Method for detecting and clearing a blockage of a centrifugal pump

Abstract

The invention relates to a method for detecting and clearing a blockage in a centrifugal pump (1) with an electric motor (5) controlled by a controller (7) for driving the centrifugal pump (1), comprising the steps of: checking whether the activity of the controller (7) falls below a threshold value and whether the motor current and / or torque of the electric motor (5) differs before and after the threshold is crossed, in order to detect the blockage, wherein the activity of the controller (7) is determined by a product of the high-pass filtered speed of the electric motor (5) and the high-pass filtered motor current and / or high-pass filtered torque of the electric motor (5) (100); and if so, performing a cleaning sequence to clear the blockage.

Description

Technical field

[0001] The invention relates to a method for detecting and clearing a blockage in a centrifugal pump with an electric motor controlled by a controller for driving the centrifugal pump, comprising the step of performing a cleaning sequence to clear the blockage. The invention further relates to a centrifugal pump with an electric motor for driving the centrifugal pump and a control and / or regulation device comprising a controller for regulating the electric motor, wherein the control and / or regulation device is configured to perform a cleaning sequence to clear the blockage. Background of the invention

[0002] Centrifugal pumps are used in various applications, particularly in wastewater systems and industrial conveying systems, to pump liquids. During operation, these pumps can become clogged by foreign objects, deposits, or solids. Especially in wastewater applications, textiles are frequently found in the pumped medium. These textiles can become lodged in various places within the pump, for example, wrapping around an impeller or getting caught in the pump's intake. Such clogging leads to increased power consumption, accelerated wear, and / or blockage of the pump. A blocked centrifugal pump often needs to be removed, cleaned, or even replaced.

[0003] To clear such a blockage, the centrifugal pump can be operated with a so-called cleaning sequence, in which the impeller is repeatedly rotated in forward and reverse directions to remove the foreign object causing the blockage. However, these measures are often time-consuming and costly and lead to undesirable downtime of the centrifugal pump. While a cleaning sequence that is too short risks not clearing the blockage at all or only partially, a cleaning sequence that is too long can leave the centrifugal pump unnecessarily unproductive for an extended period.

[0004] Therefore, there is a need for an improved method for detecting and subsequently clearing blockages in centrifugal pumps, one that more precisely identifies whether a blockage is present. A solution that allows for the cleaning sequence to be carried out as needed and ideally also enables an objective evaluation of the cleaning sequence's success would be particularly advantageous. Description of the invention

[0005] Starting from this situation, it is an object of the present invention to provide a method and a corresponding centrifugal pump that can detect an impending blockage and prevent it by suitable measures in order to improve the operating time of the centrifugal pump.

[0006] The object of the invention is achieved by the features of the independent claims. Advantageous embodiments are specified in the dependent claims.

[0007] Accordingly, the task is solved by a method for detecting and resolving a blockage in a centrifugal pump with an electric motor controlled by a controller to drive the centrifugal pump, comprising the following steps: Checking whether the controller activity falls below a threshold and whether the motor current and / or torque of the electric motor differs before and after the threshold is crossed, in order to detect the blockage, wherein the controller activity is determined by a product, in particular a multiplication, of the high-pass filtered speed of the electric motor and the high-pass filtered motor current and / or high-pass filtered torque of the electric motor; and if so, performing a cleaning sequence to clear the blockage.

[0008] In other words, it is proposed to use controller activity as a measure to detect an impending blockage. Controller activity describes, in particular, the frequency and magnitude of changes to a control variable, specifically the product of the high-pass filtered speed of the electric motor and the high-pass filtered motor current and / or torque of the electric motor. The proposed solution thus consists of a first step: detecting whether the controller activity falls below a certain threshold. If the controller activity is below the threshold, i.e., has a negative sign, a disturbance event is detected. This disturbance event could be an unwanted object in the pump housing that disrupts the normal operation of the centrifugal pump. In a second step, the control variable, for example, the torque of the electric motor, can then be compared before and after the disturbance event.If the two values ​​differ, it is highly likely that the interfering object is located in the pump housing and is negatively affecting the pump's operating behavior.

