SU1359840A1 - Device for protecting submersible electric motor against overload and "dry running" - Google Patents

Abstract

This invention relates to electrical engineering, in particular, to relay protection. The purpose of the invention is to increase the reliability of the device. In case of overload of the motor over current. Through the time delay determined by the parameters of the circuit: resistor 8 is capacitor 9, the voltage at the inverting input of the comparator 6 exceeds the input potential. At the output of the comparator 6 - switching the trigger 20 to a single state, these are analyzed with the help of an overload light 22. At the output of the element OR 19-1, the output relay is turned off 24. It is kept in the operated state by its contact 25 and acts on the actuator by turning off the electric motor 1. 1 Il. and S O) OO SP with 00 4iib

Description

ten

thirty

The invention relates to electrical engineering and can be used to protect submersible electric motors against overload and disappearance of water in a well (dry run).

The purpose of the invention is to increase the reliability of the device.

The drawing shows the principle of the device.

The device contains three current transformers 1 installed in the phases of the power supply electric motor 2, switched by power contacts 3 of the executive body, three-phase full-wave rectifier 4, potentiometer 5, first 6 and second 7 comparators, first RC circuit from resistor 8 and capacitor 9 with diode 10, 20 shunt resistor 8, a second analogous RC circuit from resistor 11 and capacitor 12 with diode 13, a third RC circuit from resistor 14 and capacitor 15, a parametric stabilizer from resistor 16 and a zener diode .17 connected by parallel inputs For example, for a capacitor 15 of the third RC circuit, the logic elements are NOT 18 and OR 19, the first 20 and second 21 RC triggers, display elements 22 and 23 are connected to the output of which the output of the OR element is connected to the output relay 24, which self-holding its closing contact 25. The first output of the resistor 8 of the first RC circuit with a diode 10 and the connection point 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 5 and the inverting input of the first comparator 6. The second output condensate Ator 9 of the first RC circuit and one of the outputs of rectifier 4 are connected to both (it bus). A second, similar to the first, RC circuit is connected to a melody by an adjustable input of potentiometer 6 and an inverting input of the second 7 comparator, the non-inverting input of which is connected to the output of a parametric stabilizer, the anode of the zener diode 17 of which is connected to the common bus. The resistor 14 of the third RC circuit is connected to the adjustable output of the potentiometer 5. The output of the second 7 comparator is connected to the input of the logical element NOT, the outputs of the first 6 and second 7 comparators are connected respectively to the first and second 15

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To the inputs of the logical element OR 18 and to the inputs of the first 20 and second 21 KS-flip-flops.

Diodes 10 and 13 are designed to discharge capacitors 9. and 12 to potentiometer 5 with a short overload.

The device works as follows.

After closing the power contacts 3 of the executive body, a current flows through the windings of the electric motor 2 and the current transformers 1. Voltage with

5 secondary windings of current transformers are fed to the rectifying bridge 4. From the output of the bridge, the rectified voltage is applied to the potentiometer 5. From the engine of the potentiometer through the integrating resistor 8 circuit, capacitor 9 and resistor 11 are capacitor 12 part of the voltage proportional to the load current, butts To the inverting inputs of the comparators 6 and 7. Simultaneously from the engine of potentiometer 5, through the integrating circuit, resistor 14 - capacitor 15 and parametric stabilizer (ballast resistor 16 - Zener diode 17) - proportional to the load current is supplied to the non-inverting input komparato--. ra -7.

At the rated load current, the voltage at the inverting input of the comparator .6 is less than at its non-inverting input, so there is no voltage at the comparator 6 device. The voltage at the non-inverting input of the comparator-7 determines the voltage stabilization of the Zener diode 13 and is 0.3-0.4 the voltage at its inverting input, so the output of the comparator 7 is the signal 1, and the output of the logic element is NOT 18 - O, postshshayuschy on one of the inputs of the element OR 19, At the output of the element 19 - Oh, the output relay 24 does not work, changing the SRI in the operation of the circuit does not occur.

In case of overload of the motor over current through the time delay determined by the parameters of the circuit, resistor 8 is capacitor 9, on the inverting

5, the input of the comparator 6, the voltage transforms the potential of the input; at the output of the comparator 6-1, the trigger 20 switches to one state, signaled with a lamp 22 o

five

0

five

overload At the same time, at the output of the element OR 19-1, which turns on the output relay 24, which by its contact 25 is kept in the actuated state and acts on the actuator by switching off the electric motor 1.

In the absence of water in the well (dry run), there is a sharp decrease in the current consumed by the electric motor. The time constant of the integrating circuit, resistor 11 — capacitor 12 is much shorter than the time constant of the circuit, resistor 14 — capacitor I5, which serves to detun the inrush currents; therefore, the inverter input of the comparator 7 changes the voltage faster than its non-inverting input. As soon as the voltage on the inverting input becomes less than the voltage on the non-inverting input, determined by the voltage of the stabilization of the zener diode 17, the output of the comparator 7 by vit-0, the output element HE 18 - switches the trigger 21 to one state , signaled by element 23 o on the dry run. At the same time, the output element HE 18 1 enters the input of the element RSH 19, which includes the output relay 24, which is held by its contact 25

to 1 ti

in the actuated state and 35 35

ting on the executive body, disconnecting the motor I.

When regulating the pump flow with a valve, the consumed current also decreases, but since the device reacts to the rate of current change, in this case the device does not respond.

the second comparator, a third RC circuit whose resistor is connected to the regulated terminal of the aforementioned potentiometer, a parametric stabilizer whose inputs are connected in parallel with the capacitor of the third RC circuit, the first and second RC triggers and logic elements OR and NOT , wherein

Thus, by introducing into the device- 45 the non-inverting input of the second company, the OR or NOT device 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 50 comparator and logic element

NOT, are connected, respectively, to the speed at the rate of decrease of the consumed current when water disappears in the well, which allows refusing the use of an electric contact water level sensor in the well and connecting wire to it, and thus

and the second comparator with two RC circuits and a parametric stabilizer connected to its inputs protects the submersible electric motor from dry running, reacting and second inputs of the OR logic gate and inputs of the first and second RC triggers, the display element is connected to the output of each of the 55 , to the output of the logic element OR is connected to the output relay, self-retaining SOBOIM closing contact.

increase the reliability of the protection.

Claims (1)

Invention Formula Device to protect the submersible motor against overload and a dry run containing three current transformers installed in the supply mains phases, a three-phase two-half-cycle rectifier whose inputs are connected to the terminals of the secondary windings connected in a star current transformers, potentiometer, connected to the outputs of the three-phase full-wave rectifier, the first KS circuit with a diode, the first output resistor, shunted by a diode, and the connection point of the second output of the resistor and the first output of the capacitor 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 whose contact is included. the contacts of which are included in the supply mains phases, one of the outputs of the three-phase two-half-period rectifier and the second output of the capacitor of the first RC circuit are connected to the common bus, which differs from the fact that, in order to increase the reliability of the device, the second comparator was additionally introduced into it, the second, analogous to the first, RC circuit with a diode, a power supply, are connected respectively to the first the primary and second inputs of the OR logic element and the inputs of the first and second RC-flip-flops, to the output of each of the 55 of which the display element is connected, to the output of the logic element OR the output relay, self-holding contact with NO, is connected.