JP2708826B2 - Water supply control device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a water supply system having an electric pump and a pressure tank, and more particularly to a system for controlling a water supply amount by controlling the number of operating pumps. It relates to a suitable water supply control device.

[Conventional technology]

In a water supply system with large fluctuations in water supply, in order to improve pump efficiency, a system in which a plurality of pumps with relatively small capacities are provided in parallel and the number of pumps operated is increased or decreased according to the water supply is often used. Used.

In such a water supply system and a water supply system of a pressure tank type, it is common to use a pressure switch, and to start / stop the electric pumps and control the number of operating units by turning on / off the pressure switch. .

By the way, this pressure switch, although depending on its type, usually has a differential pressure of 0.6 to
About 1.0 kg / cm ² is required.

Therefore, if a pump having a relatively flat QH characteristic is to be employed, the differential pressure required for the pressure switch cannot be sufficiently obtained, and it is difficult to set the operation.

In addition, if it is set forcibly, as a result, the amount of water when the pump stops is shifted to the high water amount side, so that the frequency of starting the pump is increased.

Therefore, in order to reduce the frequency of starting this pump,
The capacity of the pressure tank must be increased, which increases costs.

Therefore, Japanese Patent Publication No. 60-45759 discloses a technique in which a plurality of pressure switches are provided in correspondence with a plurality of electric pumps, and the start and stop of each pump are controlled by each pressure switch. However, this technique is unsatisfactory in that a large number of pressure switches are required and the control process becomes somewhat complicated.

Thus, if a pressure sensor for continuously detecting the feed water pressure is used, the above requirements can be sufficiently satisfied in terms of pump control. However, this pressure sensor is expensive and cannot avoid considerable cost increase. This is also unsuitable for relatively low-cost, conventional water supply systems.

Under such circumstances, the pump pressure is continuously detected by detecting the current of the electric motor that operates the pump without using the expensive pressure sensor described above, so that accurate control can be obtained at low cost. A method has been proposed.

[Problems to be Solved by the Invention] In the above-mentioned conventional technology, the pressure is detected by the electric current of the electric motor, and therefore, no consideration is given to the fact that it is susceptible to fluctuations in the power supply voltage. There was a problem with retention.

An object of the present invention is to eliminate the influence of fluctuations in power supply voltage when detecting pump pressure by electric current of a motor in a water supply system equipped with a plurality of pumps, and to always reliably control the number of operating pumps. Therefore, it is an object to provide a highly reliable pump control system at low cost.

[Means for solving the problem]

The above object is to use a pressure switch operating at the pressure of the pump, i.e., the pressure of the water supply system, to detect the current of the motor at the time of operation of the pressure switch. This is achieved by making a correction to the calculation of

According to the embodiment, the control is achieved by executing the following control by using a microcomputer (microcomputer) as a control system and making full use of electronics technology. That is, when one pump is operating and the power supply voltage is in a normal state, the operation of the pressure switch is monitored, and the current of the motor when the pressure switch is operated is measured. The value (referred to as a reference value Ik) is input to the microcomputer using a dip switch or the like and stored in a memory.

Similarly, as an initial value, the stop command current of the pump motor that is operating first is set by a dip switch, and the increase command current value and the decrease command current value for the remaining pump motors are set to the reference current value Ik. Based on, for example, 2
The second pump current command value is set in advance as Ik + a, and the second pump current command value is set as 2Ik + b (3,
4,..., Of course, the same setting is made for the second device).

For the first pump, a start command is generated when the pressure switch is turned on. When the pressure switch is in the on state, the current of the motor is measured, and the deviation between the detected value at this time and the reference value I is calculated. The above set value (initial value) is corrected by this deviation.

Thereby, it is possible to prevent the influence of the fluctuation of the power supply voltage.

According to an embodiment of the present invention, the failure of the pressure tank can be monitored when the stop time of the pump is shorter than a predetermined time set in advance.

[Action]

Since the pressure switch (which may be a flow rate switch) operates at a predetermined pressure, a change in the power supply voltage is compensated by giving a correction based on the current of the motor when the switch is operated, that is, the reference value I, and this power supply voltage is compensated. And accurate control can be performed without being affected by changes in

〔Example〕

Hereinafter, a water supply device according to the present invention will be described in detail with reference to the illustrated embodiments.

