JPS61226594A - Method of detecting flow rate of speed variable pump - Google Patents

Abstract

PURPOSE:To eliminate the need for using a function generator and easily detect the flow rate of discharging by approximating relation among a head, the number of revolution, and a flow rate by means of a quadratic function and operating the flow rate from the head and the number of revolution through the combination of only multiplication, division, subtraction and square-root extraction. CONSTITUTION:Relation among the head H, the number of revolution N, and the flow rate Q of a pump is approximated by means of a quadratic function, and the flow rate Q corresponding to the head H and the number of revolution N is calculated by a particular formula. That is, a pump head H is obtained by a subtracter 5, and N/100 is obtained by a multiplier 11. Then, the results obtained by multipliers 14, 15, 16, 17 and a subtracter 19 are inputted into a subtracter 21, and further, made pass through a square-root extractor 24 and, finally, a subtracter 22 and a divider 23, completing the operation of the particular formula for calculating the flow rate Q corresponding to the head H and the number of revolution N. Thereby, a special function generator can be eliminated, enabling an indirect detection of the flow rate of a speed variable pump, using a simple electronic computer with a small memory capacity.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a variable speed pump flow rate detection method that indirectly detects the discharge flow rate of a variable speed pump from the rotational speed and head of the pump.

[Technical Background of the Invention and its Problems] Generally speaking, to measure the discharge flow rate of a pump, it is necessary to directly measure the
A filter or venturi is used, but in the case of large-capacity pumps, it is often impossible to directly measure the flow rate due to installation location, pressure loss, etc.

In this case, it is necessary to measure the indirect C flow rate using calculation.

An example of this is the device disclosed in Japanese Patent Application Laid-Open No. 58-1838931, the construction of which is shown in FIG. 4C.

In FIG. 4, 1 is a variable speed pump, 2 is a water level gauge of the suction valve 20, 3 is a water level gauge of the discharge valve 30, 7 is a rotation speed meter of the pump 1, and 4 is a flow rate calculation device.

That is, the detection signal H1, f(O) of the water level gauge 2.3 is input manually to the subtractor 5, and the pump head H is calculated from H=Ho Ht l2.

On the other hand, the detection signal N of the rotation speed meter is manually inputted to the divider 8, and 10
0/Nl-converted and further (12th power characteristic function generator 9
It is converted to (10(+/N) 2 ) via .

The above calculation output (100/N)'' and H are multiplied by a multiplier 10, and the operating position C when the rotation speed N and the actual head H is the corresponding head H of the similar point when N=100%. Desired.

When this head Ha is input to a function generator 6C with QH characteristics where N = 100%, the flow rate Qn corresponding to the unit rotation speed is calculated.
is obtained, and the actual number of i1Q people is calculated by adding the signal N/100 input through the multiplier 11 and the multiplier 12.

The flow rate calculation device shown in FIG. 4 requires a function generator 6 that stores the Q-H characteristics of the pump. The software for both is complex and the storage capacity required is also large.

In other words, the processing content of the software is as shown in FIG.
)-2, determine which point the input value X on the X axis is at, and sandwich this between the two points (XA, Y person).

From (xa, YB), x (corresponding y
Calculate.

The outline of this processing content is added to the flowchart in Figure 6 (in Figure 6, N is the total number of coordinate combinations), but it requires advanced functions such as conditional branching, and the programmable controller 4; Small scale using simple language 1! However, it is difficult to process on a machine, and there is also the problem that the storage capacity becomes large.

[Objective of the Invention] The present invention provides a simple method for calculating the discharge flow rate of a pump indirectly (-) from the rotational speed and head of the pump by a combination of simple basic calculations without using a function generator. The purpose of this invention is to provide a method for detecting the amount of a variable speed pump.

