JPS60142097A - Variable speed water feed device - Google Patents

Abstract

PURPOSE:To make it possible to maintain the pressure at the terminal end of a pipe line at a constant value under control of less labor in a short time, by previously setting a desired control pressure at every rotational speed of a pump and as well by providing a control device for changing the desired control pressure in association with variations in the rotational speed of the pump. CONSTITUTION:A constant K which is obtained from the relationship between the rotational speed of a pump and the discharge pressure of the pump in its fully closed pump condition and the rotational speed of the pump in such a condition that a required maximum pressure is fed under a necessary pressure, is delivered to a function generator 27. The function generator 27, an adder 28 and a pressure setting unit 29 receive the rotational speed of the pump and compute a desired control pressure which is delivered to an adjusting meter 30 that computes a control signal for the rotational speed of a motor in accordance with a system pressure from a pressure sensor 31 and the desired control pressure using, for example, PI, and delivers the thus computed control signal to the motor to control the terminal end discharge of a pipe line at a substantially constant value. With this arrangement there is required no flowmeter for controlling the terminal end discharge of the pipe line at a constant value, and as well the terminal end pressure of the pipe line may be held constant with less labor in a short time.

Description

[Detailed description of the invention] The present invention relates to a control device that adjusts the amount of water in water supply equipment.

In water supply equipment, the user at the end of the piping has a request to obtain the required pressure and flow rate, and although the flow rate used fluctuates, it is necessary to maintain the required pressure. Fluctuations in the amount of water used were responded to by changing the rotational speed of the turbo pump driven by a variable speed motor. In such cases, conventional control such as constant discharge pressure or constant estimated terminal pressure is performed.

FIG. 1 shows an example of constant pressure control, with the horizontal axis showing the flow rate and the vertical axis showing the pressure. / 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 pipe end required pressure Pn and the pressure loss P0 of the pipe line at the maximum flow rate, and the pump discharge pressure is a constant pressure. However, according to this method, since the resistance of the pipe changes in proportion to the square of the flow rate, the required pressure Pn at the end of the pipe fluctuates greatly, 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. 2, which uses the same coordinates as in FIG. 1, the pump discharge pressure P″lr is determined in consideration of the pressure loss in the pipeline so that the estimated end pressure is constant.

The pump discharge pressure is changed according to a change in pressure loss P0 in the pipeline corresponding to the flow rate, that is, a resistance curve. Figure 2 shows the required pressure at the end of the piping in water supply equipment using a pump.
A flow meter is provided to measure the flow rate, and the pressure loss in the piping corresponding to the flow meter is taken into consideration, 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.

SUMMARY OF THE INVENTION An object of the present invention is to provide a pump device in which the required end pressure is kept approximately constant by controlling the control target pressure that changes with changes in rotational speed.

The present invention includes a pump, a water supply pipe connected to the discharge side of the pump, a pressure detection means connected to the water supply pipe, a motor connected to the pump to drive it, and a rotation speed control means for controlling the rotation speed of the pump. , a variable speed water supply device equipped with a speed detection means for detecting the rotational speed of a pump, wherein the rotational speed control means uses an output signal from the speed detection means as an input signal to adjust the rotational speed of the pump to a predetermined rotational speed of the pump. A control target pressure output section that outputs a corresponding control target pressure based on the relationship with the control target pressure for each rotation speed, and an output signal from the control target pressure output section and an output signal from the pressure detection means are input. The variable speed water supply device is characterized by comprising a rotation speed control section that outputs a control signal for the rotation speed of the pump as a signal.

Note that if the speed detection means ζ of the present device uses speed data during rotational speed control, it is natural that there is no need to provide a special speed detector.

A first embodiment of the present invention is that in the present invention, the relationship between the rotational speed predetermined in the control target pressure output section and the control target pressure for each rotational speed is: Based on the rotational speed of the pump and its discharge pressure value when the required pressure is reached, and the rotational speed of the pump and its discharge pressure value when the specified flow rate is flowing at the required pressure for It is a variable speed water supply device that is set in a function or data table state. Here, the required pressure corresponds to the discharge pressure because the pump is running at full capacity, but in ■, the required pressure is the desired pressure at the piping terminal taking into account the pressure loss due to the piping in the system. It means pressure, which is smaller than the discharge pressure at that time. Note that in the latter case, it is also possible to employ data at λ or more flow rate values.

