JPH0510518B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a device for operating and controlling a pump device driven by a variable speed motor, and in particular to a device for operating and controlling a pump device driven by a variable speed motor, and in particular, by using an inverter device controlled by a microcomputer to operate and control a pump device driven by a variable speed motor. The present invention relates to a water supply device suitable for controlling the discharge pressure to a constant level by directly controlling the speed of the pump.

[Conventional technology]

Conventionally, by installing a pressure sensor in the water supply pipe of a pump device driven by a variable speed motor, measuring the discharge pressure, and constantly comparing both pressures to maintain the discharge pressure at the target discharge pressure, There is a method of continuously variable operation of the pump based on a control signal whose magnitude corresponds to the deviation. This method will now be explained using FIGS. 1-3.

Figure 1 is a configuration diagram of the pump device, where 1 is a water tank, 2
1 is a suction pipe, 3 and 6 are gate valves, 4 is a pump, 5 is a check valve, 7 is a water supply pipe, 8 is a pressure sensor provided in the water supply pipe, and 9 is a variable speed motor. Pressure sensor 8
The system detects the pressure of the fluid flowing through the water supply pipe and generates a direct current electrical signal (current or voltage) in response to this. FIG. 2 is an operational characteristic diagram when the pump 4 of the pump device is operated at variable speed, with the horizontal axis representing the water amount Q and the vertical axis representing the pressure H. Curve a shows the Q-H performance when the pump 4 is operating at the maximum rotational speed (100%), and similarly, curve e shows the Q-H performance when the pump rotational speed is operating at the minimum rotational speed. Shows Q-H performance. The rotational speed of the pump is continuously variable, but for convenience, the Q-H performance of the pump at any intermediate rotational speed is shown by curves b, c, and d.

FIG. 3 is a block diagram showing the control flow of the control device for variable speed operation of the pump device, in which the proportional-integral circuit PID includes an error amplifier OP, a proportional circuit P,
It consists of an integrator I and an adder A. CTL indicates a control device for operating the variable speed motor 9 at variable speeds,
FIG. 4 shows a time chart of the proportional-integral circuit PID. In Figures 1 to 4, the amount of water used is now Q ₀
Assume that the pump 4 is operating at a rotational speed N ₂ at a point O ₁ on the pump performance curve c. In this state, if the amount of water used changes and decreases to Q ₃ , the operating point will be
The water moves to _O2 , and the pressure inside the water supply pipe 7 rises to _H1 .
At this time, the pressure sensor 8 detects this pressure and generates an electrical signal (direct current or voltage) corresponding to this pressure. _{The deviation} ES ( _{E 0}
-E ₁ ) by the error amplification circuit OP, and apply the amplified signals to a proportional circuit P and an integral circuit I, respectively.
The output signals EP and EI of the proportional circuit P and the integral circuit I are added by an adder A, and this signal EP+EI is outputted to the control device CTL of the variable speed motor 9 as a control signal.

That is, as shown in Fig. 4, the electric signal E ₁ emitted from the pressure sensor is larger than the electric signal E ₀ which is the target value corresponding to the target pressure H ₀ , and the deviation between the two is
ES=(E ₀ −E ₁ ) is negative. For this reason, the control signal
As EP+EI becomes smaller, the speed of the pump 4 and variable speed motor 9 decreases, and when the deviation ES=(E ₀ - E ₁ ) becomes 0, the control signal EP+EI becomes stable and the pump is operated at a speed according to that signal. .

As a result, as shown in Fig. 2, the variable speed motor 9 and the pump 4 are decelerated to the rotational speed _N4 , the pump performance curve becomes f, and the pump operating point changes from _{O2 to}
Move to O ₃ and keep target pressure H ₀ constant.

Also, when the amount of water used increases and reaches _Q4 , the operating point moves to _O4 and the pressure in the water supply pipe 7 decreases to _H2 , as described above. At this time, pressure sensor 8
detects this pressure, issues an electric signal E ₁ , and changes the speed of the variable speed motor 9 so that the deviation ES (E ₀ −E ₁ ) from the target value becomes zero. In this case, the deviation ES is positive, so the speed is increased and the rotational speed becomes _N5 , and the pump performance curve becomes G. This moves the pump operating point from O ₄ to O ₅ and keeps the target pressure constant at H ₀ .

[Problem to be solved by the invention]

The above-mentioned conventional device had the following problems.