FIG. 2 shows an embodiment of the present invention, in which 1 is a water receiving tank, 2-1 and 2-2 are suction pipes, 3-1 and 3-2 are electric motors,
1,4-2 is a pump, 5-1 and 5-2 are gate valves, 6-1 and 6-2
Is a check valve, 7 is a pressure tank having an air reservoir inside,
8 is a pressure switch, 9 is a water supply pipe, 10 is a flow switch, 11
Is a control circuit.

In this embodiment, as apparent from this figure, two pumps 4-1 and 4-2 and two electric motors 3 for operating these pumps 4-1 and 4-2.
-1, 3-2, and the pressure switch 8 is turned on (contacts are closed) when the pressures of the pressure tank 7 and the water supply pipe 9 are equal to or higher than a predetermined pressure set in advance. When the pressure is lower than the pressure, the switch is turned off (the contact is opened). Note that the flow switch 10 is turned on when the amount of water passing through the water supply pipe 9 is equal to or more than a predetermined value. This also enables the same control as when pressure is detected, but here the pressure switch is used. 8 will mainly be described.

FIG. 3 shows the details of the control circuit 11, where PW is a power supply, MB is a wiring or breaker, CT is a current transformer for detecting a current flowing in the main circuit, and MC1 and MC2 are electromagnetic contacts. MC1a, MC2a
Are their contacts. 49-1 and 49-2 are motors 3-
Thermal relay to protect 1,3-2 from overload operation, R, S
Is a control power supply taken from the load side of the wiring and the breaker MB, SS is a switch for switching operation and stop, T is a DC power required to operate the control circuit 11 (for example, 5 volts, 12 volts) Is a stabilized power supply unit.

Next, Mcon is a microcomputer, a central processing unit CPU, and R
It comprises a memory M composed of AM, ROM, etc., a power supply connection terminal Z, and various input / output ports Pio-1, Pio-2, Pio-3.

I / O-1, I / O-2 and I / O-3 are interfaces, Dip-
1, Dip-2 is a date switch, Ps is a pressure switch 8
(Or the flow switch 10).

The interface I / O-1 includes the currents of the motors 3-1 and 3-2 detected by the current transformer CT and the dip switches Dip-1 and Dip-
The microcomputer Mcon compares the pump stop command current value Ioff and the reference current value Ik set in advance with the input / output port Pio-
Interface for reading via I / O, I / O
-2 functions as an interface for reading the signal of the contact point Ps from the input / output port Pio-2, and the interface I / O-3 connects the electromagnetic contactors MC1 and MC2 via the input / output port Pio-3. An interface for controlling.

The present invention is not limited to the above embodiment, and the control circuit 11 may be configured by a one-chip microcomputer.

 Next, the operation of this embodiment will be described.

FIG. 4 is a pump operation characteristic diagram of the water supply system.
In the figure, a curve A represents the QH characteristic when only one of the pumps 4-1 and 4-2 is operated, and a curve B represents the two pumps 4-1 and 4-2.
4-2 shows QH characteristics when operated in parallel.

Next, a curve C is a load characteristic of the motor when only one pump is operated, that is, a current characteristic. Similarly, a curve D is a current characteristic of the motor when two pumps are operated in parallel.

In this characteristic diagram, the pressure at P ₁ is to start the pump, so-called starting pressure, Q ₁ represents the amount of water supplied in the starting pressure P _1.

Here, the pressure switch 8 closes the contact with the pressure P _1, is set to open the contacts at a pressure P ₁ '(this is called the return pressure). Then, the differential pressure ΔP at this time =
The (P ₁ '-P _1), is commonly 0.2~0.4Kgf / cm ² is selected.

Next, in the figure, I _OFF means that only one pump is operated, and at this time, the voltage and the current are at predetermined values, and at this time, the stop-time water amount Q ₂ which is considered to be optimal for stopping the pump. Is a stop command current value set based on the reference value, and this current value is set in advance by the dip switch Dip-1. Incidentally, P ₂ is the pressure at this time.

Further, I _TON is a start command current of the pump that is operated to follow up, and I _TOFF is a stop instruction current of the pump that is also operated to follow up.

By the way, the fluctuation of the power supply voltage in the power system is suppressed to approximately ± 10% at the power supply source.

On the other hand, as an electric motor for pump operation, an induction motor is usually used. In this induction motor, when the power supply voltage fluctuates, the driving current naturally increases under the same torque, The size is the above 10%
Is about 8%.

