Three phase machine, hydraulic pump and method for operating a three phase machine

Abstract

To achieve both effective heating and loss reduction.SOLUTION: In a three phase alternating current machine which operates in a fluid and has a stator 110 with at least three coils 111, etc., and a rotor 120 with at least one magnet 125, the rotor is surrounded by the at least three coils in a cross-sectional plane perpendicular to a rotation axis R of the rotor. The three phase machine includes a control device 130, which is configured to selectively energize the three coils with three alternating currents, to trigger a working mode, in which the three alternating currents generate a torque about the axis of rotation on the rotor, and to trigger a heating mode, in which the three alternating currents generate an increased power loss in comparison to the working mode due to a faster polarity reversal in at least one of the three alternating currents.SELECTED DRAWING: Figure 1A

Description

[Technical Field]

[0001] The present invention relates to a three-phase AC machine, a hydraulic pump, and a method for operating a three-phase AC machine, and more particularly to a heating function for an electric motor utilizing iron or hysteresis and / or ohmic losses when exciting the coils in an electric motor or a three-phase AC machine in general.

[0002] Self-heating in electric motors is primarily caused by ohmic losses in copper components (e.g., coils, cages, etc.). This heating is fundamentally undesirable because it results in inefficient energy utilization and can lead to overheating of the electric motor. However, in some applications, such as electric motors operated in oil / hydraulic fluid or at specific ambient conditions (e.g., cold temperatures), this thermal effect can be utilized to heat the hydraulic fluid within the motor. Heating the coil heats the hydraulic fluid, which reduces its viscosity, which in turn reduces friction. Therefore, the motor requires less torque to overcome this friction. Such motors are described, for example, in WO 2020 / 173755. To remain functional even at cold temperatures, the rotor surface in such applications is typically configured so that friction is reduced as well as possible by the liquid. However, this results in complex tooling structures for the rotor sheet metal.

[0003] Therefore, the heating effect is very significant, but only has drawbacks afterwards. For this reason, in motor construction, ohmic losses are usually kept as small as possible in order to reduce the continuous heating of electric motors and thereby increase the efficiency of the motor. This is achieved, for example, by keeping the internal resistance of the coils as small as possible.

[0004] Unfortunately, this structural constraint reduces the positive effect of ohmic losses during self-heating at low temperatures. Therefore, there is a need for new motor structures that offer a compromise between effective heating and the smallest possible losses after heating.

[0005] The above problem is solved at least in part by a three-phase alternating current machine according to claim 1, a hydraulic pump according to claim 7 and a method according to claim 10. The dependent claims define further advantageous embodiments of the subject matter of the independent claims.

[0006] The present invention relates to a three-phase AC machine, which operates at least partially in a fluid and has a stator with at least three coils and a rotor with at least one magnet, the rotor being surrounded by the at least three coils in a transverse plane perpendicular to the axis of rotation of the rotor. The three-phase AC machine further includes a controller, which: Three alternating currents are selectively applied to three coils, Triggering a working mode in which three alternating currents are applied to the rotor to generate torque around the axis of rotation; A faster polarity alternation in at least one of the three alternating currents triggers a heating mode in which the three alternating currents produce increased loss power compared to the working mode. It is structured as follows.

[0007] It is clear that a separate alternating current can flow through each of the three coils, and the alternating currents can be controlled by a controller with respect to phase, period, and amplitude, forming a three-phase alternating current from the three phases together. The magnetic field generated by the coils is superimposed on a rotating magnetic field that drives the rotational motion of the rotor (in the working mode). It is also clear that the working mode and the heating mode can be superimposed, since the individual alternating currents can be superimposed, for example, to perform heating before starting a run (at a standstill) and final heating to the optimum operating temperature while the run is in progress.

[0008] In the heating mode, a force can be exerted on the rotor or magnet, but the current can be chosen so that the rotational forces cancel out to zero. However, the force can be exerted in the radial direction of the magnet or in the axial direction of the magnetic flux in the rotor (e.g., of the magnet). However, these (radial) forces do not generate torque, but generate heat by polarity reversal.

[0009] According to each embodiment, the three-phase AC machine is a radial flux machine in which the magnetic flux extends radially through the coils.

