JPH10339272A - Pumping device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control the pressure on the water supply side by obtaining the differential pressure between the pressure detection signal to detect the water supply pressure on the discharge side of a pump and the reference pressure signal, and controlling the speed of the pump so that the differential pressure signal is agreed with the target pressure loss corresponding to the rotational speed of the pump. SOLUTION: The actual discharge pressure signal PV of a pump 1 to be outputted from a pressure detecting means 3 is inputted into a differential pressure signal output means 9 to generate the differential pressure signal DPV between the actual discharge pressure signal PV and the reference pressure signal PB. The rotational speed signal HZX of the pump 1 is inputted in a target pressure loss output means 7 from a rotational speed detecting means 6 to operate the target pressure loss DSV corresponding to the pipeline loss from the pump 1 to the end on the water supply side corresponding to the water consumption. The operated target pressure loss DSV is compared with the differential pressure signal DVP, and a motor 4 is controlled to the prescribed rotational speed by a variable speed changing means 5 so that the differential pressure signal DPV is agreed with the target pressure loss DSV through the PI control, etc., by a rotational speed control means 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pump device in which a pump is supplied at a predetermined pressure by using a variable speed means such as an inverter, and more particularly to an estimation terminal for controlling a supply water pressure at a demand destination terminal to be constant. The present invention relates to a constant pressure control type pump device.

[0002]

2. Description of the Related Art Conventionally, by controlling the speed of a pump while calculating an appropriate target pressure one by one according to the rotation speed of the pump, the pressure on the pump discharge side can be reduced to a predetermined target value without using an expensive flow meter. Pump devices that control the pressure are known. In such a pump device, there is a demand on the consumer side at the end of the water distribution pipe to obtain a required pressure and flow rate, and a turbo pump driven by a variable speed means such as an inverter drives a pump motor with respect to fluctuations in the amount of water used. This was addressed by changing the rotation speed. However, in order to keep the terminal pressure of the demand destination of the pump device constant irrespective of the amount of water used, it is necessary to determine the discharge pressure of the pump in consideration of the loss pressure according to the amount of water used in the water distribution pipeline.

FIG. 3 is a graph showing the operation characteristics of a pump. The horizontal axis represents the amount of water, the vertical axis represents the head, and the curve Hzx represents the operating characteristics at a constant pump rotation speed. Here, the resistance curve R is a pipe loss according to the amount of water used from the pump to the end of the demand, and is proportional to approximately the square of the amount of water used. Therefore, in order to control the pressure on the discharge side of the pump to be constant, the rotational speed of the pump may be controlled between Hza and Hzb so that the pressure Pb is constant. In, it is necessary to anticipate pipeline loss according to the amount of water used,
It is necessary to control the pump rotation speed between Hzo and Hzb in consideration of this loss.

[0004] FIG. 4 is a block diagram of a conventional system for controlling a constant estimated end pressure of a pump device. This pump device
The pump includes a pump 1, a water supply pipe 2 connected to an inflow side and a discharge side of the pump, and a pressure detector 3 for detecting a water supply pressure at a pump discharge side of the water supply pipe. And this pump 1
Is driven by a motor 4, and power of a required voltage and frequency is supplied from a variable speed means 5 such as an inverter to the motor 4, and the pump is operated at a variable speed. The variable speed means 5 receives a rotation speed command from the rotation speed control means 10. This rotation speed command is the actual pressure PV on the pump discharge side,
The target pressure DV from the target pressure output means 7A corresponding to the actual rotation speed from the variable speed means is compared, and the rotation speed is controlled so that they match.

As described above, the conventional rotation speed control means 10
, The actual pressure signal PV of the pump and the target pressure signal DV were input and compared. When the discharge pressure signal PV of the pump is, for example, a pressure value of 0 to 1 MPa, 0 to 5 V (D
When transmitting as an analog signal in C), the loss pressure is generally considerably smaller than the actual head, and is at most 0.
Assuming 1 MPa, the voltage change of the analog signal is 0 to
It was as small as about 0.5 V (DC). Considering a case where a signal is transmitted as 8-bit digital data by a microcomputer or the like, the resolution is 1 MPa at 256 (step).
When the loss pressure component was at most 0.1 MPa, control could be performed only with a resolution of 25 (step).

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a pump device of a constant estimated terminal pressure control system capable of controlling demand side terminal water pressure with good accuracy. With the goal.

[0007]

A pump device according to the present invention comprises:
A pump and a water supply pipe connected to the discharge side of the pump;
Pressure detection means connected to the water supply pipe and outputting a discharge pressure signal PV representing the water supply pressure, a motor connected to the pump for driving the same, variable speed means for shifting the motor, and detection of the rotation speed of the pump And a rotation speed signal H representing the rotation speed.
a rotational speed detecting means for outputting zx, and a target loss pressure corresponding to the rotational speed represented by the rotational speed signal Hzx of the pump.
Target loss pressure output means for outputting a DSV, reference pressure setting means for setting a reference pressure and outputting a reference pressure signal PB, and a differential pressure signal DPV between the pressure detection signal PV and the reference pressure signal PB
Differential pressure signal output means for outputting the target loss pressure DSV
And a rotational speed control means for outputting a speed signal MV to the variable speed means and controlling the speed of the pump so that the differential pressure signal DPV coincides therewith.

