EP1564411B2 - Method for detecting operation errors of a pump aggregate - Google Patents

Abstract

In a process to detect a fault during operation of an electric motor-powered pump, a monitoring has two electric wires linking the electric motor to a power monitoring system, and a further sensor monitoring a hydraulic parameter in the pump. The electrical and hydraulic values are logged and processed in an algorithm by a data processing system, the results being compared with pre-stored values. Also claimed is a commensurate pump monitoring system.

Description

The invention relates to a method for determining errors in the operation of a pump unit, in particular a centrifugal pump unit according to the features specified in the preamble of claim 1.

Out EP-A-1 286 056 It belongs to the state of the art to detect in a pump unit cavitation in the region of the pump by means of sensors which record the pump differential pressure and the flow rate. The data recorded by the sensors are fed to a classification system which determines through a neural network whether and to what extent cavitation exists.

Out EP-A-0 321 295 It belongs to the state of the art to detect by means of a variety of sensors hydraulic system data and mechanical data of the pump motor to detect critical operating conditions of the pump and turn off the pump if necessary in time when the pump z. B. runs dry or promotes closed valves.

Out Wolfram, Armin, Dominik Füssel, Torsten Brune and Rolf Isermann, Component-based multi-model approach for fault detection and diagnosis of a centrifugal pump, Institute of Autom. Control, Darmstadt University of Technology; American Control Conference, 2001: Proceedings of the 2001; Volume: 6, On page (s): 4443-4448 vol. 6; ISBN: 078036495-3 , it is known to monitor plants with integrated pump sets, wherein the monitoring of individual plant components, such as pump, mechanical system, pipeline, each model-based, by comparing a magnitude calculated by a mathematical model with a measured one, and then determining whether or not there is an error. As a model, among other things, a motor model and a pump model are used. As input for the aforementioned model calculations, the speed is used.

Such a monitoring system is also made of tungsten, Armin, component-based fault diagnosis industrial plants using the example of frequency converter-fed asynchronous and centrifugal pumps, dissertation TU Darmstadt, VDI Forfschrittsberichte, Series 8, No. 967, VDI Verlag 2002 , Dusseldorf known. There are also described in particular the model relationships between the engine and pump. This prior art forms the preamble of claim 1.

In the meantime, pump units are therefore considered to be the state of the art for providing a large number of sensors, on the one hand in order to detect operating conditions, and on the other hand also to determine fault conditions of the system and / or the pump unit. The disadvantage here, however, is that the sensors required in this context not only consuming and expensive, but is often prone to failure.

Against this background, the invention has for its object to provide a method for detecting errors in the operation of a pump unit, which is executable with the lowest possible sensor.

This object is achieved according to the invention by the features specified in claim 1. Advantageous embodiments of the method according to the invention will become apparent from the dependent claims, the following description and the figures.

The basic idea of the present invention is to record characteristic data using characteristic electrical quantities of the motor which are generally available anyway or at least with little effort and two variable hydraulic variables to be determined by sensor for the electric motor and the hydraulic-mechanical pump to evaluate according to mathematical linkage. In the simplest form, this is done by comparison with predetermined values, wherein both the comparison and the result is done automatically by means of electronic data processing, which thus determines whether an error in the operation of the pump is present or not.

The method according to the invention requires a minimum of sensor technology and, in the case of modern frequency-converter-controlled pumps, which in any case have digital data processing, can generally be implemented by software. It is particularly advantageous that the variables determining the electrical power of the motor, namely typically the voltage applied to the motor and the current supplying the motor, are anyway available within the frequency converter electronics, so that for detecting a hydraulic variable, e.g. the differential pressure only a pressure sensor is required, which incidentally also often belongs to standard equipment in modern pumps. The predetermined values required for comparison can be stored in digital form in corresponding memory modules of the engine electronics.

According to the invention, it is provided that, on the one hand, the two electrical quantities of the motor determining the electrical power of the motor, namely the voltage applied to the motor and the current supplying the motor, are mathematically linked to obtain at least one reference value and, on the other hand, the at least one variable hydraulic variable the pump and another determining the performance of the pump hydraulic variable to achieve at least one further comparison value are mathematically linked, wherein it is then determined on the basis of the result of the mathematical combination by comparison with predetermined values, whether an error exists or not. The mathematical combination is carried out for the motor-side data by appropriate for the electrical and / or magnetic relationships in the engine determining equations whereas equations are used for the pump, which describe the hydraulic and / or mechanical system. The values resulting from the respective links are compared with predetermined values stored in the memory electronics, after which the electronic data processing automatically determines whether an error exists or not. and The method according to the invention has the advantage that it requires little storage space for the given values.

It can not only be determined with the inventive method whether an error is present, but it can also be advantageously also the error specified, i. be determined which error it is.

As to be detected hydraulic variable is the generated by the pump. Used differential pressure, since this size can be detected on the aggregate side and the provision of such a pressure sensor in many pump types today is state of the art.

In addition to the detection of the differential pressure is used as a hydraulic variable, the flow rate of the pump. The detection of the flow rate can also be done on the aggregate side, also for this purpose are less expensive and long-term stable measuring systems available.

