Method for determining a rotational blockage of a rotatable functional component, household appliance with a rotatable functional component

Abstract

The invention relates to a method for determining a rotational blockage of a functional component (2) rotatable in the intended operation of a household appliance (1), which is driven by means of a rotor (17) of an electric machine (4), wherein the electric machine (4) is supplied with an alternating voltage, which is provided by means of an inverter (6) connected to a DC intermediate circuit (7), which provides the alternating voltage depending on a control signal of a control unit (8), which provides the control signal at least depending on a rotational speed to be achieved by the rotor, wherein the DC intermediate circuit is supplied with electrical energy without feedback from an electrical energy source (12), and wherein an intermediate circuit DC voltage is detected.The rotational speed to be achieved is reduced for a predetermined period (48) in order to effect a transition from motor operation to generator operation in the event of undisturbed rotation of the rotor which is rotationally connected to the functional component, wherein at least one value of the DC link voltage recorded during the predetermined period is compared with a predetermined voltage reference value (49).

Description

[0001] The invention relates to a method for determining a rotational blockage of a functional component of the household appliance that is rotatable during normal operation of the household appliance, wherein the functional component is driven in rotation at least temporarily by a rotor of a rotating electrical machine of the household appliance, for which purpose the electrical machine is supplied with a multi-phase electrical alternating voltage that is provided by an inverter of the household appliance connected to a DC voltage intermediate circuit, wherein the inverter provides the multi-phase electrical alternating voltage depending on a control signal from a control unit of the household appliance, wherein the control unit provides the control signal at least depending on a speed to be reached by the rotor in order to adjust the alternating voltage according to the speed to be reached,wherein the DC intermediate circuit is supplied with electrical energy from an electrical energy source without feedback, wherein an intermediate DC voltage of the DC intermediate circuit is detected. Furthermore, the invention relates to a control unit for a household appliance, which has a functional component that can be rotated during normal operation of the household appliance, a rotating electrical machine that has a stator and a rotor that can be driven rotatably relative to the stator, wherein the rotor is mechanically coupled to the functional component for at least temporarily driving the functional component in rotation, a DC intermediate circuit that can be electrically coupled to an electrical energy source without feedback, an inverter connected to the DC intermediate circuit for supplying the electrical machine with a multi-phase electrical AC voltage, wherein the inverter is designedproviding the multi-phase alternating voltage depending on a control signal from the control unit, wherein the control unit is configured to provide the control signal at least depending on a speed to be achieved by the rotor, in order to adjust the alternating voltage according to the speed to be achieved, and to receive a sensor signal from a voltage sensor of the household appliance, which detects the intermediate DC voltage of the intermediate DC voltage. Finally, the invention relates to a household appliance with a functional component that is rotatable during normal operation of the household appliance, a rotating electrical machine that has a stator and a rotor that can be driven rotatably relative to the stator, wherein the rotor is mechanically coupled to the functional component for at least temporarily rotating the functional component.a DC intermediate circuit that can be electrically coupled to an electrical energy source without feedback, an inverter connected to the DC intermediate circuit for supplying the electrical machine with a multi-phase AC electrical voltage, wherein the inverter is designed to provide the multi-phase AC electrical voltage depending on a control signal from a control unit of the household appliance, wherein the control unit is designed to provide the control signal at least depending on a speed to be reached by the rotor in order to adjust the AC voltage according to the speed to be reached, wherein the household appliance is designed to detect an intermediate DC voltage of the DC intermediate circuit.

[0002] Generic household appliances and methods for their operation are fundamentally well known in the prior art, so that no separate written proof is required in this regard. Household appliances can, for example, be used to prepare food and can have ovens, microwaves, or the like, but can also be dishwashers, washing machines, tumble dryers, or the like. The rotatable functional component can, for example, be a fan, a turntable, a laundry drum, and / or the like. During normal operation of the household appliance, in particular during normal use, the functional component is at least partially driven in rotation, at least temporarily, by means of a rotor of a rotating electrical machine of the household appliance.

[0003] Rotating electrical machines are now frequently designed as multi-phase, particularly three-phase, rotating electrical machines. For this purpose, the household appliance typically includes an inverter connected to a DC link, which is electrically coupled to the electrical machine and supplies the electrical machine with a corresponding multi-phase AC voltage, thereby achieving the desired drive functionality for the rotor mechanically connected to the rotatable functional component. The inverter provides the multi-phase AC voltage in response to a control signal from a control unit of the household appliance, which is frequently designed as an electronic control unit and supplies a corresponding electrical control signal as a control signal, with which the AC voltage supply by the inverter can be adjusted.As a rule, the alternating voltage provided by the inverter is adjusted to a speed to be achieved by the rotor of the electrical machine.

