EP2702459A1

EP2702459A1 - Controller for controlling a frequency inverter and control method

Info

Publication number: EP2702459A1
Application number: EP12723626.3A
Authority: EP
Inventors: Wolfgang Leiber; Martin Hoffmann
Original assignee: Allweiler GmbH
Current assignee: Allweiler GmbH
Priority date: 2011-04-29
Filing date: 2012-04-26
Publication date: 2014-03-05
Also published as: CN103608738A; US10359040B2; US20140044561A1; WO2012146663A1; JP6016889B2; JP2014512626A; DE102011050017A1; CN103608738B

Abstract

The invention relates to a controller for controlling a frequency inverter (4) of a positive displacement pump motor (3) of a positive displacement pump (2), said controller comprising a control unit (6) which is designed to produce a control variable (Y_s) for a frequency inverter (4) of a positive displacement pump motor (3) depending on a reference variable (W) and a first actual operating parameter (X). According to the invention, the control unit (6) is associated with logical means (7) having a first threshold value defining means (12) that are designed to determine at least one first threshold value (Y_Grenzmax, Y_Grenzmin) depending on the first actual operating parameter (X) and/or at least one further actual operating parameter (X_H, Y_H, Y_HH) that could lead to a failure state of the positive displacement pump (2) when exceeded or fallen short of.

Description

Control means for controlling a frequency converter

The invention relates to control means according to the preamble of claim 1 for driving a frequency converter of a positive displacement pump motor of a positive displacement pump, in particular a spindle pump, comprising a controller for generating a manipulated variable (manipulated variable signal) for a frequency converter of a positive displacement motor in response to a reference variable (command variable signal) and a first actual operating parameter is formed, wherein the actual operating parameter, as will be explained, preferably measured directly by means of a sensor or calculated on the basis of another actual size, in particular is simulated. Furthermore, the invention relates to a Verdrängerpumpensystem according to claim 15, comprising a positive displacement pump, a Verdrängerpumpenmotor for driving the positive displacement pump, a Verdrängerpumpenmotor associated frequency converter (for controlled or controlled energization of the motor windings) and the frequency converter upstream, formed according to the concept of the invention control means, wherein the Control means are assigned Führungsgrößenvorgabemittel, for example in the form of a process control room. Moreover, the invention relates to a drive method for driving a frequency converter of a positive displacement pump motor of a positive displacement pump according to the preamble of claim 21, wherein a control variable (control signal) for the frequency of the positive displacement motor in response to a command variable and a first actual parameter is generated.

Today's displacement pump motors for driving positive displacement pumps include a frequency converter with integrated controller, which is able to regulate the input signal, in particular a voltage signal for the frequency converter as a function of a measured actual operating parameter and a reference variable to be achieved. The problem with this is that the controller associated with the frequency converter today is designed to be engine-specific, ie, it is not optimized with respect to the actual displacement pump of interest to the positive displacement pump can lead to problems with positive displacement pump systems, as of positive displacement pumps in principle compared to centrifugal pumps increased risk for the pump itself and / or for other process units. This is due to the different flow characteristics of positive displacement pumps. In principle, even in extreme cases, this can lead to complete self-destruction or sustained disruption of the positive-displacement pump, especially if signs of damage are not detected in time.

Also, the influence of the directly resulting from the reference variable (target specification) manipulated variable signal on the quality of the delivery fluid in known positive displacement pumps is not considered.

Based on the above-described prior art, the present invention seeks to provide positive displacement pump-specific control means for providing the manipulated variable for the frequency converter of a positive displacement motor, the control means to minimize the risk to the associated positive displacement pump for itself or other process units and / or optimal Product quality, ie to ensure a good quality of the delivery fluid. Furthermore, the object is to provide a positive displacement pump system with correspondingly improved control means and a drive method for driving a frequency converter of a positive displacement motor, with which the above disadvantages can be avoided. This object is achieved with regard to the control means having the features of claim 1, with regard to the positive displacement pump system having the features of claim 16 and with regard to the actuation method having the features of claim 21. Advantageous developments of the invention are specified in the subclaims. All combinations of at least two features disclosed in the description, the claims and / or the figures fall within the scope of the invention. In order to avoid repetition, features disclosed in accordance with the device should also be regarded as disclosed according to the method and be able to be claimed. Likewise, according to the method disclosed features should be considered as device disclosed and claimed claimable. The invention is based on the idea that the control variable in response to a command variable, for example, a desired volume flow or a desired pressure of the fluid generated control variable, preferably a voltage signal not directly, ie uncritically or without plausibility, ie pass review as an input to the frequency converter, but the Control variable, or later to be explained by possibly additionally provided, in particular second, correction means obtained, corrected control variable or according to a functional relationship from the control variable or the corrected control value determined comparison value with at least a first limit (pump protection limit) to compare, the at least a first limit reflects a potential hazard to the positive displacement pump and / or another process aggregate. In other words, exceeding or falling below the first limit value (with a defined probability) would result in a predetermined defect state of the positive displacement pump. It is essential to the invention that the first limit value is not a static, ie fixed or specified limit value (of course additionally a comparison with such fixed limit values can also be carried out), but a dynamically determined limit value which Basis of actual operating parameters is calculated. In other words, the limit value is actually calculated as a function of actual operating parameters, wherein these actual operating parameters can be the first actual operating parameter, ie an actual controlled variable from the controlled system, on the basis of which the controller determines and corrects the manipulated variable at least one further, ie another actual operating parameter, which is either measured directly by means of a sensor or calculated on the basis of an actual value, in particular simulated. Stated another way, the advantage of the invention is that it not only works with static limit values, but also takes into account according to the invention that the limit values are subject to dynamics, ie can change during operation of the positive displacement pump as a function of changing actual operating parameters. In the event that the thus determined first (pump protection) limit value is exceeded or fallen below by a certain amount, a corrected manipulated variable is provided with the aid of first correction means, with which preferably the manipulated variable generated by the controller or an already previously corrected manipulated variable that was generated, for example, by second correction means, is overwritten. It is particularly expedient if the corrected manipulated variable assumes the maximum or minimum permissible value, that is to say preferably a first, currently calculated limit value in order to come as close as possible to the reference variable or more precisely the manipulated variable directly resulting from the reference variable. In other words, the corrected manipulated variable is a quantity covered by a first limit value (preferably a correspondingly limited voltage signal).

In addition to the comparison of the manipulated variable, a corrected manipulated variable, or a currently determined comparison value with a first limit value ensuring the positive displacement pump protection, the manipulated variable or a corrected manipulated variable determined by the controller as a function of the reference variable, (for example, a corrected manipulated variable obtained by first correction means), In particular, the corrected correcting variable output by the first correcting means or a currently calculated comparative value are compared with at least one second limiting value (conveying fluid protection limit value) whose compliance or not exceeding or undershooting is intended to ensure the quality of the conveying fluid. In other words, exceeding or falling below the second limit value (with a defined probability) would impair a predetermined quality parameter of the fluid delivered by the positive displacement pump. If comparisons are used to determine that the at least one second limit value has exceeded or fallen below by a predetermined amount (depending on whether it is a maximum or minimum limit value), a corrected manipulated variable is output by second correction means, which is preferably either directly or indirectly in the form of a comparison value to the comparison with the at least one first limit value or as an input variable (target specification) is passed to the frequency converter. The manipulated variable generated by the controller or the manipulated variable obtained from upstream further, for example, the first correction means, is preferably overwritten by the corrected manipulated variable of the second correction means.

It is also essential here that the second limit value is not a fixed, stored limit value, but rather a second limit value calculated on the basis of current actual operating parameters, with the actual operating parameters used in the calculation being the first actual Operating parameter, in particular an actual control variable is and additionally to another (further) measured actual operating parameter or an, in particular based on an actual value calculated actual operating parameters. Of course, in addition a comparison of a manipulated variable, a corrected manipulated variable, a comparison value and / or an actual operating parameter can be carried out with a fixed Förderfluid- limit and in case of exceeding or falling below a correction of the manipulated variable or the corrected manipulated variable can be performed.

