JPS6138193A - Variable speed water supply system - Google Patents

Abstract

PURPOSE:To enable predicted constant end pressure control by providing the necessary pressure and the rotary speed under shut-off operation of pump and the necessary pressure and rotary speed under maximum water supply to the control section and operating the target pressure for every rotary speed. CONSTITUTION:The delivery pressure of water supply pipe 7 coupled to the pumps 2, 12 to be driven through motors 1, 11 is detected through a pressure detector 8 and fed to the control section 9. The control section 9 will produce frequency signal which is fed to the inverters 13, 23 to produce power of necessary frequency thus to run the motors 1, 11 with necessary speed. The frequency produced through the inverters 13, 23 to be fed to the motors 1, 11 is also fed to the control section 9. The control section 9 is comprised of a microcomputer to operate the relation between the rotary speed and the delivery pressure under shut-off of pump system while to calculate the rotary speed and the target pressure under maximum flow and to perform operation on the basis of particular formula then to store in the memory of the controller 9. With such arrangement, predicted constant end pressure control is realized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] "Industrial Field of Application J The present invention relates to a control device for adjusting the amount of water in a water supply facility equipped with a plurality of pumps.

``Prior Art'' In water supply equipment, users at the end of piping are required to obtain the required pressure and flow rate, and it is necessary to maintain the required pressure even though the flow rate used fluctuates. Fluctuations in the amount of water used were responded to by changing the rotational speed of the turbo pump driven by the variable speed motor. In such cases, conventional control such as constant discharge pressure or constant estimated terminal pressure is performed.

FIG. 4 is an example of constant pressure control, with the horizontal axis showing the flow rate and the vertical axis showing the pressure. , 2/ is the pump performance curve. In this case, the rotational speed is controlled so that the pump discharge pressure P is the sum of the required pressure P at the piping end and the pressure loss pc of the piping at the maximum flow rate, so that the pump discharge pressure becomes a constant pressure. However, according to this method, the required pressure P at the end of the pipe fluctuates greatly because the resistance of the pipe changes in proportion to the square of the flow rate, and the range shown by diagonal lines in the figure is considered to be a loss of energy.

In the conventional control method shown in FIG. S shown in the same coordinates as FIG. 4, the pump discharge pressure P is determined in consideration of the pressure loss in the pipe line so that the estimated terminal pressure is constant.

The pump discharge pressure is changed according to a change in the pressure loss Pc of the pipeline corresponding to the flow rate, that is, a resistance curve. Figure 5 shows the required pressure at the end of the pipe in a water supply system using a pump.
The pressure loss in the piping corresponding to the flow meter equipped with a flow rate meter is estimated, and the pump discharge pressure is determined by adding the expected pressure loss to the required pressure at the end of the piping.

Such methods are expensive because they require flow meters.

In this case, since each piping is different and the pump characteristics are also different, it is necessary to apply it to each individual pump device.
Although it is possible for large-scale pump equipment, it is not suitable for mass-produced and general-purpose pump equipment.

In addition to the above, there is also a method of storing pump performance and controlling it, but it requires time and effort to collect data and can only be applied to individual systems.

Patent application filed in 1973 as the latest technology for constant estimated terminal pressure control
The variable speed water supply system of Kodazawa No. 03/ is equipped with a control device that keeps the estimated end pressure constant without having a flow meter.

"Problems to be solved by the invention" In a pump device that performs such estimated terminal pressure constant control, when trying to operate a device equipped with multiple pumps in parallel, it is difficult to calculate the target pressure in the first pump. becomes complicated. - There were drawbacks such as difficulty in appropriately determining the target pressure for additional points.

The present invention provides an additional system for calculating a control target pressure at the time of additional pump operation in a variable speed water supply system that includes a plurality of pumps and performs constant estimated terminal pressure control based on the relationship between pump rotational speed and pump discharge pressure. It is an object of the present invention to provide a variable speed water supply device having a control device having a function of calculating the rotational speed of a pump.

[Structure of the invention]

"Means for Solving the Problems" The first invention of the present application has a plurality of pumps, and is equipped with a pump rotation speed control means, a pressure detector for detecting the discharge pressure, and a pump rotation speed detection means. A variable speed water supply device that controls the estimated end pressure at a constant level by inputting the required pressure and rotational speed when the water is turned off, the required pressure and rotational speed at maximum water supply, and calculates the control target pressure for each rotational speed. Then, the rotation speed H2i during parallel operation is HZi=H2θ+
(H2J-H2A) However, HZX: Rotation speed used for control HZO: Maximum rotation speed of the first unit HZ: Rotation speed of the second unit HZA: Rotation required to produce the required pressure at maximum water supply at the time of tightening This variable speed water supply device is characterized in that it is provided with a control device that calculates a control target pressure by calculating and converting the rotational speed using an equation called speed and using the rotational speed after the calculation and conversion as the rotational speed for control.