[0004] In household appliances such as washing machines, washer / dryers, and the like, it is often important to ensure that a machine winding of the electrical machine, for example a stator winding and / or a rotor winding, does not heat up to an unacceptable level. In the prior art, it is common practice to use a machine temperature model for this purpose, which, among other things, monitors the current integral of a machine current in the machine winding. Particularly in the case of household appliances with tumble dryer functionality, it should also be considered that sufficient cooling functionality can generally only be achieved if a corresponding fan of the household appliance or a fan can also operate as intended. The aforementioned machine temperature model generally assumes this functionality as a parameter.In order to meet safety requirements, it is therefore generally necessary to ensure a minimum speed of the rotor.

[0005] In practice, however, implementing this requirement proves to be comparatively complex and costly. For a variety of reasons, the functional component and / or the electrical machine, particularly its rotor, may be blocked or severely braked. While protective measures are generally in place to prevent major damage outside the household appliance and to objects being treated, these measures generally cannot prevent damage to the functional component and / or the electrical machine, particularly its winding, from occurring. This generally requires costly repair or replacement of the household appliance.

[0006] The invention is based on the object of being able to detect the blocking or strong braking of the functional component and / or the rotor better and more reliably with little effort.

[0007] As a solution, the invention proposes a method, a control unit and a household appliance according to the independent claims.

[0008] Advantageous further training results from features of the dependent claims.

[0009] With regard to a generic method, the invention proposes in particular that the speed to be achieved is reduced for a predetermined period of time in order to effect a transition from motor operation of the electrical machine to generator operation of the electrical machine with undisturbed rotation of the rotor rotationally connected to the functional component, at least one value of the intermediate circuit DC voltage detected during the predetermined period of time is compared with a predetermined voltage comparison value in order to determine the rotational blockage of the functional component.

[0010] With regard to a generic control unit, the invention proposes in particular that the control unit is designed to reduce the speed to be achieved for a predetermined period of time in order to bring about a transition from motor operation of the electrical machine to generator operation of the electrical machine in the case of undisturbed rotation of the rotor rotationally connected to the functional component, to compare at least one value of the intermediate circuit DC voltage detected during the predetermined period of time with a predetermined voltage comparison value in order to determine a rotational blockage of the functional component.

[0011] With regard to a generic household appliance, the invention proposes in particular that the control unit is designed according to the invention.

[0012] The invention is based, among other things, on the idea that, given undisturbed rotation of the rotor connected to the functional component, control with a suitable speed reduction within a predetermined period of time implements generator operation during the predetermined period of time, at least temporarily, so that electrical energy can be supplied to the DC link due to the existing rotational pulse of the rotor connected to the functional component during generator operation. In generator mode, electrical energy can be generated by the electric machine and transferred to the intermediate circuit via the inverter. Because the intermediate circuit is connected to the electrical energy source without feedback, the energy supplied to the DC link during generator operation can only remain in the DC link.Typically, the DC link has an electrical capacitance that is charged with this energy. This leads to a significant voltage increase, which can be detected by comparing it with the specified or presettable voltage comparison value. This means that, during proper or undisturbed operation of the rotor connected to the functional component, a corresponding voltage increase due to generator operation can be detected at least temporarily during the specified period. If such a voltage increase is not detected, this indicates a blockage or severe braking of the rotor connected to the functional component.If generator operation cannot be detected due to a blockage or strong braking of the rotor or the functional component, a corresponding voltage increase in the intermediate circuit DC voltage cannot be detected either, because generator operation - as explained above - does not exist.

[0013] To implement this functionality, no additional components are required. Instead, the existing design can be used. Only the control unit needs to be adapted accordingly so that it can implement the desired functionality according to the invention. Therefore, the invention can be implemented with very little effort, and in particular, it can also be retrofitted to existing household appliances.

