Method for quantitatively determining a current operating point dependent variable of a fan, in particular the current conveying volume flow rate, and a fan for applying the method

Abstract

The present invention relates to a method for quantitatively determining a current delivery volume flow rate or other operating point dependent variable of a fan with a motor-driven impeller, where the delivery volume flow rate or other current operating point dependent variable is calculated or determined directly or indirectly by an algorithm using motor-internal and motor-external variables.

Description

[Technical field]

[0001] The present invention relates to a method for quantitatively determining a current operating point dependent variable, in particular the current delivered volume flow rate, of a fan comprising at least one motor-driven impeller. Furthermore, the method relates to a fan for applying the method. [Background technology]

[0002] No further specifications are given regarding the fans. Thus, a fan as used herein may essentially be a fan of any design, and in particular may be a radial fan, a mixed flow fan or an axial flow fan.

[0003] In particular, in order to control the fan, it is necessary to continuously determine the volume flow rate while the fan is in operation. Other operating state dependent variables (eg, current pressure rise) can also be determined based on knowledge of the current delivery volume flow rate or directly. In addition to controlling the fan speed to a specific volumetric flow rate, knowledge of the current delivery volumetric flow rate and other operating state dependent variables can be used in a variety of ways, for example when monitoring fan power or ventilation system status.

[0004] With respect to fans, a known pressure rise may allow monitoring of reserve pressure for fans prone to stall, for example. It can be identified whether the operation of the fan is within an acceptable operating range and it is also possible to identify, for example, whether a so-called drum motor is operating at too low a pressure.

[0005] Examples of other useful operating state dependent variables include the current delivered mass flow rate, the current noise emission of the fan, the current torque of the fan, the current efficiency of the fan, or the current thrust generated by the fan.

[0006] Furthermore, the operating state dependent variable may be a combination of previously identified variables, such as a function of pressure rise and delivery volume flow rate. In this way, the volumetric flow / pressure characteristic curve can be mapped. In practice, it is known to determine the current delivered volume or mass flow rate in a forward curved radial fan by means of the shaft torque. In other cases, the volumetric flow rate is determined by measuring the differential pressure or by using a vane anemometer. In this respect, reference is made, by way of example, to US Pat. No. 5,399,633. However, processes for measuring and determining the volumetric flow rate of air known in practice are imprecise and complicated to implement.

[0007] In particular, when determining the volumetric flow rate using vane anemometers located on the inlet or outlet side near the fan impeller, in addition to the delivered volumetric flow rate, the vane anemometer speed is also affected by the flow pattern, which is operating condition dependent, non-uniform and / or swirling across the flow cross section of the anemometer wheel, resulting in inaccurate determination of the volumetric flow rate. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] International Publication No. 2018 / 036802(A1) Summary of the Invention [Problem to be solved by the invention]

[0009] The invention is based on the object of identifying a method for quantitatively determining the current delivery volume flow rate or other current operating point dependent variable of a running fan with high accuracy and relatively low construction / technical costs. This method is also different from competing methods. A fan for using this method is also identified. [Means for solving the problem]

[0010] The aforementioned object is achieved, with regard to the method, by the features of claim 1 and, with regard to the fan, by the features of claim 11. Thus, motor-internal and motor-external variables are determined, from which the delivered volume flow rate and / or other current operating point dependent variables are calculated or determined directly or indirectly by an algorithm.

[0011] According to the present invention, it has been found that, using motor-internal and motor-external variables, the current conveyed volume flow rate or other current operating point-dependent variables can be quantitatively determined with high accuracy and at relatively low technical cost. It is important to combine at least one motor internal variable with at least one motor external variable, both of which are easy to detect. By using two different variables, it is possible to eliminate the pure dependence of the operating state on the motor's external signals.

[0012] The motor internal variable used may be a current, e.g. a winding current, a motor current or a motor voltage. Electrical power is also available. These motor-internal variables relate to conditions within the motor and / or its motor control system. Additionally, the motor speed can be used as a motor internal variable.

[0013] The motor external variables used may be measurements or signals of sensors placed in the immediate vicinity of the fan or impeller. The sensor may be a volume flow measuring wheel. In that case, the motor-external variable is the speed of the volume flow measuring wheel.

[0014] The volume flow measuring wheel is advantageously rotatably mounted on the inlet or outlet structure. This structure may be an inlet grid or any housing part. In this regard, no additional structural components are required.

[0015] Additionally, the sensor may be a thermal sensor, such as a hot wire anemometer, that is sensitive to flow velocity.

[0016] Also, the sensor is a differential pressure sensor that detects the pressure difference between two specific points in the flow field of the fan.

[0017] The algorithms used for the calculation are executed in the motor control system or in an external evaluation unit. The algorithm typically includes a processor and a memory. The sensor signal can be transmitted to the processor contactlessly, such as via wires or wirelessly.