A second embodiment of the present invention is, in the present invention, when the pump is in a closed operation based on the relationship between the rotational speed predetermined in the control target pressure output section and the control target pressure for each rotational speed,
■When the maximum flow rate required by the thread is flowing through the system at the required pressure, and ■When any flow rate other than the maximum flow rate (generally a flow rate smaller than the maximum flow rate is selected) is flowed at the required pressure. This is a variable speed water supply device that is set in a function or data table based on the pump rotational speed and discharge pressure value in each state when the pump is in use.

In a third embodiment of the present invention, a predetermined flow rate is caused to flow at a required pressure into the system based on the relationship between the rotational speed predetermined in the control target pressure output section and the control target pressure for each rotational speed. A variable speed water supply device that is set in a function or data table state based on the rotation speed and corresponding discharge pressure value in each state when operating at various rotation speeds when the pump is closed and when the pump is closed. It is.

The fourth embodiment of the present invention is such that the relationship between the rotational speed predetermined in the control target pressure output section and the control target pressure for each rotational speed is as follows. and ■ any constant flow rate other than the above predetermined flow rate (
(generally a flow value smaller than the maximum flow rate is chosen) and can be set in a function or data table state based on the pump rotational speed and corresponding discharge pressure value when operating at various rotational speeds. It is a variable speed water supply device.

Further, the embodiments 1, lt, and A of the present invention are embodiments in which a thyristor conversion type frequency power source is used for the above-described present invention, and in the inverter control type, the rotational speed of the pump is detected. Exceptional rotation d1”
Even if the pump is not provided, the rotational speed of the pump can be determined from the frequency.

Further, the second invention of the present invention provides a method for controlling the rotational speed of the pump set in the control target pressure output section and the control target pressure for each rotational speed of the pump in the rotational speed control means in the first invention. A reset unit with a function to correct the relationship is added, and the maximum flow rate when determining the relationship between the preset pump rotation speed and the control target pressure for each pump rotation speed during normal use. If a flow rate higher than that flows into the system, the flow rate value will be used as the new maximum flow rate and the relationship between the pump rotation speed set in the control target pressure output section and the control target pressure for each pump rotation speed will be corrected again. This is what I did.

Examples of the present invention will be described below. FIG. 3 is a diagram showing, in three-dimensional coordinates, the characteristics of a water supply facility using a non-compressible pump such as a turbo pump. The vertical axis shows the rotation speed (rotation speed) ω of the pump as a percentage with the specified rotation speed as 100, and the horizontal axis shows the pump discharge amount (flow f4) Q.
As the intersection point M-i of the coordinates of speed and discharge amount, coordinates indicating pump discharge pressure P are shown perpendicular to these coordinates.

The three groups of parallel ω-Q curves on the characteristic curved surface S shown as a mesh represent the relationship between the rotational speed of the pump and the discharge amount at the end of the piping of the water supply equipment using the pump discharge pressure as a parameter, and ω The P-ω curve group that intersects with the third group of -Q curves shows the relationship between the rotational speed of the pump and the pump discharge pressure using the flow rate Q as a parameter.

The characteristic curved surface S is ω-
The ω-Q curve 3-i (i:/, 2.
) is obtained as a cutting line of the characteristic curved surface S on a plane parallel to the plane containing the ω-Q coordinate.

By cutting the characteristic curved surface S with a plane that crosses the Q coordinate axis indicating the predetermined flow rate and is parallel to the plane containing the P-ω coordinate,
A P-ω curve corresponding to the discharge amount Q is obtained as a cutting line of the characteristic curved surface S on a plane parallel to the plane containing the ω coordinate.

When the characteristic curved surface S is cut by a horizontal plane, a modified Q-H curve (modified pump performance curve) is obtained.

Therefore, in the present invention, in a variable speed water supply device in which a water supply pipe is connected to the discharge side of a pump driven by a prime mover, and the water supply pipe is equipped with pressure detection means and means for detecting the rotational speed of the pump, the rotational speed of the pump is adjusted in advance. A control device is provided that determines a control target pressure that is expected to be close to the pressure at each water supply pipe end, and changes the control target pressure in accordance with changes in pump rotational speed.

