rotor power supply (11) function is to provide electric power supply to rotor switches (9). It might also power the switch driver (10) or farther components of the rotor that require electrical power like rotor communication unit etc. The rotor power supply (11) comprises terminals of rotor power supply as well as elements that are able to store electrical energy, like capacitors (12), inductors or batteries. Batteries used inside rotor power supply (11) might be rechargeable batteries (20) able to deliver or absorb electrical power. Elements that store energy in rotor power supply (11) need to have enough capacity, so voltages or currents at terminals of rotor power supply (11) are stable enough during operation of the electric rotary machine, so control of currents in rotor windings (6) can work properly. The rotor power supply (11) might further comprise more sophisticated devices or parts like voltage or current regulators, protection devices, etc. In a typical case, the rotor power supply (11) comprises a capacitor (12) and there are two terminals of rotor power supply (11): high and low and the rotor power supply (11) provides a DC voltage between high and low terminal.

The rotor (2) might additionally comprise a rotor communication unit (15) whose function is to receive or transmit information and deliver the information to switch driver. For example, if rotor controller (8) controls rotation speed and torque by applying currents into rotor windings (6), it might be necessary that the rotor controller (8) receives information about desired speed of rotation or desired torque that is set by the user of the electric rotary machine. The rotor communication unit (15) is going to use electromagnetic fields, light or sound as a physical medium to carry the information being exchanged. To facilitate this task, the rotor communication unit (15) might contain known and available on the market components like antennas, LED diodes, ultrasonic transducers, as well as devices to facilitate communication according to certain communication protocol. It is also possible that the functionality of rotor communication unit (15), or part of the functionality is implemented together with rotor switch driver (10).

The stator (1) might also comprise a stator communication unit (18) whose function is to transmit information to the rotor communication unit (15) or receive information from the rotor communication unit (15). In most application cases the overall supervision of the disclosed here electric rotary machine is performed at a stator control (19) that is stationary, not rotating together with the rotor (2). That requires information to be transferred into rotor controller (8) and for that purpose stator communication unit (18) might be used. The information exchange between the rotor communication unit (15) and the stator communication unit (18) can use electromagnetic fields, light or sound as a physical medium to carry the information. Depending on application, the information exchanged between the rotor communication unit (15) and the stator communication unit (18) might include: angular position of the rotor, angular velocity of the rotor, desired angular position of the rotor, desired angular velocity of the rotor, currents of rotor windings, currents of stator windings, voltages at rotor winding terminals, voltages at stator winding terminals, magnitude, or direction of magnetic field, torque, desired torque, temperature of the rotor (2), temperature of the stator (1), resistance of rotor windings (6), resistance of stator windings (3), state of rotor switches (9), fault or alarm signals and others. To facilitate this task, the stator communication unit (18) might contain known and available on the market components like antennas, LED diodes, ultrasonic transducers, as well as other devices to facilitate communication according to certain communication protocol.

Depending on application, the stator (1) might also comprise a stator control (19) whose function is to perform necessary calculation or regulation or signal-processing functions and provide signals that are further transmitted from the stator communication unit into the rotor communication unit. Stator control (19) might also receive signals or information from sources like other devices, machines, or humans. The stator control (19) might process those signals or information and the stator control (19) might share the calculation, signal-processing and regulation tasks with switch driver (10) on the rotor (2) side. The stator control (19) might also provide signals into other devices, machines, or humans. For example, it might provide signals indicating state of operation, rotating speed, torque etc. The stator control (19) might also be coupled to switch unit (5) and the stator control (19) might control the electrical connection between terminals of stator winding (14) and phases of AC electric power supply. It is also possible that the functionality of stator control (19), or part of the functionality is implemented together on the same physical component with other parts of the stator (1).

The stator (1) might also comprise one or plurality of stator communication ports (22) whose function is to exchange information with other devices or machines or humans. For example, it might be LED diodes, screens, or loudspeakers for providing information to humans, or manually operated switches, touch-screens or bottoms to receive information from humans. It might also be physical connections or communication devices for exchanging information with other devices or machines.