[0018] The fan or the fan motor has an interface which is used to transmit the determined current conveyed volume flow rate and / or the determined current other operating point dependent variables to a higher-level system. In this respect, a signal of the volume flow set value, mass flow set value or other operating state dependent variable set value is sent to the motor and / or evaluation unit, and this signal is used to control the motor speed so that the current conveyed volume flow rate, conveyed mass flow rate or other operating point dependent variable determined using the sensor signal corresponds as accurately as possible to the volume flow set value, mass flow set value or corresponding set value.

[0019] The fan according to the invention may be used to control the current delivery volume flow rate or other operating point dependent variables in accordance with the above description.

[0020] Thus, various possibilities exist for advantageously configuring and developing the invention. In this respect, reference is made to the claims dependent on claim 1 and then to the following description of an embodiment of the method according to the invention with reference to the drawings, in which: Generally preferred configurations and teaching developments are also described in conjunction with the description of embodiments of the invention with reference to the drawings. [Brief description of the drawings]

[0021] [Figure 1] FIG. 1 is a perspective cross-sectional view of an embodiment of a fan taken along a plane passing through the axis of rotation of the impeller, in which a current delivered volumetric flow rate and a current operating point dependent variable are determined using a vane anemometer. [Diagram 2] 2 is a graph showing characteristic curves of the pressure rise Δp in each case as a function of the conveyed volume flow QV for a fan at a particular conveying medium density for four different constant anemometer speeds and two constant motor speeds. [Diagram 3] 2 is a graph showing the characteristic curves of the pressure rise Δp in each case as a function of the conveyed volume flow QV for four different constant anemometer speeds and five constant motor speeds for a fan at a particular conveying medium density. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] FIG. 1 shows an embodiment of a fan 1 in a perspective cross-section in a plane passing through the axis of rotation of the impeller 3 , in which the current delivered volume flow rate and other operating point dependent variables are accurately determined by a volume flow measuring wheel 2 . The volume flow measuring wheel 2 essentially consists of a hub 7 and blades 6 fixed to the hub 7 . This figure clearly shows the volume flow measuring wheel 2 and the mounting for the volume flow measuring wheel 2 on the inlet structure, in this case the inlet grid 26. The shaft 13 for mounting the volume flow measuring wheel 2 is attached to the central area 30 of the inlet grid 26 via a receiving area 31 .

[0023] The volume flow measuring wheel 2 is mounted on the shaft 13 by means of bearings, in this embodiment two bearings are provided which are not shown. The bearings are mounted on the volume flow measuring wheel 2 in bearing receptacles 20 provided in the hub 7 . In this way, the volume flow measuring wheel 2 is free to rotate relative to the inlet grid 26 independently of the rotor 11 of the motor 4 which drives the impeller 3 of the fan 1 . By measuring the speed of the volume flow measuring wheel 2 in addition to other sensor information, the current conveyed volume flow QV of the conveyed medium and other operating point-dependent variables can be deduced with considerable accuracy.

[0024] The impeller 3 of the fan 1 is attached to the rotor 11 of the motor 4 via a fastener 15 , which is a sheet metal member that is enclosed within the impeller 3 and pressed against the rotor 11 . The measurement and evaluation of the speed nAne of the volume flow measuring wheel 2 is an essential basis for determining the conveyed volume flow QV of the current conveying medium or any other current operating point-dependent variable. If the current conveying volume flow QV of the conveying medium or other current operating point-dependent variables are to be determined with high precision, further sensor information is required in addition to the speed nAne, since the speed nAne depends not only on the conveying volume flow QV but also on the (internal) operating state of the fan. The operating state of the fan may change. For example, the amount of static pressure increase that the fan accumulates in the conveying direction may change even if the conveying volumetric flow rate QV is constant. In the present invention, motor internal variables (possibly electrical variables) of the motor 4 or the motor control system are used as such additional sensor information.

[0025] The volume flow measuring wheel 2 can generally be mounted on the inlet or outlet side of the fan, for example on the inlet grid 26 or in the housing. Instead of the motor-external variable vane anemometer speed nAne, another motor-external sensor signal can also be used to determine the conveyed volume flow rate QV of the current conveying medium or another operating point-dependent variable. A first example of another motor-external variable is the signal of another hot wire anemometer or equivalent thermal sensor that is sensitive to flow velocity. A second example of another motor-external variable is the signal of a differential pressure sensor that measures the pressure difference between two suitable points within the fan flow area (e.g., the nozzle pressure differential, which is the difference between the static pressure at the narrowest cross-sectional area of ​​the fan inlet nozzle and the static pressure at a point further inlet of the inlet nozzle).

