JP4001573B2 - Pump device - Google Patents

Description

  The present invention relates to a pump device that sucks water by a pump connected to a water main and feeds it to an elevated water tank at a high position.

  FIG. 7 is a diagram showing the configuration of a conventional pump device of this type. In FIG. 7, 1 is a pump, and the pump 1 is driven by an electric motor 2. 3 is a variable speed means comprising an inverter for controlling the rotational speed of the pump 1 by controlling the rotational speed of the electric motor 2, and 4 is a high water tank installed at a high position.

When the water level L of the elevated water tank 4 is at the pump operation water level L ₂ , the water level detector 5 outputs a pump operation signal PS to the variable speed means 3 and operates the pump 1 to supply the water supply pipe 7 from the water main pipe 6. The water is sucked in by the pump 1 via the, and the discharge pressure is given by the pump 1, and the water is fed from the pumping pipe 10 to the elevated water tank 4 via the check valve 8 and the constant flow valve 9. When the water level in the elevated water tank 4 reaches the pump stop water level L ₁ , the water level detector 5 sends a pump stop signal to the variable speed means 3 to stop the pump 1.

  When the pump 1 is started as described above and water is supplied to the elevated water tank 4, when the pump 1 is suddenly started like a general pump, the water in the water supply pipe 7 is rapidly sucked into the pump, and the water hammer action As the pump 1 is started, the pressure suddenly decreases on the suction side of the pump 1, and the reduced water pressure propagates to the water main 6, and the water main 6 is adversely affected such as impact and vibration. There's a problem.

  In order not to cause the above problems, the variable speed means 3 slowly increases the operating speed of the pump 1 or more than necessary by the constant flow valve 9 provided on the discharge side of the pump 1. The flow rate is not sucked from the water main 6.

In general, as shown in FIG. 2, the relationship between the pressure loss and the flow rate of the constant flow valve causes a large pressure loss to flow the set value S. Therefore, there is a problem that the discharge pressure required for the pump 1 cannot be accurately calculated. Therefore, in general, the pump is operated at a higher discharge pressure. As apparent from FIG. 2, no matter how high the discharge pressure is, the constant flow valve restricts the discharge pressure, so it is generally necessary to keep the pump discharge pressure high. As a result, even when a constant flow valve is provided, there are the following problems.
・ The pressure loss of the constant flow valve is large.
・ Adjustment of pump discharge pressure is difficult.

  The present invention has been made in view of the above points. A pump device that eliminates the above-described problems, eliminates the need for a constant flow valve on the pump discharge side, and supplies the water sucked from the water main to the elevated water tank. The purpose is to provide.

In order to solve the above-mentioned problems, the present invention provides a pump device including a pump having a suction port connected to a water main through a water supply pipe, and a pumping pipe connected to a discharge port of the pump and feeding water to an elevated water tank. An electric motor for driving the pump, variable speed means for operating the electric motor at a variable speed, suction pressure detecting means for detecting the suction pressure of the pump, and discharge pressure detection for detecting the discharge pressure of the pump Means, pump rotational speed measuring means for measuring the rotational speed of the pump, and the pump suction pressure, discharge pressure, rotational speed based on the pump suction pressure, the discharge pressure, and the rotational speed so that the water supply flow rate to the elevated water tank is a constant flow rate. Control means for instructing the pump speed to the variable speed means, the control means so that the difference between the discharge pressure and the suction pressure coincides with the total head required for the constant flow rate. Pump times And it is characterized in controlling the number.

According to one aspect of the present invention, the pump is operated when the water level of the elevated water tank is at a pump operating water level, and is stopped when the water level of the elevated water tank reaches a stop water level .
According to one aspect of the present invention, the control means is constituted by a microcomputer.

  According to the present invention, the flow rate can be controlled without using a constant flow valve, and the pump operating power cost can be reduced without the pressure loss of the constant flow valve.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the pump device of the present invention. 1, parts denoted by the same reference numerals as those in FIG. 7 indicate the same or corresponding parts. 11 is a subtractor, 12 is table data of the operating speed and total head at a determined flow rate of the pump 1, 13 is a PI (proportional / integral) control unit, and 14 is a suction pressure detecting means for detecting the suction pressure of the pump 1. , 15 is a discharge pressure detecting means for detecting the discharge pressure of the pump 1.