[0010] Optionally, the control device is configured to operate the three-phase AC machine alternatively in a working mode or a heating mode, where no torque is generated. The alternating current generates only loss power. In particular, the heating mode can be implemented only before the start of driving. Thus, according to the respective embodiments, in a vehicle having a three-phase AC machine, the temperature of the fluid can be detected first when the ignition is switched on, and if heating of the corresponding unit (e.g., hydraulic pump or steering assist) is recommended, the control device can first initiate the heating mode based on the detected temperature. If the operating temperature is reached, feedback can be provided to the driver, who can then switch to the working mode or drive the vehicle.

[0011] Optionally, the three-phase AC machine is connectable to a DC voltage source, and the control device is further configured to apply DC voltages with alternating polarity to the at least three coils and to vary (increase or decrease) the edge steepness when the polarity alternates in the heating mode compared to the working mode.

[0012] Optionally, the controller is configured to apply DC voltages of alternating polarity to at least three coils by pulse width modulation of controlled amplitude, in this case three different voltages, which can generate a current vector without generating torque.

[0013] Three-phase AC machines typically operate on an alternating current consisting of three phases, each phase shifted 120° from the other. The voltage transitions have a trapezoidal shape, alternating between positive and negative polarity. In this case, a positive DC current is applied to one phase, while a negative DC current is applied to the other coils, shifted in time relative to this phase. The remaining coils are then in a no-load state (i.e., no voltage is applied to them, i.e., a floating state). The heating output can be adjusted by lengthening or shortening the transition from positive to negative polarity or from negative to positive polarity. This results in a transition phase with a greater or lesser edge steepness. This edge steepness results in a faster magnetization reversal in the magnetic material of the three-phase AC machine, which in turn results in greater losses and thus the desired heat generation.

[0014] According to the respective embodiments, the instants of the zero crossings may remain the same, only the edges may be rotated. In other words, the switch-on phase does not have to be shifted as a whole, but only extended symmetrically on both sides. This results in a shorter switch-off phase, during which no voltage is applied, which in turn forces a faster polarity reversal.

[0015] Optionally, the three alternating currents can be combined into d and q currents in a coordinate system that can move with the rotor. The d current generates a magnetic flux that does not generate torque in the rotor and therefore may be considered or referred to as a heating current. The q current generates a magnetic flux that generates torque in the rotor and therefore may be considered or referred to as a work current (three-phase AC). In that case, the controller can be configured to generate (only) the d current (heating current) in heating mode. Therefore, the motor does not generate rotational force. It is obvious that the q and d currents can be composed of multiple different partial currents flowing through the individual coils.

[0016] Therefore, according to each embodiment, the heating output can be controlled by controlling the d current, while the torque of the three-phase AC machine, and therefore the rotational output, can be controlled by controlling the q current.

[0017] Optionally, the stator and / or rotor have motor laminations made of at least one of the following materials: carbon steel, stainless steel, manganese steel, silicon steel, and M12 or M15 silicon steel sheet. This allows for the use of very low-quality silicon steel sheet, with its associated increased hysteresis losses. The materials used can have less desirable electromagnetic properties, favorable for cost savings (e.g., M12 or M15 silicon steel sheet) or for improved mechanical properties (e.g., carbon steel or stainless steel).

[0018] Optionally, the stator and / or rotor include motor laminations having short circuits between the metal sheets in the axial direction of the motor laminations at predetermined locations to increase eddy current losses in a controlled manner. The predetermined locations may be determined so as to effectively generate eddy currents (i.e., so as to generate current flows that are as uniform and closed as possible).

[0019] Thus, according to each embodiment, a material with large hysteretic losses is utilized, while for the electrical traces (e.g. in the coil) a material with small ohmic losses (e.g. copper) is used.

[0020] Optionally, the control device includes a cooling device with a thermal bridge that dissipates the generated heat into the interior space. For example, the control device may include a printed circuit board with active electronic components (e.g., power transistors) that generate a significant amount of heat during operation. According to various embodiments, this heat can also be used to heat the fluid, and for this purpose, a thermal bridge can be used, for example.

[0021] Optionally, the three-phase AC machine is a permanent magnet synchronous motor (PMSM), for example with field-oriented control, in which a permanent magnet is used as an exciter. However, according to further embodiments, the three-phase AC machine may also be an asynchronous motor, a reluctance motor, a BLDC (brushless direct current motor), etc.

[0022] Each embodiment also relates to a hydraulic pump for hydraulic fluid, the hydraulic pump comprising one of the three-phase alternators described above. The interior space of the three-phase alternator contains a portion of the hydraulic fluid. Furthermore, a seal is formed to seal the interior space with the hydraulic fluid from a control device and / or other components. In particular, the three-phase alternator may be fully or partially immersed in the hydraulic fluid.