[0026] The current value of the current conveyed volume flow QV or other operating point-dependent variable is determined by a suitable algorithm from the sensor signals of the motor-external variables and second sensor signals of the motor-internal variables (e.g. motor current IMot, winding voltage UMot or power, etc.). This algorithm is advantageously executed directly in the motor control system, but may also be executed in an external evaluation unit. Of course, these sensor signals must be transmitted to their corresponding locations.

[0027] JPEG2024532458000002.jpg61170

[0028] JPEG2024532458000003.jpg17170 JPEG2024532458000004.jpg11170

[0029] JPEG2024532458000005.jpg57170

[0030] JPEG2024532458000006.jpg23170

[0031] It is advantageous if the motor 4 or an external evaluation unit has an interface for transmitting the current conveyed volume flow QV or the current operating point-dependent variable X to a higher-level system. Furthermore, it is advantageous if a signal of the set value of the conveying volume flow rate or the set value of the operating point-dependent variable X is sent to the motor 4 or to an external evaluation unit, so that the motor speed nMot is automatically controlled in such a way that the conveying volume flow rate QV or the current operating point-dependent variable X, which is determined using the sensor signal, corresponds as closely as possible to the volume flow rate set value or the set value of X.

[0032] For completeness of understanding, it should be noted that not all components of fan 1 are shown in FIG. Specifically, for the sake of clarity, for example, the motor holder connecting the stator 12 of the motor 4 to the nozzle plate 29 is not shown. The fan 1 may include a number of other components not shown.

[0033] FIG. 2 is a graph showing, for an arbitrary fan, the horizontal axis representing the delivered volume flow rate QV and the vertical axis representing the static pressure rise psF, two characteristic curves at a constant motor speed nMot and four characteristic curves for a constant vane anemometer speed nAne of a vane anemometer mounted close to the fan. It can be seen that the delivered volume flow rate QV is not an exactly constant value at a constant vane anemometer speed nAne, which means that without additional information QV can only be determined imprecisely. In particular, in many specific applications, such as controlled domestic ventilation systems, the imprecision is high. This is due in particular to the fact that the operating conditions of the fan impeller (at constant conveying volume flow rate QV) have a very large influence on the anemometer speed nAne, since for compactness reasons the anemometer wheel is mounted relatively close to the impeller. In this graph it is clear that the motor speed nMot provides some complementary information for a more accurate determination of the delivered volume flow QV. For example, the intersection point of the characteristic curve of a constant motor speed nMot and a constant vane anemometer speed nAne can be determined and a more accurate value of the current conveyed volume flow QV can be read off at the intersection point of the curve. The key is to combine both sensor signals to obtain the required information. When processing only two sensor signals, a particular type of algorithm for determining the delivered volume flow QV can be implemented in various ways.

[0034] However, determining the motor speed nMot is rather complicated, for example because of the need for Hall sensors. It has been found that instead of the motor speed nMot it is also possible to use the (possibly electrical) motor internal variable INT, which is very easy to detect by a sensor.

[0035] FIG. 3 shows a graph of the fan of FIG. 2 with the horizontal axis representing the delivered volume flow QV and the vertical axis representing the static pressure rise psF, with five characteristic curves at constant motor winding current IMot and four characteristic curves for constant vane anemometer speed nAne of a vane anemometer mounted close to the fan. It can be seen that the delivered volume flow rate QV is not exactly constant at a constant vane anemometer speed nAne, which means that without additional information QV can only be determined imprecisely. This inaccuracy is unacceptable for many applications. This is due to the fact that the operating conditions of the fan impeller (at constant conveying volume flow rate QV) have a very large influence on the vane anemometer speed nAne, in particular because for compactness reasons the anemometer wheel is mounted relatively close to the impeller.

[0036] It is clear from this graph that some of the complementary information for a more accurate determination of the conveyed volume flow QV is present in the motor winding current IMot, which can be detected via a sensor with relatively little effort. For example, the intersection point of the characteristic curve of constant motor winding current IMot and constant vane anemometer speed nAne can be determined and a more accurate value of the current conveyed volume flow QV can be read off at the intersection point of the curve. The key is that information can be gained by combining both sensor signals. When processing only two sensor signals, specifically the motor external sensor signal (in this case the vane anemometer speed nAne) and the motor internal sensor signal (in this case IMot), a certain type of algorithm for determining the conveyed volume flow rate QV can be implemented in various ways.

[0037] It should be noted that in order to quantitatively establish the calculation algorithm, calibration using measurement data on a test bench is required at least for each embodiment of the fan. For example, for the fan involved, a characteristic curve for constant motor winding current IMot versus constant vane anemometer speed nAne can be determined and stored in the motor control system or in an external evaluation unit. Other calculation algorithms are possible and, as a result, other calibrations are required. It is important that the motor external variable EXT (in this case the vane anemometer speed nAne) and the motor internal variable INT (in this case the motor winding current IMot) are treated as sensor / input variables in the algorithm to determine the current value of the current delivered volume flow QV or other operating point dependent variables.

