JP6665009B2 - Pump system, control device, and control method - Google Patents

Description

  The present invention relates to a pump system, a control device, and a control method using a pump for supplying water to a buffer water tank installed at an upstream end of a pipeline for distributing and dividing water by natural flow. In particular, the present invention relates to a pump system, a control device, and a control method capable of realizing a reduction in maintenance and management costs by suppressing the frequency of starting the pump and a reduction in operating costs by reducing power consumption.

  Conventionally, pump devices such as water intake pump device, water supply / distribution pump device, water supply pump device, agricultural irrigation pump device, pumping pump device, river water pumping device, oil pipeline pump device, drainage pump device, etc. It has been known. In such a pump device, there is a device that feeds water to a discharge water tank (hereinafter, also referred to as a buffer water tank) installed at an upstream end of a pipeline for performing water distribution and water distribution by following demand water amount by natural flow. Demand water volume is the amount of natural flow out from the buffer tank. Then, in the pump device, in order to maintain the water level of the buffer water tank that fluctuates according to the demand water amount in the operation operation water level range, pump operation number control for increasing or decreasing the operation number of the arranged pumps is performed (for example, Patent Document 1). 1).

  In the conventional pump operation number control, the number of pumps operated is set such that the buffer water tank, which is the water supply destination, secures a water level against the outflow of demand water amount. That is, the pump is started when the buffer tank water level decreases, and stopped when the buffer tank water level rises and recovers sufficiently. If the amount of water supplied is insufficient with respect to the amount of demanded water, the pumps are sequentially restarted each time the water level further decreases. Eventually, when the demand water volume decreases, the pump stops when the buffer tank water level rises to a certain water level. Each time the water level rises, the pump is stopped sequentially.

Japanese Utility Model Publication No. 60-184109

  The pump has a characteristic that the flow rate changes according to the total head. When the total head is small, the flow rate increases, and when the total head is large, the flow rate decreases. In other words, the amount of water supply changes according to the buffer tank water level. The pump water supply amount increases when the buffer tank water level is low, and the pump water supply amount decreases when the buffer tank water level is high.

  In addition, the demand water volume is the natural flow outflow from the buffer water tank, but it is adjusted to the required water volume at the demand end according to the upstream pressure, and the upstream pressure is not necessarily the pressure required for the demand water volume. There is a case where extra pressure is applied without limitation. That is, the buffer tank water level is not always an appropriate water level and may be an unnecessarily high water level. In this case, when the rotation speed of the pump is fixed, there is a case where extra water is consumed by pumping water to an extra water level.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a pump system, a control device, and a control method that can reduce power consumption of a pump and reduce operating costs.

  A pump system according to a first aspect of the present invention includes at least one motor, at least one pump driven by the motor and sucking water from a suction water tank, and a discharge from which water pumped by the pump is discharged. A water supply flowmeter that measures a water supply flow rate that is a flow rate of water sent to the water tank, and a control device that controls the motor, the control device reducing the number of revolutions of the pump by a first set amount. Controlling the motor to maintain, after a lapse of a predetermined time, determine whether or not the water supply flow rate has returned to the water supply flow rate target value, and as a result of the determination, when the water supply flow rate has returned to the water supply flow rate target value, The motor is controlled to maintain the number of revolutions of the pump reduced by a first set amount.

  According to this configuration, when the water supply flow rate returns to the water supply flow rate target value, the rotation speed of the pump can be reduced. As a result, the water level of the discharge water tank is lowered and the head is lowered, so that the power consumption of the pump can be suppressed and the operating cost can be reduced.

  The pump system according to a second aspect of the present invention is the pump system according to the first aspect, further comprising a discharge water tank water level meter for measuring a water level of the discharge water tank, wherein the control device is configured to control the discharge water tank. Until the water level reaches the lower limit water level, the control for controlling the motor is repeated to reduce and maintain the rotation speed of the pump by the first set amount.

  According to this configuration, the discharge water tank water level drops to the lower limit water level, and the head drops to the limit, so that the power consumption of the pump can be further suppressed and the operating cost can be further reduced.

  The pump system according to the third aspect of the present invention is the pump system according to the first or second aspect, wherein the control device determines that the water supply flow rate does not return to the water supply flow rate target value as a result of the determination. The motor is controlled to increase and maintain the rotation speed of the pump by a second set amount.

  According to this configuration, when the water supply flow rate does not return to the water supply flow rate target value, the number of rotations of the pump can be increased, so that shortage of the water supply flow rate can be avoided. This can prevent shortage of water in the discharge water tank 3 and improve the stability of water supply from the discharge water tank.

  The pump system according to a fourth aspect of the present invention is the pump system according to the third aspect, wherein after a predetermined time has elapsed from the time when the motor was controlled to be increased and maintained by the second set amount, It is determined whether or not the water supply flow rate has returned to the water supply flow rate target value, and as a result of the determination, if the water supply flow rate has returned to the water supply flow rate target value, the rotation speed of the pump is reduced and maintained by a first set amount. If the water supply flow rate has not returned to the water supply flow rate target value, the motor is controlled to further increase and maintain the rotation speed of the pump by a second set amount.

  According to this configuration, if the water supply flow rate has not returned to the water supply flow rate target value after the pump rotation speed is once increased by the second set amount, the pump rotation speed is increased. Therefore, the water supply flow rate can be increased so as to be closer to the water supply flow rate target value. Thereby, the water supply flow rate can be made closer to the water supply flow rate target value, so that the stability of water supply to the discharge water tank can be improved. On the other hand, if the water supply flow rate has returned to the water supply flow rate target value after the pump rotation speed has been increased by the second set amount once, the pump rotation speed can be reduced. As a result, the water level of the discharge water tank is lowered and the head is lowered, so that the power consumption of the pump can be suppressed and the operating cost can be reduced.

  A pump system according to a fifth aspect of the present invention is the pump system according to any one of the first to fourth aspects, wherein the demand water flow meter measures a demand water amount which is a natural flow-out flow amount from the discharge water tank. And the control device controls the number of revolutions of the pump so that the flow rate of the water is adjusted to the demanded water amount.

  According to this configuration, the number of rotations of the pump is controlled, and the flow rate of the supplied water and the demanded water amount are in an equilibrium state. For this reason, it is possible to avoid a situation in which one pump repeats starting and stopping, so that it is possible to solve a problem that extra power is consumed.