As already indicated, it is within the scope of the invention to adjust a manipulated variable, a corrected manipulated variable or a comparison value either against at least one first (pump protection) limit value or only against a second (conveying fluid protection) limit value or alternatively against both at least one first (pump protection) limit value. ) Limit value and additionally against at least a second (Förderfluidschutz-) limit value, which in turn alternatively first against at least a first threshold and then subsequently against at least a second threshold can be compared, or conversely first against a second threshold and subsequently against a first threshold.

The core of the invention is therefore to assign the controller for generating a manipulated variable logic (logic means), which ensures that the controller output signal (manipulated variable) first with at least a first and / or at least a second limit (pump protection limit and / or Förderfluidschutz limit ), wherein the at least one first and the at least one second limit currently, ie is calculated taking into account measured or calculated actual operating parameters and that, in the event that an above or below the at least one first limit value and / or the at least one second limit value is determined, generates a corrected manipulated variable and then this instead of the Controller originally generated manipulated variable or instead of an already previously corrected manipulated variable as an input signal to the frequency converter (frequency converter) is passed, which energizes the positive displacement motor based on this target specification.

In principle, it is possible to execute the logic means in hardware separately from the controller, for example in the form of a microcontroller separate from the controller. Preferred is an embodiment in which the controller and the control means are realized by a common microcontroller or comprise a common microcontroller. As will be explained later, it is particularly preferred if in the calculation of the at least one first limit value and / or the at least one second limit value positive displacement pump-specific parameters, in particular geometry parameters, such as a gap, and / or a spindle diameter are included. For this purpose, it is particularly useful if in a (non-volatile) memory, in particular an EEPROM, the logic means several sets of system parameters are stored, which are specific for different positive displacement pumps (ie each record is specific to a positive displacement pump), in particular for different types and Sizes of positive displacement pumps and which can be selected between these data sets, in particular in a basic configuration, for example via a menu control. In this way it is possible to use the same control means in connection with different positive displacement pumps.

Trained according to the concept of the invention control means allow for the first time possible negative effects at current, changing operating parameters of a reference variable or the effects of a directly resulting from the reference variable manipulated variable on the integrity of the positive displacement pump and / or product quality, ie the quality of the agent the promotion pump funded delivery fluid on the basis of a comparison with a situativ determined, ie to change over time limit and counteract if necessary by recognizing a potential hazard as previously resulting directly from the reference variable, generated by the controller manipulated variable (voltage signal) directly from Frequency converter is converted into a Verdrängerpumpenmotordrehzahl or the positive displacement motor is simply turned off by driving a contactor, but instead by a, in particular reduced, od he increased depending on a first operating parameter and another, preferably measured, actual operating parameter calculated corrected manipulated variable (preferably greater than zero) is passed to the frequency converter. Preferably, the corrected manipulated variable is that of the common or alternative provided first and second Grenzwertevorgabemitteln calculated first and second threshold.

The physical quantities (parameters) of the pump speed, the delivery fluid viscosity and the delivery fluid pressure are in the following physical relationship, i. are mutually interdependent:

n being

n = pump speed;

p = conveying fluid pressure in pressure line or conveying fluid pressure difference at the pump Exponent a, factor b and c Constants of the positive displacement pump

k: Factor of conveying fluid lubricity

V: Delivery Fluid Viscosity According to a preferred embodiment, it is provided that the control means take into account all the above parameters for controlling the frequency converter, wherein preferably the pump speed is taken into account in the form of the manipulated variable, the delivery fluid pressure, preferably measured at or in the vicinity of the pressure port or alternatively from other parameters calculated as the first actual operating parameter and the conveying fluid viscosity or a parameter, in particular a fluid parameter to which the conveying fluid viscosity is physically related, in particular the conveying fluid temperature as the second operating parameter, the aforementioned first actual operating parameter, ie the conveying fluid pressure and the further actual Operating parameters preferably the delivery fluid viscosity or the delivery fluid temperature by means of the first limit value setting means are taken into account in order to calculate the first limit, the Üb falling short of or could cause a defect state of the positive displacement pump. The comparison means then compare the control variable output by the controller, ie a speed signal with the first limit value, wherein first correcting means output a corrected manipulated variable, ie a corrected speed signal in the event that the manipulated variable output by the controller, taking into account the conveying fluid pressure and the conveying fluid viscosity or of a parameter related thereto in a functional context is below, wherein it is the corrected manipulated variable, ie the corrected speed signal is preferably the first, previously calculated using the first threshold value setting means limit value. In the preferred embodiment, a delivery fluid volume flow (or the pump speed reflecting the delivery volume flow) or a delivery fluid pressure are used as reference variables.

This preferred embodiment does justice to the case that frequently occurs in practice that a rapid change in the disturbance, e.g. a sudden flow resistance change leads to a very rapid change in pressure and thus to a rapid change in the torque requirement at the pump. In the case of a rapid pressure reduction for large pump drives, this would lead to a rapid speed increase. An impermissible speed increase can be prevented by taking into account the delivery fluid pressure, preferably measured at the discharge nozzle as a first operating parameter and the direct or indirect consideration of the delivery fluid viscosity as a second operating parameter in the calculation of the first limit, so that damaging the pump fails.

For small drive motors, a very rapid abrupt increase in pressure would lead to a rapid speed reduction, whereby here too the consideration of the aforementioned Erstbetriebsparameters and the aforementioned further operating parameter to a corrected manipulated variable, i. a corrected speed signal leads, whereby damage to the pump can be prevented in this case.

In the case of the realization of the medium protection, the conveying fluid pressure, the delivery fluid volume flow or the rotational speed or also the delivery fluid viscosity or a parameter, in particular a fluid parameter, of which the delivery fluid viscosity is directly dependent, preferably come into consideration. The manipulated variable is preferably the rotational speed or a rotational speed signal, wherein for calculating the limit value, in particular a maximum permissible rotational speed, a delivery fluid volume flow is considered as the first operating parameter and the delivery fluid pressure (in particular measured at the discharge port of the pump) is taken into account as a further actual operating parameter. As mentioned, the comparison with the at least one limit value can be realized in different ways. Thus, it is particularly preferred if the manipulated variable generated by the controller is used for comparison with the first limit value, or alternatively the corrected manipulated variable output by the first correction means or by the optionally provided further, for example second, correction means. It is also possible not to directly use the aforementioned manipulated variable or a corrected manipulated variable for the comparison, but rather a comparison value which is calculated on the basis of a predetermined functional relationship from the manipulated variable or a corrected manipulated variable. In an analogous manner, it is possible to use the manipulated variable generated by the controller for the comparison with the second limit value or a corrected manipulated variable, wherein the corrected manipulated variable may be the corrected manipulated variable output by the first correcting means, if present, or that of the second correction means output corrected correcting variable. It is also possible to calculate a comparison value, eg a current shear rate, on the basis of one of the aforementioned values and to use this for the comparison.

As already indicated, the logic means may be the manipulated variable generated by the controller, a corrected manipulated variable or a comparison value calculated on the basis of the manipulated variable and / or the corrected manipulated variable or an actual operating parameter, in particular the first actual operating parameter and / or the further actual operating parameter are also compared with at least one for the control means associated positive displacement pump, fixed limit value, wherein in the event that such a limit is exceeded or fallen below by a certain level of correction means, a corrected control variable is output. If the actual operating parameter to be compared is, for example, a measured actual oscillation value and if it exceeds a maximum value (limit value) for the particular positive displacement pump, a corrected manipulated variable is output by the correction means, this manipulated variable correction being corrected by first correction means and / or or may be upstream or downstream by second correction means. In the simplest case, the corrected manipulated variable is a manipulated variable signal increased or reduced by a specific factor, or a manipulated variable signal, the value stored in a memory, or a simulated, calculated value for which an exceeding or falling below the limit value is not to be expected.

