THREE-PHASE TWO-PHASE ELECTRIC MACHINE AND METHOD FOR CONTROLLING SUCH A MACHINE

Description

Scope of the invention

[0001] This application relates to the field of polyphase electrical machines and their control, and more particularly to machines with several three-phase wound systems that must operate at relatively high ambient temperatures, typically 160°C.

[0002] Preferably, but not exclusively, the invention will find preferential use in demanding automotive applications, such as, for example, in an electric camshaft phaser or in a turbocharger discharge actuator, applications close to a significant heat emission source and requiring a high degree of compactness to integrate into the environment. State of the art

[0003] The following documents, presenting polyphase electrical architectures with two three-phase systems, are already known in the prior art: Document EP3098963, for example, presents a dual three-phase architecture that minimizes the machine's common mode when controlled by vector control. Vector control allows for good machine performance in terms of torque regularity but has the drawback of requiring complex control with advanced control electronics and a precise position sensor.

[0004] Document US2014375232 also presents a dual three-phase architecture with two separate power sources and a power transfer circuit between the two three-phase systems. Here again, the machine control is vector-based, with the added requirement of doubling the power sources.

[0005] Document WO2016012703 also presents a dual three-phase architecture with two separate control modules, intended for automotive applications. The two modules are interconnected to minimize their total losses. The control method is not specified and requires continuous phase angle control for both electronic modules. It is also well known to implement a 30° phase shift between two three-phase systems to achieve the equivalent of a balanced six-phase architecture.

[0006] Finally, document EP3224929 (US 2017 / 264178 A1) presents a dual three-phase architecture with the use of a star connection and a delta connection, the two three-phase networks being associated with two voltage sources of different value. Problem not solved by the state of the art

[0007] In automotive applications operating at medium power (typically a few tens of watts to a few kilowatts), state-of-the-art architectures cannot be applied efficiently and economically. Indeed, the use of complex vector control or two separate electronic modules makes the solution too bulky and expensive compared to the three-phase solutions with which it competes, the latter being the most widely used in these applications today.

[0008] Furthermore, existing dual three-phase systems mostly use electrical machines with several windings per phase with interlocking of the different phases of the two three-phase systems, making implementation uneconomical and industrially complex with typically 12 or more windings to manage.

[0009] There are no simple and economical solutions in the state of the art for obtaining a compact actuator for medium power automotive applications that offers the advantages of dual three-phase systems compared to a simple three-phase system: higher and more constant average torque, more favorable harmonic content of signals and torque. Objects of the invention

[0010] The main object of the invention is to offer simple and economically viable double three-phase electrical machines for the automotive industry in medium power applications.

[0011] In particular, one of the objects of the invention is to propose a generic topology for a double three-phase machine optimized for block control, through the use of decoupling teeth that magnetically separate the phases of each half-machine and the phases between the two half-machines. The proposed topology is thus suited to the simplicity of block control compared to state-of-the-art vector control systems.

[0012] Another objective of the invention is to limit or simplify significantly the number of motor windings and to allow for improved compactness compared to equivalent three-phase solutions.

[0013] It is also within the object of the invention to propose a simple control for such machines, in particular in the context of the use of block switching, which is much simpler to implement than vector control, supported by economical electronic equipment, while retaining the aforementioned advantages.

[0014] More particularly, the invention relates to an electrical machine having a first and a second three-phase winding and comprising a stator formed of a cylindrical yoke made of a soft ferromagnetic material extended radially by a set of teeth, a portion of said set of teeth carrying said windings, said windings being distinct from each other, said first three-phase winding being electrically connected in delta, said second three-phase winding being electrically connected in star, characterized in that the total number of said stator teeth is equal to 3. N 1 + N 2). (k + 1) with k a natural number greater than or equal to 1 representing the number of consecutive coils of the same phase of a winding, N1 and N2 being the number of groups of consecutive coils of the same phase respectively of said first and second winding, said two windings being separated by at least one tooth not carrying any winding.

[0015] For the purposes of this invention, "number of consecutive coils of the same phase" means the number of coils belonging to the same phase and to the same half-machine and which are adjacent and not separated by an unwound tooth.