  A pump system according to a sixth aspect of the present invention is the pump system according to any one of the first to fifth aspects, wherein a flow rate of water discharged by the pump and an allowable maximum rotation number of the pump are stored in association with each other. The storage device further includes a storage unit in which the flow rate of the water discharged by the pump and an allowable minimum rotation speed of the pump are stored in association with each other, and the control device includes an allowable maximum rotation speed corresponding to the water supply flow rate target value. Reading the permissible minimum rotation speed from the storage unit, and determining whether the current rotation speed of the pump is equal to or higher than the rotation speed according to the minimum permissible rotation speed and equal to or lower than the maximum permissible rotation speed, and When the rotation speed becomes a rotation speed according to the allowable minimum rotation speed, control is performed to maintain the rotation speed so as not to fall below the allowable minimum rotation speed, and the current rotation speed of the pump is changed to the allowable maximum rotation speed. When it becomes to maintain the rotational speed so as not to exceed the permissible maximum speed.

  According to this configuration, it is possible to prevent the rotation speed of the pump from deviating from an appropriate operation range. For this reason, it is possible to prevent that water cannot be supplied even during operation, and that irregular operation conditions such as cavitation, vibration of the pump, and excess horsepower are provided.

  The pump system according to a seventh aspect of the present invention is the pump system according to any one of the first to sixth aspects, further comprising a discharge water tank water level meter for measuring a water level of the discharge water tank, wherein the control device is It is determined whether or not the water level of the discharge water tank measured by the discharge water tank water level meter has reached a lower limit water level, and when the water level of the discharge water tank has reached the lower limit water level, the rotation speed is maintained so as not to be further reduced. .

  According to this configuration, it is possible to operate the head at a head in which the water level in the discharge water tank is appropriate and the power consumption is suppressed as much as possible, while avoiding a situation where the water is not discharged from the discharge water tank so as not to fall below the lower limit water level. Of water supply from the fuel cell can be improved.

  The pump system according to an eighth aspect of the present invention is the pump system according to any one of the first to seventh aspects, further comprising a discharge water tank water level meter for measuring a water level of the discharge water tank, wherein the control device is Comparing the water level of the discharge water tank measured by the discharge water tank water level meter with an upper limit water level or a lower limit water level, and correcting the water supply flow rate target value according to the comparison result.

  According to this configuration, it is possible to prevent the water level of the discharge water tank from exceeding the upper limit water level, so that it is possible to prevent water from overflowing from the discharge water tank and to prevent excessive water supply. Alternatively, it is possible to prevent the water level from falling below the lower limit water level, and the water is always held in the discharge water tank in a certain amount or more, so that it is possible to constantly discharge water from the discharge water tank, and to improve the stability of water supply from the discharge water tank. Can be improved.

  The pump system according to a ninth aspect of the present invention is the pump system according to any one of the first to eighth aspects, further comprising a pressure gauge that measures a water supply pressure that is a pressure of water sent to the discharge water tank. The control device compares the water supply pressure measured by the pressure gauge with an upper limit pressure or a lower limit pressure, and corrects the water supply flow rate target value according to the comparison result.

  According to this configuration, the water supply pressure can be prevented from exceeding the upper limit pressure, and the discharge pipe can be prevented from being damaged because excessive pressure is not applied to the discharge pipe. Alternatively, the pressure can be kept below the lower limit pressure, and the pressure enough to supply the water to the discharge water tank can be maintained, so that the stability of water supply from the discharge water tank can be improved.

  A pump system according to a tenth aspect of the present invention includes a suction water tank, at least one motor, at least one pump driven by the motor and sucking water from the suction water tank, and pumped by the pump. A discharge water tank from which water is discharged, a water supply flow meter that measures a water supply flow rate that is a flow rate of water sent to the discharge water tank, and a control device that controls the motor, wherein the control device is configured to rotate the pump. Controlling the motor to reduce and maintain the number by a first set amount, and after a lapse of a predetermined time, determine whether the water supply flow rate has returned to the water supply flow target value, and as a result of the determination, the water supply flow rate When the flow rate is returned to the target value, the motor is further controlled to reduce and maintain the rotation speed of the pump by a first set amount.

  According to this configuration, when the water flow rate is equal to or higher than the water flow rate target value, the rotation speed of the pump can be reduced. As a result, the water level of the discharge water tank is lowered and the head is lowered, so that the power consumption of the pump can be suppressed and the operating cost can be reduced.

  A control device according to an eleventh aspect of the present invention is a control device that controls a motor that drives a pump, wherein the motor controls the motor so that the rotation speed of the pump is reduced and maintained by a first set amount. A control unit configured to determine whether or not the flow rate of water sent to the discharge water tank has returned to the flow rate of water after a predetermined time has elapsed from the time when the motor is controlled to be reduced and maintained by the first set amount. A control unit, and if the result of the determination is that the discharge water tank water level reduction control unit determines that the water supply flow rate has returned to the water supply flow rate target value, the motor control unit further sets the number of rotations of the pump. The motor is controlled so that it is reduced and maintained by a fixed amount.

  According to this configuration, when the water flow rate is equal to or higher than the water flow rate target value, the rotation speed of the pump can be reduced. As a result, the water level of the discharge water tank is lowered and the head is lowered, so that the power consumption of the pump can be suppressed and the operating cost can be reduced.

  A control method according to a twelfth aspect of the present invention is a control method for controlling a motor that drives a pump, the method including controlling the motor so that the rotation speed of the pump is reduced and maintained by a first set amount. A step of determining whether or not the flow rate of water sent to the discharge water tank has returned to the target value of the flow rate after a lapse of a predetermined time from the time when the motor is controlled to be reduced and maintained by the first set amount. As a result, when it is determined in the determining step that the water supply flow rate has returned to the water supply flow rate target value, the method further includes a step of controlling the motor to reduce and maintain the rotation speed of the pump by a predetermined amount.

  According to this configuration, when the water flow rate is equal to or higher than the water flow rate target value, the rotation speed of the pump can be reduced. As a result, the water level of the discharge water tank is lowered and the head is lowered, so that the power consumption of the pump can be suppressed and the operating cost can be reduced.

  ADVANTAGE OF THE INVENTION According to this invention, when a water supply flow rate is more than a water supply flow rate target value, the rotation speed of a pump can be reduced. As a result, the water level of the discharge water tank is lowered and the head is lowered, so that the power consumption of the pump can be suppressed and the operating cost can be reduced.

It is a schematic structure figure of pump system S concerning this embodiment. It is an example of a table T1 in which a record of a set of a pump flow rate and a permissible maximum number of rotations of a pump 2 is stored. It is an example of a table T2 in which a record of a set of a pump flow rate and a permissible minimum rotation speed of the pump 2 is stored. 5 is a flowchart illustrating an example of a motor control process according to the embodiment. It is a graph which shows an example of a pump discharge flow rate target value correction according to a buffer water tank water level. Is a flowchart illustrating an example of a correction process of the water supply flow rate target value Qp ^SV. It is an example of the graph which shows the relationship of the water supply flow rate of a head, and the graph which shows the relationship between shaft power and the water supply flow rate. It is a flow chart which shows an example of processing of discharge water tank water level reduction control. It is a figure for explaining an appropriate operating range (operating point) of a pump.

