JPS599719A - Operation controlling method of pump - Google Patents

Abstract

PURPOSE:To increase the stage of a pump in accordance with a detecting output, by constituting each pump connected in parallel so that its rotational frequency is controlled in accordance with a pressure schedule, and also providing a detector for detecting the maximum output state, on each pump, respectively. CONSTITUTION:A controller CON detects an input current of a driving motor in pumps P1-P3 by detectors D1-D3, and also detects a signal from a flow meter F and a differential pressure gauge DP, too. A detecting output from the flow meter F is converted to a value for showing a pressure schedule by a transducer R/B using a conversion table, is inputted to a comparator CP1, and also a detecting output of the differential pressure gauge DP is also inputted. When the detecting output of DP drops to a value of the pressure schedule or below, an output of logic ''1'' is generated from the CP1. Also, the value for showing the pressure schedule and the detecting output of the DP are provided to an operator PID, too, and rotational frequency of the pump required for obtaining the differential pressure of the pressure schedule or above is derived by an operation, is outputted as a rotational frequency control signal RS, and is compared with a reference value RL by a comparator CP2 so that a compared output can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an operation control method for controlling the operating status of a plurality of pumps connected in parallel.

Generally, in systems such as air conditioners that use pumps to pump water, there is a minimum pressure that is determined depending on the conditions of the piping and the load that receives the water supply. Conventionally, system design is based on a specified design pressure.
The number of pumps connected in parallel will be expanded and subtracted by changing the number of pumps in operation.

Note that the pressure of the water supply has a characteristic that it decreases in inverse proportion to the flow rate of the water supply, and the pressure difference between the water supply and the supply water is detected to increase or decrease the pump.

Figure 1 is a diagram showing the conventional installation status. Section A shows the operation status of one pump, section BFi pumps two, and section C shows the operation status of three pumps. The flow rate f increases and the differential pressure dp increases. If the pressure decreases to the design pressure Pd, expansion will be carried out at the boundaries between sections A and B and B and C.

In addition, a differential d is set at each boundary to prevent hunting from occurring during control.

However, the pressure schedule Psi that originally indicates the minimum pressure
Even if the differential pressure dp decreases, the flow rate f is maintained, and in the film increasing operation shown by the solid line in Fig. 1,
Margin range ft, fzf based on the difference between setting g1 pressure Pd and pressure schedule P8: This margin f+, ft"
Compared to the case where i is set to zero, the installation will be expanded earlier, so
This has the disadvantage of consuming excess power.

On the other hand, the boundaries of increase/decrease stages are determined based on the pump's rated output, but in reality, the maximum output that guarantees safe operation is higher than the rated output, and expansion is performed with a rated output that is less than the maximum output. Therefore, even though the pumps currently in operation have surplus power, they are expanded, and this also has the disadvantage of consuming surplus power.

The present invention has the purpose of fundamentally eliminating the drawbacks of the conventional art, and controls the rotation speed of each pump connected in parallel according to a pressure schedule, and also detects the maximum output state of each pump individually. In addition to providing a pump operation control method in which a detector is provided and the number of pumps is increased according to the detectable force of the detector, in addition to the above, the method also provides a method for controlling the operation of a pump according to the flow rate when the detector generates the detectable force and the rated flow rate. The present invention provides a pump operation control method in which a capacity coefficient is set, and reduction is performed in a flow rate state that is equal to or less than the value obtained by subtracting a predetermined differential from the rated flow rate multiplied by the capacity coefficient.

Hereinafter, the present invention will be explained in detail with reference to FIG. 2 showing an embodiment.

Figure 2 is an instrumentation diagram when a refrigerator is used as the heat 'rj and equipment. The cold water cooled by the refrigerators R1-R3 is sent under pressure by pumps P1 to P3 via headers H1 and H2, and It is supplied to the air conditioning load AL such as a fan coil unit through H3, and then is returned to the refrigerator R+=R3 through the header H4, and this process is repeated. The controller CONK, which has a processor, memory, etc., controls startup, shutdown, vane opening, etc.

