Electric machine with permanent magnets and control device therefor

Abstract

The invention relates to a rotor lamination core arrangement (100) comprising a rotor lamination core (101) and at least one permanent magnet (102) arranged at or in the rotor lamination core (101), wherein the permanent magnet (102) has a functional layer (105) for detecting an exceeding and / or falling below a threshold temperature of the permanent magnet (102), wherein the functional layer (105) changes its magnetic properties when exceeding and falling below the threshold temperature, so that an exceeding and / or falling below the threshold temperature of the permanent magnet (102) can be detected. The invention also relates to a rotor arrangement (111), a rotating electrical machine, a method for controlling a rotating electrical machine and a control unit for controlling a rotating electrical machine.

Description

BACKGROUND

[0001] DE 10 2013 222 208 A1 relates to a method for evaluating the temperature of a magnet at a rotating element of a rotating electrical machine. It is provided that when at least the rotating element of the rotating electrical machine is cooled by a coolant, a magnet temperature evaluation device evaluates the magnet temperature on the basis of the temperature of the coolant and the losses of the rotating element together with the magnet. SUMMARY

[0002] Rotating electrical machines, in particular permanently excited rotating electrical machines, are used in different construction forms and size or power classes (e.g. window lifters, micro-motors, up to traction drives in automobiles and generators in wind power plants). They are distinguished by a high power density (per mass or per volume) and are therefore mainly important for non-stationary applications.

[0003] Permanent excitation is produced in these machines with permanent magnets (also called hard magnets or permanent magnets). As a material for permanent magnets, ferrum-boron alloys or samarium-cobalt alloys are usually used in machines with a high power density.

[0004] The permanent magnets are magnetized at the end of the manufacturing process or already in the rotor lamination core or in the motor by an external magnetic field. Due to the special magnetism (magnetic properties and high coercive force or resistance to demagnetization) of these materials, these materials retain their magnetization after removal of the external magnetic field and have a so-called leakage field, that is to say a magnetic field outside the permanent magnet, which originates from the permanent magnet. This leakage field is used in permanently excited rotating electrical machines. Permanent magnetic materials have a characteristic temperature T c (Curie temperature). Above this temperature, the material undergoes a phase change, at which the material changes from a ferromagnetic state to a paramagnetic state and thus loses its oriented magnetization, which is important for the application. Directly below the Curie temperature T c , the material becomes ferromagnetic again. However, below the Curie temperature T c , the material no longer has its magnetization, which was initially applied by the external magnetic field, and thus irreversibly loses its properties, which are important for the application in rotating electrical machines. It is therefore important in the design and operation that the permanent magnets cannot be subjected to temperatures which irreversibly reduce or affect the permanent magnetic properties. The temperature at which this irreversible change (partial demagnetization) occurs can be partially below the nominal Curie temperature T c of the permanent magnet due to statistical processes.

[0005] The invention relates to a rotor lamination core arrangement, a rotor arrangement, a rotating electrical machine, a method for controlling a rotating electrical machine and a control unit for controlling a rotating electrical machine.

[0006] The advantage of the invention with the features of the independent claims is that temperature measurement can be performed wirelessly and space-saving directly at the permanent magnet, wherein the temperature measuring device can be operated with little additional expenditure. In particular, no complex cutouts in the rotor lamination core (lamination stack) are required and no large recesses around the permanent magnet, so that the magnetic field of the permanent magnet is not disturbed and the power of the rotating electrical machine is therefore advantageously maintained. A further advantage is that, with the aid of the invention, it is possible to detect temperatures above and / or below a threshold value. It is therefore possible, in particular, to introduce measures for cooling, for example, by means of a control unit, in order to maintain the effective power of the rotating electrical machine.

[0007] This is achieved by a rotor lamination core arrangement comprising a rotor lamination core and at least one permanent magnet arranged at or in the rotor lamination core, wherein the permanent magnet has a functional layer for detecting a threshold temperature of the permanent magnet, wherein the functional layer changes its magnetic properties when the threshold temperature is exceeded and / or undershot, whereby it is possible to detect that the permanent magnet has exceeded and / or undershot the threshold temperature.

[0008] The rotor lamination arrangement preferably comprises at least two permanent magnets, wherein at least one of the two permanent magnets has a functional layer.

[0009] As a sheet material for the rotor lamination core, an iron-silicon (Fe-Si) material which is extremely well magnetically conductive is typically used as an electrical sheet.

[0010] The permanent magnet can be arranged in a pocket held in a cutout of the rotor lamination core or on the rotor lamination core. This variant is particularly advantageous for synchronous machines with a high-speed rotor, since an embedded magnet can be used to form the magnetic field in order thus to better control the extreme loads caused by high centrifugal forces.