(1) A proportional-integral circuit is used to prevent the rotational speed of the variable speed motor and pump from falling below the minimum rotational speed or from running out of control above the maximum speed, or to reduce the offset of automatic control.
PID was needed.

(2) This proportional-integral circuit PID is analog controlled, and there are many adjustment parts such as target value setting and proportional-integral time setting, which may cause a delay with respect to the target value.

(3) This PID is economically expensive and difficult to apply for other purposes. For example, if you want to use a data logger to measure the amount of water used each day, you will need a computer in addition to a flow meter. Having a computer perform only this data logging is uneconomical as it reduces cost performance.

In addition, in recent years, digitalization of control has progressed, and it is being considered to replace the conventional analog configuration with a digital configuration. According to this, the control steps (conventional PID circuit ) is required. In order to realize this control step, it is necessary to calculate a mathematical formula stored in advance or to follow a predetermined control pattern in accordance with the control process.

However, this requires software development tailored to the pump's discharge characteristics and piping characteristics, or an increase in memory capacity, which is extremely disadvantageous especially when applied to low-priced products.

The present invention has been made in view of the above points, and its purpose is to prevent the occurrence of water hammer or chattering without requiring a proportional-integral circuit or special means equivalent thereto. To provide a water supply device at a low cost that can prevent the above problems and keep the discharge pressure almost constant.

[Means to solve the problem]

In order to achieve the above object, the present invention is characterized by a pump, a variable speed electric motor that drives the pump, an inverter device that controls the speed of the variable speed electric motor, and a water supply pipe connected to the pump. The inverter device includes a pressure sensor that detects the pressure in the road, a microcomputer, and a memory that stores a speed change control width of the variable speed motor, and the inverter device is configured to match the pressure measured by the pressure sensor with a predetermined target pressure. and a motion control device that gives speed commands that are sequentially increased or decreased by the speed change control width. If the two pressures do not match, the operation control device issues a speed command to the inverter device at predetermined time intervals at which pressure fluctuations in the water supply pipe due to increases and decreases in the speed change control width are stabilized. It increases or decreases with the speed change control width.

[Effect]

With the above configuration, even if the deviation between the pressure measured in the water supply pipe by the pressure sensor and the predetermined target pressure becomes large for some reason, the inverter device will not receive a speed command that changes greatly at once. Instead, speed commands in which the predetermined speed change control width is sequentially increased or decreased are sequentially applied. In addition, this speed command is increased or decreased sequentially at predetermined time intervals when pressure fluctuations in the water supply pipes are stabilized due to increases or decreases in the speed change control width, so pressure fluctuations in the water supply pipes are always suppressed. The pump is accelerated or decelerated.

Therefore, we have developed a water supply system that can prevent the occurrence of water hammer or chattering and maintain the discharge pressure almost constant without requiring a proportional-integral circuit or any special means equivalent to this. It can be obtained cheaply.

〔Example〕

An embodiment of the present invention shown in the drawings will be described below.

In this embodiment, the rotation speed of the pump is changed in stages according to the amount of water used, and the discharge pressure of the pump is kept almost constant. The electrical signal corresponding to the detection is extracted, this signal is amplified and sent to the input terminal of the comparator, and the microcomputer sends arbitrary data via the D/A converter to the other comparator. Output to the input terminal, increment or decrement the data of the microcomputer until the output of the comparator goes from 0 to 1, store the data as a detection signal of the pressure sensor, and set any rotation speed as the initial rotation speed. In addition to storing the data of the variable speed motor and the data of the speed change width, the output device of the microcomputer converts the data of the initial rotation speed into a control signal which is an analog quantity via a D/A converter, and outputs the data to the control device of the variable speed motor. After outputting data to and operating at the initial speed, compare the target pressure data described above with the detection data of the pressure sensor, and if the target pressure data is larger, change the speed change width data from the initial rotation speed data. If the target pressure data is smaller, the shift width data is subtracted from the initial rotation speed data, and the result is output from the output device to the control device of the variable speed motor via the D/A converter. The system also includes an operation control device that stores the data as new rotational speed data and repeats the above-mentioned process until the target pressure data matches the pressure sensor detection data to obtain the target rotational speed.

