JPH1068388A - Liquid feeding device for service water line and pump control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To cope with the rise and the fall of a main pipe pressure when a water feeding device is coupled directly to a service water line main pipe. SOLUTION: In a liquid feeding device for a service water line having pumps 11 and 12 to feed water in a service water line main pipe 1 to the suction demand side, when a state that a pressure on the suction side of a pump exceeds a target pressure on the discharge side is continued for a given time, operation of a pump is stopped. Further, through control the operation speed of the pump, water in the service water line main pipe is sucked and the pressure on the discharge side of the pump is controlled to a target pressure and water is fed to the demand side. In the so formed liquid feeding device for a service water line, when control of the operation speed of the pump is switched so that the pressure on the suction side of the pump is adjusted to a given pressure when the pressure on the suction side of the pump is reduced, the operation speed of the pump is gradually damped to effect switching of control.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water supply apparatus using an inverter, and more particularly to a water supply apparatus suitable for directly connecting to a water main and a pump control method therefor.

[0002]

2. Description of the Related Art Conventionally, a water supply pump for water supply is directly connected to a water main from the viewpoint of preventing water contamination due to backflow and preventing erroneous measurement of a water meter (water meter) due to a water hammer. Was regulated. For this reason, as described in, for example, JP-A-59-188096, water is once injected from a water main into a water receiving tank, and the water in the water receiving tank is pumped up by a water supply pump and sent to each customer. is the current situation.

Recently, while utilizing the pressure of the water main,
In order to eliminate unsanitary receiving tanks, studies have been started on a method of supplying water by directly connecting a water supply pump to a water main. It is considered that a water supply device using an inverter is effective for this in the following points.

1) If the pressure of the water main becomes high, the operating speed of the pump can be reduced in order to keep the pressure on the pump discharge side constant, and power is saved. 2) Since the pump can be started at a low speed when it is started, the pressure of the water main is not instantaneously reduced. 3) When the pressure of the water main decreases, the water supply to the customer can be adjusted by reducing the pump operation speed by the inverter.

[0005]

When the water supply pump is directly connected to the water main, the above-mentioned advantages can be obtained, but there are the following problems. 1) When the pressure of the water main becomes higher than the target pressure on the discharge side of the pump, the pressure cannot be controlled. 2) General consumers who do not have a water supply pump receive water at the pressure of the water main, but when the pressure of the water main decreases, the customer who has the water supply pump preferentially uses the water main to use the water main. When the water is sucked and supplied, the main pipe pressure is further reduced, and it may become impossible to supply water to the general consumer, resulting in unequalness. Therefore, from the standpoint of horizontal water supply, etc., when the pressure of the water main falls below the required pressure, the water supply is throttled, and the control of the water supply pump is controlled from the control that makes the discharge side constant, and the pressure on the suction side. It is necessary to prevent the pressure of the water main from dropping. However, if the control method is switched without taking any measures, the inverter may suddenly decelerate and trip.

[0006] 3) If a water supply method directly connected to the water main is adopted, the water hammer on the suction side of the pump is affected by the influence of the terrain in which the water supply pipe is laid (undulation of the pipe, etc.) and the hydraulic gradient of the pipe. Occurs. The water supply system must ensure that this effect does not affect the discharge side of the pump. Further, it is conceivable that the main pipe pressure decreases when the water supply pump is started due to the inertia of the water and increases when the water supply pump is stopped. 4) Since the pressure fluctuation in the water main cannot be specified, the operation speed of the inverter cannot be properly determined.

SUMMARY OF THE INVENTION An object of the present invention is to provide a highly reliable water supply apparatus capable of coping with an increase and decrease in pressure of a water main, and a pump control method therefor.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a water supply system for stopping the operation of a pump that draws water from a water main and supplies the water to a demand side when a pressure on a suction side of the pump becomes higher than a discharge side target pressure. In the pump control of the liquid device, the operation of the pump is stopped when it is determined that the operation speed of the pump has reached the minimum speed and the pressure on the suction side of the pump has become equal to or higher than the target pressure on the discharge side for a predetermined time. It is achieved by doing.

