DE19804330A1 - Process for regulating a compressor - Google Patents

Abstract

The invention relates to method and device (1) for regulating at least one delivery quantity of a compressor unit (2) driven by an electric drive motor, such as the volume flow, the pressure and/or the temperature of a medium delivered by said compressor unit (2). At least one measured value is established for the delivery quantity and compared with a specified or limiting value, and, when a deviation occurs, the rotational speed of the drive shaft of the compressor is altered. The measured value of the delivery quantities is indirectly determined by establishing actual values of at least two alternative quantities, such as for example, the motor input power and the rotational speed pertaining to the rotating field of the drive motor. In addition, motor-specific and compressor-specific characteristic quantities are determined from the alternative quantities. Said characteristic quantities are stored in a data storage (5) and have a plurality of value combinations respectively comprised of a value for the delivery quantity and of a value for each of the alternative quantities of the measured value of the delivery quantities. The motor-specific and compressor-specific characteristic quantities can be filed as a characteristic diagram in the data storage.

Description

The present invention relates to a method for regulating the pressure and / or caused by a compressor on a pumped medium the volume flow of the medium and / or the temperature of the compressed delivery medium, at least one pressure and / or Volume flow value and / or temperature value determined and with a Setpoint or a limit value compared and in the event of a deviation the speed of the drive shaft of the compressor is changed. Here becomes a pressure of either an absolute pressure of the medium or one caused by the compressor on the pumped medium Pressure difference understood.

The invention also relates to a device for Carrying out the procedure using a compressor for Pumped medium and a compressor unit having a drive motor, the drive motor with a power control for Setting whose speed is associated with a Control connection is that a regulator for regulating one of the Compressor on the pumped medium caused pressure and / or Volume flow of the medium and / or the temperature of the compressed medium. Also regarding the device becomes either an absolute pressure of the medium under pressure  or one caused by the compressor on the pumped medium Pressure difference understood.

One already knows a method and a device of the beginning mentioned type, in which the medium flow rate is one of medium compressed by the compressor by means of a controller is held. This involves changes in one to the compressor connected system flowed through by the medium compensates that the actual value of the medium flow is measured and in the event of a deviation from a target value, the speed of the Drive shaft of the compressor is changed accordingly. Here If the volume flow decreases, the speed of the Drive shaft increases and with an increase in volume flow the Speed reduced accordingly, so that regardless of Operating point of the system is a constant volume flow results. Is unfavorable in the previously known method and However, device that the for measuring the respective volume flow Actual value required sensor is still comparatively complex.

A method and a device are already known type mentioned in which the between the inlet and the Outlet of the compressor occurring pressure drop on the medium is kept constant. This is the actual value of the pressure drop measured with a differential pressure sensor and the speed of the Drive shaft of the compressor if the actual value deviates adjusted accordingly from a predetermined target value. Also the problem here is that for the actual value measurement required sensor technology is still comparatively complex.

It is also already known the temperature of the exhaust gas flow medium compressed by a compressor with a temperature sensor monitor and when a temperature is reached or exceeded Limit value the speed of the drive shaft of the compressor reduce to overheating of the compressor or any of the Prevent compressor downstream system. This too  The method and the corresponding device are still comparative complex.

There is therefore the task of a method and a device of the kind mentioned at the beginning to create a simple rules of the volume flow and / or the temperature of the compressed medium and / or one of the compressor the pressure medium or a pressure difference enables.

In the above-mentioned procedure for regulating the medium Volume flow, the solution to this problem is that compressor-specific parameters with a multitude of values combinations consisting of pressure, Speed and volume flow values determined and saved be that the volume flow measured value is determined indirectly by Actual values for one caused by the compressor on the pumped medium Pressure and for the speed of the drive shaft of the compressor is detected and from these actual values with the help of the saved Characteristics of the volume flow measured value is determined.

This advantageously makes it possible to control the volume flow of the pumped medium indirectly from a pumped medium pressure or -Pressure difference and the speed of the drive shaft of the compressor to determine, so that a complex and expensive volume flow sensor can be saved. First, for a variety of Pressure and speed values each assigned to these values Volume flow value determined and saved. The corresponding Combinations of values can be done, for example, by means of an experiment can be measured experimentally. Despite this, apparently unnecessary effort results in a significant simplification of the Procedure, since the compressor-specific value combinations for a certain type of compressor can only be determined once and then again and again to calculate the volume flow the respective speed and pressure actual values can be used  can.

The above-mentioned object can be used in a method for regulating of the volume flow rate can also be solved in that compressor-specific parameters with a multitude of values combinations consisting of mutually assigned Drive power, speed and volume flow values determined and stored that the volume flow measured value indirectly is determined by using actual values for the drive power of the Compressor and the speed of the compressor drive shaft detected and from these actual values with the help of the saved Characteristics of the volume flow measured value is determined. The volume flow can also from the drive coupled into the compressor power and the speed of the compressor can be determined, whereby a volume flow sensor can also be saved.

