JPH09151858A - Parallelly-connected pump operating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the fluctuation of supply pressure and supply flow rate to a small degree by controlling the flow rate or rotating speed of a newly started pump with the flow rate or rotating speed of an already operated pump as the target value in a pumping plant constituted by parallelly connecting a plurality of pumps individually driven by variable speed motors controlled by inverters. SOLUTION: In the installation of a pumping plant or the like for waterworks and sewageworks, with the respective discharge openings of a plurality of pumps 1 connected to a common feed pipeline 6 respectively through check valves 4 and orifices 5, flow rate is measured by a flow rate transmitter 8 provided at the discharge opening of each pump 1. In the case of starting a new pump, in an area where the discharge from the started pump is zero, the frequency of an inverter 13 is increased at the allowable maximum speed to start a motor. After the flow rate becomes positive, the flow rate of the newly started pump is controlled with the flow rate of the already operated pump as the target value, and after the flow rate of the newly started pump becomes equal to that of the already operated pump, these pumps are controlled to be operated synchronously.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of operating a plurality of pumps driven by a variable speed motor controlled by an inverter.

[0002]

2. Description of the Related Art In a fluid supply apparatus for controlling a supply pressure or a supply flow rate by a plurality of pumps driven by a variable speed motor controlled by an inverter, when starting (or stopping) a second pump and thereafter. , The rate of change of the frequency of the inverter according to the flow rate (or discharge pressure) of the pump is 2
The present applicant has already proposed a technique for suppressing the pressure fluctuation when the pump to be operated is increased or decreased by changing the number of stages (see Japanese Patent Laid-Open No. 4-358781).

[0003]

However, according to this method, in order to suppress the pressure increase at the time of starting the second and subsequent pumps, the inverter after the flow rate of the newly started pump becomes positive. It is necessary to set the rate of change in the second stage of frequency low. Therefore, as shown in FIG. 5, when the demand increase rate is relatively low, there is no problem, but when the demand increase rate is higher than a certain level, the flow rate increase rate of the new starting pump cannot follow, The recovery of supply pressure was delayed.

The present invention solves the above-mentioned drawbacks of the prior art, suppresses the pressure increase at the time of new pump startup to a low level, and increases the pump speed promptly without being greatly affected by the rate of increase in demand. The present invention has been devised for the purpose of providing a method of operating pumps connected in parallel that can recover the supply pressure in a short time.

[0005]

In order to achieve such an object, in the present invention, a plurality of pumps individually driven by an inverter-controlled variable speed motor are connected in parallel, and the number of driven pumps is reduced. In the operation method of the pump that obtains the required supply pressure or supply flow rate by increasing or decreasing, it is configured to control the flow rate or rotation speed of the new starting pump with the flow rate or rotation speed of the already operated pump as the target value. .
Especially, in the region where the flow rate of the new starting pump is zero or the discharge pressure of the new starting pump is lower than the discharge pressure of the already operated pump, the frequency of the inverter is increased at the maximum allowable speed and the flow rate of the new starting pump becomes positive. When the discharge pressure of the new starting pump becomes equal to the discharge pressure of the operating pump, the new starting pump is controlled with the flow rate or rotation speed of the operating pump as the target value. After the flow rate or the rotational speed of was equal to the flow rate or the rotational speed of the already operated pump, both pumps were operated in synchronization. Further, in this case, the responsiveness of the controller, which uses the flow rate or rotation speed of the new starting pump as a control amount, is changed according to the supply pressure or the supply flow rate.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 shows a fluid supply device to which the present invention is applied. In FIG. 1, the suction ports of a plurality of pumps 1 are connected to a fluid tank 3 via a common suction pipe line 2. Each of the discharge ports of these pumps 1 has a common supply line 6 through a check valve 4 and an orifice 5.
It is connected to the. The end of this supply line 6 is connected to a fluid user 7.