Another object of the present invention is to provide a pump control for a water supply system for supplying water to a demand side by controlling the operation speed of a pump to suck water in a water main and to control a discharge side pressure of the pump to a target pressure to supply the demand side. When the control of the operating speed of the pump is switched so that the pressure on the suction side of the pump falls to the predetermined pressure when the pressure on the suction side of the pump drops below a predetermined pressure, the operating speed of the pump is gradually attenuated. This is achieved by switching the control.

[0010]

When the main pipe pressure rises and becomes higher than the discharge-side target pressure of the water supply pump, the water supply pump is stopped to save power. At this time, if it is determined that the condition for stopping the pump is continued for a predetermined time when the pump is stopped, frequent stop / start can be avoided. Since the condition of restarting the water supply pump once stopped is set when the main pipe pressure falls below the discharge side target pressure, the water supply pressure to the demand side can be kept constant.

When the main pipe pressure is reduced, the discharge side control is changed from the discharge side pressure to the discharge side target pressure to the inflow side control so that the inflow side pressure becomes a predetermined pressure which is a control switching judgment level. At the time of switching, the operating speed is not switched in a stepwise manner, but is controlled so as to gradually attenuate, so that a sudden change in pressure fluctuation can be avoided.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. FIG. 2 is a schematic configuration diagram of a water supply device (hereinafter, referred to as a water supply device) according to a first embodiment of the present invention. The water supply device of the present embodiment includes a suction pipe 2 connected to a water main 1, a plurality of (two in the illustrated example) flow paths branched therefrom, and a pump 10 provided for each flow path. 1
1, gate valves 8, 16 (9, 17) for partitioning the upstream and downstream sides of the pump for each flow path, respectively,
A water supply pipe 20 that combines each flow path on the downstream side of 6, 17
A first pressure sensor 18 for detecting the pressure on the discharge side of the pump (in this embodiment, the pressure in the water supply pipe 20), and a pressure tank 19 having an air reservoir therein and accumulating the water in the water supply pipe 10. A second pressure sensor 7 provided in the suction pipe 2 for detecting a suction side pressure of the pump (in this embodiment, a pressure in the suction pipe 2), and a control device 21 for controlling the pumps 10 and 11
Is provided.

As will be described later in detail, the control device 21 stops the operation of the pump when the pressure of the water main 1 becomes higher than the discharge side target pressure for a certain period of time, and the pressure of the water main 1 is discharged. When the pressure drops below the side target pressure, the pump is restarted. As shown in FIG. 6, the control device 21 includes inverters 26 and 27 for controlling the speeds of the pumps 10 and 11, and when the pressure of the water main 1 drops below a predetermined lower limit pressure, the target pressure Is the lower limit pressure, and whenever the suction side pressure detected by the second pressure sensor 7 becomes lower than the target pressure (lower limit pressure), the speed of the inverter is commanded to decrease,
When they are equal, the speed is maintained. When the suction side pressure exceeds the target pressure (lower limit pressure), a speed increase command is issued and the target pressure is set to a regular target value (a discharge side target pressure desired by the water supply system in advance). Thereafter, speed control reverse to the above speed control, that is, normal speed control (speed control in which the speed increases when the pressure becomes lower than the target pressure and decelerates when the pressure becomes higher) is performed.

The details will be described below. FIG. 1 is a system diagram showing an example in which a water supply device is directly connected to a water main to supply water to a customer, and each suction pipe 2-1 and 2-2 branched from the water main 1 is shown in FIG.
-2, 2-3, water supply devices 3-1, 3-2, 3 respectively
-3 is provided, and from each water supply device, customers 5-1 and
Water is supplied to 5-2 and 5-3 via the water supply pipes 4-1 and 4-2 and 4-3.

Each of the water supply devices shown in FIG. 1 has the same configuration in the present embodiment, and one of them is shown in FIG. In these water supply devices, in addition to the above-described configuration, a check valve (prevention of backflow) 6 for preventing pollution is mounted on the upstream side of the pressure sensor 7 of the suction pipe 2, and a small amount of water is used on the downstream side of the pump in each flow path. The flow switches 24 and 23 for detecting the state are attached, and the flow switches 24 and 23 of each flow path and the gate valve 1 are attached.
Non-return valves 14 and 15 are provided between the check valves 6 and 17. The pumps 10 and 11 are driven by electric motors 12 and 13 controlled by a control device 21.