In a method of controlling the flow from one compressor to another Pumped medium caused pressure is the solution to the above mentioned task in that compressor-specific parameters with a multitude of value combinations consisting of each other assigned drive power, speed and pressure values can be determined and stored that the pressure reading indirectly is determined by actual values for the drive power and speed the drive shaft of the compressor can be detected and from these Actual values are determined using the parameters of the pressure measured value. It is therefore possible to connect one of the compressors to the Pumped medium caused pressure or a pressure difference caused thereon indirectly by measuring the injected into the compressor Drive power and the speed of the drive shaft of the compressor to determine. This advantageously enables a pressure sensor or a pressure difference sensor can be saved.

In the aforementioned method for regulating the temperature of the compressed medium, subsequently also briefly exhaust gas temperature  called, the solution to the above problem is that compressor-specific parameters with a multitude of values combinations consisting of mutually assigned Drive power, speed and fluid temperature values be determined and stored that the medium temperature Measured value is determined indirectly by using actual values for the drive power and the speed of the drive shaft of the compressor detected and from these actual values the measured medium temperature is determined. The exhaust gas temperature of the medium is thus indirectly from the drive power and the speed of the drive shaft of the compressor determined, whereby a fluid temperature sensor can be saved.

The above-mentioned methods can be carried out both in vacuum and can also be used in the compression mode of the compressor.

In a method according to at least two of claims 2 to 4 provided that of the control variables fluid volume flow, pressure or pressure difference and temperature of the compressed medium at least a first and a second controlled variable are regulated, that during the duration of a deviation of the first controlled variable from the predetermined control of the second setpoint range The controlled variable is deactivated and that during this period the speed of the drive shaft of the compressor is changed until the first controlled variable is again within the setpoint range located. So it is a superordinate regulation for a first one Controlled variable and a subordinate regulation for a second Control variable provided. This control procedure can, for example in conveyor systems in which a powder medium is present in a gas stream is promoted, applied to advantage. Such conveyors are usually operated with constant delivery pressure. At a blockage in the conveyor system can, however, be useful be to increase the delivery pressure for a short time in order to Blowing away the plug of powder medium located. In this case, a predetermined setpoint range for the pressure can  or the differential pressure can be ensured that the pressure or the differential pressure does not exceed a maximum value and thus the system is not overloaded.

So that the maximum permissible temperature of the outlet side Pumped medium and / or the compressor at none of the above mentioned types of regulation is exceeded, it is advantageous if the temperature of the compressed medium is determined and is compared with a temperature limit and if the If the temperature limit exceeds the performance of the compressor to limit the temperature of the compressed medium the temperature limit is reduced.

It is even possible that the temperature limit of one is reduced to a lower limit when the Temperature of the compressed medium is the upper limit for exceeds a predetermined or predeterminable first time period and that the temperature limit from the lower to the upper Limit is increased when the temperature reaches the lower temperature Limit value for a predefined or predefinable second time period falls below. It has been shown that the temperature of the compressed medium for a short time above the maximum permissible continuous temperature can be increased without the compressor Suffered damage.

A particularly advantageous embodiment of the invention provides that the drive shaft of the compressor from an electrical Drive motor is driven and that the drive power of the Drive shaft indirectly by detecting the motor current and the Speed of the drive motor is determined. The drive power can thereby be particularly simple, for example by means of a shunt or an inductive current transformer.

It is particularly advantageous if a frequency is used as the drive motor controlled electric motor is used and when the speed of the  Drive shaft indirectly from the operating frequency of the electric motor is determined. With an asynchronous motor, the speed of the Drive shaft from operating frequency and slip, for example of the asynchronous motor can be derived. With a synchronous motor the speed of the drive shaft proportional to the operating frequency of the synchronous motor. Thus, the speed can be particularly simple Be determined from the operating frequency.

A preferred embodiment of the invention provides that for different temperatures of an inlet-side medium and / or different ambient temperatures different compressor-specific parameters are provided and that for Selection of the parameter assigned to the respective temperature Temperature of the inlet-side pumped medium measured and / or is specified. This can reduce the thermodynamic properties of the medium are better taken into account, whereby the Control accuracy of the process with different medium Temperatures and / or ambient temperatures is improved. The Temperature of the delivery medium on the inlet side can, for example measured or specified based on experience.

It is advantageous if the compressor-specific parameters as Family of curves can be saved. This allows the physika mical properties of the compressor simulated in a simple manner become. In addition, only one is used to save the family of curves comparatively small amount of data required.

This enables a particularly simple set of characteristic curves achieved that at least one characteristic curve through a straight line is approximated. With non-linear compressor parameters, it can be advantageous if at least one characteristic of the Characteristic family by a polynomial, in particular by a polynomial second degree is approximated.

It is advantageous if for an actual value determined by  Interpolation from neighboring combinations of values and / or characteristic curves an intermediate value or characteristic is determined. The The accuracy of the control can be increased without additional combinations of values or compressor characteristics must be measured and saved.

So that the maximum permissible engine power for none of the above mentioned types of regulation is exceeded, it is advantageous if the power consumption of the motor is limited. It is even possible that immediately before reaching the maximum allowable Engine power the engine speed is reduced until a certain safety distance from the maximum allowable There is engine power. By limiting engine power in particular prevents the compressor from an operating point reached, with an overload protection of the motor activated and thus the engine is switched off.