Since the absolute pressure detection of the pressure generated by the pump always represents a differential pressure measurement against the outside atmosphere, it is often cheaper to detect the differential pressure formed between suction and pressure side of the pump instead of the absolute pressure, which is also much cheaper to further process as a hydraulic variable of the pump.

$$L{ʹ}_s\frac{d{i}_{sq}}{dt}=-R{ʹ}_s{i}_{sq}+\frac{L_m}{L_r}\left(R{ʹ}_r{\psi }_{rq}-z_p\omega {\psi }_{rd}\right)+v_{sq}$$

$$\frac{d{\psi }_{rd}}{dt}=-R{ʹ}_r{\psi }_{rd}-z_p\omega {\psi }_{rq}+R{ʹ}_r{L}_m{i}_{sd}$$

$$\frac{d{\psi }_{rq}}{dt}=-R{ʹ}_r{\psi }_{rq}+z_p\omega {\psi }_{rd}+R{ʹ}_r{L}_m{i}_{sq}$$

$$T_e=z_p\frac{3}{2}\frac{L_m}{L_r}\left({\psi }_{rd}{i}_{sq}-{\psi }_{rq}{i}_{sd}\right)$$

According to the invention, an electrical motor model is used for the mathematical combination for the variables determining the electrical power of the motor, and a mechanical-hydraulic pump model is used for the mathematical combination of the mechanical-hydraulic pump variable. Here, as the electric motor model, it is preferable to use one defined by the equations (1) to (5) or (6) to (9) or (10) to (14). $$L{\text{'}}_s\frac{d{i}_{sd}}{dt}=-R{\text{'}}_s{i}_{sd}+\frac{L_m}{L_r}\left(R{\text{'}}_r{\psi }_{rd}+z_p\omega {\psi }_{rq}\right)+v_{sd}$$

$$L{\text{'}}_s\frac{d{i}_{sq}}{dt}=-R{\text{'}}_s{i}_{sq}+\frac{L_m}{L_r}\left(R{\text{'}}_r{\psi }_{rq}-z_p\omega {\psi }_{rd}\right)+v_{sq}$$

$$\frac{d{\psi }_{rd}}{dt}=-R{\text{'}}_r{\psi }_{rd}-z_p\omega {\psi }_{rq}+R{\text{'}}_r{L}_m{i}_{sd}$$

$$\frac{d{\psi }_{rq}}{dt}=-R{\text{'}}_r{\psi }_{rq}+z_p\omega {\psi }_{rd}+R{\text{'}}_r{L}_m{i}_{sq}$$

$$T_e=z_p\frac{3}{2}\frac{L_m}{L_r}\left({\psi }_{rd}{i}_{sq}-{\psi }_{rq}{i}_{sd}\right)$$

$$\omega ={\omega }_s-s{\omega }_s$$

$$I_r=\frac{V_s}{Z_r\left(s\right)}$$

$$T_e=\frac{3R_r{I}_r^2}{s}$$

Equations (1) to (5) represent an electric dynamic motor model for an asynchronous motor. $$V_s=Z_s\left(s\right)I_s$$

$$\omega ={\omega }_s-s{\omega }_s$$

$$I_r=\frac{V_s}{Z_r\left(s\right)}$$

$$T_e=\frac{3R_r{I}_r^2}{s}$$

$$L_s\frac{d{i}_{sq}}{dt}=-R_s{i}_{sq}-z_p\omega L_s{\psi }_{rd}+v_{sq}$$

$$\frac{d{\psi }_{rd}}{dt}=-z_p\omega {\psi }_{rq}$$

$$\frac{d{\psi }_{rq}}{dt}=z_p\omega {\psi }_{rd}$$

$$T_e=z_p\frac{3}{2}\left({\psi }_{rd}{i}_{sq}-{\psi }_{rq}{i}_{sd}\right)$$

Equations (6) to (9) also represent an electric static motor model for an asynchronous motor. $$L_s\frac{d{i}_{sd}}{dt}=-R_s{i}_{sd}+z_p\omega L_s{\psi }_{rq}+v_{sd}$$

$$L_s\frac{d{i}_{sq}}{dt}=-R_s{i}_{sq}-z_p\omega L_s{\psi }_{rd}+v_{sq}$$

$$\frac{d{\psi }_{rd}}{dt}=-z_p\omega {\psi }_{rq}$$

$$\frac{d{\psi }_{rq}}{dt}=z_p\omega {\psi }_{rd}$$

$$T_e=z_p\frac{3}{2}\left({\psi }_{rd}{i}_{sq}-{\psi }_{rq}{i}_{sd}\right)$$

Equations (10) to (14) represent an electric dynamic motor model for a permanent magnet motor.