[0009] Ideally, at the steady-state operating point, the controller activity is always zero, meaning the controller does not need to change its manipulated variable, and a controlled variable, particularly the speed of the electric motor, also remains unchanged. However, if a setpoint is changed or a load changes, the controller must adjust its output to set the new setpoint or react to the changed load. A distinction can be made between a reference response (change in setpoint) and a disturbance response (change in load). In a preferred refinement, the threshold is zero or nearly zero. This means that even the smallest changes in controller activity can be considered potential indicators of a blockage, leading to particularly sensitive detection. By using controller activity as a criterion, the accuracy of blockage detection is increased.The controller is designed to be particularly computer-based, for example as part of a control and / or regulation system.

[0010] A centrifugal pump is generally defined as a turbomachine that utilizes rotary motion and dynamic forces to pump predominantly liquids. In addition to the tangential acceleration of the liquid, a centrifugal force occurring in radial flow is used for pumping, which is why such pumps are also referred to as centrifugal pumps. Centrifugal pumps are preferably used in the hydraulic systems of buildings or other applications, especially as wastewater pumps.

[0011] In normal operation of the centrifugal pump, the motor housing can be arranged above the pump housing, which contains the impeller driven by the motor via a shaft for pumping the fluid, and the centrifugal chamber. The motor housing can be permanently connected to the pump housing and / or be a single unit. The centrifugal pump and the motor can each have their own shaft, which can be connected to each other via a coupling. Preferably, the shaft projects from the motor housing into the pump housing on one drive side and / or is permanently connected to the shaft on the drive side of the impeller. Accordingly, the suction opening for the fluid to be pumped is preferably located at the bottom of the pump housing. Preferably, the motor housing and / or the pump housing are made of metal, in particular cast iron or stainless steel, ceramic, and / or plastic.

[0012] The fluid or liquid preferably comprises water or another liquid medium such as wastewater. The fluid or liquid may also include solids such as dirt, impurities, or waste of any kind, in particular feces, sediment, dirt, sand, or even small pieces of wood, brush, textiles, or rags, or the like, which can cause blockage in the pump housing. In this respect, the term "blockage" also includes partial blockage, where, for example, the impeller still rotates but is prevented from operating normally by the solid material.

[0013] The invention contributes to achieving UN Sustainable Development Goal 11 (Sustainable Cities and Communities) by improving the efficiency and reliability of wastewater systems. The described method for the automated clearing of blockages in centrifugal pumps maximizes their operating time and minimizes energy consumption. This promotes a sustainable and efficient water and wastewater infrastructure, reduces maintenance costs, and minimizes the environmental impact of unnecessary downtime and manual intervention.

[0014] According to a preferred embodiment, the method includes the step of checking whether the controller activity differs by more than 2.5%, 5%, 7.5%, 10%, or 20% before and after the threshold is undershot. This allows for flexible adaptation of the blockage detection to different operating conditions and more precise blockage detection, as it ensures significant differentiation from normal operating deviations. According to a further preferred embodiment, the method includes the step of checking whether the controller activity differs by at least 0.1%, 0.5%, 1%, 2%, 5%, or 10% before and after the threshold is undershot. In other words, it is preferably checked whether the average power output differs before and after an event, or whether a power variance, particularly fluctuation, is increased after the event, in order to detect the blockage.The threshold value is, for example, 5, 10, 15, or 20% below the controller's regular activity, i.e., during normal operation. These measures ensure robust detection of blockages over time. Furthermore, they prevent temporary, non-critical fluctuations from being falsely identified as blockages.

[0015] According to a particularly preferred embodiment, the controller's activity is further determined by the slope of a time-dependent curve, especially a derivative, of the motor current and / or torque. The controller activity is thus determined from the derivative of the manipulated variable. This enables more precise detection of changes in the motor's operating behavior, since a dynamic approach allows for a more accurate identification of deviations.

[0016] Multiplying the high-pass filtered speed of the electric motor with the high-pass filtered torque and / or motor current enables more robust detection of changes in controller activity. This multiplication yields a signal that represents the controller activity and can simultaneously distinguish between reference and disturbance behavior. This allows for reliable signal analysis by filtering out interfering DC components.

[0017] In the case of a setpoint step, the torque is increased first, followed by a corresponding increase in rotational speed. Both changes are positive, and therefore, multiplying the high-pass filtered signals also yields a positive value. If the rotational speed is reduced, the torque must first be reduced, and the rotational speed also decreases. If both changes are negative, the product or multiplication of the signals is positive. In the case of an increase in load torque, the rotational speed will preferably decrease first, so the controller responds by increasing the torque. In this case, the changes in rotational speed and torque are inversely proportional, and the product is negative.