[0011] Above the Curie temperature of the material, such a material shows a reversible phase change from its ferromagnetic state to its paramagnetic state, wherein the spontaneous or directed magnetization of the crystal regions disappears above the Curie temperature. Below the Curie temperature, the material regains its magnetism, that is to say, it exhibits a spontaneous magnetization of the Weiss domains, provided that no external magnetic field is acting on the material. However, the permanent magnet no longer regains the magnetization initially imparted by the external magnetic field below the Curie temperature. The permanent magnet therefore irreversibly loses its magnetic properties important for use in a rotating electrical machine below the Curie temperature. The permanent magnet can therefore only be used reliably as a magnet material below its Curie temperature.

[0012] Due to statistical processes, partial demagnetization can already occur below the Curie temperature of the permanent magnet, which limits the effective power of the rotating electrical machine. The temperature below the Curie temperature of the permanent magnet is referred to herein as threshold temperature of the permanent magnet (also referred to as temperature threshold, threshold temperature or limit temperature), at which an irreversible change in the magnetism of the permanent magnet is preferably not yet present. The threshold temperature can be, for example, at least 100° or at least 150° below the Curie temperature of the permanent magnet. In particular, a temperature that is sufficiently far removed from the Curie temperature of the permanent magnet should be chosen as the threshold temperature, so that the permanent magnet has sufficient time to react to an adjustment of the operating parameters of the rotating electrical machine comprising the permanent magnet to avoid a further increase in the temperature of the permanent magnet. An irreversible change in the magnetism of the permanent magnet is thus avoided.

[0013] The magnetism of the functional layer can in particular be understood as the magnetization, polarization and / or permeability of the functional layer.

[0014] The functional layer changes its magnetism, in particular the magnetization, polarization and permeability, abruptly and significantly above and / or below the temperature T c (Curie temperature) that is characteristic of the material of the functional layer. The Curie temperature of the functional layer is preferably below the Curie temperature of the permanent magnet. The Curie temperature of the functional layer can in particular correspond to the threshold temperature. The change in the magnetism of the functional layer acts in the magnetic circuit comprising the permanent magnet, the functional layer and the electrical sheet and can be detected by the machine data in operation and, if necessary, measures are introduced by the motor control device, by a phase change from ferromagnetic to paramagnetic or, below the Curie temperature of the functional layer, by a phase change from paramagnetic to ferromagnetic.

[0015] One advantage of the functional layer for monitoring the temperature of the permanent magnet is that direct information about the surface temperature of the permanent magnet or information about the exceeding and / or falling below a specific temperature threshold is obtained. By means of this information, the system can be protected from overheating of the permanent magnet. By detecting whether the temperature threshold is exceeded accurately and in close proximity, the machine can be designed and operated significantly closer to this temperature threshold. Here, no safety buffer has to be observed. The phase change of the material of the functional layer is completely reversible and can be repeated at will. Since, for monitoring the temperature of the permanent magnet, only the permanent magnet is functionally expanded and the machine software for detecting the effect is adjusted, no further components (for example the lamination stack), electronics or new parts have to be adjusted. The existing design, geometry and processes can thus advantageously be retained.

[0016] The layer thickness of the functional layer should not be chosen to be too thick, so that in normal operation, that is to say at temperatures below the Curie temperature of the functional layer (T c), this layer thickness does not excessively shield the magnetic field of the permanent magnet (on which the layer thickness is imposed) and thus negatively influences the functioning of the machine. To ensure this, the layer thickness of the functional layer is preferably less than or equal to 200 m, preferably less than or equal to 50 micrometers ( m), in particular less than or equal to 20 m.

[0017] The functional layer consists of a material that is in a ferromagnetic state at the desired operating temperature of the rotating electrical machine comprising the rotor lamination core arrangement and has a Curie temperature T c .

[0018] For typical motor applications with ferrite-boron magnets as permanent magnets and a Curie temperature of the permanent magnets between 310°C and 340°C, the maximum operating temperature is limited to less than 200°C, at most between 100°C and 160°C (depending on the magnet type).

[0019] For samarium-cobalt magnets with a Curie temperature between 750°C and 825°C, typical operating temperatures of up to 350°C (special Sm2Co 17 alloys up to 550°C) can be achieved. In the case of ferrite-boron magnets as permanent magnets, a material is suitable for use as a functional layer that has a Curie temperature of less than 250°C, in particular in the range from 100°C inclusive to 200°C inclusive (depending on the magnet type), and in which the Curie temperature of the functional layer can be precisely determined at the time of manufacture, for example due to the alloy composition. In samarium-cobalt magnets, in turn, a material is particularly suitable for use as a functional layer that has a Curie temperature in the range of less than or equal to 500°C, in particular in the range from 250°C to 350°C inclusive (at which 250°C and 350°C are included), and in which the Curie temperature of the functional layer can be precisely determined at the time of manufacture, for example due to the alloy composition. In order to make the material from which the functional layer is constructed as good as possible to conduct the magnetic flux of the permanent magnet (which is to say to reduce the magnetic resistance in the magnetic circuit), it is also advantageous for the material of the functional layer to have a high magnetization M, polarization J and a high magnetic permeability , in particular a saturation polarization J s that is greater than 0.5 Tesla (T), preferably greater than 1 T. The relative magnetic permeability r should in particular be greater than 500, preferably greater than 1000.