The last-described embodiment of the control means is primarily used to detect a sudden damage or sudden damage of the positive displacement pump. If, for example, an oscillation parameter is monitored by sensor means as the measured actual operating parameter and if it exceeds a limit value stored in a non-volatile memory or preferably alternatively or additionally depending on a further measured or calculated actual parameter, then the manipulated variable corresponding to the reference variable is not passed on but one, for example, reduced by a factor of 2 calculated manipulated variable to operate the positive displacement pump as long as possible without any damage, such as bearing damage occurs or worsens, for which the increased vibration value can be an indication.

With regard to the specific embodiment of the controller of the control means, preferably formed by a microcontroller, there are different possibilities. Preferably, the controller is designed as a PI controller or as a PID controller.

With regard to the selection or design of the first actual operating parameter, which is supplied to the controller for determining a manipulated variable and based on which the first (pump protection) limit value and / or the second (Förderfluidschutz-) limit value is calculated if necessary, and the If necessary, it is used for the calculation of the corrected manipulated variable by the correction means, there are different possibilities. Preferably, this first actual operating parameter is a preferably measured, actual controlled variable from the controlled system, in particular a so-called actual main controlled variable, for example an actual pressure of the conveying fluid or an actual pressure difference of the conveying fluid, for example between suction and Pressure side of the positive displacement pump or an actual volume flow of the fluid. The first operating parameter is preferably measured, but can alternatively also be simulated or calculated, in particular from a plurality of further actual operating parameters. As already explained above, the first and / or second limit value must be calculated not only on the basis of the first actual operating parameter supplied to the controller, but additionally on the basis of a functional relationship on the basis of another (further) actual operating parameter. The at least one further actual operating parameter can be a measured auxiliary variable or, in particular, the frequency converter calculated on the basis of an actual value measured, for example a frequency reference of the frequency converter or a nominal torque value of the frequency converter. It is also possible that at least one further actual operating parameter is a measured or calculated on the basis of an actual value auxiliary control variable, in particular a speed of the positive displacement motor or a torque of the positive displacement motor. It is also possible for at least one further actual operating parameter to be included in the calculation of the first and / or second limit value and / or in the calculation of a corrected manipulated variable and / or in the calculation of a comparison value by a measured temperature, for example a conveying fluid temperature or a bearing temperature, in particular a rolling bearing of a drive spindle of the positive displacement pump act. It is also possible for the at least one further actual operating parameter to be a measured vibration value. It is also possible for the at least one further actual operating parameter to be a measured or calculated delivery fluid viscosity. It is also possible for the at least one further actual operating parameter to be a measured leakage quantity. It is particularly preferred if not only the first actual operating parameter and only a single further actual operating parameter are taken into account in the calculation of a limit value or a corrected manipulated variable but, for example, in addition to the first operating parameter, two or even more further, preferably different, actual values. operating parameters ..

For medium protection applications (preferably not for pump protection applications), the at least one further operating parameter may be a measured actual controlled variable, for example a measured actual main controlled variable, for example an actual pressure of the conveying fluid, an actual pressure difference or an actual volume flow. Too little pressure at the suction nozzle can be used as a cavitation indicator. In addition to the pressure as an operating parameter, the delivery fluid viscosity is preferably taken into account, in particular for metrological reasons representative of the viscosity of the delivery fluid whose measured temperature.

The temperature can therefore be additionally or alternatively monitored by a pressure as actual operating parameters. An excess temperature of the conveying fluid can be hazardous to the pump, in particular with regard to a possible bearing damage.

When the limit value calculation and / or the calculation of a corrected control value, the engine speed can be taken into account in accordance with a fixed assignment or function which is directly proportional to the positive displacement pump speed (spindle speed), in particular corresponds to this. Too high or too low a speed can also be a risk, especially if further operating parameters, such as the temperature and / or the pressure exceeds or falls below certain limits. In addition or as an alternative to the above actual operating parameters, vibrations (vibrations) of the positive-displacement pump and / or the positive-displacement pump motor can be monitored. Excessive vibrations jeopardize the alignment between positive displacement pump motor and positive displacement pump with the possible consequence of bearing damage to the positive displacement pump and / or the positive displacement motor. Even with impermissible vibrations mechanical seal damage is possible. Overall, the life of the positive displacement pump can be reduced by impermissible oscillations, in particular if further actual operating parameters, such as the rotational speed and / or the temperature and / or the pressure exceed or fall below certain limits.

In addition or as an alternative to the above further operating parameters, the viscosity of the conveying fluid, which is functionally related to the conveying fluid temperature, may be directly or indirectly above the temperature in determining a limit value, a corrected manipulated variable or, if provided of a comparative value. Too low a viscosity can be hazardous to the pump because of the resulting decreasing lubricating properties of the fluid between the spindles. Too high a viscosity may be positive displacement pump motor hazard, so that the torque increases too much. In addition, too high a viscosity (too low a temperature) can be a risk of displacement, for example when using a magnetic coupling, which can often break off unnoticed due to too high a viscosity, which leads to the destruction of the positive displacement pump or of the magnetic coupling. In addition to the above-described actual operating parameters, which are measured individually, in groups or preferably together to ensure component protection (positive displacement pump protection) or to ensure or guarantee a delivery fluid quality and taken into account in calculations according to a mathematical function, at least one of the following actual operating parameters be monitored, for example, the torque which is functionally dependent on the viscosity of the conveying fluid. In particular, the torque can be taken into account as an indicator of an increasing displacement of the positive displacement pump. Additionally or alternatively, the positive displacement pump motor current can be included in the calculation of a limit value, a corrected manipulated variable or, if provided, in a comparison value. The motor current is a simple and inexpensive to measure size, especially at constant other parameters, such as the viscosity of the torque, which in turn can indicate wear of the pump. Additionally or alternatively, the leakage rate can be monitored. This is based on the idea that each mechanical seal requires a nominal leakage in order to lubricate the static and dynamic components of the mechanical seal. If the leakage rate increases, this can be an indicator of incipient mechanical seal damage.

If not, which is preferred, however, the manipulated variable generated by the controller or the manipulated variable corrected by the correction means should be compared with a first or second limit value, but additionally or alternatively for this comparison, a comparison value should be calculated which is functional Relationship to the manipulated variable or the corrected manipulated variable, may be included in the calculation of this comparison value based on a functional relationship, several of the above actual operating parameters, in particular the first actual operating parameters and at least one of the other actual operating parameters.

It is particularly preferred if the first and / or second limiting value specification means and / or the first or second correction means take into account in their calculations for the displacement pump-specific geometry parameters assigned to the control means, for example a gap width and / or a spindle diameter. In addition or as an alternative, the limit value specification means and / or the correction means may form a delivery fluid parameter stored in a storage, taking into account in particular a shearing behavior of the delivery fluid.

Thus, it is advantageous in particular with regard to the monitoring of the quality of the delivery fluid or of the final product produced therewith to take into account the angular velocities of the positive displacement pump spindle when calculating a limit value, a corrected manipulated variable or, if provided, during the calculation of a comparison value. In this case, preferably at least one geometry parameter and the pitch angle of the relevant spindle should be taken into account, since different pitch angles of the spindle at the same engine speed lead to different relative speeds within the positive displacement pump.

Also conceivable is a variant in which the at least one measured actual parameter, for example the first actual operating parameter or a further actual parameter, is not fed directly by sensor means into the control means but at the at least one actual operating parameter to the control means of a process control room is transmitted, in particular, as will be explained later, via a bus system. It is particularly preferred if a shear rate is taken into account in the calculation of the at least one first and / or at least one second limit value, in particular a maximum permissible shear rate stored in a memory and / or one currently based on at least one actual operating parameter calculated shear rate is considered according to a functional relationship.

As already explained, it is conceivable that, in addition to a dynamic limit value analysis, a static limit value analysis takes place in which the manipulated variable, a corrected manipulated variable, a comparison value or directly a first operating parameter and / or a further operating parameter with one in a preferably non-volatile memory The limit value stored in the logic means is / are compared and, if the limit value should be exceeded or undershot by a predetermined amount, a corrected manipulated variable is determined and output so as not to jeopardize the pump or product quality. In the simplest case, for this purpose, the manipulated variable predetermined by the controller or, based on a preceding comparison, already corrected manipulated variable can be increased or reduced by a predetermined amount, in particular a predetermined factor.

