EP2039939B2 - Method for monitoring an energy conversion device - Google Patents

Description

The invention relates to a method for monitoring an energy conversion device which consists of a plurality of functionally linked functional units. Such energy conversion devices within the meaning of the invention can be, for example, centrifugal pump units driven by an electric motor, compressors driven by an electric motor, systems equipped with them, or the like. They consist of several functionally linked functional units, such as electric motor and centrifugal pump or electric motor and displacement pump or combustion engine and electric generator. Such energy conversion devices are used nowadays in almost all technical, but also domestic, areas.

In the course of dwindling resources, efforts are always made to build machines, systems or other energy conversion devices in such a way that they work with the highest possible efficiency over a long period of time, but in practice the problem often arises that the initially high efficiencies decrease and the Facility continues to operate, although it no longer has the desired efficiency. This phenomenon can be observed, for example, in heating circulation pumps or in refrigerators. A replacement typically only takes place if a defect is obvious or the device completely fails to perform as intended.

In many such cases, however, it would make economic sense to replace the device beforehand or at least to replace or repair the defective or poorly functioning functional unit.

Out DE-A-10 2007 009 301 A generic method for a pump from the prior art already counts, in which the flow value is determined by a controller during operation of the pump on the basis of the speed and on the basis of values previously stored in a table and compared with a flow threshold value, but the monitoring described there is used for determining dangerous operating conditions and not for monitoring the efficiency.

Out EP-A-1 564 411 with all the features of the preamble of claim 1 counts a method comparable to the prior art with which the proper operation of the pump is monitored.

Against this background, the invention is based on the object of improving a generic method for monitoring an energy conversion device that consists of several functionally linked functional units, in particular to the effect that not only a fault condition but also a deterioration in efficiency can be detected. Furthermore, corresponding energy conversion devices are to be designed for carrying out the method according to the invention.

The procedural part of this object is achieved by the features specified in claim 1. Units and a system for carrying out the method according to the invention are specified in claims 8 to 13, advantageous configurations in the subclaims.

The solution according to the invention provides a method for monitoring an energy conversion device with the features specified in claim 1. Advantageously, according to the invention, not just one, but all functional units, which essentially determine the efficiency of the device, are expediently monitored in the manner described above. By monitoring the performance and corresponding signal processing, an energy conversion device, in particular an assembly, a machine or a system, can determine and display its individual performance characteristics, the resulting operating behavior, life expectancy and the like in a self-learning manner.

Performance-dependent variables in the context of the present invention are those which are in any way related to the performance characteristics of a functional unit. For example, in the case of units that operate discontinuously, such as the compressor of a refrigerator, the timing of the switching on and off processes can also be a performance-dependent variable in the sense of the present invention.

Advantageous refinements of the method according to the invention and devices operating according to the method according to the invention are specified in the further claims and the following description and drawing.

The inventive efficiency monitoring of the device or at least individual functional units of the device can be carried out comparatively easily if the functional units always run at the same operating point, since one measured value is then typically sufficient to determine the intended or decreased performance / efficiency of the respective unit. However, this is more complicated when an energy conversion device such as a heating circulation pump is to be monitored. Such units typically consist of the functional units motor and centrifugal pump, the centrifugal pump typically constantly changing its operating point, since the pipe network resistance of the heating system changes due to external influences. In order to have comparable performance-dependent variables here, it is useful to use an electrical-mechanical motor model and to use of a mechanical-hydraulic pump model to be used at the interface between motor and pump in order to determine the performance level of the pump unit. The determination can take place in that two hydraulic parameters of the pump, typically the delivery rate and the delivery head, are determined and equated with the mechanical power output by the motor using a corresponding model calculation.

According to the invention, in devices of this type in which the operating points change constantly and it can therefore be assumed that the same operating point will in all likelihood not be reached again when measurements are performed at intervals, several measurements are carried out at short intervals and, based on the operating points determined in this way, performance-dependent, determined multidimensional surface courses at the interfaces of the functional units to each other and compared with previously determined. In this case, these computationally determined areas are advantageously approximated using a Kalman filter, so that the respective performance-determining area can be determined with sufficient accuracy with comparatively few measurements. The distance between such areas determined at a longer time interval at a specific operating point or the volume spanned between the areas can then be used as a measure of the change in efficiency, typically the decrease in efficiency.

The method according to the invention is advantageously carried out during normal operation of the device, that is to say in the case of a pump unit during the intended pumping operation, whereby the time interval for recording the quasi-simultaneous operating points for determining the surface profile can be in the range of minutes, for example, whereas the time interval after which a comparison measurement is carried out, can be in the daily, weekly or monthly range, depending on the device type. Comparatively long intervals are z. B. result in heating circulation pumps, whereas short intervals can be useful for compressors, especially for cooling systems, since with such a monitoring method not only a deterioration in efficiency, but also a possible failure of the device can be detected.

The time interval at which the performance-dependent variables to be compared are determined depends on both the machine type and the intended use. However, the comparison is expediently carried out on the basis of the previously recorded variables or predetermined values, the latter method having the advantage that a bad function can already be detected when it is started up.

The method according to the invention can be carried out with significantly less effort in terms of measurement and computation if first an electrical variable of the motor that determines the power consumption of the motor and at least one variable that determines the hydraulic operating point of the pump are recorded and stored and the subsequent comparison measurement is waited for so long, until the previously recorded hydraulic operating point is reached again and the engine's power consumption parameters are then recorded and compared with those initially stored. A direct comparison can then be made without the need to determine operating point deviations and thus the aforementioned surface profiles.

The variables recorded later for comparison measurement can be recorded at any operating point of the system if the recorded variables are transferred on the basis of a mathematical, electrical motor model and / or a mathematical hydraulic pump model, i.e. are converted to variables that are independent of the operating point and then compared with the stored variables or vice versa, so that regardless of the operating point a comparison of the performance-determining parameters is possible.

According to the invention, the method is advantageously used only after a predetermined time has elapsed, this predetermined time corresponding at least to the running-in time of the unit, in particular the pump unit. This makes sense so that the mechanical parts of the unit adjust themselves, any resistance to running-in in the bearings can be overcome and then, after the running-in period, an initially quasi-steady operating state can be achieved, which forms a basis for the normal performance-determining properties of the device, so that only deviations later detected by this state.