[0020] Alloys that can be used as a functional layer for monitoring the temperature of the permanent magnet and have a Curie temperature that is suitable as a threshold temperature are, for example, the following:

[0021] • iron-aluminum alloys (Fe-Al alloys), such as Fe3Al with a Curie temperature Tc ~ 300°C, depending on the composition, which can also achieve iron-aluminum alloys with a Curie temperature Tc in the range of 100-200°C (including the edge values).

[0022] • Fe-Al-X alloys, such as (Fe x V 1-x )3Al, whose Curie temperature can be set by the vanadium content (V content), wherein by selecting the vanadium content a Curie temperature of -200°C and 500°C or a value between -200°C and 500°C can be achieved (source: Gautam Ghosh and MSIT®®; Effenberg, G (Edition); SpringerMaterials; 10.19028.2.9 (Springer-Verlag Heidelberg, 2004).

[0023] • nickel (Ni) with a Curie temperature of 354°C and is particularly suitable as a functional layer for temperature monitoring of permanent magnets made of samarium-cobalt alloys.

[0024] • iron-nickel compounds (Fe-Ni compounds), if necessary with the addition of molybdenum (Mo) and / or copper (Cu) and / or further chemical elements, whereby the Curie temperature of the functional layer can be 100°C, 500°C or a value between 100°C and 500°C, depending on the composition of the iron-nickel compound and the optional additives.

[0025] • ferrites with a Curie temperature from including 100°C to including 450°C.

[0026] Further examples of materials that can be used as a functional layer for monitoring the temperature of permanent magnets are:

[0027] • MnFeP with a Curie temperature of 70°C, 100°C or a value between 70°C and 110°C (depending on the composition, that is to say depending on the selection of the value x) 1-x Si x

[0028] • amorphous compounds, such as (Fe,Co) 83 (Si,B) 17

[0029] • Ti (FeCo) 2.3 with a Curie temperature of -70°C to 400°C (depending on the cobalt content)

[0030] • Ce2 (FeCo) 17 with a Curie temperature of about 0°C to 800°C (depending on the cobalt content)

[0031] The aforementioned list is merely exemplary and is not to be understood as final. Further materials whose Curie temperature is suitable as threshold temperature of the permanent magnet can also be used as functional layer for monitoring the temperature of the permanent magnet.

[0032] The functional layer can also partially, preferably < 50 volume percent, in addition to the originally functional crystalline phase (with a Curie temperature corresponding to the threshold temperature) have further crystalline phases, in particular when these crystalline phases cannot be avoided by the manufacturing process and these crystalline phases do not mean a restriction with respect to the functionality.

[0033] The functional layer can be applied to the permanent magnet using conventional methods such as chemical coating methods, vapor deposition methods, sputtering methods, vacuum deposition methods, spray or jet methods, dipping methods, application by means of dispersion, etc.

[0034] In an embodiment, the permanent magnet comprises a protective layer, wherein the protective layer is applied between the permanent magnet and the functional layer or on the side of the functional layer facing away from the permanent magnet. The protective layer can in particular comprise an oxidation protective layer. The oxidation protective layer can for example comprise copper-nickel (Cu-Ni), as a single layer or as a plurality of layers, with a layer thickness of less than 10 m. The oxidation protective layer can be applied first or the functional layer can be applied first, depending on which is more advantageous from a process-technological point of view. The protective layer can alternatively or additionally comprise a passivation layer, wherein the passivation layer can for example comprise a zinc layer, the zinc layer having a layer thickness of a few micrometers, in particular 5 m to 40 m, preferably 8 m to 12 m.

[0035] The functional layer can alternatively or additionally also function as a protective layer, in particular the functional layer can function as an oxidation protective layer. The advantage is that the magnetic resistance in the magnetic circuit is thus kept small and the magnetic flux of the permanent magnet is reliably conducted.

[0036] In an embodiment, the rotor lamination core comprises a first functional layer and a second functional layer, wherein the first functional layer is arranged on a first surface of the permanent magnet, and wherein the second functional layer is arranged on a second surface of the permanent magnet facing away from the first surface. The first and second functional layer are thus applied on two surfaces of the permanent magnet facing away from one another. The surface normal of the functional layer in particular advantageously indicates the preferred direction of the magnetism of the anisotropic permanent magnet typically used. The advantage is that the available magnetic field out of the permanent magnet is thus not reduced. Furthermore, for process-technological reasons, the coating of only two mutually opposite surfaces is much simpler to implement and much more cost-effective.

[0037] According to an embodiment, the functional layer can be configured as a granulate layer, the granulate layer comprising functional granulates and a binding material, wherein the functional granulates are at least partially surrounded by the binding material. The binding material, for example a plastic, can surround the functional granulates and hold them together. The granulates are for example composed of one or more of the above-mentioned materials having the desired T c In this embodiment it is advantageous that the granulates can be injected in a suspension or in a viscous mass into the gap between the permanent magnet and the electrically used plate. In some machine embodiments the permanent magnet is additionally fixed in the rotor lamination core by injecting an epoxy resin into this gap to withstand high centrifugal forces. The addition of functional granulates can advantageously be integrated into the process here.