In addition or as an alternative to at least one measured and first actual operating parameter and / or additionally or alternatively to a measured or calculated further actual operating parameter and / or to at least one predetermined displacement pump-specific geometry parameter, the first and / or second limit value specification means and / or the first and the second limit value specification means In the calculation of the corresponding limit value or the corrected manipulated variable, a second or second correction means may take into account a delivery fluid parameter (fluid-specific property value / constant) in accordance with a mathematical function or assignment which is stored, for example, in a non-volatile memory of the control means. Preferably, it can be selected manually or automatically under different fluid parameter data sets, for example as a function of a measurement result. The shear behavior of the conveying fluid is preferably taken into account as the conveying fluid parameter, in particular if a shear gradient is used to determine a limiting value or a corrected actuating variable.

It is particularly expedient if the logic means for determining and / or signaling a maintenance due date of the positive displacement pump in dependence of a measured or calculated actual operating parameter and / or in dependence of a are formed for the control means associated displacement pump specific parameters. For this purpose, the logic means preferably comprise a corresponding functional unit which takes into account the measured or calculated actual parameter and / or the displacement-pump-specific parameter in determining the maintenance due date. This functional unit preferably calculates the maintenance due date based on a predetermined (functional) assignment. The maintenance due date is preferably signaled via corresponding signaling means, for example a display and / or an LED traffic light, which can emit different color signals.

It is particularly expedient if the first and / or second correction means are designed such that, in the event that the limit value is exceeded or fallen below by a predetermined, in particular very high or very low value, a stop signal for the positive displacement pump motor, in particular emit for a motor contactor, due to which the positive displacement pump motor is stopped, in particular to avoid further endangering the positive displacement pump or other process units or the quality of the conveying fluid.

In a development of the invention, it is advantageously provided that the control means are communicating via a bus system, in particular a CAN bus system, in particular in order to communicate with other positive displacement pump control means and / or a process control center, ie to transmit and / or receive data. It is particularly expedient if in the control module, in particular for communication with the control room and / or at least one further module, a CAN bus system is assigned, which is known mainly from the automotive industry. This bus system is surprisingly found to be particularly reliable and robust in connection with positive displacement pump systems. It is particularly expedient if the control means are assigned input means, in particular in the form of at least one key, preferably in the form of a plurality of keys and / or a cloth screen, etc. in order to configure and / or read the control means. Particularly preferably, via the input means one of a plurality of stored in a non-volatile memory system parameter data sets and / or Förderfluidparameterdatensätzen.

An embodiment variant of the control means is particularly expedient, in which the control means have memory means which are designed and controlled to store, in particular also to log, received, calculated and / or transmitted data, in particular measured values or voltage profiles. The memory means are particularly preferably designed and controlled in order to store measured actual operating parameters and / or reference variables and / or manipulated variables and / or corrected manipulated variables.

The invention also leads to a positive displacement pump system, comprising a positive displacement pump, preferably designed as an electric motor positive displacement motor and the positive displacement pumps associated, as described above formed control means for generating an optionally corrected manipulated variable, in particular a voltage signal for the also included by the system frequency converter of the positive displacement motor. The control means are associated with reference variable presetting means, which supply the control means with the input guide variable, for example a nominal volume flow, a desired pressure, etc., preferably in the form of a voltage signal. The function of the command value specification means can in particular be taken over by a process control center which, if present, forms further process units, such as further positive displacement pumps, monitoring and / or controlling and / or regulating in addition to the positive displacement pump assigned to the control means. In addition or as an alternative to a process control system, the reference variable can be preset manually, for example by a corresponding setting on the control means and then generated by the control means itself and / or by a simple voltage source separate from the control means and outputting an electrical voltage value as a reference variable.

It is particularly expedient if the control means are designed to communicate with the process control room and / or with other control means via a bus system, in particular a CAN bus system, wherein via this bus system, for example measured actual operating parameters can be transmitted and stored for example in one of several control means.

The system preferably also comprises at least one sensor (sensor means), preferably at least two sensors, which are connected to the control means in signal-conducting fashion, the sensor or the sensors for measuring the first actual operating signal and possibly at least one further actual sensor. Operating signal is formed and arranged. For example, it is a pressure sensor for determining a fluid pressure, in particular a differential pressure and / or a temperature, for example a delivery fluid temperature or a storage temperature. It may also be a tachometer for determining the Verdrängerpumpenzahl and / or a torque meter for detecting the Verdrängerpumpenmotordrehmoments and / or a vibration sensor for measuring a vibration value and / or a fluid viscosity meter for determining the fluid viscosity and / or a Leckageatenmesser and / or Volumetric flow meter act. It is particularly expedient if the control means are signal-connected to the frequency converter in order to receive an actual auxiliary manipulated variable as the first and / or at least one further actual operating parameter, in particular a rotational frequency setpoint or a torque setpoint from the frequency converter.

Furthermore, the invention also leads to a drive method for driving a frequency converter, wherein the method or advantageous embodiment of the method has already been described above with reference to preferred control means.

Further advantages, features and details of the invention will become apparent from the following description of preferred embodiment and from the drawings. These show in:

1 shows a possible embodiment of control means which are designed to control variable generated by a controller with a first (pump protection)

Limit to compare

2 shows an alternative embodiment of control means which are designed to compare a manipulated variable generated by the controller with a (conveying fluid protection) limit value,

Fig. 3 shows a further embodiment variant of control means in which the control variable generated by the controller with a first threshold and / or a second threshold is too comparable and possibly correctable, the comparison sequence also different, as shown in Fig. 4, i. can be realized in reverse order,

Fig. 4 is an NPSH diagram, and

Fig. 5 is a diagram of the physical relationship between the delivery fluid pressure, measured at the discharge nozzle of the pump, the

Delivery fluid viscosity (medium viscosity) and the pump speed, here a minimum pump speed.

In the figures, like elements and elements having the same function are denoted by the same reference numerals.

Embodiment of FIG. 1

In Fig. 1, the structure of a positive displacement pump system 1 is shown schematically. This comprises a in the embodiment shown as a single or multi-spindle pump, in particular three-spindle pump, trained positive displacement pump 2. The positive displacement pump 2 is operatively connected to a motor shaft of a trained as an electric motor displacement pump motor 3, which comprises a frequency converter 4, depending on a generated by a controller 6 Manipulated variable Ys or a corrected manipulated variable Y's or possibly multiple times corrected manipulated variable Y's controls the energization of the motor windings of the positive displacement pump motor 3 and / or regulates. To generate the manipulated variable Ys or a corrected manipulated variable Y's, the positive displacement pump system 1 comprises, for example, control means 5 formed by a microcontroller, comprising a previously mentioned regulator 6 and logic means 7.

The control means 5 are preceded by command value presetting means 8, for example a process control room, which supply the control means 5 with a reference variable W, for example an electrical voltage signal representing a set volume flow or a set pressure.

The reference variable W and an externally supplied first actual operating parameter X are supplied to the controller 6, more precisely to a difference former 9 of the controller 6, which calculates the difference XW. The actual controller 6, which is designed, for example, as a PI or PID controller, thus determines a manipulated variable Ys on the basis of the reference variable W and the first actual operating parameter X measured here. This is not fed directly to the frequency converter 4 as in the prior art, but first passes through logic means 7. These include in the embodiment shown first comparison means 10 which compare the control variable generated by the controller 6 Ys with at least a first limit, preferably a maximum to be observed first Limit value YGrenzmax and / or a minimum limit value Yorenzmin- to be followed Instead of a direct comparison of the manipulated variable Y _s with the at least one first limit value, with the aid of not shown (optional) comparison value specification means based on the manipulated variable Ys with the manipulated variable Ys in a functional context Comparative value are calculated, in its calculation according to a functional relationship and at least one actual operating parameters, for example, the first actual operating parameters X and at least one further, to be explained later further actual operation can incorporate parameters. Also, according to a functional relationship for calculating the comparison value, the comparison value specification means can take into account at least one geometry parameter of the positive displacement pump and / or one delivery fluid parameter, which then also takes into account the limit value must be taken into account. In the exemplary embodiment shown, however, this additional comparison value calculation step is saved and the manipulated variable Y _{s is} compared directly with at least one first limit value Yorenzmax and / or Yorenzmin, wherein the at least one first limit value represents a positive-displacement pump limit whose overflow or undershoot is a defect of the positive-displacement pump entails or could have.