[0016] Similarly, the term "number of consecutive coil groups of the same phase," as used in the present invention, refers to the number of groups consisting of consecutive coils belonging to the same phase of the same half-machine, separated by at least one decoupling tooth. These coil groups may be separated by a single decoupling tooth or by several teeth and other coil groups belonging to other phases.

[0017] Preferably, the windings are carried by the main teeth, with the teeth not carrying any windings being decoupling teeth, and the angular width of the decoupling tooth, considered from the center of the machine and delimited by the width of the free end of the teeth, being less than or equal to the angular width of the main teeth. In this way, the flux collected by the wound teeth is maximized.

[0018] A preferred machine will follow the relationship N1=N2=k=1, with twelve teeth in total, including six wound teeth and six unwound teeth alternating, making a machine economical to manufacture.

[0019] In one possible embodiment, said first three-phase winding is carried by a first group of consecutive stator teeth alternating wound and unwound teeth and said second three-phase winding is carried by a second group of consecutive stator teeth alternating wound and unwound teeth, said first and second groups of stator teeth being distinct from each other.

[0020] In another embodiment, said first three-phase winding and said second three-phase winding are alternated so that a periodic pattern is formed of a first tooth of said stator carrying a coil of said first winding, a second tooth of said stator not carrying any winding and a third tooth of said stator carrying a coil of said second winding, said first, second and third teeth being consecutive in the circumferential direction of said stator.

[0021] Preferably, said first winding is distributed angularly over a first sector of 180°, said second winding is distributed angularly over a second sector of 180°, said first and second sectors being distinct from each other, and each of said windings is electrically connected to a set of electrical tracks, said sets of electrical tracks being distinct from each other and distributed angularly over two distinct angular sectors of 180°.

[0022] The invention also relates to a method of controlling a machine having a double three-phase winding as described above characterized in that each three-phase winding is controlled by a block sequence and in that each three-phase winding is controlled with an electrical offset of 30° from each other, so as to achieve twelve electrically equal-distributed control vectors.

[0023] Preferably, said first and second windings are powered by two different power bridges, each comprising six electronic switch cells.

[0024] Advantageously and preferentially, said block control is carried out using pulse width modulation, known as PWM, a first PWM is applied to the first winding, a second PWM is applied to the second winding and said first and second PWM are applied in such a way as to cancel or minimize the overlap periods during which the positive alternations are applied at the same time.

[0025] In one embodiment, said PWM is applied to said electronic switches and in another embodiment, the machine further comprises and upstream of said power bridges with six cells of electronic switches, a rectifier bridge formed of four cells of electronic switches receiving as input a two-wire electrical signal from a central control unit, said block control is carried out using pulse width modulation, said PWM, said PWM control is applied to the input of said rectifier bridge, said rectifier bridge carrying out the active rectification of said PWM control and said two power bridges being controlled in whole steps.

[0026] The control of said two three-phase windings can be carried out by a single microprocessor or by two separate microprocessors.

[0027] The invention also relates to a setting device for the continuous phase shift of the rotation angle of a camshaft controlling the gas exchange valves of an internal combustion engine with respect to a drive element, in particular a chain or belt, comprising a brushless electric setting motor with a stator fixed relative to an outer ring, the motor being coupled to a three-input / output reducer comprising the outer ring (4), an input element and an output disc, the outer ring being driven by said drive element, said output disc being integral with the camshaft, characterized in that said motor is an electrical machine conforming to the above-mentioned variants.

[0028] The invention further relates to a system comprising an electromagnetic actuator for controlling a turbocharger relief valve and a relief valve, characterized in that said motor is an electrical machine conforming to the aforementioned variants. Brief description of the figures

