JP3054352B2 - How to operate pumps connected in parallel - Google Patents

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 an inverter-controlled variable speed motor.

[0002]

2. Description of the Related Art In a fluid supply apparatus in which a supply pressure or a supply flow rate is controlled by a plurality of pumps driven by a variable speed motor controlled by an inverter, when a second or subsequent pump is started (or stopped). , The rate of change of the inverter frequency according to the pump flow rate (or discharge pressure) is 2
The present applicant has already proposed a technique in which the pressure fluctuation at the time of increase and decrease of the operated pump is suppressed by changing the operation in stages (see Japanese Patent Application Laid-Open No. 4-358787).

[0003]

However, according to this method, in order to suppress a 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 is reduced. It is necessary to set the rate of change of the second stage of the frequency low. Therefore, as shown in FIG. 5, there is no problem when the rate of increase in demand is relatively low, but when the rate of increase in demand is higher than a certain level, the flow rate increase rate of the new starting pump cannot follow, The recovery of the supply pressure had been delayed.

The present invention solves the above-mentioned drawbacks of the prior art, suppresses the pressure rise at the time of starting a new pump low, and increases the pump speed quickly 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 a pump connected in parallel which can recover a 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 pump operating method that to obtain the required supply pressure or supply rate by increasing or decreasing, new
Before or after a new start pump flow is positive
The reason why the discharge pressure of the pump becomes equal to the discharge pressure of the running pump
The previous region increases the inverter frequency at the maximum allowable speed
After the new startup pump has a positive flow, or
The discharge pressure of the newly started pump is equal to the discharge pressure of the already operated pump
After the recovery, the area of the pump that has already been operated
Feedback system for a new start-up pump with the target number
It was configured to control. In this case, the responsiveness of the controller that uses the flow rate or the 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 line 2. Each discharge port of these pumps 1 is connected to a common supply line 6 through a check valve 4 and an orifice 5, respectively.
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 transmitter 8 for detecting a flow rate. The common supply line 6 is provided with a pressure transmitter 9 for detecting a supply pressure. The flow rate detected by each flow transmitter 8 is provided for each pump 1 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. Are input to the calculated arithmetic units 12, respectively.
Each computing unit 12 generates a control signal based on these inputs, and supplies the output to a corresponding inverter 13.
Thereby, 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 branched like a mesh and connected to a plurality of fluid users 7. The pressure in the supply line 6 is detected at a plurality of points by separate pressure transmitters 9, and their detection signals are averaged by a pressure calculator 14 and supplied to a pressure indicating controller 11. Otherwise, the embodiment of FIG. 2 is generally similar to the embodiment of FIG.

Such a fluid supply device can be widely applied to a pump device for water supply 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 is constantly measured by the flow rate transmitter 8 at the discharge port of each pump 1 and a new pump is started, a region where the flow rate from the newly started pump is zero, in other words,
Before the new start pump flow becomes positive, or
When the discharge pressure of the starting pump is
Before starting, the motor is started by increasing the frequency of the inverter 13 at the maximum allowable speed, and after the flow rate becomes positive ,
Or the discharge pressure of the newly started pump is
In the area after the pressure becomes equal to the pressure, the flow rate (or rotation speed) of the already started pump is set to the target value, and the flow rate (or rotation speed) of the new startup pump is feedback-controlled. After the flow rate (or the number of revolutions) becomes equal to the flow rate (or the number of revolutions) of the already operated pumps, these two pumps are operated synchronously.

More specifically, when a new pump is additionally started with respect to an already operated pump, the flow rate of the newly started pump is not changed until the discharge pressure of the already operated pump reaches the discharge pressure of the already operated pump. It is zero. Therefore, increasing the maximum increase rate of the frequency of the inverter, the current
The speed of the new start-up pump can be rapidly increased without affecting the current supply pressure and supply flow rate.

[0013] The discharge pressure of the newly started pump is an already operated pump
After the discharge pressure becomes equal to the discharge pressure of the new startup pump and the flow rate of the new startup pump becomes positive, the flow rate (or rotation speed) of the new startup pump is set using the flow rate (or rotation speed) of the already operated pump as a target value.
Feedback control. Then, in a region where the deviation between the flow rate (or rotation speed) of the new startup pump and the flow rate (or rotation speed) of the already operated pump is large, the flow rate (or rotation speed) of the new startup pump rapidly increases, As the deviation between the flow rate (or rotation speed) of the new startup pump and the flow rate (or rotation speed) of the already operated pump decreases, the rate of increase in the flow rate (or rotation speed) of the new startup pump becomes slower.

