EP2258949B1 - Method for recording characteristic values, in particular values, in particular of parameters of a centrifugal pump powered by an electric motor integrated into an assembly - Google Patents

Description

The use of centrifugal pumps is today the state of the art in almost all technical fields. Centrifugal pumps are typically used in the form of centrifugal pump units, consisting of the actual pump and a mechanically connected electric drive motor.

To operate the centrifugal pump unit on the one hand energetically favorable, on the other hand optimally adapted to the purpose, it already counts today in centrifugal pump units of small design to the state of the art to equip them with a speed controller, typically an electronic frequency converter. Such centrifugal pump units with speed controller are used in systems, be it for example in heating systems, in Fäkalienhebeanlagen, in wastewater systems, in plants for the promotion of groundwater from a well, to name just a few typical applications.

Especially in plants, but not only there, it is important to monitor the function of the plant parts and the process variables on the one hand. Thus, it is known in centrifugal pump units to provide within the pump housing, a pressure sensor, typically a differential pressure sensor which detects the pressure generated by the pump between the suction and discharge side, so the delivery height.

In addition, electrical quantities of the motor, such as the power consumption of the motor and the frequency with which the speed controller feeds the motor, are detected.

In order to determine the hydraulic operating point of the pump, however, the detection of the aforementioned values generally does not suffice since they do not make any statement about the delivery rate. The arrangement of flow monitors for detecting the flow within the pump is complex and often prone to failure. A flow sensor, with which the flow rate and thus the flow rate can be detected, is even more complex and can not be used practically in wastewater technology in particular.

Out GB 2 221 073 A It is part of the state of the art to calculate the delivery rate of the pump indirectly, by typically determining the level, in particular the change over time, of the level via a pressure measurement within the shaft. For this purpose, when the pump is switched off, the average resulting feed rate per unit of time is first determined and then determined with the pump switched on by how much the fill level per unit time decreases, and then under the condition that the same inflow occurs in the time in which the pump is running As in the time when the pump is not running, close to the flow rate. This method is complex, since not only a time measurement is additionally required, but also the change in the level must be detected when the pump is not running. Incidentally, the accuracy of the determined pump flow rates depends on the continuity of the feed.

Out EP 1 072 795 A1 a method is known which determines when a pump located in a plant, whether it is driven in an energetically favorable range. For this purpose, on the one hand the parameters of the pump set are entered, on the other hand, the actual data, ie differential pressure, flow or the like is determined by a Relationship between the theoretical theoretical data entered and the actual actual data. The method essentially serves to determine whether the use of a speed controller makes sense or not.

Out DE 39 18 294 A1 It is state of the art to monitor a sewage pump station on the basis of the pump output values of the sewage pump by comparing the values with previously measured reference values at predefined times.

Based on the state of the art EP 1 072 795 A1 The invention has for its object to provide a method by which the aforementioned disadvantages can be avoided as far as possible and with simple technical means allows detection of the hydraulic variables of the pump during operation.

This object is achieved by a method having the features specified in claim 1. Advantageous embodiments of the invention will become apparent from the dependent claims and the following description and the drawings. Both the features of the subclaims as well as those of the following description, as far as appropriate, can also be used on their own and in combinations other than those described.

The method according to the invention serves to determine characteristic values, that is to say of parameters of an electric motor-driven centrifugal pump assembly with speed controller integrated in a system. These characteristic values are determined on the basis of electrical variables of the motor and / or the speed controller on the one hand and the pressure generated by the pump on the other hand. For this purpose, at least two different operating points of the pump are approached one after the other, wherein the flow rates in the approached operating points are determined on the system side and the characteristic values are thus determined.

After determination of the characteristic values, that is to say the parameters, both the hydraulic operating variables of the pump and also further functions can then be detected or controlled only by using electrical variables of the motor or the speed controller and the pressure generated by the pump. It is provided according to the invention that at least two operating points are approached to set the characteristic values at least with an accuracy that allows meaningful conclusions in later operation. It is understood that when starting from only two operating points, the characteristic values can not necessarily be determined unambiguously. Therefore, according to the invention, at least three, four or nine, thirteen or even more operating points are preferably approached to a sufficient number of characteristic values with sufficient accuracy, in order to be able to largely dispense later on the acquisition of flow rates even on the system side. It is understood that with increasing number of operating points, not only the accuracy of the determined characteristic values, in particular parameters, increases, but also the accuracy of the flow rates to be determined on the system side.