[Summary of the Invention] The present invention provides a flow rate detection method for a variable speed pump, which detects the rotation speed and head of a variable speed pump, and indirectly detects the pump discharge flow rate by performing predetermined calculations from the detected rotation speed and head. In this method, the relationship between head, rotation speed, and flow rate is approximated by a quadratic function, and the flow rate is calculated by a combination of only multiplication, division, subtraction, and square root calculation from the head and rotation speed, and thereby a special function generator is used. This is an indirect flow rate detection method for a variable speed pump that can be implemented using a simple meter S device with a small storage capacity, even if unnecessary.

Embodiment of the Invention An embodiment of the present invention is shown in FIG. It is the same as Figure 4.

First, the performance of the FE3 in the present invention will be explained with reference to the characteristic diagrams of the pump shown in FIGS. 2 and 3.

The relationship between the flow rate Q and the head H using the pump rotational speed N as a parameter is as shown in FIG.

Here, Nh: #Initial pump rotation speed NB: Pump rotation speed after shifting Qm: Flow rate when N people Qn: Flow rate when Nn H people 2 Head when N people HB: Height when NB Therefore, the QH characteristic of the pump shown in FIG. 2 can be approximated by the following quadratic function.

Here, H: Head Q: Flow rate N: Number of revolutions a, b, c: Coefficients From equation (4), the flow tQ corresponding to the head H and the number of revolutions N can be calculated using the following equation.

Therefore, if the Q-H characteristic when the rotation speed N = 100% is known, the Q-H characteristic can be approximated using equation (4), and the coefficient a,
b and c can be found.

In determining the coefficients a, b, and c, as shown in FIG.

Since the lift 8H is calculated as H8-Hl, the coefficient a,
Once b and c are determined, the pump discharge flow tQ can be calculated by substituting the rotational speed N into the head H in equation (5).

Therefore, if the calculation of equation (5) is stored in an electronic counter (-), it is possible to use subtracters, multipliers, etc. without using a function generator.
The pump discharge flow rate can be calculated using only basic calculation functions such as a divider and a square root calculator.

It is the same as in the conventional case of Fig. 4 that the pump head H is obtained from the 2-cchi Fig. 1 (-, #, It is.

The next C unit multiplier 16, subtracter 19, and multiplier 17 (
5) 14.15 (c bN )2 is calculated,
Through both results subtractor 22 and divider 23 (5)
After completing the calculation of the equation, the discharge flow rate Q is calculated.

Coefficients a, b, and c are set and stored in advance.

[Effects of the Invention] As explained above, according to the present invention C2, a variable speed pump can be generated by combining basic operations such as multiplication, division, subtraction, and square root without using a function generator that requires complicated processing. The discharge flow rate of the pump can be calculated indirectly from the pump's rotational speed and head. A detection method is obtained.

[Brief explanation of drawings]

Fig. 1 is a system diagram showing an embodiment of the present invention, Figs. 2 and 3 are pump characteristic diagrams showing the calculation basis of the invention, and Fig. 4 is a system diagram showing an example of a conventional flow calculation device. , FIG. 5 is a characteristic diagram of the function generator used in FIG. 4, and FIG. 6 is a flowchart showing the operation of the function generator. 1... Variable speed pump 2... Suction valve water level gauge 3...
・Discharge valve water level gauge 4...Flow control 3I device 7...Revolution meter 20...Suction valve 30...Discharge valve agent Patent attorney Yoshiaki Inomata (and 1 other person) 1st
Figure QA Qβ 0- 5 艷i Figure 2 D → Condolences Figure 5 Figure 6

Claims (1)

[Claims] In a variable speed pump flow rate detection method that detects the rotation speed and head of a variable speed pump, and indirectly detects the pump discharge flow rate by performing a predetermined calculation from the detected rotation speed and head, the head, rotation speed, and flow rate are A flow rate detection method for a variable speed pump, characterized in that the relationship is approximated by a quadratic function, and the flow rate is calculated by a combination of only multiplication, division, subtraction, and square root calculation from the head and rotation speed.