[0029] Other features and advantages of the invention will become apparent from the following detailed examples of embodiments, with reference to the attached figures which respectively represent: [ Fig 1] Figure 1 , a schematic cross-sectional view of a machine according to the invention in a first embodiment, [ Fig 2] Figure 2 , a schematic cross-sectional view of a machine according to the invention in a second embodiment, [ Fig 3] Figure 3 , a schematic cross-sectional view of a machine according to the invention in a third embodiment, [ Fig 4] Figure 4, a schematic cross-sectional view of a machine according to the invention in a fourth embodiment, [ Fig 5] Figure 5 , a schematic cross-sectional view of a machine according to the invention in a fifth embodiment, [ Fig 6] Figure 6 , a perspective view of a machine according to the invention with a first example of electrical phase connections, [ Fig 7] Figure 7 , a perspective view of a machine according to the invention with a second example of electrical phase connections, [ Fig 8] Figure 8 , a schematic cross-sectional view of a machine according to the invention in another embodiment, [ Fig 9a ] ] Fig 9b] Figures 9a and 9b , two schematic cross-sectional views of a machine according to the invention in a particular embodiment, [ Fig 10] Figure 10 , a schematic view of the connection of a machine according to the invention to a control converter in a first implementation example, [ Fig 11] Figure 11, a schematic view of the connection of a machine according to the invention to a control converter in a second implementation example, [ Fig 12] Figure 12 , a block control timing diagram using pulse width modulation that can be used to control a machine according to the invention, [ Fig 13] Figure 13 , two detailed pulse width modulation timing diagrams for different duty cycles and two different methods that can be applied to a machine according to the invention, [ Fig 14] Figure 14 , a block control timing diagram using pulse width modulation that can be used to control a machine according to the invention, [ Fig 15] Figure 15 , a first example of a mechatronic assembly implementing a machine according to the invention, [ Fig 16] Figure 16 , a second example of a mechatronic assembly implementing a machine according to the invention, [ Fig 17] Figure 17, a third example of a mechatronic assembly implementing a machine according to the invention, [ Fig 18 ] There figure 18 represents a cross-sectional view of a device according to an example embodiment, [ Fig 19a ] ] Fig 19b] Figures 19a and 19b , schematic views of the connection of a machine according to the invention to a control converter representing the two switching states used to characterize one phase of the first three-phase winding, [ Fig 20a ] ] Fig 20b] Figure 20a , the measurement of the voltage across the terminals of two terminations of a three-phase inverter and Figure 20b , the measurement of current flowing through a current measuring element, during one of the coil characterization sequences. Fig 21a] Figures 21a and 21b , schematic views of the connection of a machine according to the invention to a control converter representing the high torque control and its adaptation to low torque with the deactivation of one of the two three-phase windings. Detailed description of the implementation methods

[0030] The figure 1This represents a first example of an electrical machine according to the invention, comprising a stator (3) composed of two half-machines, respectively (1) and (2), each carrying a three-phase winding, respectively (4a, 4b, 4c) and (5a, 5b, 5c), each of the subscripts a, b, and c representing a phase of the three-phase systems formed. The stator (3) is in the form of a cylindrical ring (6) from which teeth extend radially. Each half-machine (1, 2) has two types of teeth alternating with each other: the tooth (8) carrying a coil is called the main tooth, and the tooth (7) carrying no winding is called the decoupling tooth, and its role is to magnetically decouple the phases and the two half-machines. The half-machine (1) composed of all the main teeth (8) and secondary teeth (7), thus creates 3 elementary patterns, positioned successively according to the tangential direction.The half-machine (2), composed of all the main teeth (8) and secondary teeth (7), thus creates 3 elementary patterns, positioned successively along the tangential direction. In the example case of this... figure 1 The different phases of a first half-machine (1) are connected in delta and the different phases of the second half-machine (2) are connected in star. The decoupling teeth have an opening angle (a7), the apex of this angle being the center of rotation of the motor and the angle being defined by the width of the tooth at its open end, which is less than or equal to the opening angle of the main teeth (a8) in order to maximize the magnetic flux collected by the main tooth (8) and thus improve the performance of the machine, although this relationship is not strictly necessary within the scope of the present invention.

[0031] On this figure 1The rotor consists of internal magnets (9) attached to a rotor yoke (10) made of ferromagnetic material and a shaft (not visible) which may or may not be ferromagnetic. This rotor is shown only as an example, and any other type of rotor traditionally used in any brushless machine may be used.

[0032] There figure 2 presents a variant embodiment similar to that shown in figure 1 but differs from the latter in that the main teeth (8) have, at their open end, flares (29), or polar flares, in order to collect more magnetic flux generated by the rotor and in that the rotor has magnets (9) on the surface of the yoke (10), this rotor being a second example of rotor realization.