Regarding the above-mentioned device with a controller for Regulating the flow rate of the medium is the solution Above task in that as a sensor for indirect Measurement of the volume flow rate provided a pressure sensor is for measuring one of the compressors on the pumped medium caused pressure is arranged that the control device a Has data storage in which compressor-specific parameters with a A multitude of value combinations consisting of each other assigned pressure, speed and volume flow values and / or Drive power values are stored, and that the Steuerein Direction for the indirect determination of the volume flow from the measured pressure, the speed and the compressor-specific Characteristics associated with the data store. In advantageous In this way, a conveying volume flow sensor can be saved become.

Regarding the above-mentioned device with a controller for Controlling the volume flow rate can be the above  Task can also be solved in that as a sensor for indirect Measurement of the volume flow rate of a drive power Sensor is provided that the control device a data has in the compressor-specific parameters with a A multitude of value combinations consisting of each other assigned drive power, speed and volume flow values are stored, and that the control device for indirect determination the volume flow from the measured drive power, the speed and the compressor-specific parameters with the data memory connected is. The volume flow rate is therefore indirect from the drive power and speed of the drive shaft of the Compressor determined, so that a complex and expensive Volume flow sensor can be saved.

In the device mentioned at the beginning with a controller for regulating a pressure caused by the compressor on the pumped medium the above object achieved in that as a sensor a drive power sensor for indirect measurement of pressure it is provided that the control device has a data memory, in which compressor-specific parameters with a variety of Combinations of values each consisting of mutually assigned Drive power, speed and pressure values are stored, and that the control device for indirectly determining the pressure the measured drive power, the speed and the compressor specific parameters is connected to the data storage. Consequently a pressure or pressure difference sensor can be saved.

In a device of the type mentioned above with a controller to regulate the temperature of the compressed medium The above object is achieved in that as a sensor for indirect Measurement of the fluid temperature of the compressed fluid a drive power sensor is provided that the control unit direction has a data memory in which compressor-specific Characteristics with a multitude of value combinations consisting of each associated drive power, speed and  Fluid temperature values are stored, and that the Steuerein direction for indirect determination of the temperature of the fluid the measured drive power, the speed and the compressor specific parameters is connected to the data storage. Thereby can use a temperature sensor to measure the temperature of the compressed Pumped medium can be saved.

A device according to at least two is particularly advantageous of claims 17 to 19, in particular according to claims 17 and 18 and 19. With such a device, for example, one of the Controlled variables are regulated according to a specified reference variable are, while the other control variables by means of a superordinate Regulation to be held in a window to the over or Falling below the limit values assigned to these controlled variables thus overloading the compressor unit and / or one of them to avoid connected system.

It is advantageous if the drive motor is an electric motor and if the drive power sensor is a current sensor for measurement of the motor current. The speed of the rotor of the electric motor can then be measured using a tachometer generator, for example be so that from the speed and the motor current to simple Way the drive power coupled into the compressor can be determined.

In a preferred embodiment of the invention, that the power control for controlling a frequency converter of the electric motor. The speed of the electric motor can then sensorless from the operating frequency of the frequency converter be determined.

It is advantageous if for different temperatures different compressor-specific Characteristics are stored in the data memory. The device can then even better to different systems and / or modes of operation  be adjusted by depending on the temperature range of each Application of the corresponding compressor-specific parameters, can be selected on the basis of empirical values, for example.

It is particularly advantageous if the control device is available for selection that of the respective temperature of the delivery medium on the inlet side assigned compressor-specific parameters with a medium Temperature sensor is connected. The compressor-specific parameters can then be selected automatically depending on the fluid temperature become.

It is advantageous if the value combinations of the compressor-specific fish parameters stored as a family of curves in the data memory are. Support points can then be stored in the data memory, for example for the individual characteristic curves, which are stored in The characteristic curves can be combined with a corresponding calculation rule define. Of course, the characteristic curves can also be set to another way, for example by means of data stored in the data memory Coefficients of a polynomial or a straight line equation defined be.

It is particularly advantageous if at least one characteristic curve of the Characteristic family of points stored in the data memory is defined and if at least one of these support points usable characteristic range of the characteristic is limited. From the Support points can then be calculated using an appropriate calculation any points on the characteristic curve determined become. At the same time, the support points serve the usable Limit the range of characteristics, so that an overload of the Device and / or overriding operating parameters avoided is.

It is advantageous if the data memory has at least two data has storage areas in which compressor-specific Parameters are stored for different types of compressors, and  if the data storage areas to adapt the data storage can be switched to the type of compressor used. Thereby it is possible to use different types of compressors with the same To operate control device, so that the manufacturing and Reduce spare parts storage costs for the device accordingly. The data storage areas can be switched, for example hardware by means of microswitches, removable bridges or the same coding device.

It is particularly advantageous if the device has an interface for storing compressor-specific parameters in the Data storage and / or to select a compressor type assigned data storage area with compressor-specific Has characteristics. So by means of the interface compressor-specific parameters written in the data memory so that different types of compressors with the same Control device can be operated. The compressor spec Fish parameters can, for example, on a data carrier be saved and by means of one with the interface connecting microcomputers are written into the data memory. The control device can thereby each on site with the compressor to be combined can be individually adapted. In addition, the compressor can be easily repaired replaced and if necessary by a compressor of another type be replaced.