Therefore, if the feedwater pressure is simply obtained from the electric current of the electric motor, accurate control cannot be maintained when the power supply voltage fluctuates.

Here, returning to FIG. 4, curves C 'and C "in the figure are drive current characteristics when one motor is operated when the power supply voltage fluctuates by -10% and + 10%, respectively. D ″ is a drive current characteristic when two motors are operated. From these, it can be seen that the current of the motor increases when the power supply voltage decreases, and conversely, the current decreases when the power supply voltage increases.

Next, in this figure, as described above, Ik is the current of the motor when the power supply voltage is in a normal state, that is, the reference value, and this value is the value of the dip switch Dip-2.
Is set in advance. That is, the drive current of the electric motors 3-1 and 3-2 when the power supply voltage is in the normal state is measured under the condition that the pressure switch 8 is further turned on, and the measured value is used as a reference value Ik for the dip switch Dip. It is input by -2.

Further, in FIG, m ₁ is the case where the voltage with respect to the reference current value Ik fluctuates -10%, and m ₂ is also voltage + 10%
FIG. 5 shows a change in current per motor when the electric power fluctuates, and details thereof are shown in FIG. As is apparent from FIG. 5, the pressure difference ΔP between ON and OFF of the pressure switch 8 is
As described above, the current change Δn corresponding to the flow rate change ΔQ at this time becomes extremely small as the value (typically selected from 0.2 to 0.4 kgf / cm ² ) is reduced. What is necessary is just to set it so that it may fall during this electric current change (DELTA) n.

On the other hand, as the above-mentioned starting current command value I _TON , a pressure P _{3 which} is slightly lower than the pump starting pressure P ₁ (the water amount at this time is Q ₃
Corresponding to become) a, a only a current value greater than the reference value Ik is set to (Ik + a), as a further stop current command value I _TOFF, a pressure higher than the return pressure P ₁ 'to turn on the pressure switch 8 The current value (2Ik−b) is set smaller than the reference current value 2Ik corresponding to P ₄ (the water amount at this time is Q ₄ ) by b.

As described above, in this embodiment, when the pressure switch 8 is closed, the drive current I of the electric motors 3-1 and 3-2 is measured.
This is compared with the reference current value Ik, and the current command values I _OFF , I _TON , and I _TOFF are corrected by these deviations, and the corrected values are set. Therefore, accurate pump control can always be performed.

Incidentally, the above operation processing is mainly performed by the microcomputer Mcon in the control circuit 11. Therefore, the control operation procedure by the microcomputer Mcon will be described below with reference to FIGS.
This will be described in detail with reference to the flowcharts of FIGS.
Here, FIG. 1 shows the entire processing, and FIGS.
It shows the details of the processing steps in the figure.

First, the wiring gutter and the breaker MB in FIG.
When the switch SS is closed, the power supply terminal Z of the microcomputer Mcon
Is supplied with power for operation, and the operation is started.

As a result, first, the microcomputer Mcon executes the initial setting of step 401 in FIG. Next, step 402 is executed.
FIG. 6 shows the details of this step 401. In step 501, the signal of the contact point PS of the pressure switch 8 is read through the interface I / O-2 and the input / output port Pio-2, and the ON / OFF judgment is executed. The result is stored, for example, at address 8000 of the memory RAM. At step 502, the reference current value Ik set in the DIP switch Dip-2 is read via the interface I / O-1 and the input / output port Pio-1, and this data is stored, for example, at address 8001 of the memory RAM. In 503 steps,
Based on this reference current value Ik, a start command current I _TON of the pump to be followed is calculated by calculating Ik + a, and stored as an initial value at address 8002 of the memory. Similarly, in the 504 step determined by calculating the stop command current value I _OFF of the follow-up pump and 2Ik-b, stored as an initial value to 8003 address the memory. Next, 505 in the stop command current value I _OFF prior pumps that are set in Deitsupusuitsuchi Dip-1 in step Tough Ace I / O-1, reads through the input-output port Pio-1, the initial value of the data And store it at address 8004 in the memory. In this embodiment, the stop command current value is set by the dip switch Dip-1.
Instead of this, it may be written in advance in the memory ROM as data.