FIG. 6 is a detailed block diagram of the control device 21. The control device according to the present embodiment supplies the electric power from the power supply PW to the electric motor 12 via the wiring breaker 51, the main circuit contacts 52a and 25a of the coils 52 and 25 of the electromagnetic contactor, and the inverters 26 and 27, respectively. , 13 and the motors 12, 1
3 is controlled. Various settings for each of the inverters 26 and 27 (for example, settings for the lower limit of the operating speed range of the inverters) are input from consoles (key input devices) 45 and 46.

N1 and N2, which will be described later, are signals for instructing the speeds of the inverters 26 and 27.
Reference numeral a denotes an operation command signal input line, and the electric motors 12 and 13 are operated when the switches X1 and X2 provided on the input lines 28 and 29a are turned on. Switch 3
0 indicates that the power supply unit 31
Operates to supply the control power to the power supply terminal 33, and the preparation for the automatic operation is completed.

The inverters 34 and 35 are inverters 26 and
An interface comprising a D / A converter or the like for issuing a speed command to 27, a CPU 36 of a microcomputer, a memory 37 consisting of a RAM and a ROM, and 38, 39, 40 and 41 are input / output ports is there. 4
Reference numerals 2 and 43 are switches for setting pressure and speed data.

From the switch 42, a target pressure H0, a pump starting pressure H3, a pressure H1 (point of water amount 0) which is a target value in the case of the terminal pressure constant control shown in FIG. H4 (point of the water amount Qa), a value such as a pressure i for switching from discharge-side control to suction-side control when the main pipe pressure falls below a specified value, and the switch 43 sets the operating speeds ND and NA. Set data and set PIO3
The data is read into the memory via 9, 40 (stored in the RAM). Naturally, a program such as an operation control procedure described later is written in the ROM of the memory M.
Note that ND is an initial value, and the main pipe pressure is set in advance based on the value of i.

The interface 44 is connected to the first sensor 18.
And the pressure signal detected by the second pressure sensor 7 is A /
The input port 41 is used for D conversion and reading.
Through a memory (RAM).

FIG. 3 is an operating characteristic diagram in the case of a general discharge pressure constant control system. The vertical axis shows the total head H and the horizontal axis shows the water quantity Q. Curves A, B, C, and D show that the operating speed is continuous, but the speed is NA (maximum speed), N
Pump Q when assumed to be B, NC, ND (minimum speed)
-H performance, and H0 is the discharge target pressure at this time. FIG. 4 is an operation characteristic diagram in the case of a general terminal pressure constant control system. 3 are the same as those shown in FIG. In FIG. 4, a curve E is a resistance loss curve of a water supply pipe or the like. In these control methods, the amount of water used is
When the speed changes to Qa, Qb, Qc, and Qd, the operating speed of the inverter naturally changes to NA, NB, NC, and ND, and the operating point of the pump is on the constant discharge pressure line H0 or the terminal pressure. The line changes to I, B, C, D.

Normally, a constant discharge pressure control method is often used for supplying water to an apartment or a condominium where the pipe resistance is smaller than the actual head of the pump. In the case of a long water supply pipe having a large pipe resistance with respect to the actual head, a constant end pressure control method is used. Which method is to be adopted is selected as the optimum one for the water supply system, and the operation is controlled by an operation procedure programmed in advance in accordance with the above-described operation characteristic diagram.

The effect of a change in the pressure of the water main 1 during operation according to these control methods will be described with reference to FIG. In FIG. 5, the vertical axis represents the pressure at the mounting portion of the first pressure sensor, that is, the discharge pressure (pump discharge side).