FIG. 5 shows a control circuit of an operation control device according to an embodiment of the present invention, where MCB is a main circuit disconnector, MC
is the magnetic contactor coil, Mca is its contact, INV
is a variable frequency inverter device for changing the rotational speed of the variable speed motor 9, 49 is a thermal relay for overload prevention, and μcon is a central processing unit CPU
(hereinafter abbreviated as CPU), memory M, power supply terminal E, input device IND, output device OUTA, OUTB, OUTC
A microcomputer consisting of F ₁ ,
_F2 is a D/A converter that converts a digital signal such as a hexadecimal number into an analog signal, OP is an operational amplifier, CP is a comparator, and _R1 to _R6 are resistors.

Microcomputer μcon output device
The OUTC port is connected to the + input terminal of the comparator CP via the D/A converter _F1 , and 8-bit data is output from the output device OUTC port.
This 8-bit data is converted into an analog quantity by the D/A converter _F1 . Also, the output of the comparator CP is the input device of the microcomputer μcon.
It is connected to output to the lowest bit b ₀ (any bit is fine) of the IND port, and
Microcomputer μcon output device OUTB
The port is connected to send a speed change command signal to the variable frequency inverter INV via the D/A converter _F2 .

The control circuit CTL consists of a transformer T, a power supply unit Z,
Consists of start/stop switch SS, magnetic contactor MC, transistor Tr, and relay X. Control device CTL
When the circuit breaker MCB is turned on and the start/stop switch SS is closed, rectified and smoothed stable power is sent from the power supply unit Z via the transformer T to the power supply terminal E of the microcomputer μcon, which starts operation. Preparation is complete.

Next, the relationship between the electrical signals emitted from the pressure sensor 8 will be explained. Now the pressure sensor is water supply pipe 7
When the internal pressure is P, an electric signal I is emitted, the input voltage of the operational amplifier OP is Vi, and the output voltage is
Assuming V ₀ , the output voltage is given by equation (1).

V ₀ = (1+R ₃ /R ₂ )Vi...(1) By the way, when the input voltage Vi of the operational amplifier is expressed by the electrical signal I generated by the pressure sensor 8, it is expressed as Vi=I・R ₁ ...(2) . Here, R ₁ is the input resistance of the operational amplifier OP.

By transforming equations (1) and (2), we obtain the following equation (3).

V ₀ = (1+R ₃ /R ₂ )・I・R ₁ ...(3) Here, the resistors R ₂ and R ₃ can be carried appropriately, but if we set R ₂ = R ₃ for convenience, equation (3) becomes V ₀ =2・I・R ₁ ...(4).

Generally, the electrical signal emitted by a pressure sensor is on the order of mA, so in equation (4), R ₁ is set for convenience.
If you choose 1KΩ (R ₁ can also be selected appropriately)
Equation (4) further becomes V ₀ =2·I (5).

In other words, equation (5) shows that the output voltage of the operational amplifier OP is proportional to twice the electrical signal generated by the pressure sensor. In other words, the pressure inside the water supply pipe P
and the output voltage V ₀ of the operational amplifier have a one-to-one correspondence.

6 and 7 are flowcharts showing the control procedure of the operation control device.

FIG. 8 shows the relationship between the pressure detected by the pressure sensor 8 and the electrical signal output from the sensor.

Further, FIGS. 9 and 10 show the process until the target rotational speed and target pressure are reached, respectively.

To explain in more detail with these drawings,
A program is stored in the memory M of the microcomputer μcon so that the pump device can be operated according to the flowcharts shown in FIGS. 6 and 7. First, in 3 steps, the CPU
For example, data on the target rotation speed (data obtained by converting the electric signal _I0 shown in FIG. 8 into hexadecimal, etc.) is loaded into the BC register. Next, in 4 steps, data 01 (hexadecimal number) is stored in the A register of the CPU.
Load A, and in 5 steps, connect A from the output device OUTA port of the microcomputer μcon.
Output the data 01(16) loaded into the register. This output state is the control circuit CTL in Figure 5.
Shown in OUTA.

In other words, since only the lowest bit _b0 of port OUTA is 1, the transistor Tr is conductive.
Since relay X is energized, electromagnetic contactor MC is energized and its contact point Mca is closed.

Next, in 6 steps, the initial rotation speed data is loaded into the A register, and in 7 steps, the output device is loaded.
The data in the A register is output from the OUTB port via the D/A converter _F1 to the variable speed frequency inverter device INV, which is a control device for the variable speed motor. Therefore, the variable speed motor starts operating at the initial speed. Note that this speed can be arbitrarily determined. Further, this initial rotation speed data is stored in the memory _M1 in 8 steps.