[0038] It is also conceivable to find calibration parameters for the particular application or installation conditions in order to achieve greater accuracy in determining the value of the current delivery volume flow QV or other current operating point dependent variable in the relevant application.

[0039] In the present invention, the motor-external variable used may be the signal of a hot wire anemometer or similar thermal sensor sensitive to local air speed, or it may be the signal of a differential pressure sensor measuring the difference in static pressure between two specific points within the area of ​​the fan. In both cases, the sensor signal is usually determined to depend on the current delivered volume flow QV as well as on the operating state of the fan impeller 3, which may be expressed, for example, in terms of a value of static pressure rise psF. This dependency on the operating state can be eliminated by adding sensor signals representing internal, possibly electrical, variables within the motor, which makes it possible to achieve significantly greater accuracy in determining the current delivered volume flow QV and, consequently, the current values ​​of other operating point-dependent variables.

[0040] If a pressure difference or a hot wire anemometer signal is used as motor external signal, the current conveying medium density is also required as a further input variable for determining the conveying volume flow QV. Advantageously, this transport medium density can be assumed to be constant and can also be determined in real time with the aid of further sensor signals (eg relating to the temperature and moisture content of the transport medium).

[0041] On the other hand, the mass flow rate of the conveying medium can be determined using the volume flow rate QV of the conveying medium, which is determined using the density of the conveying medium. If a pressure difference or a hot wire anemometer signal is used as motor external signal, it is also possible to directly determine the conveying medium mass flow rate without knowing the conveying medium density.

[0042] As regards further advantageous configurations of the method according to the invention, in order to avoid repetition, reference is made to the general part of the specification and to the appended claims.

[0043] Finally, the above-described embodiments of the method according to the invention are purely useful for illustrating the claimed teachings, but do not limit the claimed teachings to the embodiments. [Explanation of symbols]

[0044] 1. Fan 2. Volumetric flow measuring wheel (vane anemometer) 3. Fan impeller 4 Motor 5. Inlet nozzle 6 Blades of the volumetric flow measuring wheel 7 - Hub of volume flow measuring wheel 8 Impeller top ring 9 Impeller blades 10 Impeller hub ring 11 Motor rotor 12 Motor stator 13 .... Shaft for mounting the volume flow measuring wheel 15 - Device for fixing impeller to motor 20 .... Receptacle for bearing in volume flow measuring wheel 26...Inflow grid 29 Nozzle plate 30 Central region of the inflow grid 31... Shaft receiving area of ​​inlet grid

Claims

1. 1. A method for quantitatively determining a current delivery volume flow rate or other operating point dependent variable of a fan having a motor-driven impeller, comprising:

1. A method for quantitatively determining a current delivered volume flow rate or other operating point dependent variable of a fan, wherein motor-internal and motor-external variables are determined, and from the motor-internal and motor-external variables, the current delivered volume flow rate or other operating point dependent variable is calculated or determined directly or indirectly by an algorithm.

2. 2. The method according to claim 1, characterized in that the motor-internal variable is a current, such as a winding current or a motor current, a motor voltage or a power, in the motor or in the motor control system of the motor.

3. 2. The method of claim 1, wherein the motor internal variable is motor speed.

4. 2. The method of claim 1, wherein the motor external variable is a measurement or signal of a sensor located in the immediate vicinity of the fan or impeller.

5. the sensor is an anemometer including a volume flow measuring wheel; 5. The method of claim 4, wherein the motor-external variable is the speed of the anemometer or the speed of the volume flow measuring wheel.

6. 6. The method according to claim 5, characterized in that the volume flow measuring wheel is rotatably mounted on an inlet or outlet structure, in particular on an inlet grid or housing part.

7. 5. The method of claim 4, wherein the sensor is a thermal sensor sensitive to flow velocity, such as a hot wire anemometer.

8. 5. The method of claim 4, wherein said sensor is a differential pressure sensor that detects the pressure difference between two specific points in the flow field of said fan.

9. the algorithm is executed in a motor control system or an external evaluation unit having a processor and a memory, 10. The method of claim 1, wherein the sensor signal is transmitted to the processor by wire or in a contactless manner.

10. 2. The method according to claim 1, wherein the fan motor has an interface used to transmit the determined current conveying volume flow rate or the determined current operating point dependent variable to a higher-level system.

11. a signal for a volume flow setpoint or an operating point dependent variable setpoint is transmitted to the motor and / or to the external evaluation unit, 11. The method of claim 10, wherein the signal is used to control the motor speed so that the current delivery volume flow rate or the other operating point dependent variable determined using a sensor signal matches the volume flow rate setpoint or the operating point dependent variable setpoint as accurately as possible.

12. A fan for controlling the current conveying volume flow rate or other operating point dependent variables for applying the method described in claim 1.

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