  Hereinafter, the present embodiment will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of a pump system S according to the present embodiment. As shown in FIG. 1, the pump system S communicates with the suction water tank 1, the motors 15-1, 15-2, 15-3, the suction water tank 1, and the motors 15-1, 15-2, 15-. 3 is provided with pumps 2-1, 2-2, and 2-3 that suck water from the suction water tank 1. The pumps 2-1 to 2-3 are operated at a flow rate according to the demand water amount. Further, the pump system S includes a tachometer 18-1 for measuring the number of revolutions of the impeller of the pump 2-1; a tachometer 18-2 for measuring the number of revolutions of the impeller of the pump 2-2; And a tachometer 18-3 for measuring the number of rotations of the impeller. Hereinafter, the rotation speed of the impeller of the pumps 2-1 to 2-3 is referred to as the rotation speed of the pump. Further, the pump system S measures the rotation speed of the motor 15-1 by measuring the rotation speed of the motor 15-1, the rotation speed meter 19-2 of measuring the rotation speed of the motor 15-2, and the rotation speed of the motor 15-3. A tachometer 19-3 for measuring is provided.

  Further, the pump system S includes a suction tank water level meter 21 for measuring the water level of the suction water tank 1, an intake flow meter 23 for measuring the amount of water flowing into the suction water tank 1, and a water intake valve 24 provided at the suction port of the suction water tank 1. Is provided. Further, the pump system S includes one suction pipe 5 communicating with the suction water tank 1, a water stop valve 10 provided on the suction pipe 5, a suction pipe 5 branched from the suction pipe 5, and suctioned by the pumps 2-1 to 2-3. It has three branch suction pipes 6-1, 6-2, 6-3 connected to the respective ports. Further, the pump system S includes water shutoff valves 11-1, 11-2, and 11-3 provided in the branch suction pipes 6-1, 6-2, and 6-3, respectively.

  Further, the pump system S includes branch discharge pipes 7-1, 7-2, 7-3 communicating with the discharge ports of the pumps 2-1 to 2-3, and water pumped by the pumps 2-1 to 2-3. A discharge water tank 3 to be discharged and a discharge pipe 8 in which three branch discharge pipes 7-1, 7-2, 7-3 are gathered and communicate with the discharge water tank 3 are provided. In this manner, the pump 2 transfers the water sucked from the suction water tank 1 through the suction pipe 5 and the branch suction pipes 6-1 to 6-3 to the branch discharge pipes 7-1 to 7-3 and the discharge pipe 8. The water is supplied to the discharge water tank 3 through the water tank.

  Further, the pump system S is provided in each of the branch discharge pipes 7-1, 7-2, and 7-3, and is a check valve 9- that prevents backflow of water to the pumps 2-1 2-2, and 2-3. 1, 9-2 and 9-3. Further, a pump system S is provided in each of the branch discharge pipes 7-1, 7-2 and 7-3, and is a pump discharge valve capable of adjusting the flow rate of water discharged from the pumps 2-1, 2-2 and 2-3. 12-1, 12-2 and 12-3 are provided. Further, the pump system S is provided in each of the branch discharge pipes 7-1, 7-2, 7-3, and is a water stop valve capable of stopping water discharged from the pumps 2-1, 2-2, 2-3. 13-1, 13-2, and 13-3. Further, the pump system S is provided in the discharge pipe 8 and measures a water supply flow rate which is a flow rate of water sent to the discharge water tank 3, and a water supply flow meter 20 provided in the discharge pipe 8 and sent to the discharge water tank 3. A pressure gauge 17 for measuring a water supply pressure as a pressure is provided.

  Further, the pump system S includes a discharge water tank water level meter 22 for measuring the water level of the discharge water tank 3 (hereinafter, also referred to as discharge water tank water level), and a discharge amount of the natural water flowing out of the discharge water tank 3 provided on the discharge side of the discharge water tank 3. A demand water flow meter 25 for measuring a certain demand water amount, and a demand water outflow valve 26 provided on the discharge side of the discharge water tank 3 and capable of adjusting the flow rate of the demand water discharged by the discharge water tank 3 are provided.

  The pumps 2-1, 2-2, and 2-3 are collectively referred to as a pump 2. The three pumps 2 are arranged in parallel, but may be one or two or four or more. That is, at least one pump 2 may be used. Similarly, the motors 15-1, 15-2, and 15-3 are collectively referred to as a motor 15. Although three motors 15 are arranged, the number of the motors 15 may be the same as the number of the pumps 2, and may be one or two or four or more. That is, at least one motor 15 may be used. Similarly, the tachometers 19-1, 19-2, and 19-3 are collectively referred to as the tachometer 19.

  In this embodiment, it is assumed that the discharge water tank water level is higher than the suction water tank 1 water level, and that the total head of the pump 2 is larger than zero. As an example, in the present embodiment, a description will be given below assuming that the discharge water tank 3 is installed at a position higher than the suction water tank 1.

  Further, the pump system S includes a control device 30 that controls the motors 15-1, 15-2, and 15-3.

  In the conventional pump operation number control, if the demand water amount falls within the range of the water amount that can be supplied by driving k (k is a positive integer) pumps, the pump water supply amount and the demand water amount are in an equilibrium state, and the pump operation is stable. I do. However, if the demand water amount does not fall within the range of the amount of water that can be supplied by driving the k pumps (k is a positive integer), one pump repeatedly starts and stops, consuming extra power consumption. There was a problem.

  On the other hand, the control device 30 according to the pump system S according to the present embodiment controls the rotation speeds of the pumps 2-1 to 2-3 so that the water supply flow rate is adjusted to the demand water amount. Here, the water supply flow rate is the total water supply amount of the pumps 2-1 to 2-3. Thereby, the number of rotations of the pumps 2-1 to 2-3 is controlled, and the water supply flow rate and the demand water amount are in an equilibrium state. For this reason, it is possible to avoid a situation in which one pump repeats starting and stopping, so that it is possible to solve a problem that extra power is consumed.

  As shown in FIG. 1, the control device 30 includes a storage unit 31, a water flow target determination unit 32, a discharge water tank water level reduction control unit 33, a flow control unit 34, a number control unit 35-1, a speed control The circuit includes a circuit 35-2 and motor control units 36-1, 36-2, and 36-3.