[0033] There figure 3presents a variant of the machine embodiment, without a visible rotor, where each half-machine (1, 2) is composed of three elementary motifs extending over a mechanical angle of 60° and made of an assembly comprising here 3 consecutive main teeth (8) and a decoupling tooth (7), each of the three main teeth carrying a set of coils belonging to the same phase of the same half-machine. On the figure 3 The indices A, B, and C refer to the three different phases of each half-machine (indices _1 and _2) separated from each other by a decoupling tooth (7) carrying no windings. The two half-machines (1) and (2) are nested here, because a phase of the first half-machine (indice _1) is followed angularly by a phase of the second half-machine (indice _2), the two being separated by a decoupling tooth (7).

[0034] In figure 4 , a variant implementation similar to that of the figure 3is shown, but for which the two half-machines (1) and (2) are spatially positioned each over 180°, the first half-machine (index _1) is composed of 3 successive elementary motifs in the tangent direction, just like the second half-machine (index _2). Each phase (A_2, B_2, C_2, A_1, B_1, C_1) is carried by three main teeth (8) and is separated by a decoupling tooth (7).

[0035] There figure 5 presents a 36-tooth machine having four coils per phase with two groups of two diametrically opposed teeth. The two half-machines (index _1 and _2) are nested, that is to say, alternating two teeth wound from the same phase and from the same machine with two teeth wound from the same phase and from the other machine, each group of two teeth being separated from its neighbor by a decoupling tooth (7).

[0036] There figure 6This represents, by way of non-limiting example, the connection of a machine with 6 main teeth (8) and 6 decoupling teeth (7). The stator (3) is made of two half-machines (1) and (2), each extending over an angle of approximately 180°. This solution ensures the connection of the windings through the distribution of currents between the two half-machines. Two sets (11) and (12) of conductive parts, typically made of copper, provide the star connection of the winding in the first half-machine (1) and the delta connection of the winding in the second half-machine (2). The sets of conductive parts (11) and (12) can advantageously be arranged on the same plane to improve the compactness of the assembly and reduce the risk of electrical contact between the different electrical parts without using specific insulation.

[0037] There figure 7This is an alternative method for connecting the windings of the two machine halves using a printed circuit board (13) directly connected to the various windings, without using the previously described conductive parts. The traces on the printed circuit board (13) perform the star and delta connection function for the windings. In this solution, each coil is connected directly to the printed circuit board (13) using a press-fit connection.

[0038] There figure 8represents an electric machine according to an alternative embodiment comprising a rotor external to the stator, having a yoke (10) carrying a ring of magnets (9), where the half-machines are nested, the coils (4A, 4B and 4C) belonging to a first half-machine and the coils (5A, 5B and 5C) belonging to a second half-machine and which has the particularity of presenting polar flares (29), that is to say a widening of the free end of the tooth opposite the rotor, on the main teeth (8), the decoupling teeth having a constant width in the radial direction, without flare at their free end.

[0039] THE figures 9a and 9b present another embodiment in which the two half-machines (1, 2) are each built on a half-stator (1a, 1b). figure 9a is a view before assembly, the figure 9bThis is a view after assembly. The separation of the two stator halves (3a, 3b) can be made at the center of the decoupling teeth (7), or it can also be made on the edge of the decoupling teeth (7) as shown here. This design allows the coils (4, 5) to be inserted onto the main teeth (8), which are longer than in other embodiments, by mounting the coils (4, 5) of the two machine halves before assembling the complete machine. Mounting the different coils (4, 5) would not have been possible on a single stator, as the central opening where the rotor (not shown) must be housed does not allow the passage of these coils.

[0040] In Figure 10A schematic view of the electrical connection of a machine according to the invention to a converter is shown. Each half-machine, connected in a star (1) and delta (2) configuration, is supplied with voltage by a three-phase bridge rectifier (14, 15), respectively, each composed of six electronic switches, according to a configuration commonly understood by those skilled in the art. The converter has at its input a filter (16), connected to the voltage source (E) made up of an array of inductors (17) and a capacitor bank (18). This filter (16) is connected to the terminals of the three-phase bridge rectifiers (14, 15) connected to the two half-machines (1, 2). The adapted and alternating control of the different switches minimizes the size of the filter (16), thus reducing cost and overall size.