[0038] According to an embodiment, the permanent magnet of the rotor lamination core arrangement can be composed of ferritic-ferroboron alloy and the Curie temperature of the functional layer has a value of less than or equal to 250°C, in particular a value between 100°C and 200°C.

[0039] According to an embodiment, the permanent magnet of the rotor lamination core arrangement can be composed of samarium-cobalt alloy and the Curie temperature of the functional layer has a value of 350°C or 500°C or a value between 350°C and 500°C.

[0040] In an embodiment, the functional layer comprises a first sublayer having a first Curie temperature and a second sublayer having a second Curie temperature (10512), and wherein the first Curie temperature and the second Curie temperature differ from each other. An advantage is that this functional layer composed of at least two sublayers forms a multi-layer system which enables the realization of a plurality of also different threshold temperatures (= Curie temperature of the functional sublayer) when a multi-level nature of the signal is required. An exact temperature monitoring can thus advantageously be carried out, in particular it can be ascertained in which temperature interval the temperature of the permanent magnet lies and countermeasures can be introduced by the motor control device if necessary.

[0041] The advantages of the rotor arrangement comprising the rotor lamination core arrangement according to the preceding embodiments result from the advantages of the rotor lamination core arrangement.

[0042] A control unit for controlling a rotating electrical machine, the control unit comprising:

[0043] • a receiving unit configured to receive an input signal, wherein the input signal is representative of a magnetic quantity by means of which an exceeding and / or falling below a threshold temperature of a permanent magnet can be detected.

[0044] • a comparison unit which compares the input signal with a reference curve and provides a control signal for setting at least one operating parameter of the rotating electrical machine depending on the detected exceeding and / or falling below the threshold temperature of the permanent magnet, and

[0045] • an output unit for outputting a control signal for setting at least one operating parameter of the rotating electric machine in accordance with the detected exceeding and / or falling below of the threshold temperature of the permanent magnet.

[0046] The receiving unit, the comparison unit and / or the output unit can be configured as part of a motor controller which takes over the control, regulation and monitoring of the motor function. The motor controller can for example have a microcontroller for carrying out the calculation operations, such as the signal comparison, wherein the microcontroller accesses internal and / or external memory (RAM, ROM and Flash) in which for example reference curves or reference data are stored. Furthermore, the motor control device also comprises ASICs and / or FPGAs. The receiving unit and / or the output unit can in particular comprise analog and digital input signals for the sensors and output signals for the actuators integrated into the motor controller. The operating state of the rotating electric machine, for example the energy-saving mode, can for example be adjusted by the motor controller.

[0047] The advantage of the control unit is that the temperature monitoring of the rotating electric machine can be carried out in a simple manner, since only the magnetic variable is monitored, by means of which the exceeding and / or falling below of the threshold temperature of the permanent magnet in the rotor arrangement of the rotating electric machine can be detected. In the case of a determination of the exceeding of the threshold temperature by means of the magnetic variable, such as the reluctance of the magnetic circuit, the magnetic flux, the current / voltage change curve, the electric power, etc., in comparison with a reference curve, measures can be directly introduced by the motor control device in order to for example throttle the power of the machine and to promote cooling. The control unit thus makes it possible to avoid overheating of the permanent magnet (cf. above) and thus achieves a reliable operation of the rotating electric machine. If a falling below of the threshold temperature is determined immediately, the rotating electric machine can be brought again into its normal operating mode by the control signal. An efficient, reliable operation of the rotating electric machine is thus achieved.

[0048] The B(H) characteristic cannot be measured directly in the machine operation. In one embodiment, the difference in the expected machine signal can be calculated by calculating the total magnetic circuit in the rotating electrical machine from two B(H) characteristics of the two states (paramagnetic and ferromagnetic) which can be externally characterized, for example on a pure material. But this signal can alternatively or additionally also be recorded for different operating points before use in the rotating electrical machine, stored in the characteristic curve in the software and thus used as a reference. The signal on the machine level alone is suitable for evaluation, such as the characteristic (power, current, voltage, etc.) or a combination of several characteristic variables which indicate the overall picture. The change in this overall picture of the characteristic variables when the threshold temperature is exceeded must be stored as a reference as described above. In particular, the electrical power or voltage / current change curve of the rotating electrical machine below the Curie temperature (ferromagnetic) and / or above the Curie temperature (paramagnetic) can be stored as a reference curve in a storage unit inside or outside the rotating electrical machine and can be called up by the comparison unit. Figure 5 One example for such a reference curve is shown in the diagram. The magnetic field strength H is plotted on the x-axis of the B-(H) characteristic and the magnetization B on the y-axis. The functional layer is in the magnetic field of the permanent magnet. Depending on whether the functional layer is in the ferromagnetic state or the paramagnetic state, the functional layer in the magnetic field has a different magnetization. By comparing the magnetization represented by the input signal and passed to the receiving unit with the reference curve, it can be determined whether the functional layer is in the ferromagnetic state or in the paramagnetic state, that is to say whether the surface of the permanent magnet has a temperature above the threshold temperature (the functional layer is paramagnetic) or below the threshold temperature (the functional layer is ferromagnetic).