The comparison means 10 is associated with a first functional unit 1 1, which includes first correction means 13 in addition to first limit value specification means 12. The functional unit 1 1 calculates the at least one first limit value Y limit, Y min value, which is supplied to the comparison means 10 in addition to the manipulated variable Y _s generated by the controller 6. The comparison means now check whether the manipulated variable Y _s falls below a maximum first limit value YGrenzmax and / or whether the manipulated variable Ys exceeds a minimum first limit value Yorenzmin. If this is the case, the manipulated variable Y _s is a permissible control variable which does not endanger the positive displacement pump, which can be supplied to further comparisons and correction routines, not shown, or as shown directly as input signal to the frequency converter 4 of the positive displacement motor 3 on this basis controls.

To calculate the at least one first limit value, the first actual operating unit 1 1 is supplied with the first actual operating parameter X and another measured or calculated actual operating parameter Y _H and / or X _H , wherein the actual operating parameter Y _{H is} shown in FIG Embodiment is an auxiliary manipulated variable of the frequency converter, for example, a rotational frequency setpoint or a torque setpoint of the frequency converter. These are not measured values, but based on at least one actual parameter, for example based on a current control measurement calculated by the frequency converter, in particular simulated values. In the exemplary embodiment shown, the further actual operating parameter X _H is an auxiliary control variable, for example an engine and / or positive displacement pump speed or a torque, which are preferably measured directly on the engine 3. In any case, therefore, of the first limit value specification means 12 for calculating the at least one pump protection limit value, an operating parameter, ie For example, the first actual operating parameter, in this case the actual value of the controlled variable from the process control line 14, and at least one further actual operating parameter YH, XH or a preferably measured main control variable Y _H H for the process control variable X, for example a pressure or a volumetric flow.

If the comparator means detects that the maximum first limit value YGrenzmax has been exceeded and / or falls short of the minimum first limit value Ycrenzmin, this is reported to the first functional unit 1 1, whose first correction means 13 then determine a corrected manipulated variable Y's taking into account of the first actual operating parameter X and one of the aforementioned further actual operating parameters Y _H , XH _, YHH _. This corrected manipulated variable Y ' _s can then, as shown, be supplied to the comparison means as an input for comparing with a first limit value Ycrenzmax and / or Yorenzmin or bypassing the comparison means (not shown) to a further comparison and correction procedure or directly to the frequency converter 4 as an input signal ,

From a preferably non-volatile memory 19, specific geometry parameters GP and / or conveying fluid parameters FP specific to the conveying fluid, such as the shear behavior of the conveying fluid, can be supplied to the first limiting value specification means 12 and / or the first correction means 13 for the positive displacement pump assigned to the control means 5, which are included in the context of a functional relationship in the calculation of the first limit values Yorenzmax, YGrenzmin, and / or the corrected manipulated variable Y ' _s . In the exemplary embodiment shown, the corrected manipulated variable Y ' _s is the maximum or minimum permissible first limit value Ycrenzmax, YGrenzmin, by which the manipulated variable Ys generated by the controller comes as close as possible. In this respect, the first limit value specification means 12 and the first correction means 13 include a common computer (computer means), since the corrected manipulated variable Y ' _s in the exemplary embodiment shown corresponds to a first limit value Ycrenzmax, YGrenzmin. The manipulated variable Ys generated by the controller is overwritten with the corrected manipulated variable Ys. In particular, when the corrected manipulated variable Y's is not to correspond to the first limit value, the first correction means 13 and the first limit value specification means 12 can be realized completely separately, ie with their own calculation means, ie in separate functional units. This is, of course, also possible for the case explained above, that the corrected manipulated variable Y's should correspond to a first limit value, in which case, as shown in FIG. 1, limit value specification means 12 and correction means 13 merge with one another, ie have a common calculation routine. In the following, the embodiment of FIG. 1 will be described with reference to exemplary, non-limiting concrete embodiments.

First example

The first actual operating parameter X corresponds to the actual controlled variable, in the exemplary embodiment shown a pressure, measured in bar. It is assumed that the reference variable X is a pressure and is initially 20 bar. Likewise, the actual operating parameter X is measured as 20 bar.

Now a command value change takes place. The reference variable X changes, for example, by a corresponding specification from 20 bar to 10 bar. This results in a control deviation WX = 10 bar. The controller 6 determines a new manipulated variable Y _s , in this case a speed-proportional voltage value, which is significantly smaller than in a previous run or in a previous calculation. The first threshold value setting means 12 calculates a minimum allowable limit YGrenzmin. This represents in the embodiment shown a minimum allowable speed. Maintaining a minimum permissible speed is desirable in order to avoid the risk of lubricant leakage when this minimum permissible speed is exceeded.

The minimum permissible speed, ie the minimum permissible limit YGrenzmin is calculated based on the following functional relationship:

In the functional context Yorenzmax corresponds to the minimum permissible limit value. This is a minimum allowable speed (n _ON | _AESS strength).

The first actual operating parameter X is in this case the measured controlled variable, here the new actual pressure of 10 bar. The factor · ^α is a further operating parameters, namely a measure for the, in particular via a temperature measurement of the conveying fluid certain operating viscosity of the fluid or for the situation influence of viscosity on the maximum allowable pressure. This value is in the illustrated embodiment 10 ⁰ ^'32 for the particular medium. The constant k is the correction value for the lubricity of the medium, this is exemplified by 0.75 for the particular medium.

The constant b is a correction value for the tribocharging capability of the pump casing. This is in the embodiment shown 1. The pump-specific characteristic value c is a characteristic value for the radially loaded rotor diameter. This is for example in the embodiment shown 0.55.

The minimum permissible limit YGrenzmin is supplied to the first comparison means 10, which compare the control variable Ys determined by the controller 6 with this. In dependence of the comparison, either the manipulated variable Ys determined by the controller is sent to the frequency or a corrected manipulated variable Y _'s determined by the first correction means, which is preferably the previously calculated (or recalculated) minimum permissible limit Yorenzmin corresponds.

Second example

The first actual operating parameter X corresponds to the actual controlled variable, here a pressure. An actual pressure of 20 bar is measured. Due to a corresponding specification, the setpoint of the controlled variable, ie the reference variable W changes from 20 to 30 bar. At the same time there is a change in the disturbance variable. It is assumed that the flow resistance increases, as a result of a smaller flow area, ie a smaller flow diameter, for example, as a result of a tool change. In practice, this leads to the fact that the actual operating variable X, ie the actual pressure, will clearly exceed the reference variable W, or would, since initially being conveyed with an unchanged rotational speed and, in the meantime, the flow resistance has increased significantly due to the tool change , The resulting control deviation at the subtractor output then leads to a significant reduction, ie reduction of the manipulated variable Y _s . In the event that this uncorrected transmitted to the frequency converter 4 as a target value, this would result in a risk to the pump with respect to the allowable pressure at a reduced low speed. To prevent this, the aforementioned manipulated variable Y _{s is} compared with the minimum limit value Yorenzmin (first limit value) to be calculated, which represents the minimum permissible rotational speed. The calculation is based on the functional relationship specified in the first embodiment. Since the manipulated variable Ys falls below the minimum permissible limit value Ycrenzmin, ie the minimum permissible rotational speed, a corrected manipulated variable Y ' _{s is} output by the first correcting means 13, which is transmitted to the frequency converter instead of the manipulated variable Ys.

The corrected manipulated variable Y ' _s preferably corresponds to the calculated minimum permissible value

Limit value Ycrenzmin.