In FIG. 5, the operating point c of the water quantity Q is the same as the value shown in FIG. 3, and the operating speed NC is determined based on the value when the main pipe pressure is i (the lower limit of the fluctuation). Pump Q-
An H performance curve C is determined. If the main pipe pressure increases from i to j at this time, the pump moves to a pump QH performance curve C 'indicated by a broken line. Accordingly, the cutoff pressure naturally changes from HSC to HSC '. At this time, the example of the constant discharge pressure control method is shown as the control method.
Is reduced to the value of the calculation formula shown by the following formula 1, and the pressure is kept constant.

[0025]

(Equation 1)

When the main pipe pressure is i and the amount of water used is Q
At (0), the operating speed is reduced, and eventually reaches the minimum speed ND. Further, consider a state in which the main pipe pressure has increased to j.

If the operating speed ND does not change, the pump QH curve D moves to a curve D 'shown by a broken line.
Therefore, when the amount of water used decreases, the pressure increases along the curve D ', and exceeds H0 to reach the maximum HSD'. In this case, the operating speed ND should not be limited but updated to a lower speed, or the operating speed should reach the minimum speed every time the operating speed reaches ND and the pressure detected by the pressure sensor exceeds H0. The ND is automatically calculated and updated as described in detail with reference to FIG. As a result, even if the main pipe pressure fluctuates, the pressure on the discharge side
It can be kept constant in a certain relationship. The lower limit speed of the inverter is determined by the console 45, 4 as described above.
6 can be set in advance.

Next, the case where the main pipe pressure exceeds the planned value (pump discharge side target pressure value) will be described with reference to FIGS. In FIG. 7, the vertical axis indicates the discharge pressure, the main pipe pressure, and the inverter speed. Now, on point X on the horizontal axis, the discharge pressure is 701 at H0, and the main pressure is 7 at i.
06, and the inverter speed is at ND 711.

In this state, the main pipe pressure rises and exceeds the planned value and becomes k (for example, j = H0, k> H).
0), the main pipe pressure moves to the point 708, the discharge pressure exceeds the point H0 and reaches the point 703, and the inverter speed reaches the NMIN set on the console to 713 points. In a state where the main pipe pressure is increased, a non-control state in which the discharge side pressure of the pump cannot be controlled to the target pressure H0 cannot be achieved (above the Y 'point on the horizontal axis). Therefore, in this embodiment, since the main pipe pressure can be maintained at H0 or more without operating the pump, the operation of the pump is stopped when the non-control state is established.

FIG. 8 is a flowchart showing the operation procedure of the pump. The procedure for stopping the operation of the pump will be described on this flowchart. First, step 8
At 00, the main pipe pressure is detected by the second pressure sensor 7, and it is determined whether or not the detected value exceeds the target pressure H0 (step 802). If the result of this determination is that it exceeds H0, the routine proceeds to step 803, and after waiting for a certain time t, the main pressure is detected again by the pressure sensor 7 (step 80).
4), a re-determination is made in step 805, and even in this re-determination, H0
If so, the routine proceeds to step 806, where the operation of the pump is stopped. As described above, the pump is stopped when the main pipe pressure continuously exceeds the planned value for a certain period of time, so that power can be saved and a power saving effect can be obtained.

Next, the pressure of the main pipe drops extremely, and the pressure in FIG.
Consider a case where the pressure i at the point 09 drops to the pressure l at the point 710 (i> l) (Z → Z ′ on the horizontal axis). In such a state, water cannot be supplied to other consumers connected to the water main. Therefore, in order to protect the position such as the supply level, the control is switched from the control using the detection value of the pump discharge side pressure sensor 18 to the pressure control using the detection value of the suction side pressure sensor 7, and the speed control 81 in the normal state is controlled.
An operation reverse to the steps 0 to 813 is performed.

That is, the value detected by the pressure sensor 7 in step 809 is equal to the lower limit value i set from the switch 42.
(See FIG. 7) It is determined whether it is lower. As a result of the judgment,
If the value is lower than the lower limit value i, the process proceeds to step 814, and the value of the target pressure is replaced with the lower limit value i. And 815
The pressure H detected by the pressure sensor 7 in the step and the target pressure i
Compare with As a result of the comparison, when the main pipe pressure becomes high, the speed increasing process is performed, the process returns to step 800, and the subsequent processes are executed.