[0014] To ensure that the DC intermediate circuit is coupled to the electrical energy source without feedback, it can be provided that a corresponding decoupling unit is provided, for example using one or more diodes, the uncontrolled bridge rectifier and / or the like. This ensures that no electrical energy can reach the electrical energy source from the DC intermediate circuit. Therefore, only a unidirectional energy flow from the electrical energy source to the household appliance, in particular to the DC intermediate circuit, is possible. In this context, it can be provided that the electrical energy source is formed by a public energy supply network that provides a single-phase or multi-phase electrical alternating voltage.Preferably, a rectifier unit can be provided for coupling the electrical energy source, which rectifier unit is preferably included in the household appliance and which can be coupled to the electrical energy source on the AC side. On the DC side, the rectifier unit is preferably directly connected to the DC intermediate circuit. The rectifier unit can have a bridge rectifier formed from diodes or the like. In principle, however, the energy source can also be a DC energy source that can be electrically coupled to the DC intermediate circuit. In this case, the unidirectional coupling is achieved, for example, by a single diode that releases energy flow only from the energy source to the DC intermediate circuit. Of course, the diodes can also be formed by thyristors or the like, which are operated in a correspondingly controlled manner.The use of transistors in addition to diodes or as an alternative to diodes can also be provided if the transistors are operated in a controlled manner.

[0015] Preferably, the specified voltage comparison value is greater than a value of the intermediate circuit DC voltage that can be achieved by the electrical energy source outside of the rotating drive of the functional component by the electric machine. If no other components are connected to the DC intermediate circuit, the DC intermediate circuit voltage in this case corresponds to the maximum DC voltage that can be provided by the energy source at the DC intermediate circuit. The voltage comparison value can be selected slightly higher, for example, taking tolerances or the like into account, so that generator operation can be reliably detected in undisturbed operating conditions.If the rotation of the rotor connected to the functional component is hindered, disrupted, or severely decelerated, generator operation cannot be sufficiently achieved within the specified time period, meaning that the intermediate circuit DC voltage cannot rise above the specified voltage comparison value. Therefore, it can be stated that, based on a simple comparison with the voltage comparison value determined in this way, the undisturbed operation of the electrical machine driving the functional component can be reliably and quickly improved without great effort.

[0016] According to a further development, it is proposed that the predetermined period be at least 0.1 s, preferably at least 0.5 s, particularly preferably at least 3 s. By selecting the predetermined period as proposed, it is possible to reliably detect blocking using simple means, preferably using the means already available.

[0017] According to a further development, it is proposed that the predetermined period be no more than 5 s, preferably no more than 3 s, particularly preferably no more than 0.8 s. This makes it possible to minimize the effects of the method according to the invention on the intended operation of the household appliance. It is thus possible for the method according to the invention to have essentially no noticeable effect on the intended operation for a user of the household appliance.

[0018] Furthermore, it is proposed that the method according to the invention be carried out repeatedly. This ensures that even a blockage that may occur during the intended operation of the household appliance can be reliably detected. It can be provided that the method according to the invention is carried out when the household appliance is started and / or ended. However, it can also be provided that the method according to the invention is repeated due to a predeterminable event, for example, the addition of an item of laundry during a wash cycle, or after the expiration of a predefined period of time, for example, five minutes, ten minutes, or the like.

[0019] According to a further development, it is proposed that the control unit provides the control signal depending on a sensorless field-oriented control. Sensorless field-oriented control is particularly suitable for use with multi-phase AC machines and makes it possible to keep the control effort for such electrical machines low. At the same time, reliable operation can be achieved without the need for a sensor to determine the rotor's rotational position. At the same time, field-oriented control makes it easy to implement suitable generator operation within the specified time period, so that the invention can be integrated into an existing design or application with little effort.

[0020] Furthermore, it is proposed that a rotor-related d / q system be determined from a stator-related multiphase system using a Clarke transformation and a subsequent Park transformation. This allows the method according to the invention to be implemented in the control unit in a particularly simple manner.

[0021] Furthermore, it is proposed that the sensorless field-oriented control be used to specify generator operation of the electric machine for the specified period of time. It is therefore not necessary to provide generator operation for the specified period of time using separate means and to provide a corresponding separate unit in the control unit. Rather, it is possible to utilize the existing sensorless field-oriented control and, by means of this, to specify generator operation based on the speed reduction, so that the control unit can easily provide the appropriate control signal for the inverter without additional means. The invention can thus be further improved.

[0022] According to a further development, it is proposed that an AC voltage component superimposed on the intermediate circuit DC voltage is determined and that the AC voltage component is compared with a predetermined AC voltage reference value. This further development makes it possible to further improve the reliability of blocking detection. It utilizes the knowledge that, in the event of blocking or severe braking of the rotor connected to the functional component, a significant AC voltage can be superimposed on the intermediate circuit DC voltage due to the operation of the inverter. The frequency of the AC voltage depends in particular on the operation of the inverter. The amplitude of the superimposed AC voltage also depends, among other things, on the inductances of the electrical machine.This alternating voltage is typically significantly higher than a pulsating direct voltage, which is generated by rectifying the alternating voltage of the electrical power source during normal, undisturbed operation. Therefore, it can be used to support the reliability of the detection functionality.