  The storage unit 31 stores the flow rate of the water discharged from the pump 2 (hereinafter, also referred to as a pump flow rate) and the maximum allowable rotation speed of the pump 2 in association with each other, and stores the flow rate of the water discharged by the pump 2 and the minimum allowable rotation speed of the pump 2. The number is stored in association with the number. FIG. 2 is an example of a table T1 in which records of a set of a pump flow rate and a permissible maximum number of rotations of the pump 2 are stored. FIG. 3 is an example of a table T2 in which a record of a set of a pump flow rate and a minimum allowable rotation speed of the pump 2 is stored. For example, the storage unit 31 stores a table T1 in which a record of a set of the pump flow rate and the allowable maximum rotation speed of the pump 2 shown in FIG. 2 is stored, and a set of the pump flow rate and the allowable maximum rotation speed of the pump 2 shown in FIG. Is stored in association with the table T2 in which the record is stored. In the present embodiment, for simplicity, as an example, each of the motors 15-1, 15-2, 15-3 and each of the pumps 2-1, 2-2, 2-3 are of the same kind, It is assumed that the minimum rotation speed is common.

With reference to FIG. 4, processing of each unit of the control device 30 will be described. FIG. 4 is a flowchart illustrating an example of the motor control process according to the present embodiment.
(Step S101) First, the water flow rate target determination unit 32 sets a water flow rate target value Qp ^SV so that the water flow rate matches the demand water flow rate, using the demand water flow rate signal acquired from the demand water flow meter 25. Here, the demand water flow signal indicates the demand water flow rate.

(Step S <b> 102) Next, the water supply flow rate target determining unit 32 corrects the water supply flow rate target value Qp ^SV using the discharge water tank water level signal obtained from the discharge water tank water level meter 22 and the water supply pressure signal obtained from the pressure gauge 17. . Here, the discharge water tank water level signal indicates the water level of the discharge water tank 3, and the water supply pressure signal indicates the water supply pressure. The detailed processing will be described later with reference to FIG. The water supply flow rate target determination unit 32 outputs the corrected water supply flow rate target value Qp ^SV to the discharge water tank water level reduction control unit 33 and the flow control unit 34.

  (Step S103) Next, the discharge water tank water level reduction control unit 33 controls the discharge water tank water level using the discharge water tank level signal acquired from the discharge water tank level meter 22 and the water flow rate signal acquired from the water flow meter 20. Execute Here, the water supply flow rate signal indicates a water supply flow rate, which is a flow rate of water sent to the discharge water tank 3. The detailed processing will be described later with reference to FIG.

(Step S104) Next, the flow control unit 34 executes PID control in which the corrected water flow target value Qp ^SV is set as the target value SV, and the water flow obtained from the water flow meter 20 is the control amount PV. The flow controller 34 outputs the manipulated variable MV obtained by the PID control to the speed control circuit 35.

(Step S105) The number control unit 35-1 determines the number of pumps 2 to be operated according to the water supply flow rate target value Qp ^SV and the flow rate control method.

  (Step S106) The speed control circuit 35-2 performs the operation set by the number control unit 35-1 in the motors 15-1, 15-2, and 15-3 according to the operation amount MV acquired from the flow control unit 34. The command value of the number of rotations of the unit is determined. The speed control circuit 35 outputs the determined rotational speed command value to the corresponding motor control units 36-1, 36-2, 36-3.

  (Step S107) The motor control unit 36-1 performs control so that the rotation speed of the motor 15-1 is adjusted to the input rotation speed command value.

  (Step S108) In parallel with step S106, the motor control unit 36-2 controls the rotation speed of the motor 15-2 to match the input rotation speed command value.

  (Step S109) In parallel with steps S106 and S107, the motor control unit 36-3 controls the rotation speed of the motor 15-3 to match the input rotation speed command value.

Next, correction of the water supply flow rate target value Qp ^SV will be described with reference to FIGS. First, the reason why the water supply flow rate target value Qp ^SV needs to be corrected will be described with reference to FIG. FIG. 5 is a graph showing an example of the pump discharge flow rate target value correction according to the buffer water tank water level. As shown in FIG. 5, when an unbalance occurs between the pump water supply amount and the demand water amount for some reason and the water level rises unexpectedly abnormally, the pumping amount is larger than the demand water amount, which is indicated by an arrow A1. It is necessary to reduce the water flow rate. For this reason, it is necessary to correct (decrease) the water supply flow rate target value Qp ^SV or to forcibly reduce the rotation speed. On the other hand, when the water level drops abnormally, the amount of pumped water is smaller than the demanded water amount, so that it is necessary to increase the water supply flow rate as shown by the arrow A2. Therefore, it is necessary to correct (increase) the water supply flow rate target value Qp ^SV or to forcibly increase the rotation speed.
Basically, since the operation is performed at Qp = Qp ^SV , a small or large flow rate does not occur.

Next, the details of the rotational speed forced increase / decrease process for correcting the water supply flow rate target value Qp ^SV in step S102 in FIG. 4 will be described with reference to FIG. FIG. 6 is a flowchart illustrating an example of the correction process of the water supply flow rate target value Qp ^SV .
(Step S201) First, the water flow rate target determination unit 32 determines whether the water flow rate target value correction flag is ON. Here, when the water supply flow rate target value has been corrected in the past, the water supply flow rate target value correction flag is ON, and when the water supply flow rate target value has not been corrected in the past, the water supply flow rate target value correction flag has been set. Is OFF.

(Step S202) If it is determined in step S201 that the water flow rate target value correction flag is ON, the water flow rate target determination unit 32 compares the water flow rate target value correction value Qp ^SVC with the water flow rate target value corrected in the past. The process proceeds to step S204 with the correction value Qp ^SVC .

(Step S203) When it is determined in step S201 that the water supply flow rate target value correction flag is not ON, the water supply flow rate target determination unit 32 sets the water supply flow rate target value correction value Qp ^SVC to the water supply flow rate target value Qp ^SV, and performs the processing. Proceed to step S204.

(Step S204) Next, the water supply flow rate target determination unit 32, the discharge water tank water level L _T is determined whether or not more than the upper limit level L _T ^H. Here the discharge water tank water level L _T is obtained from the discharge water tank water level signal obtained from the discharge water tank water level gauge 22.

(Step S205) when the discharge water tank water level L _T is more than the upper limit water level in step S204, the water supply flow rate target determination unit 32, by a first correction amount DerutaQp ^SVH remove water flow target value correction value Qp ^SVC (Qp ^SVC = Qp ^SVC− ΔQp ^SVH ) (step S205-1) or reduce the number of revolutions (step S205-2). Thereafter, the process proceeds to step S211.