By this operation, it is possible to start the pump quickly and to suppress the rate of increase of the supply pressure after the pump is started to a low level. In addition, the flow rate (or rotation speed) of the already operated pump, which is the target value of the flow rate (or rotation speed) control of the new startup pump, increases in accordance with the increase in demand. Ri target value the name large,
That than the difference between the target value and the actual value is ing large new startup pump flow (or speed) increase rate is increased,
If the rate of increase in demand is low, Ri target value is small, knob
Ri target value and than the deviation between the actual value may turn small new start pump flow (or speed) rate of increase becomes moderate.
This makes it possible to suppress a rise in supply pressure after starting the pump to a small extent and to quickly start the second and subsequent pumps without being affected by fluctuations in demand.

When the supply pressure (or supply flow rate) is low, the pump is started quickly and the supply pressure is increased by setting the sensitivity of the controller for controlling the flow rate (or rotation speed) of the starting pump high. By setting the sensitivity of the controller as low as possible, it is possible to start the pump more quickly and to suppress the rise in the supply pressure to a small value.

From the above control conditions, the control conditions in the region where the flow rate of the new start-up pump is zero or the discharge pressure of the new start-up pump is lower than the discharge pressure of the already operated pump are excluded, and the new start-up pump is excluded. It is also possible to perform feedback control from the time when the flow rate is zero to the flow rate of the operated pump as a target value. According to this, there is an advantage that the control logic can be simplified.

FIG. 4 shows an analysis result when the second pump flow rate is controlled using the first pump flow rate as a target value after the second pump flow rate becomes positive, showing the difference in the rate of increase in demand. Are shown in correspondence with.

FIG. 3 shows that after the flow rate of the second pump becomes positive, the flow rate of the second pump is controlled by using the flow rate of the first pump as a target value, and the sensitivity of the controller of the flow control is determined by the supply pressure. The analysis results for a case where the demand is decreased in accordance with the rise are shown in correspondence with the difference in the rate of increase in demand.

FIG. 4 shows that even when the increase in demand is large, the supply pressure recovers in a shorter time than in the conventional method shown in FIG. FIG. 3 shows that the recovery of the supply pressure is further accelerated by changing the feedback responsiveness of the flow control at the time of starting the pump according to the supply pressure.

[0020]

As described above, according to the present invention, in a fluid supply device in which a supply pressure (or a supply flow rate) is controlled by a plurality of pumps driven by a variable speed motor using an inverter, This has a great effect on quickly starting the pump and suppressing a change 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 when a single supply piping system is used.

FIG. 2 is a schematic configuration diagram of a fluid supply device when there are a plurality of supply piping systems.

FIG. 3 is a graph showing changes over time in supply pressure, pump rotation speed, and pump flow rate when the pump operation method according to the present invention is applied.

FIG. 4 is a graph showing a change with time of a supply pressure, a pump rotation speed, and a pump flow rate when another example of the pump operation method according to the present invention is applied.

FIG. 5 is a graph showing changes over time in supply pressure, pump rotation speed, and pump flow rate when a conventional pump operation method is applied.

[Explanation of symbols]

 Reference Signs List 1 pump 2 suction line 3 fluid tank 4 check valve 5 orifice 6 supply line 7 fluid user 8 fluid transmitter 9 pressure transmitter 10 fluid indicating controller 11 pressure indicating controller 12 computing unit 13 inverter 14 pressure computing unit

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Shoji Kobayashi 2-12-1 Tsurumichuo, Tsurumi-ku, Yokohama-shi, Kanagawa Prefecture Inside Chiyoda Kako Construction Co., Ltd. (56) References JP-A-3-246394 (JP, A) JP-A-4-358781 (JP, A) JP-A-64-25202 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F04B 49/00-51/00 F04B 23/04

Claims (2)

(57) [Claims] 1. A pump operating method in which 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 is obtained by increasing or decreasing the number of driven pumps. Before the flow of the new start-up pump becomes positive, or
When the discharge pressure of the starting pump is
Area before the inverter frequency is
Increase the flow after the new start pump flow is positive or
When the discharge pressure of the starting pump is
The method for operating the pumps connected in parallel is characterized by performing feedback control of a new starting pump using the flow rate or the number of revolutions of the already operated pump as a target value. 2. The target of the flow rate or the number of revolutions of the already operated pump
Control flow rate or rotation speed of new startup pump as value
The responsiveness of the controller is determined by the supply pressure or
The method according to claim 1, wherein the pump is changed according to the amount .