From the above, assuming that the flow rate is constant, we can use a data table that stores the pressure values at each rotational speed of the pump in advance, and data on the pump rotational speed and pressure value when the required end pressure is being produced at the maximum flow rate. A control target pressure can be determined for each pump rotation speed. This method of determining the control target pressure is advantageous because it can be performed at each pump rotational speed when the pump is closed, without using a flowmeter.

Next, an example will be described in which the control target pressure corresponding to each rotational speed of the pump when the pump is closed is determined.

ωX: Rotational speed PX: Pressure ωx ”” (Px) Relationship between rotational speed and pressure at closing PA: Required pressure at maximum water flow ωMAX: Required rotation speed at maximum water flow ωA,: Closing at time A When the required rotational speed is PBIIL/the required rotational speed at minimum required pressure ωBe''B at If the reference is P, then Pm = △P x α 0 FB ((17≦α≦l) and the rotation speed that produces the flow rate corresponding to the reference control target pressure PIn is ω. Then ω. - △ ω x β 0 f(Pm) (O≦β≦/)\Now, +-("m ''B)/(ω□-ωB)x2-(pA
-pm)/(ωMA!-ωm)(!: Considering KIIK2, the control target pressure sv for a certain pump rotational speed ωX is ωX≦ωB S■=PB... (1) ωB<G)x
≦ω, SV-,, X (ω8-ωB)+PB...
...(2)0)mriωwork≦ω, AX SV=2X(ω
x ”m)-1-”m...(31ωMAI<ωX
S■=PA ・・・(4) Above (11, (2+, +
31. (Determined according to formula 41.

Figure 3 is a flow sheet showing the pump device. A pump 12 driven by a motor // whose rotation speed is controlled by changing the frequency pumps water from a water source 13 through a suction pipe /4', pressurizes the water, and discharges it to a discharge pipe is. The pressure in the discharge pipe IS is detected by a pressure detector/B,
Check valve/7. The water is sent to the demand side through the water supply pipe 19 via the gate valve ig.

A signal of the discharge pressure of the pump 12 detected by the pressure detector/6 is sent to the control section 21. Control part 2
A frequency signal is outputted from 1 and inputted to an inverter 22 which obtains a frequency power source using, for example, a thyrisk conversion system, and the inverter 22 outputs a required frequency and sends it to motor ii to operate motor/l at a required speed. The frequency generated by inverter 2 and sent to motor 1/ is sent to control unit 2/.

A microcomputer is used in the control unit 2/, and the relationship between the pump rotational speed and the pump discharge pressure at the time of shutoff of the pump device, the pump rotational speed at the required maximum flow rate, and the control target pressure mentioned above is determined in advance. The life of calculating◆
It is equipped with a storage device in which the information is stored.

FIG. 5 is a flowchart showing the operation.

Pressure detector/4 changes with changes in the flow rate used. That is, as the flow rate used increases or decreases, the value of the pressure signal S/ indicated by the pressure detector lB decreases or increases.

The pressure signal S/ indicated by the pressure detector/B is sent to the control section 21.

The control unit 21 receives signals S, 2 sent from the two inverters.
is sent to routine 10θ, and as already mentioned, it is closed in routine/θθ to calculate the initial pump pressure-frequency characteristic, the local wave number pressure at maximum flow rate (maximum flow dark voltage), the required shutoff pressure at setting PB1, and the required pressure at maximum flow rate. The control target pressure SV is calculated using PA or the like. The determined control target pressure SV is then determined in routine 10/ by using the difference between the pressure signal Sl and the control target pressure SV, the rate of change of the difference, etc., and a frequency output signal so that the pump discharge pressure P approaches the control target pressure SV. I'm angry (
P1 performance 3 yen) is output to the inverter 22. The control unit 21 changes the speed of the motor l/ through the inverter 22 to change the pressure value in the opposite direction to the direction of change of the pressure value indicated by the pressure detector/B. The above control is performed so that the pressure indicated by the pressure detector 16 becomes the control target pressure SV determined above, and the rotational speed of the motor l/therefore the pump 12 and the pressure detector/6
The detected pressure of will change correspondingly.

FIG. 6 is a block diagram showing the control device.

