Full automation of the electric pump control device. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Power Supplies

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The described device serves for automatic control of any electric pumps, including centrifugal borehole water lifting pumps with submerged electric motors with a power of 1 ... 11 kW and for monitoring the water level in the reservoir and well being filled.

The device is an augmented version of the device "Automatic control of the electric pump", described by A. Kalinsky. Compared with it, the proposed device allows you to automatically respond not only to the water reaching above the permissible level in the reservoir being filled, but also to lowering the water below the permissible level in the well. This will be of great help when placing the electric pump in a well or well with a low water level, or when pumping water from one tank to another when watering from a tank. In addition, it provides control of water levels in the well and reservoir, as well as protection of the pump motor against phase failure of 3-phase motors.

The schematic diagram of the device is shown in Fig.1.

(click to enlarge)

The device contains elements of thermal protection of the pump motor: automatic three-pole switch SF1; heating elements 1RT, 2RT and opening contacts K1.1RT, K1.2RT of the thermal relay; electromagnetic starter K1, including the pump; power supply that converts the voltage "220 V (between phase wire C and neutral wires N) into a constant 9 V; water sensors that control the operation of the device in automatic mode and contain a Schmitt trigger on the elements DD3.1 - DD3.2, an RS trigger on elements DD3.3 - DD3.4, an actuator on transistors VT3 VT4 and relay K2, sensors (electrodes) of the lower water level (LNU) and the upper one (DVU) Capacitors C4 - C7 and the Schmitt trigger are designed to increase the noise immunity of the device.

The device uses a magnetic starter with a coil for a voltage of ~ 380 V, i.e. if phase A or B fails, the pump is switched off. If phase C fails, there will be no voltage of 9 V, therefore, relay K2 will release, and with its contacts K1.1 and K1.2 it will break the power supply circuit of the starter coil, and the pump will turn off.

When switch SF1 is on and switch SA1 is in neutral position, the electric pump is off (relay K2 is de-energized). If it is necessary to work in manual mode, switch SA1 is set to the "Manual" position. (at the top according to the diagram). In this case, relay K2 is activated and with its contacts K1.1 and K1.2 it turns on the magnetic starter.

To switch to automatic mode, the SA1 switch is set to the lower position according to the diagram, while the power supply is switched on, which supplies + 9 V to the water level sensors.

1. If the water in the tank being filled is below the DNU, then the resistance between the DNU, DVU and the tank body is large, and there is a log voltage at inputs 1 DD2.1 and 8 DD2.2. "1".

2. If the water in the well is above the DVU, the resistance between the DVU, DVD and the ground is 1 ... 10 kOhm (depending on the electrical conductivity of the water, which, in turn, depends on the content of salts and various impurities in the water). At inputs 8 and 9 DD1.3 and 12 and 13DD1.4 there is a log voltage. "0".

3. If the conditions of paragraphs 1 and 2 are present, the log level "13" comes to the input S of the RS-flip-flop (pin 3.3 DD0), the level log "8" comes to the input R (pin 3.4 DD1). The trigger is set to a single state, a log "1" is set at output 3.3 of DD1, transistors VT3, VT4 open, relay K2 is activated, which, with its contacts K2.1 and K2.2, closes the power circuit of the coil of the magnetic starter K1, which includes in operation of the electric pump.

4. The pump starts pumping water from the well into the reservoir. In the process of filling, the water reaches the bottom of the reservoir, or the water level in the well is set below the TLD, or both of these conditions are met simultaneously: a log "4" appears at the output 2.3 DD0, and at the input S (output 13 DD3.3) RS- trigger log "1", but the trigger state does not change, the pump continues to pump water.

5. If the water in the tank reaches the DVU or in the well drops below the DNU, the input R (pin 8 DD3.4) of the RS-trigger receives a log. "0", the trigger is set to zero, the level log appears at the output 11 DD3.3 . "0", which closes the transistors VT3, VT4. The relay K2 releases, the starter coil K1 is de-energized, the pump is disconnected from the network.

6. As the water from the reservoir is used, the water is set below the TLD, or in the well rises above the LL, or both of these conditions are met: the RS-trigger does not change its state, and the pump remains off.

7. Only on condition that the water in the tank reaches a level below the LL and in the well - above the LL - the pump is automatically switched on (RStrigger is set to a single state log. "0" at the input S (pin 13 DD3.3).

If during the operation of the electric pump the current through the heating elements 1PT, 2PT flows above the permissible level, the thermal relay is activated and the contacts K1.1PT, K1.2PT de-energize the starter K1. In case of short circuits in the pump motor windings, the SF1 circuit breaker is activated, disconnecting the electric pump from the mains.

Construction and details. As an electric pump, a submersible electric motor for lifting water PEDEV-8 with a power of 8 kW was used, switched by the contacts of an electromagnetic starter with a 380 V coil, in the body of which a TRN-25U3 thermal relay is located.

The heating elements of this relay are connected to two phase wires supplying the electric pump, and the opening contacts are connected in series with the starter winding.

Automatic switch type 1-AP50-3MU3. Instead, you can use A3124 for a trip current of at least 25 A.

To connect the electric motor, use a wire or cable with a core cross section of at least 2,5 mm2. Switch SA1 type P2T-1. Transformer T1 with a power of at least 5 W with a voltage on the secondary winding of 13 ... 15 V. Diodes VD1-VD4 of the KTs405 type with any letter index. Capacitors C1, C4 - C7 type K73-17, C2, C3 type K50-35. Resistors such as OMPT or MPT. K176 series microcircuits can be replaced with K561 series microcircuits. Transistors VT1-VT4 with any letter index. Instead of KT315B (VT1, VT3), you can use KT503, KT3102, instead of KT805BM (VT2, VT4) - KT819 with any letter index. Relay K2-RES9 (passport RS4.5241203, RS4.524.214, RS.524.216, RS4.524.219, RS4.524.229, RS4.524.232). The printed circuit board of the control unit is shown in Fig.2.

Attention! There is a voltage of ~ 220 V on the printed circuit board. When adjusting and repairing, unsolder the wires "K1.2RT" and "phase B".

After adjustment or repair, cover the printed circuit board with zaponlak. On the front cover of the housing, a switch SA1, a fuse FU1 and LEDs HL1 - HL4 are installed, the glow of which indicates that the water has reached the level of the corresponding sensor. The body of the device is connected to the common wire of the power supply and the neutral wire of the network. The neutral wire is grounded.

The tank body is also grounded. If the tank is non-metallic, then a third electrode is installed and grounded on the same bar with level sensors. It should be longer than the lower level sensor. The water in the well or well is securely grounded, and no grounding measures need to be taken.

Corrosion-resistant metal constructions can be used as level sensors: galvanized, stainless steel, aluminum. Do not use metals that have a harmful effect on water, such as copper (this also applies to the supply wires).

Device setup. Without powering the control unit, use resistor R1 to select the current through the zener diode VD5 within 5 ... 10 mA. Set the resistor R2 to +2 V on the emitter VT9, apply it to the device.

Setting up the device consists in selecting the resistances of resistors R4 - R7. To set up, it is necessary: ​​to supply power to the level sensors, in parallel with the capacitor C4, solder a resistor with a resistance of 3 ... 10 kOhm (water equivalent), changing the resistance R4, to ensure that the voltage drop across the water equivalent resistor is 0,5 ... 0,7 V, disconnect the water equivalent resistor - the voltage at terminals 1,2 DD1.1 should be about 9 V. Similarly, select resistors R5 - R7.

During the operation of the device, it is recommended to carry out preventive inspection and cleaning of the level sensors twice a year.

Author: A.N.Mankovsky

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