According to the present invention described above, before the actual pressure is compared with the target pressure in the rotational speed control means, the actual differential pressure obtained by subtracting the actual head from the actual pressure corresponds to only the line loss. Since the target loss pressure is compared with the target loss pressure, the control for the loss pressure can be performed in the full range of the comparator. This makes it easy to control the rotation speed by the rotation speed control means, and enables highly accurate control.

[0009]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a block diagram showing a pump device according to an embodiment of the present invention. A pump 1, a water supply pipe 2 connected to an inflow side and a discharge side of the pump, a pressure detector 3 for detecting a pressure on a discharge side of the pump, and a motor 4 for driving the pump.
The configuration of the pump device including the variable speed means 5 for supplying a variable frequency / variable voltage to the motor 4 is the same as that of the prior art.

The control device of this embodiment compares the reference pressure setting means 8 corresponding to the actual head of the pump with the output signal PV of the pressure detector for detecting the pressure on the discharge side of the pump. A differential pressure signal output means 9 for outputting the differential pressure output signal DPV. Here, the reference pressure setting means 8 is a setting means for setting an output voltage using, for example, a potentiometer, and the differential pressure signal output means 9 is, for example, an analog comparator. The rotation speed detection means 6 detects the actual rotation speed commanded to the motor from the variable speed means 5 such as an inverter, and outputs it as Hzx. Target loss pressure output means 7
Is means for outputting a pressure DSV corresponding to a pipe loss corresponding to the input rotation speed signal Hzx. The rotation speed control means 10 sends the speed signal MV to the variable speed means 5 so that the target loss pressure signal DSV and the differential pressure output signal DPV obtained by subtracting the reference pressure corresponding to the actual head from the actual pressure on the pump discharge side coincide. It is a means to output and speed control the pump. The rotation speed control means 10 is, for example, a PI control circuit. In the present embodiment, the rotation speed detection means 6, the target loss pressure output means 7, and the rotation speed control means 10 are each processed by calculation using a microcomputer or the like.

FIGS. 2A and 2B are block diagrams for explaining the estimated terminal pressure constant control system of the present invention in comparison with the conventional technology. FIG. 2A shows the conventional system, and FIG. 2B shows the system of the present invention. Show. That is, the conventional estimated terminal pressure constant control method is based on the target pressure SV obtained by adding the line loss pressure to the actual head obtained from the actual discharge pressure PV of the pump and the actual rotation speed of the pump.
Are compared by the rotation speed control means 10 and a rotation speed command MV is output to the variable speed means 5 so that the two values match. Thus, the pump rotation speed is controlled so that the actual detected pressure and the target pressure obtained by adding the required pipe loss to the actual head are equal.

On the other hand, in the method of the present invention, in order to compare the actual pressure PV of the pressure detector with the target pressure, the target pressure is separated into a reference pressure PB corresponding to the actual head and a target loss pressure DSV. The differential pressure DPV between the actual pressure PV detected by the pressure detector and the reference pressure PB corresponding to the actual head is detected by the differential pressure output detecting means 9.
It is calculated by Then, the differential pressure output DPV is compared with a target loss pressure DSV, which is a target pipe loss corresponding to the rotational speed, by the rotational speed control means 10, and a rotational speed command MV is output so that they match. Thus, the rotation speed control means 1
0 is common in that the actual pressure and the target pressure corresponding to the rotational speed are compared, and the rotational speed of the pump is controlled by the rotational speed control means so that they match. And the target loss pressure DSV.

The actual discharge pressure signal PV of the pump output from the pressure detection means 3 is input to the differential pressure signal output means 9, and the differential pressure signal of the pressure signal PV and the reference pressure signal PB output from the reference pressure setting means 8 is obtained. Output DPV. This corresponds to the differential pressure obtained by subtracting the pressure corresponding to the constant actual head, regardless of the amount of water used, from the actual discharge pressure on the pump discharge side as described above.

On the other hand, the rotational speed signal Hzx of the pump from the rotational speed detecting means 6 is inputted to the target loss pressure output means 7. The rotation speed detecting means 6 is a variable speed means 5 such as an inverter.
If the speed signal MV is read in the microcomputer, no special equipment is required. The target loss pressure output means 7 is a means for calculating and outputting a pump rotation speed, that is, a loss pressure corresponding to a pipe loss from the pump to the demand side end corresponding to the amount of water used.

In the target loss pressure output means 7, for example, K1 = (PA-PB) / (HzO-HzB) where: HzB; rotation speed at the time of shutoff at the reference pressure PB HzO; maximum rotation speed (50 Hz or 60 Hz) PA; Pump discharge pressure at Hz0 PB; Reference pressure (target pressure at flow rate 0) A coefficient K1 derived by the following equation is calculated. Then, the target loss pressure DSV when the rotation speed signal Hzx is input
Are sequentially calculated by DSV = K1 * (Hzx-HzB).

