JPS6079195A - Protective apparatus for variable speed-change pump - Google Patents

Abstract

PURPOSE:To prevent the lack of water during too-little water-amount operation and the rise of the temperature of water in a casing by transmitting the instruction to stop a variable speed-change pump when water feeding pressure stays between an aimed pressure and the pressure in the operation with the reduced number of pumps for a certain time. CONSTITUTION:When the pressure in a water feeding pipe 8 is smaller than the in-parallel introduced pressure H1, a motor 5a is controlled to speed-change- operate a variable speed-change pump 4a, and controls a motor 5b to constant- speed-operate a variable speed-change pump 4b. Thus, the operation speed of a pump in speed-change operation is reduced. After the operation speed reaches the min. speed Nmin, the pressure in the water feeding pipe 8 is detected, and when the pressure is larger than the in-parallel release pressure H2, one pump is put into stop, and the instruction to put the pump in speed-change operation at the max. speed is transmitted. When the above-described pressure stays between an aimed pressure H0 and the in-parallel release pressure H2 for 2-3min, one pump is set into stop.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a water supply system that uses both a constant-speed pump and a variable-speed pump, and in particular, the present invention relates to a water supply system that uses a constant-speed pump and a variable-speed pump in combination. This invention relates to a membrane device for variable speed pumps that can prevent water from falling and overheating in such situations.

[Background of the invention]

In a water supply system that uses both a constant speed pump and a variable speed pump as a water supply means, energy conservation is achieved by controlling the pressure to a constant level by changing the operating speed of the variable speed pump according to fluctuations in the amount of water demanded.

FIG. 1 shows the specific system configuration, and is a water supply system diagram of two variable speed pumps in suction operation. In the figure, la and lb are foot valves, and a suction pipe 3 & inserted into the water tank 2.

It is attached to the tip of 3b. 4m and 4b are pumps 6m driven by variable speed motors 5m and 5b.

6b is a check valve installed in the pump system line, 7*, 7b is a gate valve, 8 is a water supply pipe, 9 is a pressure sensor that measures the pressure of water supply pipe 8, IO is a foot valve 1a, lb for water leakage prevention 11 is a water supply pipe connected to the water supply pipe 8 to supply water to the auxiliary water/tank unit 10; 12 is a float provided in the auxiliary water tank unit IO; When the supplied water 31 reaches a predetermined amount, the water supply is automatically stopped.

13m and 13b are water supply pipes that send water to the discharge sides of the pumps 4m and 4b, 14m and 14b are check valves, and 15m and 15b are automatic drain valves installed in the middle of the water supply pipes 13a and 13b. By opening circuits 15m and 15b, part of the water supplied to the pumps 4m and 4b is discharged, thereby preventing water from falling into the pumps and overheating inside the casing.

In other words, in the same configuration, two variable speed pumps 4m
, 4b is driven to supply water from the water supply pipe 8. However, if the measurement result by the pressure sensor 9 indicates that water supply by two pumps is not required, one or both variable speed modes are controlled by a control circuit (not shown). and variable speed pump 4m, 4
Reduce the water supply amount by operating b' at low speed. At that time, for example, if only one pump 4a is operated at low speed or stopped, water in the pump may fall through the gap in the foot valve 1a even though auxiliary water is being supplied through the water replenishment pipe 13m. In addition, since there is no water in the pump, the pump itself will overheat and be destroyed.18 Kaisho GO-79
195(2).

FIG. 2 is a diagram showing the operating characteristics of the water supply system shown in FIG. 1, in which the horizontal axis represents the amount of water 9 minutes, and the vertical axis represents the pressure H. In the figure, curve g shows the Q-H performance when the pump operating speed is the maximum speed NMAX, and similarly, j, i, and h are the curves when the pump operating speed is Nl sN2 sN51N1, respectively.
The Q-H performance when 1 is shown. In addition, the curve f shows that one pump is operated at a constant speed and the operating speed is the lowest speed NMIN.
This is the Q-H characteristic when operating in parallel. Similarly, for curves a, d, e, b, and a, the operating speeds of the constant speed pump and variable speed pump are Nl *N2 +N5 sNIImNMA
It shows the Q-H performance when operating in parallel with X. Furthermore, Ho is the target pressure of the water supply system (corresponding to the total head of the pump). And these curves a, b, o...
...The intersection points A, B, C of k and the straight line of target pressure H,
. . . K indicates the operating point when the pump is operated while maintaining the pressure of the water supply pipe 8 at tHo while changing the operating speed of the pump according to the amount of water demanded. In addition, Qmus QB + Qc...
...QK indicates the discharge amount of the pump at that time.