An electromotive-driven centrifugal pump unit in the sense of the invention is an electric motor with a centrifugal pump driven therefrom, which typically has a common shaft. Associated with the unit is a speed controller, typically a frequency converter, which can vary the electrical energy added to the motor at least in terms of frequency, but typically also in terms of voltage in a wide range. The electrical variables of the motor, which are to be detected, inter alia, namely the power consumption and the frequency, can possibly be replaced by corresponding variables of the speed controller. These variables are usually available on the speed controller, so they need not be detected by separate sensors. The pressure generated by the pump can by a differential pressure sensor on the pump, but also by other suitable pressure transducer elsewhere, z. B. be measured at a distance from the pressure outlet of the pump.

Under plant within the meaning of the invention, any involvement of a centrifugal pump unit to understand, for example, a sewage lifting system, a system in which promotes a centrifugal pump unit as a submersible pump from a well, a system in which promotes a centrifugal pump unit in a surge tank, wastewater systems with several centrifugal pump units and the like ,

According to an advantageous development of the method according to the invention, the characteristic values to be determined are parameters which are part of a function following the model laws of motor and / or pump or also functions which are preferably formed in parameter-linear form. The latter makes it possible to determine concrete values on the basis of concrete operating points in a simple manner, without further differential consideration. Since this function or functions follow the model laws of the engine and / or pump, only a few operating points result in a practically usable result when starting up.

Advantageously, a function determining the delivery rate is used, which has at least one first term with a hydraulic and / or electrical performance-dependent variable and a second term with a hydraulic and / or electrical performance-dependent variable, which are each multiplicatively linked to one of the parameters. Specifying such a function as a function of the delivery rate is particularly favorable since the delivery rate in the approached operating points is determined on the installation side and can therefore be used directly for determining the characteristic values. A function determining the flow rate of the above-mentioned type is particularly advantageous if the flow rate, for example in wastewater treatment plants, can not be detected accurately but, for example, only averaged over time. For then this comparatively uncertain value stands on one side of the equation. If necessary, the parameters can then be determined with comparatively high accuracy by repeated starting and also the same operating point, since the accuracy of the applied delivery quantity also increases as the number of approached operating points and detected values increases. This applies in particular on the basis of the parameter-linear equations described below.

According to a development of the invention, a function is particularly advantageously used in which the parameters form part of at least part of a pump model and are linked as follows: $$q={\gamma }_1\frac{p}{{\omega }_r}+{\gamma }_2\frac{T}{{\omega }_r}+{\mathrm{<figure-callout\; id="3"\; label="\gamma "\; filenames="imgf0002.png"\; state="\{\{state\}\}">\gamma </figure-callout>}}_3{\omega }_r$$

In this equation, q is the delivery rate of the pump, p is the delivery pressure of the pump, that is, for example, the differential pressure between suction and pressure side, ω _r the rotational speed of the pump, T the drive torque of the pump and γ ₁ to γ _3, the parameters of the sub-pump model to be determined , To determine these parameters γ ₁ to γ ₃ , at least two operating points are to be approached in order to determine them at least approximately. It is understood that then there is still no clear solution, but due to the fact that the equation (a) represents a part of a pump model, even for some applications can be sufficiently meaningful.

verwendet werden, das gegenüber dem vorbeschriebenen Teilpumpenmodell um den Term ${\gamma }_0\frac{1}{{\omega }_r}$

erweitert ist. Dieser Term ist zur Kompensation eines Affinitätsfehlers bestimmt, der entstehen kann, wenn der Druck p mit Abstand zur Pumpe ermittelt wird, also gegenüber dem tatsächlich von der Pumpe erzeugten Druck abweichend gemessen wird.As an alternative to the aforementioned sub-pump model according to equation (a), the sub-pump model according to equation (b), which is $$q={\gamma }_0\frac{1}{{\omega }_r}+{\gamma }_1\frac{p}{{\omega }_r}+{\gamma }_2\frac{T}{{\omega }_r}+{\mathrm{<figure-callout\; id="3"\; label="\gamma "\; filenames="imgf0002.png"\; state="\{\{state\}\}">\gamma </figure-callout>}}_3{\omega }_r$$

be used, compared to the above-described sub-pump model by the term ${\gamma }_0\frac{1}{{\omega }_r}$

is extended. This term is intended to compensate for an affinity error that can arise when the pressure p is determined at a distance from the pump, that is to say that it is measured differently than the pressure actually generated by the pump.