Furthermore, in the 9th step, data of the conversion control width (data corresponding to triangle N shown in Figs. 9 and 10) is loaded into the A register, and in the 10th step, the data loaded into the A register is stored in the memory _M2. put.

Similarly, in steps 11, 12, 13, and 14, data corresponding to the minimum rotational speed NMIN is stored in memory _M3 .
Store data corresponding to the maximum rotational speed NMAX in memory _M4 .

I will continue to explain further, but now, variable speed motor 9
and the rotational speed of the pump 4 is N ₂ as shown in FIG.
Assume that the system is operating at pressure H ₀ and point O ₀ on characteristic curve c. Under these conditions, the amount of water used decreases.
At Q ₄ , the pressure increases. The pressure increases and the operating point moves from O ₀ to O ₁ , and the pressure in the water supply pipe 7 decreases.
When H ₁ is reached, the pressure sensor 8 detects this and
Emit an electrical signal I ₁ .

As a result, the output voltage of the operational amplifier OP becomes 2I ₁ =V ₁ from equation (5). This signal _V1 is sent to the (-) input terminal of comparator CP. Next, the microcomputer μcon executes the processing from step 15 onward. That is, data 00(16) (or FF(16) or other data may be used) is loaded into the DE register of the CPU, and the data in the DE register is output from the port of the output device OUTC.
Here, the digital signal output from the output device OUTC port is converted to an analog signal by the D/A converter _F1 , and the resulting signal (initial value is 00 in this example)
(16)) to the positive input of comparator CP.
This comparator CP inverts its output signal from 0 to 1 when the positive input signal is equal to or larger than the negative input signal.

Therefore, as a result, the least significant bit _b0 of the port of the input device IND of the microcomputer becomes 0.

Next, the microcomputer μcon inputs port data 00 (16) of the input device IND in 17 steps, reads it into the A register, and in 18 steps it inputs the data 00 (16) of the port of the input device IND.
Executes judgment to determine whether the data imported into the register is 01 (16), and if the judgment result is 01 (16), jumps to step 20, and if it is 00 (16), proceeds to step 19, and stores it in the DE register. Increment (or decrement) the data in the DE register, jump to step 17, repeat the loop of steps 17, 18, and 19 until the A register becomes 01 (16), and sequentially increment the data in the DE register (first If FF(16) is loaded into the DE register, it is decremented).

As a result, if the data in the A register becomes 01 (16), the data in the DE register is shifted to the right in 20 steps to reduce the data to 1/2. This is because the above-mentioned equation (5) is twice the signal emitted by the pressure sensor, so it is necessary to match the level with the target value. Instead of halving, you can double the target value and match it.

Then, in step 21, the data in the DE register (detected value of the pressure sensor) is subtracted from the data in the BC register (target pressure value), and the result is stored in the A register.

The data stored in this A register is digital data corresponding to the deviation H ₀ −H ₁ between the target pressure H ₀ and the measured pressure H ₁ of the pressure sensor.

Next, in step 22, determine whether the data stored in the A register is 00(16), and if it is 00(16), the target pressure and measured pressure match, so
Jump to step 34, wait for a certain period of time, and proceed to step 35. If it is not 00(16), it is determined in the next 23 steps whether the data in the A register is positive. In the example in Figure 9,
Since H ₀ - H ₁ is negative, the result is a jump to 24 steps, the initial rotation speed data in memory M ₁ is transferred to the A register, and in 26 steps A
Compare the data in the register and the data in memory _M3 (minimum rotation speed data) and check if they are equal.
If it is smaller, jump to step 34 without changing gears, wait for a certain period of time, and proceed with the process.
Otherwise, transfer the rotation speed data of _M1 to the A register in 27 steps.

This continues to decelerate, and as the speed decreases, the Q-H curve of the pump also decreases, causing the inconvenience that the pump cut-off pressure PS drops below the target pressure H ₀ and control runaway. This is to ensure that the rotational speed does not drop below NMIN.

