JP4741312B2 - Variable speed water supply device - Google Patents

Description

  The present invention relates to a variable speed water supply apparatus including a motor pump that is used for pumping water from a well and is operated at a variable speed by a frequency converter such as an inverter.

  For example, as a pump drive source, a motor whose rotation can be controlled by a frequency converter (inverter) is widely used to operate the pump at a variable speed. By using the inverter, the operation can be performed regardless of the power source, and by performing the variable speed operation, the pump discharge side can be controlled to have a constant pressure control.

  FIG. 7 shows a conventional water supply system using a pump for variable speed operation. The water supply pump 1, a variable speed motor 4 having an inverter 2 and a motor 3 for driving the pump 1, and an output of the inverter 2 are shown. And a control device 5 for controlling the frequency of the power to be generated. The control device 5 detects a discharge water pressure Po of the discharge pipe 7 provided in the discharge pipe 7 of the water supply pump 1 and a target pressure calculation means 6 for calculating a control target pressure in accordance with a predetermined logic. A pressure detecting means 8 for outputting a Po signal, a rotational speed detecting section 9 for detecting the rotational speed of the variable speed electric motor 4 and outputting a signal of the rotational speed Hzx, and a discharge water pressure Po detected by the pressure detecting means 8. Is provided with rotation speed control means 10 for controlling the output of the inverter 2 so as to coincide with the calculated control target pressure. In this example, the rotation speed detection unit directly detects the output of the rotation control unit.

  During the pump operation, the pressure in the pipe is detected by the pressure detection means 8 and the motor 3 is operated at a variable speed by the inverter 2 while calculating the target pressure according to the operation state. When the pressure is lower than the target pressure, the number of revolutions is increased and the pump discharge side is controlled to keep the target pressure value constant. Furthermore, when the target pressure is changed so that the pressure in the terminal equipment such as a hot water shower becomes constant according to the operation state, the estimated terminal pressure constant control is performed. If the pump is controlled at a variable speed in this way, not only the pressure fluctuation on the pump discharge side can be kept low, but also the pressure tank can be made smaller compared to the conventional on / off control, and the ground unit can be made smaller.

  In the variable speed water supply apparatus having the above configuration, the target pressure calculation means 6 calculates the target pressure PV corresponding to the rotation speed Hzx by a function {PV = f (Hzx)} of the rotation speed Hzx, and represents the target pressure representing the target pressure. PV signal is output. Further, the rotational speed control means 10 controls the speed of the variable speed motor 4 in response to the target pressure PV and the discharge water pressure Po so that the discharge water pressure Po matches the target pressure PV.

FIG. 8 is a diagram for explaining the relationship between the pump flow rate and the pressure in such a conventional variable speed water supply apparatus. The symbols used in this figure are as follows.
PA: Maximum water volume target pressure (= lift to the highest position + required pressure at the highest position + piping resistance at the maximum water volume)
PB: Deadline target pressure (= lift to the highest position + required pressure at the highest position)
Hzx: Pump rotation speed value detected by the rotation speed detection unit Hz0: Maximum pump rotation speed (normally 50 Hz or 60 Hz)
HzB: Pump rotation speed PA and PB for setting the target cutoff pressure PB at the cutoff (flow rate 0) are set by the input means at the time of system startup as the specifications of the water supply system. HzB is a value determined by the cutoff target pressure PB and the pump, and is generally represented by HzB = (PB / P0) ^1/2 × Hz0 in terms of pump characteristics. In the figure, lines L0 and LB are performance curves of the pump at rotation speeds Hz0 and HzB, respectively, and a line LL is a curve representing pressure loss in piping from the pump to the terminal equipment.

In the state set in this way, in the target pressure calculation means 6, by inputting the pump rotation speed Hzx,
a) PV = PB when Hzx <HzB (1)
b) For HzB ≤ Hzx ≤ Hz0 PV = ((Hzx-HzB) / (Hz0-HzB)) ^1/2 x (PA-PB) + PB (2)
c) When Hz0 <Hzx PV = PA (3)
Are programmed to sequentially calculate the target pressure PV. According to this, when the pump speed is low, the target pressure is guided to the cutoff target pressure PB, and when the pump speed is high, the intermediate rotation is performed so that the target pressure is guided to the maximum water amount target pressure PA. In number, the pump is controlled to lead to the pressure at a point on the straight line connecting the maximum and minimum operating points. This curve approximates the pressure loss characteristic curve LL. By such a method, without using a flow meter, the end pressure can be controlled to be constant regardless of the flow rate, and an effect of smooth device operation and energy saving can be obtained.