Naturally, since the pressure exceeds i, the normal 8
Processing after 10 steps will be performed. 81 above
If the determination results in the five steps are equal, the process proceeds to step 817, and no gear shift is performed. As a result of the determination, if the main pipe pressure is lower than the lower limit value i, the process proceeds to step 818 to perform a deceleration process. Then, go to step 819a,
Here, a waiting time process that does not cause a trip due to the sudden deceleration of the inverter is executed, the process returns to step 800, and the process is executed again from here.

Next, FIG. 9 shows an embodiment in which the inverter minimum speed when the main pipe pressure fluctuates (increases) at the point where the water amount is 0 in the control method of FIGS. explain.

At step 900 in the figure, initialization is performed. That is, the main pipe pressure at the time of planning is the lower limit value i, and the pump 10
As a cutoff pressure (discharge pressure) HS at a 0% operation speed, an operation speed at a water amount of 0 is obtained by the following equation 2 or 3;
This value is set as an initial value.

[0036]

(Equation 2)

[0037]

(Equation 3)

This initial value may be set in advance by the switch 43 shown in FIG. (Ji) shown in Expression 2 or Expression 3 is the pressure fluctuation value of the main pipe known at the planning stage.

Next, at step 901, the pressure detected by the pressure sensor 7 is detected. At step 902, it is checked whether or not the pressure H (for example, k) detected by this sensor has exceeded the maximum value j of the initial value of 900 steps. If so, the process jumps to step 905, and if not, the maximum value j is replaced with k in step 903. This means that the main pipe pressure rose beyond the planned value due to the influence of the water hammer. Then, the minimum value of ND can be obtained by performing processing in step 904 by replacing equation (2) or equation (3) with (ki) by replacing (ji) with (ki).

[0040]

(Equation 4)

[0041]

(Equation 5)

In Equations (2), (3), (4), and (5), H0 is the target pressure when the water amount is 0 shown in FIG. 3 and H1 is the one shown in FIG.

According to this, since the appropriate value of the lowest frequency of the inverter can be easily obtained, the pressure does not increase as shown by the curve D 'in FIG.

A second embodiment of the present invention will be described with reference to FIGS.
This will be described with reference to FIGS.

In the present embodiment, the pressure in the main pipe is not affected when the pump is started and stopped in the configuration shown in FIG.

In this embodiment, 100, 1 in FIG.
In step 01, it is determined whether or not the pressure detected by the pressure sensor 18 (load side) has decreased to the starting pressure H3 or less (FIGS. 3 and 4). As a result, if the starting pressure has been reached, 102
In a step, the first pump 10 is started at a minimum speed (not shown) determined by an initial value. Since the inverter is soft-start, it takes an acceleration time (several seconds) to reach this speed.

Next, the routine proceeds to step 103, where the main pipe side pressure is detected by the pressure sensor 7, and in step 104, the target pressure is replaced with the suction side lower limit pressure i. Then, in step 105, the pressure H detected by the pressure sensor 7 is compared with the target pressure H0 (= i).

As a result of the comparison, the detected pressure H is H0 (= i)
If it is equal to, hold the minimum speed without shifting. As a result of the comparison, when the main pipe pressure (detected pressure H) is lower than H0 (= i: lower limit pressure), 81 in FIG.
The deceleration process is performed in the same manner as in steps 8 and 819. In this way, the main pipe pressure does not decrease due to the inertia of water at the time of starting. As a result of the comparison in step 105, when the main pipe pressure (detected pressure H) becomes higher than H0 (= lower limit value i), the process proceeds to step 109, and the target pressure is returned to the value of the target pressure on the discharge side. Then, in step 110, the discharge side pressure is detected by the pressure sensor 18.

Next, based on this pressure, in step 111, the same speed control as in the processing block X shown in FIG. 8 is performed. In steps 112 to 114, after a certain period of time,
It is determined whether the flow rate sensor is ON based on the small amount of water.
If it is not ON, the process returns to step 103 for continuing the operation, and if it is ON, a search operation for stopping without increasing the pressure too high is performed in steps 115 to 118.