The second invention of the present application has a plurality of pumps, is provided with pump rotational speed control means, is equipped with a pressure detector for detecting discharge pressure, and pump rotational speed detection means, and is equipped with a pressure detector for detecting the discharge pressure and a pump rotational speed detection means, so that the required pressure and rotational speed at the time of pump tightening are determined. , by inputting the required pressure at maximum water supply and the required rotational speed and calculating the control target pressure for each rotational speed, the rotational speed HZi during parallel operation is HZi=HZθ
+ (Hl2- HZB) where nzi: Rotational speed used for control HZO: Maximum rotational speed of the first unit HZ, 2: Rotational speed of the second unit HZB: Rotational speed necessary to generate the necessary pressure when the pump is closed This variable speed water supply device is characterized in that it is provided with a control device that calculates a control target pressure by calculating and converting the rotational speed using the following formula and using the rotational speed after the calculation and conversion as the rotational speed for control.

The third invention of the present application has a plurality of pumps, and is equipped with a pump rotation speed control means, a pressure detector for detecting the discharge pressure, and a pump rotation speed detection means, and the required pressure and rotation speed when the pump is closed, By inputting the required pressure at the maximum water supply and the required rotational speed and calculating the control target pressure for each rotational speed, the rotational speed HZi during parallel operation can be controlled with a variable speed water supply device that controls the estimated terminal pressure at a constant level. HZ i = H
ZO 10 (H2J-HZO) However, HZ1: Rotation speed used for control Hl: Maximum rotation speed of the first pump HZO: Maximum rotation speed of the second pump HZO: Maximum rotation speed of the first pump in target pressure calculation The pressure that became the target pressure at the time is calculated and converted using the formula that is the rotation speed required for the second pump to output when it closes, and the rotation speed after calculation conversion is used as the control rotation speed to determine the control target pressure. This is a variable speed water supply device characterized by being provided with a control device that performs calculations.

"Operation" The rotational speed H2, 23F of the second pump is detected by the rotational speed detection means, inputted to the control device, any of the constants HZA, H2B, HZO stored in the control device is used as data, and H2i The rotational speed calculated to obtain the control target pressure is determined using the calculation command of the above-mentioned formula.

"Example" First, when there is only one pump or multiple pumps with the same performance are operated at the same rotation speed, the relationship between the pump rotation speed and the pump control target pressure (discharge pressure) will be explained. One method of constant estimated pressure control is as follows.

Assuming that the flow rate is constant, the data for each pump rotation speed is calculated using a data table that stores the pressure values at each rotation speed of the pump in advance, and the data of the pump rotation speed and pressure value when the required end pressure is being produced at the maximum flow rate. control target pressure can be determined. This method of determining the control target pressure is advantageous if it is performed at each rotational speed of the pump when the pump is closed, since it can be performed without using a flow meter.

Next, a method for determining the control target pressure corresponding to each rotational speed will be described.

HZX: Pump rotational speed Px: Pressure HZX=: f(PX): L, relationship between rotational speed and pressure at pumping PA: Required pressure at maximum required water flow HZMAX: Rotational speed at required maximum water flow H2A:
Required rotational speed at tightening at PA time PB Required pressure at early stage H2B: PB Rotational speed at required maximum water flow HZMAX and PA when the rotational speed is set as required to produce the required pressure at PB L stage
The difference ΔHZ in required rotational speed at time tightening is ΔHZ=H
ZMAX-H7A Required pressure FA at the required maximum water amount and required pressure FB at the time of infancy
The difference ΔP is ΔP=PA−PB, and the control target pressure S at the midpoint between pressures FA and PB is
If the reference for V is PM, then p%=ΔPXα+IPB (θ≦α≦l), and the rotation speed that produces the flow rate corresponding to the reference control target pressure PM is HZ.
If M, then HZM=ΔHZ
Find 2 for PA-PM)/(HZMAX-HZM) and Kl, and calculate the control target pressure BV for a certain pump rotational speed HZX: HZX≦HZB 5V=FB, -,
-(1) HZB(HZX≦HZM 8V'=/X(
HZX, HZB)-l-FB...(2) HZM<HZX≦HZMAX SV=, 2X(H
ZX-HZM) + PM fist --- (3) HZMAX<HZX BV=PA ---
, (41 Determined according to the above equations (1) #(2), (31, (41).