  By the way, such a pump may be installed in a water source such as a well. FIG. 9 shows a water supply device that pumps water from a deep well and supplies it to consumers. The submersible pump 11 installed in the well, the discharge pipe 13 led out from the submersible pump 11, and the submersible pump 11 are supplied with power. And it has the control panel 14 which accommodates the apparatus and control apparatus for controlling this. The discharge pipe 13 is provided with a check valve 16, a flow switch 18, a pressure sensor 20, and a pressure tank 22, and these and the control panel 14 are accommodated in the ground unit 24. Also in this water supply device, the estimated terminal pressure constant control as shown in FIG. 8 is performed by the control device 5 having the configuration shown in FIG.

  In such a water source such as a well, the water level may fluctuate depending on seasonal changes or usage conditions. Since the estimated terminal pressure constant control as described above is performed on the premise that the pressure on the suction side is constant, if the pressure on the suction side changes due to water level fluctuation or the like, accurate terminal pressure constant control cannot be performed, Pressure fluctuation will increase. Such pressure rise is the use of extra power, while pressure drop is directly connected to the inconvenience of consumers, so PA and PB are set high with a margin, and again Leads to use.

Japanese Patent No. 1892600 Japanese Patent No. 3291007

  Accordingly, in order to efficiently perform the estimated terminal pressure constant control in a water source such as a well, it is necessary to correct the calculation formula of the estimated terminal pressure control based on the pressure change on the suction side. As a method of knowing the pressure change on the suction side, there are a method of installing a water level meter in the well and calculating the pressure on the suction side from the water level, and a method of measuring the suction side pressure by providing a pressure sensor on the suction side. .

  For example, as shown in FIG. 9, a method is conceivable in which a water level sensor 29 is installed in a well and the suction side pressure is calculated from the water level. This water level sensor 29 applies an ultrasonic wave from the upper surface of the well to the surface of the well and measures the water level by reflection. The water level sensor 29 detects the fluctuation value of the water level, and uses this value as the suction pressure fluctuation value to sequentially correct the arithmetic expression of the target pressure calculation means. The correction method is proposed in Patent Document 2 and the like. Thus, if the fluctuation value PP of the water level is detected by the water level sensor, the estimated terminal pressure can be controlled on the pump discharge side even if the well water level fluctuates. By using the correction control by the water level sensor 29, it is possible to perform the estimated terminal pressure control with high accuracy.

  However, installation of the water level sensor 29 and the pressure sensor is costly. Considering the fact that the installation location is in a well and difficult to maintain, considerable maintenance costs are required to operate them stably. As for the method of providing a pressure sensor on the suction side, a suction pipe to which the pressure sensor is attached is necessary. However, in the case of a submersible pump, the suction side pressure sensor cannot be attached because there is no suction pipe structurally.

  On the other hand, there is a method of correcting the push-side pressure value during a test run by using the discharge pressure actually detected at a specific pump speed in a low-load state as an approximate value of the discharge pressure at the pump speed in the cutoff state. Conceivable. However, when a flow rate detector such as a flow switch for detecting a minimum amount of water is used to detect a low load, the flow switch is not practical because the minimum amount of water cannot be distinguished from the deadline state. Of course, a flow meter may be used, but the flow meter is expensive and the advantage of not using a pressure sensor or the like on the suction side is offset. In any case, when the demand water volume suddenly becomes 0, etc., the pump operating speed cannot be reduced in time, and the detected pressure on the discharge side is considerably higher than the pressure that should be originally intended for the water volume at that time. Since it becomes high, the correction value of the suction side pressure may deviate greatly.

