JP5159187B2 - Variable speed water supply device - Google Patents

Description

  The present invention relates to a variable speed water supply apparatus, and more particularly to a variable speed water supply apparatus that operates a plurality of pumps that are driven at a variable speed in parallel.

  A water supply device is installed in an apartment house or a building and supplies water to each water supply end. FIG. 1 shows a typical example of such a water supply apparatus. The water supply apparatus includes two motor pumps 1 and an inverter (frequency converter) 2 for supplying electric power for driving the two motor pumps 1. I have. The water supply device includes a pressure tank 3 and a discharge-side pressure sensor 4 on the discharge side of the pump 1, and a flow switch (flow rate detection means) 6 and a check valve 7 for each pump. A suction side pipe 8 of the pump is connected to a water main pipe 9, and a suction side pressure sensor 10 and a backflow prevention device 11 are provided in the suction side pipe 8. Further, a bypass pipe 12 for supplying water only with the pressure of the water main pipe is provided between the suction side pipe 8 and the discharge side pipe 13 of the pump 1. A check valve 14 is provided in the middle of the bypass pipe 12. The control device 15 that controls the motor pump 1 performs the rotational speed control and the number control of the pump 1 according to the situation based on signals from these sensors.

  In addition, if the suction side pipe of the pump is not a direct connection type water supply device connected to the water main, but a water receiving tank type water supply device, the pump suction side piping is connected to the water receiving tank and provided in the water receiving tank. A water level detector is connected to the controller. Moreover, a backflow prevention device, a suction side pressure sensor, and a bypass pipe are not provided.

  FIG. 2 is a QH diagram when performing such constant control of the estimated terminal pressure of the water supply apparatus, the horizontal axis indicates the flow rate Q, and the vertical axis indicates the pressure (head) H. The minimum required pressure PB of the water supply system and the required pressure PA at the maximum demand water volume are connected by a resistance curve R of the pipe line depending on the flow rate, and the pressure indicated by the resistance curve R at each flow rate is the target pressure to be supplied by the water supply device It becomes. The minimum required pressure PB of the water supply system and the required pressure PA at the maximum demand water amount are previously set and stored in the control device 15 by the setting means. The control device 15 issues a rotational speed command to the inverter 2 between the pump rotational speed HzB at which the pressure becomes PB in the closed state and the pump maximum rotational speed HzMax, but estimates the flow rate from the current pump rotational speed command value. The target pressure at that time is determined, and a rotation speed command is issued to the inverter 2 so that the pressure detected by the discharge-side pressure sensor 4 matches the target pressure.

  In the water supply apparatus configured as described above, when water is used on the demand side while the pump is stopped and the detected pressure of the discharge-side pressure sensor 4 falls below the starting pressure (minimum required pressure) PB, the control device 15 causes the pump 1 Activate one. In this case, the pump 1 is operated at a pump speed HzB. When the demand water volume increases, the pump 1 increases the rotation speed from the pump rotation speed HzB to Hz1, Hz2,..., But when the flow rate exceeds Q1, the pump rotation speed reaches the maximum rotation speed HzMax. As a result, the target pressure cannot be satisfied. Therefore, when the pump rotation speed command reaches the maximum rotation speed HzMax, another pump is started. At this time, the pump that was started first (the first pump) is fixed at a predetermined speed HzMax ′ whose operating speed is slightly lower than the maximum speed HzMax, and becomes a fixed speed pump. It becomes a variable speed pump that is controlled at variable speed according to the amount of demand water, and satisfies the target pressure. The fixed speed pump is operated at a predetermined number of revolutions determined in advance, regardless of fluctuations in the discharge pressure.

If the demand water volume decreases while two pumps are operating, the number of revolutions of the later pump will be reduced. However, if the water volume is Q1 or less, the demand can be met with one pump. Stop. The control device 15 detects that the amount of water supplied from the subsequent pump is small by the flow switch 6 of the subsequent pump, stops the subsequent pump from being disconnected, and controls the preceding pump again at a variable speed.
When the demand water volume further decreases, the rotational speed of the starter pump is lowered, but when the flow switch 6 of the starter pump detects that the amount of water is small, the control device 15 also stops the starter pump and uses the water again. The standby state is maintained until the detected pressure of the discharge side pressure sensor 4 becomes equal to or lower than the starting pressure (minimum required pressure) PB.

