JP3883382B2 - Water supply equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a water supply apparatus including a pump, and more particularly, to a water supply apparatus including a submersible motor pump for deep wells that is operated at a variable speed by a frequency converter such as an inverter.
[0002]
[Prior art]
A pump such as a submersible motor pump for deep wells is widely used to operate the pump at a variable speed by using a frequency converter (inverter) that supplies an arbitrary frequency and voltage to the pump. For example, in a ranch or the like in an area where power supply conditions are poor, there is a case where the output voltage of a solar cell is converted into power by an inverter and supplied to a pump, and well water is pumped from a well into a tank on the ground and stored. Such a water supply device using a solar cell is operated by electric power generated corresponding to the amount of solar radiation, but since the pumped water is once accumulated in the tank, the water stored in the tank is needed as needed. Can be used for drinking water for livestock.
[0003]
The amount of power supplied from the solar battery varies depending on the amount of solar radiation and the operating state (voltage, current, frequency) of the motor pump. Therefore, in such a water supply device, in order to operate the pump most efficiently, maximum power tracking control is performed to control the voltage, current, and frequency supplied to the pump so that the maximum power can be supplied.
[0004]
[Problems to be solved by the invention]
This type of water supply device is normally adjusted to drive the pump only when the amount of solar radiation is sufficient for pumping, but if this adjustment is not made sufficiently, or if unusual operating conditions overlap For example, if the amount of solar radiation is small, the pump may continue to operate without sufficient pumping, and the pump may be in a shutoff operation state. If such a shut-off operation continues, the pump will be overheated. Therefore, it is necessary to take measures such as detecting the shut-off operation, outputting an alarm and stopping the pump.
[0005]
This invention is made | formed in view of the problem of such a prior art, and it aims at providing the water supply apparatus which can continue a driving | operation, preventing the shut-off operation of a pump.
[0006]
[Means for Solving the Problems]
In order to solve such a problem in the prior art, an aspect of the present invention is a water supply apparatus including a pump and a frequency converter that supplies electric power to the pump and controls the rotational speed of the pump. A reference current value table associating a rotation frequency of the pump with a reference current value serving as a criterion for determining the cutoff operation at the rotation frequency, a rotation frequency detecting means for detecting the rotation frequency of the pump, and the reference current value table. Reference current value acquisition means for acquiring a reference current value corresponding to the rotation frequency detected by the rotation frequency detection means, current detection means for detecting a current value supplied to the pump, and current detection means And a comparison means for comparing the current value detected by the reference current value acquired by the reference current value acquisition means.
[0007]
In this case, the operation of the pump can be stopped when it is determined that the current value detected by the current detection means is lower than the reference current value. Further, the operation of the pump may be stopped after a predetermined time has elapsed.
[0008]
According to the present invention, it is possible to detect the cutoff operation and stop the pump during the operation of the pump, and therefore it is possible to prevent the pump from being damaged due to overheating due to the cutoff operation.
[0009]
Furthermore, after stopping the operation of the pump, the operation of the pump may be resumed after a predetermined time has elapsed. Thereby, since it becomes maintenance-free, a problem does not occur even in unmanned operation, and it is possible to prevent water storage from becoming insufficient due to a long-term pump stop.
[0010]
The predetermined time may be determined in advance for each rotation frequency of the pump. Thereby, flexible control according to the rotational frequency of the pump becomes possible.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of a water supply apparatus according to the present invention will be described in detail with reference to FIGS. 1 to 3.
FIG. 1 is a diagram illustrating an overall configuration of a water supply apparatus in the present embodiment. In addition, in the following description, although the water supply apparatus using a solar cell as a power supply is demonstrated, it is also possible to use a wind power generator and a storage battery as a power supply.
[0012]
As shown in FIG. 1, a water supply apparatus according to the present invention includes a solar cell 1 that converts sunlight into electrical energy, and an inverter that converts DC power supplied from the solar cell 1 into AC power suitable for pump operation. 2 and a motor pump 3 driven by electric power supplied from the inverter 2. The motor pump 3 is a submersible motor pump in which a pump and a canned motor are integrated, and is disposed at the bottom of the well 6. A water storage tank 5 connected to the motor pump 3 via the discharge pipe 4 is disposed on the ground, and water in the well 6 is pumped into the water storage tank 5. Then, the water accumulated in the water storage tank 5 is supplied to a required area through the pipe 8 by opening the valve 7.