  The present invention has been made in view of the above circumstances, and corrects the calculation formula of the estimated end pressure control corresponding to the change in the water level at low cost without installing a pressure sensor or a water level sensor on the suction side. It aims at providing the water supply apparatus which can do.

  In order to achieve the object, the variable speed water supply apparatus according to claim 1 is a variable speed water supply apparatus that uses a pump using a variable speed motor and controls the pump discharge side pressure at a constant estimated terminal pressure. Rotational speed value in a specific pressure state at the start of the pump as a target deadline for obtaining the target deadline for obtaining the final target pressure in the constant terminal pressure control, It is characterized by taking in and using.

  Here, the specific pressure state at the time of starting the pump means a pressure condition at the time of starting the pump that is predetermined in terms of control as a trigger for taking in the rotational speed value, and is a small water amount state at the time of starting the pump, It is desirable that the pump is in a state where it is estimated that the pump is operating in the vicinity of the cutoff target pressure. With such a configuration, it is possible to obtain the target shut-off speed that is a reference for the estimated terminal pressure constant control without providing a means for directly or indirectly detecting the suction side pressure.

The invention according to claim 1 is characterized in that the rotation speed value of the pump after the pressure on the pump discharge side has changed from a downward trend to an upward trend is used as the target cutoff rotational speed. At the time of starting the pump, it is considered that the pump is stably operating along the characteristic curve after the pressure on the discharge side of the pump has changed from the downward trend to the upward trend. Therefore, if it is estimated that the pump is operating near the cutoff target pressure and the amount of water is small, the target cutoff speed can be acquired from the discharge side pressure.

Variable speed water supply apparatus according to 請 Motomeko 2 is the invention according to claim 1, to calculate the change in the reference pressure value of the pump suction side on the basis of the deadline target speed the captured, based on this The pump discharge side pressure is controlled to be constant at the estimated end pressure.

According to the variable speed water supply apparatus according to claim 1 and claim 2 , without installing a pressure sensor or a water level sensor on the suction side, the calculation formula of the estimated terminal pressure control can be obtained at low cost corresponding to the change in the water level. The water supply apparatus which can correct | amend can be provided.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a water supply device that pumps water from a deep well and supplies it to a consumer. And it has the control panel 14 which accommodates the apparatus and control apparatus for controlling this. The discharge pipe 13 is provided with a check valve 16, a flow switch 18, a pressure sensor 20, and a pressure tank 22, and these and the control panel 14 are accommodated in the ground unit 24.

  The submersible pump 11 includes a drive motor 12, and the drive motor 12 is supplied with an alternating current having a frequency controlled from an inverter 26 installed in the control panel 14 via a cable 28. A predetermined gas is sealed in the pressure tank 22, and this pressure rises if the water supply device continues to operate when the consumer is not in use. The pressure sensor 20 detects this pressure and sends the output signal to the control device 30 installed in the control panel 14. Even after the pump is stopped by the action of the pressure tank 22 and the check valve 16, the pressure in the discharge pipe is maintained at a constant pressure unless water is used. The flow switch 18 provided on the pump discharge side detects that the flow rate in the discharge pipe 13 has become a small amount of water below a certain level. For example, the pump is rotating at a predetermined speed but the amount of water is small. At some point, abnormalities such as clogged valves can be detected.

  As shown in FIG. 2, the control device 30 includes an input unit 32 for inputting various driving operations and conditions, a target pressure calculation unit 34 for calculating a target pressure based on the input set value, a pump A rotation speed detector 36 for detecting the rotation speed of the inverter 26 based on the target pressure output value from the target pressure calculator 34 and the measured output value from the pressure sensor 20, have. The basic configuration of the control device 30 is the same as that of the conventional case shown in FIG. Moreover, the rotation speed detection part 36 has detected the output of the rotation control part directly.

  The control panel 14 has a pressure setting function and can set “starting pressure Pstart” and “stopping pressure Pstop”. The control panel 14 is provided with a display panel (not shown) so that the pump can be operated in various ways such as “manual operation” or “automatic operation”. In “manual operation”, the operation frequency is manually operated to operate the pump at an arbitrary frequency. In the “automatic operation”, as will be described later, when the discharge pressure becomes a set value (starting pressure) or less, the pump is started to perform the estimated terminal pressure constant control, and when the flow amount is reduced and the flow switch 18 is activated, Accumulate pressure (for example, up to a stop pressure) to stop the pump. In addition to the flow switch 18, as a small water amount detection means, there is a method in which a decrease in pump speed or electric motor power is used as a determination condition. As the starting pressure, the target pressure PB at the point where the flow rate is zero or a value in the vicinity thereof is used.