In the case of a device with a programmable controller, the Interface can also be used to select a control program. This allows the control characteristic of the control device to the respective properties of a connected to the device Plant can be customized.

Overall, this results in a device that is both in one closed, as well as in an open medium cycle can be used. The device allows in one  closed fluid circuit a regulation or a Limitation of the volume flow from the compressor at the pressure medium caused or a pressure caused thereon Pressure difference and / or the temperature of the outlet side Medium. With an open medium cycle the device regulates or limits the medium Volume flow, one caused by the compressor on the medium Differential pressure or the absolute medium pressure and / or the temperature of the discharge medium. Both can with an open as well as with a closed medium Circuit set a desired control characteristic are used, whereby application limit values can also be taken into account.

Below are exemplary embodiments of the invention based on the Drawing explained in more detail. Show it:

Fig. 1 is a block diagram of an apparatus having what is called a system compressor unit and a controller for controlling the conveying medium volume flow, which is determined indirectly from the operating frequency of the electric drive motor of the compressor unit and the motor current,

Fig. 2 is a block diagram of an apparatus having what is called a system compressor unit and a controller for controlling the conveying medium absolute pressure, which is determined indirectly from the operating frequency of the electric drive motor of the compressor unit, the motor current and the measured ambient pressure,

Fig. 3 is a block diagram of a device that has a system called a compressor unit connected to an open medium circuit and a controller for regulating its medium volume flow, which indirectly from the operating frequency of the electric drive motor of the compressor unit and the pressure difference caused on the medium is determined

FIG. 4 shows a block diagram of a device similar to FIG. 3, but with the compressor unit connected to a closed fluid circuit;

Fig. 5 is a graphical representation of a family of characteristics having a plurality of respective different compressor At output speeds associated characteristics is gen wherein aufgetra on the abscissa of the feed medium flow rate and on the ordinate the pressure differential across the pumping medium,

Fig. 6 is a view similar to FIG. 5, but plotted on the abscissa, the drive power and the ordinate the conveying medium volume flow,

Fig. 7 is a view similar to FIG. 6, except that applying on the ordinate the pressure difference,

Fig. 8 is a block diagram of a device similar to Fig. 1, wherein to limit the pressure difference caused on the medium, this is determined indirectly from the operating frequency of the electric drive motor of the compressor unit and the motor current and is compared with a limit value which regulates the flow rate of the medium restricts

Fig. 9 is a block diagram of a device similar to FIG. 1, but the compressor unit is connected to an open delivery medium circuit and is measured for limiting the flow medium-pressure of a pressure sensor and compared with a limit value,

Fig. 10 is a block diagram of a device similar to FIG. 9, but the compressor unit is connected to a closed conveying medium circuit,

FIG. 11 shows a representation similar to FIG. 6, but a minimum value Q _min is additionally provided for the volume flow rate of the conveyed medium,

FIG. 12 shows a representation similar to FIG. 7, but a maximum value Δp _max is additionally provided for the differential pressure,

Which restrict Fig. 13 is a block diagram of a device similar to FIG. 1 except that threshold values are predetermined for the temperature of the exhaust gas discharged from the compressor medium, the control of the conveying medium volume flow,

FIG. 14 shows a block diagram of a device similar to FIG. 3, but with limit values for the exhaust gas temperature of the medium conveyed by the compressor being specified, which limit the regulation of the volume flow rate;

Which limit similar to Fig. 15 is a block diagram of an apparatus Fig. 4, however, limits are set for the temperature of the exhaust gas discharged from the compressor medium, the control of the conveying medium volume flow,

FIG. 16 shows a representation similar to FIG. 5, but in addition a temperature characteristic for the maximum exhaust gas temperature is specified, which limits the volume flow pressure difference characteristics,

Fig. 17 is a graphical representation of a family of characteristics having a plurality of approximated by straight lines respectively associated difference union compressor drive speed characteristic curves, in which the abscissa of Fördermedium- volume flow and on the ordinate the pressure difference is applied on the conveying medium,

Fig. 18 is a view similar to FIG. 17, but shown on the abscissa, the drive power and the ordinate the conveying medium volume flow,

Fig. 19 is a view similar to FIG. 18, but the pressure difference is plotted on the ordinate,

FIG. 20 shows a representation similar to FIG. 17, but with the characteristic curves being approximated by a second degree polynomial, FIG.

FIG. 21 shows a representation similar to FIG. 18, but with the characteristics being approximated by a second degree polynomial and

FIG. 22 shows a representation similar to FIG. 19, but the characteristic curves are approximated by a second degree polynomial.

The devices shown in FIGS. 3 and 4, generally designated 10 , have a compressor unit 11 with a compressor and a drive motor, which is connected to a power control for setting its drive speed. The power control is in control connection with a control device which has a controller 12 for regulating the volume flow of the medium. In the embodiment shown in Fig. 3 game, the compressor is connected to an open medium circuit and in the embodiment of FIG. 4 with a closed medium circuit.

To regulate the volume flow of the compressor, a volume flow measured value Q is compared with a volume flow setpoint Q _v and if there is a deviation, the speed n of the drive shaft of the compressor is changed. In this case, if the volume flow measured value Q is greater than the setpoint Q _v , the speed is reduced and if the measured value Q is smaller than the setpoint Q _v , the drive speed n is increased. If the measured value Q agrees with the setpoint Q _v , the speed is maintained.