[0013]
The solar cell 1 converts incident solar energy into electrical energy, and supplies a DC voltage of about DC 100 to 175 V to the inverter 2. The inverter 2 converts the DC power received from the solar cell 1 into AC power by pulse width modulation, and supplies this AC power to the motor pump 3 via the cable 9. The inverter 2 supplies the motor pump 3 with a maximum operating frequency of 240 Hz. This operating frequency is considerably higher than the frequency of a normal commercial power supply of 50 Hz or 60 Hz. Thus, by increasing the rotational speed of the motor pump, the size of the motor pump itself can be reduced.
[0014]
If the amount of solar radiation decreases and the power supplied from the solar cell decreases, the operating frequency of the pump 3 decreases, and a sufficient head cannot be secured. It is possible to become a driving situation. If such a shut-off operation continues, the pump 3 will be overheated.
[0015]
Therefore, the water supply apparatus according to the present invention is provided with the control device 10 for preventing the operation in the state of the above-described deadline operation. FIG. 2 is a block diagram showing the configuration of the control device 10.
[0016]
Generally, in the state of deadline operation, the load is abnormally light because the pump does not perform the work of pumping water. Therefore, if the minimum load current (cutoff current) is set in advance, it can be determined that the pump is in the cutoff operation when the pump operating current falls below this current value. Since such a cutoff current value varies depending on the rotational speed (operation frequency) of the pump, it is necessary to set a cutoff current value for each rotational speed. In the present embodiment, a storage device (not shown) installed in the control device 10 is associated with a pump operating frequency and a reference current value (deadline current) that serves as a criterion for determining the cutoff operation at that frequency. A reference current value table 20 is stored. For example, as shown in FIG. 3, a combination of five points (A, B, C, D, E) of pump operating frequencies and reference current values is prepared, and a reference current value complemented by a straight line between the points. Use a table.
[0017]
Further, as shown in FIG. 2, the control device 10 corresponds to the frequency of the secondary side current of the inverter 2, that is, the frequency detector 21 that detects the operation frequency of the pump, and the frequency detected by the frequency detector 21. A reference current value acquisition unit 22 that acquires a reference current value with reference to the reference current value table 20, and a current detector that detects a current value of a secondary side current of the inverter 2, that is, a current value of a motor in the pump 3. 23 and a comparator 24 that compares the current value detected by the current detector 23 with the reference current value acquired by the reference current value acquisition unit 22.
[0018]
In addition, the storage device of the control device 10 includes a first preset time which is a time until the pump is stopped when a deadline operation is performed, and a time until the pump is restarted after the pump is stopped. The second preset time is stored in advance. The first preset time needs to be shorter than the time for the pump to be damaged due to overheating due to the shutoff operation of the pump. In addition, since the degree of overheating due to the shut-off operation increases as the rotational speed of the pump increases, the first preset time is set to each rotational speed, for example, the first preset time is shortened when the rotational speed is high. Alternatively, it may be set. On the other hand, the second preset time is set to a time sufficient for the pump that has been heated to some extent to cool down.
[0019]
Next, the operation during operation of the water supply apparatus according to the present invention will be described. FIG. 4 is a flowchart showing an operation during operation of the water supply apparatus.
During the operation of the water supply device, the frequency of the secondary current of the inverter 2 is detected by the frequency detector 21 in the control device 10 (step 1). Then, the reference current value acquisition unit 22 refers to the reference current value table 20 and acquires a reference current value corresponding to the detected frequency (step 2).
[0020]
Next, the current value of the motor in the pump 3 is detected by the current detector 23 (step 3), and the current value is compared with the reference current value in the comparator 24 (step 4). Here, when the motor current value is lower than the reference current value and the state where the motor current value is lower than the reference current value continues longer than the first preset time, the pump is in a cutoff operation state. And the pump operation is stopped (step 5). In this case, for example, an alarm may be displayed by turning on an LED lamp or the like. As described above, according to the present invention, it is possible to detect the shutoff operation of the pump and stop the pump. Therefore, it is possible to prevent the pump from being damaged due to overheating due to the shutoff operation.