The above-mentioned points change the rotational speed of the pump when the pump is closed to obtain the required pressure FA at the required maximum water flow, and the point of the pump rotational speed HZA that can be produced at the initial stage and the required pressure when the pump is closed (=
Terminal required pressure) The point of the pump rotation speed HZB when outputting FB is taken as a pressure-rotation speed coordinate, and these points are approximated by connecting them with a broken line via the intermediate point (PM, H2M) coordinates. . If the reference PM of the control target pressure is appropriate, such a method approximates the actual pump performance, and a practically appropriate control target pressure can be obtained.

FIG. 1 is a flow sheet showing the pump device. Pumps -, /J are driven by motors i and li whose rotational speeds are controlled by changing the frequency.
(Pump up water through the pipe, increase the pressure of the water, and discharge the pipe. /
3 and flows through check valves 6 and 16 into the water pipe. The pressure in the water pipe is detected by a pressure detector and sent to the demand side.

A signal of the discharge pressure detected by the pressure detector is sent to the control section. Control part? A frequency signal is outputted from, for example, inverters i and ii, which obtain a frequency power source using a thyristor conversion method, are operated at a required speed. Inverter/J.

The frequency generated at λ3 and sent to the motors t and ii is sent to the control unit DE.

A microcomputer is used in the control section, and it is designed to calculate in advance the relationship between the pump rotation speed and pump discharge pressure at the pump device's shut-off time, the pump rotation speed at the required maximum flow rate, and the control target pressure. It has a stored storage device.

In such a pump device, in the following, for convenience of explanation, it is assumed that pump l is operated first, and pump l is additionally operated as the flow rate increases while the end estimated pressure is controlled to be constant at the maximum rotational speed of pump l. However, in reality, the pumps alternate, so naturally pumps / and l/ may be operated in the reverse order.

In such a pump device, when the first pump l is operated independently, the control target pressure is expressed by the formula +11! 2)
(3) It can be obtained from (4).

For example, if pump l is rotating at the maximum rotational speed HZθ and the water supply load increases, it will no longer be able to follow the control target pressure, and pump l/ will be additionally operated. The method of determining the rotational speed during the additional operation of pump 11 will be explained below.

FIG. 2 is a diagram showing the relationship between pump rotational speed and control target pressure, with the horizontal axis showing the control target pressure and the vertical axis showing the pump rotational speed. In the figure, S is a curve that determines the control target pressure for two-unit operation, and when the rotation speed is below HZθ, the control target pressure during single operation is calculated, and when it is above HZθ, the control target pressure during a-unit operation is calculated. From this curve S, the control target pressure at the addition point of the second pump can be determined as the control target pressure calculated when HZi=HZθ. A curve S1 shows the relationship between the rotational speed of the independently operating pump and the control target pressure.

In the figure, Pl: 2, value of the control target pressure when the rotation speed is HZl HZMAX: Rotation speed at the required maximum water flow HZθ: Maximum rotation speed of the 1st unit PO: / of the 1st unit This is the control target pressure at the maximum rotation speed. Using FIG. 1, when the rotation speed is HZi, the control target pressure can be determined as the point P1 where a perpendicular line hanging down from the point where the horizontal line from EZi on the ordinate cuts the curve S cuts the abscissa.

Here, the rotation speed H2i used for control when calculating the control target pressure by calculating the rotation speed during parallel operation will be described. - Rotational speed HZi for calculating the control target pressure of the gold-pump pump/l HZi = H2θ0 (HZJ - HZA) -
--" (5). However, HZ
J is the rotation speed of the a-th pump //.

The third method is HZi=, HZθ+(HZ2−HZB) −
--- It is calculated as (6).

The third method is to calculate the target pressure, and if the rotational speed required for the second pump to output the pressure that became the target pressure at the maximum rotational speed of the first pump when it is closed is H2O, then HZ i =, HZθ+(HZ2−HZO)
--- It is calculated as (7).

Using these relationships, we can calculate H on the vertical axis using aSS in Figure 2.
The control target pressure SV on the horizontal axis can be determined using Zi as a variable.

FIG. 3 is a diagram showing the relationship between the flow rate and pressure of the pump device, with the horizontal axis showing the flow rate Q and the vertical axis showing the pressure. Curve R is a composite pump performance curve combining pumps 1 and 1/ during parallel operation, and the rotational speed at that time is HZMAX. Curve I is the performance curve of pump I, and the rotational speed at that time is H2θ.