wobei p den Förderdruck der Pumpe, ω_r die Drehgeschwindigkeit der Pumpe, T das Antriebsdrehmoment der Pumpe und θ₀ bis θ₈ die zu ermittelnden Parameter des Teilpumpenmodells darstellen. Die Gleichungen (a), (b) und (c) stellen jeweils Teile eines Pumpenmodells dar, bilden also zusammen ((a) und (c) bzw. (b) und (c)) ein vollständiges Pumpenmodell, weshalb es besonders vorteilhaft ist, die Parameter beider Gleichungen zu bestimmen, da dann eine vollständige hydraulische Leistungskurve der Pumpe mit hoher Genauigkeit nachgebildet werden kann. Es versteht sich, dass dann eine entsprechend Vielzahl von unterschiedlichen Betriebspunkten anzufahren ist, um die Vielzahl der zu ermittelnden Parameter bestimmen zu können.Alternatively or additionally, according to an advantageous development of the invention, a partial pump model can be used in which the parameters are linked as follows: $$p^2={\theta }_0+{\theta }_{1}p+{\theta }_{2}T+{\mathrm{<figure-callout\; id="3"\; label="\theta "\; filenames="imgf0002.png"\; state="\{\{state\}\}">\theta </figure-callout>}}_3\mathit{pT}+{\theta }_4{T}^2+{\mathrm{<figure-callout\; id="5"\; label="\theta "\; filenames="imgf0005.png"\; state="\{\{state\}\}">\theta </figure-callout>}}_5{\omega }_r^2+{\theta }_{6}p{\omega }_r^2+{\theta }_{7}T{\omega }_r^2+{\theta }_{\mathrm{8th}}{\mathrm{<figure-callout\; id="4"\; label="\omega \; r"\; filenames="imgf0002.png"\; state="\{\{state\}\}">\omega \; </figure-callout>}}_r^{}$$

where p represents the delivery pressure of the pump, ω _r the rotational speed of the pump, T the driving torque of the pump and θ ₀ to θ _{8 represent} the parameters of the sub-pump model to be determined. The equations (a), (b) and (c) each represent parts of a pump model, so together form (a) and (c) or (b) and (c) a complete pump model, which is why it is particularly advantageous To determine the parameters of both equations, since then a complete hydraulic power curve of the pump can be replicated with high accuracy. It goes without saying that then a corresponding multiplicity of different operating points must be approached in order to be able to determine the multiplicity of parameters to be determined.

An advantageous development, in particular simplification of the method according to the invention results from the fact that the determination of the rotational speed of the pump ω _{r is} omitted and this is simplified equated to the frequency ω _{e of} the power supply of the motor. $${\omega }_r={\omega }_e$$

This frequency value ω _e is available in the speed controller and therefore does not need to be determined. The same applies to the determination of the drive torque T of the pump. This can be easily determined by determining that from the quotient of the electric power P _{e received} by the motor and the frequency ω _e the power supply of the motor or the rotational speed of the pump ω _{r is} formed. $$T=\frac{P_e}{{\omega }_e}$$

The electric power P _e picked up by the motor is also available on the speed controller since voltage and current are constantly detected there.

In order to determine the characteristic values in the approached operating points, the method according to the invention at least estimatedly requires the resulting delivery rate q of the pump. According to the invention, when the pump unit is used in a pressure-balanced container, typically a well shaft or the like, it will be determined, at least approximately, by detecting the change over time of the liquid level in the shaft from which the pump is pumping, on the one hand with the pump switched off to detect the inlet, and on the other hand with the pump switched on in the respective operating point. Next, the knowledge of the shaft geometry, ie in particular the size of the shaft cross-section, if necessary, depending on the level height, if the shaft is formed, for example, tapered to assign the height difference of the liquid level corresponding amount of liquid can. The detection of the liquid level can be done in a simple manner by a pressure measurement, so for example by a pressure sensor in the pump, which detects the static pressure when the pump is switched off. Alternatively, the level can also be detected mechanically or the delivery rate of the pump can be detected directly, if this is advantageous.