The volume flow measured value is determined indirectly from a pressure difference measured by means of a pressure or pressure difference sensor 13 on the pumped medium and the speed of the drive shaft of the compressor, thereby saving a volume flow sensor. For this purpose, the control device has a data memory 14 in which compressor-specific parameters with a multiplicity of value combinations, each consisting of pressure difference, speed and volume flow values assigned to one another, are stored.

As can be seen from FIG. 5, the compressor-specific parameters stored in the data memory 14 are approximated by a family of characteristic lines with compressor characteristics 3 . With the aid of this characteristic curve 3 , the control device assigns a volume flow value to a pair of values having a pressure difference and a speed value.

The sequence of the volume flow control is explained below using the example of the operating points P1, P2 and P3 in FIG. 2 for the device 10 shown in FIGS. 3 and 4. This feeds a system that has system characteristics 1 and 2 . P1 is the operating point on the system characteristic 1 and a compressor characteristic 3 assigned to the speed n _o . At operating point P1, the volume flow rate corresponds to a predetermined volume flow setpoint Q _v . Characteristic line 2 arises due to changes in the system. The operating point then moves on the compressor characteristic curve 3 for the speed n _o to point P2. At point P2, the control device determines from the compressor characteristic curve 3 that the volume flow measured value is too small, whereupon the speed of the drive shaft of the compressor is increased until the volume flow setpoint Q _v is reached again. The operating point then moves from P2 to P3 on the system characteristic curve 2 .

In the embodiment shown in FIG. 1, the device 10 has a compressor unit 11 with a compressor driven by an electric synchronous motor. To set the drive speed, the synchronous motor is connected to a power control unit that has a frequency converter. The power control is in control connection with a control device which has a regulator 12 for regulating the volume flow of the medium.

A is used to regulate the flow rate of the compressor Volume flow measured value compared with a volume flow setpoint and in the event of a deviation, the speed of the synchronous motor or Compressor drive shaft changed. The volume flow measured value is indirectly derived from the operating frequency of the synchronous motor derived drive speed of the compressor drive shaft and drive measured by means of a motor current measuring device Power of the synchronous motor determined. This creates a volume flow Sensor saved.

The control device has a data memory 14 in which compressor-specific parameters with a large number of value combinations, each consisting of drive power, speed and volume flow values, are stored. As can be seen from FIG. 6, the compressor-specific parameters stored in the data memory 14 are approximated by a family of curves with compressor curves 4 . With the aid of these characteristic curves 4 , the control device in each case assigns a volume flow value to a pair of values having an engine speed and an engine power value.

The flow of the volume flow control is explained below using the example of the operating points P1, P2 and P3 in FIG. 6 for a system operated with the device 10 , which has the system characteristics lines 1 and 2 . The point P1 is the operating point on the system characteristic 1 and a compressor characteristic 4 assigned to the speed n _o . At the operating point P1, the volume flow rate corresponds to a predetermined setpoint Q _v . Characteristic curve 2 arises due to changes in the system. The operating point then moves on the compressor characteristic curve 4 for the speed n _o to point P2. The control device determines the volume flow Q assigned to the point P2 and compares it with the setpoint Q _v . Since the determined volume flow Q is smaller than the target value Q _v , the speed is increased until the volume flow has again reached the target value Q _v . The operating point moves from P2 to P3 on system characteristic curve 2 .

The control device having the controller 12 has a serial interface with which the control characteristic of the controller 12 can be switched over in software. Various control variants, such as volume flow control, pressure control and / or exhaust gas temperature control, can be set.

For the pressure control, the compressor characteristic curves 5 shown in FIG. 4 are stored in the data memory 14 , which have a large number of value combinations, each consisting of drive power, speed and pressure difference values assigned to one another. The compressor characteristics 5 are approximated by straight line sections.

The sequence of the pressure control is explained in more detail below with the aid of points P1, P2 and P4 in FIG. 7. The point P1 is the operating point on the system characteristic 1 and the compressor characteristic 5 assigned to the speed n _o . At operating point P1, the differential pressure of the pumped medium corresponds to a predetermined differential pressure setpoint Δp _v . Characteristic curve 2 arises due to changes in the system. The operating point then moves on the compressor characteristic curve 5 for the speed n _o to point P2. At point P2, the control device determines the pressure difference assigned to point P2 from the compressor characteristic curve 5 and compares it with the setpoint value Δp _v . Since the differential pressure at operating point P2 is greater than the target value Δp _v , the speed of the drive motor is reduced until the differential pressure target value Δp _v is reached again. The operating point on plant characteristic line 2 moves from P2 to P4.

With the method or the device 10 described above, the pressure of the conveyed medium can be regulated to a constant target value Δp _v without the use of a pressure sensor, regardless of the _particular system characteristic. The pressure control can be used both with a closed ( FIG. 1) and with an open ( FIG. 2) conveying medium circuit. The differential pressure in a closed circuit can, for example, correspond to the difference between the pressure of the pumped medium on the pressure side and that on the suction side of the compressor. In the case of an open conveying medium circuit, the pressure difference can correspond, for example, to the difference between the conveying medium pressure on the compressor pressure side and the ambient pressure during pressure operation.