That is, in steps 115 and 116, a test operation is performed with the current speed reduced by, for example, about 10 Hz.
In step 117, the discharge side pressure is detected, and in step 118, it is checked whether or not this value is equal to or higher than H0 (specified value).
If the pressure is equal to or higher than H0 even if the speed is lowered by about 10 Hz from the current level, it means that water is not used at the demand end, so the operation is stopped at step 120 with the operation speed reduced. As a result of the determination at step 118, if the feed water pressure is lower than the specified value H0, the operation speed is returned to the original speed at step 119, and the process returns to step 110.
The subsequent processing is performed.

After the execution of step 120, the next step 121 replaces the machine with the idle pump, returns to step 100, and executes the subsequent processing instructions. With this configuration, the main pipe pressure does not increase due to the inertia of water at the time of stoppage, and stable operation without pressure fluctuation can be realized.

As described above, in the present embodiment, the pump (water supply device) is directly connected to the water main, and the shortage of the main pressure is pumped by the pump to send water to the demand end, and the pressure sensor 18 supplies water. The pressure sensor is provided in the pipe 20 and generates a pressure signal in accordance with the pressure therein. The pressure sensor 7 is provided in the suction pipe 2 on the suction side of the pump, and also generates a pressure signal. The plurality of inverters are speed-controlled and operation-controlled based on the relationship between the pressures detected by the pressure sensors 7 and 18 and a preset control system set value (for example, a target value). Operates as follows when is detected.

A) When the pressure of the water main becomes larger than the preset target pressure on the discharge side, and the operation speed of the inverter reaches the minimum speed, and when this state has passed for a certain period of time, the pump is stopped. When the pipe pressure falls below the target pressure, the pump is operated again.

B) When the pressure of the water main reaches a preset lower limit pressure and the operation is switched from control by the pressure sensor on the discharge side to control by the pressure sensor on the suction side, the speed signal of the inverter is changed stepwise. Instead of commanding, make it gradually attenuate.

C) When the pump is started, the inverter outputs a low speed signal. If the pressure on the suction side falls below the lower limit, the inverter maintains the speed, and if the pressure exceeds the lower limit, increases the speed. At the time of stop, before issuing a stop command, try a search operation to check whether the water usage is low, and if so, stop the inverter at a low speed so that the suction side pressure does not increase. Let it do.

D) Since the pressure fluctuation of the main pipe cannot be specified,
The lower limit value of the operating speed range of the inverter is set in advance to the minimum value, the pressure fluctuation of the main pipe is estimated and lowered in advance to match it, or the detection of the pressure sensor 7 provided on the suction side is performed. Based on the obtained pressure signal, it is automatically calculated and determined.

According to such an embodiment, the following effects can be obtained. 1) When the pressure in the water main exceeds the target pressure on the pump discharge side, stop the operation and switch to water supply at the main pressure to save power.

2) When the operation is stopped due to the use of a small amount of water, when the supply water pressure is at a specified value, the operation is performed at an extremely low speed, so that waste of power can be eliminated. When one of them is stopped and switched, the other is started at the same low speed in advance. In this case, when the pressure is equal to or higher than the specified pressure, the operation is stopped and switched, so that the pressure fluctuation is small.

3) When the speed of the pump is increased, the pump to be increased is started and fixed at Nmin before the operating pump reaches the maximum speed. When the pressure falls below the specified pressure, the speed of the booster pump operating at a fixed speed is increased, and when the speed of the deceleration and the lowering reaches 100% N, the follower is fixed at 100% N, and the preceding machine is fixed. Since the speed is reduced to Nmin and stopped when the speed reaches a specified value or more, the pressure fluctuation is minimized.

[0060]

According to the present invention, it is possible to cope with the pressure of the main pipe, to prevent the inverter from tripping even if the pressure of the main pipe drops rapidly, and to obtain a highly reliable water supply apparatus.

[Brief description of the drawings]

FIG. 1 is a system diagram of a system in which a water supply device is directly connected to a water main.

FIG. 2 is a configuration diagram of a liquid supply device according to one embodiment of the present invention.