[0049] Furthermore, the reluctance (the functional layer acts as this reluctance in the magnetic circuit) depends on whether the functional layer is in the ferromagnetic state (corresponds to a low reluctance) or in the paramagnetic state (corresponds to a low reluctance compared to the reluctance in the ferromagnetic state). The change in the reluctance can be detected, for example, as a change in the magnetic flux density, wherein the input signal representing the magnetic flux density can be, for example, a voltage, a Hall voltage, etc. The magnetic flux can be measured, for example, with a magnetometer, a Hall sensor or a measurement coil. It can thus be determined from the operating data of the machine whether the threshold temperature is exceeded and / or undershot.

[0050] For example, the rotational speed of the rotor device, the torque of the rotor device or the copper winding of the stator of the rotating electrical machine through which the coil current which drives the rotor device rotates is used as an operating parameter of the rotating electrical machine.

[0051] The advantages of the rotating electrical machine comprising the rotor device result from the advantages of the rotor lamination core device and the rotor device.

[0052] Rotating electrical machines, such as electric motors or generators, are usually composed of a stator and a rotor arrangement arranged in a rotatable manner in the stator. Such a rotor arrangement typically comprises a large number of rotor laminations which are joined to form a so-called rotor lamination core, and a drive unit comprising a drive shaft. Rotating electrical machines can work as three-phase electric motors or also as generators which generate a three-phase current. Rotating electrical machines have mostly external stator windings which generate a magnetic rotating field and in which a voltage is induced. Mostly internal rotors (pole wheels) carry permanent magnets for generating a magnetic field.

[0053] In an embodiment, the rotating electrical machine comprises the above-mentioned control unit, wherein the control unit is configured to provide a control signal for setting at least one operating parameter of the rotating electrical machine when a threshold temperature of the permanent magnet is exceeded and / or undershot. Advantages result from the above-mentioned advantages of the control unit.

[0054] A method for controlling a rotating electrical machine, comprising the following steps:

[0055] • determining that a threshold temperature of the permanent magnet is exceeded and / or undershot,

[0056] • adjusting at least one operating parameter of the rotating electrical machine when the threshold temperature of the permanent magnet is exceeded and / or undershot.

[0057] An efficient, reliable operation of the rotating electrical machine is thus achieved. BRIEF DESCRIPTION OF DRAWINGS

[0058] Figure 1 A cross-sectional view of a rotor arrangement comprising a rotor lamination core arrangement is shown;

[0059] Figure 2 A cross-sectional view of a rotating electrical machine is shown;

[0060] Figure 3a A cross-sectional view of a permanent magnet with a first functional layer and a second functional layer is shown;

[0061] Figure 3b A cross-sectional view of a permanent magnet with a particle layer comprising functional particles and a binding material is shown;

[0062] Figure 3c A cross-sectional view of a permanent magnet comprising a functional layer comprising a first sublayer and a second sublayer is shown;

[0063] Figure 4 A cross-sectional view of a permanent magnet comprising a protective layer applied on a side of a functional layer facing away from the permanent magnet is shown;

[0064] Figure 5An exemplary B-H characteristic of a functional layer is shown;

[0065] Figure 6 is a simplified diagram of the course of the magnetic field of a permanent magnet in a section of a rotor lamination core arrangement; and

[0066] Figure 7 is a flow chart of a method for controlling a rotating electric machine. DETAILED DESCRIPTION

[0067] Figure 1 An exemplary schematic cross-sectional view of a section of a rotor arrangement 111 comprising a rotor lamination core arrangement 100 is shown. The rotor lamination core arrangement 100 comprises a rotor lamination core 101 and in this embodiment a plurality of permanent magnets 102 arranged in the rotor lamination core 102. So-called buried permanent magnets 102 are involved. The rotor lamination core arrangement 100 is arranged on a drive shaft 103. On the surface of the permanent magnets 102 facing the drive shaft and on the surface of the permanent magnets 102 facing away from the drive shaft, respectively, a functional layer 105 for detecting an exceeding and / or a falling below of a threshold temperature of the permanent magnets 102 is arranged, wherein the functional layers 105 change their magnetic properties upon exceeding and falling below the threshold temperature, so that an exceeding and / or a falling below of the threshold temperature of the permanent magnets 102 can be detected. The Curie temperature of the functional layers 105 corresponds in particular to the threshold temperature. The permanent magnets can be configured for example cuboidally as rectangular magnets, wherein at least one surface is equipped with a functional layer 105. The permanent magnets 102 are in this embodiment seated in pockets 104, which are held in cutouts of the rotor lamination core 101. The permanent magnets 102 are there moved in, clamped. In addition, the permanent magnets can also be additionally or complementarily bonded with the rotor lamination core 101 with an adhesive, for example an epoxy resin, so that the pockets 104 between the rotor lamination core 101 and the permanent magnets 102 or between the rotor lamination core 101 and the functional layers 105 are at least partially filled with the epoxy resin. The permanent magnets can alternatively or complementarily also be arranged on the rotor lamination core 101 or in recesses at least partially in the rotor lamination core 101.