[0023] The hydraulic pump may be used for various assistance units of a vehicle, such as a truck or other commercial vehicle. In particular, the embodiments also relate to a power steering with a hydraulic pump.

[0024] Each embodiment also relates to a vehicle system including the above-described hydraulic pump and / or three-phase AC machine. The vehicle system may be at least one of a power steering system, a brake system, a system including a ball screw drive mechanism, and a clutch actuation device including a ball screw drive mechanism.

[0025] The embodiments also relate to a vehicle, in particular a truck, equipped with a three-phase alternator and / or power steering and / or vehicle system as described above.

[0026] Embodiments also relate to a method for driving a three-phase AC machine, the method comprising: Selectively energizing three alternating currents through three coils; In the working mode, generating torque in the rotor by three alternating currents (or by a rotating magnetic field generated by the alternating currents); Triggering a heating mode in which the three alternating currents produce increased loss power compared to the working mode by a faster polarity alternation in at least one of the three alternating currents; Includes.

[0027] For example, in the heating mode, an increased amplitude may be generated in at least one of the three alternating currents compared to the working mode.

[0028] It is self-evident that all the above-described functions of the control device can be configured as further optional method steps. Furthermore, it is self-evident that the order described does not necessarily imply the order in which the method steps are performed. The steps may also be performed in another order, or only some of the method steps may be performed.

[0029] The method, or at least parts thereof, may also be implemented or stored in software or in the form of instructions on a computer program product, which, when executed on a processor, are capable of performing the steps of the method. Accordingly, the present invention also relates to a computer-readable storage medium having stored thereon software code (software instructions) configured to perform one of the above-described methods when executed on a processing unit. The processing unit may be any form of computer or control unit having a corresponding microprocessor capable of executing the software code. Accordingly, the embodiments also relate to a computer-readable storage medium having stored thereon instructions configured, when executed on a data processing unit, to cause the above-described three-phase AC machine control device to perform the above-described method.

[0030] Advantageous aspects of each embodiment can be summarized as follows: Each embodiment solves at least part of the above-mentioned technical problem by utilizing core or hysteresis losses in the metal sheets of the motor laminations as a heat source to bring the fluid up to operating temperature as quickly as possible. In this case, rapid switching of the positive and negative signs of the applied direct current results in rapid polarity alternation (from "+" polarity to "-" polarity and from "-" polarity to "+" polarity). This in turn causes rapid magnetization reversal and thus the desired hysteresis losses. The available dissipated heat depends on the speed of the polarity reversal. Thus, according to each embodiment, hysteresis losses are intentionally increased while ohmic losses (due to ohmic resistance) are kept small, since ohmic losses would otherwise result in excessive heat loss even in normal operation.

[0031] To this end, embodiments may utilize intelligent control techniques to proactively bring fluid viscosity within a standard range upon start-up of a vehicle or system (e.g., a hydraulic unit such as a pump).

[0032] Each embodiment of the present invention will be better understood from the following detailed description of several different embodiments and the accompanying drawings, which should not be construed as limiting the disclosure to specific embodiments, but are merely used for explanation and understanding. [Brief explanation of the drawings]

[0033] [Figure 1A] 1 is a diagram showing a three-phase AC machine according to an embodiment of the present invention; [Figure 1B] 10A and 10B are diagrams illustrating driving of coils according to each embodiment. [Figure 2] 1A-1C show cross-sections through the axis of rotation of a three-phase AC machine and the forces acting according to various embodiments. [Figure 3] FIG. 1 shows the voltage progression of all three phases. [Figure 4] FIG. 1 shows a schematic flow chart of a method for driving a three-phase AC machine according to embodiments.

[0034] FIG. 1A illustrates a three-phase AC machine according to one embodiment of the present invention. The three-phase AC machine includes a stator 110, a rotor 120, and a controller 130. The stator 110 includes at least three coils 111, which are typically embedded in a motor lamination 116. The stator 110 may be fixedly connected to a housing of the three-phase AC machine. The rotor 120 includes at least one magnet 125 and is coupled to a shaft 60 through which the rotor 120 provides torque M during operation (e.g., for a pump or servo drive). The rotor 120 is rotatably supported within an interior space 50 of the three-phase AC machine about a rotational axis R of the shaft 60. A fluid, such as oil, or other liquid having a temperature-dependent viscosity may be provided within the interior space 50.