[0018] The opposite is true when the load torque decreases. The rotational speed increases, and the controller responds primarily by reducing the load torque. Again, the product of the changes, i.e., the high-pass filtered signals, is negative. In summary, the controller activity is particularly positive when the setpoint changes and negative when a disturbance or blockage occurs.

[0019] In the task described above, only the disturbance behavior is of particular interest, since the entry of an object or foreign body into the pump housing is understood as a disturbance in the operation of the centrifugal pump with a homogeneous medium, i.e., a blockage. Calculating the controller activity by high-pass filtering and multiplying the manipulated and controlled variables, in addition to defining an undisturbed, i.e., regular, state and separating the reference and disturbance responses, has the advantage that the temporal behavior of the controller activity can be precisely adjusted by selecting a filter time constant and / or the cutoff frequency of the high-pass filter. If the filter time constant is chosen to be similar to the controller's disturbance suppression, individual events can be resolved, and in particular, blockages can be detected.

[0020] Following a preferred further training, the procedure includes the following steps: After and / or during the execution of the cleaning sequence, check whether the starting energy of the electric motor, determined by integrating an electrical power input and absorbed by the electric motor during a start-up phase, exceeds a starting energy threshold, and if so, repeat and / or continue the cleaning sequence and, in particular, otherwise drive the centrifugal pump.

[0021] In other words, the further development of the process initially includes a cleaning sequence to eliminate the blockage, particularly after it has been detected. The cleaning sequence can be designed in any way desired and might, for example, consist of a defined sequence of forward and reverse movements of the impeller of the centrifugal pump, driven by the electric motor. After and / or during this cleaning sequence, it is checked whether the starting energy consumed by the electric motor during the start-up phase, which is determined by integrating the electrical power consumption, exceeds a threshold value. If this is the case, the cleaning sequence is repeated or an already running cleaning sequence is continued.

[0022] A key aspect is that, to verify the success of the cleaning sequence—for example, whether a foreign object clogging the centrifugal pump was successfully removed—the starting energy absorbed by the centrifugal pump's electric motor during the start-up phase is determined by integrating the electric motor's electrical power consumption (i.e., its input power) and evaluated against a threshold value. The term "after and / or during" the cleaning sequence means that testing is performed, for example, when the cleaning sequence is one-quarter, half, or three-quarters complete, although smaller increments are also conceivable. Preferably, testing is performed continuously during the cleaning sequence. The starting energy threshold is preferably in the range of 10 to 10,000 Ws, more preferably in the range of 100 to 10,000 Ws, and most preferably in the range of 500 to 500 Ws.000 Ws. The starting energy threshold is preferably dependent on the centrifugal pump; it is lower for smaller centrifugal pumps and higher for larger centrifugal pumps.

[0023] Using the motor input power to indirectly assess a load torque during the cleaning sequence is advantageous because the motor input power can be easily determined due to current and voltage sensors that are already regularly present in the centrifugal pump, or may even already be available due to its use in other control systems for the centrifugal pump. The motor input power is proportional to the product of torque and speed: P Motor , shaft = M Motor , shaft * ω

[0024] In this equation P Motor, shaft the mechanical power at a motor shaft of the centrifugal pump, M Motor, shaft a wave moment and ω the rotational speed or the one with 2π Multiplied speed. The motor input power P Motor, inis greater than the engine shaft power P Motor, shaft , since losses P Loss Losses occur in the electric motor and frequency converter of the centrifugal pump, particularly due to iron and copper. Therefore: P Motor , in = M Motor , shaft + P Loss

[0025] The core aspect of the training is therefore to adapt to the load moment after and / or during the execution of the cleaning sequence. M Load corresponding energy quantity W Load to use the integration of the motor input power during the start-up phase for a load torque assessment. This energy quantity W Load However, it does not need to be determined. Since the energetic quantity W Load If part of the initial energy is involved, its determination is sufficient. This allows for a simple and reliable way to determine whether the cleaning sequence was successful or needs to be repeated or continued.

[0026] In other words, the starting energy includes the increase in kinetic energy from standstill to a certain operating speed, as well as losses such as friction, electrical losses, etc. Since these latter values ​​are often unknown and can vary depending on the direction of rotation, reference values ​​are preferably established through tests with the centrifugal pump in a clean condition. If the starting energy exceeds the reference value for a given direction when the centrifugal pump is restarted, particularly during the cleaning sequence, for example, after the electric motor or impeller stops during a reversal of rotation, it can be concluded that there is a foreign object in the pump chamber, specifically a partial or complete blockage.If, after performing the cleaning sequence (e.g., forward and reverse movements of the impeller), the starting energy in both directions of rotation of the impeller and / or the electric motor falls below the reference value, the cleaning sequence can be considered successful and terminated. Otherwise, another cleaning sequence can be started.