[0023] Preferably, the AC voltage reference value is selected to be greater than the AC voltage component during fault-free, normal operation. This allows for a clear distinction between faulty and undisturbed operation to be easily determined.

[0024] It is further proposed that the electric machine be configured to be supplied with a three-phase alternating voltage, and that the inverter be configured to provide a three-phase alternating voltage. This configuration allows for an application with particularly cost-effective components, since the use of three-phase machines is very widespread.

[0025] It is further proposed that the household appliance be designed to be electrically coupled to a power source that provides a single-phase AC power source voltage. This makes it possible to use the household appliance in a wide variety of households where a corresponding single-phase AC voltage is available.

[0026] With regard to the household appliance, it is further proposed that the household appliance have an uncontrolled bridge rectifier which is electrically coupled on the DC voltage side to the DC voltage intermediate circuit and which can be electrically coupled on the AC voltage side to an electrical energy source providing an AC energy source. This makes it easy to achieve a feedback-free electrical coupling or a unidirectional energy-technical coupling of the energy source to the DC voltage intermediate circuit. The bridge rectifier can be designed to match the number of phases of the AC voltage provided by the energy source. Preferably, the electrical energy source is an energy source that provides a single-phase AC electrical voltage, and the bridge rectifier can be designed in the manner of a single-phase bridge rectifier circuit.

[0027] It is further proposed that the electrical machine be a synchronous machine or an asynchronous machine. These machine types have proven particularly suitable for use in a given household appliance.

[0028] It is further proposed that the inverter be designed to provide a three-phase alternating voltage. This allows the use of three-phase electrical machines, for example, synchronous machines, asynchronous machines, or the like, which can serve as a drive for the functional component.

[0029] Advantageous embodiments of the method according to the invention are to be regarded as advantageous embodiments of the control unit and the household appliance. For example, physical components of the control unit or the household appliance are designed alone or in combination to enable the method steps.

[0030] Further features of the invention emerge from the claims, the figures, and the description of the figures. All features and combinations of features mentioned above in the description, as well as the features and combinations of features mentioned below in the description of the figures and / or shown alone in the figures, can be used not only in the respective combination specified, but also in other combinations or on their own, without departing from the scope of the invention. Thus, embodiments are also to be considered encompassed and disclosed by the invention that are not explicitly shown and explained in the figures, but which emerge and can be produced through separate combinations of features from the explained embodiments.

[0031] Embodiments of the invention are explained in more detail below with reference to schematic drawings. In the figures, like reference numerals denote like functions and features.

[0032] They show: Fig. 1 a washing machine as a household appliance according to the invention in a schematic open front view, Fig. 2 a schematic diagram for a drive unit for the washing machine according to Fig. 1, Fig. 3 in a schematic block diagram view a section of a control functionality of a control unit of the household appliance for the washing machine according to Fig. 1, Fig. 4 a schematic diagram of signal curves in an undisturbed rotor of an electrical machine of the drive unit according to Fig. 2, and Fig. 5 a schematic diagram representation such as Fig. 4, where the runner is blocked.

[0033] Fig. 1 shows a washing machine 1 as a household appliance in a schematic open front view. Fig. The washing machine 1 shown in Figure 1 comprises a rotatably mounted washing machine drum 2 as a functional component, which is driven via a drive belt 3 by means of a three-phase permanent magnet synchronous machine 4. The synchronous machine 4 is connected via an electrical line 5 to an inverter 6, which in turn is connected to a DC link 7 ( Fig. 2). The DC intermediate circuit 7 has a bridge rectifier 9 formed from diodes, which is connected on the DC side to an intermediate circuit capacitor 10. On the AC side, the bridge rectifier 9 is connected to terminals 11, which serve for the detachable electrical connection to a public power grid 12 as an electrical energy source. In this case, the power grid 12 provides a single-phase AC voltage of approximately 230 V at approximately 50 Hz.

[0034] The washing machine 1 has a control unit 8, which, among other things, can control the inverter 6 using control signals not shown in detail. Furthermore, the washing machine 1 has an operating unit 13, by means of which a user can control the function of the washing machine 1 via an input field. At the same time, the operating unit 13 has a graphical output unit, by means of which the operating states of the washing machine 1 can be visually displayed to the user. The washing machine 1 further has a power supply unit 14, by means of which the control unit 8 and components connected to it, for example the operating unit 13, can be supplied with electrical energy for proper operation.