[0041] There figure 11This represents a schematic view of the electrical connection of a machine according to the invention to a converter enabling the control of the six-phase machine via a two-wire pulse control (30), such as that provided by the electronic control unit (ECU) of a vehicle powered by a voltage source such as a battery (E), for example via pulse-width modulation, known by the abbreviation PWM. Because the two-wire signal (30) can have a negative or positive polarity, i.e., an electrical ground that can be on the upper or lower line, the converter includes a rectifier (19), here active, controlled by four electronic switches, allowing the conversion from a positive or negative pulse signal to positive pulses that supply the three-phase bridges (14, 15).

[0042] There figure 12This demonstrates the principle of the control applied to the phases of the two half-machines. Controls C1 and C2 are applied to the branches of the three-phase bridges of the Figure 10 For example, control C2 exhibits an electrical offset of 30° relative to control C1, this angular offset arising from the electrical offset between the induced phase voltages of the second half of the machine and those of the first. Each control C1 and C2 consists of a control (HS1, HS2) of the voltage-side transistors, called High Side, receiving a chopped PWM-type voltage (PWM1, PWM2) and a control signal (LS1, LS2) from the ground-side transistors, called Low Side, receiving a constant voltage (ON). Each control shown here is traditionally used as a unit for three-phase machines and is also found under the English name of Slow decay.

[0043] There figure 13This describes two methods for controlling the half-machines, respectively labeled P1 and P2, using pulse-width modulation (PWM1 and PWM2) applied to the three-phase bridges of each half-machine. The aim of both methods, P1 and P2, is to minimize the overlap times during which the two half-machines are powered simultaneously, thereby reducing current ripple and thus minimizing the size of the filter described earlier for the converter driving the machine. By alternating the power supply between the two half-machines as much as possible, this goal can be achieved depending on the duty cycle indicated as a percentage in the figure. The method will be more efficient the lower the duty cycle. As shown in the figure 13 , whether for process P1 or P2, no overlap between PWM1 and PWM2 is observed when the duty cycle is less than 50%.

[0044] For example case P1, the method consists of achieving a symmetrical control with respect to the midpoint of the period. For example case P2, the method consists of triggering the PWM2 control after the completion of the positive PWM1 control when the duty cycle is less than 50%, and then minimizing signal overlap above this value.

[0045] There figure 14 represents the typical signals applied to a converter as shown in figure 12DIR1 and DIR2 represent the two-wire signal (30). In CAS1 on the left of the figure, a PWM control is generated on line DIR1, so that a positive average voltage value is obtained on this line, while line DIR2 is at zero, corresponding to ground. On the right for CAS2, DIR2 has a positive average value and DIR1 is at zero. After rectification by element (19), the signal entering the power bridges (14, 15) is as shown in line V, but the control (HS1, LS1, HS2, LS2) of the power bridge switches (14, 15) will be carried out according to the polarity of DIR1 and DIR2, and will be different in CAS1 and CAS2.

[0046] There figure 15This represents a mechatronic assembly that generates motion using energy from a vehicle battery (31) delivering a constant voltage. The battery is connected to two three-phase bridges (14, 15), and after filtering (16), these bridges generate alternating voltages at the terminals of a six-phase machine (20) directly connected to a mechanical load (21). The three-phase bridges (14, 15) are controlled by a microcontroller (22) connected to a centralized control unit (ECU). The controller (22) exchanges information via a bidirectional link (24) with the central control unit (ECU) and receives information from position sensors (25, 26) that determine the motor position and from an absolute position sensor (27) at the load output. The connection to the battery (19) is made via a connector (28) that allows the transfer of commands from the ECU and the power lines from the battery (31).

[0047] There figure 16represents a variant implementation of a mechatronic assembly similar to the figure 15 but using two controllers (23a, 23b) instead of one, each of these controllers (23a, 23b) controlling the three-phase bridges respectively (14, 15) from the position information coming from the rotor position sensors (25, 26) of the machine (20).