[0027] The proposed training makes it possible to run a flushing cycle to remove the blockage with the precise number of cleaning sequences required, without prematurely terminating the cycle or unnecessarily prolonging it. The described steps allow for efficient detection and removal of the blockage. Monitoring the starting energy during or after the cleaning sequence enables a reliable determination of the degree of blockage, allowing the process to adapt to varying operating conditions.

[0028] According to a preferred embodiment, the method includes the step of driving the centrifugal pump in regular operation if, otherwise, or if the starting energy does not exceed the starting energy threshold. In this case, it can be assumed that the blockage has been cleared, allowing the centrifugal pump to return to regular operation, i.e., the electric motor of the centrifugal pump can be driven as intended for regular operation. This enables efficient operation, as unnecessary cleaning sequences are avoided. Preferably, however, the cleaning sequence is only performed if the centrifugal pump is blocked or partially blocked, for example, due to stiffness in the centrifugal pump, particularly as a result of aging, deposits, or similar wear. This further development enables automatic blockage detection, thereby avoiding unnecessary cleaning sequences.

[0029] According to another preferred embodiment, the starting energy threshold is a reference value obtained in a reference state of the centrifugal pump, particularly when the electric motor is operated in forward and reverse directions. This allows for an evaluation of the starting energy adapted to specific operating conditions. The reference value can advantageously be tracked over the lifetime of the centrifugal pump, for example, by averaging the last 10 starts rated as unblocked, in order to avoid unnecessary cleaning cycles solely due to aging.

[0030] Alternatively or additionally, the centrifugal pump can be designed to start up from zero speed in a controlled manner during the start-up phase and then transition to speed-controlled operation. The start-up phase can begin at zero frequency at time T1 and end at time T2 when a predetermined target frequency is reached. The difference between T2 and T1 represents the acceleration time T. During the start-up phase, the centrifugal pump operates in a purely frequency-controlled manner, a so-called open loop; that is, the speed is not regulated in a closed loop.

[0031] Preferably, before the start-up phase, the rotor of the electric motor is magnetically aligned with respect to the stator field of the electric motor such that the rotor field and the stator field point in the same direction. This has the advantage that the rotor is brought into a defined, stable starting position, preventing it from starting in the wrong direction. Rotor alignment can be achieved, as is known per se, by successively applying two stator field vectors. Overall, this design ensures a controlled and optimized start-up phase.

[0032] According to a further preferred embodiment, the centrifugal pump is accelerated during the start-up phase using a defined acceleration function identical to one previously used, particularly at the factory or during customer operation, to obtain comparative values ​​for the starting energy. This allows for improved comparability of the starting energy. In one embodiment, the acceleration can also be performed with the same acceleration function at all times, i.e., during every start-up process, so that the starting energies of all centrifugal pump start-ups can be compared.

[0033] Alternatively or additionally, the acceleration function can be defined by a predetermined acceleration time, a predetermined (especially constant) acceleration profile, and a predetermined current amplitude, whereby a specific target speed is reached at the end of the acceleration time. The acceleration function during the start-up phase can be defined by the predetermined acceleration time T = T₂ - T₁, a predetermined speed profile, and a predetermined current amplitude I₂OL. A transition to speed-controlled operation preferably occurs when the specific target speed is reached at the end of the acceleration time T. In this respect, the speed can be controlled in a closed-loop control system after the start-up phase, for example, using field-oriented control. This allows for precise control of the start-up phase.

[0034] The motor input power can be determined by measuring current and voltage, preferably on the output side of a frequency converter of the centrifugal pump. By integrating the motor input power during an acceleration process in the start-up phase, the starting energy can be calculated. W This starting energy will be determined. W includes kinetic energy introduced into the centrifugal pump W kin , Engine losses W loss and an energetic quantity W load , which are representative of a certain level of load moment M load This is illustrated by the following equation: W = ∫ T 1 T 2 Pdt = W kin + W loss + W load

[0035] If the same acceleration function is always used, that is, if the acceleration always takes place with the same parameters, for example current amplitude, acceleration time, in particular ramp time, and acceleration profile, in particular ramp steepness, it can be assumed to a good approximation and neglecting temperature dependencies that in the power integral ∫ T 1 T 2 Pdt contained quantities of kinetic energy W kin as well as the engine losses W loss are always the same. Temperature dependencies can be corrected, for example, by compensation or comparison of a power integral during parking. Since the temperature essentially affects the motor resistance and thus Ri 2<, an Ri 2< integral can be determined during parking, and the integral time and current amplitudes can be corrected and subtracted from the starting energy, leaving only iron losses and W load.