[0035] In a transverse plane perpendicular to the rotation axis R, the at least three coils 111 are arranged in a circular ring shape around the rotor 120, at angular intervals of, for example, 120° or 60° (e.g., when six coils are provided). According to a further embodiment, the three-phase AC machine includes at least three busbars between the control device 130 and the at least three coils 111, for selectively energizing the coils 111 with three alternating currents. The control device 130 is configured to control the three alternating currents. The three-phase AC machine can be connected to a DC voltage source via a connector provided on the housing. The DC voltage can be supplied to the control device and converted there into three desired alternating currents via switches (e.g., power transistors), which are then supplied to the coils via the busbars 136.

[0036] According to a further embodiment, the three-phase AC machine includes a thermal bridge 135 between the controller 130 and the interior space 50, which provides a thermal coupling between heat-generating components (e.g., power transistors) of the controller 130 and the interior space 50, thereby causing heat to flow from the controller 130 to the fluid inside the stator 110. This heat therefore also contributes to the rapid heating of the fluid.

[0037] The exemplary motor laminations 116, in which at least three coils 111 are embedded as encapsulants, also form the coil core and may comprise thin metal sheets (e.g., made of iron or steel) stacked in layers. The constant magnetization reversal during operation results in losses, also referred to as iron losses. According to embodiments, it is not necessary to use iron or steel for the motor laminations 116; other (ferro)magnetic materials can also be used. Advantageously, a material is used that has sufficient hysteresis loss to controllably generate sufficient heat. According to embodiments, to generate sufficient heat, the very hysteresis loss should not be minimized.

[0038] 1B shows an embodiment for driving the three coils 111 by the control device 130. In particular, the voltage progression V is shown as a function of time T, this voltage progression V being exemplarily shown for only one of the three coils 111. The voltage V alternates between a positive supply voltage +VCC and a corresponding negative supply voltage −VCC, which may be two poles of a DC voltage source or may be provided by an optional voltage converter.

[0039] The first voltage transition 132 (solid line) represents the normal operating mode. Positive polarity (+VCC) is applied to the coil 111 until a first time T1. At time T1, the connection to +VCC is disconnected and the voltage drops continuously. At a fifth time T5, negative polarity (-VCC) is applied to the coil 111. This polarity is maintained until a sixth time T6, at which point the coil 111 is again disconnected from the voltage supply. At a tenth time T10, positive polarity +VCC is again applied, and the voltage gradually increases between times T6 and T10. The application and disconnection of polarities +VCC and -VCC are controlled by the control device 130 according to the respective embodiment. The edge steepness 131 between both positive and negative polarities does not need to be driven by the control device 130 but is set automatically. The corresponding contacts may be open ("floating") during this time, so the potential changes gradually. However, the edge steepness 131 is determined by the time period between the tenth time point T10 and the sixth time point T6. This results in a trapezoidal alternating current for the example coil 111.

[0040] The second voltage transition 134 (dashed line) shows an example for driving one coil 111 by the control device 130 in the heating mode. In the heating mode, the control device 130 controls the alternating current so that a loss output increased compared to the working mode (voltage transition 132) is generated by the coil. In the illustrated example, the increase in the loss output is caused by a faster polarity alternation in at least one or all three alternating currents. In the heating mode, the polarity alternation is performed between the second time point T2, which is the time point at which the positive polarity +VCC is maintained at the end, and the fourth time point T4, at which the negative polarity -VCC is applied. The second time point T2 and the fourth time point T4 may be arbitrarily selected, and a faster polarity alternation is achieved when T2>T1 and T4<T5 hold.

[0041] The same applies to the polarity alternation from the negative polarity to the positive polarity. In this case, in the heating mode, for example, the negative polarity remains applied until the seventh time point T7, and the positive polarity is applied at the ninth time point T9. The seventh time point T7 and the ninth time point T9 may also be arbitrarily selected, and a faster polarity alternation is achieved by T7>T6 and T9<T10 holding. As a result, the edge steepness 133 in the polarity alternation in the heating mode increases compared to the working mode.