[0048] There figure 17 represents a particular embodiment of a mechatronic assembly using a machine according to the invention, implementing the converter shown in figure 11 . In this assembly, a battery (31) powers an electronic control unit (ECU) which provides, through a connector (28), a two-wire signal (30), preferably in the form of a PWM signal, which passes through a rectifier (19) before powering the three-phase bridges (14, 15) and the microcontroller (23) in order to drive and control the six-phase machine. Application : electrical phase shifter

[0049] An electric machine according to the invention is particularly suitable for driving a camshaft phaser.

[0050] There figure 18 represents a cross-sectional view of a device according to an example embodiment, coupled to a camshaft (41). The device consists of an electrical machine (42) as described above, associated with a reducer (43), here of the trochoidal type.

[0051] The reduction gear (43) comprises an outer ring (44) driven by the timing chain or belt of the internal combustion engine (not shown). This outer ring (44) has a typical outer diameter of 100 to 150 millimeters and external teeth adapted for drive by said timing chain. Its inner surface has a tubular toothed race (45). This outer ring (44) is free to rotate relative to the camshaft (41).

[0052] An eccentric gear wheel has a section smaller than the inner section of the outer ring (44), the number of teeth of the gear wheel being less than the number of teeth of the toothed path (45) on the inner surface of the outer ring (44), with identical module.

[0053] The difference between the number of teeth of the eccentric gear and the number of teeth of the toothed path on the inner surface of the outer ring is advantageously one tooth in order to maximize the reduction ratio of the trochoidal reducer (43).

[0054] The eccentric gear is guided by a bearing mounted on the single shaft (48) at the level of an eccentric whose axis of revolution is eccentric with respect to the median axis of the single shaft (48). The offset between these two axes is generally between 0.1 and 1 mm and depends on the module of the teeth of the trochoidal mesh.

[0055] This output disc (49) is also attached to the camshaft (41) by a screw (50) with which it is coupled via a radial flare (15), close to the axis of rotation of the assembly formed.

[0056] The invention is not limited to trochoidal reducers. Other reducers can be used, for example, epicyclic reducers. The choice of one reducer over another may depend on the desired reduction ratio and the final cost of the solution.

[0057] Various details of the realization of such a camshaft phaser are described in European patent EP3464841, which does not constitute a limitation of protection but a simple example of a mechanism capable of being driven by an electric machine according to the invention. Application : turbocharger discharge actuator

[0058] An electric machine according to the invention is particularly suited to controlling a wastegate for a turbocharger in internal combustion engines. This wastegate regulates the gas pressure in the turbocharger turbine.

[0059] Internal combustion engines (for motor vehicles, trucks, construction equipment, etc.) operate through the explosion of an air / fuel mixture in the combustion chamber of the cylinders.

[0060] The engine's air intake system, which manages and exhausts the air supplying the engine, operates using various valves. To improve the performance of the internal combustion engine, some vehicles are equipped with a turbocharger, which forces more air into the combustion chamber.

[0061] An electrical machine conforming to the invention represents a particularly well-suited solution for demanding applications such as turbochargers. Application : electronic method for phase balancing

[0062] An electrical machine according to the invention exhibits an intrinsic sensitivity to imbalances in the impedance or inductance of its phases. These imbalances are common but often negligible in conventional machines and can arise from manufacturing variations in the number of turns constituting the coils, from the variable quality of electrical connections made by press-fit or welding, from an imbalance in the lengths of the electrical connections, etc. In the specific case of an electrical machine according to the invention, the difference in the topology of the two half-machines, one connected in star and the other in delta, necessarily implies using a different number of turns between the coils of these two half-machines to obtain an equivalent current at the same inverter voltage. This difference corresponds to an ideal ratio, and the effective number of turns of each of the two half-machines is obtained by rounding to the nearest integer.This implies that an error equivalent to the impedance of half a turn or more can occur, and this error is all the greater when the number of turns in the windings is small. This results in a current imbalance between the phases of the two half-machines that can reach up to 10%. This imbalance causes torque ripple, complicating control, premature wear of the guidance system, and premature wear of the electronic components due to one half-machine being subjected to greater stress than the other.