The signal Sl of the pressure detector 16 and the frequency signal S2 of the inverter 22 are input to the microcomputer via the interface 2, and these values and the memory device 2A store the above-mentioned pressure-velocity at pump shut-off. Using data and formulas such as these, the frequency is calculated by the central processing unit S so that the control target pressure SV is achieved, and the frequency is outputted to the inverter 22 via the interface cock.
controls the rotational speed of the motor // to operate the pump 12 so that the control target pressure SV is achieved.

An actual example is shown in FIG. In Fig. 7, the horizontal axis shows the flow rate Q1 and the vertical axis shows the pressure P, with the car 4' for the maximum flow rate used as 2/cm2, the minimum pressure required when the pump is closed. ．．
The control target pressure calculated in step 6 is shown by a curve 23, and the terminal pressure Pn-PB is approximately constant.

FIG. 5 is a block diagram when a wired logic electronic circuit is used in the control unit 2/ of the rotation speed control means of the embodiment shown in FIG. A constant k obtained from the relationship between the values and the rotational speed of the pump in a state where the required maximum flow rate is supplied at the required pressure is input into the function generator 27, the adder, and the 2g1 pressure setting device. At 29, the control target pressure is calculated based on the input of the rotational speed and inputted to the controller 30.The controller 30 calculates, for example, the system pressure obtained from the pressure sensor 31 and the control target pressure, and calculates the control target pressure for the motor. This outputs a rotational speed operation signal.

As described above, the present invention provides a water supply device equipped with a pump in which a control target pressure is determined in advance for each rotational speed of the pump (or a function for calculating the control target pressure from the rotational speed is determined), and the control target pressure is adjusted as the rotational speed changes. Since it is equipped with a control device that changes the pressure, there is no energy loss as would be required if the pump discharge pressure is kept constant.

There is no need for a flow meter to control the discharge pressure at the end of the pipe, and there is no need for labor-intensive and time-consuming methods such as measuring and controlling each water supply equipment individually. can be kept almost constant.

The relationship between the predetermined pump rotation speed in the control target pressure output section and the control target pressure for each pump rotation speed is determined in each state when the pump is closed and when a predetermined flow rate is flowing through the system. Since it is set in a function or data table based on the pump rotation speed and discharge pressure value, the pump rotation speed and discharge are set when the pump is closed and when a predetermined flow rate is flowing, which can be selected as appropriate. If the pressure value is known, the pressure at the end of the water supply can be controlled to be constant at each rotational speed of the pump, so it is very flexible in inputting it to the rotational speed control means of the pump.

The method of determining the control target pressure based on the pump rotation speed uses a data table that stores the pressure values at each rotation speed when the pump is closed and data on the rotation speed and pressure value when the required pressure is being produced at the maximum water flow rate. Since the pump rotation speed-discharge pressure characteristic at the time of pump cut-off hardly changes depending on the pump, it should be stored in advance in the memory device of the microcomputer. It is suitable for mass-produced water supply equipment. The rotational speed when producing the required pressure at the maximum amount of water used can be obtained by calculating the pressure loss in the pipeline, or it can be easily obtained by actual measurement, and as a result, the rotational speed of each pump Since the control target pressure SV can be controlled based on the control target pressure SV, the control is extremely simple. Such control target pressure SV is expressed by equation (1)
When using equations (4) to (4), it can be determined by appropriately determining the constants α and β. In the embodiment shown in FIG. 5, the same effect as described above can be obtained.

[Brief explanation of the drawing]

