JPS6293498A - Operation of speed controlled pump - Google Patents

Abstract

PURPOSE:To obtain the high accurate control of a pump, by carrying out the predictive terminal pressure constant control of the pump based on a real pump head and a pipe line constant which is calculated by substituting a discharge pressure and a discharge quantity of flow per terminal quantity of flow for the function of a pipe line load resistance curve. CONSTITUTION:A controller 20 which controls the revolution number of a variable speed motor 12, on the early time of the operation of a pump 11, measures a discharge quantity of flow Q and a discharge pressure H by a flowmeter 14 and a pressure sensor 13 at every terminal quantity of flow which is changed by a cock 16 under a constant pressure at the terminal of a pipe line 15. At the discharge quantity of flow Q and the discharge pressure H are respectively substituted for the function of a pipe line load resistance curve F so as to calculate a pipe line constant K and a real pump head ho. A target pressure Hf is calculated by the K and the ho, then the present discharge pressure H of the pump 11 is measured by the pressure sensor 13, the Hf and the H are compared with, and the revolution number of the variable speed motor 12 is increased or decreased until the pressures H and Hf become an equal pressure. Thus, the pump 11 is speed-controlled along the curve F corresponding to the change of the quantity of water for use, so that the pressure of the water for use can be made constant.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a method of operating a speed control pump, and is particularly suitable for performing predictive terminal pressure constant control that controls the pressure of the terminal flow rate of a piping system at a constant level. Regarding driving laws.

[Background of the invention]

When controlling the pump speed in a general water supply system,
Various control methods are employed, such as pressure control, flow control, water level control, etc. The pressure control methods include constant discharge pressure control that keeps the pump discharge pressure constant, and predictive end pressure control that keeps the end pressure of the piping system constant.

In both of these control systems, it is ideal to use predictive pressure constant control that can keep the pressure at the end of the pipe constant regardless of the amount of water used.

Figure 7 shows a conventional example of a water supply system that performs predictive terminal pressure constant control, and Figure 8 shows the pump's Q-I-I performance, with the horizontal axis representing the discharge flow rate Q and the vertical axis representing the discharge pressure H. It shows a curve.

In the figure, 1 is a pump having a variable speed electric motor 2, 3 is a pressure sensor, 7 is a flow meter, 4 is a calculator, and 5 is a tank. In this control method, a pressure sensor 3 is installed at the end of the pipe line 6, and the rotation speed of the pump 1 is controlled so that the end flow pressure detected by the pressure sensor 3 is constant. , when the pressure sensor 3 is installed at the end of the pipe line 6,
Since the piping system is long and difficult in terms of wiring 8 and maintenance, generally a pressure sensor 3 is placed beside the discharge of the pump 1 as shown by the chain line, and the pressure at this part is determined from the flow meter 9. In order to satisfy the load resistance curve F of the pipeline shown by the formula (1) based on the amount of water used Q, that is, the pump rotation speed No. is adjusted so as to be operated at the 6 points a, b + Qo d shown in Fig. 8. N.

Control to NZt N3+N4.

Ht = K Q 10h O・・・・・・・・・(1
) Here, Hf: pump discharge pressure: pipe line constant Q: amount of water used n: constant (generally 2) h: actual head For example, if the amount of water used is Qo, the rotation speed of the variable speed motor 2 is No. The Q-H performance curve of pump 1 is A and a
Assume that you are driving at a point. From this state, when the amount of water used becomes Qo, the discharge pressure of pump 1 becomes Q - H
The pressure I-I increased along the performance curve A, and a'
It becomes a point. The pressure sensor 3 detects this increased pressure, and the flow rate detector 9 detects the discharge flow rate Q1. Then, by substituting the detected flow rate Q1 into equation (1), the target pressure Itr (Hr=KQ 10ho) is determined by the calculator 4, and the pressure H detected by the pressure sensor 3 and the target pressure determined by the calculator 4 are calculated. So that the deviation IHrH+l from Hf becomes O,
When the rotational speed of the variable speed electric motor 2 is controlled, the rotational speed becomes N, and the Q-H performance curve of the pump becomes B,
The operating point moves from point a' to point b. Thereafter, the speeds of the variable speed motor 2 and the pump 1 are controlled along the load resistance curve F of the pipe line in accordance with changes in the amount of water used.