[0042] According to various embodiments, the time points of zero crossings during operation of or within the heating mode can remain constant over time. In FIG. 1B , the first zero crossing occurs at the third time point T3 in both the first voltage transition 132 (working mode) and the second voltage transition 134 (heating mode). (The voltage value at the third time point T3 is zero or corresponds to the average value of the positive and negative supply voltages.) The second zero crossing from negative polarity to positive polarity occurs at the eighth time point T8, which may also be the same (i.e., occur at the same time) in both the working mode and the heating mode. Thus, when transitioning from the working mode to the heating mode, only the edge steepness 131, 133 can be changed so that the period (duration) at positive polarity +VCC remains the same as the period with negative polarity -VCC. That is, even if the individual periods change, the ratio of both periods does not need to be changed.

[0043] However, this need not be the case. According to various embodiments, the controller 130 can optionally trigger polarity alternation, for example, to induce optimal / maximum heat generation without triggering rotational movement of the rotor 120.

[0044] The control device 130 may further be configured to cause continuous transitions from the working mode to the heating mode and from the heating mode to the working mode. If an edge steepness 131 exists in the working mode (see FIG. 1B), this angle can be continuously increased to a new angle (edge ​​steepness 133) in the heating mode. In the working mode, for example, three alternating currents can be selectively applied to at least three coils 11, such that at each time, exactly one coil is applied with a positive polarity and exactly one other coil is applied with a negative polarity. The period of application of the positive / negative polarity can correspond to a 120° angular movement of the rotor 120 about the rotation axis R. On the other hand, in the heating mode, there can be periods during which a positive (or negative) supply voltage is applied to two or more of the coils 111. Thus, forces can be applied in different directions (e.g., two coils, rather than just one, act to attract the rotor 120 at a given time). This overlap also results in losses. This is because the rotating magnetic field is weakened and radial (loss) forces act, which generate heat.

[0045] 2 shows a cross-sectional view perpendicular to the axis of rotation R, illustrating the forces acting to generate torque M by a three-phase AC machine. For simplicity, only magnet 125 of rotor 120 is shown, with three coils 111, 112, and 113 arranged around magnet 125 at an exemplary interval of 120°. The three coils include first coil 111, second coil 112, and third coil 113, and can be excited by a three-phase AC current consisting of phases A, B, and C.

[0046] In the illustrated state, a negative polarity -VCC is applied to the first coil 111, a positive polarity +VCC is applied to the third coil, and no voltage is applied to the second coil 112, i.e., the control device 130 is letting the potential in the second coil 112 freely "float" at the time of illustration. The three coils 111, 112, and 113 are electrically connected to each other, for example, at the sides to which earth potential or zero voltage (= the average value of +VCC and -VCC) is applied, and the positive polarity +VCC and negative polarity -VCC can be applied to the ends of the coils 111, 112, and 113 that are not connected to each other.

[0047] Here, rotation of rotor 120 is caused by gradual changes in polarity in each coil, which creates a continuously changing magnetic field and an alternating force acting on magnet 125. In the illustrated state, first coil 111 attracts, for example, the black pole of magnet 125, and second coil 113 attracts the white pole of magnet 125. Magnet 125 is in a balanced state, aligned along magnetic flux vector 230. The alternating polarities result in a rotating magnetic field that rotor 120 follows because rotor 120 always aligns its longitudinal axis with (rotating) magnetic flux vector 230. Thus, magnetic flux vector 230 can jump from one to another, causing magnet 125 to rotate to the new magnetic flux vectors 241 and 242. The continuous polarity alternation generates a rotational force 220, and therefore a torque M, that can act on or be emitted from the rotor 120. The alternating current that generates the rotational force 220 is referred to as the q current Iq.

[0048] However, according to the embodiments, the same polarity, i.e., -VCC or +VCC, can be applied simultaneously to both coils in the heating mode. Therefore, in the illustrated position, the second coil 112 can be positioned at -VCC without "floating." This would no longer generate a rotating magnetic field during polarity alternation. However, sudden changes that the magnet 125 cannot follow with rotational motion can occur. This means that longitudinal forces 210 are generated that do not contribute to the rotational motion but are lost as energy and ultimately converted into heat. If the current is selected so that all rotational forces are compensated for and only radial forces 210 are still generated, these forces act only in the radial direction of the polar coordinate system in FIG. 2, and therefore all energy is converted into heat. This current is also referred to as the d current Id.

[0049] According to various embodiments, the control device 130 can control the alternating current to perform an oscillating angular motion of the rotor 12 (rapid back and forth rotation) within a predetermined angular range, which results in additional heating of the fluid. According to a further embodiment, when the three-phase AC machine is at standstill, an alternating D current Id is generated that produces a longitudinal force 210 (along the longitudinal axis of the magnets 125) but no rotational motion. In both cases, rapid polarity reversals can be performed, which result in hysteresis losses and thus engine heating without producing a continuous torque (of a predetermined sign).