Figures 1 and 1 are diagrams showing the conventional control method, Figure 3 is a diagram showing the characteristics of water supply equipment in three-dimensional coordinates, Figure 1 is a flow sheet of the water supply equipment used in the present invention, and Figure The figure is a flowchart of the present invention, Figure 6 is a block diagram of the present invention, and Figure 7 is a flowchart of the present invention.
The figure is a diagram showing an experimental example of the present invention, and FIG. 5 is a block diagram of an electronic circuit. l...Pump performance curve Co...PV curve 3...V-
4 curves l/...motor/, 2...pump 13...
Water source llI... Suction pipe /, 5-... Discharge pipe /A.
・Pressure detector /ri・・Check valve ig・・Gate valve /q・
・Water supply pipe 2/・Control unit 2.2・・Inverter 2
y...Interfunis, 25...Central processing unit
2 O...Memory 100,10/...Routine M...
Intersection of coordinates P, PX...Discharge pressure PA...Required pressure at maximum flow rate PB...Required closing pressure at setting Po...Pressure loss Pn...Required pressure at the end of the pipe △PX...Loss pressure in the pipe Q... Discharge amount (flow rate) Q...Flow rate S...
Characteristic surface S/...Pressure signal S2...Signal SV...
・Control target pressure V, Vx...Rotation speed ω-Rotation speed. Patent applicant Ebara Corporation Ebara Electric Co., Ltd. Agent Arai Part Figure 4 Figure 5 Figure 6 Power supply Figure 7 Flow rate o (', 41~

Claims (1)

[Claims] l A pump, a water supply pipe connected to the discharge side of the pump, a pressure detection means connected to the water supply pipe, a motor connected to the pump to drive it, and a rotation that controls the rotational speed of the pump. In a variable speed water supply device comprising a speed control means and a speed detection means for detecting the rotational speed of the pump, the rotational speed control means uses an output signal from the speed detection means as an input signal to control the rotation of the pump at a predetermined speed. a control target pressure output section that outputs a corresponding control target pressure based on the relationship between the speed and the control target pressure for each rotational speed of the pump; an output signal from the control target pressure output section and an output from the pressure detection means; A variable speed water supply device comprising: a rotational speed control section which takes the signal as an input signal and outputs a control number 48 for the rotational speed of the pump. (e) The relationship between the predetermined pump rotational speed in the control target pressure output section and the control target pressure for each pump rotational speed is the same when the pump is closed and when a predetermined flow rate is flowing through the system. 2. The variable speed water supply device according to claim 1, wherein the variable speed water supply device is set in the state of a function or data table based on the rotational speed and discharge pressure value of the pump in the state. 3. When the relationship between the predetermined rotational speed of the pump in the control target pressure output section and the control target pressure for each rotational speed of the pump is small, when the maximum flow rate required by the system is flowing through the system. and the state of the function or data table is set based on the rotational speed and discharge pressure value of the pump in each state when an arbitrary flow rate smaller than the maximum flow rate is flowed. variable water supply system. Hiroshi: The relationship between the predetermined pump rotational speed in the control target pressure output section and the control target pressure for each pump rotational speed changes in various ways when a predetermined flow rate is passed through the system and in the closed operation state. 2. The variable speed water supply device according to claim 1, wherein the variable speed water supply device is set in the state of a function or a data table based on each rotation speed and the corresponding discharge pressure value when the pump is rotationally driven at the rotation speed. S. The relationship between the predetermined pump rotational speed in the control target pressure output section and the control target pressure for each pump rotational speed is different from the predetermined flow rate when a predetermined flow rate is caused to flow through the system. Claims that are set in the state of a function or data table based on the rotational speed of the pump and the corresponding discharge pressure value when the pump is operated at various rotational speeds while maintaining an arbitrary constant flow rate. Variable speed water supply device according to item 1. The variable speed water supply device according to any one of claims 1 to 3, wherein the motor is a synchronous motor, and the rotational speed control means is based on an inverter control system. H) The speed detection means for detecting the rotational speed of the pump utilizes a frequency signal of the rotational speed control means using the inverter control system, and is substantially included in the rotational speed control means. Variable speed water supply device according to scope 6. & A pump, a water supply pipe connected to the discharge side of the pump, a pressure detection means connected to the water supply pipe, a motor connected to the pump to drive it, a rotation speed control means for controlling the rotation speed of the pump, and a pump. In the variable speed water supply device, the rotational speed control means uses an output signal from the speed detection means as an input signal to control the rotational speed of the pump at a predetermined rotational speed and the rotational speed of the pump. A control target pressure output unit that outputs a corresponding control target pressure based on the relationship with the control target pressure of the pump, an output signal from the control target pressure output unit, and an output signal from the pressure detection means as input signals, A resetting function having a function of correcting the relationship between a predetermined pump rotation speed and a control target pressure for each pump rotation speed in a rotation speed control section that outputs a rotation speed control signal and the control target pressure output section. A variable speed water supply device comprising: