RU2309298C2 - Device for protecting electric motor of submersible pump against overloading - Google Patents

Abstract

FIELD: electric engineering.

SUBSTANCE: device comprises three current transformers connected to the power supply, three-phase full-wave rectifier, potentiometer, RC-circuit with diode, first comparator, indication element, output relay, two comparators, and current transformer connected to one of the power source phases. The first output of the transformer is connected with the common bus, and the second output is connected with the inverting input of the second comparator. The inverting input of the third comparator is connected with the phase wire of the same phase. The output of the second comparator is connected with the first input of the 2AND and 2AND-NOT circuits. The output of the 2AND-NOT circuit is connected with the second input of the 2AND circuit whose output is connected with the inverting input of the integrator whose output is connected with the first output of the switch. The second output of the switch is connected with the resistor that is connected with the capacitor and non-inverting input of the repeater whose inverting input and output are connected to the common point that is connected with the second input of the OR circuit and second RS flip-flop whose output is connected with the second indication element.

EFFECT: enhanced reliability.

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Description

The invention relates to electrical engineering and can be used to protect electric motors of submersible electric pumps from the disappearance of water in the well.

A device for protecting a submersible electric pump from “dry running” [1], comprising a “dry running” sensor with make contacts, a DC relay, the first pair of opening contacts of which is included in the power supply circuit of the magnetic starter coil, step-down transformer, rectifier bridge, relay control circuit a direct current is connected to the output of the rectifier bridge, while in parallel with the input of the rectifier bridge is connected a serial circuit from the second pair of NC contacts of the DC relay and the short circuit “dry run” sensor cycles, the input of the rectifier bridge through the quenching resistor is connected to the secondary winding of the step-down transformer, the primary winding of which is connected to the network.

The disadvantage of this device is the low reliability of the water supply in the event of a break in the wire going to the “dry run” sensor, since in this case the electric motor cannot be turned on.

The closest in technical essence is a device for protecting the submersible motor from overload and “dry running” [2], containing three current transformers installed in the phases of the supply network, a three-phase two-half-wave rectifier, the inputs of which are connected to the terminals of the secondary current transformers connected to the star, a potentiometer connected to the terminals of a three-phase half-wave rectifier, the first RC circuit with a diode, the first output of a resistor shunted by a diode, the connection point of the second output res the stator and the first output of the capacitor, which are connected respectively to the adjustable output of the potentiometer and the inverting input of the first comparator, two display elements and an output relay, the contact of which is included in the control circuit of the actuator, the power contacts of which are included in the phases of the supply network, one of the outputs of a three-phase two-half-wave rectifier and the second capacitor terminal of the first RC circuit connected to a common bus, a second comparator, a second, similar to the first, RC circuit with a diode connected between adjustable the output of the potentiometer and the inverting input of the second comparator, the third RC circuit, the resistor of which is connected to the adjustable output of the said potentiometer, a parametric stabilizer, the inputs of which are connected in parallel with the capacitor of the third RC circuit, the first and second RS triggers and logical elements OR and NOT, while the non-inverting input of the second comparator is connected to the output of the parametric stabilizer, the input of the logic element is NOT connected to the output of the second comparator, the outputs of the first comparator and the logic element are NOT are connected respectively to the first and second inputs of the OR logic element and the inputs of the first and second RS-flip-flops, an indication element is connected to the input of each of them, an output relay is connected to the output of the OR logic element, self-holding by its make contact.

The disadvantage is the low reliability for submersible motors with high idle current.

The present invention solves the problem of improving the reliability of the protection of electric motors of submersible electric pumps in the event of the disappearance of water in the well.