  In the variable speed water supply apparatus having the above configuration, the target pressure calculation unit 34 calculates the target pressure PV corresponding to the rotation speed Hzx by a function {PV = f (Hzx)} of the rotation speed Hzx, and represents the target pressure representing the target pressure. PV signal is output. Further, the rotation speed control unit 38 controls the speed of the drive motor 12 in response to the target pressure PV and the discharge water pressure Po so that the discharge water pressure Po matches the target pressure PV.

The method of constant control of the estimated terminal pressure in this device is the same as that in the conventional variable speed water supply device described with reference to FIG. That is, the following numerical values are set.
PA: Maximum water volume target pressure in this water supply system PB: Deadline target pressure in this water supply system Hz0: Maximum pump speed (usually 50 Hz or 60 Hz)
HzB: Number of rotations of the pump for releasing the target cutoff pressure PB by closing (flow rate 0)

And the target pressure calculating part 34 is based on the input of pump rotation speed Hzx,
a) When Hzx <HzB PV = PB (1)
b) For HzB ≤ Hzx ≤ Hz0 PV = ((Hzx-HzB) / (Hz0-HzB)) ^1/2 x (PA-PB) + PB (2)
c) When Hz0 <Hzx PV = PA (3)
In this manner, the target pressure PV is sequentially calculated.

  The control device 30 is different from the conventional case in that the rotation of the pump is used to shut out the target shutoff pressure PB at a predetermined timing based on the output value of the pressure sensor 20 at the start of the pump. A deadline target rotational speed acquisition unit 40 for taking in several HzBs (deadline target rotational speed) is provided. As shown in FIG. 4, the deadline target rotation speed acquisition unit 40 takes in the rotation speed HzBs when the output value of the pressure sensor 20 becomes PB or a value in the vicinity thereof when the pump is started. This process will be described below.

  FIG. 3A is a diagram of the operational characteristics of the normal pump described in FIG. 8, and the solid line coordinates indicate the case where the water level of the well is at the reference position. Here, considering the case where the water level rises from the reference position and a positive suction pressure (push-in pressure) Pp occurs, the performance curve of the pump shifts upward as shown in FIG. Therefore, it is a problem to newly obtain the pump rotation speed HzBs for obtaining the shutoff target pressure PB in this state by closing (flow rate 0), that is, obtaining the pump characteristic L2 '.

  As shown in FIG. 4, the pump is activated when the output value of the pressure sensor 20 becomes equal to or lower than the starting pressure Pstart. This starting pressure Pstart is generally set larger than the target cutoff pressure PB. Even if the pump is activated, the pressure continues to decrease while the rotational speed does not increase sufficiently, the pressure becomes PB or less, and at a certain point, the pressure starts to increase. While the pressure is decreasing, the pump is not in a stable state, that is, it is not operating on the characteristic curve, but it is considered that it is operating on the characteristic curve after starting to rise. Changes in the operating point of the pump during this time are schematically shown in FIG. Here, Qm is a small flow rate range at the time of start-up, a two-dot chain line indicates an unstable operation state, and a solid line indicates a stable operation state.

  As can be seen from these figures, the pump characteristic at a certain rotational speed is a flat curve while the flow rate is small. Therefore, when the amount of water is small, the discharge pressure at that time is substantially equal to the cutoff pressure at the number of rotations. Therefore, when starting the pump that is known to have a small amount of water, and operating along the characteristic curve, the rotation speed HzBs1 when the discharge pressure indicates PB approximated the new cutoff target rotation speed HzBs. It is considered to be a value.