In order to provide electrical supply for stator communication unit (18) or stator control unit (19), the stator 1 might comprise a stator supply unit (17), for example in form of at least one extra stator winding (16), where the extra stator winding (16), or plurality of extra stator windings (16) are placed inside stator (1) core to deliver AC electric power into the stator supply unit (17) and the stator supply unit (17) converts the AC electric power from extra stator windings (16) into DC electric power source that can be electrically coupled to other parts of stator (1) like stator control (19), or stator communication unit (18), or other parts in order to deliver necessary electric power for those parts to function. The stator supply unit (17) might also contain a battery, or a rechargeable battery (20), so stator control unit might be able to deliver DC power to stator control (19) or stator communication unit (18), even if terminals of stator windings (14) are disconnected from AC electric power supply, or if the AC electric power supply is not able to deliver electric power. In specific embodiments, the invention is as follows.

Fig. 1 presents a particular embodiment of an electric rotary machine comprising a stator (1) and a rotor (2), The stator further comprises: three stator windings (3) made of conductive material, where terminals of stator windings (14) in this particular example are connected in delta arrangement and for operation of the electric rotary machine are coupled to AC electric power supply (4) through a switch unit (5). The rotor (2) further comprises: three rotor windings (6) made of conductive material, where terminals of rotor windings (7) are in this particular example connected in a star arrangement. The rotor (2) further comprises a rotor controller (8), wherein the rotor controller further comprises rotor switches (9) - in this particular example constructed from power MOS transistors (13), switch-driver (10) and rotor power supply (11) in this case comprising a capacitor (12). The rotor further comprises a rotor communication unit (15), that can receive or send information and the rotor communication unit (15) is coupled to switch-driver (10). The stator (1) further comprises: an extra stator winding (16) and a stator supply unit (17), wherein the extra stator winding (16) is electrically coupled to stator supply unit (17) and the stator supply unit provides electrical DC power supply.

The stator further comprises stator communication unit (18) and the stator communication unit can send information to rotor communication unit (15) or receive information from the rotor communication unit. The stator further comprises a stator control (19) coupled to stator communication unit (18). Stator supply unit (17) further comprises a a rechargeable battery (20). In this particular example, the stator control (19) is coupled and can control switch unit (5) and the stator control (19) is coupled and can control stator communication unit (18) and the stator control (19) is coupled to a stator communication port (22).

Fig. 2 presents a diagram of current and voltage phasors and power flow in stator coordinates XY and rotor coordinates X'Y' for basic explanation of methods of operation of disclosed electric rotary machines.

We can assign a coordinate system to the rotor and stator in such a way that stator coordinate system XYZ doesn't move versus stator windings and the rotor coordinate system X'Y'Z' doesn't move versus rotor windings. If, for convenience, Z axis of either coordinate system is aligned with the axis of rotation of the electric rotary machine, we can refer to (XY) as stator coordinate system and to (X'Y') as rotor coordinate system. Any vector I phasor in stator coordinate system can be linearly transformed into representation in rotor coordinate system and vice versa. Phasors that we are going to consider in this disclosure have direction perpendicular to the axis of rotation. They can rotate within the plain (XY), or (X'Y') perpendicular to the axis of rotation. The rotation of a phasor might be at different angular speed. Since rotor might rotate at speed of WR versus stator, if a phasor rotates at an angular velocity W1 in stator coordinates, in rotor coordinates it will rotate at an angular velocity of W1 -WR.

Every winding inside stator or rotor has a corresponding current phasor pointing perpendicularly to the surface of the winding, whose magnitude is the current of the winding times number of loops in the winding. If a rotor, or stator contain plurality of windings, the rotor current phasor or stator current phasor is a vector sum of all current phasors from every individual winding. We consider stator current phasor (IS) and rotor current phasor (IR). Analogously to current phasor, we also define voltage phasor, whose direction is like for current phasor and magnitude is the difference between two voltages applied to the terminals of the winding. If terminals of a winding are shorted, voltage phasor of that winding is equal zero. If a rotor, or stator contain plurality of windings, the rotor voltage phasor or stator voltage phasor is a vector sum of all voltage phasors from every individual winding. In the machine geometry considered here, stator voltage phasor (VS) and rotor voltage phasor (VR) point radially within the plane perpendicular to rotation axis of the machine.