[0021]
Such deadline operation is a phenomenon that occurs when the amount of solar radiation is extremely unique, and since the amount of solar radiation changes sequentially, it is expected that sufficient solar radiation can be obtained over time. it can. Further, in a ranch or the like that requires a water supply device using such a solar cell, maintenance and inspection by humans is often not complete, and it is desired that the maintenance is free.
[0022]
Therefore, in the present embodiment, after the pump is stopped as described above, the pump is automatically returned. In the present embodiment, after the second preset time has elapsed since the shutoff operation was detected and the pump operation was stopped, the pump operation is automatically returned and the pump operation is resumed (step 6). By automatically returning the pump in this way, maintenance becomes free, so that no problem occurs even during unattended operation, and it is possible to prevent water storage from becoming insufficient due to the pump being stopped for a long period of time.
[0023]
Here, FIG. 5 is a graph showing a change in the temperature rise value of the pump when the above-described shutoff operation is detected in the water supply apparatus according to the present invention. In the example shown in FIG. 5, the first preset time is 2 minutes and 30 seconds, and the second preset time is 5 minutes. As shown in FIG. 5, after the first preset time elapses, the operation of the pump is stopped and the temperature of the pump is lowered. Then, after the second preset time has elapsed, the operation of the pump is resumed and the temperature of the pump rises. This operation is repeated when the state of the shut-off operation continues, and the temperature of the pump repeatedly rises and falls, but never exceeds a certain value. As described above, by appropriately setting the first preset time and the second preset time, the pump can be prevented from being overheated to a certain temperature or higher.
[0024]
Although one embodiment of the present invention has been described so far, it is needless to say that the present invention is not limited to the above-described embodiment, and may be implemented in various forms within the scope of the technical idea.
[0025]
【The invention's effect】
As described above, according to the present invention, it is possible to detect the shut-off operation and stop the pump during the operation of the pump. Therefore, it is possible to prevent the pump from being damaged due to overheating due to the shut-off operation. It becomes.
[0026]
In addition, since it becomes maintenance-free, there is no problem even in unattended operation, and it is possible to prevent water storage from becoming insufficient due to a long-term pump stop.
[Brief description of the drawings]
FIG. 1 is a diagram showing an overall configuration of a water supply apparatus according to an embodiment of the present invention.
FIG. 2 is a block diagram showing a configuration of a control device shown in FIG.
3 is a diagram showing an example of a reference current value table stored in the control device shown in FIG. 2; FIG.
FIG. 4 is a flowchart showing an operation during operation of the water supply apparatus according to the embodiment of the present invention.
FIG. 5 is a graph showing a change in a temperature rise value of a pump when a shutoff operation is detected in the water supply apparatus according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Solar cell 2 Inverter 3 Motor pump 4 Discharge pipe 5 Water storage tank 6 Well 7 Valve 8 Piping 9 Cable 10 Control apparatus 20 Reference current value table 21 Frequency detector 22 Reference current value acquisition device 23 Current detector 24 Comparator

Claims (5)

In a water supply apparatus comprising a pump and a frequency converter that supplies electric power to the pump and controls the rotational speed of the pump,
A reference current value table associating the rotation frequency of the pump with a reference current value serving as a criterion for determining the cutoff operation at the rotation frequency;
Rotation frequency detection means for detecting the rotation frequency of the pump;
Reference current value acquisition means for acquiring a reference current value corresponding to the rotation frequency detected by the rotation frequency detection means with reference to the reference current value table;
Current detection means for detecting a current value supplied to the pump;
A water supply apparatus comprising: a comparison unit that compares a current value detected by the current detection unit with a reference current value acquired by the reference current value acquisition unit. The water supply device according to claim 1, wherein when the current value detected by the current detection means is determined to be lower than the reference current value, the operation of the pump is stopped. 2. The water supply device according to claim 1, wherein when the current value detected by the current detection unit is determined to be lower than the reference current value, the operation of the pump is stopped after a predetermined time has elapsed. . The water supply device according to claim 2 or 3, wherein the operation of the pump is resumed after a predetermined time has elapsed after the operation of the pump is stopped. The water supply apparatus according to claim 3 or 4, wherein the predetermined time is predetermined for each rotation frequency of the pump.

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