  Here, as shown in FIG. 5, since the water amount Qm at this time is not strictly 0, the cutoff pressure of the pump characteristic curve at the rotational frequency HzBs is PB + α, which is slightly higher than PB. The difference α is not a problem in practice, but the rotation speed HzBs2 when the pressure becomes (PB−β) is set as the cutoff target rotation speed so that the cutoff pressure becomes PB in consideration of this difference. This is the second method. Although this method is accurate in principle, there is a problem that it is difficult to estimate the value of β as long as the flow rate is not known. For example, if β is too large, HzBs2 cannot be taken in if the pressure does not drop that much. Therefore, it is conceivable to use the rotation speed HzBs3 when the pressure changes from lowering to increasing. This is because it is considered that the pump is operating on the characteristic curve after the pump discharge pressure starts to rise, and the characteristic curve is considered to be close to L2 '.

  As a feature of the above three values, the rotational frequency HzBs1 when the pressure indicates PB is slightly higher than the original value, and the rotational frequency HzBs2 when the pressure is (PB-β) is close to an approximation, but β Is difficult, and the rotation speed HzBs3 when the pressure changes from lowering to rising becomes a slightly lower value. Therefore, it is conceivable to compensate for the disadvantage by using some of these values in combination. For example, it is conceivable to use an appropriate value between the rotational speed HzBs1 when the pressure indicates PB and the rotational speed HzBs3 when the pressure changes from falling to rising. In this case, a simple average value, a weighted average value, or another calculation method may be used. Alternatively, the rotational speed HzBs2 when the pressure becomes (PB-β) may be preferentially used, and when the pressure cannot be obtained, the rotational speed HzBs3 when the pressure changes from lowering to rising may be used.

By replacing the target cutoff speed HzBs obtained as a result with the original target cutoff speed HzB, the estimated terminal pressure constant control at the suction pressure is performed. Specifically, the target pressure calculation unit 34 is based on the input of the pump speed Hzx.
a) When Hzx <HzBs PV = PB (1 ′)
b) For HzBs ≦ Hzx ≦ Hz0 PV = {(PA−PB) / (Hz0−HzBs)} × (Hzx−HzBs) + PB (2 ′)
c) When Hz0 <Hzx PV = PA (3 ′)
In this manner, the target pressure PV is sequentially calculated. In the equation (2 ′), control is performed along the pressure loss characteristic L3 ′ in FIG.

  In this embodiment, the correction is performed by replacing HzB in Expression (2), and the correction of Hz0 is not performed. Actually, Hz0 also fluctuates with fluctuations in the suction pressure, but for the sake of simplicity, the effect can be obtained only by replacing HzB.

The HzB obtained in this way is not the rotational speed at which PB is output when the flow rate is 0, but is a value in the vicinity thereof, which is not problematic in practice. Further, even in the case of HzB obtained in this way, if the water level of the well decreases (if the suction pressure decreases), the HzB increases, and if the water level of the well decreases (if the suction pressure increases), the HzB decreases. Therefore, compared with the case where the suction pressure is not corrected, the pressure fluctuation of the demand destination is reduced, and it is possible to suppress useless energy consumption.
In addition, since the detection is performed in a state where the flow rate is flowing, the pump is not in the deadline state, so an unnecessary process for identifying the deadline state is not required.

With reference to FIG. 6, the operation of the variable speed water supply apparatus of this embodiment. Here, among the methods described above, the rotational frequency HzBs1 when the pressure P indicates PB is employed. First, in step 1, the control device 30 determines whether or not the output value P of the pressure sensor 20 has become equal to or less than the starting pressure Pstart. Next, in step 3, HzB0 is set as a provisional HzB value for controlling the operation of the pump. The use of this HzB0 is a very short time until a new HzBs is acquired. Usually, the HzB set at the previous operation of the pump is used.

  Next, in step 4, it is determined whether a new HzB has already been set. Of course, since it is not set at first, the routine for setting HzB is entered. In step 5, it is determined whether or not P has turned upward. This is because, while P is in a downward trend, the pump is not operating stably along its characteristic curve, so new HzBs cannot be taken in. If it is determined that P has turned upward, it is determined in step 6 whether or not P has reached PB. If so, in step 7, the rotational speed Hzx at that time is taken in as HzBs1, and HzB Replace with.