Disclosed here electric rotary machines and methods of operations cover also multi-pole machines, where at any given moment of operation, magnetization of the rotor or magnetization of the stator is not like in a magnetic dipole, but has multiple: 4, 6, 8,... poles, or correspondingly 2, 3, 4... pole pairs. In a case of such a machine, voltage and phasor diagrams are the same, only coordinate systems are not geometrical, but electrical - taking not the entire machine, but a portion of it, where the considered portion of rotor and stator is a dipole magnet, and a rotor rotation of alpha geometrical angle corresponds to alpha * m angle of electrical degrees, where m is the number of magnetic pole-pairs.

If terminals stator windings (14) are connected to a three-phase AC electric power supply (4), stator voltage phasor (VS) will rotate synchronously with the frequency of the AC three-phase main power supply: (WS) and the magnitude |VS| is defined by voltage amplitude of AC electric power supply. In a case of a single-phase AC electric power supply, the stator voltage phasor would be a sum of two voltage phasor components: (V1) and (V2), where (V1) and (V2) have equal magnitudes and both rotate at angular speed of (WS) in counterclockwise and clockwise directions respectively. Let's now introduce a simple linear model of an electric rotary machine described above. The model is based on an assumption, that a current phasor I induces magnetic field, whose average flux density B inside corresponding windings has the same direction, like I and that magnitude of B is linearly proportional to I: B=c*l. The assumption is not 100% accurate, because it doesn't include effect of magnetic hysteresis, or saturation, or other effects present in most magnetic materials. However, if soft magnetic materials are used for stator and rotor core and magnetic field is not saturated, the model provides enough accuracy. Under this assumption, the relationship between rotor I stator voltage and current phasors is:

VS=a*IS'+b*IR'+rs*IS,

VR=b*IS"+c*IR"+rr*IR, and

T=b*IS*IR*sin(IS,IR), wherein IS' is time derivative of IS in stator coordinates, I R' is time derivative of I R in stator coordinates, IS" is time derivative of IS in rotor coordinates, IR" is time derivative of IR in rotor coordinates and a, b, c, rs, rr are parameters of the linear model of the electric rotary machine.

According to the linear model, stator voltage phasor is a sum of 3 components: VS=a*IS'+b*IR'+rs*IS. In a steady-state situation, IR, IS and VS have constant magnitudes and only rotate in XY coordinates at velocity W1. In rotor coordinates X'Y', rotor current phasor IR and stator current phasor IS rotate at velocity W1-WR. According to linear model, rotor voltage phasor VR=c*IR"+b*IS"+rr*IR. Note, that time derivatives of IR in rotor coordinates IR" and time derivative of IS in rotor coordinates IS" are not necessarily equal IR' or IS', because rotor coordinates rotate versus stator coordinates at angular speed of WR.

Current phasors, or voltage phasors, or their components can rotate synchronously, or asynchronously versus each other. Two phasors, for example IS and VS rotate synchronously if in steady state, their angular velocities are equal, so the angle between them is constant over time. Two phasors rotate asynchronously if in steady state their angular velocities are not equal, so the angle between them changes over time.

The amount of power delivered into windings is I * V, where I is the current phasor and V is the voltage phasor and I * V is scalar product. The scalar product is a number equal to product of magnitude of phasor I times magnitude of phasor V times cosine of the angle between I and V. If the sign of I * V is negative, electric power is extracted from windings. The power transfer from AC electric power supply into stator windings is PS=VS*IS. The power supply from rotor controller into rotor windings is PR=VR*IR. The sum of PS and PR is converted into resistive power losses PH and mechanical power PM equal to torque T times angular velocity WR: PM=b*IR*IS*WR*sinlR,IS.