The control characteristic of the device 10 can also be set such that one or more limit values are specified for the differential pressure or the volume flow, which limit the range of characteristics for a specific control variant. If the limit value (s) is still exceeded or fallen below, the compressor is returned to the range defined by the limit value (s) based on the characteristic curves 3 , 4 , 5 by changing the speed. Only then is the old control variant reactivated ( Fig. 8, 9, 10).

This is explained below using the example of a differential pressure control with a predetermined minimum volume flow Q _min on the basis of the operating points P1, P2, P3 in FIG. 10. The point P1 is the operating point on the system characteristic 1 and the compressor characteristic 4 for the speed n _o . At operating point P1, the volume flow corresponds to a predetermined volume flow setpoint Q _v . Characteristic curve 2 arises due to changes in the system. The operating point then moves on the compressor characteristic curve 4 for the speed n _o to point P2. The control device determines from the engine speed and the engine power at P2 a volume flow that is too small ( FIG. 7) and an excessively large pressure difference ( FIG. 4). Since the volume flow control is superimposed on the pressure control and thus the volume flow limit Q _{min has} priority over the pressure difference setpoint Δp _v , the control unit increases the speed until the volume flow limit Q _{min is} reached. The operating point on plant characteristic curve 2 moves from P2 to P3. The pressure control is only reactivated when the volume flow limit Q _{min is} reached.

The control characteristic of the device 10 can also be set such that one or more limit values are specified for a volume flow control for the differential pressure, which is explained below using the example of the operating points P1, P2 and P3 in FIG. 8. The point P1 is an operating point on the system characteristic 1 and the compressor characteristic 5 for the speed n _o . At the operating point P1, the volume flow rate corresponds to a predetermined setpoint Q _v . Characteristic curve 2 arises due to changes in the system. The operating point then moves on the compressor characteristic curve 5 for the speed n _o to point P2. There, the control device determines an excessively large pressure difference ( FIG. 12) and an excessively small volume flow ( FIG. 6) from the engine speed and the engine power. Since the pressure difference limit value Δp _{max has} priority over the lower-level volume flow control, the control unit reduces the speed until the pressure difference limit value Δp _{max is} reached. The operating point on plant characteristic curve 2 moves from P2 to P3. When the pressure difference limit Δp _max is reached, the volume flow control is reactivated.

A maximum permissible limit value of the exhaust gas temperature T _max may not be exceeded for any control variant or fixed speed. If the limit value is nevertheless exceeded, the compressor is returned to the permitted temperature range based on the compressor characteristic curves 3 , 4 , 5 by changing the speed. Only then is the old control variant (e.g. pressure difference and / or volume flow control) reactivated ( Fig. 13, 14, 15).

The sequence of the control when limiting the exhaust gas temperature of the conveyed medium is explained in more detail below with the aid of the operating points P1, P2 and P3 in FIG. 16. The permitted characteristic curve area of the individual characteristic curves 5 is limited by a temperature limit characteristic curve 6 , which in each case intersects a characteristic curve end point 7 of the individual characteristic curve 5 . The point P1 is an operating point on the system characteristic 1 and the compressor characteristic 5 for the speed n _o . Characteristic curve 2 arises due to changes in the system. The operating point then moves on the compressor characteristic curve 5 for the speed N ₀ to point P2. The control device determines an excessively high exhaust gas temperature from the engine speed and the engine power or the pressure or the pressure difference at P2. Since the regulation of the temperature level T _max has precedence over flow and / or pressure control and / or speed control, the control device reduces the rotational speed until the temperature limit value t _max is reached again. The operating point moves from P2 to P3 on system characteristic curve 2 . Only then is the volume flow and / or pressure and / or speed control reactivated.

The data memory 14 of the control unit has a plurality of memory areas in which families of characteristic curves for different types of compressors are stored. In order to adapt the data memory 14 to the compressor type assigned to it, the data memory areas can be switched over in software via the serial interface. As a result, the same control device can be used for a large number of different compressors, which simplifies the production and storage of the control device.

The compressor characteristics 3 , 4 , 5 are stored in the data memory 14 as a family of compressor characteristics with combinations of values, each consisting of a pressure difference, a volume flow, a speed and a drive power value. Each of the families of characteristic curves has separate compressor characteristic curves 3 , 4 , 5 for vacuum and pressure operation of the compressor, for different medium suction temperatures and for different drive speeds.

Depending on the type of compressor, the characteristics are approximated either by straight lines ( Fig. 17, 18, 19) or by second degree polynomials ( Fig. 20, 21, 22). The equations for the compressor characteristics and various solution algorithms for this are stored in the control device. In the data memory 14 , the starting point A _n and the end point C _{n of} the characteristic are stored for a straight compressor characteristic curve and an intermediate point B _{n is also} stored for a second degree polynomial. From these points, the value combinations of the compressor characteristic curves 3 , 4 , 5 are determined online by the control device using the compressor equations. The characteristic curve points stored in the data memory for a family of compressor characteristic curves are shown in the following table, in which the temperature values of the medium on the suction side are abbreviated with T, the speed values with n, the drive power values with P and the pressure difference values with Δp:

In order to limit the number of stored compressor characteristic curves 3 , 4 , 5 and still enable precise control of the variables pressure difference, speed, volume flow and / or exhaust gas temperature, the control device for pressure difference, speed, volume flow and / or Drive power / actual value combinations that are not on a stored characteristic curve are determined by interpolating intermediate characteristic curves 3 ', 4 ', 5 '( FIGS. 5, 7, and 11). The start and end values of the intermediate characteristic curves and, if appropriate, the intermediate values from the initial values A _n , the end values C _n and, if appropriate, the intermediate values B _{n of} the compressor characteristic curves 3 , 4 , 5 adjacent to the intermediate characteristic curve are determined. The value combinations assigned to the intermediate characteristic curve are then calculated from the determined start, end and intermediate values.