[0068] Figure 2 An exemplary schematic cross-sectional view of a section of a rotor arrangement 111 comprising a rotor lamination core arrangement 100 is shown. The rotor lamination core arrangement 100 comprises a rotor lamination core 101 and in this embodiment a plurality of permanent magnets 102 arranged in the rotor lamination core 102. So-called buried permanent magnets 102 are involved. The rotor lamination core arrangement 100 is arranged on a drive shaft 103. On the surface of the permanent magnets 102 facing the drive shaft and on the surface of the permanent magnets 102 facing away from the drive shaft, respectively, a functional layer 105 for detecting an exceeding and / or a falling below of a threshold temperature of the permanent magnets 102 is arranged, wherein the functional layers 105 change their magnetic properties upon exceeding and falling below the threshold temperature, so that an exceeding and / or a falling below of the threshold temperature of the permanent magnets 102 can be detected. The Curie temperature of the functional layers 105 corresponds in particular to the threshold temperature. The permanent magnets can be configured for example cuboidally as rectangular magnets, wherein at least one surface is equipped with a functional layer 105. The permanent magnets 102 are in this embodiment seated in pockets 104, which are held in cutouts of the rotor lamination core 101. The permanent magnets 102 are there moved in, clamped. In addition, the permanent magnets can also be additionally or complementarily bonded with the rotor lamination core 101 with an adhesive, for example an epoxy resin, so that the pockets 104 between the rotor lamination core 101 and the permanent magnets 102 or between the rotor lamination core 101 and the functional layers 105 are at least partially filled with the epoxy resin. The permanent magnets can alternatively or complementarily also be arranged on the rotor lamination core 101 or in recesses at least partially in the rotor lamination core 101.

[0069] The magnetic field of the permanent magnets 102, the direction 107 of which is indicated by the arrow in Figure 2The magnetic field of the permanent magnet 102 is introduced into the gap 112 by the rotor lamination core 101 and further guided into the stator lamination core 301 or interacts with the electromagnetic field generated by the tooth-shaped winding 302 of the stator across the gap 112. It is advantageous for the guidance of the magnetic field of the permanent magnet 102 in the direction of the gap to produce as little magnetic resistance as possible, that is to say, in general, but in particular for the functional layer 105, to use a material with high magnetization M or polarization J, high magnetic permeability and high electrical resistance (in order to reduce dynamic losses). The magnets are typically equipped with a passivation layer (Zn layer, phosphate layer, a few micrometers thick) and / or an oxidation protection layer (Cu-Ni, single layer or multilayer, < 10 micrometers) (not shown in Figure 2 ). As a material for the stator lamination core, a ferrosilicon material that is very well magnetically conductive is typically used as an electrical sheet, and an unavoidable minimum gap (air gap, or epoxy) is produced by fitting the permanent magnet 102 into the pocket 104 in the rotor lamination core 101.

[0070] The functional layer 105 is applied to the surface of the permanent magnet 102 as shown in Figure 3a . When the functional layer 105 itself acts as the oxidation protection structure 106, it is sufficient to apply only the functional layer 105. A combination with the oxidation protection layer 106 is possible and is shown schematically in Figure 4 . Here it is possible to either apply the oxidation protection layer (not shown) first or the functional layer (see Figure 4 ) first, depending on which is more advantageous from the process-technological point of view.

[0071] The functional layer 105 consists of a material that is in the ferromagnetic state at the desired operating temperature of the rotating electrical machine and has a Curie temperature T c corresponding to the desired threshold temperature. In order for the material to conduct the magnetic flux of the permanent magnet 102 as well as possible (that is to say, the magnetic resistance in the magnetic circuit is reduced), it is also advantageous for the material of the functional layer to have a high magnetization M, polarization J and high magnetic permeability .

[0072] In Figure 1 , 2 , 3a and 4, the functional layer 105 is applied only on the upper side and the lower side of the permanent magnet 102. A first functional layer 1051 is arranged on a first surface 1071 of the permanent magnet 102 and a second functional layer 1052 is arranged on a second surface 1072. The first surface 1071 and the second surface are here surfaces of the permanent magnet that are opposite one another. As shown by Figure 2It can be seen that this is the surface which is important for the magnetic flux in the direction of the gap 112 between the rotor lamination core arrangement 100 and the stator 301. The direction also corresponds to the preferred direction 107 of the magnetic properties of the anisotropic permanent magnet 102 typically used. When the surface is completely coated, it can be possible that a part of the magnetic flux coming in the direction of the air gap 112 flows back onto the layer and thus reduces the available magnetic field. The coating of only the upper and lower sides 1071, 1072 prevents this and can also be implemented much more simply and much more cost-effectively for technical reasons.