[0035] The inverter 6 has three half-bridge circuits (not shown), each of which has a series connection of two IGBTs, whose respective center terminals are connected to respective phase terminals of the synchronous machine 4 via the electrical line 5. The IGBTs are electrically connected to a driver circuit 16 via their respective gate terminals. The driver circuit 16 receives appropriate control signals for the intended operation of the inverter 6, depending on a control signal from the control unit 8.

[0036] The synchronous machine 4 has a stator 18 ( Fig. 3), which has a stator winding connected to the inverter 6 via the electrical line 5, as previously explained. Furthermore, the synchronous machine 4 has a rotor 17, which is rotatably arranged in a through-opening of the stator 18 and, in the present embodiment, has permanent magnets to provide the permanently excited synchronous machine 4. The stator winding of the stator 18 is three-phase.

[0037] In addition to the intermediate circuit capacitor 10, the DC link 7 has a voltage sensor 15, by means of which an intermediate circuit DC voltage of the DC link 7 can be detected. The voltage sensor 15 supplies a voltage sensor signal to the control unit 8.

[0038] The bridge rectifier 9 ensures, on the one hand, that the alternating voltage provided by the power supply network 12 is rectified and that energy from the alternating voltage network 12 can be supplied to the DC intermediate circuit 7. On the other hand, it prevents the feedback of electrical energy from the DC intermediate circuit 7 to the power supply network 12. Therefore, energy flow is only possible unidirectionally in this case, thus achieving zero feedback.

[0039] The inverter 6 provides the three-phase alternating voltage for the synchronous machine 4 depending on the control signal from the control unit 8. The control unit 8 provides the control signal at least depending on the speed to be achieved by the rotor 17. The inverter 6 adjusts the alternating voltage accordingly according to the speed to be achieved.

[0040] The control unit is embodied here as an electronic control unit with a computing unit (not designated). The control unit 8 is designed to provide sensorless field-oriented control for the synchronous machine 4. Fig. 3 shows a schematic block diagram of a section of a control functionality of the control unit 8 with respect to the sensorless field-oriented control.

[0041] As from Fig. As can be seen in Figure 3, phase currents in the electrical line 5 are detected using current sensors (not shown), and corresponding sensor signals 19 are transmitted to a block 20. Block 20 performs a Clarke transformation and delivers corresponding transforms α, β as a result. The transforms α, β are fed to a block 21, which performs a Park transformation and delivers transforms p, q. From block 21, the transforms p, q are fed to a logic operation 22.

[0042] The control unit 8 provides a signal at 27 indicating the speed to be achieved or the target speed for the rotor 17. The signal is fed to a block 23, which executes a ramp function. This specifies the rate of change of the speed to be achieved. The speed change determined in this way is fed to a link 24. From the link 24, the signal is fed to a block 25, which implements speed control based on a PI controller. As a result, block 25 delivers a signal I q,soll and a corresponding bias signal preload to a block 26. In block 26, a signal I q, maxand a signal relating to load information. These signals are combined in block 26, and a resulting signal is fed to link 22. In link 22, this signal is combined with the Park transforms d, p, and the resulting signal is fed to block 28. Current control takes place in block 28, resulting in p, q signals that are subjected to an inverse Park transformation in block 29. In this way, signals α, β are generated, which are then fed to space vector modulation (SVM) in block 30. Block 30 then generates the control signals for the IGBTs of inverter 6 as a control signal.

[0043] The Park transforms d, q from block 21 are additionally fed to link 22. The signals from blocks 20 and 29 are also fed to block 31, which provides an observer for electromagnetic feedback. This observer provides a speed signal 33, which is fed to block 32. The ramp signal from block 23 is also fed to block 32, and block 32 provides a speed signal 34 as a result, which is fed to link 24.

[0044] The ramp signal from block 23 is further fed to an integrator block 33, which supplies a corresponding ramp signal 35 to a block 36. Block 36 also receives an angle signal 37 from block 31. Block 36 also receives the ramp signal from block 23, combines signals 35 and 37, and supplies an angle signal 38 to blocks 21 and 29 for performing the transformation and the inverse transformation, respectively. Furthermore, block 36 supplies the load information signal to block 26.

[0045] Fig. 4 now shows, in a schematic diagram representation, a diagram 38 with four signal diagrams 40, 41, 42, 43 with signal curves which use the same time axis t in a time-synchronized manner and which represent the signal curves when the rotor 17 of the synchronous machine 4 can reach the desired speed without interference during normal operation. Fig. Figure 4 shows the four signal curves 40, 41, 42, 43, which use a common time axis, namely the abscissa.