After executing these processes, the process returns to step 403 in FIG. 1, and it is determined whether the feed water pressure has reached the starting pressure or less. If the result of the determination is that the starting pressure is ₁ or less,
Proceeding to the next step 407, a signal for starting the pump to be operated first is output from the input / output port Pio-3 via the interface I / O-3, and the electromagnetic switch is operated.
Energize MC1 or MC2.

Now, assuming that the preceding pump is MC1, the electric motor 3-1 is driven and the pump 4-1 is operated. If the result of the determination in step 403 is equal to or higher than the starting pressure, the processing in steps 404 to 406 is executed until the processing becomes equal to or lower than the starting pressure. In addition, as will be described later, the measurement and stop time of the stop time of the preceding pump are described.
of the determination whether t ₂ below, executes the process of reporting an abnormality of the tank accordingly, returns to 402 step.

Here, the relationship between water amount Q ₂ when the pump stop time t ₂ and the pump stopped holdings water V in the pressure tank is given by When (pump ON, water volume between _{OFF) t 2 = V / Q} 2.

For example, when the water volume V of the tank is 7, the water volume at the time of stoppage Q ₂
Is 10 / min and the pump stop time t ₂ is calculated as Becomes Therefore, in this example, the pump stop time t ₂ is determined as t ₂ = about 10 seconds as a result of executing the above-described processing.
If the time is shorter than 10 seconds, some trouble has occurred on the pressure tank side. It should be noted that this is due to a decrease in the internal air of the diaphragm type pressure tank or the tank with the automatic air supply device, and ultimately a malfunction of the pressure tank.

Accordingly, by providing an alarm lamp or the like in the control circuit 11 of FIG. 3 in addition to the processing of step 406, it is possible to report an abnormality of the tank.

Next, at step 408 (details are shown in FIG. 7), current detection and current correction are performed. That is, in FIG. 7, the load current of the motors 3-1 and 3-2 is detected by the current transformer CT at step 601 as shown in FIG. 3, and this value is used as the interface I / O- 1 is read from the input / output port Pio-1 and stored in, for example, address 8005 of the memory RAM. Next, the process proceeds to step 602, where it is determined whether or not the contact Ps of the pressure switch 8 is closed. If not, the process exits this loop. That is, when the pressure switch 8 is closed, each set current described above is corrected. 60
The current I measured in three steps is compared with the reference current Ik. However, as a result of the comparison, if the values are equal, the set value is not corrected, and the initial value set in the processing of FIG. 6 is left. As a result of the comparison, if Ik> I, the process proceeds to step 604. Here, the change ΔI (Ik−I ≧ m1) of the current due to the power supply fluctuation is obtained, and the stop command current value I _OFF of the preceding pump is obtained in step 605.
Is corrected by the current change ΔI to obtain I _OFF + ΔI, which is set as a new set value and stored at the address 8004. Similarly, 60
In step 6,607, the current change ΔI is corrected, the follow-up pump start command current value I _{TON is set} to (I _TON + ΔI), and this is stored at address 8002 as a new set value. Similarly,
The follow-up pump stop command current value I _{TOFF is set} to (I _TOFF + 2ΔI), and this is stored at address 8003 as a new value. If the result of the comparison at step 603 is Ik <I, the processing of steps 608 to 611 is executed, and here, the operation processing opposite to that of steps 604 to 607 is executed. Although omitted, each setting data is updated.

When these processes are executed, the process returns to step 409 in FIG. 1. Further, here, the actually measured current I and the preceding pump stop command current value I _OFF (of course, if the power supply voltage fluctuates, This value _ITOFF has been corrected). As a result of comparison, if I> I _OFF
The process proceeds to step 411, but if I <I _OFF , the process proceeds to step 410 to execute stop processing.

When the determination result at step 409 is NO, the process proceeds to the next step 411, where it is compared whether the load current I has reached the starting command (increased) current I _TON of the following pump. here,
As described above, the value of I _TON is corrected for the current change due to the fluctuation of the power supply voltage. As a result of comparison, if I <I _TON , the process returns to step 408, and the subsequent processing is performed.
If it is _TON , this state will be kept for a certain time (5-10
After confirming that the time has elapsed, a process for starting the follow-up pump (either 4-1 or 4-2) is executed at step 415. Incidentally, as another embodiment of the starting condition of the following pump,
If the contact of the pressure switch PS shown in steps 413 to 414 is confirmed to be closed for a certain period of time or more before executing steps 411 to 412 and the start-up processing of the follow-up pump is executed, the operation is further ensured. Thereafter, the process proceeds to step 415, where the same current detection and correction processing of each set value as in step 408 described above are performed. In step 417, the actual load current I is compared with the stop command current _ITOFF of the follow-up pump, and as a result of comparison, if I> _ITOFF , the process returns to step 416, and the subsequent processing is executed. On the other hand, if I> I _TOFF , the process proceeds to step 418, in which the following pump is stopped, and
Return to step 8.