The orifice 5 provided at the discharge port of each pump 1 is provided with a flow rate transmitter 8 for detecting the flow rate. The common supply line 6 is provided with a pressure transmitter 9 for detecting the supply pressure. The flow rate detected by each flow rate transmitter 8 is provided via the flow rate indicating controller 10 and the supply pressure detected by the pressure transmitter 9 is provided via the pressure indicating controller 11 in correspondence with each pump 1. It is input to each of the calculated arithmetic units 12.
Each arithmetic unit 12 generates a control signal based on these inputs and supplies the output to the corresponding inverter 13.
As a result, the motor of each pump 1 is controlled at a variable speed.

The fluid supply device shown in FIG. 2 is generally similar to that shown in FIG. 1, but in this case the supply line 6
Are connected like a mesh and are connected to a plurality of fluid users 7. The pressure in the supply line 6 is detected by different pressure transmitters 9 at a plurality of points, and the detection signals are averaged by the pressure calculator 14 and supplied to the pressure indicating controller 11. In all other respects, the embodiment of FIG. 2 is similar to the embodiment of FIG.

Such a fluid supply device can be widely applied to a pump device for water and sewerage, a material supply device in a chemical plant or the like, or a fuel supply facility in an airport or the like.

When the flow rate transmitter 8 at the discharge port of each pump 1 constantly measures the flow rate to start a new pump, the area where the flow rate from the new starting pump is zero is the maximum allowable speed of the inverter. After increasing the frequency of 13 to start the motor and the flow rate becomes positive, set the flow rate (or rotation speed) of the pump that is already operating to the target value and set the flow rate (or rotation speed) of the new starting pump. ) Is controlled so that the flow rate (or rotation speed) of the new starting pump becomes equal to the flow rate (or rotation speed) of the already operated pump, these two pumps are operated in synchronization.

More specifically, when a new pump is additionally started up with respect to the pump that is already in operation, the flow rate of the new starting pump is zero until the discharge pressure of the new pump reaches the operating pressure. Therefore, even if the rate of increase in the frequency of the inverter is maximized, it is possible to rapidly increase the rotation speed of the new starting pump without affecting the supply pressure and the supply flow rate.

After the discharge pressure of the new starting pump becomes equal to the operating pressure and the flow rate of the new starting pump becomes positive, the new starting pump is set with the flow rate (or rotation speed) of the already operated pump as a target value. Control the flow rate (or rotation speed). Then, in a region where the flow rate (or rotational speed) of the new starting pump and the flow rate (or rotational speed) of the already-operated pump are large, the flow rate (or rotational speed) of the new starting pump rapidly increases, and As the deviation between the flow rate (or rotational speed) of the new starting pump and the flow rate (or rotational speed) of the already operated pump decreases, the rate of increase in the flow rate (or rotational speed) of the new starting pump becomes gentle.

By this action, the pump can be started rapidly and the rate of increase of the supply pressure after starting the pump can be suppressed low. In addition, the flow rate (or rotation speed) of the already-operated pump, which is the target value for the flow rate (or rotation speed) control of the new startup pump, increases in accordance with the increase in demand, so if the increase rate of demand is high, Since the target value becomes large, the flow rate (or rotational speed) of the new starting pump increases at a high rate, and when the rate of increase in demand is low, the target value becomes small, so the flow rate (or rotational speed) of the new starting pump increases. The speed becomes slow. This makes it possible to suppress the increase in supply pressure after starting the pump to be small and to quickly start the second and subsequent pumps without being affected by demand fluctuations.

When the supply pressure (or supply flow rate) is low, the sensitivity of the controller for controlling the flow rate (or rotation speed) of the starting pump is set to be high, so that the pump is rapidly started and the supply pressure is high. By setting the sensitivity of the controller to be lower as it becomes, it becomes possible to start the pump more quickly and to suppress the increase in the supply pressure to a small level.

From the above control conditions, the control conditions in the region where the flow rate of the new starting pump is zero or the discharge pressure of the new starting pump is lower than the discharge pressure of the already operated pump are excluded, and the new starting pump is removed. It is also possible to control the flow rate of the already operated pump as a target value when the flow rate of is zero. And according to this, the advantage that a control logic can be made into a simpler structure is acquired.