(Step S206) when the discharge water tank water level L _T in step S204 is less than the upper limit water level, the water supply flow rate target determination unit 32 determines whether the discharge water tank water level L _T is less than the lower limit level L _T ^L.

In (Step S207) Step S206, when the discharge water tank water level L _T is less than the lower limit level L _T ^L, water flow rate target determination unit 32, only the second correction amount DerutaQp ^SVL increased water flow rate target value correction value Qp ^SVC (Qp ^SVC = Qp ^SVC + ΔQp ^SVL ) (step S207-1) or increase the rotation speed (step S207-2). Thereafter, the process proceeds to step S211.

In (Step S208) Step S206, when the discharge water tank water level L _T is not equal to or less than the lower limit level L _T ^L, water flow rate target value correcting value Qp ^SVC is unchanged value (Qp ^SVC = Qp ^SVC). Thereafter, the process proceeds to step S212.

(Step S209) water flow target determining unit 32 determines water pressure Hp is whether or not the upper limit pressure Hp ^H or more. If the water supply pressure Hp is equal to or higher than the upper limit pressure Hp ^H , the process proceeds to step S205, and the water supply flow rate target determination unit 32 reduces the water supply flow rate target value correction value Qp ^SVC by the first correction amount ΔQp ^SVH (Qp ^SVC = Qp ^SVC -ΔQp ^SVH ). Thereafter, the process proceeds to step S211.

In (Step S210) Step S209, if the water supply pressure Hp is not the upper limit pressure Hp ^H above, water flow rate target determination unit 32 determines water pressure Hp is or smaller than a lower limit pressure Hp ^L. When the water supply pressure Hp is equal to or lower than the lower limit pressure Hp ^L , the process proceeds to step S207, and the water supply flow rate target determination unit 32 increases the water supply flow rate target value correction value Qp ^SVC by the second correction amount ΔQp ^SVL ( Qp ^SVC = Qp ^SVC + ΔQp ^SVL ). Thereafter, the process proceeds to step S211. If the water supply pressure Hp is not equal to or lower than the lower limit pressure Hp ^L , the process proceeds to step S208, and the water supply flow rate target value correction value Qp ^SVC remains unchanged (Qp ^SVC = Qp ^SVC ). Thereafter, the process proceeds to step S212.

  (Step S211) The water flow rate target determination unit 32 turns on a water flow rate target value correction flag. Thereafter, the process proceeds to step S213.

  (Step S212) The water flow rate target determination unit 32 turns off the water flow rate target value correction flag. Thereafter, the process proceeds to step S213.

(Step S213) The water supply flow rate target determination unit 32 sets the water supply flow rate target value Qp ^SV to the water supply flow rate target value correction value Qp ^SVC (Qp ^SV = Qp ^SVC ).

  As shown in steps S204 and S206, the control device 30 compares the water level of the discharge water tank 3 measured by the discharge water tank water level meter 22 with the upper limit water level or the lower limit water level, and corrects the water supply flow rate target value according to the comparison result. . Thereby, the water level of the discharge water tank 3 can be prevented from exceeding the upper limit water level, so that it is possible to prevent water from overflowing from the discharge water tank 3 and to prevent excessive water supply. Alternatively, it is possible not to fall below the lower limit water level, and since water is always held in the discharge water tank 3 by a certain amount or more, it is possible to always discharge water from the discharge water tank 3 and to supply water from the discharge water tank 3. Stability can be improved.

As shown in steps S209 and S210, control device 30 compares the water supply pressure measured by manometer 17 with the upper limit pressure or the lower limit pressure, and corrects the water supply flow rate target value Qp ^SV according to the comparison result. Thereby, the water supply pressure can be prevented from exceeding the upper limit pressure, and the discharge pipe 8 can be prevented from being damaged because excessive pressure is not applied to the discharge pipe 8. Alternatively, the pressure can be kept below the lower limit pressure and the pressure enough to supply the water to the discharge water tank 3 can be maintained, so that the stability of the supply of water from the discharge water tank 3 can be improved.

  Next, an outline of a process of reducing the water level of the discharge water tank 3 while maintaining the water supply flow rate by the discharge water tank water level reduction control will be described with reference to FIG. FIG. 7 is an example of a graph showing the relationship between the head water supply flow rate and a graph showing the relationship between the shaft power and the water supply flow rate. As shown in the graph of the head flow rate in FIG. 7, when the rotation speed of the pump 2 is reduced by the first set amount from the coordinates C1 indicating the set of the water supply flow rate and the head, the discharge water tank 3 The water level drops and the head drops. At this time, since the water supply flow rate also decreases because the rotation speed of the pump 2 is reduced, the coordinates indicating the set of the current water supply flow rate and the total head move as shown by an arrow A11. As the time elapses (if there is no fluctuation in the demand water amount), the total head is also reduced by the decrease of the water supply flow rate, and the flow rate returns to the original flow rate as shown by arrow A12. Similarly, when the rotation speed of the pump 2 is reduced by the first set amount, the coordinates indicating the set of the current water supply flow rate and the head move as shown by an arrow A13, and as shown by an arrow A14 over time. Flow returns to the original flow rate. Hereinafter, similarly, the coordinates move in the order of arrow A15, arrow A16, arrow A17, arrow A18, arrow A19, arrow A20, arrow A21, and arrow A22. Thereby, it is possible to move from the position of the coordinate C1 to the position of the coordinate C2 while maintaining the same water supply flow rate, and it is possible to lower the head while maintaining the water supply flow rate.

  As shown in the graph showing the relationship between the driving force and the flow rate in FIG. 7, when the total head of the pump 2 is reduced even at the same water supply flow rate, the pump shaft power is reduced, so that the power consumption of the pump can be suppressed and the operating cost can be reduced. it can.

  Subsequently, the details of the discharge water tank water level reduction control in step S103 in FIG. 4 will be described with reference to FIG. FIG. 8 is a flowchart illustrating an example of a process of the discharge water tank water level reduction control.

  (Step S301) First, the discharge water tank water level reduction control unit 33 performs control to temporarily stop the constant flow rate control. Specifically, the discharge water tank water level reduction control unit 33 outputs a constant flow control suspension signal to the flow control unit 34. Here, the constant flow control suspension signal is a signal for instructing temporary suspension of the constant flow control. Thereby, the flow control unit 34 temporarily stops the constant flow control.