• i_sd den Motorstrom in Richtung d
• i_sq den Motorstrom in Richtung q
• ψ_rd den magnetischen Fluss des Rotors in d-Richtung
• ψ_rq den magnetischen Fluss des Rotors in q-Richtung
• T_e das Motormoment
• v_sd die Versorgungsspannung des Motors in d-Richtung
• v_sq die Versorgungsspannung des Motors in q-Richtung
• ω die Winkelgeschwindigkeit des Rotors und Laufrades
• R' _s den Ersatzwiderstand der Statorwicklung
• R'_r den Ersatzwiderstand der Rotorwicklung
• L_m den induktiven Kopplungswiderstand zwischen Stator- und Rotorwicklung
• L'_s den induktiven Ersatzwiderstand der Statorwicklung
• L_r den induktiven Widerstand der Rotorwicklung
• z_p die Polpaarzahl
• I_s den Phasenstrom
• V_s die Phasenspannung
• ω_s die Frequenz der Versorgungsspannung
• ω die tatsächliche Rotor- und Laufraddrehzahl
• s den Motorschlupf
• Z_s (s) die Statorimpedanz
• Z_r(s) die Rotorimpedanz
• R_r den Ersatzwiderstand der Rotorwicklung
• R_s den Ersatzwiderstand der Statorwicklung
• L_s Den induktiven Widerstand der Statorwicklung,

wobei d uns q zwei senkrecht zueinander stehende Richtungen senkrecht zur Motorwelle sind,Represent in equations (1) to (14)

• i _sd the motor current in direction d
• i _sq the motor current in direction q
• ψ _rd the magnetic flux of the rotor in d-direction
• ψ _rq the magnetic flux of the rotor in q-direction
• T _e the engine torque
• v _{sd is} the supply voltage of the motor in d-direction
• v _{sq is} the supply voltage of the motor in q-direction
• ω the angular velocity of the rotor and impeller
• R ' _s the equivalent resistance of the stator winding
• R ' _r the equivalent resistance of the rotor winding
• L _m the inductive coupling resistance between stator and rotor winding
• L ' _s the inductive equivalent resistance of the stator winding
• L _r the inductance of the rotor winding
• z _{p is} the pole pair number
• I _s the phase current
• V _{s is} the phase voltage
• ω _{s is} the frequency of the supply voltage
• ω the actual rotor and impeller speed
• s the engine slip
• Z _s ( s ) the stator impedance
• Z _r (s) the rotor impedance
• R _r the equivalent resistance of the rotor winding
• R _{s is} the equivalent resistance of the stator winding
• L _s The inductive resistance of the stator winding,

where d and q are two perpendicular directions perpendicular to the motor shaft,

For the mechanical-hydraulic pump model, equation (15) and at least one of equations (16) and (17) are advantageously used.

und mindestens eine der Gleichungen $$H_p=-a_{h2}{Q}^2+a_{h1}Q\omega +a_{h0}{\omega }^2$$

$$T_p=-a_{t2}{Q}^2+a_{t1}Q\omega +a_{t0}{\omega }^2$$

in denen

• $\frac{d\omega }{dt}$
  
  die zeitliche Ableitung der Winkelgeschwindigkeit des Rotors,
• T_p das Pumpendrehmoment,
• J das Massenträgheitsmoment von Rotor, Laufrad und im Laufrad gebundener Förderflüssigkeit,
• B die Reibungskonstante,
• Q der Förderstrom der Pumpe,
• H_p der von der Pumpe erzeugten Differenzdruck,
• a _h2 ,a _h1, a _h0 die Parameter, die den Zusammenhang zwischen Drehzahl des Laufrades, Förderstrom und Differenzdruck beschreiben und
• a _t2 ,a _t1,a _t0 die Parameter, die den Zusammenhang zwischen Drehzahl des Laufrades, Förderstrom und Massenträgheitsmoment beschreiben

Equation (15) represents the mechanical relationships between motor and pump, whereas equations (16) and (17) describe the mechanical-hydraulic relationships in the pump. These equations are: $$J\frac{d\omega }{dt}=T_e-B\omega -T_P$$

and at least one of the equations $$H_p=-a_{H2}{\mathrm{<figure-callout\; id="2"\; label="Q"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">Q</figure-callout>}}^2+a_{H1}Q\omega +a_{H0}{\omega }^2$$

$$T_p=-a_{t2}{\mathrm{<figure-callout\; id="2"\; label="Q"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">Q</figure-callout>}}^2+a_{t1}Q\omega +a_{t0}{\mathrm{<figure-callout\; id="2"\; label="\omega "\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">\omega </figure-callout>}}^2$$

in which

• $\frac{d\omega }{dt}$
  
  the time derivative of the angular velocity of the rotor,
• T _{p is} the pump torque,
• J the mass moment of inertia of rotor, impeller and in the impeller bound delivery liquid,
• B the friction constant,
• Q is the flow rate of the pump,
• H _{p is} the differential pressure generated by the pump
• a _{h 2} , a _{h 1} , a _{h 0 are} the parameters that describe the relationship between the speed of the impeller, the flow rate and the differential pressure, and
• a _{t 2} , a _{t 1} , a _{t 0 are} the parameters describing the relationship between the speed of the impeller, the flow rate and the mass moment of inertia

Claim 4 defines, by way of example, how mathematical links are made to determine whether an error exists or not. The basic idea of this specific method is, on the one hand with the aid of the engine model, to determine the engine torque resulting from the electrical variables on the motor shaft and the rotational speed. Equations (16) and (17) are used to determine a relationship between the differential pressure and the delivery flow on the one hand and between the pump pressure torque and the delivery flow on the other hand.

In order to give the system a certain tolerance, it may be useful to set a tolerance _band by variance of at least one of the variables a _h0 to a _h2 , a _t0 to a _t2 , B and J in order to register an error only if this too is relevant to the operation.