[0046] In signal diagram 40, a graph 44 represents the intermediate circuit voltage detected by the voltage sensor 15. In signal diagram 41, a graph 45 represents the alternating voltage of the alternating voltage network 12. In signal diagram 42, a graph 46 represents the torque-generating current according to the transformed I q In a signal diagram 43, a graph 47 shows the speed to be achieved according to the control signal for the inverter 6. In the present embodiment, it is provided that the control unit 8 uses a sensorless field-oriented control, as described in Fig. 3 previously explained. Speed ​​control is performed depending on a calculated rotor angle and a calculated speed. One manipulated variable of the speed controller is the rotor-related torque-generating transformed current I q . An acceleration or deceleration of the rotor 17 leads to a difference in the value of I q regarding the sign.

[0047] During normal operation, the intermediate circuit capacitor 10 is charged via the bridge rectifier 9 from the power supply network 12 to a voltage value of the intermediate circuit DC voltage, which is approximately the amplitude of the AC voltage provided by the power supply network 12. In this case, the value is approximately 325 V. This intermediate circuit DC voltage is also applied to the half-bridge circuits of the inverter 6 as a power supply source. The function of the inverter 6 and the operation of the IGBTs according to a pulse-width modulation method are known to those skilled in the art, which is why detailed explanations are omitted. Using the half-bridge circuits, appropriate phase currents are set for the three phases of the stator winding of the stator 18 of the synchronous machine 4.These are detected by means of current sensors (not shown) on the electrical line 5 and corresponding current signals are fed to the control unit 8 for further evaluation, as can be seen from the signal 19 in . Fig. 3. By processing the current signals thus provided by first performing a Clarke and then a Park transformation, the transformed current quantities I q and I d determined.

[0048] If the rotor 17 is accelerated in terms of its rotation due to the operation of the inverter 6, i.e., the synchronous machine 4 is operated in motor mode, the DC link 7, in particular its intermediate circuit capacitor 10, is discharged, whereas during braking, i.e., a reduction in the speed of the rotor 17, the DC link 7 and in particular its intermediate circuit capacitor 10 are charged in generator mode of the synchronous machine 4. Because a backflow of electrical energy from the DC link into the power supply network 12 is prevented by the bridge rectifier 9, a voltage increase in the intermediate circuit DC voltage results when the rotor 17 is braked. In motor mode, however, the drop in the intermediate circuit DC voltage is prevented by the subsequent supply of electrical energy from the power supply network 12 via the bridge rectifier 9.

[0049] Only when the rotor 17 of the synchronous machine 4 actually rotates during intended operation can the generator operation explained above be achieved. The behavior of the intermediate circuit DC voltage during generator operation of the synchronous machine 4 depends, among other things, on the amplitude of the impressed transformed current I q away.

[0050] For this method, it is irrelevant whether operation is planned in the basic range or in the field weakening range. This fact is used here to determine whether there is a blockage of the rotor 17 connected to the washing machine drum 2. For this purpose, the method according to the invention only needs to cause the sensorless field-oriented control of the control unit 8 to briefly, i.e., during a predetermined period 48 ( Fig. 4) the speed to be achieved of the rotor 17 according to the graph 47 in Fig. 4. During this period, the intermediate circuit voltage is reduced according to graph 44 in Fig. 4. If the rotor 17 is operating properly, the intermediate circuit voltage increases according to graph 44. Fig. 4 shows that the specified period begins at time t1 and ends at time t2. At time t1, the intermediate circuit DC voltage is approximately 325 volts, as shown in graph 44. By time t2, this intermediate circuit DC voltage rises to a value of approximately 337 volts.

[0051] Signal diagram 40 also shows a voltage comparison value 49, which in this case is approximately 330 volts. In this configuration, it is now evident that the specified voltage comparison value 49 is exceeded by graph 44 during period 48, so that it can be determined that synchronous machine 4 has reliably reached generator operation within the specified period 48. Therefore, it can be determined that rotor 17 and the washing machine drum 2, which is rotationally coupled to it, can rotate properly. No malfunction is present here.

[0052] The speed reduction can also be seen from graph 46, with which the transformed control signal I q is shown.

[0053] Fig. 5 shows in a further schematic diagram 39 the signal diagrams 40 to 43, as in the schematic diagram according to Fig. 4, but here the washing machine drum 2 is blocked. The blockage may be caused by mechanical tension or the like. The blockage of the washing machine drum 2 resulted in the rotor 17, which is rotationally coupled to the washing machine drum 2, also not rotating. This affects the measurement process described above.