$$q_{\mathit{in}}=A_w\left({\eta }_0+{\eta }_1{z}_m+{\eta }_2{z}_m^2+\dots +{\eta }_k{z}_m^k\right)$$

in denen

Z_m

der Flüssigkeitsstand im Bohrloch,

Δ _t

ein Zeitabschnitt,

ΔZ _m

die Flüssigkeitsstandsänderung während eines Zeitabschnitts Δt,

q_in

der berechnete Zufluss in das Bohrloch und

A_w

der Querschnitt des Bohrlochs sowie

η _o , ..., η_k

die Parameter eines den Zulauf in das Bohrloch nachbildenden mathematischen Modells sind.

If the system is formed by a borehole with a borehole pump located therein, according to an embodiment of the invention, the flow rate in the respectively approached operating point can be determined on the basis of the temporal change of the liquid level in the borehole. In this case, the liquid level change, which results when the pump is switched off, on the one hand, and with the pump switched on, on the other hand, over a predetermined period of time on the other hand, in order to determine the delivery rate of the pump. Since such boreholes are typically non-linear in inflow, it is advantageous to determine the inflow rate to the borehole using the following equations: $$\frac{\mathrm{\Delta }{z}_m}{\mathrm{\Delta }t}={\eta }_0+{\eta }_1{z}_m+{\eta }_2{z}_m^2+...+{\eta }_k{z}_m^k$$

$$q_{\mathit{in}}=A_w\left({\eta }_0+{\eta }_1{z}_m+{\eta }_2{z}_m^2+...+{\eta }_k{z}_m^k\right)$$

in which

Z _m

the fluid level in the borehole,

Δ _t

a period of time,

ΔZ _m

the liquid level change during a time interval Δt,

q _in

the calculated inflow into the well and

A _w

the cross section of the borehole as well

η _o , ..., η _k

are the parameters of a mathematical model that replicates the feed into the borehole.

Since these equations are also in parameter-linear form, the parameters can be determined by conventional methods, as is well-known in the calculation of the inflow of boreholes per se.

The method according to the invention is formed for applications in which the pump unit conveys into an expansion tank by determining the flow rates at the approached operating points on the basis of the change with time of the pressure in the expansion tank of the plant into which the pump is conveying, taking into account the time change of the tank pressure once when turned on and the other time with the pump off, each over a predetermined period of time.

in der

q_out

der aus der Anlage austretende Förderstrom,

q_pump

die Fördermenge der Pumpe,

p_out

der Druck im Expansionsbehälter,

Δt

ein Zeitabschnitt,

Δp_out

die Druckänderung im Expansionsbehälter während des Zeitabschnitts Δt und

K_e

eine Konstante des Expansionsbehälters sind.

In this case, according to an advantageous embodiment of the method, the delivery rate of the pump is determined using the following equation: $$q_{\mathit{out}}-q_{\mathit{pump}}=-\frac{K_e}{p_{\mathit{out}}^2}\frac{d{p}_{\mathit{out}}}{dt}\approx -\frac{K_e}{p_{\mathit{out}}^2}\frac{\mathrm{\Delta }{p}_{\mathit{out}}}{\mathrm{\Delta }t}$$

in the

q _out

the flow leaving the system,

q _pump

the flow rate of the pump,

p _out

the pressure in the expansion tank,

.delta.t

a period of time,

Δp _out

the pressure change in the expansion tank during the period .DELTA.t and

K _e

are a constant of the expansion tank.

vereinfacht durch den Differenzenquotient $\frac{{\mathrm{\Delta }\mathit{p}}_{\mathit{out}}}{\mathrm{\Delta }\mathit{t}}$

ersetzt worden, was jedoch beim Anfahren einer ausreichenden Menge von Betriebspunkten in der Regel unproblematisch ist.Here is the differential quotient $\frac{{\mathit{dp}}_{\mathit{out}}}{\mathit{dt}}$

simplified by the difference quotient $\frac{{\mathrm{\Delta }\mathit{p}}_{\mathit{out}}}{\mathrm{\Delta }\mathit{t}}$

has been replaced, but this is not a problem when starting a sufficient amount of operating points in the rule.