By the way, in the conventional example shown above, the pipe load resistance curve F
In the functional formula, the pipe line constant K and the actual head hO are determined by the piping system, so they are calculated from one drawing. Therefore, when the equipment is installed on site, the pipe line constant K and the actual head.

The reality is that it is difficult to control accurately because the actual installation may differ depending on time and calculations, and may also change due to changes in the piping system over time.

[Purpose of the invention]

SUMMARY OF THE INVENTION In view of the problems of the prior art described above, it is an object of the present invention to provide a speed control pump operating method that accurately determines the pipe line constant and actual pump head from the actual condition of the pipe line and accurately performs constant predicted terminal pressure control. There is a particular thing.

[Summary of the invention]

The first aspect of the present invention is to change the end flow rate in advance under a constant target pressure at the end of the pipe at the initial stage of operation of the pump, and to adjust the pump discharge pressure and discharge flow rate for each changed end flow rate. , calculate the pipe constant and actual head by substituting the discharge pressure and discharge flow rate for each terminal flow rate into the function of the pipe load resistance curve, and calculate the pipe constant and the actual head based on the pipe constant and the actual head. It is characterized in that it performs predictive terminal pressure constant control, and as a result, the pipe constant and the actual head can be accurately determined from the actual condition of the pipe system when starting pump operation.
It is possible to accurately control the terminal pressure to be constant.

Further, the second aspect of the present invention is to change the end flow rate in advance under a constant target pressure at the end of the pipe at the initial stage of operation of the pump, and measure the rotation speed of the pump for each changed end flow rate. , calculate the Q-H performance curve of the pump at the rotation speed based on a predetermined reference Q-H performance curve, and then measure the discharge pressure at the rotation speed to correspond to the discharge pressure. Calculate the discharge flow rate from the Q-H performance curve of the pump, substitute the discharge pressure and discharge flow rate for each end flow rate into the function of the pipe load resistance curve, calculate the pipe resistance and actual head, and calculate the pipe resistance and actual head. The feature is that the predicted end pressure is controlled to be constant based on the pipe line constant and the actual head, and as a result, the effect of the first invention can be obtained, and the discharge flow rate can be adjusted without using a flow meter. Since the conduit constant resistance and the actual head can be calculated accurately by determining the constant predicted terminal pressure, it is possible to accurately control the predicted end pressure to be constant.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to FIGS. 1 to 6. FIG. 1 is a schematic diagram showing an embodiment of a water supply device for carrying out the method of the present invention, FIG. 2 is a block diagram of a control device,
FIG. 3 is a flowchart showing a first embodiment of the method of the present invention.

As shown in FIG. 1, a water supply system for implementing the method of the present invention includes a pump 11 having a variable speed electric motor 12, and a pump 1.
a pressure sensor 13 that measures the discharge pressure of pump 11;
a flow meter 14 that measures the discharge flow rate, a faucet 16 provided at the end of the pipe 15, a pressure gauge 17 that measures the flow pressure at the end of the pipe 15, and controls the rotation speed of the variable speed electric motor 12. A control device 20 is provided.

The control device 20 includes a microcomputer (hereinafter abbreviated as CPU) 21 that performs calculations and processing according to a predetermined program, a rotational speed N detected by a tachometer, and a discharge rate detected by a flowmeter 14. Amount Q and water discharge pressure Hr'a detected by the pressure sensor 13: CP
An input unit 22 that inputs to U21 and a first storage unit (ROM
) 23 and a second storage section (RAM) 24, and a control section 26 which receives input from the C:PU 21 via an output section 25 and controls the rotation speed of the variable speed electric motor 12.

