JPH1061585A - Pump drop water detecting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate a discharging valve as an auxiliary device for protecting a pump and preventing drop water of a siphon pipe by detecting pump drop water. SOLUTION: In a pump making use of the siphon phenomenon, a frequency signal of a VVVF device 8 is input into a function generator 11 in which a torque curve of a pump is set, and converted into a loading side current signal in dropping of water, a loading current signal in dropping of water is set by adding 15 a bias signal from a bias setting unit 14, the set loading current signal in drop water and the acutal loading current signal detected by a CT 12 and converted by a converter 13 are compared with each other 16, that the actual loading current signal becomes lower than the set loading current signal in dropping of water is detected by a circuit of an operational amplifier 17, a transistor 18 and a relay 19, water drop is detected, and the pump is stopped and protected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting a water drop of a pump using a siphon phenomenon in sewage treatment or the like.

[0002]

2. Description of the Related Art In general, a discharge valve is installed as an auxiliary device in a sewage treatment pump or the like of a sewage treatment plant. After confirming running water with a full water detector, the pump is started to operate and the discharge valve is fully opened to supply water. Therefore, there is no danger of water drop during operation.

[0003] Fig. 2 shows the construction of a drainage pump station of a system that takes in water using the siphon phenomenon. In the figure, reference numeral 3 denotes a siphon pipe provided between the water absorption tank 1 and the discharge tank 2;
The discharge port 3 ₂ is higher than _1. Reference numeral 6 denotes a pump provided in the siphon pipe, and a pump driving motor 7 is connected to VVVF.
(Variable voltage, variable cycle) By controlling the speed by the device 8, the pump flow rate is controlled.

[0004]

In the station configuration shown in FIG. 2, there is no particular problem as long as the water levels of the tanks 1 and 2 are always at the water level.
If lower than ₁ at the top, there is a risk that the flap valve 4 is that the backflow air open, the reverse flow and siphon tube 3 by the air is no longer a vacuum, the water in the pump when the pump is decelerated to overboard There is fear.

[0005] The state of falling water is the same as the no-load operation for the pump. If the idle operation is performed, the state becomes similar to cavitation due to air, and the impeller of the pump may be broken.

In order to prevent this water drop, a discharge valve may be provided as an auxiliary device in the pump piping, but the price increases accordingly.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has as its object to detect a pump drop and to omit a discharge valve as an auxiliary device for protecting the pump and preventing the drop. It is an object of the present invention to provide a method for detecting a water drop of a pump.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a method for detecting a water drop of a pump provided in a siphon pipe, wherein an output frequency signal of a pump power supply is inputted to a function generator which sets a torque curve of the pump. It is converted to a pump load side current signal, and a bias signal is added to this signal to set a load current signal at the time of water drop according to the torque curve of the driving motor. It is characterized by detecting a water fall by comparing the actual load current signal converted into a signal with the actual load current signal and detecting that the actual load current signal is smaller than the set load current signal at the time of water fall. .

[0009]

FIG. 1 shows a circuit configuration of a pump drop detecting device. 7, reference numeral 7 denotes a motor for driving the pump 6 in the drainage station shown in FIG. 2, 8 denotes a VVVF (variable voltage variable frequency) device, and 11 denotes a function generator in which a torque curve of the pump is set. An output frequency (rotational speed) signal N (0 to 10 VDC) is input, and the load side current value is output as a DC voltage signal (0 to 10 V).

Reference numeral 12 denotes CT for detecting the actual load current, and 1
3 is an I / V converter for converting an actual load current value detected by CT into a DC voltage signal, 14 is a DC bias setting device, 1
Reference numeral 5 denotes an adder that adds a negative bias voltage signal from the setting unit 14 to the output voltage signal from the function generator 11 and outputs a load current value signal at the time of water drop according to the torque curve of the motor 7 as a setting signal.

Reference numeral 16 denotes a comparator for comparing the actual load current value from the I / V converter 13 with the load current set value at the time of water drop from the adder 15, and outputs a negative signal when no water drop occurs. Outputs a positive signal when falling. Reference numeral 17 denotes an operational amplifier that amplifies the output of the comparator 16, reference numeral 18 denotes a transistor that is turned on when the output side voltage of the operational amplifier becomes negative, and reference numeral 19 denotes a relay that operates by turning on the transistor 18;
To stop the falling water detection output.

With the above construction, in the construction of the drainage station shown in FIG.
Normal operation at the position higher than the top of the discharge opening 3 ₂ is
Since the signal from the adder 15 is smaller than the signal from the I / V converter 13, the output of the comparator 16 is negative, the output potential of the operational amplifier 17 is positive, and the transistor 18 is
In the FF state, the relay 19 does not operate.

[0013] the water level of the water discharge vessel 2 air from the flap valve 4 decreases from the top of the discharge port 3 ₂ drainage pump in reverse flow within the siphon tube 3 is generated, the pump 6 becomes the same as the no-load operation, Since the signal from the I / V converter 13 becomes smaller, the output signal of the comparator 16 becomes positive and the operational amplifier 1
7, the output side potential of the transistor 7 becomes negative.
When N is reached, the relay 19 operates to output a falling water detection signal, and stop and protect the pump 6.

[0014]

Since the present invention is configured as described above, the following effects can be obtained.

(1) Since it is possible to detect the water drop of the pump and to protect the pump at the time of the water drop, the discharge valve can be omitted in a small-scale drainage pumping station or the like, and only the flap valve can be used.

(2) Since the detection of the water drop of the pump is performed based on the load current and the load torque, the water drop detection circuit can be applied not only to the water drop but also to a constant shaft power control.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a water drop detection circuit.

FIG. 2 is a configuration diagram of a drainage plant utilizing a siphon phenomenon.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Water absorption tank 2 ... Discharge tank 3 ... Siphon pipe 4 ... Flap valve 6 ... Pump 7 ... Pump drive motor 8 ... VVVF device (VVVF inverter) 11 ... Function generator 12 ... CT (current transformer) 13 ... I / V (current / voltage) converter 14 ... Bias setting device 15 ... Adder 16 ... Comparator 17 ... Op amp 18 ... Transistor 19 ... Water drop detection output relay

Claims (1)

[Claims] 1. A method for detecting a water drop of a pump using a siphon phenomenon, wherein a frequency signal of a pump power supply is input to a function generator in which a torque curve of the pump is set and converted into a load-side current signal at the time of pump water drop. A bias signal is added to this signal to set a load current signal at the time of water drop due to the torque of the driving motor. The set load current signal at the time of water drop and the actual load current signal detected by CT and converted into a voltage signal And detecting that the actual load current signal has become smaller than the set load current signal at the time of water drop.