Third example

The reference variable W is a volume flow measured in l / min. The first actual operating parameter X is a measured volume flow. It is assumed that the volumetric flow demand increases during operation. In the example shown, the reference value is to double, namely from 1500 l / min to 3000 l / min. From the resulting control deviation WX, the controller 6 determines a manipulated variable Ys, here a speed. This manipulated variable Ys, ie from the controller. 6 predetermined speed is compared by the comparison means 10 with a maximum allowable speed, ie a first limit Yorenzmax- This maximum allowable speed is determined based on the NPSH _ve available, ie based on the existing NPSH or Haitureruckhöhe the system. In the exemplary embodiment shown, this amounts to 8 mWs (meter of water column). Based on the NPSH _ve rfügbar and another measured actual operating parameters, here the viscosity of the medium, Yorenzmax, that is, the maximum speed determined. This is done by way of example with reference to the diagram shown in FIG. 4 or alternatively via polynomials stored in a non-volatile memory, which are based on the following calculation basis:

NPSH = / (pump size (d _a ), lead screw angle, viscosity V, speed n) where from the pump size via the spindle diameter d _a and the lead screw angle to the axial velocity of the medium within the pump valid for a certain size and pitch angle can be closed so that there is a simplified relationship:

NPSH = {yax BG stgg 'viscosity V, speed n) Consequently

v ax zulBG NPSH = f (v

'n)' so that about the context

v = S * n or n = ^ z-

Finally, the relationship γ _ _ ^V ox zul BG NPSH

Limit max ~ zul BG NPSH ~ can be produced. It is therefore possible to calculate a permissible pump speed n _{nd BG} for a pump with a specific pump size, a specific spindle pitch angle and a specific NPSH value. In the diagram according to FIG. 4, the water column (mWs) is indicated in meters on the left vertical axis of the NPSH. On the right vertical axis, the speed is given in revolutions per minute. On the horizontal axis, the axial velocity of the fluid is given in m / s. The diagram refers to an exemplary pump with a size 20 and a lead angle of the spindle of 56 °. The linearly rising line characterizes the axial velocity v _{ax of} the medium (delivery fluid) as a function of the rotational speed.

To determine the first limit value Yorenzmax, ie the maximum permissible rotational speed, it is necessary to move to the right in the diagram, starting from an NPSH of 8 mWs, up to the curve characteristic for the measured viscosity of 500 mm ² / s. At the intersection with this curve, the diagram must move up to the linear line. At the intersection with this line, the maximum permissible speed, ie the first limit value Yorenzmax, can then be read on the right vertical axis. This is about 3800 revolutions / min for the measured viscosity, ie the other actual operating parameters.

As mentioned above, the reference variable, ie the required volume flow doubles, which is 3000 l / min due to the linear relationship between a manipulated variable change from the assumed 1500 rpm. Since this manipulated variable Y _s of 3000 1 / min is smaller than the first limit YGrenzmax of about 3800 1 / min, the manipulated variable Ys can be transmitted to the frequency converter 4 as an input variable.

If the reference variable were not only to double, but to triple, for example, this would result in a manipulated variable of 4500 1 / minute, which would be greater than the first limit value Y limit, so that the correction means 13 will overwrite the manipulated variable Ys preset by the controller 6 with a corrected manipulated variable Ys which corresponds, for example, to the first limit, ie in the present example 3800 1 / min. Embodiment of FIG. 2

The exemplary embodiment according to FIG. 2 differs from the exemplary embodiment according to FIG. 1 only in that the manipulated variable Ys generated by the controller 6 is not compared with at least one first limit value ensuring or representing the positive displacement pump protection, but with at least one second, the delivery fluid quality ensuring limiting value. In the exemplary embodiment shown, this is a second limit value.

The at least one second limit value Yorenzmax, Ycrenzmin ensures compliance with the delivery fluid quality. In the embodiment shown, only a single, maximum second threshold Ycrenzmax is provided by second threshold presetting means 15, alternatively providing a plurality of second threshold values, e.g. in addition, a minimum limit value Yorenzmin that can be calculated to ensure the delivery fluid quality.

In any case, second comparison means 16 compare whether the manipulated variable Y _s generated by the controller 6 or a manipulated variable already corrected in a preceding further correction procedure not included here exceeds the second limit value Yorenzmin by a certain amount. If the manipulated variable Ys is less than or equal to the maximum limit value, the manipulated variable Y _s generated by the controller 6 or supplied to the comparison means 16 is made available (calculated) to the frequency converter 4.

Otherwise, with the aid of second correction means 18 included in a second functional unit 17 in addition to the second limit value specification means 15, a corrected manipulated variable Y ' _{s is} provided, with which the manipulated variable Y _{s is} overwritten. To calculate the at least one second limit value Yorenzmin, the second limit value specification means 15 take into account the first actual operating parameter X and at least one further (other) actual operating parameter, for example an auxiliary manipulated variable Y _H , an auxiliary controlled variable X _H and / or a skin manipulated variable Y _H _H. Also it is feasible that in the calculation additionally take into account geometry parameters GP of the positive displacement pump and / or delivery fluid parameters FP, as well as the vibration.

Fourth example

The fourth example concerns the protection of the medium, i. The second limit value is determined such that the manipulated variable does not result in a negative impairment of a quality parameter of the delivery fluid (delivery medium) conveyed by the positive displacement pump.

In the specific example, it should be ensured that the pumped medium is not sheared unduly. The maximum permissible shear rate of the medium is therefore included in the calculation of the second limit value. It should again be realized a speed control, so that the second limit corresponds to a maximum permissible speed. This means that the first operating parameter X is a volume flow of the process line. In addition to the medium-specific limit of the maximum permissible shear rate, the determination of the second limit value includes functional conditions of the pump, i. Speed relationships are taken into account, namely the angular velocity difference of the rotating positive displacement rotors (spindles) relative to the stationary pump housing. The velocity ratios in the columns are directly proportional to the pump speed and there is an inversely directly proportional relation to the size of the function gap, i. to the current linear shear rate. This function gap depends on the one hand on pump-specific conditions, namely on the present actual radial gap, i. from the fixed pump rotor radial play and also from current operating conditions, namely the current pressure load (delivery fluid pressure) and the respective current viscosity of the delivery fluid. The latter two further actual operating parameters are measured and found in the calculation of the second limit Yorenzmax, i. considered in the calculation of the maximum permissible speed.

For example, a delivery fluid having a dynamic viscosity η of 5 Pas is delivered. This corresponds to a kinematic viscosity v of 5000 mm ² / s, wherein assuming a density p of 1000 kg / m ^3, while maintaining a maximum permissible shear stress τ of 100000 N / m ^2, a maximum permissible shear rate D _ZU | of 20000 1 / sec for the delivery fluid in a given pump. This is characterized by a rotor diameter of D _a = 70 mm and by a differential pressure-dependent radial gap S = h ₀ , which gives a value of 0.021 mm at Δρ = 5 bar. This results in a maximum permissible speed, ie a second limit Yorenzmax of 191 1 / min. As long as the preset of the regulator 6 manipulated variable Ys is below the aforementioned value, the manipulated variable Ys can be passed directly to the inverter 4 - otherwise the manipulated variable Ys is of second correction means 18 corrected by or limited manipulated variable Y "overwritten _s.

The example described above is based on the following calculation principles:

For example, T _zu1 = Ό * η and η = ν * ρ for Newtonian fluids follows

D 'zul

zul

v * p

Furthermore, applies

W z, ul

With insertion in

AW

W _zul = D ^ * S or in D _zul = - ^ - can be calculated by summing all occurring constants to k the maximum allowable speed:

Ό * π * η D. * k * S

D = - -> n = -

k * S ^zul Ώ _α * π

The maximum permissible speed therefore corresponds to the limit value Y _Gn

In the event that the conveying fluid (medium) to be pumped does not exhibit Newtonian behavior, the Reynolds numbers in the pump function gap, the shear rate and the resulting representative viscosities resulting therefrom would have to be calculated according to known physical relationships, for example for pseudoplastic conveying fluids. As a result, the permissible conditions for these fluids can be monitored and maintained in the same way as in the case of new-type conveying fluids.