In order to be able to specify the type of error more precisely, in addition to the two electrical variables, two hydraulic variables are determined by measuring and the determined values are inserted into the equations according to claim 4, so that then four error variables r ₁ to r ₄ result. Based on the combination of these error variables, the type of error is then determined on the basis of predetermined limit value combinations. This too is done automatically by electronic data processing.

In an alternative development of the method according to the invention, in addition to the two electrical magnitudes, the two aforementioned hydraulic variables are determined by measuring and the determined values are compared with predetermined values to determine the type of error, in which case the predefined values define an area in three-dimensional space It is determined whether or not the determined quantities lie on these areas (r * ₁ to r * ₄ ) and, based on the combination of the values, the type of error is determined on the basis of predetermined limit value combinations. The type of error can then be determined, for example, from the following table: Error type defect size r ₁ , r ₂ , r ₃ , r ₄ , comparison area r ₁ * r ₂ * r ₃ * r ₄ * Increased friction due to mechanical defects 1 0 1 1 Reduced delivery / missing differential pressure 0 1 1 1 Defective in the intake area / missing flow 1 1 0 1 Fjord failure 1 1 1 1

With the aid of the method according to the invention, it is thus possible not only to determine or not to determine the fault-free operating state of the pump set with a minimum of sensor, but moreover to specify it in detail in the event of a fault, so that a corresponding error signal is generated in the pump set which indicates the type of error. This signal may optionally be transmitted to remote locations where the function of the pump set is to be monitored.

The surfaces formed in the three-dimensional space on the basis of predetermined values are typically space-curved surfaces whose values have previously been determined by the factory based on the respective unit or aggregate type and stored in the digital data memory on the aggregate side. The aforementioned comparison surfaces r * ₁ to r * _{4 are arranged} in a three-dimensional space, which at r * ₁ from the torque, the flow and the speed, at r * ₂ from the differential pressure, the flow rate and the speed, for r * ₃ of the torque, the differential pressure and the speed and for r * ₄ from the torque, the differential pressure and the flow rate are formed.

The variables defined in the table by the comparison surfaces r * ₁ to r * ₄ indicate the respective operating state, wherein the number 0 means that the respective value lies within the area defined by the predetermined values and 1 outside. For example, the error combination defined in the table due to increased friction due to mechanical defects can mean bearing damage or an otherwise caused increased frictional resistance between the rotating parts and the stationary parts of the aggregate. The under the generic term reduced promotion / missing differential pressure marked error combination can be, for example, by error or wear on the pump impeller or an obstacle in the pump Einoder Exhaust caused. Defined under the generic term defect in the intake / missing flow error combination can be caused for example by defect of the ring seal at the suction of the pump. The error combination under the generic term Förderausfall can have a variety of causes and should be further specified if necessary. This delivery failure can be caused by a blocked shaft or jammed pump impeller, shaft breakage, pump impeller loosening, cavitation due to impermissibly low differential pressure at the pump inlet, and dry running.

The operating states designated in the table by the variables R ₁ to R ₄ are based on mathematical calculations of fault parameters r ₁ to r ₄ according to the equations (19) to (22), wherein the corresponding error amount becomes zero when a correct operation is present and the value 1 in case of error. The table is to be understood in terms of the type of error in a similar manner as described above. Figuratively speaking, each of the error quantities r ₁ to r _{4 represents} a distance to the corresponding areas r * ₁ to r * ₄ . However, the error quantities do not necessarily correspond to the areas r * ₁ to r * ₄ . The error quantities r ₁ to r ₄ correspond to the equations (19) to (22) and correspond to the areas r * ₁ to r * ₄ in the FIGS. 4 to 9 ,

In order to further differentiate the nature of the error, it is provided in a further development of the invention that, when a fault is detected, the pump unit is actuated with a different speed, in order then to be able to define the detected error more precisely on the basis of the resulting measuring results.

$$\{r_2=q_2\left(-a_{h2}{Q}^2+a_{h1}\omega Q+a_{h0}{\omega }^2-H_p\right)$$

$$\{\begin{array}{ccc}\hfill Qʹ& =& \frac{a_{h1}\omega +\sqrt{a_{h1}^2{\omega }^2-4a_{h2}\left(H_p+a_{h0}{\omega }^2\right)}}{2a_{h2}}\hfill \\ \hfill J\frac{d{\hat{\omega }}_3}{dt}& =& -B{\hat{\omega }}_3-\left(-a_{t2}{\mathit{Qʹ}}^2+a_{t1}Qʹ\omega +a_{t0}{\omega }^2\right)+T_e+k_3\left(\omega -{\hat{\omega }}_3\right)\hfill \\ \hfill r_3& =& q_3\left(\omega -{\hat{\omega }}_3\right)\hfill \end{array}$$

$$\{\begin{array}{ccc}\hfill \omega ʹ& =& \frac{{-a}_{h1}{H}_p+\sqrt{a_{h1}^2{H_p}^2-4a_{h2}\left(H_p+a_{h0}{Q}^2\right)}}{2a_{h2}}\hfill \\ \hfill J\frac{d{\hat{\omega }}_4}{dt}& =& -B{\hat{\omega }}_4-\left(-a_{t2}{\mathit{Q}}^2+a_{t1}Q\omega ʹ+a_{t0}{\omega ʹ}^2\right)+T_e+k_4\left(\omega ʹ-{\hat{\omega }}_4\right)\hfill \\ \hfill r_4& =& q_4\left(\omega ʹ-{\hat{\omega }}_4\right)\hfill \end{array}$$