It is particularly advantageous if at least one operating profile is automatically recorded after the predetermined time, typically the run-in time, and the expected energy consumption is determined taking into account the possibly determined change in efficiency and displayed by suitable means. With this method, it is possible to automatically determine after the running-in period whether the unit fulfills the values specified in terms of power / efficiency or which additional changes in energy consumption can be expected due to a deterioration in efficiency.

According to the method according to the invention, it is not necessary for a comparison measurement to approach the same operating point. Rather, on the basis of several operating points, a multi-dimensional model character, which is dependent on the performance of a functional unit, is determined and stored, and such a surface profile is determined and stored again at time intervals and compared with the previously determined one, the distance between the surface profiles then being a predetermined one Operating point or operating range or the volume spanned between the surface courses can be used as a measure of the change in efficiency. Such an evaluation is particularly advantageous because it can take place during continuous operation without any intervention in the operating behavior of the machine. Such a method is particularly advantageous in the case of centrifugal pump assemblies, such as those used, for example, as heating circulation pumps, which usually run at constantly changing operating points. A Kalman filter is advantageously used to determine the surface profile on the basis of the operating points. This iteration method makes it possible, with only a comparatively small number of measured operating points, to determine the surface profile with sufficient accuracy in order to be able to detect and quantitatively determine the deviations in question here.

The method according to the invention can in principle be used for monitoring with any energy conversion devices which consist of several functionally linked functional units. It is particularly advantageous to use centrifugal pump units, compressors, heating systems, refrigerators, freezers and the like, which are typically operated for years and decades without any deterioration in efficiency or failure. The monitoring method according to the invention is suitable both for detecting and indicating a bad run, i.e. a deterioration in efficiency, which makes premature replacement of the unit or at least one functional unit of the unit appear economically sensible, as well as, for example, of particular advantage in the case of freezers or freezers to be able to display the expected failure of the unit so that a replacement can be provided in good time. The method according to the invention can also be used effectively in the case of larger machines, the downtime of which has economic consequences, in order to indicate an impending failure in good time. It goes without saying that appropriate characteristic values are then expediently specified, which were previously determined in the laboratory test, so that the downtime can at least roughly be determined based on the change in efficiency or the change in performance of the machine.

The method according to the invention can advantageously be implemented in the form of a software program in the digital control and regulation electronics which are already present in modern units. In the case of pump units and compressors, such control and regulating electronics can be provided both in the unit itself and in the terminal or connection box of the unit.

The method according to the invention is advantageously used in a centrifugal pump unit with an electric motor and a centrifugal pump driven by it in a device provided there for monitoring the performance characteristics of at least one functional unit of the unit. In the case of a compressor unit with an electric motor and a displacement pump driven by it, such a device operating according to the method according to the invention can be provided for monitoring the performance characteristics, in particular for recording and monitoring efficiency. Advantageously, a cooling unit can be provided with an electric motor, with a displacement pump driven by it, with an evaporator and with a condenser with a device for monitoring the performance characteristics that works according to the method according to the invention, the monitoring of the performance characteristics not only affecting the engine and Limited displacement pump, but advantageously includes evaporator and condenser.

In the case of refrigerators in particular, a reduction in efficiency can be determined by monitoring the running time of the compressor after the installation of the device. This can be done, for example, in that the running time is determined within 24 hours and then later, for example after six months, is compared with the resulting running time within 24 hours. In its simplest form, it can be assumed that, due to constant environmental conditions and user behavior, an increasing number of Duty cycle is caused by a deterioration in the efficiency of the system. More precise conclusions can be drawn from an analysis of the compressor running time over time.

In an analogous manner, a device for monitoring the performance characteristics of the burner and at least one water circuit that can be heated by this can be provided in a heating system in order to be able to detect, for example, combustion residues on the primary heat exchanger and the associated deterioration in efficiency. By attaching a corresponding signal lamp, an indication of the required cleaning service can be given, which can thus be determined as required.

The device is expediently designed in such a way that it starts automatically after a predetermined time after commissioning the unit or the system with the acquisition and storage of the parameters relevant for monitoring the performance characteristics, in particular for determining and monitoring the efficiency, and at appropriate time intervals these parameters again recorded and compared with the pre-stored and / or the originally stored quantities and possibly indicates an impermissibly high deviation. According to a further development of the invention, the device therefore advantageously has a measured value memory in which at least the variables recorded at the beginning of the measurement or variables derived therefrom are stored.

With the method according to the invention, the machine is expediently monitored in its entirety if possible. However, it can also be sufficient to monitor only one functional unit of the machine. This will be particularly useful if the machine has a functional unit that typically fails significantly before all other functional units due to wear and tear or in some other way.

It is particularly advantageous if several or preferably all functional units of an energy conversion device, i.e. a machine, a unit or a system, are recorded in order to be able to assign them to one or more functional units in a targeted manner in the event of a deterioration in efficiency, in order to then specifically only this functional unit or functional units to be repaired or replaced. This will make economic sense, especially for larger machines.

Fig. 1

anhand eines Schaubilds das grundlegende Prinzip eines mit Leistungsflächen arbeitenden erfindungsgemäßen Überwachungsverfahrens,

Fig. 2 a

das Überwachungsverfahren nach Fig. 1, dargestellt anhand eines Kreiselpumpenaggregates,

Fig. 2 b

ein alternatives Überwachungsverfahren für eine Kreiselpumpe,

Fig. 2 c

eine weitere Variante eines Überwachungsverfahrens für eine Kreiselpumpe,

Fig. 3

ein Überwachungsverfahren, dargestellt anhand eines Kompressors,

Fig. 4

ein Überwachungsverfahren, dargestellt anhand eines Kühlgeräts und

Fig. 5

ein Überwachungsverfahren, dargestellt anhand einer Heizungsanlage.

The invention is explained in more detail below with reference to the exemplary embodiments shown in the drawing. Show it:

Fig. 1

using a diagram, the basic principle of a monitoring method according to the invention that works with power surfaces,

Fig. 2 a

the monitoring procedure Fig. 1 , shown using a centrifugal pump unit,

Fig. 2 b

an alternative monitoring method for a centrifugal pump,

Fig. 2 c

another variant of a monitoring method for a centrifugal pump,

Fig. 3

a monitoring process, shown using a compressor,

Fig. 4

a monitoring method, presented using a cooling device and

Fig. 5

a monitoring process, presented using a heating system.

In Fig. 1 an energy conversion device consisting of the functional units 1 and 2 is shown as an example for a large number of machines, systems and aggregates. In the exemplary embodiment shown, the functional units 1 and 2 are monitored independently of one another. First of all, the power P ₁ consumed by the functional unit 1 is a function of one or more variables x ₁ recorded and saved as in Fig. 1 shown with 3. The variables x ₁ are through u ₁ and y ₁ , so that the area shown in FIG. 3 corresponds to the energy balance of the functional unit 1 at the input. Accordingly, a power P ₂ is established at the output, which in turn depends on the variables x ₁ is. This area is shown in FIG. The functional units 1 and 2 are functional, e.g. B. connected to each other via a shaft, which is why representation 4 corresponds to representation 5, which shows the power P ₂ here as a function of x _{2 defined} according to the energy balance at the input of the functional unit 2, depending on the variables u ₂ and y ₂ . A power P _{3 occurs} at the output of the functional unit 2, as shown in FIG. 6 and which is dependent on x ₂ is.

The areas marked by hatching in Figures 3 to 6 are determined at the beginning of the method. This can be done in the factory or only after a certain time in operation. This can be done as an initialization process or during operation. In any case, it takes place at a point in time t ₁ which, if several operating points are to be recorded, can also represent a time range. At a time t ₂ becomes then in the same way an energy balance is created at the input of the functional unit 1, at the output of the functional unit 1, at the input of the functional unit 2 and at the output of the functional unit 2. The corresponding representations are marked 3 ', 4', 5 'and 6'. By comparing these sizes or areas determined at time t ₂ , which can also be a time range, with the sizes or areas determined and stored at time t _1, reductions in the efficiency of individual functional units 1, 2 can be recorded, the distance between the hatched areas in FIG and 3 'or 4 and 4' or 5 and 5 'or 6 and 6' are determined at a predetermined operating point or the volume spanned between these surfaces is determined and a signal is generated when a predetermined value is exceeded, which the user can recognize indicates that there has been a deterioration in efficiency in the machine, which makes an exchange or a repair or an imminent exchange or an imminent repair appear appropriate. Different signals can be generated here by grading the values, for example a first warning signal which indicates a reduced efficiency above a certain value and a second warning signal which indicates such a reduction in efficiency that requires replacement or repair. Since the functional units 1 and 2 are monitored separately from one another, it can also be determined which of the functional units is wholly or partially responsible for the reduction in efficiency.

• Variable:
  • q ∼ Volumenstrom durch die Pumpe [m³/h]
  • Δp ∼ von der Pumpe aufgebauter Differenzdruck [bar]
  • ω _r ∼ Geschwindigkeit der die Pumpe antreibenden Welle [U/sec]
  • T_e ∼ Drehmoment der Welle [Nm]
  • V ∼ Versorgungsspannung [V]
  • I ∼ Versorgungsstrom [A]
  • φ ∼ Winkel zwischen der Versorgungsspannung V und dem Motorstrom I [U]
  • ω _e ∼ Versorgungsfrequenz [U/sec]
  • P ₁ ∼ dem Motor zugeführte elektrische Leistung [W]
  • P ₂ ∼ mechanische Leistung an der Motorwelle [W]. Die Leistung P₂ ist proportional zum Schlupf s des Motors. Dies ist P₂ ∞ s.
  • P₃ ∼ hydraulische Leistung der Pumpe [W]
  • ηm ∼ Motorwirkungsgrad
  • ηp ∼ Pumpenwirkungsgrad

How this can look in a specific application can be seen, for example, using Fig. 2a , b and c shown. A device consisting of an electric motor 1 a and a pump 2 a, which feeds a consumer 7, is shown there. The electrical power consumed by the motor 1a is indicated by P ₁ . The motor converts the electrical power into a torque T _e at a speed ω _r . This present at the output of the engine 1 a mechanical power P ₂ is at the same time present at the input of the pump 2a mechanical power P _2, which is converted within the pump in a hydraulic power P _3, by the by the pump between the suction and pressure side generated pressure difference Δp and the volume flow through the pump q is determined. In order to use Fig. 2a To completely monitor the device consisting of motor 1a and pump 2a, it is expedient to determine areas at the respective interfaces which comprise the performance of the respective functional unit at every possible operating point, namely at the input and output of the same.
The formulaic relationship is as follows:

• Variable:
  • q ∼ volume flow through the pump [m ³ / h]
  • Δp ∼ differential pressure built up by the pump [bar]
  • ω _r ∼ speed of the shaft driving the pump [rev / sec]
  • T _e ∼ torque of the shaft [Nm]
  • V ∼ supply voltage [V]
  • I ∼ supply current [A]
  • φ ∼ angle between the supply voltage V and the motor current I [U]
  • ω _e ∼ supply frequency [U / sec]
  • P ₁ ∼ electrical power supplied to the motor [W]
  • P ₂ ∼ mechanical power on the motor shaft [W]. The power P ₂ is proportional to the slip s of the motor. This is P ₂ ∞ s .
  • P ₃ ∼ hydraulic power of the pump [W]
  • ηm ∼ motor efficiency
  • ηp ∼ pump efficiency

$$P_1=V/\cos \left(\phi \right)$$

$$P_2={\omega }_r{T}_e$$

$$P_3=\mathrm{\kappa }\mathit{q\Delta p}$$

$${\eta }_m=\frac{P_2}{P_1}$$

$${\eta }_p=\frac{P_3}{P_2}$$

These variables are linked as follows: $$s=\frac{{\omega }_e-{\omega }_r}{{\omega }_e}$$

$${\mathrm{<figure-callout\; id="1"\; label="P"\; filenames="imgf0001.png,imgf0004.png"\; state="\{\{state\}\}">P</figure-callout>}}_1=V/\mathrm{<figure-callout\; id="2"\; label="cos\; \phi \; P"\; filenames="imgf0001.png,imgf0003.png"\; state="\{\{state\}\}">cos</figure-callout>}\left(\phi \right)$$

$$P_{}$$$${}_2={\omega }_r{T}_{\mathrm{<figure-callout\; id="3"\; label="e\; P"\; filenames="imgf0001.png"\; state="\{\{state\}\}">e\; </figure-callout>}}$$

$$P_{}$$$${}_3=\mathrm{\kappa }\mathit{q\Delta p}$$

$${\eta }_m=\frac{P_2}{{\mathrm{<figure-callout\; id="1"\; label="P"\; filenames="imgf0001.png,imgf0004.png"\; state="\{\{state\}\}">P</figure-callout>}}_1}$$

$${\eta }_p=\frac{P_3}{{\mathrm{<figure-callout\; id="2"\; label="P"\; filenames="imgf0001.png,imgf0003.png"\; state="\{\{state\}\}">P</figure-callout>}}_2}$$

(Gleichung 8)
wobei vorausgesetzt wird, dass die Versorgungsspannung durch denThe mathematical description of the area that defines the performance of the engine at all operating points as shown in Figure 8 results from the following equation: $${\mathrm{<figure-callout\; id="1"\; label="P"\; filenames="imgf0001.png,imgf0004.png"\; state="\{\{state\}\}">P</figure-callout>}}_1\left({\omega }_e,s\right)=v_s•{\left[{\mathit{IR}}_s+{\mathit{J\omega }}_e\left({\mathrm{L.}}_{\mathit{ls}}+{\mathrm{L.}}_m\right)-{\mathit{J\omega }}_e{\mathrm{L.}}_m{\left(\frac{{\mathrm{R.}}_r}{s}+{\mathit{J\omega }}_e\left({{\mathrm{L.}}_l}_r+{\mathrm{L.}}_m\right)\right)}^{-1}{\mathit{J\omega }}_e{\mathrm{L.}}_m\right]}^{-1}{\nu }_s$$

(Equation 8)
whereby it is assumed that the supply voltage through the

gegeben ist. Rs (Statorwiderstand), L_ls (induktive Verluste des Stators), L_m (magnetische Induktion), L_lr (induktive Verluste des Rotors), R_r (Rotorwiderstand) und $J\left(\mathrm{Matrix}\left[\begin{array}{cc}0& -1\\ 1& 0\end{array}\right]\right)$

sind die Konstanten des Motors.vector $\left[\begin{array}{c}{V}_{\mathit{sd}}\\ V_{\mathit{sq}}\end{array}\right]=\left[\begin{array}{c}{\mathrm{<figure-callout\; id="1"\; label="K"\; filenames="imgf0001.png,imgf0004.png"\; state="\{\{state\}\}">K</figure-callout>}}_1{\omega }_e+{\mathrm{<figure-callout\; id="0"\; label="K"\; filenames="imgf0003.png,imgf0004.png"\; state="\{\{state\}\}">K</figure-callout>}}_0\\ 0\end{array}\right]$

given is. Rs (stator resistance), L _ls (inductive losses of the stator), L _m (magnetic induction), L _lr (inductive losses of the rotor), R _r (rotor resistance) and $J\left(\mathrm{matrix}\left[\begin{array}{cc}0& -1\\ 1& 0\end{array}\right]\right)$

are the constants of the motor.

beschrieben werden, in welcher die Konstanten a_T2, a_T1, a_T0 und B Pumpenkonstanten sind.The power at the input of the pump 2a according to illustration 9 can be known from the pump equation $$P_2\left(q,{\omega }_r\right)=-a_{P2}{\mathrm{<figure-callout\; id="2"\; label="q"\; filenames="imgf0001.png,imgf0003.png"\; state="\{\{state\}\}">q</figure-callout>}}^2{\omega }_r+a_{\mathrm{<figure-callout\; id="2"\; label="P"\; filenames="imgf0001.png,imgf0003.png"\; state="\{\{state\}\}">P</figure-callout>}2}{\mathit{<figure-callout\; id="2"\; label="q\omega \; r"\; filenames="imgf0001.png,imgf0003.png"\; state="\{\{state\}\}">q\omega </figure-callout>}}_r^{}+a_{\mathrm{<figure-callout\; id="0"\; label="P"\; filenames="imgf0003.png,imgf0004.png"\; state="\{\{state\}\}">P</figure-callout>}0}{\mathrm{<figure-callout\; id="3"\; label="\omega \; r"\; filenames="imgf0001.png"\; state="\{\{state\}\}">\omega </figure-callout>}}_r^{}+{\mathit{<figure-callout\; id="2"\; label="B\omega \; r"\; filenames="imgf0001.png,imgf0003.png"\; state="\{\{state\}\}">B\omega </figure-callout>}}_r^{}$$

in which the constants a _T2 , a _T1 , a _T0 and B are pump constants.

The power present at the output of pump 2a according to illustration 10 can be described by the following equation: $$P_3\left(q,{\omega }_r\right)=-a_{p2}{\mathrm{<figure-callout\; id="3"\; label="q"\; filenames="imgf0001.png"\; state="\{\{state\}\}">q</figure-callout>}}^3+a_{p2}{\mathrm{<figure-callout\; id="2"\; label="q"\; filenames="imgf0001.png,imgf0003.png"\; state="\{\{state\}\}">q</figure-callout>}}^2{\omega }_r+a_{\mathrm{<figure-callout\; id="0"\; label="p"\; filenames="imgf0003.png,imgf0004.png"\; state="\{\{state\}\}">p</figure-callout>}0}{\mathit{<figure-callout\; id="2"\; label="q\omega \; r"\; filenames="imgf0001.png,imgf0003.png"\; state="\{\{state\}\}">q\omega </figure-callout>}}_r^{}+p_{\mathit{offset}}q$$

In this equation, the constants are a _p2 , a _p1 , a _p0, and p _offset .