When the pump 11 is in operation, this control device 20 operates as shown in FIG.
As shown in the section, when the pipe line constant and the actual head hO are stored in the storage means, the CPU takes in the discharge flow rate Q measured by the flowmeter 14, and calculates the above-mentioned equation (1). Calculate the terminal target pressure Hr, take in the current discharge pressure H measured by the pressure sensor, compare the magnitude of this discharge pressure H with the target pressure H, and calculate the comparison result, discharge Pressure H
When a difference occurs between the target pressure Hf and the target pressure Hf, the controller 1
~The variable speed electric motor 1 until the same pressure is achieved by the roll portion 26.
The flow rate pressure at the end of the pipe line 15 can be kept constant by slowing down or increasing the rotational speed of the pump 2 to make the discharge pressure H and the target pressure Hf the same pressure.

In addition, this control device 20 changes the end flow rate using the faucet 16 under a constant pressure at the end of the pipe line 15 at the initial stage of operation of the pump, and uses a flow meter 14 for each changed end flow rate.
The discharge flow rate Q and the discharge pressure H are measured by the pressure sensor 13 and the discharge flow rate Q and the discharge pressure H are calculated as (1
) to calculate the pipe line constant and the actual head hO.

Next, an embodiment of the method of the present invention will be described with reference to FIG. 3 in connection with the control operation of the water supply device of the embodiment.

First, at the initial stage of operation of the pump 11, test run the pump 11, and open the water faucet 16 to allow a suitable terminal flow rate (Sl)
, the rotational speed N1 of the variable speed motor 12 is adjusted so that the pressure of the terminal flow rate becomes the target pressure PO using the pressure gauge 17 (S2).

At this time, the discharge flow rate Q is measured by the flow meter 14 and the pressure sensor 13.
+ and discharge pressure H, are measured and stored in the second storage unit 24 (S3), and it is determined whether this measurement has been performed a predetermined number of times (S4). As a result of the determination, if the process is not performed a predetermined number of times, the opening degree of the faucet 16 is changed to change the flow rate Q (S5),
The following steps 82 to S5 are repeated until a predetermined number of times is reached.

Therefore, under a constant target pressure po at the end of the pipe line 15,
The terminal flow rate is varied, and the discharge flow rate Qn and discharge pressure Hn are measured for each of the various terminal flow rates Q.

On the other hand, when the measurement is carried out a predetermined number of times, the various discharge flow rates Qn and discharge pressures Hn measured in S3 are sent to the CPU 21.
By substituting into equation (1), the pipe resistance and the actual head ho are calculated (S6), and the pipe resistance and the actual head hO are stored in the second storage unit 24 (S7).

After the process in S7, the pump 1 is
] to perform constant terminal pressure control.

That is, the control device 20 measures and takes in the discharge flow rate Q of the pump 11 using the flowmeter 14 (S8), and adds the actual head hO to the discharge flow rate Q and the pipe resistance calculated in 86 (S8).
1) Find the target pressure Hf by substituting it into the equation (S9), then measure and take in the current discharge pressure H of the pump 11 with the pressure sensor 13 (SIO), and calculate the discharge pressure H and the target pressure H.
Compare with f (Sll).

As a result of the comparison, if the discharge pressure H is larger than the target pressure I-If, the rotation speed of the variable speed electric motor 12 is reduced until both pressures become the same (514), while the discharge pressure H is lower than the target pressure H.
If it is smaller than f, the rotational speed of the variable speed motor 12 is increased until both pressures become the same (Sl, 5).

Then, when the discharge pressure H and the target pressure Hr become the same pressure, after a certain period of time has elapsed (31, 3), the processes from S8 onwards are repeated. As a result, the variable speed electric motor 12 and the pump 1
1 is speed-controlled along the line load resistance curve F shown in FIG. 8 in response to changes in the amount of water used, so the pressure of the water used can be kept constant.