Hereinafter, the control operation is repeated according to the above-described procedure,
The number of pumps operated is controlled according to the demand water amount, and the water supply operation is continued.

Therefore, according to these embodiments, even if the power supply voltage fluctuates, it is possible to appropriately correct various current command values in accordance therewith, and to control the start and stop of the pump and the increase and decrease of the number of pumps. Can always be performed reliably.

In addition, if the cycle time of the pump can be set arbitrarily from the outside, the starting command pressure of the preceding pump and the starting and stopping command current values of the following pump can be optimized (wrapped). Even if the operation is performed with the water supply amount near the switching point, it is possible to prevent the control state where only the following pump (specific pump) is turned on / off.

Further, in the above embodiment, since the initial value of each set value is input by the dip switch, there is an effect that even when the power is turned off, the data does not disappear and the operation can be continued as it is.

〔The invention's effect〕

ADVANTAGE OF THE INVENTION According to this invention, in the water supply system of the system which detects the electric current of the electric motor which drives a pump, and controls the number of pumps operated, it can eliminate the possibility of control loss by fluctuation | variation of a power supply voltage. Even if a pump having the -H characteristic is used, the problem of difficulty in setting the pressure switch is eliminated, and the operation control of the pump in such a water supply system can always be accurately performed.

[Brief description of the drawings]

FIG. 1 is a flowchart for explaining the operation of an embodiment of a water supply control device according to the present invention, FIG. 2 is a system configuration diagram showing an embodiment of the present invention, and FIG. 4 and 5 are characteristic diagrams for explaining the operation of one embodiment of the present invention, and FIGS. 6 and 7 are flow charts for explaining the operation. 3-1, 3-2 ... motor, 4-1 4-2 ... pump, 7 ...
... pressure tank, 8 ... pressure switch, 10 ... flow switch, CT ... current transformer, MC1, MC2 ... ... magnetic electromagnetic contactor, M _con ... microcomputer, _Pio- 1,
P _io- 2, P _io- 3 ... I / O ports, I / O-1, I / O-2, I / O
-3 ...... Inn tough _{Ace, D ip -1, D ip -2} ...... Deitsupusuitsuchi, T ...... stabilized power Yunitsuto.

Claims (5)

(57) [Claims] An electric pump comprising at least two electric pumps and a pressure tank connected to a discharge side thereof, wherein starting control of the first one from a state in which all of the electric pumps are stopped is controlled by a water supply amount. Is performed when the flow rate reaches a predetermined flow rate value, and the increase / decrease control of the number of operating pumps and the stop control of the last pump are performed when the current consumption of the electric motor for driving the electric pump reaches a predetermined current set value. Data input means for presetting the consumed current value at the predetermined flow rate value as an initial value, and sequentially detecting the consumed current value at the predetermined flow rate value during operation of the pump to thereby determine a deviation from the initial value. And processing means for correcting the respective current set values required for the increase / decrease control and the stop control based on the detection result of the deviation. Water supply control apparatus characterized by operation control of the pump is constructed as Yuku been performed by flow setpoint. 2. The invention according to claim 1, wherein the predetermined flow rate value is detected by at least one of a flow rate switch and a pressure switch installed in the water supply pipe. Water supply control device. 3. The water supply control device according to claim 1, wherein an initial value of each current set value required for the increase / decrease control and the stop control is preset input. 4. The invention according to claim 1, wherein in the increase / decrease control of the number of operating pumps, the condition for increasing the number of operating pumps is not limited to the current set value, but the current set value state A water supply control device characterized in that it is configured to have a condition that it has continued for a predetermined time or more set in advance. 5. The invention according to claim 1, further comprising a determination means for measuring a time during which all of the electric pumps are stopped,
A water supply control device characterized in that when the result of the determination by the determination means exceeds a predetermined set time, the occurrence of an abnormality in the pressure tank is displayed.