The figures 8, 9 and 10 in Fig. 2a The three-dimensional surfaces shown, which each describe the performance at the interfaces in front of, between and behind the functional units 1 a and 2a, are recorded and stored at a point in time t ₁ . The detection is typically made during normal operation a short period of time which is negligibly small in relation to the monitoring interval (time from T ₁ to t ₂ ), after which this process is repeated after a longer period of time, namely at time t ₂ , so that the areas according to the representations 8 ', 9 'and 10' result. The surfaces 8 and 8 'as well as 9 and 9' and finally 10 and 10 'are compared with one another at time t ₁ and t ₂ . If the surfaces match, the unit works unchanged. If, on the other hand, two of these surfaces are spaced apart from one another at an operating point, then one of the functional units has changed in terms of its performance characteristics, typically deteriorated. If, for example, a distance between the surfaces according to illustration 10 and 10 'and otherwise matching surfaces are determined, then it can be assumed that although the motor 1a operates with undiminished efficiency, a process that changes the efficiency has taken place within the pump 2a . Conversely, if the areas according to the representations 9 and 9 'change, it can be concluded that the pump output characteristics remain the same but the motor efficiency is changed.

When monitoring how they are based on Fig. 2a is shown, a performance monitoring takes place before and after each functional unit 1 a, 2a. However, this may be unnecessary depending on the application. It is also not absolutely necessary to determine the multi-dimensional and model-like surface courses representing the input or output power, as defined by equations 8, 9 and 10, but can, as in the exemplary embodiment according to FIG Figure 2b clarified, e.g. instead of the power P ₃ according to illustration 10 in Fig. 2a alternatively, the hydraulic power characteristic can be determined, i.e. the differential pressure applied by the pump 2a as a function of the drive speed ω _r and the flow rate q. Which is recorded and stored at time t ₁ . The multidimensional area shown in illustration 10a and the area shown at time t ₂ in illustration 10a 'are each defined by the equation. $$\mathrm{\Delta }p\left(q,{\omega }_r\right)=-a_{p2}{\mathrm{<figure-callout\; id="2"\; label="q"\; filenames="imgf0001.png,imgf0003.png"\; state="\{\{state\}\}">q</figure-callout>}}^2+a_{p2}{\mathrm{<figure-callout\; id="1"\; label="q"\; filenames="imgf0001.png,imgf0004.png"\; state="\{\{state\}\}">q</figure-callout>}}^1{\omega }_r+a_{\mathrm{<figure-callout\; id="0"\; label="p"\; filenames="imgf0003.png,imgf0004.png"\; state="\{\{state\}\}">p</figure-callout>}0}{\mathrm{<figure-callout\; id="2"\; label="\omega \; r"\; filenames="imgf0001.png,imgf0003.png"\; state="\{\{state\}\}">\omega </figure-callout>}}_r^{}+p_{\mathit{offset}}$$

Based on Figure 2c a further possibility of monitoring such a pump assembly consisting of the functional units 1a and 2a is shown. As shown in illustration 11, the power P ₁ is recorded there as a function of ω _e and Q according to illustration 8a and is compared with the corresponding output according to illustration 8a 'at a time interval between t ₁ and t ₂ . The power P ₂ is also determined there as a function of Δ _p and ω _r , as the illustration according to FIG. 9a and 9a 'illustrates. Finally, the Figure 2c The monitoring concept shown, the efficiency of the motor η _m and the efficiency of the pump η _p are monitored directly, as the representations 11a and 11b and 11a 'and 11b' illustrate. These differences are only intended to make it clear that there are a large number of options for monitoring the performance characteristics of the entire device but also of the functional units thereof, as has been illustrated above using the centrifugal pump assembly consisting of the functional units motor 1a and pump 2a.

The efficiency of the motor η _m is the quotient of P ₂ and P ₁ and is dependent on ω _e (the supply frequency ) and s , the slip of the motor. The motor efficiency is in Figure 2c in the illustration 11a represented by the area in the diagram at each operating point. In the illustration 9a, the power P _{2 is shown} as a function of Δp and ω _r . This results in the efficiency of the pump η _p as a function of the pump speed ( ω _r ) and the delivery rate q , as the area shown in FIG. 11 b illustrates. In FIG. 8a, the power P _{1 of} the motor 1 a is also shown in the form of an area as a function of the supply frequency and the flow rate of the pump. Analogous to Fig. 1 the powers or efficiencies shown on the basis of areas 8a, 9a, 11a and 11b have been determined and stored at time t ₁ , whereas corresponding comparison areas have been determined at time t ₂ , with the distance between the areas in the as a measure of the change in efficiency Representations 11a and 11a 'and 11b and 11b' can be used. If, for example, the efficiency of the pump 2a decreases in the course of time t ₁ to t ₂ due to bearing damage, the surfaces in the representations 11a and 11a 'will lie one inside the other, whereas the surfaces in the representations 11b and 11b' are a considerable distance apart will have, based on an operating point. Instead of this distance, a volume can also be defined.

• p_in ∼ Eingangsdruck am Kompressor [bar]
• p_out ∼ Ausgangsdruck am Kompressor [bar]
• T_in ∼ Eingangstemperatur am Kompressor [°K]
• T_out ∼ Ausgangstemperatur am Kompressor [°K]
• ω _r ∼ Drehzahl der den Kompressor antreibenden Welle [U/sec]
• P₁ ∼ vom Motor aufgenommene elektrische Leistung [W]
• P ₂ ∼ Leistung an der Antriebswelle [W]. Die Leistung P ₂ ist proportional zum Schlupf des Motors s. Dies ist P ₂ ∞ s.

Based on Fig. 3 shows an example of how a compressor can be monitored using the method according to the invention. The compressor has a functional unit 1b in the form of a motor and a functional unit 2b driven by it in the form of a displacement pump which feeds a consumer 7b. Here, too, an area representing the engine power according to illustration 12 and an area representing the pump output according to illustration 13 are determined and stored at time t ₁ and at a time interval, for example at time t ₂ , according to illustrations 12 'and 13' based on current values determined at time t ₂ and compared with the stored ones, the distance between the surfaces according to the representations 12 and 12 'or 13 and 13' and the volume spanned between them being used as a measure of the deterioration in efficiency. The arithmetic relationships result as follows:

• p _in ∼ inlet pressure at the compressor [bar]
• p _out ∼ outlet pressure at the compressor [bar]
• T _in ∼ inlet temperature at the compressor [° K ]
• T _out ∼ outlet temperature at the compressor [° K ]
• ω _r ∼ speed of the shaft driving the compressor [rev / sec]
• P ₁ ∼ electrical power consumed by the motor [W]
• P ₂ ∼ power on the drive shaft [W]. The power P ₂ is proportional to the slip of the motor s . This is P ₂ ∞ s .