[0050] Then, when going into the working mode, a q current Iq is generated which generates a torque in the rotor 120. The d current Id may be switched off immediately, but this is not necessary: ​​only when the three-phase AC machine has reached its operating temperature can the d current Id be switched off with its associated losses.

[0051] That is, according to the respective embodiments, the three currents flowing through the three coils 111, 112, 113 can be selected so that in the heating mode, no q current Iq is generated, but instead a large d current Id is generated that varies as fast as possible, while in the working mode a large q current Iq is generated and the d current Id is avoided as much as possible. In this way, the maximum useful power output by the three-phase AC machine can still be guaranteed for a given current.

[0052] 3 illustrates the switching of DC voltages at several different coils 111, 112, 113. The voltage profiles for each coil 111, 112, 113 are shown, here as a function of the angle of the rotor 120 (or magnet 125). The upper diagram shows, by way of example, the voltage profile for the first coil 111, which is at a positive polarity +VCC, which is switched off at an angle of 120°. At an angle of 180°, a negative polarity −VCC is applied to the first coil 111, which remains at the negative polarity −VCC until an angle of 300°. The voltage is then switched off again at the first coil 111, and finally, at an angle of 360°, +VCC is applied again, for example.

[0053] The second coil 112 is driven in a similar manner, but this time with a phase shift of 60°, i.e., −VCC is applied to the second coil 112 initially, and more specifically up to an angle of 60°. Between 60° and 120°, no voltage is applied. Between 120° and 240°, +VCC is applied. Between 240° and 300°, no voltage is applied, and between 300° and 330°, −VCC is applied.

[0054] The third coil 113 again has the same pattern, but here there is also a 60° phase shift, i.e. at an angle of 60°, -VCC is applied to the third coil 113 and remains at -VCC up to an angle of 180°. Between 180° and 240° no voltage is applied. Between 240° and 360° +VCC is applied, then at 360° +VCC is again switched off.

[0055] The lower diagram shows superimposed voltage profiles 311, 312, 313 for the individual coils 111, 112, 113, where the first voltage profile 311 shows the voltage alternation for the first coil 111, the second voltage profile 312 shows the voltage alternation for the second coil 112, and the third voltage profile 313 shows the voltage alternation for the third coil 113. Linear edges are formed between the positive polarity +VCC and the negative polarity -VCC. No voltage is actively applied at these linear edges, but the potentials present there change automatically in the circuit, and this change is not necessarily linear.

[0056] The 60° phase shift essentially results in a positive voltage (+VCC) being applied to exactly one of the three coils 111, 112, 113 at each instant in time, and a negative voltage (-VCC) being applied to exactly one of the three coils 111, 112, 113. The respective defined voltages are not coupled to the remaining coils.

[0057] According to various embodiments, the control device 130 intentionally disrupts this symmetry. For example, the control device 130 can intentionally vary the activation periods 320 of the coils 111, 112, and 113, i.e., the time during which +VCC or −VCC is applied to them. The activation periods can be, for example, continuously lengthened or shortened. Similarly, the switch-off periods 330 (when no potential is applied to the coils) can be continuously shortened. This allows the control device 130 to control the edge steepness of polarity alternations that are performed more rapidly (less than 60° of rotational movement). For example, the switch-off periods 330 can be only 40°, 20°, or 0°. If this were to be done for all coils, opposing forces would be generated, which would not generate a (pure) rotational force as described above, but would act radially (in the direction of the magnet 125). To achieve this, the control device 130 generates a current d Id which, according to the respective embodiment, can be used to heat the fluid in the interior space 50. In particular, the drive can be implemented in such a way that the rotational movement of the rotor 120 is prevented or at most vibrations are generated.

[0058] 4 shows a schematic flow chart of a method for driving a three-phase AC machine according to embodiments, the method comprising the following steps: Step S110 of selectively energizing three alternating currents to the three coils 111, 112, and 113; Step S120 of generating torque M on the rotor 120 by three alternating currents in the working mode; a step S130 of triggering a heating mode in which a faster polarity alternation in at least one of the three alternating currents results in the three alternating currents having an increased loss power compared to the working mode; Includes.