Advantageously, with the method according to the invention, in particular on the basis of a partial pump model, as indicated in claims 4 and 5 according to equations (a) or (b), the delivery rate can be determined during later operation of the pump, without a flow monitor or a sensor to use for this. It can therefore be advantageous only on the basis of the electrical characteristics such. Power consumption and frequency of the engine and a pressure measurement, the flow rate can be determined. If necessary, other plant sizes can also be determined, for example, the amount of liquid flowing into the well or the system.

According to one embodiment of the method according to the invention, this can also be used to monitor the function of the pump unit by the characteristic values, in particular the parameters are determined again at a time interval and compared with the previously determined. If these values agree with a given tolerance, it can be assumed that the function of the pump set is unchanged. However, if these deviate significantly or significantly from those determined previously, a functional impairment of the pump is to be determined, for example due to the leakage of a seal, due to the increased friction in the event of a defect in a bearing or the like.

If what is provided according to a development of the method according to the invention, not only the characteristic values, in particular parameters of a sub-pump model, but those of a complete pump model at a time interval are determined and compared, typically such, as in claims 4 or 5 and 6 is specified, then it is even possible to monitor the efficiency of the pump unit, so its effectiveness. In this case, for example, the curve of the efficiency as a function of the promotion of the pump is modeled by the pump model, so that when comparing the curves a power loss is visible only in some areas.

The method according to the invention is preferably carried out automatically with the aid of a corresponding control, which can be part of the digital control of a frequency converter, for example, by automatically determining and processing the characteristic values. For this purpose, the pump unit is first operated in an identification mode in which it automatically approaches several hydraulic operating points to determine the characteristic values, in particular parameters and subsequently placed in an operating mode in which the previously determined characteristic values for determining the operating size of the system, in particular the flow rate of the pump unit can be used. If the characteristic values have to be determined again after a certain time to monitor the pump set, the pump set is put back in the identification mode and these values are again determined and then compared with the pre-determined or the originally determined.

Fig. 1

ein Diagramm betreffend die möglichen Anwendungen des erfindungsgemäßen Verfahrens,

Fig. 2

in stark vereinfachter schematischer Darstellung eine Anlage zum Einsatz eines Pumpenaggregates in der Abwassertechnik,

Fig. 3

die zeitliche Flüssigkeitsstandsänderung in der Anlage gemäß Fig. 2 und der daraus ableitbare Förderstrom der Pumpe.

Fig. 4

in Diagrammdarstellung gemäß Fig. 3 eine Erfassung des Förderstroms der Pumpe unter Zugrundelegung von Zeitabschnitten, die kleiner als das jeweilige Förderintervall sind,

Fig. 5

in schematischer Darstellung eine Anlage mit Bohrloch und Pumpenaggregat,

Fig. 6

in schematischer Darstellung eine Anlage, bei der das Pumpenaggregat in einen Ausgleichsbehälter fördert,

Fig. 7

ein Diagramm, welches die Ermittlung der zeitlichen Druckänderungen und deren Auswertung verdeutlicht und

Fig. 8

eine Kurve, welche den Wirkungsgrad in Abhängigkeit der Fördermenge darstellt.

The invention is explained in more detail with reference to the figures. Show it

Fig. 1

a diagram concerning the possible applications of the method according to the invention,

Fig. 2

in a highly simplified schematic representation of a plant for the use of a pump unit in wastewater technology,

Fig. 3

the temporal fluid level change in the system according to Fig. 2 and the derivable from this flow of the pump.

Fig. 4

in diagram representation according to Fig. 3 a detection of the flow rate of the pump on the basis of time periods that are smaller than the respective delivery interval,

Fig. 5

a schematic representation of a system with a borehole and pump unit,

Fig. 6

a schematic representation of a system in which promotes the pump unit in a surge tank,

Fig. 7

a diagram illustrating the determination of the temporal pressure changes and their evaluation and

Fig. 8

a curve showing the efficiency as a function of the flow rate.