As described above, in this embodiment, an actually installed water supply device is used, and when the pump 11 is initially operating, the water is supplied to the conduit 15 to adjust the discharge pressure Hn and the discharge flow rate Qn of the pump 11.
By measuring , the pipe resistance and the actual head hO are calculated, so unlike the conventional values obtained from drawings, the pipe resistance and the actual head hO can be calculated accurately from the actual condition of the pipe. Therefore, predictive terminal pressure constant control can be performed accurately. Moreover, even if the actual state of the pipe line 15 changes due to aging, etc., the pipe resistance will change accordingly.
can be determined accurately, and constant predicted terminal pressure control can always be performed accurately regardless of changes over time.

4 and 5 show a second embodiment of the method of the invention.

In this case, Q-) at each rotation speed of the pump 11
Focusing on the fact that the T performance curves are in a relative relationship, when the rotational speed Nn of the pump 11 is measured for each end flow rate, the Q-H performance curve of the pump at that rotational speed Nn is calculated from the predetermined standard Q- The calculated Q-H performance curve is used to calculate the pipe resistance and the actual head h.
o.

For example, as shown in FIG.
Given a standard Q-H performance curve
, H'2. Q'2, H'3. Q'3...H' n
, Q' n and the point HIy on the Q-H performance curve Y
There is a relative relationship between each of the two points Ql, H2, Q2, H3, Qa, and HntQn as shown in the following equation (2).

Based on the relationship of this equation (2), the standard Q-H performance curve
Each point H'+ y Q'+ , H'zt Q'z・-
Each point Hl, Q at rotation speed N from H'nt Q'n
+, Hzt Qz...Hn, Qn can be converted to obtain the Q-H performance curve Y at the rotational speed N.

Then, the Q-H performance curve Y at this determined rotational speed N
The measured discharge pressure Hx is plotted on the top to calculate the discharge flow rate Qx. Therefore, flow meter 1
4 is not used to determine the discharge flow rate Qx.

Next, to specifically describe the second embodiment of the method of the present invention,
As shown in FIG. 4, at the initial stage of operation of the pump 11, the reference Q of the pump 11 is stored in advance in the first storage unit 23 of the control device 20.
-H Performance curve
The rotational speed Nn of the variable speed electric motor 12 is adjusted so that the rotational speed Nn becomes 0 (S2).

At this time, the rotation speed N of the variable speed electric motor 12 is measured (S1
6), and the control device 20 uses the pre-stored standard Q-H.
Based on the performance curve X, points H1, Ql, H2? from equation (2)?
Q2...Hn and Qn are determined, and the Q-H performance curve Y at the rotation speed N is calculated.

Further, after calculating the Q-H performance curve Y, the control device 20 measures the discharge pressure Hx of the pump 11 using the pressure sensor 13, and plots this discharge pressure Hxl on the Q-H performance curve Y. Accordingly, the discharge flow rate Qx of the pump 11 is calculated (S17).

Then, after changing the end flow rate under a constant target pressure po at the end of the pipe, and measuring the discharge pressure Hxn and calculating the discharge flow jii:Qxn for each changed end flow rate, a predetermined number of times, Substitute the discharge pressure T-1xn and the discharge flow rate Qxn into equation (1) to calculate the pipe resistance and the actual head hO (S6), and after storing these values (S7), Execute predictive terminal pressure constant control with the processing content shown in .

In this way, in this example, the standard Q-H performance curve
Using this, calculate the Q-H performance curve Y of the rotation speed measured based on the Q-I-I performance curve X of this standard, and calculate the Q
- Plot the discharge pressure Hxn measured with the H performance curve Y, calculate the meteor Qxn, and calculate the discharge flow rate Qx
Since the pipe resistance and the actual head ho are determined by n and the discharge pressure Hxn, the pipe resistance and the actual head hO can be determined accurately. You can get the effect - to 1 -.

In addition, in the illustrated embodiment, an example was shown in which the discharge flow rate Qx was obtained by using the standard Q-H performance curve X, but this Q-H performance curve , Q= a H'+ b H+ c
...13) a, b, c: constants By using this equation (3), the discharge flow rate Qx
can be found.