The water supply in the water supply system shown in Fig. 1 is carried out by driving the pumps 4m and 4b, respectively, and operating the pumps according to the water demand as shown in the characteristic diagram of Fig. 2 while maintaining the target pressure HO. Water is supplied to the end faucet by changing the speed. If the pump is operated at low speed during such water supply operation, the water flow will be insufficient. This is the water flow rate QHIN.
Automatic drain valve 15 m or 15 b if:
is opened to discharge water from the water supply pipe 8. This prevents the pump from watering down and overheating inside the pump casing.

In other words, in the above-mentioned water supply system, if the range of water usage is between the water amount Qy = Qy' shown in Figure 2 for a long time, the variable speed pump will be in closed operation and there is a high possibility of water falling, and once water falls, It was impossible to pump water, and the water temperature inside the pump casing rose, which was extremely dangerous, so an automatic drain valve had to be installed to release the water. According to this, not only is the released water wasted, but
Completely prevents low water flow operation.
It was necessary to install a solenoid valve and an orifice that constitute an automatic drain valve, which was expensive and had low reliability.

[Purpose of the invention]

An object of the present invention is to prevent water from falling and an increase in water temperature within the casing when the pump is operating with a low water flow.

[Summary of the Invention] The variable speed pump protection device according to the present invention compares a predetermined target pressure with the actually measured pressure inside the water supply pipe, and adjusts the variable speed pump so that the measured pressure matches the target pressure. A means is provided to issue a stop command to the variable speed pump when the operating speed of the pump is changed and the water supply pressure remains between the target pressure and the pump platform pressure set slightly higher than that for a certain period of time,
This is designed to prevent water from overheating when the variable speed pump is operated at the lowest speed.

[Embodiments of the invention]

An embodiment of the present invention will be described in detail below with reference to FIGS. 3 and 4. The first part is a control circuit diagram of a variable speed pump protection device assuming the water supply system shown in Figure 1.
is a three-phase AC power supply, MCB is a 7-page disconnector, and MCo1 to MCl1a are magnetic contactors MCo, respectively.
- The contact point of MC11, Ml + M2, is the variable speed pump 4m shown in FIG.

The motor that drives motor 4b corresponds to motors 5m and 5b. THI and TH2 are thermal relays for overload prevention of each motor M1 + M2, IN'v is a variable frequency inverter, μ'can is a microcomputer, central processing CPU, memory M1 power terminal E1 output capacitor. )
It has PIA-A, PIA-B, and PIA-C. This microcomputer μ.con has interfaces F1+F25G as peripheral devices.

That is, the signal detected by the pressure sensor 9 in FIG. 1 is read into the input/output boat PIA-C via the interface F1. Further, an operating speed command signal for the variable speed pump is sent from the input/output boat PIA-B to the variable frequency inverter INV via the interface F2 to command a desired operating speed. Furthermore, a signal instructing the operating order and number of pumps is output to the input/output boat PIA-A) interface G.

The interface G constituting the operation circuit CTL consists of transistors TrO to Trq, relay coils XO to Trq inserted into their collectors, and resistors R6 to RIO, and each transistor Tr( 1-Trq is the microcomputer μ・con (7) Interfuni,',
It is driven by a command signal obtained via PIA-A.

In addition, the relay circuit X is a magnetic contactor MCQ-MC11
and the relay coil contact XOa-X inserted in series with it.
It consists of I1m, switch SS, transformer T, and stabilized power supply unit 2.

In Fig. 3, to explain the case where a pump operation order command signal for one pump is output from PIA-A to interface G (input/output capo), for example,
When the b2 and b11 bits of PIA-A output a signal of "1", transistors TrO and Tr2 become conductive, relay XO# Then, the motor 5a of the pump 4a starts.

Therefore, when the switch SS is closed, the microcomputer μ.
Power is sent to the power supply terminal E of eoH, and preparations for the 900 rotation are completed.

FIG. 4 is a flowchart showing the operating procedure in the control circuit of FIG.
A program is input into the memory M of n so that these procedures are controlled in an orderly manner.