Overall, this results in a method and a device 10 for controlling at least one controlled variable of a compressor unit, such as, for example, the volume flow, the pressure difference and / or the exhaust gas temperature of a medium compressed by the compressor unit. At least one measured value is determined for the controlled variable and compared with a target or limit value, and in the event of a deviation, the speed of the drive shaft of the compressor is changed. The measured value is determined indirectly by determining actual values of at least two substitute variables, such as, for example, the speed of the compressor drive shaft and its drive power, and from the substitute variables using compressor-specific parameters stored in a data memory 14 with a multitude of combinations of values, each consisting of one value the measured value is determined for the controlled variable and one value for each of the substitute variables. This saves one sensor for measuring the controlled variable.

Claims (30)

1. A method for controlling the volume flow of a compressor, wherein at least one volume flow measured value is determined and compared with a volume flow setpoint or limit value and in the event of a deviation the speed of the drive shaft of the compressor is changed, characterized in that compressor-specific parameters are included a large number of combinations of values, each consisting of pressure, speed and volume flow values which are assigned to one another, are determined and stored so that the volume flow measurement value is determined indirectly by actual values for a pressure caused by the compressor on the delivery medium and for the speed of the Drive shaft of the compressor are detected and the volume flow measured value is determined from these actual values with the aid of the stored parameters. 2. The method according to the preamble of claim 1, characterized characterized in that compressor-specific parameters with a multitude of value combinations consisting of each associated drive power, speed and Volume flow values are determined and saved that the volume flow measured value is determined indirectly by Actual values for the drive power of the compressor and the Speed of the compressor drive shaft can be detected and off these actual values with the help of the stored parameters of Volume flow measured value is determined. 3. Procedure for regulating the from one compressor to one Pumped medium caused pressure, at least one pressure Measured value determined and with a pressure setpoint or limit value compared and in the event of a deviation the speed of the drive shaft of the compressor is changed, characterized in that that compressor-specific parameters with a variety of  Combinations of values each consisting of mutually assigned Drive power, speed and pressure values determined and be saved so that the measured pressure value is determined indirectly by adding actual values for the drive power and the speed the drive shaft of the compressor can be detected and from these actual values with the help of the parameters the pressure measured value is determined. 4. Procedure for regulating the temperature of a compressor compressed delivery medium, with at least one delivery measured medium temperature and with a medium temperature setpoint or limit value compared and at a Deviation the speed of the drive shaft of the compressor is changed, characterized in that compressor specific parameters with a multitude of values combinations consisting of mutually assigned Drive power, speed and fluid temperature values be determined and stored that the medium Temperature measured value is determined indirectly by actual values for the drive power and the speed of the drive shaft of the compressor can be recorded and from these actual values the Fluid temperature measured value is determined. 5. The method according to at least two of claims 1 to 4, characterized characterized in that of the controlled quantities of the medium volume current, fluid pressure and temperature of the compressed Medium at least a first and a second controlled variable be regulated that during the period of a deviation of the first controlled variable from a predetermined setpoint range Regulation of the second controlled variable is deactivated, and that during this period the speed of the drive shaft of the compressor is changed until the first controlled variable is again within the setpoint range. 6. The method according to any one of claims 1 to 5, characterized  records that the temperature of the compressed medium is determined and compared with a temperature limit and that when the temperature limit is exceeded the Performance of the compressor to limit the temperature of the compressed medium to the temperature limit is reduced. 7. The method according to claim 6, characterized in that the Temperature limit from an upper to a lower one Limit is reduced when the temperature of the compacted Medium the upper limit for a given or predeterminable first time period and that the Temperature limit from the lower to the upper limit is increased when the temperature reaches the lower temperature Limit value for a predefined or predefinable second time period falls below. 8. The method according to any one of claims 1 to 7, characterized records that the drive shaft of the compressor from a electric drive motor is driven and that the Drive power of the drive shaft indirectly through detection of the motor current and the speed of the drive motor is determined. 9. The method according to any one of claims 1 to 8, characterized records that as a drive motor a frequency controlled Electric motor is used and that the speed of the drive wave indirectly from the operating frequency of the electric motor is determined. 10. The method according to any one of claims 1 to 9, characterized records that for different temperatures of a delivery medium and / or different environment temperatures different compressor-specific parameters are provided and that for the selection of the respective  Characteristics assigned to the temperature of the inlet-side pumped medium is measured and / or specified. 11. The method according to any one of claims 1 to 10, characterized shows that the compressor-specific parameters as Family of curves can be saved. 12. The method according to any one of claims 1 to 11, characterized in that at least one characteristic ( 3 , 4 , 5 ) of the family of characteristics is approximated by a straight line. 13. The method according to any one of claims 1 to 12, characterized in that at least one characteristic ( 3 , 4 , 5 ) of the family of characteristics is approximated by a polynomial, in particular by a second-line polynomial. 