[0063] An economical method of characterization and compensation is proposed in the figures 19a, 19b, 20a and 20b This method requires the addition of at least one current measurement element (100) on one of the DC lines between the inverters and the filter, visible on the figures 19a and 19bThe use of at least one current measurement element (100), positioned between the inverters and the filter and coupled with an algorithm to discriminate between the compositions of each inverter / motor assembly, allows for optimization of the electrical architecture. Note that it is possible to use multiple current measurement elements (100), for example, one per inverter, to improve the accuracy of this measurement.

[0064] Thus, a characterization, at the output of the production line, of the impedances and inductances of each phase of the motor can be performed using the application of a simple control sequence and the analysis of said current. This sequence consists of applying the battery voltage across the terminals of one phase for a sufficiently long time to analyze the transient current regimes due to inductive effects, as shown in figure 19afor one phase of the star-wound half-machine (1), then apply the opposite voltage to that same phase, as shown figure 19b , for a sufficiently long time to observe the new current variation. The voltage, measured across the terminals (101, 102) of the supplied phase, typically has the shape shown in the figure 20a and the current, measured using the current measuring element (100), is given in the figure 20b Measurements of the time constant and amplitude of this current allow us to deduce the inductance and impedance values ​​of the phase. By repeating this measurement for all phases of the two half-machines, we can calculate a ratio for each phase, relative to the phase with the worst characteristics. This ratio is then used to individually weight the duty cycle of the pulse-width modulation controlling the voltage waveform feeding the half-machines. Application : electronic method for optimizing torque control

[0065] An electrical machine according to the invention exhibits constant-resolution torque regulation across its entire operating range. This is achieved by modifying the duty cycle using pulse-width modulation, which allows for phase voltage control. This principle also applies to conventional electrical machines, such as three-phase machines. However, in applications involving the synchronization of two rotating systems, which may consist of two electrical sub-assemblies, it is often necessary to have very high resolution to regulate small load variations and thus a precise torque response from the electrical machine. Such high resolution is not required when load variations are significant and a larger torque response from the electrical machine is needed.

[0066] The specificity of the invention allows us to improve the resolution of the torque regulation over the operating range where the torque is lowest, up to half the nominal torque of the assembly, as described in the figure 21a In this figure, T n is the torque in normal operating conditions, y is the torque constant, n is the number of turns in each coil. V DC is the inverter's supply voltage, D is the duty cycle of the transistors composing the inverter, and Rφ eq And Lφ eq are the equivalent resistance and inductance of a coil for the two half-machines, connected in star and delta configurations, with different duty cycles. It is possible to determine the smallest possible variation in torque under normal operating conditions, as a function of the minimum variation in the duty cycle of the voltage control Δ D , according to Δ T n = γ . n .2 . V DC . Δ D Rφ eq + Lφ eq .

[0067] An algorithmic method is therefore proposed to deactivate one of the two half-machines when the required torque regulation is below half the nominal torque, as represented in the figure 21b , Or T m is the torque accessible in this optimized mode. This allows all pulse-width modulation steps to be dedicated to the active half-machine alone, instead of being shared between the two half-machines. This effectively doubles the modulation frequency for the active half-machine and halves the minimum duty cycle variation, Δ D, leading to halving the torque resolution of the set, Δ T m = γ . n .2 . V DC . Δ D Rφ eq + Lφ eq .

[0068] Doubling the modulation frequency of the active machine by deactivating the second is not the only possible option; intentionally degrading the frequency over certain torque ranges is also being considered to ensure a smoother transition between the low-torque range, where only one machine is active, and the high-torque range, where both machines are active. Another possibility is to transfer only a portion of the control steps from the inactive machine, thus achieving a progressively variable resolution.

Claims

1. An electric machine having a first (4a, 4b, 4c) and a second (5a, 5b, 5c) three-phase windings and comprising a stator (3) formed of a cylindrical yoke (10) made of a soft ferromagnetic material radially extending to a set of teeth (7, 8), a part of said set of teeth (8) carrying said windings, said windings (4a, 4b, 4c, 5a, 5b, 5c) being distinct from one another, said first three-phase winding (4a, 4b, 4c) being electrically triangle-connected, said second three-phase winding (5a, 5b, 5c) being electrically star-connected characterised in that the total number of said teeth (7, 8) of stator (3) is equal to 3 · (N1 + N2) ·(k + 1) with k being a natural number higher than or equal to 1 representing the number of consecutive coils of a same phase of a winding, N1 and N2 being the number of groups of consecutive coils of a same phase respectively of said first and second windings, said two windings being separated by at least one tooth (7) carrying no winding, and also each group of consecutive coils of a same phase being separated by at least one tooth (7) carrying no winding.