If F is a resistance curve, the maximum water supply amount is at the intersection point 1g of the composite pump performance curve R and the resistance curve r, and the required pressure at that point is PA. The ordinate of the intersection of the individual pump's performance curve and the resistance curve F/9 is the control target pressure pc at the maximum rotational speed of the first pump l, and the maximum rotational speed of the first pump l is determined by pump control target pressure calculation. At the rotational speed required for the a-th pump/l to output the pressure that became the control target pressure at the time of tightening, the intersection of the performance curve of the first pump l and the resistance curve R is /? It is shown as the performance curve Re starting from .

The rotational speed when the pump is closed is H2B, and its pressure is FB. Its performance curve is shown as . The pump performance in the case of rotation speed 1 (ZA), which produces the required pressure FA at the maximum flow rate when pumps / and // are operated in parallel, is shown by the curve RA.

As seen in this diagram, since FA)PO)FB, the rotation speed of the second pump//additional point is HZA)HZO)H
2B, and the rotation speed HZ1 used for calculating the control target pressure of the second pump // is based on equation (5).
is the smallest, the rotational speed H2i according to equation (6) is the largest, and the rotational speed HZi according to equation (7) is equation (5),
(Rotation speed HZ for calculating the control target pressure obtained in step 61)
It is between i.

In equations (51, (6)), there is a slight difference between the calculated control target pressure at the additional point of the first pump ii and the control target pressure at the maximum rotational speed of the first pump l.

Equation (7) does not show this difference.

The control target pressure is calculated from the rotational speed obtained by these using equations (1) to (4). Furthermore, the relationship between HZi and SV is stored in a storage device in the control device as a function of a diagram such as the N-diagram.

Even in a variable speed water supply system in which three pumps can be operated in parallel, the rotational speed used to calculate the control target pressure of the third pump can be similarly determined.

Next, the estimated terminal pressure constant control method when operating a number of units or more is as follows.

HZ, 7; Third pump rotation speed HZ2 during parallel operation
MAX: The maximum rotational speed of the second pump during parallel operation. Same as the third pump HZ, 7 MAI. HZsa: Constant determined by the method described below. The third pump also has HZ, 70. ■ Maximum rotational speed during parallel operation HZMAX. How to decide When operating a Bonpco machine HZMAX=HZθ+(HZ2MA!-H
Z20) When operating 13 units HZMAX: HZθ+(HZO
-HZA0)+(H2,7MAI-HZJO)The first item, HZO, is the maximum rotational speed of the first pump, and the second item, HZO, is the maximum rotational speed of the second pump. The power frequency is 60Hz.

■ How to determine the rotational speed HZi used to calculate the control target pressure When operating the Bonpco table H2i = = HZθ + (HZJ - HZ
Jc) When operating 13 units HZi: HZQ+ (HZO-
H2I) + (HZj - HZ, IC) As described above, during parallel operation, use the value calculated as the maximum rotational speed HZMAX for determining the calculation formula, and use the value calculated with @ when calculating the control target pressure SV. The rotational speed HZi is used.

The method for determining the constants H2, 2C and HZIO is as follows.

■ How to determine constant HZ, 20 Step 1 Control target pressure E3VHZe is 5VHZe =KJ (HZO-HZM)-)-PM However, HZθ≧HZM Or BVH26=to/(HZO-H2B)-4-PR However, HZO(HZM Step λ ゛HZJO is the wave number of cutting chips when the control target pressure 8VBZs is tightened to the initial pressure.If the function form showing the tightening characteristics is T and +H2EII, HZJO=LH28I (B
VmZe).

■ How to determine constant HZ30 Step 1 When the maximum rotational speed of the second pump added during parallel operation is greater than or equal to the maximum rotational speed HZθ of the first pump,
Control-Target pressure SVHZ2MA: ¥ is SVnz2MAX = 2 (H2JMAX-HZM
) 10PM However, HZJMAX ≧H2M or BVHZtMhx=Kt (HZJMAX-H2B)
-1-FB However, it is also referred to as HZt2MAI (HZM).

Step λ If the rotation speed at the time of tightening the control target pressure 8VBzIM*X and the initial pressure is HZJC, then H730=LH
Determined by 2B engineering (SVH22MAl).

In addition, constant H2, 201 (: HZB is used, constant HZ3
HZA may be used for 0.