To achieve this technical result, in a device for protection against overload and "dry running" of a submersible electric pump electric motor containing three current transformers installed in the phases of the supply network, a three-phase half-wave rectifier, the inputs of which are connected to the terminals of the secondary current transformers connected to the star, a potentiometer connected to the outputs of a three-phase two-half-wave rectifier, an RC circuit with a diode, the first output of the resistor shunted by the diode, the connection point of the second output the torus and the first output of the capacitor, which are connected respectively to the adjustable output of the potentiometer and the inverting input of the first comparator, an indication element and an output relay, the contact of which is included in the control circuit of the actuator, the power contacts of which are included in the phases of the supply network, one of the outputs of a three-phase two-half-wave rectifier and the second output of the RC circuit capacitor is connected to a common bus, two comparators are additionally introduced into the device, a current transformer connected to one of the network phases, one the output is connected to a common bus, the other is connected to the input of the second comparator, the input of the third comparator is connected to a phase wire of the same phase, the output of the second comparator is connected to the first input of logic elements 2I and 2I-NOT, the output of the third comparator is connected to the second input of logic 2I- NOT, the output of which is connected to the second input of the logic element 2I, the output of which is connected to the input of the integrator, to the output of which one output of the key is connected, the second output of the key is connected to the resistor, the resistor is also connected to the cond to the sensor and the non-inverting input of the repeater, the inverting input and output of which are connected to a common point, which is connected to the second input of the OR logic element and the second RS-trigger, the output of which is connected to the second indication element.

The invention is illustrated by two drawings. Figure 1 shows a schematic diagram of a device. Figure 2 shows a diagram of the operation of the device.

The device contains three current transformers 1 installed in the phases of the supply network, and a current transformer 2 installed in one of the phases of the supply network, switched by power contacts 3 of the actuator, an electric motor 4. Three-phase two-half-wave rectifier 5, the inputs of which are connected to the terminals of the secondary connected to the star windings of current transformers 1. Potentiometer 6 is connected to the outputs of a three-phase half-wave rectifier 5, an RC circuit with a diode 7 and a resistor 8, the first output of which is shunted by diode 7, and the point the unity of the second output of the resistor 8 and the first output of the capacitor 9 are connected respectively to the adjustable output of the potentiometer 6 and the input of the first comparator 10, the output of which is connected to the input of the RS-trigger 11, the output of which is connected to the indication element 12. The output of the first, comparator 10 is connected to the first input element OR 13. The output of the logic element OR 13 is connected to the output of the relay 14, which is self-holding by its make contact 15. The other input of the output relay 14 is connected to a common bus. The output of the make contact 15 is connected to the power plus. The contact of the output relay 14 is included in the control circuit of the executive body, the power contacts 3 of which are included in the phases of the supply network. One of the outputs of the three-phase half-wave rectifier 5 and the second output of the capacitor 9 of the first RC circuit are connected to a common bus. The second comparator 16 is connected to a current transformer 2, the third comparator 17 is connected to a phase wire 18 of the same phase. The output of the comparator 16 is connected to the first inputs of the logic elements 19 and 20. The output of the comparator 17 is connected to the second input of the element 20, the output of which is fed to the second input of the logic element 19, the output of which, through the resistor 21, is connected to the integrator 22. Parallel to the inverting input and output the integrator 22 is connected to the capacitor 23 and the key 24, not inverting the input of the integrator 22 is connected to a common bus. An analog memory cell is suitable for the output of integrator 22, the input of which is key 25, the resistor 26 is connected at one end to key 25, and the second to the input of capacitor 27 and the non-inverting input of repeater 28, the output of capacitor 27 is connected to a common bus, the inverting input and output of the repeater 28 are connected to a common point, which is the output of the analog memory cell. The second input of the OR logic element 13 and the input of the RS-trigger 29, to the output of which an indication element 30 is connected, are connected to it.

The device operates as follows.

After the power contacts 3 of the actuator are closed, current flows through the windings of the electric motor 4 and current transformers 1 and 2. The voltage from the secondary windings of the current transformers 1 is supplied to the rectifier bridge 5. From its output, the rectified voltage is applied to the potentiometer 6. From the potentiometer 6 through the RC circuit, the resistor 8 is the capacitor 9, part of the voltage proportional to the load current is applied to the inverting input of the first comparator 10. At the same time, current and phase voltage are supplied from the current transformer 2 and the phase wire 18 to the inverting inputs of the comparators 16 and 17, respectively.