Also, check the temperature of the water supply from header H1 using temperature sensor T! At the same time, the amount of water supplied is detected by the flow meter F, and the controller CON determines the amount of heat of the supplied water.
The temperature of the return water is detected by the temperature sensor T2, and the flow meter F
The calorific value of the return water is determined based on the detection power, and the air conditioning load is determined based on the difference in calorific value between the supplied water and the return water, and the refrigerator R is adjusted accordingly.

- Controls the increase/decrease stage of R3 and the vane opening degree.

On the other hand, the rotation speed and increase/decrease stage of the pumps Pl-Ps are controlled by the controller CON via a rotation speed control device (not shown), and the pumps P+ to P! The detector I)+-Ds detects the input current of the drive motor at , and the detected power is applied to the controller CON, thereby detecting the maximum output state of the pumps P+ to P3. It becomes.

In addition, there is a differential pressure tl- between the input sides of headers H2 and H4.
A D P is inserted, which detects the differential pressure between the water supply and the water supply and provides it to the controller, and the controller CON adjusts the rotational speed and increase/decrease stage of the pumps P1 to P3 according to this detected force. It is supposed to be controlled.

However, in this case, the pressure schedule P shown in FIG.
The rotational speed of pumps P, ~P3 is controlled to maintain a differential pressure of s or more, and the expansion is performed when these rotational speeds reach the maximum value and the differential pressure decreases according to pressure schedule P8t. It becomes.

FIG. 3 is a diagram showing the status of increasing/decreasing stages, with section A showing the operating state of one pump, section B showing the operating state of two pumps, and section C showing the operating state of three pumps. In this case, pumps P1 to P3 are shown. Pumps are added in the order of pumps P3 to P1, and reductions are made in the order of pumps P3 to P1.

That is, first, the pump PI operates, and when it reaches the maximum output state, a detection force is generated from the detector DI,
According to the flow rate at maximum output at this time and the rated flow rate Lal of pump P+, 1 is set to the capacity coefficient of controller C according to the following formula.
Calculated in OH.

K 1= L l/L (+ 1...
(1) Also, the first expansion is performed at the time of maximum output flow rate Ll, and pump P1. Parallel operation of P2 is performed.

In addition, if the flow rate decreases in this state, as shown by the dotted line, the flow rate at maximum output L (from the differential d
Attenuation is performed at the flow rate after subtracting .

On the other hand, when pumps PI and P2 enter parallel operation, the second
In preparation for the next expansion, output value L12 for the next expansion.
is calculated by the following formula.

Lu --(Lot + LO2) X Kl-...(
2) Then, LO2 is set at the rated output of pump P2.

In addition, a limit value for ensuring safety is added to the output value L+2 as, for example, ±20ch, a low limit value LL and a high limit value HL are set, and detection is performed by the detector D2 below the high limit value HL. When no force is generated, the high range limit value HL
If the output value reaches LL, the expansion is forcibly performed, and if the output value reaches the low limit value LL, the attenuation is forcibly performed when the reduction is not performed above the low limit value LL.

In addition, if the detector fails after the output value L+2 is exceeded, or if I) 2 is detected/deer occurs, the output value L11 is still low, so the maximum output when the detection force occurs is set as L2. The following equation is calculated, and the previous ability coefficient Kl is updated by adding 2 to the ability coefficient obtained thereby.

K2 = L2 / (Lot +Lo2) ---
(3) FIG. 4 is a flowchart of the control operation performed by the processor in the controller CON to realize the above-mentioned control situation. First, I(L,
LL determination'' is performed, and then the current output value is '
Below LL?゛′ is judged, and if this is NO, there is a 1 stage increase request from the circuit described later.・T” is judged, and depending on this, it is judged whether the current output value is ``HL or higher?'' .

If 'T' is greater than or equal to HL (NO'?), then the 'calculate i reduction position' is used to subtract the de7 renal cl from the rated output L6+ shown in Fig. 3, and the current output is less than or equal to the 1 stage reduction position. ? If the answer is YES, the amount of water is reduced by designating the suspension pump.

Note that if T″ below the dead stage position is NO, there is no need to increase or decrease the stage, so the status quo is maintained.

Also, is there a request for 1 stage increase?゛' YES or H
L or more? In response to YES in ``, the 1 capacity coefficient is updated'' by the calculation of equation (3), and an expansion is performed by specifying the stop pump.