[0073] In Figure 3b an embodiment, an example of a functional layer 105 is shown in cross section, when the functional layer 105 is configured as a particle layer, which comprises functional particles 109 embedded in a binding material 110. In one implementation, such a particle layer comprising the functional particles 109 and the binding material 110 or other functional layer 105 is alternatively or additionally arranged on the lower side, that is to say on the surface of the permanent magnet 102 which is opposite the functional layer 105 shown. Figure 3b

[0074] Figure 3c An example of a functional layer 105 is shown in cross section, wherein the functional layer 105 comprises a plurality of sub-layers 10511, 10512 (multilayer system). The first sub-layer (10511) has a first Curie temperature and the second sub-layer 10512 has a second Curie temperature. The first Curie temperature and the second Curie temperature are in particular different from one another. A plurality of also different threshold temperatures of the permanent magnet can thus be detected, wherein the first and second Curie temperatures correspond to different threshold temperatures. It can thus be determined in particular in which temperature interval the temperature of the permanent magnet 102 lies and thus, if necessary, measures for adjusting the operating mode (for example, energy-saving mode) are more precisely coordinated to the current temperature. Measures can thus be introduced, for example, at an early stage, in order to avoid further temperature increases and by means of further threshold temperatures it can be determined whether measures have already been taken, that is to say whether the temperature is falling or remaining, or whether the temperature continues to rise and thus more forceful measures must be introduced by adjusting the operating parameters.

[0075] In Figure 5 an exemplary and schematic illustration of magnetization characteristic lines (magnetic induction 200 with respect to an external magnetic field 201) for ferromagnetic material 202, paramagnetic material 203 and vacuum 204 is shown. The ferromagnetic material has a magnetic permeability f which is typically greater than the magnetic permeability p ​The high multiple of the order of magnitude. The paramagnetic material thus exhibits a magnetic resistance in the magnetic circuit similar to the air gap. Correspondingly, the magnetic circuit is significantly influenced by the transition of the functional layer 105 from the ferromagnetic state with good magnetic conductivity to the paramagnetic state with poor magnetic conductivity. This jump in the magnetic flux can be reliably detected in the machine data during operation. The layer thickness of the functional layer should not be chosen to be so thick that it would shield the magnetic field of the permanent magnet 102 too much in normal operation (temperature < Tc of the functional layer) and thus negatively influence the functioning of the rotating electrical machine. The layer thickness preferably varies in the range < 50 m, advantageously also in the range < 20 m.

[0076] Figure 6 The brief course of the magnetic field lines 205 of the permanent magnet 102 in the rotor lamination core arrangement 100 is shown. The magnetic field lines extend from the permanent magnet 102 through the functional layer 105 and the gap (pocket) 104 between the functional layer and the rotor lamination core 101 and through the rotor lamination core.

[0077] Figure 7 A flow chart of a method 404 for controlling a rotating electrical machine 300 is shown. The control unit 400, for example a motor control device, receives an input signal 4010 from the rotating electrical machine 300 by means of a receiving unit 401. The input signal 4010 represents a magnetic quantity by means of which it can be detected whether a threshold temperature of the permanent magnet 102 is exceeded and / or undershot. The input signal 4010 can be a sensor signal which represents a magnetic quantity, for example the magnetic flux of the permanent magnet. The sensor can for example be a magnetometer, a Hall sensor, etc. The input signal 4010 is conducted by the receiving unit 401 to a comparison unit 402, where it is compared to a reference curve 4020. Depending on whether a threshold temperature of the permanent magnet 102 is detected to be exceeded and / or undershot, a control signal 4021 for setting at least one operating parameter of the rotating electrical machine 300 is provided by the comparison unit 402.

[0078] It is shown in the comparison that the functional layer 105 is in the ferromagnetic state and the rotating electrical machine 300 is operated in normal operation, so that no operating parameter is adjusted by means of the control signal 4021.

[0079] It is shown in the comparison that the functional layer 105 is in the ferromagnetic state and the rotating electrical machine 300 is operated in a special operating mode (for example in an energy-saving mode or switched off), so that the rotating electrical machine 300 can be brought again into normal operation by means of the control signal 4021, since from the ferromagnetic state of the functional layer 105 it can be concluded that the permanent magnet 102 has a temperature below the Curie temperature of the functional layer 105 and thus below the threshold temperature of the permanent magnet 102 and is not at risk of overheating. Normal operation is thus possible.

[0080] In the comparison it is shown that the functional layer 105 is in the paramagnetic state and the rotating electric machine 300 is in normal operation, so that the rotating electric machine 300 can be brought into a special operation (e.g. energy saving mode, matching operating parameters or switching off the rotating electric machine 300) by means of the control signal 4021.

[0081] In the comparison it is shown that the functional layer 105 is in the paramagnetic state and the rotating electric machine 300 is in a special operation (e.g. energy saving mode), so that further measures for cooling can be introduced by means of the control signal 4021, e.g. switching off the rotating electric machine 300 or further adjusting the operating parameters. The rotational speed of the rotor arrangement, the torque of the rotor arrangement or the coil current flowing through the copper winding of the rotating electric machine and contributing to the rotation of the rotor arrangement, e.g. serve as operating parameters of the rotating electric machine. The coil current, for example, can be reduced and thus the Joule heat which also causes the permanent magnets to heat up is reduced.