[0054] It can be seen that the measurement process for the specified period 48 - as previously explained - does indeed lead to a reduction in the speed to be achieved according to graph 47, but this does not result in an excessive voltage increase of the intermediate circuit DC voltage according to graph 44. Since the rotor 17 is not rotating, generator operation cannot be achieved in this case. This means that due to the lack of generator operation during the specified period 48, no energy is supplied to the DC voltage intermediate circuit 7 and thus to the intermediate circuit capacitor 10. This explains why, according to graph 44 in Fig. 5, the specified voltage comparison value 49 is not reached. Therefore, at the latest at time t2, it can be determined that a fault exists with regard to the rotation of the rotor 17, i.e., a blockage of the rotor 17 and the washing machine drum 2 connected to the rotor 17 can be detected. The control unit 8 can then issue a corresponding message and, if necessary, adjust the further operation of the inverter 6.

[0055] Out of Fig. 5 it can also be seen that an alternating voltage is superimposed on the intermediate circuit DC voltage, which in this case has an amplitude of approximately 25 volts.

[0056] This effect is in normal, undisturbed operation according to Fig.4 is not present. It is therefore possible to verify the functionality described above by specifying an AC voltage comparison value for the AC voltage component of the intermediate circuit DC voltage. For this purpose, the AC voltage comparison value can be selected for an amplitude of approximately 10 to 15 volts. This can further improve the reliability of the detection.

[0057] Overall, the invention makes it possible to reliably and quickly detect the blocking or severe braking of a functional component connected to a rotor of an electrical machine without requiring significant additional hardware. At the same time, the invention also makes it possible to retrofit existing household appliances with the invention. This can be achieved, for example, by appropriately supplementing the control program of a control unit 8 implemented using a program-controlled computer unit. It is therefore even possible to implement the invention without any additional hardware effort.

[0058] The embodiments serve solely to explain the invention and are not intended to limit it. List of reference symbols 1 washing machine 2 washing machine drum 3 drive belts 4 Synchronous machine 5 Management 6 inverters 7 DC link 8 Control unit 9 bridge rectifiers 10 DC link capacitor 11 connection terminals 12 AC network 13 Control unit 14 Power supply unit 15 Voltage sensor 16 driver circuit 17 runners 18 stands 19 sensor signals 20 blocks 21 Block 22 Link 23 Block 24 Link 25 blocks 26 Blocks 27 Signal 28 blocks 29 Block 30 blocks 31 blocks 32 blocks 33 Integrator block 34 Speed ​​signal 35 Ramp signal 35 Signal 36 blocks 37 Signal 38 Diagram representation 39 Diagram representation 40 Signal diagram 41 Signal diagram 42 Signal diagram 43 Signal diagram 44 Graph 45 Graph 46 Graph 47 Graph 48 period 49 Voltage comparison value