Like the diagram according to Fig. 1 illustrates, the pump unit is identified in an identification mode 1, that is, the characteristic sizes of the pump set determined by at least two, but preferably a variety of operating points is approached, in each of the operating points, the electrical power of the engine, the speed of the motor or simplifies the frequency of the supply voltage of the motor and the pump delivered by the delivery pressure is determined. The quantity delivered in each case is determined on the plant side. When this identification mode 1 is completed, after the parameters γ ₁ to γ _{3 of} the equation (a) or the parameters γ ₀ to γ _{3 of} the equation (b) are determined, by using these equations (a) and (b), respectively in the later operating mode 2, the delivery rate of the pump can be determined.

If, on the other hand, the function or the power of the pump set is to be monitored, a constant change between identification mode 1 and operating mode 2 is necessary, as is the case in the left part of FIG Fig. 1 is shown. In the identification mode 1, the parameters are also determined, then the pump unit runs in the operating mode 2 to return to the identification mode 1 after a predetermined time (eg one hour or one week), where the parameters are determined again. A comparison of the now determined parameters with the previously determined parameters allows an assessment in the simplest form of the function of the pump up to the detection of a change in efficiency, as they are based on Fig. 8 is shown. For the latter, the parameter acquisition of equations (a) and (c) or (b) and (c) is required, whereas for pure function monitoring the parameter detection of equations (a) and (b) or (c) is sufficient.

In Fig. 2 a plant is shown, as it is given for example for the promotion of waste water from a shaft. The shaft 3 in Fig. 2 is, as usual in systems of this type, designed as an upwardly open vessel. The liquid level 4 moves in the inlet of liquid q _in upward and with the pump switched on according to the flow rate q _pump down. The pump delivers at the pressure p, which is the differential pressure between suction and discharge side. Although the feed into the shaft 3 is not constant, it is averaged over a time interval Δ t ( q _in ) as quasi-constant. From the change in the liquid level 4 and on the basis of the shaft cross-section 3 then results in an inflow and with decreasing liquid level 4, when the pump is pumping, a flow rate q _out . Since even during the time when the pump is pumping, liquid in the shaft 3 runs, q _in so quasi constant, resulting from the sum of the discharge amount q _out and q _in the flow rate of the pump.

How this can be determined in detail is based on Fig. 3 shown. The diagram shows the level heights in shaft 3 as a function of time t. In the in Fig. 3 first measuring interval 6 is multiplied in the time in which the pump is switched off, the liquid level changing detected 6 over time Δ t and with the shaft cross-section A (h). This results in an inflow amount q _in per unit of time flowing into the shaft 3. In the subsequent interval 7, the pump is turned on and runs at a first operating point until the liquid level 4 again has the original given at the beginning of the interval 6 level. From this, the flow rate q _{pump of} the pump can then be determined. This can in a subsequent interval 8, 9 carried out in an analogous manner, except that the feed quantity q _in is greater and thus requires the pump in the interval 9 longer to get back to the original level. Thus, two operating points are approached with which, with the aid of equation (a), which represents a partial pump model, the parameters of this equation are at least so far determinable that the method is usefully applicable. Expediently, however, one will approach further operating points here, which may not necessarily occur consecutively but also at intervals in the identification mode 1.

As Fig. 3 clarifies, in the method used there, the inflow into the shaft during the entire time to determine when the pump is turned off. In that regard, that is cheaper on the basis of Fig. 4 illustrated method in which the intervals 10 and 11, are divided into partial time sections Δ t 1 to Δ t 9, wherein the time intervals Δ t can be chosen arbitrarily or randomly, so that there is a certain statistical distribution.

Based on Fig. 5 a system is shown in which the pump unit is designed as a well pump 12, which in a wellbore 13 is arranged. The borehole pump 12 conveys the water collecting in the borehole 13 to the surface. In Fig. 5 Z _{w is} the current water level in the shaft 3, ie the liquid level. Z _g represents the groundwater level, ie the water level which would be reached if not pumped out and Z _f the filter inlet pressure, ie the water level required to penetrate the filter typically formed by sand around the well shaft. The above-described principle of the shaft 3 for determining the pumped liquid of the pump leads only conditionally, ie with greater inaccuracy to the result in this system, since unlike the shaft 3, the feed into the borehole 13 is a function of the liquid level Z _w , ie the higher the liquid level Z _w in the borehole, the lower the inlet. In order to take this into account, equations (f) and (g) have to be used in this appendix to determine q _in , ie the incoming liquid per unit of time. These linear parameterized equations (f) and (g) can be solved in the usual way by parameter identification, as known per se in such systems and therefore not described here in detail.