in denen

• k ₁ ,k ₃ ,k ₄ Konstanten,
• q₁ ,q ₂ ,q ₃,q ₄ Konstanten,
• Q' Der berechnete Förderstrom auf Basis von aktueller Drehzahl und gemessenem Differenzdruck,
• ω̂₁ die berechnete Rotordrehzahl auf Grundlage der mechanisch-hydraulischen Gleichungen (15) und (17),
• ω̂₃ die berechnete Rotordrehzahl auf Grundlage der Gleichungen (15), (16) und (17),
• ω̂₄ die berechnete Rotordrehzahl auf Grundlage der Gleichungen (15), (16) und (17),
• ω' die berechnete Rotordrehzahl aufgrund gemessenen Differenzdrucks und gemessenem Förderstrom
• r ₁-r ₄ Fehlergrößen und
• r ₁ *-r ₄* durch drei Variable bestimmte Flächen sind, die einen fehlerfreien Betrieb der Pumpe repräsentieren.

The error quantities r ₁ to r ₄ are advantageously defined by the equations (19) to (22): $$\{\begin{array}{cc}\hfill J\frac{d{\hat{\omega }}_1}{dt}& =-B{\hat{\omega }}_1-\left(-a_{t2}{Q}^2+a_{t1}Q\omega +a_{t0}{\omega }^2\right)+T_e+k_e\left(\omega -{\hat{\omega }}_1\right)\hfill \\ \hfill r_1& =q_1\left(\omega -{\hat{\omega }}_1\right)\hfill \end{array}$$

$$\{r_2=q_2\left(-a_{H2}{Q}^2+a_{H1}\omega Q+a_{H0}{\omega }^2-H_p\right)$$

$$\{\begin{array}{ccc}\hfill Q\text{'}& =& \frac{a_{H1}\omega +\sqrt{a_{H1}^2{\omega }^2-4a_{H2}\left(H_p+a_{H0}{\omega }^2\right)}}{2a_{H2}}\hfill \\ \hfill J\frac{d{\hat{\omega }}_3}{dt}& =& -B{\hat{\omega }}_3-\left(-a_{t2}{\mathit{Q\; \text{'}}}^2+a_{t1}Q\text{'}\omega +a_{t0}{\omega }^2\right)+T_e+k_3\left(\omega -{\hat{\omega }}_3\right)\hfill \\ \hfill r_3& =& q_3\left(\omega -{\hat{\omega }}_3\right)\hfill \end{array}$$

$$\{\begin{array}{ccc}\hfill \omega \text{'}& =& \frac{{-a}_{H1}{H}_p+\sqrt{a_{H1}^2{H_p}^2-4a_{H2}\left(H_p+a_{H0}{Q}^2\right)}}{2a_{H2}}\hfill \\ \hfill J\frac{d{\hat{\omega }}_4}{dt}& =& -B{\hat{\omega }}_4-\left(-a_{t2}{\mathit{Q}}^2+a_{t1}Q\omega \text{'}+a_{t0}{\omega \text{'}}^2\right)+T_e+k_4\left(\omega \text{'}-{\hat{\omega }}_4\right)\hfill \\ \hfill r_4& =& q_4\left(\omega \text{'}-{\hat{\omega }}_4\right)\hfill \end{array}$$

in which

• k ₁ , k ₃ , k ₄ constants,
• q ₁ , q ₂ , q ₃ , q ₄ constants,
• Q ' The calculated flow rate based on actual speed and differential pressure,
• ω _{1 is} the calculated rotor speed based on the mechanical-hydraulic equations (15) and (17),
• ω _{3 is} the calculated rotor speed based on equations (15), (16) and (17),
• ω ₄ the calculated rotor speed based on equations (15), (16) and (17),
• ω 'the calculated rotor speed based on measured differential pressure and measured flow
• r ₁ - r ₄ error quantities and
• r ₁ * -r ₄ * are areas determined by three variables which represent a faultless operation of the pump.

According to the invention, therefore, a sensor is provided for detecting the voltage applied to the motor supply voltage and the supply current and for detecting the differential pressure applied by the pump and the flow rate. In addition, an evaluation device to be provided, which in the form of digital data processing, for. B. a microprocessor may be formed, in which the inventive method is implemented by software. In order to be able to carry out the comparison between detected or calculated values and specified values (eg recorded and stored by the factory), an electronic memory is also to be provided. In modern frequency converter controlled pump units all the aforementioned hardware requirements are already in place, so that is only to ensure sufficient dimensioning of the electronic data processing system, in particular the storage means and the evaluation device. All components, with the exception of the sensors required for the detection of hydraulic variables, are preferably an integral part of the motor and / or pump electronics, so that constructively so far no further precautions are necessary to carry out the method according to the invention. Another embodiment may be a separate module provided in a panel or control panel, in the same way as a motor protection switch, but with the monitoring and diagnostic features as described above.

The embodiments described here relate to centrifugal pumps, as can be seen from the mechanical-hydraulic pump model. Such pumps may be, for example, industrial pumps, submersible pumps for sewage or water supply and heating circulation pumps. Particularly advantageous is a diagnostic system according to the invention in canned pumps, since through early fault detection, the looping through of the can and thus outlet of the pumped liquid, eg. B. in the living area, preventively prevented. In the application of the invention in Verdrängerpumpenbereich the mechanical-hydraulic pump model must be adjusted according to the different physical relationships. The same applies to the use of other engine types for the electric motor model.