The following mathematical relationships also apply: $$\begin{array}{l}{\mathrm{<figure-callout\; id="2"\; label="P"\; filenames="imgf0001.png,imgf0003.png"\; state="\{\{state\}\}">P</figure-callout>}}_2={\omega }_r{T}_e\\ \frac{n-1}{n}=\frac{\ln \left(T_{\mathit{out}}\right)-\ln \left(T_{\mathit{in}}\right)}{\ln \left(p_{\mathit{out}}\right)-\ln \left(p_{\mathit{in}}\right)}\end{array}$$

wobei k = ΔV/(2π) ist.In the case of an adiabatic compression cycle, the power P ₂ results as follows: $${\mathrm{<figure-callout\; id="2"\; label="P"\; filenames="imgf0001.png,imgf0003.png"\; state="\{\{state\}\}">P</figure-callout>}}_2={\mathrm{<figure-callout\; id="0"\; label="k"\; filenames="imgf0003.png,imgf0004.png"\; state="\{\{state\}\}">k</figure-callout>}}_0{\omega }_r{p}_{\mathit{in}}\ln \left(\frac{p_{\mathit{out}}}{p_{\mathit{in}}}\right)+{\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="imgf0001.png,imgf0004.png"\; state="\{\{state\}\}">k</figure-callout>}}_1{\mathrm{<figure-callout\; id="2"\; label="\omega \; r"\; filenames="imgf0001.png,imgf0003.png"\; state="\{\{state\}\}">\omega </figure-callout>}}_r^{}+{\mathrm{<figure-callout\; id="2"\; label="k"\; filenames="imgf0001.png,imgf0003.png"\; state="\{\{state\}\}">k</figure-callout>}}_2{\mathrm{<figure-callout\; id="3"\; label="\omega \; r"\; filenames="imgf0001.png"\; state="\{\{state\}\}">\omega </figure-callout>}}_r^{}$$

where k = ΔV / (2π) .

wobei k = ΔV n/(n-1) /(2π), wobei n eine Konstante ungleich 1 ist, die den Wärmefluss während der Kompression beschreibt. Wenn der Prozess unter konstanter Temperatur abläuft, kann somit n ebenfalls als konstant angenommen werden. Der Ausdruck n/(n-1) ergibt sich aus folgender Gleichung: $$T_{\mathit{out}}=T_{\mathit{in}}{\left(P_{\mathit{out}}/P_{\mathit{in}}\right)}^{\left(n-1\right)/n}$$

In the event that there is no adiabatic process in the compressor circuit, the performance can be specified as follows: $${\mathrm{<figure-callout\; id="2"\; label="P"\; filenames="imgf0001.png,imgf0003.png"\; state="\{\{state\}\}">P</figure-callout>}}_2={\mathrm{<figure-callout\; id="0"\; label="k"\; filenames="imgf0003.png,imgf0004.png"\; state="\{\{state\}\}">k</figure-callout>}}_0{\omega }_r{p}_{\mathit{in}}\left({\left(\frac{p_{\mathit{out}}}{p_{\mathit{in}}}\right)}^{\frac{n-1}{n}}-1\right)+{\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="imgf0001.png,imgf0004.png"\; state="\{\{state\}\}">k</figure-callout>}}_1{\mathrm{<figure-callout\; id="2"\; label="\omega \; r"\; filenames="imgf0001.png,imgf0003.png"\; state="\{\{state\}\}">\omega </figure-callout>}}_r^{}+{\mathrm{<figure-callout\; id="2"\; label="k"\; filenames="imgf0001.png,imgf0003.png"\; state="\{\{state\}\}">k</figure-callout>}}_2{\mathrm{<figure-callout\; id="3"\; label="\omega \; r"\; filenames="imgf0001.png"\; state="\{\{state\}\}">\omega </figure-callout>}}_r^{},$$

where k = ΔV n / (n-1) / ( 2π ), where n is a constant other than 1 that describes the heat flow during compression. If the process takes place under constant temperature, n can thus also be assumed to be constant. The expression n / ( n -1) results from the following equation: $$T_{\mathit{out}}=T_{\mathit{in}}{\left(P_{\mathit{out}}/P_{\mathit{in}}\right)}^{\left(n-1\right)/n}$$

This means that this expression can be determined from the temperatures T _in and T _out and the pressures P _out and P _in as follows: $$\frac{n-1}{n}=\frac{\ln \left(T_{\mathit{out}}\right)-\ln \left(T_{\mathit{in}}\right)}{\ln \left(p_{\mathit{out}}\right)-\ln \left(p_{\mathit{in}}\right)}$$

The engine power P ₁ can be monitored in a manner analogous to that indicated above by equation (8).

Based on Fig. 4 the inventive method for a refrigerator is shown consisting of a Motor 1c, a displacement pump 2c, the output of which acts on an evaporator 3c, which is connected via a throttle 4c to a capacitor 5c, the output of which is line-connected to the input of the pump 2c. The cold room is marked with 7c.

• T_i ∼ Temperatur am Austritt des Verdampfers 3c
• T_h ∼ Temperatur am Eintritt des Kondensators 5c
• T_box ∼ Temperatur im Kühlraum 7c
• T_amb ∼ Umgebungstemperatur
• Q ₁ ∼ Kühlleistung
• Q ₂ ∼ an die Umgebung abgegebene Leistung
• W ∼ von der Pumpe 2c abgegebene Leistung
• ω_r ∼ Geschwindigkeit der Motorwelle [U/sec]
• T_e ∼ Drehmoment [Nm]
• P ₂ ∼ vom Motor abgegebene mechanische Leistung

The following variables result in this system:

• T _i ∼ temperature at the outlet of the evaporator 3c
• T _h ∼ temperature at the inlet of the condenser 5c
• T _box ∼ temperature in the refrigerator compartment 7c
• T _amb ∼ ambient temperature
• Q ₁ ∼ cooling capacity
• Q ₂ ∼ power emitted to the environment
• W ∼ power delivered by pump 2c
• ω _r ∼ speed of the motor shaft [rev / sec]
• T _e ∼ torque [Nm]
• P ₂ ∼ mechanical power delivered by the motor