  Moreover, when the water supply apparatus is a direct connection type water supply apparatus, the pressure of the water main pipe is applied to the pump suction side, and the pressure also fluctuates. When the suction pressure increases, the same pressure and flow rate can be covered at a lower pump rotation speed, so the relationship between PB and HzB described above changes. For this reason, the relationship between the target pressure and the pump rotation speed command is appropriately corrected according to the suction pressure, and appropriate estimated terminal pressure constant control is performed. If the suction pressure is further increased and exceeds the target pressure, water can be supplied without driving the pump, so the control device 15 stops the pump. When the suction pressure decreases and falls below the target pressure, the pump is driven again.

JP-A-9-268978 JP 2003-21069 A Japanese Patent Laid-Open No. 5-118280

  When the starter pump is in operation and the pump is additionally started, the control device continuously checks that the starter pump has reached the maximum speed and that the starter pump has water for a certain period of time by means of a flow switch. It is determined that the flow rate is equal to or higher than Q1, and it is necessary to add a later pump. The amount of water in the starting pump is checked to separately detect an abnormal condition in which there is no pressure or amount of water, even though the pump is rotating due to air contamination, etc. Is also used.

  On the other hand, an inverter that drives a motor, particularly an inverter that drives a DC brushless motor, has a current limiting function, and when the motor load is large, the current is reduced at a rotational speed lower than the frequency command value from the control device. Is controlled so as not to exceed the set value. As shown in FIG. 3, when the rotational speed is increased up to the maximum rotational frequency HzMax, the operating point on the performance curve of HzMax cannot be taken in the high flow rate region depending on the load condition. The operation is performed at the operating point at which the rotational speed is reduced as shown. For example, when the current limiting function is activated and the inverter reduces the rotation speed to Hz4, the operation is performed at the intersection point a, and as a result, the flow rate becomes Q1 '.

In such a water supply device, there are some problems as listed below.
(1) In the situation where the current limiting function is working, even if the rotational speed command value is increased, the actual pump drive frequency is lowered. Therefore, until the rotational speed command value increases to the maximum rotational speed and a subsequent pump is added. During this period, the demand cannot be satisfied.
(2) If a pump is added while the current limiting function is working, the load on the starting pump is reduced and the current limiting function is released, so the starting pump is suddenly driven at the rotational speed command value. Causes fluctuations.
(3) If the detection state of a small amount of water is accidentally continued due to a malfunction of the flow rate detection means such as a flow switch failure, a subsequent pump will not be added and the demand water amount cannot be met. There is a fear.
(4) If the load on the motor of the first pump becomes extremely heavy due to contamination of foreign matter, etc., the rotation speed command of the pump will be the maximum rotation speed, but since the actual water volume is small, a small amount of water will be detected. There is a possibility that the demand water volume cannot be satisfied without additional pump activation.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a variable speed water supply apparatus that includes a plurality of motor pumps that are driven at a variable speed and that can perform a stable additional operation with little pressure fluctuation. And
In addition, the present invention determines whether the capacity of the pump being operated is insufficient even when the flow detection means such as the flow switch does not operate normally or when the flow switch is not provided. It aims at providing the variable speed water supply apparatus which can be performed.

In order to achieve the above-described object, one aspect of the present invention includes a plurality of pumps, a plurality of frequency converters each having a current limiting function for shifting the pumps, a discharge-side pressure sensor, and these devices. A variable speed water supply apparatus that controls a plurality of pumps in parallel, wherein the control apparatus controls the variable speed pump so that the pressure detected by the discharge side pressure sensor matches a target pressure. while operating in a state in which the current limiting function works by the frequency converter for driving the speed pump, and, when the detected pressure of the discharge-side pressure sensor is in the following states target pressure, the frequency for driving the speed pump It is characterized in that it is determined that the output current value of the converter is equal to or higher than a preset limit current value, and the additional pump is started.

  A preferred aspect of the present invention further includes a flow rate detecting means provided for each of a plurality of pumps, wherein the control device has a frequency command value for the speed change pump of the maximum rotation speed, and the flow rate detecting means. The additional pump is also started when a state where the amount of water is not small is detected for a predetermined time.

  In a preferred aspect of the present invention, after the additional pump is started, the control device operates at a variable speed so that the detected pressure of the discharge-side pressure sensor coincides with a target pressure using the additional pump as a speed change pump. The previously operated pump is operated as a fixed speed pump at a speed equal to or lower than the additional operation frequency.