The resistive power losses PH is a sum of resistive losses in stator: rs*IS*IS, and resistive power losses in rotor: rr*IR*IR. If the angle between IS and VS is less than 90deg, power PS is transferred from AC electric power supply into stator windings, and if the angle is more than 90deg, PS is transferred from stator windings into AC electric power supply.

The absolute value of the cosine of an angle between IS and VS is the power factor PF. In a typical situation, the desired power factor PF is 1 , so no reactive power is injected into the AC electric power supply. The requirement PF=1 means that the angle between IS and VS is zero, or 180 degree, depending if the electric rotary machine works in motor, or generator mode. It is possible, by controlling the rotor current IR to control PF to have desired value. Presented in this disclosure methods of operation of different versions of electric rotary machines, specify sets of conditions to be fulfilled by current and voltage phasors for a method to work properly. That raises a question how to enforce respective current and voltage phasors to satisfy those conditions using the structure of a particular version of the disclosed electric rotary machine? There might be different regulation approaches and the enforcement method described below is just a particular method and the disclosure is not limited to this particular method. The enforcement method is a two-step approach. In the first step, the desired rotor current phasor is calculated. In the second step, the state of electronic switches in rotor is determined.

To determine the desired rotor current phasor IR_D, in case of a steady-state operation, conditions in respective claims are converted into a set of algebraic equations to be fulfilled by current phasor IR_D, or components of current phasor IR_D: IR1_D, IR2_D. Also, other conditions not mentioned in respective claims might be added to the set of equations: for example, the conditions that component of rotor current phasor: IR1 has to be perpendicular to a component of a stator current phasor: IS1 , or that power factor PF has desired value. Another equation that needs to be added is an equation of the desired torque T. The value of the desired torque might be provided by the operator of the electric rotary machine (human, or a machine), or it might be determined from other regulation methods applied for the electric rotary machine. Next, those equations are solved for example by micro-computer installed within the stator control (19), or swith driver (10) - either directly, or by an iterative computer-based method of solving algebraic equations, or other method. Performing those calculations might also require measurement of some variables within the electric rotary machine, like actual position, actual stator current phasor IS, actual stator voltage phasor VS etc. In case the machine is not in a steady-state, but in an intermediate state of operation, filtering methods might be used to gradually change from the desired rotor current phasor IR_D from initial to final steady-state of operation.

The second step is to determine state of electronic switches within rotor to enforce that actual rotor current phasor IR is equal, or at least close to the desired current phasor IR_D. There are number of known techniques involving Field-Oriented Control, PWM regulation, hysteresis regulation, etc, that can be used for this task.

A particular method proposed here is following. For given topology of electric circuit containing rotor windings and rotor switches, there exist a list of valid configurations of rotor switches. A configuration of rotor switches is an assignment, where each of rotor switches has an assigned state of conduction: “on”, or “off”. A configuration of rotor switches is valid, if in such a configuration every terminal of rotor winding is connected to exactly one terminal of rotor supply by one switch in “on” state and all other electronic switches connected to that terminal are in “off” state. Now, for every valid configuration of rotor switches, there exist a corresponding rotor voltage phasor given by values of voltages applied to every terminal of rotor windings.

The proposed here method of determining state of electronic switches might work in a following way: it periodically verifies which one of valid configurations of rotor switches leads to rotor voltage phasor VR, such that the angle between VR and (IR_D-IR) is smallest and then applies this particular configuration of rotor switches by forcing respective output signals of the switch driver. Fig. 3a and 3b illustrate current and voltage phasors as well as power transfers to explain a method of operating an electric rotary machine according to the above said during a steady-state operation. The voltage or current phasors are presented in stator coordinates XY or in rotor coordinates X'Y'.

For disclosed here electric rotary machines in a steady-state situation, it is possible that a current phasor or a voltage phasor comprise phasor components, and that those components rotate at different angular speeds. For example, rotor current phasor IR might comprise two components: IR1 and IR2, such that IR is a vector sum of IR1 and IR2: IR = IR1 + IR2 and IR1 rotates in stator coordinates at angular speed of W1 and IR2 rotates in stator coordinates at angular speed of W2. The term “comprises” used for current or voltage phasors means that list is not exclusive: for example: “IR comprises IR1 and IR2”, means that it is still possible that there is a further phasor IR3, such that IR = IR1 + IR2 + IR3 and in a steady-state IR1 rotates at W1 , IR2 rotates at W2 and IR3 rotates at W3.