(Step S302) Next, the discharge water tank water level reduction control unit 33 refers to the storage unit 31 and
Obtaining the allowable maximum rotational speed Np ^QMAX and the allowable minimum rotation speed Np ^QMIX corresponding to the current pump flow. Then, the discharge water tank water level reduction control unit 33 determines whether or not the rotation speed Np of the pump is ^{equal to} or less than the allowable maximum rotation speed Np ^QMAX and the rotation speed Np is equal to or more than the allowable minimum rotation speed Np ^QMIN + the first set amount ΔNd. I do. Here, FIG. 9 is a diagram for explaining an appropriate operating range (operating point) of the pump. As shown in FIG. 9, an appropriate operation range A1 of the pump is set. The appropriate operating range A1 of the pump is an operating range in which no pump problems such as cavitation, pump vibration, and horsepower excess occur. Outside of the appropriate operation range A1, water may not be supplied even when operated, or irregular operating conditions such as cavitation, vibration of a pump, and excess horsepower may be obtained. For example, when the water supply flow rate Q is Q1, the rotation speed Np is not less than N1 and not more than N2 (N1 ≦ Np ≦ N2) is an appropriate operation range. In this example, when the water supply flow rate Q is Q1, the allowable maximum rotation speed Np ^QMAX is N1 and the allowable maximum rotation speed Np ^QMAX is N2. When the water supply flow rate Q is Q2, the rotation speed Np is equal to or more than N3 and equal to or less than Nmax (N3 ≦ Np ≦ Nmax). Here, Nmax is the maximum number of rotations of the motors 15-1 to 15-3. In this example, when the water supply flow rate Q is Q2, the allowable maximum rotation speed Np ^QMAX is N3, and the allowable maximum rotation speed Np ^QMAX is Nmax. As described above, the allowable maximum rotational speed Np ^QMAX and the allowable minimum rotational speed Np ^QMIX change depending on the water supply flow rate Q. For this reason, the allowable maximum rotation speed Np ^QMAX is specified for each pump flow rate in the table T1, and the allowable minimum rotation speed Np ^QMIX is specified for each pump flow rate in the table T2.

(Step S303) Next, when the rotation speed Np in step S302 exceeds the allowable maximum revolution speed Np ^QMAX, discharge water tank water level reduction control unit 33 sets the rotational speed target value Np ^SV to the allowable maximum revolution speed Np ^QMAX. Alternatively, when the rotation speed Np is lower than the allowable minimum rotation speed Np ^QMIN , the discharge water tank water level reduction control unit 33 sets the rotation speed target value Np ^SV to the allowable minimum rotation speed Np ^QMIN + the first set amount ΔNd. The discharge water tank water level reduction control unit 33 outputs a rotation speed target signal indicating the rotation speed target value Np ^SV to the speed control circuit 35. As a result, the speed control circuit 35 sets the rotation speed target value Np ^SV as the rotation speed command value and outputs the rotation speed command value to the corresponding motor control units 36-1, 36-2, 36-3. I do. Therefore, the motors 15-1, 15-2, and 15-3 are driven at the rotation speed of the rotation speed target value Np ^SV .

(Step S304) If the rotation speed Np is equal to or less than the allowable maximum rotation speed Np ^QMAX + the first set amount ΔNd and the rotation speed Np is ^{equal to} or higher than the allowable minimum rotation speed Np ^{QMIN in} step S302, the discharge water tank water level reduction control unit 33 , The motor 15 is controlled so as to reduce the rotation speed of the pump 2 by the first set amount ΔNd.

  (Step S305) Then, the discharge water tank water level reduction control unit 33 controls the motor 15 to maintain the rotation speed reduced in step S303. As a result, the water level of the discharge water tank 3 decreases over time.

  (Step S306) If the predetermined time has elapsed, the process proceeds to step S307.

(Step S307) The discharge water tank water level reduction control unit 33 determines whether or not the water supply flow rate Qp has returned to the water supply flow rate target value Qp ^SV .

(Step S308) If the result of determination in step S307, or if the water flow rate Qp is returned to the water supply flow rate target value Qp ^SV, discharge water tank water level reduction control unit 33, the discharge water tank water level L _T has reached the lower limit level L _T ^L Determine whether or not. If the discharge water tank water level L _T does not reach the lower limit level L _T ^L (i.e. when the discharge water tank water level L _T is larger than the lower limit level L _T ^L), the process returns to step S302. By returning to step S302 in this manner, the discharge water tank water level reduction control unit 33 controls the motor 15 to further reduce and maintain the rotation speed of the pump 2 by the first set amount ΔNd.

On the other hand, if the discharge water tank water level L _T has reached the lower limit level L _T ^L, in step S312, the discharge water tank water level reduction control unit 33 maintains the rotation speed is controlled so as to return to the constant flow rate control. Specifically, the discharge water tank water level reduction control unit 33 outputs a constant flow control return signal to the flow control unit 34 and the speed control circuit 35. Here, the constant flow control return signal is a signal for instructing a return to constant flow control. Thereby, the flow control unit 34 restarts the constant flow control.

(Step S309) When the water supply flow rate Qp returns to the water supply flow rate target value Qp ^SV in step S307, the discharge water tank water level reduction control unit 33 executes the pump 2-2 acquired from the tachometer 18-1 in parallel with step S308. rotation number Np1 of the motor 15-1 obtained from the first rotational speed Np1 or tachometer 19-1 determines whether below the lower limit rotational speed Np ^MIN motor 15-1 can generate torque. If the motor 15-1 is below the lower limit rotational speed Np ^MIN capable of generating torque, the discharge water tank water level reduction control unit 33 controls so as to return to the constant flow rate control. Specifically, the discharge water tank water level reduction control unit 33 outputs a constant flow control return signal to the flow control unit 34 and the speed control circuit 35. Thereby, the flow control unit 34 restarts the constant flow control. On the other hand, if not less than the lower limit rotation speed Np ^MIN motor 15-1 can generate a torque, the process returns to step S302. Thereby, the discharge water tank water level reduction control unit 33 controls the motor 15 so as to further reduce and maintain the rotation speed of the motor 15 by the first set amount ΔNd.

(Step S313) On the other hand, if the water supply flow rate Qp does not return (recover) to the water supply flow rate target value Qp ^SV as a result of the determination in step S307, the discharge water tank water level reduction control unit 33 sets the rotation speed of the pump 2 to the second. The motor 15 is controlled to increase by the set amount ΔNu.

  (Step S314) Then, the discharge water tank water level reduction control unit 33 controls the motor 15 so as to maintain the increased rotation speed.