The output target loss pressure DSV is compared with the differential pressure signal DPV output from the differential pressure signal output means, and the rotational speed control means 10 controls the differential pressure signal DPV to the target loss pressure signal DSV by PI control or the like. The speed is controlled so as to match. That is, when the differential pressure signal DPV is lower than the target loss pressure DSV, the rotation speed control means 10 increases the speed signal MV to the speed increasing side,
When the differential pressure signal DPV is higher than the target loss pressure DSV, the speed signal MV is changed to the deceleration side.

The speed signal MV is, for example, 0 to 10 V (DC)
The variable speed means 5, for example, the inverter receiving the voltage signal, outputs 0-10V to the motor speed signal 0-50H.
z, and speed-controls the motor to a predetermined rotation speed.
The transmission of the signal between the rotation speed control means 10 and the variable speed means 5 may be digital data transmitted by serial communication instead of analog 0 to 10 V (DC).

According to the configuration of the control device, the differential pressure output DP
V is, for example, 0 to 5 MPa (D
If the full range is set so as to be transmitted as the analog signal of C), the change in the differential pressure obtained by subtracting the pressure corresponding to the actual head from the actual pressure of the pressure detector output is 0-0.
In the case of 1 MPa, the voltage change is 0 to 5 V (DC), and control can be performed with ten times the accuracy of the conventional art. Considering the case where the differential pressure output DPV is transmitted as 8-bit digital data by a microcomputer or the like, the resolution is set to a loss pressure of 0.1.
Since the MPa can be divided into 256 steps with 8 bits, the resolution can be improved by a factor of 10 compared to the conventional case where the full range is from 0 to 1 MPa. Actually, since it is necessary to consider the fluctuation to the minus, it is also conceivable to set ± 0.1 MPa. Even in this case, the resolution can be improved five times.

Further, when it is desired to keep the discharge pressure constant, there is no loss pressure in the pipeline, so it is sufficient to control so that the loss pressure DSV always becomes zero. At this time, the pump rotation speed is controlled so that the differential pressure DPV input to the rotation speed control means 10 becomes zero.

In the above-described embodiment, an example has been described in which the reference pressure setting means 8 and the differential pressure signal output means 9 are constituted by analog circuits. However, these are all constituted by digital circuits such as microcomputers. Of course, it is good. In this case, it is necessary to provide an A / D converter for converting the analog output of the pressure detector 3 into a digital output.

Further, the pump device of the above embodiment can be used as a so-called direct connection type pump device in which the inflow side water supply pipe is directly connected to a water main pipe or the like. In this case,
For example, it is necessary to provide a pressure detector on the pump inflow side and perform processing such as correcting the rotation speed coefficients Hzo and Hzb in the target loss pressure output means by calculation in accordance with the fluctuation of the pump inflow side pressure.

[0023]

As described above, the present invention separates the target pressure into an amount corresponding to an actual head and an amount corresponding to a pipe loss in the constant control method of the estimated end pressure of the pump device, and converts the amount corresponding to the pipe loss into a pump. This is a comparison with a differential pressure obtained by subtracting an amount corresponding to the actual head from the actual pressure on the discharge side. Therefore,
The comparison with the actual differential pressure with respect to the pipe loss equivalent can be performed in a large range. Therefore, the control accuracy of the estimated terminal pressure constant control can be easily improved without substantially changing the hardware configuration of the pump device.

[Brief description of the drawings]

FIG. 1 is a block diagram of constant control of estimated terminal pressure of a pump device according to an embodiment of the present invention.

FIG. 2 is a block diagram in which (A) a conventional method and (B) a method according to the present invention are compared with each other.

FIG. 3 is a Q (flow rate) / head (H) diagram showing operating characteristics of the pump.

FIG. 4 is a block diagram of constant control of estimated end pressure of a conventional pump device.

[Explanation of symbols]

 Reference Signs List 1 pump 2 water supply pipe 3 pressure detector 4 motor 5 variable speed means (inverter) 6 rotation speed detection means 7 target loss pressure output means 8 reference pressure setting means 9 differential pressure signal output means 10 rotation speed control means

Claims (1)

[Claims] 1. A pump, a water supply pipe connected to a discharge side of the pump, pressure detection means connected to the water supply pipe and outputting a discharge pressure signal PV representing the water supply pressure, and a pump connected to the pump. A motor to be driven, variable speed means for shifting the speed of the motor, rotation speed detection means for detecting a rotation speed of the pump and outputting a rotation speed signal Hzx representing the rotation speed, and a rotation speed signal Hzx of the pump. Target loss pressure output means for outputting a target loss pressure DSV corresponding to the rotation speed, reference pressure setting means for setting a reference pressure and outputting a reference pressure signal PB, the pressure detection signal PV and the reference pressure signal
A differential pressure signal output unit that outputs a differential pressure signal DPV of PB, and a speed signal MV is output to the variable speed unit to control the speed of the pump so that the differential pressure signal DPV matches the target loss pressure DSV. A pump device comprising a rotation speed control means.