Moreover, according to the invention, means are provided for generating and transmitting at least one error message to a display element arranged on the pump unit or elsewhere, whether in the form of one or more indicator lights or a display with an alphanumeric display. In this case, the transmission can be wireless, for example via infrared or radio but also wired, preferably in digital form.

A simplified method, which does not belong to the invention is based on Fig. 1 shown. In an electric motor model 1, the variable electrical power-determining variables flow, here the voltage V _abc and the current i _abc - The product of these quantities defines the electrical power absorbed by the engine. From this motor model, such as given by the equations (1) to (5) or (6) to (9) or (10) to (14), the torque T _e on the shaft of the motor and the rotational speed ω derivable from the engine, as they result arithmetically on the basis of the engine model. These power-dependent electrical variables of the engine are linked to the determined mechanical delivery height H (differential pressure) in a pump model 2, for example according to equations (16) and (17), the result then being compared with predetermined operating values determined on the basis of defined operating points. If these input variables agree with the specified values, the pump set operates without errors. On the other hand, if the difference is greater than a predetermined amount, then an error signal r is generated which signals a malfunction of the pump.

1. 1. erhöhte Reibung aufgrund mechanischer Defekte,
2. 2. reduzierte Förderung/fehlender Differenzdruck,
3. 3. Defekt im Ansaugbereich/fehlender Förderstrom und
4. 4. Förderausfall.

In the embodiment according to the invention Fig. 2 become the same as at Fig. 1 the input voltage v _abc and the motor current i _{abc are used} as input values for the motor model 1 to determine the torque Te present at the motor shaft and the rotational speed of the shaft co. These derived from the engine model 1 values and the sensory variables of the head H (differential pressure) and the flow Q are mathematically linked together in a mechanical-hydraulic pump model 3, which is further developed eg by the equations (19) to (22). In this case, four error quantities r ₁ to r _{4 are} generated, whereby a fault-free operation is present if they all assume the value zero and thus the operating points in the in the FIGS. 4 to 7 shown in detail surfaces r * ₁ to r * ₄ lie. These areas shown there are defined from a variety of operating points in the proper operation of the pump unit and factory-generated and stored digitally in the memory module of the evaluation electronics. Alternatively or additionally, it is determined whether or not the error variables r ₁ to r ₄ determined on the basis of the mechanical-hydraulic pump model are zero or not, according to this result an evaluation takes place in accordance with the above-described table. Depending on whether an error size is present or not, when an error occurs in total four faulty operating states of the pump set are detected, namely those falling under the above-mentioned preambles:

1. 1. increased friction due to mechanical defects,
2. 2. reduced delivery / missing differential pressure,
3. 3. Defective in the intake / missing flow and
4. 4. Delivery failure.

The equations described above for the mathematical description of pump and motor are to be understood as examples only and can be replaced, if necessary, by other suitable equations, as they are known from the relevant specialist literature. The above with these models detectable error in the operation of a pump set or differentiation by types of errors can be further diversified by appropriate error algorithms.

In order to ensure that even small production tolerances or measurement errors do not lead to the emission of error signals, it is expedient to choose the parameters a _h and at specified in equations (16) and (17) not constant, but in each case to set a lower or upper limit to generate some bandwidth, as in Fig. 3 are shown. In the left-hand curve shown there, the power is plotted against the delivery flow and in the right-hand curve the delivery height (differential pressure) is plotted against the delivery flow.

LIST OF REFERENCE NUMBERS

1. 1 - Electric Engine Model
2. 2 - Simplified pump model
3. 3 - Extended pump model
4. 4 - Hydraulic part of the system

Claims (10)

1. A method for determining faults on operation of a pump assembly, with which at least two electrical variables of the motor which determine the electrical power of the motor, and at least one changing hydraulic variable of the pump, as well as at least one further hydraulic variable which determines the power of the pump are acquired, and on the one hand, the two electrical variables of the motor which determine the electrical power of the motor, are mathematically linked for achieving at least one comparison value, and on the other hand the at least one changing hydraulic variable of the pump, as well as at least one further hydraulic variable determining the power of the pump are mathematically linked for achieving at least one comparison value, wherein a mathematical, electrical motor model (1) is used in combination with a mathematical, mechanical-hydraulic pump model (3) for the mathematical linking, and one determines whether a fault is present or not by way of the results of the mathematical linkings by comparison with predefined values, wherein the input voltage V_abc and the motor current i_abc are used as input values for the motor model (1), in order to determine the moment Te which is present at the motor shaft, characterised in that the rotation speed of the shaft ω is determined from the motor model and these values which are derived from the motor model (1) as well as the variables of the delivery head H, differential pressure as well as the delivery flow Q which are determined by sensor are mathematically linked to one another in the mechanical-hydraulic pump model (3).
2. A method according to claim 1, characterised in that if the presence of a fault is determined, one then further determines as to which fault it is a case of.
3. A method according to one of the preceding claims, characterised in that the electrical motor model (1) is formed by the following equations $${\mathit{Lʹ}}_s\frac{d{i}_{\mathit{sd}}}{dt}=-{\mathit{Rʹ}}_s{i}_{\mathit{sd}}+\frac{L_m}{L_r}\left({\mathit{Rʹ}}_r{\psi }_{\mathit{rd}}+z_p\omega {\psi }_{\mathit{rq}}\right)+v_{\mathit{sd}}$$