(Step S315) If the predetermined time has elapsed, the process returns to step S307. By returning to step S307 in this manner, the discharge water tank water level reduction control unit 33 adjusts the water supply flow rate Qp to a target water supply flow rate Qp after a predetermined time has elapsed since the motor 15 was controlled to increase and maintain the second set amount ΔNu. It is determined whether the value has returned to the value Qp ^SV (that is, the water flow rate Qp is equal to the water flow target value Qp ^SV ) (see step S307). When the water supply flow rate Qp returns to the water supply flow rate target value Qp ^SV as a result of the determination, the discharge water tank water level reduction control unit 33 reduces the motor 15 so as to maintain the rotation speed of the pump 2 reduced by the first set amount ΔNd. Is controlled (see steps S304 and S305). On the other hand, when the water supply flow rate Qp has not returned to the water supply flow rate target value Qp ^SV , the discharge water tank water level reduction control unit 33 controls the motor 15 to further increase and maintain the rotation speed of the pump 2 by the second set amount ΔNu. Control (see steps S313 and 314).

With this configuration, if the water supply flow rate Qp has not returned to the water supply flow rate target value Qp ^SV after the rotation speed of the pump 2 is once increased by the second set amount ΔNu, the rotation speed of the pump 2 is increased. Therefore, the water supply flow rate Qp can be increased so as to be closer to the water supply flow rate target value Qp ^SV . Thereby, the water supply flow rate Qp can be made closer to the water supply flow rate target value Qp ^SV , so that the stability of water supply to the discharge water tank 3 can be improved. On the other hand, if the water supply flow rate Qp has returned to the water supply flow rate target value Qp ^SV after increasing the rotation number of the pump 2 by the second set amount ΔNu, the rotation number of the pump 2 can be reduced. As a result, the water level of the discharge water tank is lowered and the head is lowered, so that the power consumption of the pump can be suppressed and the operating cost can be reduced.

As described above, as shown in steps S304 to S307, the control device 30 controls the motor 15 so that the rotation speed of the pump 2 is reduced and maintained by the first set amount ΔNd. water flow rate target value whether the determined return to Qp ^SV, the result of the determination, if the water flow rate Qp is returned to the water supply flow rate target value Qp ^SV, further reducing the rotational speed of the pump 2 by a first set amount ΔNd The motor 15 is controlled to maintain it.

With this configuration, when the water supply flow rate Qp returns to the water supply flow rate target value Qp ^SV , the rotation speed of the pump 2 can be reduced. As a result, the water level of the discharge water tank is lowered and the head is lowered, so that the power consumption of the pump can be suppressed and the operating cost can be reduced.

  Further, the control device 30 repeats the control for controlling the motor 15 so as to maintain the rotation speed of the pump 2 reduced by the first set amount ΔNd until the water level of the discharge water tank 3 reaches the lower limit water level.

  With this configuration, the discharge water tank water level drops to the lower limit water level and the head drops to the limit, so that the power consumption of the pump can be further suppressed and the operating cost can be further reduced.

Further, as shown in steps 313 to 314, when the water supply flow rate Qp does not return to the water supply flow rate target value Qp ^SV as a result of the above determination, the control device 30 increases the rotation speed of the pump 2 by the second set amount ΔNu. The motor 15 is controlled so as to maintain it.

With this configuration, when the water supply flow rate Qp does not return to the water supply flow rate target value Qp ^SV , the rotation speed of the pump 2 can be increased, so that the water supply flow rate can be prevented from becoming insufficient. In this way, it is possible to prevent shortage of water in the discharge water tank 3 and to improve the stability of water supply from the discharge water tank 3.

Further, as shown in step S302, the control device 30 reads the allowable maximum rotation speed and the allowable minimum rotation speed corresponding to the water supply flow rate target value Qp ^SV from the storage unit 31, and determines that the current rotation speed of the pump 2 is the allowable minimum rotation speed. It is determined whether the rotation speed is equal to or higher than the rotation speed (in the present embodiment, as an example, the allowable minimum rotation speed Np ^QMIN + the first set amount ΔNd) and equal to or lower than the allowable maximum rotation speed. Then, when the current rotation speed of the pump 2 becomes a rotation speed corresponding to the allowable minimum rotation speed, the control device 30 performs control to maintain the rotation speed so as not to fall below the allowable minimum rotation speed. When the rotation speed of the motor reaches the maximum allowable rotation speed, the rotation speed is maintained so as not to exceed the maximum allowable rotation speed.

  With this configuration, it is possible to prevent the pump speed from deviating from an appropriate operation range. For this reason, it is possible to prevent that water cannot be supplied even during operation, and that irregular operation conditions such as cavitation, vibration of the pump, and excess horsepower are provided.

  Further, as shown in step S308, the control device 30 determines whether or not the water level of the discharge water tank 3 measured by the discharge water tank water level meter 22 has reached the lower limit water level, and the water level of the discharge water tank 3 has reached the lower limit water level. In this case, the rotation speed is maintained so as not to be further reduced, and the flow returns to the constant flow rate control as shown in step S312 (see step S104).

  With this configuration, it is possible to prevent the water from being discharged from the discharge water tank so as not to fall below the lower limit water level, and to operate the head in the discharge water tank 3 with an appropriate water level and with the lowest possible power consumption. Of water supply from the fuel cell can be improved.

  Further, as shown in step S309, the control device 30 determines whether or not the rotation speed of the pump 2 measured by the tachometer 18 or 19 is lower than a lower limit rotation speed at which the motor 15 can generate torque. If the number of revolutions is less than the lower limit number of revolutions, the number of revolutions is maintained so as not to decrease any more, and the flow returns to the constant flow rate control as shown in step S312.

  With this configuration, it is possible to prevent the water from being discharged from the pump 2 and prevent the water level in the discharge water tank 3 from dropping. Thereby, it is possible to avoid a situation in which water is not discharged from the discharge water tank 3, and it is possible to improve the stability of water supply from the discharge water tank 3.

  In the present embodiment, in step S302, it is determined whether the rotation speed of the pump 2 is in an appropriate range. However, the present invention is not limited to this, and it may be determined whether the rotation speed of the motor 15 is in an appropriate range.

  As described above, the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements in an implementation stage without departing from the scope of the invention. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the above embodiments. For example, some components may be deleted from all the components shown in the embodiment. Further, constituent elements of different embodiments may be appropriately combined.