FIG. 3 is a QH characteristic diagram of discharge pressure constant control.

FIG. 4 is a QH characteristic diagram of the terminal pressure constant control.

FIG. 5 is a QH characteristic diagram showing an influence when the main pipe pressure fluctuates.

FIG. 6 is a control circuit diagram of the embodiment of the present invention.

FIG. 7 is an operation characteristic diagram showing a relationship among a discharge pressure, a main pipe pressure, an inverter speed, and a flow rate according to the embodiment of the present invention.

FIG. 8 is a flowchart showing an operation procedure of the first embodiment of the present invention.

FIG. 9 is a flowchart showing an operation procedure of the first embodiment of the present invention.

FIG. 10 is a flowchart showing an operation procedure of the second embodiment of the present invention.

[Explanation of symbols]

1 ... water main, 2 ... suction pipe, 7, 18 ... pressure sensor,
10, 11 pump, 12, 13 electric motor, 19 pressure tank, 20 water supply pipe, 21 control device, 23, 24 ...
Flow rate sensors, 26, 27 ... inverters.

Continuation of the front page (51) Int.Cl. ⁶ Identification number Agency reference number F04D 15/00 F04D 15/00 D F04B 49/02 331F 331E (72) Inventor Kosaburo Matsuno Higashi Narashino, Narashino-shi, Chiba 7-1-1-1 Narashino Plant, Hitachi, Ltd.

Claims (7)

[Claims] 1. A pump control method for a water supply device for a water supply, comprising: stopping the operation of a pump that draws water from a water main and supplies the water to a demand side when a pressure on a suction side of the pump becomes equal to or higher than a discharge side target pressure. The operation of the pump is stopped when it is determined that the state in which the operation speed of the pump has reached the minimum speed and the pressure on the suction side of the pump has become equal to or higher than the target pressure on the discharge side has been continued for a predetermined time. Control method of pump for liquid supply device. 2. The water supply apparatus according to claim 1, wherein the pump is restarted when the suction side pressure of the pump becomes lower than the discharge side target pressure after the operation of the pump is stopped. Pump control method. 3. A pump for sucking water from a water main and supplying it to a demand side, an inverter for controlling an electric motor for driving the pump, pressure detecting means for detecting a pressure on a suction side of the pump, and pressure detecting means. Pump stop control means for outputting to the inverter a command to stop the operation of the pump when the pressure detected by the means is equal to or higher than the target pressure on the discharge side of the pump; A pump judging means for judging that the pump pressure has become higher than or equal to the discharge-side target pressure for a predetermined period of time. 4. The inverter according to claim 3, wherein, after the operation of the pump is stopped by the pump stop control means, a command to restart the pump when the pressure detected by the pressure detection means falls below the discharge-side target pressure. A water supply device for water supply, characterized by comprising means for outputting to a water supply. 5. The pump according to claim 3 or 4, wherein the operation of the pump is stopped when the flow rate of water supplied to the demand side is equal to or lower than a predetermined flow rate, and the pump is started when the discharge pressure of the pump becomes equal to or lower than the starting pressure. A water supply device for water supply, characterized by comprising means. 6. A pump control method for a water supply device for a water supply, wherein the operation speed of the pump is controlled to suck water in the water main, and the discharge side pressure of the pump is controlled to a target pressure and supplied to the demand side. When the control of the operation speed of the pump is switched so that the pressure on the suction side of the pump becomes the predetermined pressure when the pressure on the pump side becomes lower than the predetermined pressure, the control is performed by gradually attenuating the operation speed of the pump. And a pump control method for a water supply device. 7. A water supply apparatus for a water supply, which controls the operation speed of a pump to draw water from a water main and controls the discharge side pressure of the pump to a target pressure and supplies the target pressure to a demand side. When the control of the operation speed of the pump is switched so that the pressure on the suction side of the pump becomes equal to the predetermined pressure when the pressure decreases to a predetermined pressure or less, the control switching is performed such that the operation speed of the pump is gradually attenuated and the control is switched. A water supply device for water supply, characterized by comprising means.