The water level detector 5 outputs a pump operation signal PS to the variable speed means 3 when the water level of the elevated water tank 4 is at a predetermined pump operation water level L _2, and operates the pump 1 to supply the water supply pipe from the water main 6. Water is sucked in by the pump 1 via 7, discharged by the pump 1, given pressure, and fed to the elevated water tank 4 through the pumping pipe 10 via the check valve 8. High置水tank 4 the water level pump stop level L ₁ (as is clear from FIG. 2, the high have predetermined water level from the pump operation water level L ₂₎ is reached, the pump stop signal to the water level detector 5 the variable speed unit 3 To stop the pump 1.

  The PI pressure control unit 13 detects the discharge pressure detection means 15 and the suction pressure detection means 14 and subtracts the suction pressure from the discharge pressure of the pump 1 by the subtractor 11 and uses the subtraction result ΔP (measured total head) as a command value. At the same time, the current pump speed is measured by the pump speed measuring means (output frequency of the variable speed means 3) as a feedback signal, and the total head ΔP ′ (table head) is calculated from the table data 12 at the measured speed. The read value is input to the PI control unit 13, and the output of the PI control unit 13 instructs the variable speed means 3 to determine the pump 1 so that the measured lift ΔP and the table lift ΔP ′ coincide with each other. The flow rate is controlled.

A method for obtaining the table data 12 will be described. FIG. 3 is a diagram showing the relationship between the total head P and the discharge flow rate Q at the rotational speeds N ₀ , N ₁ , N ₂ , N ₃ , N ₄ , N ₅ , and N ₆ of the pump 1. In FIG. 3, the pump 1 rotates at every rotation speed N ₀ , N ₁ , N ₂ , N ₃ , N ₄ , N ₅ , N ₆ (actually, the rotation speed is determined more finely) at the discharge flow rate setting value Q _1. The number and the total head P are measured, the relationship between the rotational speed and the total head is graphed as shown in FIG. 4, this graph is converted into table data, and becomes table data 12.

Now, in FIG. 5, the operating point of the pump 1 is the point A, that is, the intersection A with the system curve SC at the pump rotational speed N ₂ is the pressure. Actually, the pressure in FIG. 5 is the discharge pressure, but for easy understanding, the suction pressure is zero (the suction pressure P _S detected by the suction pressure detecting means 14 is zero), that is, the total lift of the pump 1 is read. In this case, in the case of the rotation speed (output frequency of the variable speed means 3) N _{2 according} to FIG. 4, the point B, that is, the pressure is P _B. The pressure P _B = [Delta] P 'and total head of the pump 1, i.e. the discharge and by comparing the difference [Delta] P of pressure P _S = 0 suction detected by the pressure P _D and the suction pressure detection means 14 detected by the discharge pressure detecting means 15 When the pressure P _B = ΔP ′ is smaller than ΔP, the PI controller 13 increases the pump rotation speed, and the total head (discharge pressure) ΔP (suction pressure) detected by the discharge pressure detection means 15 of the pump 1. The number of revolutions of the pump 1 is controlled so that the total head pressure P _B = ΔP ′ read from the table data coincides with P _S = 0) and the number of revolutions (the output frequency of the variable speed means 3).

  By controlling the pump 1 as described above, the constant flow valve 9 is not required on the discharge side of the pump 1 as shown in FIG. 7, and the load at which the discharge pressure of the pump 1 is used, that is, a system curve. Since the pump 1 can be operated in conformity with the SC, the problem that the pressure loss of the constant flow valve is large and it is difficult to adjust the discharge pressure of the pump, as in the case of using a constant flow valve, can be solved, and the optimum operation can be performed. It becomes possible. For example, when the system curve is the dotted line SC ′ in FIG. 5, the pump 1 is operated at the intersection point a.