   

   $${\mathit{Lʹ}}_s\frac{d{i}_{\mathit{sq}}}{dt}=-{\mathit{Rʹ}}_s{i}_{\mathit{sq}}+\frac{L_m}{L_r}\left({\mathit{Rʹ}}_r{\psi }_{\mathit{rq}}-z_p\omega {\psi }_{\mathit{rd}}\right)+v_{\mathit{sq}}$$

   

   $$\frac{d{\psi }_{\mathit{rd}}}{dt}=-{\mathit{Rʹ}}_r{\psi }_{\mathit{rd}}-z_p\omega {\psi }_{\mathit{rq}}+{\mathit{Rʹ}}_r{L}_m{i}_{\mathit{sd}}$$

   

   $$\frac{d{\psi }_{\mathit{rq}}}{dt}=-{\mathit{Rʹ}}_r{\psi }_{\mathit{rq}}+z_p\omega {\psi }_{\mathit{rd}}+{\mathit{Rʹ}}_r{L}_m{i}_{\mathit{sq}}$$

   

   $$T_e=z_p\frac{3}{2}\frac{L_m}{L_r}\left({\psi }_{\mathit{rd}}{i}_{\mathit{sq}}-{\psi }_{\mathit{rq}}{i}_{\mathit{sd}}\right)$$

   

   
   or $$V_s=Z_s\left(s\right)I_s$$

   

   $$\omega ={\omega }_s-s{\omega }_s$$

   

   $$I_r=\frac{V_s}{Z_r\left(s\right)}$$

   

   $$T_e=\frac{3R_r{I}_r^2}{s}$$

   

   
   or $${\mathit{L}}_s\frac{d{i}_{\mathit{sd}}}{dt}=-{\mathit{R}}_s{i}_{\mathit{sd}}+z_p\omega L_s{\psi }_{\mathit{rq}}+v_{\mathit{sd}}$$

   

   $${\mathit{L}}_s\frac{d{i}_{\mathit{sq}}}{dt}=-{\mathit{R}}_s{i}_{\mathit{sq}}-z_p\omega L_s{\psi }_{\mathit{rd}}+v_{\mathit{sq}}$$

   

   $$\frac{d{\psi }_{\mathit{rd}}}{dt}=-z_p\omega {\psi }_{\mathit{rq}}$$

   

   $$\frac{d{\psi }_{\mathit{rq}}}{dt}=z_p\omega {\psi }_{\mathit{rd}}$$

   

   $$T_e=z_p\frac{3}{2}\left({\psi }_{\mathit{rd}}{i}_{\mathit{sq}}-{\psi }_{\mathit{rq}}{i}_{\mathit{sd}}\right)$$

   

   
   in which is
   i_sd the motor current in direction d
   i_sq the motor current in direction q
   ψ_rd the magnetic flux of the rotor in the d-direction
   ψ_rq the magnetic flux of the rotor in the q-direction
   T_e the motor moment
   v_sd the supply voltage of the motor in the d-direction
   v_sq the supply voltage of the motor in the q-direction
   ω the angular speed of the rotor and impeller
   R'_s the equivalent resistance of the stator winding
   R' _r the equivalent resistance of the rotor winding
   L_m the inductive coupling resistance between the stator and the rotor winding
   L'_s the inductive equivalent resistance of the stator winding
   L_r the inductive resistance of the rotor winding
   Z_p the pole pair number
   I_s the phase current
   V_s the phase voltage
   ω_s the frequency of the supply voltage
   ω the actual rotor and impeller rotational speed
   s the motor slip
   Z_s (s) the stator impedance
   Z_r (s) the rotor impedance
   R_r the equivalent resistance of the rotor winding
   R_s the equivalent resistance of the stator winding
   L_s the inductive resistance of the stator winding
   wherein d and q are two directions perpendicular to the motor shaft and perpendicular to one another
   and that the mechanical-hydraulic pump/motor model is formed by the equation $$J\frac{d\omega }{dt}=T_e-\mathit{B\omega }-T_P$$

   

   
   and at least one of the equations $$H_p=-a_{h2}{Q}^2+a_{h1}\mathit{Q\omega }+a_{h0}{\omega }^2$$