Is there a request for an addition in Figure 5 to Figure 4? “YES”
This is a block diagram of a circuit that generates a film increase request signal TJSfc indicating the following.This circuit is housed in the controller CON and operates as follows.

That is, the detected force from the flow meter F is converted into a value indicating the pressure schedule by the converter R/B using a conversion table, and is applied to one input of the comparator CPr, and the detected force of the differential pressure gauge DP is converted to a value indicating the pressure schedule. is given to the other input,
When the detection force of the differential pressure gauge DP decreases to a value below the pressure schedule, the comparator CP+ produces a comparison output of the logical value %1''.

In addition, the output of the converter R/B and the detection force of the differential pressure gauge DP are given to the calculator PID, and the output of the converter R/B and the detection force of the differential pressure gauge DP are given, and the pumps P1 to P3 required to obtain a differential pressure above the pressure schedule are
The rotational speed of the pump P+-Ps is determined by calculation, and this is given to one input of the comparator CP2, and the reference value RL indicating that the rotational speed of the pump P+-Ps is 100% of the maximum is given to the other input. There is.

Therefore, when the output of the arithmetic unit PID exceeds the reference value RL, a comparison of %1'' occurs, and the comparison output of the comparator CP+ also becomes ◆1'' (AND game)
G+ will produce the output of Hayabusa 1", and OR game) G
A timer TIM for ignoring the state of the unstable period is activated via ffi, and a film increase request signal US is sent out when the timer TIM times up.

On the other hand, the detector D I-D 3 detects the comparator CPa.
~ CP6 is supplied to one input, and a reference value IL indicating the motor input current at maximum output is supplied to the other input, and the detection force of the detectors D1 to D3 is equal to or greater than the reference value m. When the comparator CPs~CP++ becomes %1n
Since the pump P
If any of P1 to P3 reaches the maximum output state, comparator C
A comparison output occurs from any of P3 to CPS and starts timer TIM via Gs and G2;
When this time-up occurs, a film increase request signal US is sent.

Note that the output of the arithmetic unit PID is directly connected to the rotation speed control signal R.
8, and this is sent out as each pump P! -Used to control the rotation speed for P3.

Therefore, the rotation speed of pumps PI-P3 is controlled according to the pressure schedule, and expansion is only performed when the differential pressure falls to the pressure schedule, and the capacity of each pump Pi-P3 is maximized. This reduces power consumption.

However, the refrigerator R1-R* in Fig. 2 may be replaced with a boiler, etc., and a dedicated control circuit may be used instead of a processor for the controller CON. The present invention can be modified in various ways, such as replacing the control operation with a processor.

As is clear from the above description, according to the present invention, when adding to a plurality of pumps connected in parallel, the addition is done in a reasonable manner and power consumption is reduced. Remarkable effects can be obtained in various water supply systems.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the conventional increase/decrease installation situation, Fig. 2 and subsequent figures show an embodiment of the present invention, Fig. 2 is an instrumentation diagram, Fig. 3 is a diagram showing the situation of increase/decrease stage, and Fig. 4 is a diagram showing the situation of increase/decrease stages. A flowchart of the control operation, and FIG. 5 is a block diagram of a circuit that generates a film increase request signal. P1~P1...φ pump, DI~D3...
Detector, CON...Controller, DP...Φ/Differential pressure gauge,
F...Flowmeter. Patent applicant Yamatake Honeywell Co., Ltd. Agent Masaki Yamakawa (and one other person)

Claims (2)

[Claims] (1) Multiple pumps that are connected in parallel and whose rotational speed is controlled according to a pressure schedule that indicates the minimum pressure of the system - Each pump is equipped with a detector that detects the maximum output state, and the detection power of the detector is A method for controlling operation of a pump, characterized in that the number of pumps is increased depending on the number of pumps. (2) A detector is installed to detect the maximum output state of each pump connected in parallel and whose rotation speed is controlled according to a pressure schedule that indicates the minimum pressure of the system, and the detector detects the detection force. A pump characterized in that a capacity coefficient is set according to the output flow rate and the rated flow rate at the time of occurrence, and the reduction is performed in a flow rate state below a value obtained by subtracting a predetermined differential from the rated flow rate multiplied by the capacity coefficient. operation control method.