In the case of Fig. 6 The plant shown promotes the pump 14 in an expansion tank 15, ie in a closed container 15 which is at least partially filled with a compressible gas which is more or less compressed depending on the level, ie, that the pressure within the expansion tank 15 is variable. Since the flow rate here is both outflowing (p _out ) and inflowing (pin) depending on the pressure within the container 15, to determine the flow rate of the pump, the equation (g) is to be used, which determines the flow rate as a function of the pressure p _out in Expansion tank or at the end of the discharge line and the pressure change Δ p _out and a constant K _{e of} the expansion tank considered. Again, it is appropriate, as based on Fig. 4 shown, the time interval 16, For example, while the pump is turned off, and the time interval 17 while the pump is turned on, to divide into a plurality of time intervals Δ t 1 to Δ t 9 and to detect the pressure changes Δ p _out resulting in these time intervals, to thereby to improve the accuracy of the result.

It is understood that in all measurements, as determined by the FIGS. 3, 4 and 7 have been exemplified, these are to be repeated accordingly to detect different operating points and thus to determine the parameters of the sub-pump models formed by the equations (a) and (b) and (c). The more operating points are approached, the more accurate is the subsequent determination of the delivery rate of the pump during operation, ie in the operating mode. However, this is more important for the monitoring of the pump function, in particular the efficiency of the pump.

The Fig. 8 shows by way of example two curves, which are formed by means of the sub-pump models (b) and (c) and which represent the efficiency of the pump η above the delivery rate. The curve 18 has been detected at the beginning of the operation, whereas the curve 19 after a considerable period of operation, so after one or several times has been switched to the operating mode, z. After five months. As the curves illustrate, the efficiency of the pump set has fallen almost over the entire pump delivery range. This can be z. B. indicate a leak within the pump, in which a partial flow is shorted.

LIST OF REFERENCE NUMBERS

1

- identification mode

2

- Operation mode

3

- shaft

4

- Liquid level

6, 7, 8, 9

- intervals in Fig. 3

10, 11

- Intervals in Fig. 4

12

- Borehole pump

13

- borehole

14

- pump

15

expansion tank

16, 17

- Intervals in Fig. 7

18, 19

- curves in Fig. 8

Z _g

Groundwater level

Z _f

Filter input pressure

Z _w

Water level in the well

Claims (13)

1. A method for determining parameters of an electromotorically driven centrifugal pump assembly with a speed controller, said assembly being integrated in an installation, said characteristic values being determined by way of electrical variables of the motor and/or the speed controller and of the pressure produced by the pump (14), with which one successively runs to at least two different operating points of the pump (14), wherein the delivery rates are determined on the installation-side at the run-to operating points, and the parameters are determined with this, characterised in that

   - the delivery rates in the run-to operating points are evaluated by way of the temporal change of the fluid level in at least one bore hole (13), which forms part of the installation and from which the pump (14) delivers, by way of comparison of the fluid level change and the feed quantity or discharge quantity resulting therefrom, with the pump (14) switched off and with the pump (14) switched on, or

   - that the delivery rates in the run-to operating points are determined byway of the temporal change of the fluid level (14) in a shaft (3) of the installation, out of which the pump (14) delivers, and specifically whilst taking into account the temporal change of the fluid level, with the pump (14) switched off and with the pump (14) switched on, as well as the shaft geometry, or

   - that the delivery rates in the run-to operating points are determined by way of the temporal change of the pressure in an expansion container (15) of the installation, into which container the pump (14) delivers, and specifically whilst taking into account the temporal change of the container pressure, with the pump (14) switched off and with the pump (14) switched on.
2. A method according to claim 1, characterised in that the parameters are part of a function following the model laws of the motor and/or pump, preferably of a parameter-linear form.
3. A method according to claim 1 or 2, characterised in that a function determining the delivery rate comprises at least one term with a hydraulic and/or electrical power-dependent variable, and a second term with a hydraulic and/or electrical power-dependent variable, which are in each case are linked to one of the parameters in a multiplicative manner.
4. A method according to one of the preceding claims, characterised in that the parameters form part of at least one part of a pump model and are linked as follows: $$q={\gamma }_1\frac{p}{{\omega }_r}+{\gamma }_2\frac{T}{{\omega }_r}+{\gamma }_3{\omega }_r$$