   

   $$T_p=-a_{t2}{Q}^2+a_{t1}\mathit{Q\omega }+a_{t0}{\omega }^2$$

   

   
   in which is
   

   

   the temporal derivative of the angular speed of the rotor,
   T_p the pump torque,
   J the moment of mass inertia of the rotor, impeller and the delivery fluid contained in the impeller,
   B the friction constant,
   Q the delivery flow of the pump,
   H_p the differential pressure produced by the pump,
   a _h2 ,a _h1,a _h0 the parameters which describe the relationship between the rotational speed of the impeller, the delivery flow and the differential pressure and
   a _t2 ,a _t1,a _t0 the parameters which describe the relation between the rotational speed of the impeller, the delivery flow and the moment of mass inertia.
4. A method according to claim 3, characterised in that the variables a_h0-a_h2 and a_t0-a_t2 are fixed in the equations (16) and (17), as well as the variables B and J in the equation (15), that a motor moment (T_e) is determined from the electrical motor model (1) according to the equations (1) - (5) or (6) - (9) or (10) - (14), and the rotational speed is computed according to the equations (1) - (5) or (6) - (9) or (10) - (14), whereupon with the help of the equations (16) and (17), one determines a relationship between differential pressure and delivery flow on the one hand and between the pump moment and delivery flow on the other hand.
5. A method according to claim 3, characterised in that a tolerance band is fixed by way of variance of at least one of the variables a_h0-a_h2 and a_t0-a_t2 and B and J.
6. A method according to one of the preceding claims, characterised in that the determined values are substituted into the equations according to claim 4, in a manner such that several fault variables (r₁ - r₄) result, wherein by way of the combination of fault variables, the type of fault is determined by way of predefined boundary value combinations.
7. A method according to one of the preceding claims, characterised in that the determined values or values derived therefrom are compared to predefined values, wherein the predefined values in each case define a surface, wherein one determines whether the determined variables or those derived therefrom lie on one of these surfaces (r*₁ - r*₄) or not, and by way of the combination of the fault variables, one determines the type of fault by way of predefined boundary value combinations.
8. A method according to one of the preceding claims, characterised in that the evaluation of the fault type is effected by way of the following table: fault type fault variable r ₁, r₂, r ₃, r ₄, comparative surface r ₁* r ₂* r ₃* r ₄* increased friction on account of mechanical defects 1 0 1 1 reduced delivery/ absent differential pressure 0 1 1 1 defect in suction region/ absent delivery flow 1 1 0 1 delivery stoppage 1 1 1 1
9. A method according to one of the preceding claims, characterised in that on determining a fault, the pump assembly is activated with a changed rotational speed, in order by way of the measurement results which then set in, to more accurately specify the determined fault.
10. A method according to one of the preceding claims, characterised in that the variables r₁ - r₄ are defined by the equations $$\{\begin{array}{cc}\hfill J\frac{d{\hat{\omega }}_1}{dt}=& -B{\hat{\omega }}_1-\left(-a_{t2}{Q}^2+a_{t1}\mathit{Q\omega }+a_{t0}{\omega }^2\right)+T_e+k_e\left(\omega -{\hat{\omega }}_1\right)\hfill \\ \hfill r_1=& q_1\left(\omega -{\hat{\omega }}_1\right)\hfill \end{array}$$

    

    $$\{r_2=q_2\left(-a_{h2}{Q}^2+a_{h1}\mathit{\omega Q}+a_{h0}{\omega }^2-H_p\right)$$

    

    $$\{\begin{array}{cc}\hfill \mathit{Qʹ}=& \frac{a_{h1}\omega +\sqrt{a_{h1}^2{\omega }^2-4a_{h2}\left(H_p+a_{h0}{\omega }^2\right)}}{2a_{h2}}\hfill \\ \hfill J\frac{d{\hat{\omega }}_3}{dt}=& -B{\hat{\mathrm{\omega }}}_3-\left(-a_{t2}{\mathit{Qʹ}}^2+a_{t1}\mathrm{Qʹ\omega }+a_{t0}{\mathrm{\omega }}^2\right)+T_e+k_3\left(\mathrm{\omega }-{\hat{\mathrm{\omega }}}_3\right)\hfill \\ \hfill r_3=& q_3\left(\mathrm{\omega }-{\hat{\mathrm{\omega }}}_{\mathrm{3}}\right)\hfill \end{array}$$

    

    $$\{\begin{array}{cc}\hfill \mathit{\omega ʹ}=& \frac{-a_{h1}{H}_p+\sqrt{a_{h1}^2{H_p}^2-4a_{h2}\left(H_p+a_{h0}{Q}^2\right)}}{2a_{h2}}\hfill \\ \hfill J\frac{d{\hat{\omega }}_4}{dt}=& -B{\hat{\mathrm{\omega }}}_4-\left(-a_{t2}{\mathit{Q}}^2+a_{t1}\mathit{Q\omega ʹ}+a_{t0}{\mathit{\omega ʹ}}^2\right)+T_e+k_4\left(\mathit{\omega ʹ}-{\hat{\mathit{\omega }}}_4\right)\hfill \\ \hfill r_4=& q_4\left(\mathit{\omega ʹ}-{\hat{\mathit{\omega }}}_4\right)\hfill \end{array}$$

    

    in which represent
    k₁,k ₃,k ₄ constants,
    q ₁,q _2, q _3, q ₄ constants,
    Q' the computed delivery flow on the basis of current rotational speed and measured differential pressure,
    ω̂ ₁ the computed rotor rotational speed on the basis of the mechanical-hydraulic equations (15) and (17),
    ω̂ ₃ the computed rotor rotational speed on the basis of the equations (15), (16) and (17),
    ω̂ ₄ the computed rotor rotational speed on the basis of the equotations (15), (16) and (17),
    ω' the computed rotor rotational speed on the basis of the measured differential pressure and measured delivery flow
    r ₁ - r ₄ fault variables, and
    r ₁* - r ₄* surfaces determined by three variables, which represent a fault-free operation of the pump.

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