These are in the following mathematical context: $$\begin{array}{l}{\mathrm{<figure-callout\; id="2"\; label="P"\; filenames="imgf0001.png,imgf0003.png"\; state="\{\{state\}\}">P</figure-callout>}}_2={\omega }_r{T}_e\\ T_{\mathit{eq}}=\frac{T_H-T_l}{T_l}\cdot \left(T_{\mathit{amb}}-T_{\mathit{box}}\right)\end{array}$$

$$P_3=R_{\mathit{th}}\cdot \frac{T_h-T_l}{T_l}\cdot \left(T_{\mathit{amb}}-T_{\mathit{box}}\right)$$

The area describing the power of the motor 1c according to illustration 14 corresponds to that according to illustration 12 in FIG Fig. 3 or illustration 8 in Fig. 2a The following relationships result for the areas defining power P ₂ and P ₃ : $${\mathrm{<figure-callout\; id="2"\; label="P"\; filenames="imgf0001.png,imgf0003.png"\; state="\{\{state\}\}">P</figure-callout>}}_2={\mathrm{R.}}_{\mathit{th}}\cdot \frac{T_H-T_l}{T_l}\cdot \left(T_{\mathit{amb}}-T_{\mathit{box}}\right)+K_{\omega }\cdot {\omega }^3$$

$${\mathrm{<figure-callout\; id="3"\; label="P"\; filenames="imgf0001.png"\; state="\{\{state\}\}">P</figure-callout>}}_3={\mathrm{R.}}_{\mathit{th}}\cdot \frac{T_H-T_l}{T_l}\cdot \left(T_{\mathit{amb}}-T_{\mathit{box}}\right)$$

Equation 15 describes the power P ₂ at the input of the compressor, whereas equation 17 describes the power at the output of the compressor. As illustrated in particular by illustration 17, the areas to be determined here to determine the power at the interfaces of the functional units can be two-dimensional or multidimensional. The area according to illustration 17 is two-dimensional, that is, a line. The other areas shown here are all three-dimensional. It goes without saying that these surfaces can possibly also be more than three-dimensional, depending on the type of machine to be monitored and the underlying mathematical-physical relationships.

Here, too, the monitoring takes place in an analogous manner, in that the areas indicating the power at the interfaces of the functional units are determined according to representations 14, 15 and 17 at time t ₁ and after a time interval at time t ₂ (the areas then result according to Representations 14 '15' and 17 '), in order to then determine by determining the distance between the surfaces or the volume spanned between them which of the functional units 1c, 2c have decreased in their degree of efficiency.

• q ∼ Volumenstrom des durch die Leitung 22 strömenden Wassers
• ṁ_g ∼ Abgasmasse
• T_w,out ∼ die Temperatur des aus der Leitung 22 austretenden Wassers
• T _w,in ∼ die Temperatur des in die Leitung 22 eintretenden Wassers
• T_g.out ∼ die Temperatur des Abgases am Austritt
• T_g.in ∼ die Verbrennungstemperatur
• T_amb ∼ die Umgebungstemperatur
• P₁ ∼ die durch den Brennstoff in das System eingebrachte Leistung
• P₂ ∼ die durch das Wasser aus dem System abgeführte Leistung

Finally, based on Fig. 5 shows how the monitoring method according to the invention can be applied to the primary circuit of a heating system. The heating system has a burner 20 which heats water in a line 22 in a combustion chamber 21. The water heated by the burner 20 is routed in the primary circuit of the heating system and, after its heat has been dissipated, reaches a heat exchanger 23 in which the exhaust gas exiting the combustion chamber 21 gives off its heat to the water. The exhaust gas exits via outlet 24. The variables of this system are:

• q ∼ volume flow rate of the water flowing through line 22
• ṁ _g ∼ exhaust mass
• T _{w, out} ∼ the temperature of the water emerging from line 22
• T _{w , in} ∼ the temperature of the water entering the line 22
• T _g.out ∼ the temperature of the exhaust gas at the outlet
• T _g.in ∼ the combustion temperature
• T _amb ∼ the ambient temperature
• P ₁ ∼ the power brought into the system by the fuel
• P ₂ ∼ the power removed from the system by the water

in der p_w die Dichte des Wassers und C_pw die spezifische Wärmekapazität des Wassers darstellen. Die zu berechnenden Flächen ergeben sich. hierbei wie folgt und sind zum Zeitpunkt t₁ durch die Darstellung 16 und zum Zeitpunkt t₂ durch die Darstellung 16' angegeben: $$P_2={\bar{P}}_1-{\bar{\dot{m}}}_g{C}_{\mathit{pg}}{T}_{w,\mathit{in}}-{\bar{\dot{m}}}_g{C}_{\mathit{pg}}\left({\bar{T}}_{g,\mathit{in}}-T_{w,\mathit{out}}\right)e^{\frac{\mathit{UA}}{{\bar{\dot{m}}}_g{C}_{\mathit{pg}}}-\frac{\mathit{UA}}{{\mathit{qp}}_w{C}_{\mathit{pw}}}}+{\bar{\dot{m}}}_g{C}_{\mathit{pg}}{\bar{T}}_{\mathit{amb}}$$

wobei C_pg und C_pw die spezifische Wärmekapazität des Abgases, U der Wärmeübertragungskoeffizient und A die Wärmeübertragungsfläche zwischen dem Brenner 20 und der Leitung 22 sind. Dabei werden die durch das Abgas abgeführte Leistung P _in und der Massestrom ṁg des Abgases als konstant angenommen, ebenso die Umgebungstemperatur T _amb . Ggf. können diese Größen auch in einfacher Weise durch Messung ermittelt werden.This results in the following relationships: $${\mathrm{<figure-callout\; id="2"\; label="P"\; filenames="imgf0001.png,imgf0003.png"\; state="\{\{state\}\}">P</figure-callout>}}_2={\rho }_w{\mathit{qC}}_{\mathit{pw}}\left(T_{w,\mathit{out}}-T_{w,\mathit{in}}\right)$$