Exemplary embodiment according to FIG. 3

2, ie the control means 5 are designed such that the manipulated variable Ys output by the controller 6 has both at least one first limit value (pump protection limit value) and at least one second limit (medium protection limit) can be compared. In the embodiment shown in FIG. 3, the control variable Y _s generated by the controller 6 is first compared with a first and then with a second threshold, wherein the reverse arrangement is of course feasible, ie, that first with a second and then with a first Limit value is compared.

It is characteristic of the embodiment according to FIG. 3 that the output value of the first comparison forms the input variable for the second comparison, wherein the output variable of the first comparison can be the uncorrected manipulated variable Y _s , namely in the first comparison there is no limit value overshoot or undershoot and thus Y _s is not corrected or alternatively by a manipulated variable Y's corrected by the first comparison means 10. Ys or Y ' _s are then the input variables for the second comparison means 16. If no correction is made here, the input value for the second comparison Y _s or Y' _{s is sent} to the frequency converter 4 or, in the case of a correction, the corrected manipulated variable Y _s .

In the exemplary embodiment shown, first and second decision-making means 20, 21 are provided in which it is determined whether a pump protection comparison or a medium protection comparison is to be carried out. The respective decision can be predefined by software, for example, so that the user can alternatively only implement a pump protection comparison or a medium protection comparison, or both comparison operations.

Embodiment of FIG. 5

This exemplary embodiment represents a preferred embodiment for realizing the pump protection. The manipulated variable is a speed signal for the pump, the pump speed being plotted in the diagram on the left vertical axis. As the first actual operating parameter, the delivery pressure, measured at the discharge nozzle of the pump, flows into the calculation of the first limit value, the delivery fluid pressure being plotted on the right vertical axis. The delivery fluid viscosity (medium viscosity) flows into the calculation of the first limit value as a further actual operating parameter, the medium viscosity being plotted on the horizontal lower axis. As a guide variables come here alternatively the delivery fluid volume flow or the pump speed or the delivery fluid pressure into consideration. In the specific embodiment, it is assumed that the delivery fluid pressure is the reference variable.

In the embodiment shown, it is assumed that the conveying fluid viscosity (medium viscosity) due to a corresponding medium change from 12mm ^{2 /} s to 9 mm ^{2 /} s, to 6 mm ^{2 /} s, to 4 mm ^{2 /} s and then (stepwise) up to 2mm ^{2 /} s drops. The delivery fluid volume flow may fluctuate. The reference variable, ie the process pressure (delivery fluid pressure) should initially be kept at 10bar, then increase to 20bar, etc., ie incrementally by 10bar each to a maximum of 50bar. In other words, the reference variable gradually changes from initially 10bar to 50bar. The controller outputs a manipulated variable (Y _s ) as a function of the reference variable (W). The first limit value specification means calculate a first limit value, in the present case a minimum rotational speed Yorenzmin as a function of the first actual operating parameter, here the delivery fluid pressure and the further actual operating parameter, here the medium viscosity, wherein in the concrete exemplary embodiment the medium viscosity is determined indirectly via the delivery fluid temperature. In the present Ausführunsbeispiel falling below the first limit, ie the minimum speed would cause a defect state of the positive displacement pump. In the specific embodiment, the comparison means compare the control variable predetermined by the controller, ie a speed signal with the first limit value calculated by the first limit value specification means. If the manipulated variable in the illustrated embodiment is above this first limit value, the manipulated variable is forwarded to the frequency converter as an input signal. If the manipulated variable undershoots the first limit value, a corrected manipulated variable is determined or determined as an input signal in the embodiment shown and passed on to the frequency converter as a corrected manipulated variable in the embodiment shown by the first correction means passing on the first limit value determined by the limit value specification means.

LIST OF REFERENCE NUMBERS

1 positive displacement pump system

2 positive displacement pump

3 positive displacement motor

4 frequency inverters

5 control means

6 controllers

7 logic means

8 guide variable specification means

9 differential images of the controller

10 first comparison means

1 1 first functional unit

12 first threshold value specification means

13 first correction means

14 process control line

15 second threshold value setting means

16 second comparison means

17 second functional unit

18 second correction means

19 memory

20 first decision-making tools

21 second decision-making tools

Ys manipulated variable

Y _s ' corrected manipulated variable

Ys "corrected manipulated variable

X first actual operating parameter (preferably actual controlled variable)

YHH further actual operating parameter (main control variable)

Y _H further actual operating parameter (auxiliary manipulated variable)

XH further actual operating parameter (auxiliary control variable)

W reference size

GP Geometry parameter of the positive displacement pump

FP delivery fluid parameters

Claims

claims

Control means for controlling a frequency converter (4) of a positive-displacement pump motor (3) of a positive displacement pump (2) comprising a controller (6) for generating a manipulated variable (Ys) for a frequency converter (4) of a positive-displacement pump motor (3) as a function of a reference variable ( W) and a first actual operating parameter (X), in particular the conveying fluid pressure, is formed, characterized in that the controller (6) logic means (7) are assigned, the first limit value setting means (1 2), which are designed to at least a first limit value (Yorenzmax, Ycrenzmin) as a function of the first actual operating parameter (X) and at least one further actual operating parameter (XH, YH, YHH), in particular the delivery fluid viscosity, the exceeding or falling below of which is a defective state of the positive displacement pump ( 2), and

the first comparison means (1 0), which are designed, the manipulated variable (Ys) or a corrected manipulated variable (Y's, Y "s) or one according to a functional relationship from the manipulated variable (Y _s ) or the corrected manipulated variable (Y ' _s , Y "s) determined comparison value renzmax with the at least one limit value (Y _G, Ycrenzmin) to be compared, and

the first correction means (1 3), which are designed to determine a corrected manipulated variable in the event that the first comparison means (1 0) exceeds or falls below the at least one first limit value (Yorenzmax, Ycrenzmin) by a certain amount (Y ' _s , Y "s) which preferably corresponds to a limit value (Y _G _en zmax, Yasmin) determined by the limit value specification means (12), and / or the second limit value specification means (1 5), which are designed to determine at least one second limit value (Ycrenzmax, YGrenzmin) as a function of the first actual operating parameter (X) and at least one further actual operating parameter (XH, YH, YHH) ZU, its exceeding or falling below a negative impairment of a quality parameter of the funded with the positive displacement pump (2) conveying fluid could result, and the second comparison means (1 6), which are formed, the manipulated variable (Ys) or a corrected manipulated variable (Y _'s, Y' s), or (according to a functional relationship of the manipulated variable Ys) or the corrected manipulated variable (Y's, Y "renzmax s) determined comparison value with the at least one second threshold value (Y _G, YGrenzmin) to be compared, and

the second correction means (1 8), which are adapted to a corrected in the event that the second comparison means (1 6) above or below the at least one second limit value (Ycrenzmax, YGrenzmin) by a certain amount Output manipulated variable (Y ' _s , Y "s), which preferably corresponds to one of the second limit value setting means (1 5) determined limit value (Ycrenzmax, YGrenzmin).

Control means according to claim 1,

characterized,

the first actual operating parameter is a measured actual controlled variable (X), in particular an actual pressure, an actual pressure difference or an actual volume flow of the conveying fluid.

Control means according to one of claims 1 or 2,

characterized,

that the at least one further actual operating parameter is a measured actual controlled variable (X), in particular an actual pressure, an actual pressure difference or an actual volume flow of the conveying fluid, and / or that the at least one further actual operating parameter is a measured or Auxiliary manipulated variable (YH) calculated on the basis of the actual value, in particular a rotational frequency setpoint of the frequency converter (4) or a torque setpoint of the frequency converter (4), and / or that the at least one further actual operating parameter is a measured or calculated based on an actual value Auxiliary control variable (XH), in particular a rotational speed of the positive displacement pump motor (3) or a torque of the positive displacement pump motor (3) and / or that the at least one further actual operating parameter is a measured temperature, in particular a delivery fluid temperature or a storage temperature of the positive displacement pump (2) and / or that the at least another actual operating parameter is a measured vibration value and / or that the at least one further actual operating parameter is a measured or calculated delivery fluid viscosity and / or that the at least one further actual operating parameter is a measured leakage rate.