[0059] It is clear that all the above-described functions of the control device 130 can be configured as further optional method steps. Furthermore, it is clear that the order described does not necessarily imply the order in which the method steps should be performed. The steps may be performed in another order, or only some of the method steps may be performed.

[0060] The method may be computer-implemented, i.e., the method may be realized by instructions that are stored on a storage medium and that, when executed on a processor, are capable of performing the steps of the method. The instructions include one or more instructions that may be stored in different formats on different media, typically within or surrounding a control unit (with the processor), that, when read and executed by the control unit, cause the control unit to perform the functions, functionality, and operations required to perform the method according to the present invention.

[0061] The advantageous aspects of each embodiment can be summarized as follows: The desired heating is achieved by rapidly changing the magnetic field, which results in the desired core / hysteresis losses. This heat is transferred to the air gap (internal space 50), where the fluid (e.g., oil or other liquid) is heated, thereby reducing the fluid's viscosity. If the control device 130 operates the three-phase AC machine in heating mode, the control device 130 can correspondingly increase the edge steepness 131, 133 between polarity alternations, which is equivalent to shortening the coil switch-off period 330. Through the speed of the polarity alternation achieved in this way, losses can be set or the heat generation by the three-phase AC machine can be controlled. The faster the polarity changes, the faster the magnetization in the material changes, which leads to increased losses and therefore heat generation.

[0062] According to embodiments, the material for the motor laminations 116 is adapted to enhance this effect. For example, a material with a larger hysteresis loss can be employed, which is considered a poor quality for conventional electric motors and is therefore avoided. According to embodiments, for example, at least one of the following materials can be utilized for the motor laminations 116: carbon steel, stainless steel, manganese steel, silicon steel.

[0063] The use of a metal sheet with higher losses combined with fast switching of the Id current during start-up facilitates the fast heating achieved by the embodiments, which offer the possibility of heating the liquid in the interior space 50 even in electric motors with low ohmic resistance.

[0064] A further advantage is that each embodiment can be used in all areas within the motor air gap 50 where a liquid that increases in viscosity at relatively low ambient temperatures is present.

[0065] Each embodiment can combine two main components: one is the motor (three-phase AC machine) structure, where materials with larger hysteresis losses can be selected to increase heating at relatively low temperatures, and the second is the control by the controller 130, which controls heating by rapidly switching the sign of the DC current at system start-up.

[0066] Cost advantages are also achieved in the manufacture of three-phase AC machines or electric motors, since the need for complex tooling for the rotor sheet metal is eliminated.

[0067] The embodiments are applicable to electric power steering systems that require operation at ambient temperatures between -40°C and +85°C, for example. To increase the motor's efficiency and reduce heating at, for example, 85°C, the ohmic losses of the exemplary permanent magnet synchronous motor (PMSM) are kept low. At low temperatures, the exemplary hydraulic fluid in the air gap of a conventional power steering system becomes very viscous, which requires a very large torque to drive the pump during start-up. This conventional hydraulic system heats up only slowly due to the small ohmic losses. The embodiments significantly improve the situation, since only time-limited heating is possible through control.

[0068] As previously mentioned, embodiments utilize hysteresis losses in the laminations of the stator 110 and / or rotor 120 for this purpose. These hysteresis losses are achieved by rapidly switching the sign of the applied DC current (from +VCC to −VCC and from −VCC to +VCC). This loss generates additional heat, causing the metal sheets of the motor laminations 116 to act as a heat source. The laminations 116 then dissipate their heat into the air gap 50. This allows the viscosity of the hydraulic fluid to be reduced more quickly, thereby enabling the motor to transition to normal operating mode more quickly.

[0069] The features of the invention disclosed in the description, the claims and the drawings may, both alone and in any combination, be essential for realizing the invention. [Explanation of symbols]

[0070] 50 Interior Space 60 shaft 110 Stator 111,112,113 At least three coils 116 Motor Laminate 120 rotor 125 at least one magnet 130 Control device (controller, electronic control unit) 131 Edge steepness (angle) in working mode 132 Voltage transition in working mode 133 Edge steepness (angle) in heating mode 134 Voltage transition in heating mode 135 Heat Bridge 136 Busbar 210 Radial Force 220 Torque 230,241,242 Rotating magnetic flux vector (generated by Iq) 311, 312, 313 Voltage transition in coil 320 Switch-on period 330 Switch-off Period R rotation axis M Torque Id d current (heating current) Iq q current (working current) +VCC Positive polarity (of applied DC voltage) -VCC Negative polarity (of applied DC voltage)