14. The method according to any one of claims 1 to 13, characterized in that an intermediate value or an intermediate characteristic ( 3 ', 4 ', 5 ') for a determined actual value by interpolation from adjacent combinations of values and / or characteristic curves ( 3 , 4 , 5 ) ) is determined. 15. The method according to any one of claims 1 to 14, characterized records that the power consumption of the engine is limited. 16. The apparatus for performing the method according to claim 1, with a compressor for the pumped medium and a drive motor having a compressor assembly, the drive motor being connected to a power control for setting its speed, which is connected to a controller ( 12 ) for regulating the flow medium volume flow having control device in control connection, characterized in that a pressure sensor ( 13 ) is provided as a sensor for the indirect measurement of the conveying medium volume flow, which is arranged to measure a pressure caused by the compressor on the conveying medium that the control device Data memory ( 14 ) has stored in the compressor-specific parameters with a large number of combinations of values, each consisting of mutually assigned pressure, speed and volume flow values, and that the control device for indirectly determining the volume flow from the measured pressure, the speed and the compressor-specific parameters are connected to the data memory ( 14 ). 17. The device according to the preamble of claim 16, for carrying out the method according to claim 2, characterized in that a drive power sensor is provided as a sensor for indirect measurement of the conveying medium volume flow, that the control device has a data memory ( 14 ), in which compressor-specific parameters are stored with a multitude of value combinations consisting of drive power, speed and volume flow values assigned to each other, and that the control device for the indirect determination of the volume flow from the measured drive power, the speed and the compressor-specific parameters with the data memory ( 14 ) is connected. 18. Device for performing the method according to claim 3, with a compressor for the pumped medium and a drive motor having a compressor unit, the drive motor being connected to a power control for setting its speed, which is connected to a controller ( 12 ) for regulating the compressor is connected to the control medium in the control medium, which has the effect of pressure, characterized in that a drive power sensor is provided as a sensor for indirect measurement of the pressure, that the control device has a data memory ( 14 ) in which compressor-specific parameters with a large number of combinations of values exist are stored from each associated drive power, speed and pressure values, and that the control device for the indirect determination of the pressure from the measured drive power, the speed and the compressor-specific parameters with the data memory ( 14 ) ver is bound. 19. The apparatus for performing the method according to claim 4, with a compressor for the pumped medium and a drive motor having a compressor unit, the drive motor being connected to a power control for setting its speed, which is connected to a controller ( 12 ) for regulating the temperature of the the compressor compressed medium is in control connection, characterized in that a drive power sensor is provided as a sensor for the indirect measurement of the medium temperature of the compressed medium that the Steuerein direction has a data memory ( 14 ) in the compressor-specific parameters with a variety of combinations of values consisting of mutually assigned drive power, speed and medium temperature values are stored, and that the control device for indirectly determining the medium temperature from the measured drive power, the speed and the compression r-specific parameters is connected to the data memory ( 14 ). 20. The device according to at least two of claims 17 to 19, in particular according to claims 17 and 18 and 19. 21. Device according to one of claims 17 to 20, characterized characterized in that the drive motor is an electric motor and that the drive power sensor is a current sensor Has measurement of the motor current. 22. The device according to one of claims 17 to 21, characterized characterized in that the power control a frequency um has judge for driving the electric motor.   23. Device according to one of claims 16 to 22, characterized in that for different temperatures of the inlet-side conveying medium, different compression-specific parameters are stored in the data memory ( 14 ). 24. The device according to one of claims 16 to 23, characterized characterized in that the control device for selecting the respective temperature of the medium on the inlet side assigned compressor-specific parameters with a Fluid temperature sensor is connected. 25. Device according to one of claims 16 to 24, characterized in that the combinations of values are stored as a family of characteristics in the data memory ( 14 ). 26. Device according to one of claims 16 to 25, characterized in that at least one characteristic curve ( 3 , 4 , 5 ) of the family of characteristic curves is a straight line. 27. The device according to one of claims 16 to 26, characterized in that at least one characteristic ( 3 , 4 , 5 ) of the family of characteristics is a polynomial, in particular a second-line polynomial. 28. Device according to one of claims 16 to 27, characterized in that at least one characteristic curve ( 3 , 4 , 5 ) of the family of characteristic curves is defined by support points stored in the data memory and that at least one of these support points represents the usable characteristic curve range of the characteristic curve ( 3 , 4 , 5 ) limited. 29. The device according to any one of claims 16 to 28, characterized in that the data memory ( 14 ) has at least two data storage areas in which compressor-specific parameters for different types of compressors are stored, and that the data storage areas for adapting the data memory ( 14 ) to the particular one used Compressor type are switchable. 30. Device according to one of claims 16 to 29, characterized in that the control device has an interface for storing compressor-specific parameters in the data memory ( 14 ) and / or for selecting a data storage area associated with a compressor type with compressor-specific parameters.