FIG. 6 is a diagram showing a processing procedure of a program when the control unit including the adder 11 and the PI control unit 13 of FIG. 1 is configured by a microcomputer. The processing procedure when the control unit is constituted by a microcomputer will be described. First, the output frequency Hz _OUT is set to 0 (step ST1). The output frequency Hz _OUT is commanded to the inverter of the variable speed means 3 (step ST2). The discharged read the pressure P _D of the pump 1 detected by the discharge pressure detecting means 15 (step ST3), followed by reading the suction pressure P _S has been detected by the suction pressure detection means 14 (step ST4).

The suction pressure P _S is subtracted from the discharge pressure P _D , and this subtraction value = P _D −P _S is set as the total pump head ΔP (step ST5). Subsequently, the total head ΔP ′ is read from the table data 12 by the output frequency Hz _OUT (step ST6). Subsequently, the total head ΔP measured and the total head ΔP ′ read from the table data 12 are compared (step ST7), and if ΔP <ΔP ′, a value obtained by subtracting the frequency increment DIGH from the output frequency Hz _OUT Hz _OUT −DIGHZ Is output as an output frequency Hz _{OUT to} the inverter of the variable speed means 3 (step ST8). And outputs to the inverter of variable speed means 3 as the output frequency Hz _OUT value Hz _OUT + DIGHz obtained by adding the frequency increment DIGHz the output frequency Hz _OUT if there at ΔP> ΔP '(step ST9).

In the table data 12, the performance of the pump 1 is digitized and the performance of the pump 1 is stored, the performance of the pump is converted according to the number of rotations of the pump, the flow rate is determined, and the entire pump is determined according to the flow rate. It is possible to obtain the head and tabulate the results, or provide a constant flow valve on the discharge side of the pump 1 to automatically increase the pump 1 slowly from the low speed to the maximum speed. speed subtracts a suction pressure P _S detected by the discharge and the pressure P _D detected by the discharge pressure detecting means 15 (output frequency of the variable speed means 3) the suction pressure detection means 14, total head and the subtraction value As shown in FIG.

It is a block diagram which shows the structure of the pump apparatus of this invention. It is a figure which shows the pressure loss of a constant flow valve. It is a figure which shows the relationship between the total head for every rotation speed of a pump, and discharge flow volume. It is a figure which shows the table data of the relationship between the pump rotation speed and the total head in the flow volume determined by the pump. It is a figure for demonstrating the operating point of the pump apparatus of this invention. It is a figure which shows the process sequence of the program at the time of comprising the control part of the pump apparatus of this invention with a microcomputer. It is a block diagram which shows the structure of the conventional pump apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pump 2 Electric motor 3 Variable speed means 4 Elevated water tank 5 Water level detector 6 Water main pipe 7 Water supply pipe 8 Check valve 9 Constant flow valve 10 Pumping pipe 11 Subtractor 12 Table data 13 PI control part 14 Suction pressure detection means 15 Discharge pressure detection means

Claims (3)

A pump device comprising a pump having a suction port connected to a water main through a water supply pipe, and a pumping pipe connected to a discharge port of the pump and feeding water to an elevated water tank,
An electric motor for driving the pump;
Variable speed means for variable speed operation of the electric motor;
A suction pressure detecting means for detecting a suction pressure of the pump;
A discharge pressure detecting means for detecting a discharge pressure of the pump;
A pump rotational speed measuring means for measuring the rotational speed of the pump;
Control means for commanding the pump speed to the variable speed means based on the suction pressure, the discharge pressure, and the speed of the pump so that the water flow rate to the elevated water tank becomes a constant flow rate ,
The pump device characterized in that the control means controls the pump rotational speed so that a difference between the discharge pressure and the suction pressure coincides with a total head required for the constant flow rate .   2. The pump device according to claim 1, wherein the pump is operated when a water level of the elevated water tank is at a pump operation water level, and is stopped when a water level of the elevated water tank reaches a stop water level. . 3. The pump device according to claim 1, wherein the control means is constituted by a microcomputer.

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