  S: pump system, 1: suction water tank, 2-1 2-2, 2-3: pump, 3: discharge water tank, 5: suction pipe, 6-1, 6-2, 6-3: branch suction pipe, 7-1, 7-2, 7-3: branch discharge pipe, 8: discharge pipe, 9-1, 9-2, 9-3: check valve, 10: water stop valve, 11-1, 11-2 , 11-3: water stop valve, 12-1, 12-2, 12-3: discharge valve, 13-1, 13-2, 13-3: water stop valve, 15-1, 15-2, 15-. 3: Motor, 17: Pressure gauge, 18-1, 18-2, 18-3: Tachometer, 19-1, 19-2, 19-3: Tachometer, 20: Water flow meter, 21: Suction Water tank water level meter, 22: discharge water tank water level meter, 23: water intake flow meter, 24: water intake valve, 25: demand water flow meter, 26: demand water outflow valve, 30: control device, 31: storage unit, 32: water supply flow rate Goal determination , 33: discharge water tank water level reduction control unit, 34: flow rate control unit, 35-1: count control unit, 35-2: speed control circuit, 36-1,36-2,36-3: motor control unit

Claims (12)

At least one motor,
At least one pump driven by the motor and sucking water from a suction tank;
A water flow meter that measures a water flow rate, which is a flow rate of water sent to a discharge water tank from which water pumped by the pump is discharged,
A demand water flow meter that measures a demand water amount that is a natural flow outflow amount from the discharge water tank,
A control device for controlling the motor,
With
The control device controls the motor to reduce and maintain the number of rotations of the pump by a first set amount, and after a lapse of a predetermined time, the water supply flow rate is a demand water flow rate provided on the discharge side of the discharge water tank. the water flow rate using a demand water flow rate signal obtained from the total is determined whether or not return to the set water flow rate target value to match the demand water flow rate, the result of the determination, the water flow rate is the water flow rate target The pump system further comprising: controlling the motor so that the rotation speed of the pump is reduced and maintained by a first set amount when the value is returned to the value. Further provided with a discharge water tank water level meter for measuring the water level of the discharge water tank,
The pump according to claim 1, wherein the control device repeats control for controlling the motor to reduce and maintain the rotation speed of the pump by the first set amount until the water level of the discharge water tank reaches the lower limit water level. system. The control device controls the motor to increase and maintain the rotation speed of the pump by a second set amount when the water supply flow rate does not return to the water supply flow rate target value as a result of the determination. A pump system according to claim 1. After a lapse of a predetermined time from the time when the motor is controlled to be increased and maintained by the second set amount, it is determined whether or not the water supply flow rate has returned to the water supply flow rate target value. When the flow rate returns to the target flow rate, the motor is controlled to maintain the rotation speed of the pump reduced by the first set amount, and when the water supply flow rate does not return to the water supply flow target value, the rotation speed of the pump is further increased. The pump system according to claim 3, wherein the motor is controlled so as to increase and maintain the motor speed by a second set amount. Before SL controller pump system claimed in any one of 4 to control the rotational speed of the pump so that the water flow rate to match the water demand. A storage unit in which a flow rate of water discharged by the pump and an allowable maximum rotation speed of the pump are associated and stored, and a flow rate of water discharged by the pump and an allowable minimum rotation speed of the pump are stored in association with each other. Prepared,
The control device reads an allowable maximum rotation speed and an allowable minimum rotation speed corresponding to the water supply flow rate target value from the storage unit, and the current rotation speed of the pump is equal to or more than the rotation speed according to the allowable minimum rotation speed and the allowable rotation speed. It is determined whether or not the rotation speed is equal to or less than a maximum rotation speed. When the current rotation speed of the pump becomes a rotation speed according to the allowable minimum rotation speed, control for maintaining the rotation speed so as not to fall below the allowable minimum rotation speed. When the current rotation speed of the pump reaches the maximum allowable rotation speed, the rotation speed is maintained so as not to exceed the maximum allowable rotation speed.
The pump system according to claim 1. Further provided with a discharge water tank water level meter for measuring the water level of the discharge water tank,
The control device determines whether or not the water level of the discharge water tank measured by the discharge water tank water level meter has reached a lower limit water level.If the water level of the discharge water tank has reached the lower limit water level, the rotation speed is further reduced. A pump system according to any one of the preceding claims. Further provided with a discharge water tank water level meter for measuring the water level of the discharge water tank,
The said control apparatus compares the water level of the said discharge water tank measured by the said discharge water tank water level meter with an upper limit water level or a lower limit water level, and corrects the water supply flow rate target value according to the comparison result. A pump system according to claim 1. Further comprising a pressure gauge that measures a water supply pressure that is a pressure of water sent to the discharge water tank,
The said control apparatus compares the said water supply pressure measured by the said pressure gauge with an upper limit pressure or a lower limit pressure, and corrects the said water supply flow rate target value according to a comparison result. Pump system. A suction tank,
At least one motor,
At least one pump driven by the motor and sucking water from the suction tank;
A discharge water tank from which water pumped by the pump is discharged,
A water supply flow meter that measures a water supply flow rate that is a flow rate of water sent to the discharge water tank,
A demand water flow meter that measures a demand water amount that is a natural flow outflow amount from the discharge water tank,
A control device for controlling the motor,
With
The control device controls the motor to reduce and maintain the number of rotations of the pump by a first set amount, and after a lapse of a predetermined time, the water supply flow rate is a demand water flow rate provided on the discharge side of the discharge water tank. the water flow rate using a demand water flow rate signal obtained from the total is determined whether or not return to the set water flow rate target value to match the demand water flow rate, the result of the determination, the water flow rate is the water flow rate target The pump system further comprising: controlling the motor so that the rotation speed of the pump is reduced and maintained by a first set amount when the value is returned to the value. A control device that controls a motor that drives a pump,
A motor control unit that controls the motor to reduce and maintain the rotation speed of the pump by a first set amount;
After a lapse of a predetermined time from the time when the motor is controlled to be reduced and maintained by the first set amount, the flow rate of water sent to the discharge water tank is determined by a demand obtained from a demand water flow meter provided on the discharge side of the discharge water tank. A discharge water tank water level reduction control unit that determines whether or not the water supply flow rate has returned to the water supply flow rate target value set to match the demand water flow rate using a water flow rate signal ;
With
Result of the determination, if the water flow rate by the discharge water tank water level reduction control unit is determined to be returned to the water flow rate target value, the motor control unit maintains reduced by further predetermined amount the number of revolutions of the pump A control device for controlling the motor as described above. A control method for controlling a motor that drives a pump,
Controlling the motor to maintain the pump speed reduced by a first set amount;
After a lapse of a predetermined time from the time when the motor is controlled to be reduced and maintained by the first set amount, the flow rate of water sent to the discharge water tank is determined by a demand obtained from a demand water flow meter provided on the discharge side of the discharge water tank. Determining whether or not the water flow rate has returned to the water flow rate target value set to match the demand water flow rate using a water flow rate signal ;
Result of the determination, if the water flow rate in the determining step is determined to have returned to the water flow rate target value, and controlling the motor so as to maintain reduced by further predetermined amount the number of revolutions of the pump,
A control method having:

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