According to the present invention, a plurality of variable speed driven motor pumps are provided, and a stable additional operation with little pressure fluctuation can be performed.
More specifically, the following effects are obtained.
(1) According to the present invention, when a deviation occurs between the frequency command value and the actual operating frequency due to the current limiting function of the frequency converter (that is, when the operating pump cannot cover the load) In addition, since the additional pump is started quickly, it is possible to perform control that is sensitive to an increase in the amount of demand water.
(2) According to the present invention, even when the flow rate detecting means such as the flow switch does not operate normally, or even when the flow switch is not provided, it is determined whether the capacity of the operating pump is insufficient, Can be added.
(3) According to the present invention, even when the load is increased due to foreign matters mixed in the pump and the rotation speed is difficult to increase, the DC brushless motor increases the current until the current limiting function is activated. At least a pump can be added.

[First Embodiment]
FIG. 4 is a diagram showing an embodiment of the variable speed water supply apparatus of the present invention. Since the configuration of the variable speed water supply apparatus of the present invention is the same as that of the variable speed water supply apparatus shown in FIG. 1, FIG. 4 is a diagram illustrating a control apparatus in detail by extracting a part of FIG. 1. In the present invention, each motor M that drives the pump 1 is a DC brushless motor. The control device 15 includes a setting unit 16, a storage unit 17, a calculation unit 18, a display unit 19, an I / O unit 20, and the like. In the setting unit 16, the minimum required pressure PB of the water supply system, the required pressure PA at the maximum demand water amount, a stall level that is a threshold at which the inverter 2 operates the current limiting function, and the like are set by an external operation. Various setting values set in the setting unit 16 are stored in the storage unit 17. The I / O unit 20 receives signals from various sensors in the water supply device, such as the output of the discharge side pressure sensor 4 and the signal of the flow switch 6, and sends them to the calculation unit 18. Further, the I / O unit 20 and each inverter 2 are connected by communication means such as RS485, and various setting values such as a stall level setting value, a frequency command value, and an on / off signal (from the control device 15 to the inverter 2). A control signal such as a start / stop signal) is sent, and the operating status such as the actual frequency value and current value is sequentially sent from the inverter 2 to the control device 15.

  The calculation unit 18 sequentially determines the start / stop (start / stop) of each inverter 2 and calculates the frequency command value based on signals from sensors such as the discharge side pressure sensor 4, the suction side pressure sensor 10 and the flow switch 6. And sends a command to each inverter 2 via the I / O unit 20.

  FIG. 5 is a flowchart of the estimated terminal pressure constant control of such a water supply apparatus. First, the control device 15 takes in the detection pressure of the discharge side pressure sensor 4 and takes in the detection pressure of the suction side pressure sensor 10. Next, at the suction pressure at that time, the pump rotation speed HzB that is the minimum required pressure PB of the water supply system in the closed state is calculated. The control device 15 stores the relationship among the suction pressure, the pump cutoff pressure, and the pump rotation speed as table data or a function, and calculates the pump rotation speed HzB using this relationship. Further, the maximum operating frequency (maximum pump speed) HzMax at the suction pressure at that time is calculated. This maximum operating frequency HzMax is the rotational speed that is the pressure when the cutoff operation is performed at the suction pressure at that time and the cutoff operation is performed at the maximum rotational speed of the pump when the suction pressure is zero. The above-described maximum operating frequency HzMax at the suction pressure at that time is also calculated using the table data or function indicating the relationship between the suction pressure, the pump cutoff pressure, and the rotation speed stored in the control device 15.

  Next, the control device 15 calculates a target pressure for the estimated terminal pressure constant control based on the calculated HzB and the current frequency command value. Then, the calculated target pressure is compared with the current discharge pressure to calculate the frequency command value of the pump that is operating at a variable speed by PI calculation. If this frequency command value is smaller than HzB, the frequency command value is calculated. If it is larger, the calculated value is directly used as the frequency command value.