The operation of the circuit shown in FIG. 3 will be explained based on the flowchart shown in FIG. First, the microcomputer μmcan is 1
In the step, the operating speed data NM is set as the initial value.
I N * MX s NMAX s Pressure data HO
tHl s■2, data for turning on the magnetic contactor MCo-MCII. is stored in each memory. Although intermediate processing is omitted, in the next two steps, the pressure in the water supply pipe 8 is detected by the pressure sensor 9, and is loaded into a register A (not shown) of the microcomputer μ-can via the interface F11r. It is transferred to the B register (also not shown) in 3 steps, and the two are compared in 4 steps.As a result, if the pressure inside the water supply pipe is greater than the parallel introduction pressure H1 in FIG. Although it is not, the process returns to the 5th step and 10°, and processes such as pressure judgment, one-unit switching judgment, and speed control are performed again. If the pressure inside the water supply pipe 8 is lower than the parallel introduction pressure H1, the process proceeds to step 6, where a signal is output to close the electromagnetic contactor MCo + Mo 2 m MCM, and the motor 5a is controlled to start the pump. 4a
In addition to operating the pump 5b'lH at a variable speed, the motor 5b is controlled to operate the pump 5b'lH at a constant speed. At the same time, a command is issued to change the operating speed of the variable speed pump from the maximum speed NMAX to the minimum speed NMIN in seven steps. In 8 steps,
A waiting time Δt sufficient for processing in the previous 6.7 steps is executed, and in the next 9 steps, the pressure in the water supply pipe 8 is detected and loaded into the aforementioned register (not shown). Then, the target pressure Ho (memory MI
The data (contents of Q) is transferred to register B (not shown), and the two are compared in step 11. As a result of the comparison,
If the pressure inside the water supply pipe 8 is smaller than the target pressure H,
In step 12, the speed is increased until they become equal, and if the pressure in the water supply pipe 8 is greater than the target pressure HO, then in step 13, the process is performed to decrease the page speed until they become equal. If the two are equal, no shift processing is performed and the next 14 steps are executed. Here, it is determined whether or not the minimum speed NMIN has been reached, and as a result, if the minimum speed NMIN has not been reached, 8
Return to the step and execute the subsequent processing again.

When the minimum speed NMI N is reached, the process proceeds to the next 15 steps, where the pressure inside the water supply pipe 8 is detected and the register A (not shown) of the microcomputer μ・aon is detected.
Load into. Then, in step 16, the data of the target pressure HO (contents of the memory MIG for initial value setting) is transferred to the B register, and in step 17, the two are compared. As a result of the comparison, if the pressure in the water supply pipe 8 is smaller than or equal to the target pressure H, the process returns to step 8 and the subsequent processes are executed again. If the pressure inside the water supply pipe 8 is greater than the target pressure Ho, then in the next 18 steps,
Data for parallel release pressure (contents of memory M12) is transferred to the B register, and the two are compared in step 19. As a result of the comparison, if the pressure inside the water supply pipe 8 is greater than the parallel release pressure 6O-79195 (4) removal pressure H2 shown in Fig. At the same time, a command is issued to change the operating speed of the variable speed pump from the minimum speed NMIN to the maximum speed NMAX. and water pipe 8
If the pressure inside is smaller than the parallel release pressure H2, the register C (not shown) of the microcomputer μmcan is incremented in the addition step (register C is used as a counter, and the timer is set by processing the loop N times. In step t, 21, it is determined whether the count in register C has reached N times, and the loop Loop is repeated until it reaches N times. The number of times N of loop LOOR is processed is determined to be, for example, 2.3 minutes. That is, between the target pressure Ha and the parallel release pressure H2 (the amount of water used is between Qv" and Qv')
If the pump is operated for more than 3 minutes, one of the pumps is controlled to be stopped.

Therefore, conventionally, when the amount of water used was between QF - QF', the modified pump would continue to operate at the minimum speed NMIN, and especially in the case of suction operation, the falling water phenomenon would occur and pumping would become impossible. However, according to this embodiment, these problems can be solved by stopping one of the pumps.

〔Effect of the invention〕

As is clear from the above embodiments, according to the present invention, the discharge pressure of the pump constituting the water supply system is detected, compared with a target value, and controlled so that it can be operated at the target value. Since the pump is controlled to stop when the operating state remains static for a certain period of time, there is no risk of the pump operating with an insufficient amount of water, it prevents overheating and water leakage, and it also prevents wasteful discharge. There are advantages such as:

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of a water supply system with two variable speed pumps in water suction operation, Fig. 2 is an operational characteristics diagram of the water supply system in Fig. 1, and Fig. 3 is a concrete diagram of a water supply system showing an embodiment of the present invention. FIG. 4 is a one-page flowchart 4 for explaining the circuit operation of FIG. 3. Ml *M2...'Pump motor, Xo = Xq-
...Relay, MC, -MCII...Magnetic contactor, G*
F1aF2...Interface, CPU...Central processing unit, μ・eon...Microcomputer, INV...Inverter, T...Transformer, 2.
...Stabilized power supply unit. Representative Patent Attorney Masami Akimoto

Claims (1)

[Claims] a pump; a water supply pipe line disposed on the discharge side of the pump;
In a water supply system that is configured with a pressure sensor installed in the water supply pipe and supplies water according to the amount of water used, a predetermined target pressure is compared with the actually measured pressure in the water supply pipe, and the measured pressure is calculated. The operating speed of the variable speed pump is changed to match the target pressure, and the water supply pressure is between the target pressure and the pump base pressure, which is set slightly higher than the target pressure.
A protection device for a variable speed pump, characterized in that it is provided with means for issuing a stop command to the variable speed pump when the variable speed pump is stopped for a certain period of time.