Claims

1. A three-phase AC machine, The three-phase AC machine operates at least partially in a fluid and has a stator (110) with at least three coils (111, 112, 113) and a rotor (120) with at least one magnet (125); The rotor (120) is surrounded by the at least three coils (111, 112, 113) in a transverse plane perpendicular to the rotation axis (R) of the rotor (120). In three-phase AC machines, A control device (130) is provided, the control device (130) comprising: - selectively energizing the three coils (111, 112, 113) with three alternating currents; triggering a working mode in which the three alternating currents generate a torque (M) about the axis of rotation (R) on the rotor (120); A faster polarity alternation in at least one of the three alternating currents triggers a heating mode in which the three alternating currents produce an increased loss power compared to the working mode. A three-phase AC machine characterized by being configured as follows.

2. the control device (130) is configured to operate the three-phase AC machine alternatively in the working mode or the heating mode; In the heating mode, no torque (M) is generated.

2. The three-phase AC machine according to claim 1.

3. the three-phase AC machine is connectable to a DC voltage source; The control device (130) applying a DC voltage with alternating polarity (+VCC, −VCC) to the at least three coils; Increasing edge steepness (131, 133) when alternating polarity in the heating mode compared to the working mode.

3. The three-phase AC machine according to claim 1, further comprising:

4. the control device (130) is configured to apply the DC voltages with alternating polarities (+VCC, −VCC) to the at least three coils by pulse width modulation of controlled amplitude; 4. The three-phase AC machine according to claim 3.

5. the three alternating currents are combinable into d-currents (Id) and q-currents (Iq) in a coordinate system movable with the rotor; The d current (Id) generates a magnetic flux in the rotor (120) that does not produce a torque (M); The q current (Iq) generates a magnetic flux that generates a torque (M) in the rotor (120); The control device (130) is configured to generate the d current (Id) in the heating mode.

5. A three-phase AC machine according to claim 1.

6. The stator (110) and / or the rotor (120) have motor laminations (116) made of at least one of the following materials: carbon steel, stainless steel, manganese steel, silicon steel, M12 or M15 silicon steel sheet; 6. A three-phase AC machine according to any one of claims 1 to 5.

7. the stator (110) and / or the rotor (120) have motor laminations; the motor laminations have axial short circuits between the lamination metal sheets at predetermined locations to increase eddy current losses in a controlled manner; 7. A three-phase AC machine according to any one of claims 1 to 6.

8. The control device (130) includes a cooling device with a thermal bridge (135) that dissipates generated heat into the interior space (50).

8. A three-phase AC machine according to any one of claims 1 to 7.

9. The three-phase AC machine is configured as a permanent magnet synchronous motor.

9. A three-phase AC machine according to any one of claims 1 to 8.

10. A hydraulic pump for hydraulic fluid, comprising a three-phase AC machine according to any one of claims 1 to 9, The internal space (50) contains a portion of the hydraulic fluid and has a seal for sealing the internal space (50) containing the hydraulic fluid from a control device (130). Hydraulic pump.

11. A vehicle system comprising the hydraulic pump according to claim 10 or the three-phase AC machine according to any one of claims 1 to 9.

12. the vehicle system is at least one of a power steering system, a brake system, a system with a ball screw drive mechanism, and a clutch actuation device with a ball screw drive mechanism; 12. The vehicle system of claim 11.

13. A vehicle, in particular a truck, equipped with a three-phase alternating current machine according to any one of claims 1 to 9 and / or a vehicle system according to claim 11 or 12.

14. 2. A method for driving a three-phase AC machine according to claim 1, comprising: The method comprises: A step (S110) of selectively energizing three alternating currents to three coils (111, 112, 113); - in a working mode, generating a torque (M) on the rotor (120) by the three alternating currents (S120); triggering a heating mode (S130) in which a faster polarity alternation in at least one of the three alternating currents causes the three alternating currents to produce an increased loss power compared to the working mode; A method comprising:

15. In the heating mode, an increased amplitude is generated in at least one of the three alternating currents compared to the working mode.

15. The method of claim 14.

16. A computer-readable storage medium having instructions stored thereon, comprising: The instructions, when executed on a data processing unit, are configured to cause the controller (130) for a three-phase AC machine of claim 1 to perform the method of claim 14. A computer-readable storage medium.

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