Control means according to one of the preceding claims,

characterized,

in that the logic means (7) comprise at least one comparison value determination means which is designed to be based on a functional relationship between the manipulated variable (Y _s ) or the corrected manipulated variable (Y ' _s , Y "s), and / or from the first and second the at least one further actual operating parameter (X _H , Y _H Y _HH ).

Control means according to claim 4,

characterized,

in that the comparison value determining means are designed in such a way that they additionally have at least one specific geometry parameter (GP), preferably one, stored in a memory (19) for the positive displacement pump (2) assigned to the control means (5) for determination of the comparison value within the functional context Slit width or a spindle diameter, and / or from a stored in a memory (19) Förderfluidparameter (FP), in particular the shear behavior of the delivery fluid, take into account.

Control means according to one of the preceding claims,

characterized,

in that the first and / or the second limit value specification means correspond to the first or second limit value as a function of at least one positive displacement pump (2) stored in a memory (19) and assigned to the control means (5). specific geometry parameters (GP), preferably a gap width, or a spindle diameter, and / or as a function of a stored in a memory (1 9) Förderfluidparameters (FP), in particular the shear behavior of the conveying fluid, are determined, and / or that the first and or the second correction means the corrected manipulated variable (Y's, Y "s) as a function of at least one in a memory (1 9), for the control means (5) associated with the positive displacement pump (2) specific geometry parameter (GP), preferably a gap width, or a spindle diameter, and / or as a function of a stored in a memory (1 9) Förderfluidparameters (FP), in particular the shear behavior of the conveying fluid, are designed determining.

Control means according to one of the preceding claims, characterized

in that the first and / or the second limit value specification means determine the first or second limit value as a function of a minimum or maximum shear rate in the positive displacement pump (2) stored in a memory (1 9) for the positive displacement pump (2) assigned to the control means (5). and / or are designed as a function of the actual shear rate, and / or that the first and / or the second correction means the corrected manipulated variable (Y's, Y "s) as a function of at least one in a memory (1 9) stored for the positive-displacement pump (2) associated with the control means (5) is designed to determine the specific shear rate in the positive-displacement pump (2) and / or as a function of the actual shear rate.

Control means according to one of the preceding claims, characterized

in that the control means (5) have at least one input for the first actual operating parameter (X), and a plurality of inputs for the additionally at least one further actual operating parameter (X _H , YH, YHH).

Control means according to one of the preceding claims,

characterized, in that the first and / or the second comparison means are designed to be the first actual operating parameter (X) and / or the at least one further actual operating parameter (XH, YH _, YHH) and / or one according to a functional relationship from the first actual Operating parameters (X) and / or calculated from the at least one other actual operating parameters (X _H , YH _, YHH)

Value or a control value (Ys) of the controller (6) or a corrected spot size or on the basis of the manipulated variable (Y _s) or the corrected manipulated variable (Y _'s, Y' s) calculated comparison value with at least one in a memory (19 ) of the logic means (7) and that the first and second correction means, respectively, are designed to be in the event that the first

Comparing means ascertaining that the at least one defined limit value is exceeded or undershot, a corrected manipulated variable (Y ' _s, Y "s) is output.

characterized,

that in a non-volatile memory (19), in particular an EEPROM, the control means (5) different system parameter data sets for different positive displacement pumps (2), and / or different delivery fluid parameters (FP), preferably manually, in particular via a selection menu, selectable, are stored.

1 1. Control means according to one of the preceding claims,

characterized,

in that the logic means (7) for determining and / or signaling a

Maintenance due to the positive displacement pump (2) as a function of the first actual operating parameter (X) and / or at least one further actual operating parameters (X _H , YH _, YHH) and / or one for the the control means (5) associated positive displacement pump (2) specific Parameters are formed.

12. Control means according to one of the preceding claims,

characterized, in that the control means (5) are designed to communicate via a bus system, in particular a CAN bus system, and comprise a corresponding interface.

Control means according to one of the preceding claims,

characterized,

in that the control means (5) comprise memory means which are designed and controlled to provide the first actual operating parameters (X) and / or the at least one further operating parameters (X _H , YH _, YHH) and / or the reference variables (W) and / or store the comparison values and / or the limit values, preferably each with a time stamp.

Control means according to one of the preceding claims,

characterized,

in that input means, in particular in the form of at least one key, are provided for configuring the control means (5).

Control means according to one of the preceding claims,

characterized,

that signaling means, in particular a display and / or or at least one LED, in particular an LED traffic light are provided.

Positive displacement pump system comprising a positive displacement pump (2), a positive displacement pump motor (3) for driving the positive displacement pump (2), a frequency converter (4) associated with the positive displacement pump motor (3) and control means (5) upstream of the frequency converter (4) according to any one of the preceding claims, wherein the control means (5) are assigned Führungsgrößenvorgabemittel (8).

System according to claim 16,

characterized,

in that the reference variable presetting means (8) are designed as a process control station which is designed to monitor and / or control and / or regulate a plurality of system units, in particular positive displacement pumps (2).

18. System according to one of claims 16 or 17,

characterized,

in that a plurality of positive displacement pumps (2) are provided with associated control means (5).

19. System according to one of claims 16 to 1 8,

characterized,

the control means (5) with the process control station and / or a plurality of control means (5) are designed to communicate with one another via a bus system, in particular a CAN bus system.

20. System according to any one of claims 16 to 1 9,

characterized,

in that the control means (5) is signal-connected to at least one sensor for receiving the first actual operating parameter (X) and / or the at least one further measured actual operating parameter (XH, YH, YHH) and / or that the control means (5) signal conducting with the frequency converter (4) for receiving the first actual operating parameter (X) and / or the at least one further measured actual operating parameter (X _H , YH, YHH), in particular a positive displacement motor speed and / or a rotational frequency reference value of the frequency converter (4) and / or a torque setpoint of the frequency converter (4).

21. Method for controlling a frequency converter (4) of a positive-displacement pump motor (3) of a positive-displacement pump (2), in particular for operating control means (5) according to one of claims 1 to 14, wherein a control variable (Y _S ) for a controller (6) the frequency converter (4) of the positive-displacement pump motor (3) is generated as a function of a reference variable (W) and a first actual operating parameter (X), characterized in that logic means (7) associated with the controller (6) are used a first limit value (Y limit value, Ycrenzmin) is determined as a function of the first actual operating parameter (X) and at least one further actual operating parameter (XH, YH, YHH), the exceeding or falling below of which results in a defect state of the positive displacement pump (2) could have

and that a manipulated variable (Ys) or a corrected manipulated variable (Y's, Y "s) or a comparison value determined according to a functional relationship from the manipulated variable (Y _s ) or the corrected manipulated variable (Y ' _s , Y" s) with the at least one Limit value (YGrenzmax, YGrenzmin) is compared, and that, in the event that exceeds or falls below the at least one first limit value

(YGrenzmax, YGrenzmin) is detected by a certain amount, a corrected manipulated variable (Y ' _s , Y "s) will be output which preferably corresponds to a limit value (Y limit max, Ycrenzmin) determined by the threshold value setting means, and / or a second limit value (Y limit max , YGrenzmin) is determined as a function of the first actual operating parameter (X) and at least one further actual operating parameter (XH, YH, YHH) whose exceeding or falling below a negative impairment of a quality parameter of the conveying fluid conveyed with the positive displacement pump (2) could result

and that a manipulated variable (Ys) or a corrected manipulated variable (Y's, Y "s) or a comparison value determined according to a functional relationship from the manipulated variable (Y _s ) or the corrected manipulated variable (Y ' _s , Y" s) with the at least one second limit (YGrenzmax, Ycrenzmin) is compared, and that for the

If an overshoot or undershooting of the at least one second limit value (Y limit value, Ycrenzmin) is determined by a certain amount, a corrected manipulated variable (Y's, Y "s) will be output, which preferably corresponds to a limit value (Y limit max) determined by the second limit value specifying means; Ycrenzmin).