  Next, it is confirmed whether or not two or more pumps are operating in parallel, and if they are operating in parallel, the frequency command of the first pump that is operating as a fixed speed pump is used as a frequency command of 95% of HzMax calculated above. Is specified. After that, it is confirmed whether or not this frequency command value does not fall below HzB as well as the above-mentioned variable speed pump. After that, this frequency command value is actually sent from the inverter 2 to the first pump when the second pump is added. If it exceeds the operating frequency (additional operation frequency), and if it exceeds, the frequency command value of the starting pump is set as the additional operation frequency. Here, 95% of HzMax is used, but as long as the frequency is lower than HzMax, a frequency obtained by multiplying HzMax by a predetermined ratio (not limited to 95%) or a frequency obtained by subtracting a predetermined value from HzMax may be used. Finally, it is confirmed whether or not the frequency command value does not fall below the frequency of HzB + α (a frequency value set slightly higher than HzB). If it is lower, the frequency command value of the starting pump is set to this HzB + α. . Here, HzB + α is used to make the operation more stable by keeping the operation frequency of the fixed speed pump higher than the operation frequency of the transmission pump.

  As described above, the frequency command value of the pump being operated is determined, and the control device 15 transmits each frequency command value to each inverter 2. Since HzMax varies depending on the suction pressure, the starting pump actually changes its operating frequency in accordance with the variation of the suction pressure, although it is a fixed speed pump. In other words, the fixed-speed pump here is a pump that has no relation to the comparison calculation between the discharge pressure and the target pressure, and changes the operating frequency only in response to fluctuations in the suction pressure. Due to this change in the operating frequency, the cutoff pressure at that frequency becomes constant regardless of the fluctuation of the suction pressure, that is, the performance curve of the starting pump becomes constant regardless of the suction pressure. The calculation of the target pressure is stable.

  In the case of a water tank-type water supply device, the suction pressure is not taken into the control device 15 and there is no fluctuation in the suction pressure, so there is no need to calculate HzB or HzMax sequentially, and HzB is a target pressure setting. What is necessary is just to calculate and memorize | store at time etc., and to set and memorize | store HzMax by external operation. Others are the same as the control described above.

  FIG. 6 is a flowchart of the control when it is necessary to additionally start another pump without performing the operation of one pump to cover the amount of demand water when performing such pressure control. . The additional control of the pump according to the present embodiment is parallel of two determination conditions.

  First, the first pump is operated at a variable speed, the rotational speed becomes the maximum rotational speed, and the state where the flow switch 6 of the pump does not detect a small amount of water (flow switch open) continues for a predetermined time. A pump is added when the additional condition of is satisfied. Under this additional condition, as described above, not only cannot the flow switch 6 be added when it fails, but if the current limiting function is activated, an extra pressure fluctuation occurs. Therefore, in the present embodiment, even if the pump is not added under the first additional condition, the current value of the starting pump (variable pump) that is sent from the inverter 2 and is operated at a variable speed is stored in the storage unit 17. A pump is also added when the second additional condition that the current limit value (stall level) is not less than the stored current pressure and the detected pressure of the discharge-side pressure sensor 4 is equal to or lower than the target pressure at that time is satisfied. In the second additional condition, without confirming whether the condition continues, a pump is added as soon as the two conditions are met, so control that responds sharply to an increase in demand water is possible become. Note that the discharge pressure and the target pressure are compared under the second additional condition, but the target pressure itself is not a predetermined pressure value based on the target pressure (for example, a pressure value obtained by multiplying the target pressure by 0.95). Or a pressure value slightly lower than the target pressure, such as a pressure value obtained by subtracting a predetermined value from the target pressure). In addition, the continuation of the condition may be added after confirming the continuation for a short time even in the second additional condition. Even in this case, the time is extremely short compared to the predetermined time for continuation in the first additional condition. (For example, about 0.5 seconds).

  The second additional condition can be determined regardless of the state of the flow switch 6, and the current limit function of the inverter 2 causes a difference between the frequency command value and the actual operation frequency (that is, the operation). When the flow switch 6 fails, the pump can be added and the extra pressure fluctuation associated with the current limiting function is suppressed. can do. In addition, even when the load is high and the rotational speed is difficult to increase due to foreign matter entering the pump, the DC brushless motor increases the current until the current limiting function works. be able to.

  In addition, when both the first and second additional conditions are satisfied, the actual operating frequency of the starting pump (transmission pump) at the time when the addition of the pump is determined is stored as the additional operating frequency. And in the determination process of the frequency command value of the fixed speed pump shown in FIG. 5, the frequency command value to the fixed speed pump is controlled so as not to exceed the operation frequency at the time of addition. As a result, even when a pump is added under the second additional condition, the rotational speed of the first pump whose load has been reduced by the operation of the subsequent pump does not suddenly increase to near the maximum rotational speed. Stable operation with suppressed is possible.