[0082] The output unit 403 outputs the control signal 4021 for setting at least one operating parameter of the rotating electric machine 300 depending on the detected exceeding and / or undershooting of the threshold temperature of the permanent magnets 102 to the rotating electric machine 300.

Claims

1. Rotor lamination core arrangement (100) comprising a rotor lamination core (101) and at least one permanent magnet (102), the permanent magnet being arranged at or in the rotor lamination core (101), characterized in that the permanent magnet (102) having a functional layer (105, 1051, 1052) for detecting an exceeding and a falling below a threshold temperature of the permanent magnet (102), wherein the functional layer (105, 1051, 1052) changes its magnetic properties upon exceeding and falling below the threshold temperature, thus enabling a detection of an exceeding and a falling below the threshold temperature of the permanent magnet (102), wherein the threshold temperature is a temperature below the Curie temperature of the permanent magnet (102) at which no irreversible change of the magnetic properties of the permanent magnet (102) has occurred yet.

2. The rotor lamination core arrangement (100) according to claim 1, characterized in that the Curie temperature of the functional layer (105, 1051, 1052) corresponds to the threshold temperature.

3. The rotor lamination core arrangement (100) according to claim 1 or 2, characterized in that the permanent magnet (102) comprises a protective layer (106), wherein the protective layer (106) is applied between the permanent magnet (102) and the functional layer (105, 1051, 1052) or on a side of the functional layer (105, 1051, 1052) facing away from the permanent magnet (102).

4. The rotor lamination core arrangement (100) according to claim 1 or 2, characterized in that the rotor lamination core (101) comprises a first and a second functional layer (105, 1051, 1052), wherein the first functional layer (1051) is arranged on a first surface (1071) of the permanent magnet (102) and wherein the second functional layer (1051) is arranged on a second surface (1072) of the permanent magnet (102) facing away from the first surface (1071).

5. The rotor lamination core arrangement (100) according to claim 1 or 2, characterized in that the functional layer (105, 1051, 1052) is configured as a granular layer, the granular layer comprising functional granules (109) and a binding material (110), wherein the functional granules (109) are at least partially surrounded by the binding material.

6. The rotor lamination core arrangement (100) according to claim 1 or 2, characterized in that the permanent magnet (102) is composed of a ferrouranium alloy and the Curie temperature of the functional layer has a value of 250°C or less.

7. The rotor lamination core arrangement (100) according to claim 1 or 2, characterized in that the permanent magnet (102) is composed of a samarium cobalt alloy and the Curie temperature of the functional layer has a value of 500°C or less.

8. The rotor lamination core arrangement (100) according to claim 1 or 2, characterized in that the functional layer (105, 1051, 1052) comprises a first sub-layer (10511) having a first Curie temperature and a second sub-layer (10512) having a second Curie temperature, and wherein the first Curie temperature and the second Curie temperature are different from each other.

9. The rotor lamination core arrangement (100) according to claim 1 or 2, characterized in that the permanent magnet (102) with the functional layer (105, 1051, 1052) is arranged in a pocket in the rotor lamination core (101).

10. The rotor lamination core arrangement (100) according to claim 6, characterized in that the permanent magnet (102) is composed of a ferrouranium alloy and the Curie temperature of the functional layer has a value between 100°C and 200°C.

11. The rotor lamination core arrangement (100) according to claim 7, characterized in that the permanent magnet (102) is composed of a samarium cobalt alloy and the Curie temperature of the functional layer has a value between 250°C and 350°C.

12. Rotor arrangement (108) comprising a rotor lamination core arrangement (100) according to any one of claims 1 to 11.

13. Rotating electric machine (300) comprising a rotor arrangement (108) according to claim 12.

14. Method (404) for controlling a rotating electrical machine (300) according to claim 13, comprising the steps of: • determining an exceeding and / or undershooting of a threshold temperature of the permanent magnet (102), • adjusting at least one operating parameter of the rotating electrical machine (300) upon exceeding and / or undershooting of the threshold temperature of the permanent magnet (102).

15. Control unit (400) for controlling a rotating electrical machine (300) according to claim 13, comprising: • a receiving unit (401) configured to receive an input signal (4010), wherein the input signal (4010) is representative of a magnetic quantity by means of which an exceeding and / or undershooting of a threshold temperature of the permanent magnet (102) can be detected, • a comparison unit (402) which compares the input signal (4010) with a reference curve (4020) and provides a control signal (4021) for setting at least one operating parameter of the rotating electrical machine (300) depending on the detected exceeding and / or undershooting of the threshold temperature of the permanent magnet (102), and • an output unit (403) for outputting the control signal (4021) for setting at least one operating parameter of the rotating electrical machine (300) depending on the detected exceeding and / or undershooting of the threshold temperature of the permanent magnet (102).

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