Then, in step 28, the data in memory _M2 containing the shift control width ΔN is subtracted from the data in register A, and stored in register A, and in step 32, the data in register A is stored in memory _M1 as new rotational speed data. Transfer it to and store it. Next, in 33 steps, the data in the A register is output from the port of the output device OUTB, and the data is converted into an analog quantity by the D/A converter _F2 , and is sent as a control signal to the variable speed motor control device. Send to frequency inverter device INV.
As a result, the rotational speeds of the variable speed motor 9 and the pump 4 are reduced by ΔN from _N2 .
Therefore, the operating point of the pump 4 moves from O ₁ to O ₂ ,
The pressure inside the water supply pipe 7 becomes _H2 . However, since the target pressure H ₀ has not been reached, the microcomputer μcon proceeds with the process further, executing a waiting period of a certain time in 34 steps, and starting and starting in 35 steps.
It is determined whether the stop switch SS is closed, and if it is closed, the operation is stopped, but since the result of the determination is that it is closed, the microcomputer μcon executes steps 15 and onwards again. As a result, the rotational speed of the variable speed motor is further increased by △N
, the operating point of the pump 4 moves from O ₂ to O ₃ , and the pressure inside the water supply pipe becomes H _2. Eventually, the judgment result of the 22 steps described above becomes 00 (16).
The speed is reduced by N, and as a result, the rotational speed is N ₄
Thus, the target pressure H ₀ is kept constant.

In addition, the amount of water used increased, as shown in Figure 10.
When Q ₄ ' is reached, the microcomputer μcon continues processing as described above, but in this case, since the judgment result at step 23 is positive, it jumps to step 25 and changes the initial rotation speed. Data is transferred from memory _M1 to A register, and the data in A register and memory are transferred in the next 29 steps.
Compare the data of _M1 (maximum rotation speed data), and if it is equal or larger, jump to 34 steps without changing gears and wait for a certain period of time to proceed with the process, otherwise
Transfer the rotation speed data of _M1 to the A register. This is to prevent the rotation speed from increasing too much if the speed continues to increase, and the pump's Q-H curve also becoming large, which would not only result in overload operation but also to prevent adverse effects on the control device of the variable speed motor. be. For this reason, the rotational speed of the variable speed motor and pump is kept below NMAX.

Then, in 31 steps, the memory containing the data of the A register and the data of the shift control width △N is
Add M ₂ and store the result in the A register. In 32 steps, the data in the A register is transferred to the memory _M1 as new rotational speed data. Then, in 33 steps, the data in the A register is sent to the D/A converter from the output device OUTB port.
The output is output to the variable frequency inverter device INV via F ₂ , and the rotational speed of the variable speed motor 9 and pump 4 is increased by △N from N ₂ until the judgment result of 22 steps becomes 00 (16). speed up.

As a result, the operating point of pump 4 is O ₀ →O ₁ ′→
The pressure changes from O ₂ ′→O ₃ ′→O ₄ ′, and the target pressure H ₀ is kept constant. 9 and 10 show pressure changes in a large scale to make the explanation easier to understand, but in reality, the changes are extremely small.

Furthermore, the shift control width ΔN can be appropriately determined based on the offset with respect to the target pressure H ₀ and the time required to reach the target pressure H ₀ , and the waiting time t
can be appropriately determined depending on the time required to reach the target pressure. Also, while the CPU of the microcomputer μcon is executing the waiting time, a flowmeter is provided in the water supply pipe, although not shown in this embodiment, and the signal of this flowmeter is read into the microcomputer μcon. It is also possible to log data such as daily or monthly water consumption and power consumption. Furthermore, since these data are in digital quantities, they can be easily transmitted to a remote monitoring room or the like.

Although FIGS. 6 and 7 of this embodiment show an example in which an 8080 or equivalent microcomputer is used as the instruction system, the present invention is not limited to this.

As described above, according to this embodiment, the proportional-integral circuit PID for the speed command of the variable speed motor is no longer required.
Not only is it economically inexpensive, but the speed change control width is △
By appropriately determining N and waiting time t, the offset with respect to the target pressure can be reduced and responsiveness can be improved.

That is, if the speed change control width ΔN is selected to be small, the operating speed of the variable speed pump can be varied almost continuously.

In addition, since the speed of the variable speed motor is changed using an inverter device to control the characteristics of the pump,
During speed control, the rotational energy of the variable speed motor is directly transmitted to the pump, so no energy is wasted, and energy can be saved.

Furthermore, since the microcomputer can be used for multiple purposes, cost performance is improved. In addition, to prevent runaway, the minimum rotation speed N
Since a MIN and a maximum rotational speed NMAX are set and the operation is set between these values, no pressure drop occurs, pressure changes are small, and there is no adverse effect on the control device of the variable speed motor.