On Fig. 3a and 3b, the rotor current phasor IR is a sum two phasor components: IR1 and IR2, where component IR1 rotates synchronously with stator voltage phasor VS at angular speed of WS, and component IR2 rotates asynchronously versus VS at angular speed of W2. Similarly, stator current phasor IS is a sum of two components: IS1 and IS2. The component IS1 is synchronous with IR1. The component IS2 is synchronous with IR2. In a linear model, stator voltage phasor VS is a sum of two components: voltage phasor induced by IR1 and IS1 : VS1=a*IS1'+b*IRT+rs*IS1 , and voltage phasor induced by IR2 and IS2: VS2=a*IS2'+b*IR2'+rs*IS2.

VS1 rotates at WS and VS2 rotates at W2. The ratio of magnitudes of IR2 and IS2 and the angle between IR2 and IS2 is such, that resulting stator voltage phasor component VS2 is equal zero, so VS = VS1 The VS2 is equal zero, because a*IS2’+b*IR2’ cancel rs*IS2. In rotor coordinates X'Y', IR1 and

151 induce a component of rotor voltage phasor VR1 and IR2 together with

152 induce VR2.

Electric power at rotor windings PR is equal:

PR = (IR1 + IR2) * (VR1+VR2) , so:

PR = (IR1 * VR1) + (IR2 * VR2) + (IR1*VR2) + (IR2*VR1).

Now, if IR1 and VR2 as well as IR2 and VR1 are asynchronous, the average value of IR1*VR2 is zero and average value of IR2*VR2 is also zero and the average electric power PR equals PR=IR1*VR1 and IR2*VR2. For that reason, if current phasor comprises two asynchronous components: IR1 and IR2, one can talk about average power transfer associated with current phasor component IR1 equal to IR1 * VR1 and average power transfer associated with current phasor IR2 equal IR2 * VR2.

The key aspect of this disclosure is that the magnitudes of IR1 and IR2 are chosen in such a way, that the average power transfer at rotor windings (6) associated with IR1 : PR1 and average power transfer associated with IR2: IR2 are of opposite sign and balance each other. By the notion "balance" we mean that PR1 +PR2 is exaclty zero, or is very small, so absolute value of PR1+PR2 is much smaller than the absolute value of PR1 or PR2: say below 5%, or that PR1+PR2 covers only power needs of other blocks of the rotor like: switch driver (10), or rotor communication unit (15).

Fig. 3a shows current and voltage phasors for a motor mode, where the angle between IR1 and VR1 is more than 90deg and the angle between IR2 and VR2 is less than 90deg, therefore PR1 is negative and PR2 is positive. It is possible to find such a ratio between magnitude of IR1 and IR2, that average power transfer from rotor controller and rotor windings is equal, or sufficiently close to zero, or that rotor windings in average deliver as much power to the rotor controller (8) as is needed by other parts of the electrical rotary machine that use the electric power from rotor power supply (11), like rotor switch driver (10), rotor communication unit (15) etc. In that situation the average power transfer between rotor windings and rotor controller associated with different components of rotor current phasor is balanced.

Fig. 3b shows current and voltage phasors for a generator mode, where the angle between IR1 and VR1 is less than 90deg and the angle between IR2 and VR2 is more than 90deg, therefore PR1 is positive and PR2 is negative. Again, it is possible to find such a ratio between magnitude of IR1 and IR2, that average power transfer from rotor controller and rotor windings is equal or sufficiently close to zero, or that rotor windings in average deliver as much power to the rotor controller as is needed by other parts of the electrical rotary machine that use the electric power from rotor power supply (11), like rotor switch driver (10), rotor communication unit (15) etc. In that situation the average power transfer between rotor windings and rotor controller associated with different components of rotor current phasor is balanced.