That is, as shown in FIG. 6, Q expressed by equation (3)
The following equations are established between Q' and H' on the -H performance curve and points Hx and Qx on the pipe resistance curve F, respectively.

Q'= a H" + b H'+ c ・
...(4)N'Q'= Qx Nx - (5)N
'H'=Hx(Nx)' ・=(6
)(4), (5), and (6), the flow rate Qx can be found from the known a, b, c, N' and the measured values Hx, Nx, so the procedure is similar to the second embodiment. It is also possible to calculate the pipe resistance and the actual head hO.

〔Effect of the invention〕

As described above, according to the present invention, at the initial stage of operation of the pump, the end flow rate is changed under a constant target pressure at the end of the pipe, and the pump discharge pressure and discharge for each changed end flow rate are The pipe resistance and actual head are calculated based on the meteors, and the predicted end pressure is controlled to be constant based on the pipe resistance and the actual head. It is possible to accurately determine the predicted end pressure constant control from the above, and to perform the predicted terminal pressure constant control with high precision, and it is also possible to perform the predicted end pressure constant control with high precision, regardless of the aging of the pipe staff.

[Brief explanation of drawings]

1ti- Fig. 1 is a schematic diagram showing an embodiment of a water supply device for implementing the method of the present invention, Fig. 2 is a block diagram showing a control device for the water supply device, and Fig. 3 is a schematic diagram showing an embodiment of the water supply device for carrying out the method of the present invention. FIG. 4 is a flowchart showing the second embodiment of the method of the present invention, and FIG. 5 shows the relationship between the standard Q-H performance curve and the Q-H performance curve at the measured rotation speed. Figure 6 is an explanatory diagram when the standard Q-H performance curve is replaced with a functional equation, Figure 7 is a piping diagram showing an example of a conventional water supply device, and Figure 8 is the Q-H of a pump. It is an explanatory diagram showing a performance curve. 11... Pump, 12... Variable speed electric motor, 13...
Pressure sensor, 14...Flowmeter, 15...Pipeline, 16
...Water faucet, 17..Pressure gauge, F.. Pipe load resistance curve, H..Discharge pressure, Q..Discharge flow rate. Representative Patent Attorney Tadashi Akimoto Figure 1 Figure 3 Figure 5 Figure Q [One Q (q±, discharge flow rate) Figure 6 Edge - Figure 7 Figure 8 m-÷Q (discharge i amount )

Claims (1)

[Claims] 1. The rotation speed of the pump is determined by the Q-
In a speed control pump operation method that performs constant predicted terminal pressure control by varying it according to the H performance curve, the terminal flow rate is varied in advance under a constant target pressure at the end of the pipe at the initial stage of pump operation. Measure the pump discharge pressure and discharge flow rate for each terminal flow rate, and substitute the discharge pressure and discharge flow rate for each terminal flow rate into the function of the pipe load resistance curve to calculate the pipe constant and actual head. A method of operating a speed pump, characterized in that the predicted terminal pressure is controlled to be constant based on the calculated pipe line constant and the actual pump head. 2. Set the pump rotation speed to Q-, which is determined by the pipe load resistance curve.
In the speed control pump operating method, which controls the end pressure at a constant level by changing it according to the H performance curve, the end flow rate is changed in advance under a constant target pressure at the end of the pipe at the initial stage of pump operation. The rotational speed of the pump is measured for each terminal flow rate, and the Q-H performance curve of the pump at the rotational speed is calculated based on a predetermined standard Q-H performance curve, and then the discharge pressure at the rotational speed is calculated. , calculate the discharge flow rate from the Q-H performance curve of the pump corresponding to the discharge pressure, and substitute the discharge pressure and discharge flow rate for each terminal flow rate into the function of the pipe load resistance curve. A method of operating a speed control pump characterized by calculating pipe resistance and actual head, and performing predictive terminal pressure constant control based on the pipe line constant and actual head.