In this embodiment, since the comparison value is incremented or decremented when the measured pressure data of the pressure sensor 8 is input into the microcomputer μcon, an appropriate delay time occurs, and walk hammer or chuckling in the control system can be prevented without adding any other steps.

In the embodiment described above, the comparison pressure generation means is provided as software, and the sampling operation of the measured pressure is performed by first setting hexadecimal data FF or OO in the microcomputer μcon, and then decrementing or incrementing this value. Microcomputer μcon output device OUT
and the comparator CP via the D/A converter _F1 .
Although this has been done by generating a comparison signal corresponding to the comparison pressure output to the sensor, it is also possible to generate the comparison signal randomly and converge toward the measured pressure. In addition, in the embodiment, the digital signal output from the output device OUTC of the microcomputer μcon is once converted into an analog signal by the D/A converter _F1 , and the comparison signal is converted to an analog level by the comparator CP and the pressure input through the operational amplifier OP. The measurement signals of the sensor 8 were compared, but if a pressure sensor that can directly obtain a digital signal output is used, both signals can be compared without going through a D/A converter.

Furthermore, in the embodiment, the speed command signal in the form of a digital code output from the output device OUTB of the microcomputer μcon is first transferred to the D/A converter.
Convert to analog signal with F ₂ and input variable speed control device INV
However, recently, digitally controlled inverter devices have become popular, so the output device
It is also conceivable to directly input the speed command signal from OUTB to the variable speed control device INV.

Furthermore, in the water supply system of the present invention, if there is a possibility that the pump capacity will change due to an increase or decrease in the number of customers, or the discharge pressure will change, etc., new information will be stored in the memory of the microcomputer μcon prior to pump operation. target discharge pressure, speed change control range for increasing or decreasing pump operating speed, pump operating limit speed (maximum rotation speed and minimum rotation speed),
Furthermore, it is convenient to add a control step for inputting data such as the initial rotational speed of the pump, which is provisionally determined at the initial stage of starting the water supply system.

In the above embodiments, it is possible to secure a simple sampling operation or the delay time necessary to prevent chattering, so it is possible to simplify the control operation and further reduce the memory cost, making it possible to obtain an inexpensive product. can.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, the pressure measured in the water supply pipe by the pressure sensor,
Even if the deviation from the predetermined target pressure becomes large for some reason, speed commands with large changes are not applied to the inverter device all at once, but speed commands in which the predetermined shift control width is sequentially increased or decreased are applied one after another. become. In addition, since the speed command is increased or decreased sequentially at predetermined time intervals when pressure fluctuations in the water supply pipe are stabilized due to an increase or decrease in the speed change control width,
The pump is accelerated or decelerated while pressure fluctuations within the water supply pipe are always suppressed.

Therefore, we have developed a water supply system that can prevent the occurrence of water hammer or chattering and maintain the discharge pressure almost constant without requiring a proportional-integral circuit or any special means equivalent to this. It can be obtained cheaply.

[Brief explanation of drawings]

Fig. 1 is a block diagram for explaining the configuration of one embodiment of the present invention, Fig. 2 is a characteristic curve diagram for explaining the operation of a conventional water supply device, and Fig. 3 is a control system of the conventional device. 4 is a timing diagram for explaining the control characteristics of the conventional device, FIG. 5 is a block diagram for explaining the configuration of the operation control device of the embodiment, and FIGS. Fig. 7 is a flowchart for explaining the control procedure of the embodiment device, Fig. 8 is a diagram showing the output characteristics of the pressure sensor, and Figs. 9 to 10 are characteristics for explaining the operation operation of the embodiment device. It is a curve diagram. 4...Pump, 7...Water supply pipe, 8...Pressure sensor, INV...Variable speed drive means, _H0 ...Target pressure.

Claims (1)

[Claims] 1. A pump, a variable speed electric motor that drives the pump, an inverter device that controls the speed of the variable speed electric motor, and a pressure sensor that detects the pressure in a water supply pipe connected to the pump. and a microcomputer, and a memory storing a speed change control width of the variable speed electric motor, and a controller that causes the inverter device to sequentially increase or decrease the speed change control width so that the pressure measured by the pressure sensor matches a predetermined target pressure. and an operation control device that gives a speed command, and when the two pressures do not match, the operation control device operates at predetermined time intervals at which pressure fluctuations in the water supply pipe are stabilized due to an increase or decrease in the speed change control width. To,
A water supply device characterized in that a speed command to the inverter device is increased or decreased by the speed change control width.