[0036] From a change in starting energy W, that is, one value of the power integral ∫ T 1 T 2 Pdt , This can therefore lead to a change in size W load and thus a change in the load moment M load to be closed. In other words, based on the starting energy W It is possible to detect whether anything changes in the hydraulic system during the operation of the centrifugal pump, that is, either in the centrifugal pump itself or in the system in which the centrifugal pump delivers the fluid. This change is indicated by the change in the W load The value is represented. As already mentioned, no numerical calculation of the value is necessary. W load , since the change made by the centrifugal pump or the hydraulic system is based on the starting energy W It is recognizable, i.e., whether the cleaning sequence was successful and / or the blockage has been resolved or removed.

[0037] According to a preferred embodiment, the procedure includes the following step: if the motor current and / or torque, especially when filtered by a high-pass filter, do not differ before and after the threshold is crossed, the centrifugal pump is driven. The terms "before and after" refer specifically to 1, 2, 5, 10, 20, 30, 60, or 120 seconds before the threshold is crossed. The term "does not differ" refers specifically to no longer differing by 20, 10, 5, 2, or 0%. This embodiment ensures that a cleaning sequence is only performed if an actual blockage is present.

[0038] In principle, various methods for detecting blockages exist in the prior art. According to a preferred embodiment, blockage detection includes checking whether a calculated coefficient of variation of an operating parameter of the centrifugal pump exceeds a permissible coefficient of variation for that operating parameter. Preferably, it is checked whether the mean value of a power signal over the last number of seconds is a certain percentage lower than the mean value of the power signal after the next number of seconds. This allows for precise blockage detection based on the variability of the operating parameters.

[0039] In another preferred embodiment, the cleaning sequence includes, in particular, repeated operation of the electric motor in forward and reverse directions, including intermediate stops of the electric motor. Preferably, the start-up phase begins after the electric motor has stopped, when the electric motor begins to move in the forward and reverse directions.In a further preferred embodiment, the cleaning sequence includes, in particular, repeatedly operating the electric motor in forward and reverse directions, including stopping the electric motor in between, and / or the cleaning sequence includes first stopping the electric motor, then operating the electric motor in reverse for a predetermined flushing duration, and finally stopping the electric motor again if the torque and / or the motor current differ by more than 2.5%, particularly 5% or 10%, before and during the process, or otherwise driving the centrifugal pump. Such an embodiment improves the effectiveness of the cleaning sequence by achieving a mechanical loosening of the blockage.

[0040] The sequence of process steps can be varied unless a specific sequence is technically required. The aforementioned sequence of process steps is preferred.

[0041] The object of the invention is further solved by a centrifugal pump with an electric motor for driving the centrifugal pump and a control and / or regulation device comprising a controller for regulating the electric motor, wherein The control and / or monitoring device is configured to check whether an activity of the controller exceeds a threshold value and whether the activity of the controller before and after falling below a threshold value is below a threshold value and differs, in order to detect the blockage, wherein the activity of the controller is determined by a frequency and / or magnitude of a change in the motor current and / or torque as the manipulated variable of the controller; and if so, the control and / or monitoring device is also configured to carry out a cleaning sequence to clear the blockage.

[0042] According to a preferred embodiment, the centrifugal pump is designed as a wastewater pump. Preferably, the control and / or regulation device is computer-based, for example, designed as a microcontroller.

[0043] Preferred further developments of the centrifugal pump result in analogy to the previously described procedure. Brief description of the drawings

[0044] The invention is explained in more detail below with reference to the accompanying drawings and by way of preferred embodiments.