  Thereafter, the control target pressure (SV) is calculated by the equation (2) in Step 8 using the new deadline target rotation speed HzBs. In Step 9, for example, the output value P of the pressure sensor 20 and the calculated SV Thus, PI control at the rotational frequency Hzx is performed. Then, returning to step 4, it is determined whether or not a new HzB has been set, but since it has already been set, steps 8 and 9 are sequentially repeated thereafter.

  On the other hand, if the conditions of step 5 and step 6 are not satisfied, the process returns to step 4 through steps 8 and 9, and steps 5 and 6 are executed again. This routine is executed until these conditions are satisfied. repeat. In step 6, if it is within a few percent before and after PB, it may be determined that it is PB. In this case, when Pstart is larger than PB, the pressure may not drop below PB when starting the pump, or may pass through PB during the pressure drop after starting the pump, but when the pressure starts to increase at that time What is necessary is just to set HzB using Hzx of this, or Hzx when it becomes PB after starting to rise.

In the process of FIG. 6, the rotation speed at the time when the pressure P reaches PB after the pressure P changes from the decrease to the increase is adopted, but the rotation speed HzBs 3 when the pressure changes from the decrease to the increase, The same applies to the case of using the rotational frequency HzBs2 when the value becomes (PB-β) or a combination thereof.

  In the above embodiment, the obtained rotation speed HzB is used as a value for rewriting the target pressure calculation formula (3). However, a corresponding reference pressure P0 obtained from this rotation speed HzB and a predetermined pressure value PB are used. The suction pressure value Pp may be obtained by calculation from the difference between and the suction pressure value Pp. If Pp is obtained and controlled in this way, the control process that has been corrected by inputting Pp by the pressure sensor 20 can be used as it is.

  As in this embodiment, in the case of a well pump, the fluctuation of the suction pressure during pump operation (fluctuation in water level) is less frequent than in the direct connection type water supply apparatus directly connected to the water main, and the groundwater level due to the season The effect of fluctuation is greater. Therefore, it is particularly suitable for the well pump to determine the correction value of the suction pressure when starting the pump as in the present invention.

  Of course, the present invention is not limited to the well pump, and can be applied to a water supply apparatus from a water source whose pushing pressure fluctuates. For example, even when the water level fluctuates frequently, if the correction is always performed at the time of startup, the automatic correction is made constantly and the appropriate estimated terminal pressure constant control can always be performed. .

It is a figure which shows the structure of the whole variable speed water supply apparatus of this invention. It is a figure which shows the structure of the control part of the variable speed water supply apparatus of this invention. It is a figure explaining operation | movement of the variable speed water supply apparatus of this invention. It is a figure explaining the control process of the variable speed water supply apparatus of this invention. Similarly, it is a figure explaining the control process of the variable speed water supply apparatus of this invention. It is a flowchart explaining the control process of the variable speed water supply apparatus of this invention. It is a figure which shows the conventional variable speed water supply apparatus. It is a figure explaining operation | movement of the conventional variable speed water supply apparatus. It is a figure which shows the conventional variable speed water supply apparatus for wells.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Submersible pump 12 Drive motor 13 Discharge piping 14 Control panel 15 Display panel 16 Check valve 18 Flow switch 20 Pressure sensor 22 Pressure tank 24 Ground unit 26 Inverter 28 Cable 30 Control apparatus 32 Input part 34 Target pressure calculating part 36 Number of rotations Detection part 38 Rotational speed control part 40 Deadline target rotational speed acquisition part

Claims (2)

In a variable speed water supply apparatus that uses a pump that uses a variable speed motor and controls the pump discharge side pressure at a constant estimated terminal pressure,
Incorporating and using the rotational speed value of the pump after the pressure on the pump discharge side at the time of starting the pump has changed from a downward trend to an upward trend as the target cutoff speed for obtaining the target cutoff pressure in the estimated terminal pressure constant control A variable speed water supply device characterized by A change in the reference pressure value on the pump suction side is calculated based on the incorporated target rotation speed, and the pump discharge side pressure is controlled to be constant at the estimated end pressure based on the corrected reference pressure value. The variable speed water supply apparatus according to claim 1, wherein

Images