  The operation of the pump under this second additional condition will be described with reference to FIG. The upper diagram in FIG. 7 shows the flow rate of the water supply device on the horizontal axis and the discharge pressure on the vertical axis. The lower diagram in FIG. The current value of the pump is taken. The target pressure for the estimated terminal pressure constant control is given by a resistance curve R between the minimum required pressure PB of the feed water system and the required pressure PA at the maximum demand water volume, and the target pressure changes depending on the flow rate. In FIG. 7, the performance curves of the pump at HzMax and HzL are shown.

  As the flow rate of the water supply device increases, the number of rotations of the pump increases so as to satisfy the target pressure corresponding to the flow rate at that time, and the current value for driving the pump also increases. Then, when the flow rate increases to the flow rate L which is the intersection of the resistance curve R of the target pressure and the line indicated by the two-dot chain line s where the rotational speed is limited by the current limiting function by the inverter, the rotational speed of the pump becomes HzL, The current value of the pump drive reaches the current limit value. When the flow rate increases even a little from this state, the calculation unit 18 of the control device 15 outputs a frequency command value larger than HzL, but the output frequency of the inverter becomes a value smaller than the frequency command value by the current limiting function. At this time, since the current value of the pump is not less than the limit current value and the discharge pressure does not reach the target pressure, the second additional condition is satisfied and the pump is added.

  When the water amount decreases from the parallel operation state, as shown in FIG. 8, the transmission pump is in a low water state by the flow switch 6 of the transmission pump, and the discharge pressure detected by the discharge side pressure sensor 4 exceeds the target pressure. If the state that the discharge pressure exceeds the target pressure continues for a predetermined time, it is determined that the amount of demand water can be covered even if the added pump is stopped. Is stopped, and the fixed speed pump is used again as the transmission pump to perform the disconnection operation.

  Although omitted in FIG. 5, if the additional pump speeds up due to the increase in water volume during parallel operation and catches up with the number of revolutions of the starting pump, the fixed speed pump is also switched to the variable speed pump at a higher water volume. A uniform speed operation is performed by the two speed change pumps, and the two pumps are speed-changed based on the same frequency command value. In addition, in the case of a water supply apparatus having three pumps, a third pump was added to two pumps operated at a uniform speed, and the second pump was preceded if the same additional conditions as in FIG. 6 were satisfied. The control shown in FIG. 5 is performed with the pump as a fixed speed pump and the added third pump as a speed change pump, and when the speed change pump catches up with the rotation speed of the fixed speed pump, the control is performed with three speeds. Is possible. The same control is possible when four or more pumps are operated in parallel. Also, if the frequency command value decreases due to a decrease in the amount of water during uniform speed operation and falls below the frequency command value to be output to the fixed speed pump (HzMax x 0.95 or the lower operation frequency when added), the uniform speed operation will occur. Is released and the control returns to the control shown in FIG.

[Second Embodiment]
In the first embodiment described above, the first additional condition and the second additional condition are arranged in parallel, and if either one of the conditions is satisfied, the pump is added. However, in the second embodiment, Only two additional conditions were adopted, and the flow switch was not used when the pump was disconnected.

FIG. 9A is a flowchart for determining whether to add a pump, which is the same as the determination of the second additional condition in the first embodiment. That is, the current value of the starting pump (transmission pump) that is sent from the inverter 2 and is operated at a variable speed is equal to or greater than the current limit value (stall level) stored in the storage unit 17, and the discharge-side pressure sensor 4. When the condition that the detected pressure is equal to or lower than the target pressure at that time is satisfied, the actual operating frequency of the starting pump (transmission pump) is stored as the additional operating frequency, and the pump is additionally started.
FIG. 9B is a flowchart for determining the pump disengagement. The frequency command value to the transmission pump is HzB (minimum frequency), and the discharge pressure detected by the discharge-side pressure sensor 4 is the target pressure. It is confirmed whether or not the discharge pressure has exceeded the target pressure, and when the state where the discharge pressure has exceeded the target pressure has continued for a predetermined time, the speed change pump is stopped, and the fixed speed pump is returned to the speed change pump to continue the operation. .

  The comparison between the discharge pressure and the target pressure at the time of disconnection determination is performed by using a predetermined pressure value based on the target pressure without using the target pressure itself (for example, a pressure value obtained by multiplying the target pressure by 1.05 or a target pressure). A comparison may be made with a pressure value slightly higher than the target pressure, such as a pressure value to which a value is added.