[0045] The drawings show Fig. 1 is a schematic view of a centrifugal pump for carrying out the proposed method according to a preferred embodiment of the invention. Fig. 2 is a flowchart for carrying out the proposed method according to the preferred embodiment of the invention. Fig. 3 is a diagram in which, at the top, a starting energy and, at the bottom, a rotational speed during operation of the centrifugal pump in forward and reverse directions are plotted for determining reference values ​​by tests in a clean state. Fig. 4 is a diagram in which, at the top, the starting energy and, at the bottom, the rotational speed during a cleaning sequence are plotted. Fig. 5 is a diagram in which, at the top, power is plotted over time and, at the bottom, a coefficient of variation is plotted over time. Fig. 6 shows an exemplary diagram in which, from top to bottom, a motor current, the rotational speed, and a controller activity are plotted over time. Detailed description of the implementation examples

[0046] Fig. 1 Figure 1 shows a schematic view of a centrifugal pump 1 for carrying out a method described below, in particular for detecting and subsequently remedying or resolving the blockage of the centrifugal pump 1 according to a preferred embodiment of the invention.

[0047] The centrifugal pump 1, designed as a wastewater pump, has a conventional pump housing 2 with a suction opening 3 located at the bottom of the pump housing 2 as an inlet. A rotor 4 is provided in the pump housing 2, extending vertically in the drawing. The rotor 4 is part of an electric motor 5, shown only partially, which is arranged opposite the suction opening 3. An impeller 6 is provided facing the suction opening 3 and is driven by the rotor 4 of the electric motor 5. Furthermore, the centrifugal pump 1 has a microprocessor-based control unit 7 or a controller 7, in Fig. 1 only hinted at.

[0048] Finally, the centrifugal pump 1 has a sensor 8 for detecting the current and voltage drawn by the electric motor 5 of the centrifugal pump 1. The sensor 8 is accordingly configured as a current and / or voltage sensor. The following method, particularly the computer-implemented method, for detecting and clearing a blockage in the centrifugal pump 1 is carried out by a computer (not shown), in particular the control unit 7.

[0049] The procedure includes the in Fig. 2 schematically represented steps: Checking whether the activity of the controller 7 falls below a threshold value and whether the motor current and / or torque of the electric motor 5 differs before and after the threshold is crossed, in order to detect the blockage, wherein the activity of the controller 7 is determined by a product of the high-pass filtered speed of the electric motor 5 and the high-pass filtered motor current and / or high-pass filtered torque of the electric motor 5, 100, in particular if affirmative, after and / or during a cleaning sequence to clear the blockage, checking whether a starting energy absorbed by the electric motor 5 during a start-up phase, determined by integrating an electrical power consumption of the electric motor 5, exceeds a starting energy threshold, 200; and if affirmative, repeating and / or further performing the cleaning sequence 300.

[0050] The procedure can be subdivided into two essential aspects: firstly, the detection of a blockage, followed by the execution of the cleaning sequence to clear it; and secondly, the verification, either during or after the cleaning sequence, of whether the blockage has been cleared and, if necessary, the repetition and / or further execution of the cleaning sequence. The second aspect will be described first, followed by the first.

[0051] The cleaning sequence that occurs when the centrifugal pump 1 becomes clogged includes repeatedly operating the electric motor 5 in forward and reverse directions, including stopping the electric motor 5 in between. During an acceleration process of the electric motor 5 in the start-up phase from the stopped electric motor 5 in forward and reverse directions, a motor shaft and the associated impeller 6 of the centrifugal pump 1 are accelerated according to a defined acceleration function.

[0052] During the start-up phase, centrifugal pump 1 initially ramps up from zero speed under controlled conditions and then transitions to speed-controlled operation. In this start-up phase, centrifugal pump 1 accelerates according to a defined acceleration function, identical to the acceleration function previously used to obtain comparative values ​​for the starting energy. The acceleration function is defined by a predetermined acceleration time, a predetermined (in particular, constant) acceleration profile, and a predetermined current amplitude, whereby a specific target speed is reached at the end of the acceleration time. The starting energy includes the increase in kinetic energy from standstill to a specified evaluation speed and losses such as friction, electrical losses, etc.

[0053] Since the latter values ​​in particular are often unknown and can differ depending on the direction of rotation, reference values ​​are preferably established by tests with the centrifugal pump 1 in a clean condition. In the diagram of the Fig. 3 The starting energy is plotted above and the rotational speed during operation of centrifugal pump 1 in forward and reverse directions as examples for determining reference values ​​through tests in a clean state.

[0054] If the starting energy during a restart of centrifugal pump 1, especially during the cleaning sequence, exceeds the reference value for a given direction, it can be concluded that there is a foreign object in the pump chamber, i.e., in particular a partial blockage or blockage.