Claims

[1] Method for determining a rotational blockage of a functional component (2) of the household appliance (1) that is rotatable during normal operation of the household appliance (1), wherein the functional component (2) is driven in rotation at least temporarily by means of a rotor (17) of a rotating electrical machine (4) of the household appliance (1), for which purpose the electrical machine (4) is supplied with a multi-phase alternating electrical voltage that is provided by an inverter (6) of the household appliance (1) connected to a DC voltage intermediate circuit (7), wherein the inverter (6) provides the multi-phase alternating electrical voltage depending on a control signal from a control unit (8) of the household appliance (1), wherein the control unit (8) provides the control signal at least depending on a speed to be reached by the rotor (17) in order to adjust the alternating voltage according to the speed to be reached,wherein the DC intermediate circuit (7) is supplied with electrical energy from an electrical energy source (12) without feedback, wherein an intermediate DC voltage of the DC intermediate circuit (7) is detected, , characterized by that the speed to be achieved is reduced for a predetermined period of time (48) in order to bring about a transition from motor operation of the electrical machine (4) to generator operation of the electrical machine (4) with an undisturbed rotation of the rotor (17) which is rotationally connected to the functional component (2), at least one value of the intermediate circuit DC voltage detected during the predetermined period of time (48) is compared with a predetermined voltage comparison value (49) in order to determine the rotational blockage of the functional component (2). [2] Method according to claim 1, characterized bythat the predetermined voltage comparison value (49) is greater than a value of the intermediate circuit DC voltage which is achieved by the electrical energy source (12) outside the rotating drive of the functional component (2) by the electrical machine (4). [3] Method according to one of the preceding claims, characterized by that the predetermined period (48) is at least 0.1 s, preferably at least 0.5 s, particularly preferably at least 3 s. [4] Method according to one of the preceding claims, characterized by that the predetermined period (48) is at most 5 s, preferably at most 3 s, particularly preferably at most 0.8 s. [5] Method according to one of the preceding claims, characterized by that the control unit (8) provides the control signal depending on a sensorless field-oriented control. [6] Method according to claim 5, characterized bythat a rotor-related d / q system is determined from a stator-related multi-phase system using a Clarke transformation and a subsequent Park transformation. [7] Method according to claim 5 or 6, characterized by that a generator operation of the electrical machine (4) is specified for the specified period (48) by means of the sensorless field-oriented control. [8] Method according to one of the preceding claims, characterized by that an alternating voltage component superimposed on the intermediate circuit direct voltage is determined and the alternating voltage component is compared with a predetermined alternating voltage comparison value. [9] Method according to claim 8, characterized by that the AC voltage comparison value is selected to be greater than the AC voltage component in trouble-free, intended operation. [10] Method according to one of the preceding claims, characterized bythat the electrical machine (4) is designed to be supplied with a three-phase alternating voltage, and the inverter (6) provides a three-phase alternating voltage. [11] Method according to one of the preceding claims, characterized by that the household appliance (1) is designed to be electrically coupled to an energy source (12) which provides a single-phase energy source alternating voltage. [12] Control unit (8) for a household appliance (1), which has a functional component (2) which is rotatable during normal operation of the household appliance (1), a rotating electrical machine (4) which has a stator (18) and a rotor (17) which is rotatably driven relative to the stator (18), wherein the rotor (17) is mechanically coupled to the functional component (2) for at least temporarily rotating the functional component (2), a DC voltage intermediate circuit (7) which can be electrically coupled to an electrical energy source (12) without feedback, an inverter (6) connected to the DC voltage intermediate circuit (7) for supplying the electrical machine (4) with a multi-phase electrical alternating voltage, wherein the inverter (6) is designed to provide the multi-phase electrical alternating voltage depending on a control signal from a control unit (8) of the household appliance (1), wherein the control unit (8) is designed,to provide the control signal at least as a function of a speed to be reached by the rotor (17) in order to adjust the alternating voltage according to the speed to be reached and to receive a sensor signal from a voltage sensor of the household appliance (1) which detects the intermediate circuit DC voltage of the DC voltage intermediate circuit (7), , characterized by in that the control unit (8) is designed to reduce the speed to be achieved for a predetermined period of time (48) in order to bring about a transition from motor operation of the electrical machine (4) to generator operation of the electrical machine (4) in the case of undisturbed rotation of the rotor (17) which is rotationally connected to the functional component (2), and to compare at least one value of the intermediate circuit DC voltage detected during the predetermined period of time (48) with a predetermined voltage comparison value (49) in order to determine a rotational blockage of the functional component (2). [13] Household appliance (1) with a functional component (2) which is rotatable during normal operation of the household appliance (1), a rotating electrical machine (4) which has a stator (18) and a rotor (17) which is rotatably driven relative to the stator (18), wherein the rotor (17) is mechanically coupled to the functional component (2) for at least temporarily rotating the functional component (2), a DC voltage intermediate circuit (7) which can be electrically coupled to an electrical energy source (12) without feedback, an inverter (6) connected to the DC voltage intermediate circuit (7) for supplying the electrical machine (4) with a multi-phase electrical alternating voltage, wherein the inverter (6) is designed to provide the multi-phase electrical alternating voltage depending on a control signal from the control unit (8), wherein the control unit (8) is designed,providing the control signal at least as a function of a speed to be reached by the rotor (17) in order to adjust the alternating voltage according to the speed to be reached, wherein the household appliance (1) is designed to detect an intermediate circuit DC voltage of the DC voltage intermediate circuit (7), , characterized by that the control unit (8) is designed according to claim 12. [14] Household appliance according to claim 13, characterized by an uncontrolled bridge rectifier (9) which is electrically coupled on the DC voltage side to the DC voltage intermediate circuit (7) and which can be electrically coupled on the AC voltage side to an electrical energy source (12) providing an energy source AC voltage. [15] Household appliance according to claim 13 or 14, characterized bythat the electrical machine (4) is formed by a synchronous machine or an asynchronous machine, wherein the inverter (6) is particularly designed to provide a three-phase alternating voltage.

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