in which p _{w is} the density of the water and C _{pw is} the specific heat capacity of the water. The areas to be calculated result. here as follows and are indicated at time t ₁ by representation 16 and at time t ₂ by representation 16 ': $${\mathrm{<figure-callout\; id="2"\; label="P"\; filenames="imgf0001.png,imgf0003.png"\; state="\{\{state\}\}">P</figure-callout>}}_2={\bar{P}}_1-{\bar{\dot{m}}}_G{\mathrm{C.}}_{\mathit{pg}}{T}_{w,\mathit{in}}-{\bar{\dot{m}}}_G{\mathrm{C.}}_{\mathit{pg}}\left({\bar{T}}_{G,\mathit{in}}-T_{w,\mathit{out}}\right)e^{\frac{\mathit{UA}}{{\bar{\dot{m}}}_G{\mathrm{C.}}_{\mathit{pg}}}-\frac{\mathit{UA}}{{\mathit{qp}}_w{\mathrm{C.}}_{\mathit{pw}}}}+{\bar{\dot{m}}}_G{\mathrm{C.}}_{\mathit{pg}}{\bar{T}}_{\mathit{amb}}$$

where C _pg and C _{pw are} the specific heat capacity of the exhaust gas, U is the heat transfer coefficient and A is the heat transfer area between the burner 20 and the line 22. Thereby the power dissipated by the exhaust gas P _in and the mass flow ṁ g of the exhaust gas is assumed to be constant, as is the ambient temperature T _amb . Possibly. these variables can also be determined in a simple manner by measurement.

As the above exemplary embodiments make clear, the method according to the invention can be used with a wide variety of devices such as units, machines and systems, with the multidimensional areas being advantageously always determined, which define the performance at the interfaces of the functional units to each other at any operating point and thus a reliable one Measure for the performance characteristics of the functional units as well as with a corresponding evaluation of the entire device result when these are compared with one another at different times (for example t ₁ and t ₂ ). It goes without saying that the times t ₁ and t ₂ are to be understood here only as examples; the values determined at the time t ₁ are expediently always stored in order to be able to compare them with later ones, but this does not rule out that intermediate values are also saved possibly also to record the speed of the change. This can also be evaluated in a corresponding evaluation device. In this regard, in particular EP 1 564 411 A1 referenced where comparable evaluations are described in detail.

It should be pointed out at this point that in the exemplary embodiments shown above, two- or multi-dimensional surfaces have always been used to determine the power balance at the interfaces of the functional units, since this enables an evaluation to be practically independent of the respective operating point. The two-dimensional or multi-dimensional surfaces in question are advantageously determined during operation, with attempts being made by means of suitable iteration methods to achieve a high level of accuracy of the surfaces on the basis of as few different operating points as possible. This can be achieved in particular using the Kámán filter, as has already been described above. However, other suitable iteration methods can also be used. It is also conceivable that, for example in the case of a pump unit, certain operating points are approached in a targeted manner in order to capture the area representing the power balance with the highest possible accuracy or to be able to dispense with determining such areas by specifically approaching defined operating points.

Claims (13)

1. A method for monitoring an energy conversion device which consists of several function units which are functionally linked to one another, concerning which power-dependent variables of at least one function unit are automatically detected and/or computed in temporal intervals and are compared to one another or to values derived therefrom and/or to predefined values, and a corresponding signal is produced in dependence on the comparison, wherein power-dependent variables of at least two function units which are functionally linked to one another are detected and/or computed in an automatic manner in temporal intervals, and the power-dependent output variables or variables derived therefrom, of the one function unit, form the power-dependent input variables of the function unit which is functionally arranged subsequent to this and a multidimensional surface course which has a model character and is dependent on the power of a function unit is determined on the basis of several operating points and stored, characterised in that such surface courses are determined anew in temporal intervals and are compared to the previously determined ones.
2. A method according to claim 1, characterised in that the volume spanned between the surfaces is used as a measure for the efficiency change, in particular an efficiency drop.
3. A method according to claim 1 or 2, characterised in that a Kalman filter is used for determining the surface course on the basis of the operating points.
4. A method according to one of the preceding claims, characterised in that it is used for operational optimisation and/or for monitoring the energy consumption or the efficiency of a pump assembly, in particular of an electromotorically driven centrifugal pump assembly, concerning which on operation, at least one power-dependent variable of the motor and at least one hydraulic variable of the pump or at least two hydraulic variables of the pump, at a temporal interval are compared to one another or are mathematically linked to one another or compared to predefined values, and a signal characterising the operating state of the pump assembly is produced in dependence on the comparison.
5. A method according to claim 4, characterised in that it is carried out during the designated delivery operation.
6. A method according to claim 4 to 5, characterised in that the detection of power-determining variables of the motor and/or pump is not effected until after the completion of a predefined time which corresponds at least to the running-in phase of the pump assembly.
7. A method according to claim 6, characterised in that after completion of the predefined time, during the monitoring phase, automatically at least one operating profile is detected and the expected energy consumption is determined whilst taking into account the efficiency change which is possibly determined
8. A centrifugal pump assembly with an electrical motor and a centrifugal pump driven by this, characterised in that a device for monitoring the power characteristics of at least one function unit of the assembly is provided, said device operating according to a method according to one of the preceding claims.
9. A compressor assembly with an electrical motor and a displacement pump driven by this, characterised in that a device for monitoring the power characteristics of at least one function unit of the assembly is provided, said device operating according to a method according to one of the preceding claims.
10. A cooling assembly with an electric motor, with a displacement pump driven by this, with an evaporator and with a condenser, characterised in that a device for monitoring the power characteristics of at least one function unit of the assembly is provided, said device functioning according to a method according to one of the preceding claims.
11. A heating facility with a combustor and at least one water circuit which can be heated by this, characterised in that a device for monitoring the power characteristics of at least one function unit of the facility is provided, said device operating according to a method according to one of the preceding claims.
12. 1 An assembly or facility according to one of the preceding claims, characterised in that after a predefined time after starting operation of the assembly or facility, the device automatically begins with the detection and storage of the variables which are relevant to determining the efficiency
13. An assembly or facility according to claim 12, characterised in that the device comprises a measured value memory, in which at least the variables detected at the beginning of the measurement or variables derived therefrom are stored.

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