[0055] Specifically, during this start-up phase, the current and voltage drawn by the electric motor 5 are measured using the defined acceleration function via sensor 8. From this, the motor input power, i.e., the electrical power consumption of the electric motor 5 during the start-up phase, is determined. Current and voltage are preferably measured at the output side of a frequency converter of the centrifugal pump 1. By integrating the motor input power during the acceleration process in the start-up phase, the starting energy is determined.

[0056] This starting energy W includes kinetic energy introduced into the centrifugal pump W kin , Engine losses W loss and an energetic quantity W load , which are representative of a certain level of load moment M load is, as illustrated by the following equation: W = ∫ T 1 T 2 Pdt = W kin + W loss + W load

[0057] Then, the control and / or regulation device 7 is used to check whether the starting energy determined in this way is sufficient. W The system checks whether a starting energy threshold is exceeded, i.e., whether centrifugal pump 1 is clogged. This check is performed after and / or during the cleaning sequence, for example, periodically and / or each time electric motor 5 restarts.

[0058] If the check reveals that the starting energy threshold has been exceeded, meaning that centrifugal pump 1 remains clogged, the cleaning sequence is repeated and / or continued. Otherwise, if the starting energy no longer exceeds the starting energy threshold, meaning the clog has been removed, the electric motor 5 of centrifugal pump 1 is driven normally, or centrifugal pump 1 is operated normally again.

[0059] In the diagram of Fig. 4The starting energy is plotted above and the rotational speed during a cleaning sequence below as examples. When a blockage is detected as described below, the cleaning sequence begins and ends after the starting energy of electric motor 5 falls below the starting energy threshold again.

[0060] Prior to carrying out the cleaning sequence, it is necessary to detect whether the centrifugal pump 1 is clogged, for which various methods are possible. In one variant, the detection of a clog involves checking whether a calculated coefficient of variation of an operating parameter of the centrifugal pump 1 exceeds a permissible coefficient of variation for that operating parameter. Fig. 5 The diagram shows an example where the power over time is plotted at the top and the coefficient of variation over time is plotted at the bottom.

[0061] In a preferred second embodiment, the electric motor 5 is controlled by means of the controller 7, which is part of the control and / or regulation device 7. Specifically, in this second embodiment, the control and / or regulation device 7 checks whether the activity of the controller 7 falls below the threshold value and whether the motor current and / or torque of the electric motor 5 differs before and after the threshold is crossed, wherein the activity of the controller 7 is determined by the product of the high-pass filtered speed of the electric motor 5 and the high-pass filtered motor current and / or high-pass filtered torque of the electric motor 5, in particular to distinguish between normal and disturbance behavior.

[0062] Fig. 6Figure 1 shows an example diagram plotting motor current, speed, and controller activity over time from top to bottom. A disturbance event is evident, as the controller activity decreases over time. Since the activity of controller 7 falls below the threshold value (in this case, it has a negative sign), and since the activity of controller 7 differs between the threshold value and the disturbance event, it can be concluded that there is a disruptive object in the pump housing that negatively affects the pump's efficiency. Therefore, the previously described cleaning sequence can be initiated.

[0063] The activity of the controller 7 can also be determined by the slope of a time-dependent curve, in particular a derivative, of the motor current and / or torque. Specifically, the activity of the controller 7 is determined by multiplying the high-pass filtered speed of the electric motor 5 by the high-pass filtered torque and / or high-pass filtered motor current. The activity of the controller 7 before and after the threshold is crossed must differ by more than 2.5%, 5%, 7.5%, 10%, or 20%. Furthermore, the activity of the controller 7 is considered for at least 0.1%, 0.5%, 1%, 2%, 5%, or 10 seconds before and after the threshold is crossed.

[0064] The described embodiments are merely examples that can be modified and / or supplemented in various ways within the scope of the claims. Each feature described for a particular embodiment can be used independently or in combination with other features in any other embodiment. Each feature described for an embodiment of a particular category can also be used accordingly in an embodiment of a different category. Reference symbol list

[0065] centrifugal pump 1 Pump housing 2 Suction opening 3 rotor 4 electric motor 5 balance bike 6 Control and / or regulating device, controller 7 sensor 8 Check whether the activity of the controller 7 falls below a threshold value and whether the motor current and / or torque of the electric motor 5 differs before and after the threshold is crossed, in order to detect the blockage, wherein the activity of the controller 7 is determined by a product of the high-pass filtered speed of the electric motor 5 and the high-pass filtered motor current and / or high-pass filtered torque of the electric motor 5 after and / or during a cleaning sequence to clear the blockage, check whether a change in the motor current and / or torque of the electric motor 5 is detected during a 100 The starting energy recorded during the start-up phase, determined by integrating the electrical power consumption of the electric motor 5, exceeds a starting energy threshold. 200 If affirmative, repeat and / or further execution of the cleaning sequence 300