Fig. 4 presents a particular embodiment of an arrangement of electric rotary machines comprising two electric rotary machines (M1), (M2), wherein rotors (2) of electric rotary machines (M1), (M2), are mechanically coupled through a common shaft (21) and rotors (2) share the same rotor power supply (11) and rotor switch-driver (10). Terminals of stator windings (14) of electric rotary machines (M1), (M2) are electrically coupled in a parallel manner and coupled to AC electric power supply (4) through a common switch unit (5).

Fig. 5 illustrates current and voltage phasors to explain a method of operating an electric rotary machine presented on Fig. 4 in steady-state operation. In this particular case, the arrangement works in a generator mode, but phasors for motor mode can be derived analogously to Fig. 3a and 3b. Machine (M1) has two components of rotor current phasor: IR1_M1 and IR2_M1 , and machine (M2) also has two components of rotor current phasor: IR1_M2 and IR2_M2.

On stator side, machine (M1) has two components of stator current phasor: IS1_M1 and IS2_M1 , and machine (M2) has two components of stator current phasor IS1_M2 and IS2_M2. Furthermore, following pairs of current phasor components are synchronous: IS1_M1 and IR1_M1 , IR2_M1 and IS2_M1 , IS1_M2 and IR1_M2, IS2_M2 and IR2_M2. Following components of current phasors rotate synchronously with stator voltage phasor: IS1 _M 1 and IS1_M2. On the rotor side, the average power transfers associated with each of: IR1_M1 , IR2_M1 , IR1_M2 and IR2_M2 balance each other.

Moreover, stator voltage phasor of either machine (M1) or (M2) has only one component: VS=VS1_M1 =VS1_M2, rotating at WS, because the other component is equal zero: VS2_M1=VS2_M2=0.

Finally, phasors IS2_M1 and IS2_M2 have the same magnitude and opposite direction and they cancel each other. Since stator winding terminals (14) of (M1) and (M2) are electrically connected in parallel, the arrangement of electric rotary machines (M1) and (M2) doesn't inject any significant asynchronous current into the AC electric power supply (4).

Fig. 6 presents a schematic of a particular embodiment of an arrangement of electric rotary machines comprising a machine (M1) and a machine (N1), where rotors (2) of all electric rotary machines (M1) and (N1) are mechanically coupled through a common shaft (21) and rotors (2) share the same rotor power supply (11) and rotor switch-driver (10). Terminals of stator windings (14) of machine (M1) are electrically coupled to AC electric power supply (4) through a switch unit (5) and terminals of stator windings (14) of machine (N1) are electrically shorted. Fig. 7 illustrates current and voltage phasors and power transfers to explain a method of operating an electric rotary machine presented on Fig. 6 in steadystate operation. In this particular example the arrangement works in motor mode, but phasors for generator mode can be derived analogously to Fig. 3a and 3b. Machine (M1) has a stator current phasor IS_M1 and rotor current phasor IR_M1. Also, machine (N1) has a stator current phasor IS_N1 and rotor current phasor IR_N1. In machine (M1), IS_M1 and IR_M1 rotate synchronously with stator voltage phasor VS. In machine (N1), rotor and stator current phasors IR_N1 , IS_N1 are arranged in such a way, that resulting stator voltage phasor is zero, because stator winding terminals (14) are shorted. Moreover, power transfer between rotor windings (6) and rotor controller (8) associated to IR_M1 and power transfer between rotor windings (6) and rotor controller (8) associated to I R_N 1 balance each other.

Fig. 8 presents a particular embodiment of a single-phase electric rotary machine, wherein the stator (1) comprises one stator winding (3) and auxiliary winding (23), wherein the terminals of the stator winding (14) are coupled to a single-phase AC electric power supply (4) through a switch unit (5) and the auxiliary winding (23) is shorted and (23) is oriented perpendicularly to the stator winding (3), so current phasor of stator winding is perpendicular to current phasor of auxiliary winding. In this example, the rotor (2) comprise three rotor windings (6). Remaining aspects of the machine are analogous to Fig. 1.