FIG. 3 shows the analysis results when the second pump flow rate is controlled with the first pump flow rate as a target value after the second pump flow rate becomes positive. It corresponds and shows.

In FIG. 4, after the flow rate of the second pump becomes positive, the flow rate of the second pump is controlled with the pump flow rate of the first unit as a target value, and the sensitivity of the controller for the flow rate control is set to the supply pressure. The results of the analysis in the case of a decrease in response to an increase are also shown, corresponding to the difference in the rate of increase in demand.

It can be seen from FIG. 3 that the supply pressure can be recovered in a shorter time than in the conventional method shown in FIG. 5 even when the demand increases greatly. Further, it can be seen from FIG. 4 that the recovery of the supply pressure becomes much faster by changing the feedback response of the flow rate control at the time of starting the pump according to the supply pressure.

[0020]

As described above, according to the present invention, in the fluid supply device for controlling the supply pressure (or the supply flow rate) by the plurality of pumps driven by the variable speed motor using the inverter, the second and subsequent units are used. A large effect can be exerted in promptly starting the pump and suppressing fluctuations in the supply pressure and the supply flow rate to be small.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a fluid supply device having a single supply pipe system.

FIG. 2 is a schematic configuration diagram of a fluid supply device having a plurality of supply piping systems.

FIG. 3 is a time-dependent change diagram of a supply pressure, a pump rotation speed, and a pump flow rate when the pump operation method according to the present invention is applied.

FIG. 4 is a time-dependent change diagram of supply pressure, pump rotation speed, and pump flow rate when another example of the pump operating method according to the present invention is applied.

FIG. 5 is a time-dependent change diagram of a supply pressure, a pump rotation speed, and a pump flow rate when a conventional pump operation method is applied.

[Explanation of symbols]

 1 Pump 2 Suction Pipeline 3 Fluid Tank 4 Check Valve 5 Orifice 6 Supply Pipeline 7 Fluid User 8 Fluid Transmitter 9 Pressure Transmitter 10 Fluid Indicating Controller 11 Pressure Indicating Regulator 12 Operator 13 Inverter 14 Pressure Operator

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toyomitsu Kanai 2-12-1, Tsurumi Chuo, Tsurumi-ku, Yokohama-shi, Kanagawa Chiyoda Kako Construction Co., Ltd. (72) Shoji Kobayashi Tsurumi-chuo, Tsurumi-ku, Yokohama-shi, Kanagawa 2-12-1 Chiyoda Kako Construction Co., Ltd.

Claims (3)

[Claims] 1. A method of operating a pump, wherein a plurality of pumps individually driven by an inverter-controlled variable speed motor are connected in parallel, and a required supply pressure or supply flow rate is obtained by increasing or decreasing the number of driven pumps. A method of operating parallel-connected pumps, wherein the flow rate or rotation speed of a new starting pump is controlled using the flow rate or rotation speed of an already operated pump as a target value. 2. When the flow rate of the new starting pump is zero or the discharge pressure of the new starting pump is lower than the discharge pressure of the already operated pump, the frequency of the inverter is increased at the maximum permissible speed, and the flow rate of the new starting pump is increased. Becomes positive, or after the discharge pressure of the new starting pump becomes equal to the discharge pressure of the already operated pump, the new starting pump is controlled with the flow rate or rotation speed of the already operated pump as the target value. The method for operating parallel-connected pumps according to claim 1, wherein both pumps are operated in synchronization after the flow rate or the rotational speed of the starting pump becomes equal to the flow rate or the rotational speed of the already operated pump. 3. The responsiveness of a controller that uses the flow rate or rotation speed of an already operated pump as a target value and sets the flow rate or rotation speed of a new starting pump as a control amount is changed according to the supply pressure or the supply flow rate. The method for operating parallel-connected pumps according to claim 1 or 2.