Claims

1. Method for detecting and clearing a blockage in a centrifugal pump (1) with an electric motor (5) controlled by a controller (7) for driving the centrifugal pump (1), comprising the steps of: checking whether the activity of the controller (7) falls below a threshold value and whether the motor current and / or torque of the electric motor (5) differs before and after the threshold is crossed, in order to detect the blockage, wherein the activity of the controller (7) is determined by a product of the high-pass filtered speed of the electric motor (5) and the high-pass filtered motor current and / or high-pass filtered torque of the electric motor (5) (100); and if so, performing a cleaning sequence to clear the blockage.

2. Method according to the preceding claim, comprising the step: checking whether the activity of the controller (7) differs by more than 2.5, 5, 7.5, 10 or 20% before and after the threshold is undershot.

3. Method according to one of the preceding claims, comprising the step: checking whether the activity of the controller (7) differs at least 0.1, 0.5, 1, 2, 5 or 10 seconds before and after the threshold is undershot.

4. Method according to one of the preceding claims, wherein the activity of the controller (7) is further determined in particular by a slope of a time course, in particular a derivative, of the motor current and / or the torque.

5. Method according to any of the preceding claims, wherein the threshold is zero.

6. Method according to one of the preceding claims, comprising the steps: after and / or during the execution of the cleaning sequence, checking whether a starting energy of the electric motor (5) absorbed by the electric motor (5) in a start-up phase, determined by integrating an electrical power input, exceeds a starting energy threshold (200), and if so, repeating and / or further performing the cleaning sequence (300) and in particular otherwise driving the centrifugal pump (1).

7. Method according to the preceding claim, wherein the starting energy threshold is a reference value obtained in a reference state of the centrifugal pump (1), in particular when operating the electric motor (5) in forward and reverse directions.

8. Method according to one of the two preceding claims, wherein the centrifugal pump (1) initially runs up from zero speed in a controlled manner during the start-up phase and then transitions to speed-controlled operation.

9. Method according to one of the three preceding claims, wherein in the start-up phase the centrifugal pump (1) is accelerated with a defined acceleration function which is identical to an acceleration function which was previously used to obtain comparative values ​​for the starting energy.

10. Method according to the preceding claim, wherein the acceleration function is defined by a predetermined acceleration time, a predetermined, in particular constant, acceleration profile and a predetermined current amplitude, wherein a specific target rotational speed is reached at the end of the acceleration time.

11. Method according to one of the preceding claims, comprising the step: if the motor current, in particular the high-pass filtered motor current and / or the torque, in particular the high-pass filtered torque, does not differ before and after the threshold is undercut, driving the centrifugal pump (1).

12. Method according to one of the preceding claims, wherein the detection of the blockage comprises checking whether a calculated coefficient of variation of an operating parameter of the centrifugal pump (1) exceeds a permissible coefficient of variation of the operating parameter.

13. Method according to one of the preceding claims, wherein the cleaning sequence comprises, in particular, repeated operation of the electric motor (5) in forward and reverse directions, including intermediate stopping of the electric motor (5), and / or wherein the cleaning sequence first comprises stopping the electric motor (5), then operating the electric motor (5) in reverse for a predetermined rinsing duration, and finally stopping the electric motor (5) again if the torque and / or the motor current differ, in particular, by more than 2.5% before and during the period of insufficient torque, or otherwise driving the centrifugal pump (1).

14. Centrifugal pump (1) with an electric motor for driving the centrifugal pump (1) and a control and / or regulation device (7) comprising a controller (7) for regulating the electric motor, wherein the control and / or regulation device (7) is configured to check whether the activity of the controller (7) falls below a threshold value and whether the motor current and / or torque of the electric motor (5) differs before and after the threshold is crossed, in order to detect the blockage, wherein the activity of the controller (7) is determined by a product of the high-pass filtered speed of the electric motor (5) and the high-pass filtered motor current and / or high-pass filtered torque of the electric motor (5); and if so, the control and / or regulation device (7) is configured to perform a cleaning sequence to clear the blockage.

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