〔Effect of the invention〕

The present invention has a plurality of pumps, and is equipped with a pump rotation speed control means, a pressure detector for detecting the discharge pressure, and a pump rotation speed detection means. Input the required pressure at each rotation speed and the required rotation speed, and calculate the control target pressure for each rotation speedζ
From this, in a variable speed water supply system that performs constant estimated terminal pressure control, the rotation speed HZ1 during parallel operation is HZ i == HZ
θ+(HZ2-HZconst) However, nzi: Rotational speed used for control HZθ: Maximum rotational speed of the first pump HZConi added λ Rotational speed of the second pump H2aonst: One of the following constants Required rotational speed HZB: Required rotational speed to generate the required pressure when the pump is closed HZC: The pressure that became the target pressure at the highest rotational speed of the first pump when calculating the target pressure. A variable speed water supply device equipped with a control device that calculates a control target pressure by calculating and converting the rotational speed required to output at the time of closing, and using the pump rotational speed after the calculation and conversion as the pump rotational speed for control. Therefore, the control target pressure can be calculated regardless of the number of pumps, which not only reduces the number of calculation equations, but also makes it possible to appropriately determine the control target pressure at the point where the pumps are added.

[Brief explanation of the drawing]

Fig. 1 is a flow sheet of the pump device of the example, Fig. 2 is a diagram showing the relationship between pump rotational speed and control target pressure, Fig. 3 is a diagram showing the pump performance curve, Fig. The figure is a diagram for explaining control of water supply pressure in a conventional example. Patent applicant Ebara Corporation Ebara Electric Co., Ltd.

Claims (1)

[Claims] 1. It has a plurality of pumps, is provided with pump rotation speed control means, is equipped with a pressure detector for detecting discharge pressure, and pump rotation speed detection means, and is equipped with a pressure detector for detecting discharge pressure and a pump rotation speed detection means to detect the required pressure when the pump is closed. By inputting the rotation speed, the required pressure at maximum water supply, and the required rotation speed, and calculating the control target pressure for each rotation speed, this variable speed water supply device controls the estimated end pressure at a constant level. Rotation speed HZi is HZi = HZθ + (HZ2 - HZA) where HZi: Rotation speed used for control HZθ: Maximum rotation speed of the first pump HZ2: Rotation speed of the added second pump HZA: At maximum water supply The invention is characterized in that it is equipped with a control device that calculates a control target pressure by calculating and converting the rotational speed according to an equation of the rotational speed necessary to produce the necessary pressure at the time of tightening, and using the rotational speed after the calculation and conversion as the control rotational speed. Variable speed water supply device. 2. It has multiple pumps, is equipped with a pump rotation speed control means, is equipped with a pressure detector for detecting the discharge pressure, and a pump rotation speed detection means, and is equipped with a pressure detector for detecting the discharge pressure and a pump rotation speed detection means to determine the required pressure and rotation speed when the pump is closed, and the maximum water supply. In a variable speed water supply system that performs constant estimated terminal pressure control by inputting the required pressure and required rotational speed at each rotational speed and calculating the control target pressure for each rotational speed, the rotational speed HZi during parallel operation can be calculated as HZi= HZθ+(HZ2-HZB) HZi: Rotation speed used for control HZθ: Maximum rotation speed of the first pump HZ2: Rotation speed of the added second pump HZB: To generate the necessary pressure when the pump is closed 1. A variable speed water supply device comprising: a control device which calculates a control target pressure by calculating and converting the rotational speed according to a formula representing the rotational speed necessary for the rotational speed, and using the rotational speed after the calculation and conversion as the rotational speed for control purposes. 3. It has a plurality of pumps, and is equipped with a pump rotation speed control means, a pressure detector for detecting the discharge pressure, and a pump rotation speed detection means, and is equipped with a pressure detector for detecting the discharge pressure and a pump rotation speed detection means. In a variable speed water supply system that performs constant estimated terminal pressure control by inputting the required pressure and required rotational speed and calculating the control target pressure for each rotational speed, the rotational speed BZi during parallel operation can be calculated as BZi = BZθ + (BZ2-
BZC) However, HZi: Rotation speed used for control HZθ: Maximum rotation speed of the first pump HZ2: Rotation speed of the added second pump HZC: When the maximum rotation speed of the first pump is determined by target pressure calculation The pressure that has become the target pressure is calculated and converted using the formula of the rotation speed required for the second pump to output when it closes, and the control target pressure is calculated using the rotation speed after calculation conversion as the control rotation speed. A variable speed water supply device characterized by being provided with a control device that