  Further, in the present embodiment, considering the characteristics of the motor and pump used in the water supply device, the target pressure, the maximum demand water amount, etc., the intersection of the performance curve at the maximum rotation speed of the pump and the performance curve by the current limiting function Set the threshold (current limit value, stall level) for the current limit function to be higher than the target pressure, so that the pressure at which the current limit function starts to work at the maximum speed is higher than the target pressure. It is desirable to do.

FIG. 10 is a view similar to FIG. As shown in FIG. 10, if the pressure at which the current limiting function starts to work at the maximum number of revolutions is below the target pressure, the additional conditions of the pump are not satisfied unless the target pressure is once exceeded when the flow rate increases, and the pressure fluctuation It is because it will produce. On the other hand, as shown in FIG. 7, if the pressure at which the current limiting function starts to work at the maximum rotational speed is equal to or higher than the target pressure, the current limiting function always works before the speed change pump reaches the maximum rotational speed. The addition of the pump can be determined without causing extra pressure fluctuations.
Other configurations other than those described here are the same as those in the first embodiment.

  In the determination of the second additional condition in the first embodiment and the additional condition in the second embodiment, the operation current value of the transmission pump is compared with the current limit value stored in the control device. , It is determined that the current limiting function is working, but it is determined that the current limiting function is working, such as by using a signal to notify that the current limiting function sent from the inverter to the control device is working. You may do it.

It is a figure which shows the prior art example of the water supply apparatus which supplies water to a water supply end. It is a QH diagram at the time of performing the estimated terminal pressure constant control of the water supply apparatus which supplies water to a water supply end. It is a QH diagram for demonstrating the electric current limiting function of an inverter. It is a figure which shows one Embodiment of the variable speed water supply apparatus which concerns on this invention, and is the figure which extracted a part of FIG. 1 and showed the control apparatus in detail. It is a flowchart of the presumed terminal pressure constant control of the variable speed water supply apparatus which concerns on this invention. It is a flowchart of control of the additional start of a pump. The upper diagram is a QH diagram when the estimated terminal pressure constant control of the water supply device is performed, and the lower diagram is a diagram showing the relationship between the flow rate of the water supply device and the current value of the starting pump. It is a flowchart which shows the disconnection operation of a pump. FIG. 9A is a flowchart for determining whether to add a pump, and FIG. 9B is a flowchart for determining whether a pump is disconnected. The upper diagram is a QH diagram when the estimated terminal pressure constant control of the water supply device is performed, and the lower diagram is a diagram showing the relationship between the flow rate of the water supply device and the current value of the starting pump.

Explanation of symbols

1 Motor pump 2 Inverter (frequency converter)
3 Pressure tank 4 Discharge pressure sensor 6 Flow switch (flow rate detection means)
7, 14 Check valve 8 Suction side pipe 9 Water main pipe 10 Suction side pressure sensor 11 Backflow prevention device 12 Bypass pipe 13 Discharge side piping 15 Controller 16 Setting unit 17 Storage unit 18 Calculation unit 19 Display unit 20 I / O unit M motor

Claims (3)

Provided with a plurality of pumps, a plurality of frequency converters having a current limiting function for shifting each of the pumps, a discharge-side pressure sensor, and a control device for controlling these devices, and the plurality of pumps are operated in parallel. A variable speed water supply device,
The control device operates the variable speed pump at a variable speed so that the detected pressure of the discharge-side pressure sensor matches a target pressure, and a current limiting function works in a frequency converter that drives the variable speed pump, and When the detected pressure of the discharge side pressure sensor is equal to or lower than the target pressure, it is determined that the output current value of the frequency converter that drives the transmission pump is equal to or higher than a preset limit current value . A variable speed water supply apparatus characterized by starting a pump. Furthermore, a flow rate detection means provided for each of a plurality of pumps is provided,
The control device starts the additional pump even when the frequency command value to the variable speed pump is the maximum number of revolutions and the state where the amount of water is not small is continued for a predetermined time by the detection of the flow rate detecting means. variable speed water supply apparatus according to claim 1 Symbol mounting to. After starting the additional pump, the control device operates at a variable speed so that the detected pressure of the discharge-side pressure sensor coincides with a target pressure using the additional pump as a speed change pump and has been operated first. 3. The variable speed water supply apparatus according to claim 1, wherein the pump is operated as a fixed speed pump at a speed equal to or lower than an additional operation frequency. 4.

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