   

   wherein

   q is the delivery rate of the pump,

   p the delivery pressure of the pump,

   ω_r the rotational speed of the pump,

   T the drive torque of the pump, and

   γ₁ to γ₃ the parameters of the part pump model.
5. A method according to one of the preceding claims, characterised in that the parameters form part of at least one part of a pump model and are linked as follows: $$q={\gamma }_0\frac{1}{{\omega }_r}+{\gamma }_1\frac{p}{{\omega }_r}+{\gamma }_2\frac{T}{{\omega }_r}+{\gamma }_3{\omega }_r$$

   

   wherein

   q is the delivery rate of the pump,

   p the delivery pressure of the pump,

   ω_r the rotational speed of the pump,

   T the drive torque of the pump, and

   γ₀ to γ₃ the parameters of the part pump model.
6. A method according to one of the preceding claims, characterised in that the parameters form part of at least one further part of a pump model and are linked as follows: $$p^2={\theta }_0+{\theta }_{1}p+{\theta }_{2}T+{\theta }_3\mathit{pT}+{\theta }_4{T}^2+{\theta }_5{\omega }_r^2+{\theta }_{6}p{\omega }_r^2+{\theta }_{7}T{\omega }_r^2+{\theta }_8{\omega }_r^4$$

   

   wherein

   p is the delivery pressure of the pump,

   ω_r the rotation speed of the pump,

   T the drive torque of the pump, and

   θ₀ to θ₈ the parameters of the part pump model.
7. A method according to claim 4, 5 or 6, characterised in that $${\omega }_r={\omega }_e$$

   

   and $$T=\frac{P_e}{{\omega }_e}$$

   

   are substituted,
   wherein ω_e is the frequency of the voltage supply of the motor and P_e is the electrical power taken up by the motor.
8. A method according to one of the preceding claims, characterised in that the feed quantity to the bore hole is determined whilst using the following equations: $$\frac{\mathrm{\Delta }{z}_m}{\mathrm{\Delta }t}={\eta }_0+{\eta }_1{z}_m+{\eta }_2{z}_m^2+\dots +{\eta }_k{z}_m^k$$

   

   $$q_{\mathit{in}}=A_w\left({\eta }_0+{\eta }_1{z}_m+{\eta }_2{z}_m^2+\dots +{\eta }_k{z}_m^k\right)$$

   

   in which

   Z_m is the fluid level in the bore hole,

   Δt a time interval,

   Δz_m the fluid level change during a time interval Δt,

   q_in the computed feed into the bore hole,

   A_w the cross section of the bore hole, and

   η₀, ..., η_k the parameters of a mathematic model imitating the feed into the bore hole.
9. A method according to one of the preceding claims, characterised in that the delivery rate of the pump is determined whilst using the following equation $$q_{\mathit{out}}-q_{\mathit{pump}}=-\frac{K_e}{p_{\mathit{out}}^2}\frac{d{p}_{\mathit{out}}}{dt}\approx -\frac{K_e}{p_{\mathit{out}}^2}\frac{\mathrm{\Delta }{p}_{\mathit{out}}}{\mathrm{\Delta }t}$$

   

   in which

   q_out is the delivery flow exiting from the installation,

   q_pump the delivery rate of the pump,

   p_out the pressure in the expansion container,

   Δt a time interval,

   Δp_out the pressure change in the expansion container during the time interval Δt, and

   K_e a constant of the expansion container.
10. A method according to one of the preceding claims, characterised in that the part of the pump model according to claim 4 or 5 is used for determining the delivery rate of the pump during the operation.
11. A method according to one of the preceding claims, characterised in that the parameters are determined afresh at a temporal interval and are compared to the previously determined ones for monitoring the function of the pump assembly.
12. A method according to one of the preceding claims, characterised in that the hydraulic power of the pump is determined with the pump model according to claim 4 or 5 and claim 6, and with which this is determined afresh at a temporal interval and this is compared to the previously determined ones for monitoring the power performance of the pump.
13. A method according to one of the preceding claims, characterised in that the characteristic values are preferably detected automatically in an identification mode, and subsequently, the previously determined characteristic values are applied for determining the operating variables of the installation, in particular of the pump assembly, in an operating mode.

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