2. The electric machine according to claim 1, characterised in that said windings are carried by main teeth (8), in that said teeth carrying no winding are decoupling teeth (7) and in that the angular width of said decoupling tooth (7), considered from the centre of the machine and delimited by the width of the free end of said teeth, is less than or equal to the angular width of said main teeth (8).

3. The electric machine according to claim 1 characterised in that N1=N2=k=1, said stator (3) having twelve teeth (7, 8) in total of which six teeth are wound and six teeth are unwound alternately.

4. The electric machine according to any one of claims 1, 2 or 3, characterised in that said first three-phase winding is carried by a first group of consecutive stator teeth with alternating wound tooth and unwound tooth and in that said second three-phase winding is carried by a second group of stator teeth with alternating wound tooth and unwound tooth, said first and second groups of stator teeth being separate from each other.

5. The electric machine according to any one of claims 1, 2 or 3, characterised in that said first three-phase winding and said second three-phase winding are alternated so that a periodic pattern is formed of a first tooth of said stator carrying a coil of said first winding, a second tooth of said stator carrying no winding and a third tooth of said stator carrying a coil of said second winding, said first, second and third teeth being consecutive along the circumferential direction of said stator.

6. The electric machine according to claim 4, characterised in that said first winding is angularly distributed over a first 180° sector, in that said second winding is angularly distributed over a second 180° sector, said first and second sectors being separate from one another, and in that each of said windings is electrically connected to a set of electric tracks, said sets of electric tracks being separate from each other and angularly distributed over two angular 180° sectors separate from each other.

7. A method for controlling a machine having a double three-phase winding according to any one of the preceding claims, characterised in that each three-phase winding is controlled by a block sequence and in that each three-phase winding is controlled with an electrical offset of 30° from one another.

8. The method for controlling a machine having a double three-phase winding according to claim 7 characterised in that said first and second windings are supplied by two different power bridges (14, 15) each including six electronic switch cells.

9. The method for controlling a machine having a double three-phase winding according to claim 8, characterised in that said block control is carried out using pulse width modulation, known as PWM, in that a first PWM is applied to the first winding, in that a second PWM is applied to the second winding and in that said first and second PWMs are applied so as to cancel or minimise the overlap periods during which the positive alternations are applied at the same time.

10. The method for controlling a machine having a double three-phase winding according to claim 9, characterised in that said PWMs are applied to said electronic switches.

11. The method for controlling a machine having a double three-phase winding according to claim 8, characterised in that the machine further comprises, upstream of said power bridges with six electronic switch cells, a rectifier bridge formed of four electronic switch cells receiving as an input a two-wire electrical signal from a central control unit, said block control being carried out using pulse width modulation, known as PWM, said PWM control being applied as an input of said rectifier bridge, said rectifier bridge carrying out active rectification of said PWM control and said two power bridges being controlled in full steps.

12. The method for controlling a machine having a double three-phase winding according to any one of claims 7 to 11, characterised in that controlling said two three-phase windings is carried out by one and a single microprocessor.

13. The method for controlling a machine having a double three-phase winding according to any one of claims 7 to 11, characterised in that controlling said two three-phase windings is carried out by two separate microprocessors.

14. An adjusting device for continuous phase shift of the angle of rotation of a camshaft controlling the gas exchange valves of an internal combustion engine relative to a drive element, especially a chain or belt, comprising a brushless electric adjustment motor with a fixed stator relative to an outer ring gear, the motor being coupled to a three-input / output reduction gear (43) comprising the outer ring gear (44), an input element (46) and an output disc, the outer ring gear (44) being driven by said drive element, said output disc being integral with the camshaft (41) characterised in that said motor is an electric machine according to any one of claims 1 to 6.

15. A system comprising an electromagnetic actuator for governing a relief valve for a turbocharger and a relief valve, characterised in that said motor is an electric machine according to any one of claims 1 to 6.