At a rated load current, the voltage at the inverting input of the first comparator 10 is less than at its non-inverting input, so there is no voltage at the output of the first comparator 10.

Current and voltage (curves 1 and 2, FIG. 2) are supplied to comparators 16 and 17, with the help of which rectangular pulses are obtained (curves 3 and 4, FIG. 2). Logic elements 19 and 20 convert two input signals into rectangular pulses, the width of which is proportional to the angle of the phase shift between current and voltage (curve 5, figure 2). Using the integrator 22, the obtained pulses are integrated (curve 6, Fig. 2), and the analog memory cell, executed on the repeater 28, carries out a voltage change (curve 7, Fig. 2). The device works when changing the angle from 0 to 90 °. When there is water in the well, the output relay 14 is supplied with a voltage insufficient for its operation.

When the motor is overloaded by current through the time delay determined by the parameters of the RC circuit, the resistor 8 is a capacitor 9, at the non-inverting input of the first comparator 10, the voltage exceeds the input potential, at the output of the first comparator 10 is “1”, which switches the RS-trigger 11 to a single state signaling with lamp 12 about overload. At the same time, at the output of the OR element 13 - “1”, including the output relay 14, which is held in contact 15 by the contact 15 and acts on the actuator, turning off the electric motor 4.

With the disappearance of water in the well, a sharp decrease in the reactive component of the phase current occurs, thereby changing (increasing) the angle between the current and voltage, as a result of which a higher voltage is applied through the integrator, which leads to the operation of the output relay 14, which is maintained by contact 15 and operates to the actuator, turning off the electric motor 4. At the same time, the RS-trigger 29 is triggered, including the indication element 30, indicating the occurrence of "dry running".

Information sources

1. RF patent No. 2184414, Н02Н 7/08, 7/093, 2002, B No. 18 (II h).

2. A.S. USSR No. 1359840, Н02Н 3/08, 3/12, 1987, B No. 46 - prototype.

Claims (1)

A device for protecting the submersible motor against overload and "dry running", containing three current transformers installed in the phases of the supply network, a three-phase two-half-wave rectifier, the inputs of which are connected to the terminals of the secondary windings of the current transformers connected to the star, a potentiometer connected to the outputs of the three-phase two-half-wave rectifier, the first RC circuit with a diode, the first terminal of the resistor shunted by the diode, and the connection point of the second terminal of the resistor and the first terminal of the capacitor, which are connected respectively to the regulated output of the potentiometer and the input of the first comparator, the output of which is connected to the first input of the OR logic element and to the first RS-trigger, to the output of which an indication element is connected, the output of the OR logic element is connected to the output relay, the contacts of which are connected to the executive control circuit body, the power contacts of which are included in the phases of the supply network, after the power contacts of the executive body are closed, current flows through the motor windings and current transformers, one of the the outputs of the three-phase two-half-wave rectifier and the second capacitor output of the first RC circuit are connected to a common bus, characterized in that two comparators are additionally introduced into it, a current transformer connected to one of the network phases, one output is connected to a common bus, the other is connected to the input of the second comparator, the input of the third comparator is connected to a phase wire of the same phase, the output of the second comparator is connected to the first input of logic elements 2I and 2I-NOT, the output of the third comparator is connected to the second input of the logic element that 2I-NOT, whose output is connected to the second input of the 2I logic element, the output of which is connected to the integrator input, to the output of which one key output is connected, the second key output is connected to the resistor, the resistor is also connected to the capacitor and non-inverting input of the repeater, the inverting input and the output of which is connected to a common point, which is connected to the second input of the OR logic element and the second RS-trigger, the output of which is connected to the second indication element.

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