Fig. 9 illustrates current and voltage phasors and power transfers to explain a method of operating an electric rotary machine presented on Fig. 8 in a steady-state operation. In this particular example the arrangement works in motor mode, but phasors for generator mode can be derived analogously to Fig. 3a and 3b. The single-phase AC electric power supply generates a stator voltage phasor VS, and the stator voltage phasor VS comprises two components: VS1 and VS2, wherein VS1 and VS2 have same magnitudes and rotate in opposite directions synchronously with AC electric power supply. Also the rotor current phasor IR comprises two components: IR1 and IR2, and IR1 is synchronous with VS1 and IR2 is synchronous with VS2. The average power transfer between rotor windings and rotor power supply due to rotor current phasor IR1 and average power transfer between rotor windings and rotor power supply due to current phasor IR2 balance each other.

Fig. 10a presents a particular implementation of an electric rotary machine comprising three single-phase machines M1 , M2, M3, wherein each of machines M1 , M2, M3 is coupled to three-phase AC electric power supply 4, characterized in that each machine M1 , M2, M3 is an electric rotary machine according to the machine shown in figure 8 and terminals of stator windings 14 of M1 , M2, M3 are arranged in delta connection. Rotors of M1 , M2 and M3 can be mechanically coupled.

Fig. 10b presents a particular implementation of an electric rotary machine comprising three single-phase machines (M1), (M2), (M3), wherein each of machines (M1), (M2), (M3) is coupled to three-phase AC electric power supply (4), characterized in that each machine (M1), (M2), (M3) is an electric rotary machine according to the machine shown in Fig. 8 and terminals of stator windings (14) of (M1), (M2), (M3) are arranged in star connection.

LIST OF REFERENCE NUMERALS

1 stator

2 rotor

3 stator windings

4 AC electric power supply

5 switch unit 6 rotor windings

7 terminals of rotor windings

8 rotor controller

9 rotor switches

10 switch driver

11 rotor power supply

12 capacitor

13 power MOS transistors

14 terminals of stator windings

15 rotor communication unit

16 extra stator winding

17 stator supply unit

18 stator communication unit

19 stator control (unit)

20 rechargeable battery

21 shaft

22 stator communication port

23 auxiliary winding

M1 , M2, M3, N1 electric rotary machines

XY stator coordinates

X'Y' rotor coordinates

WR rotor angular rotation speed

IR rotor current phasor

IR_D desired rotor current phasor

IS stator current phasor

IR1 , IR2 rotor current phasor component

IR_M1 , IR_M2 rotor current phasor of machine M1 or M2 respectively

IR1_M1 , IR2_M1 components of rotor current phasor in M1

IR1_M2, IR2_M2 components of rotor current phasor in M2

IR' time derivative of rotor current phasor in stator coordinates IR" time derivative of rotor current phasor in rotor coordinates

IS 1 , IS2 stator current phasor components

IS_M1 , IS_M2, IS_N 1 stator current phasor of machine M1 or M2 or N1 respectively

IS1 _M 1 , IS2_M1 components of stator current phasor in M1 IS1_M2, IS2_M2 components of stator current phasor in M2

IS' time derivative of stator current phasor in stator coordinates

IS" time derivative of stator current phasor in rotor coordinates

VR rotor voltage phasor

VS stator voltage phasor

VR1 , VR2 rotor voltage phasor components

VS1 , VS2 stator voltage phasor components a, b, c, rr, rs parameters of linear model of an electric rotary machine

W1 , W2 angular velocities of rotation of current or voltage phasors WS angular velocity of AC electric power supply sinU,V sinus of an angle between phasors U and V cosll,V cosine of an angle between phasors U and V

T torgue

P power

PF power factor

PM mechanical power

PS electrical power delivered to stator windings

PR electrical power delivered to rotor windings

PH resistive power losses in stator and rotor windings

PR1 , PR2 electrical power delivered to rotor windings associated with current phasor component IR1 or IR2 respectively

PS1 , PS2 electrical power delivered to rotor windings associated with current phasor component IS1 or IS2 respectively