SU1582265A1 - Device for protection of dc circuit - Google Patents

Abstract

The invention relates to electrical engineering. The aim of the invention is to improve the economy. The goal is achieved due to the fact that if the load current 8 exceeds the permissible value, the signal from the current sensor 9 turns on the semiconductor switch 2, which closes the power supply circuit of the coil of the relay 1, the break contact of which opens and the closure 16 closes. In this state of limiting the current by the first resistor 5, the device will remain until the fault in the load circuit 8 is eliminated. In this case, the difference between the signals at the inputs of the operational amplifier 12 will generate a signal at its output that includes the first thyristor 18, which dampens the semiconductor switch 2 and at the end of the discharge current of the first capacitor 19 itself extinguishes. The absence of a constant signal in the thyristor control circuit increases the efficiency of the device. 1 il.

Description

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31582265

The invention relates to electrical equipment and can be used in protection systems of secondary power sources.

The aim of the invention is to increase efficiency.

The drawing shows a schematic of a device for protecting a constant circuit to a field.

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The device contains a relay coil

1, one pin connected to one pin of a semiconductor key

2, the other terminal of which is intended to be connected to the negative pole of the power source 3, the positive pole of which 4 is intended to be connected to another output of the relay coil 1, the first resistor 5, one output connected to the other - the output of the relay coil 1 and one disconnecting relay 6, another pin 7 of which is connected to another pin of the first resistor 5 and one

a load terminal 8, the other output of which is connected via the current sensor 9 to another output of the semiconductor switch 2, a voltage divider on the resistors 10 and 11 connected between one output of the first resistor 5 and the other output of the semiconductor switch 2, parallel to the active voltage divider 10-11 The operating amplifier 12 is turned on by the power inputs, the inverting input 13 of which is connected to the output of a voltage divider, and the non-inverting input 1 of the operational amplifier is connected to one output of the second resistor 15, the other output of which The third resistor 17 is connected between the output of the operational amplifier 12 and the control electrode of the first thyristor 18, the cathode of the semiconductor switch 2 connected to another output, the second thyristor being used, whose anode and cathode serve respectively and its other terminals, the first capacitor 19 connected between the anodes of the first and second thyristors 18 and 2, the second capacitor 20 connected together with the fourth resistor 21 between the non-inverting operating input preamplifier 12 and the cathodes of the first and second thyristors 18, a fifth resistor 22 connected between the anode

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the first thyristor 1b and the other output of the coil of the relay 1, and the indicator 23 connected in parallel to the coil of the relay t.

The device works as follows.

When the power supply is connected to the input terminals, the operating current goes through the opening contact 6 of the relay, the output load circuit 3 and the current sensor 9. At the rated operating current, the semiconductor switch 2 does not turn on. The first thyristor 18 is also turned off, since the signal at the output of the operational amplifier t2 is zero. Indicator 23 is de-energized. When an overcurrent occurs, the current sensor 9 generates a signal to trigger the semiconductor switch 2. It activates and turns on a relay that opens the power supply with the opening contact 6 and connects the voltage divider 10-11 to the common point of the first resistor 5 and the load 8. First capacitor 19 It begins to charge through the fifth 22 and second 2 thyristors, and the second capacitor 20 through the first 5 and second 15 resistors, the charge time constant of which is longer than the first capacitor 19. This condition ensures reliable operation of the device at Return to the initial state of the load circuit 8, i.e. the first capacitor 19 needs to be charged to a certain potential so that when the first thyristor 18 is turned on, the second thyristor 2 is turned on. Indicator 23, connected in parallel with the winding of relay 1, is energized and signals an overload condition. When the load circuit 8 is restored, the input signal level at the non-inverted input of the operational amplifier 12 becomes higher than at the inverting input, and a high level appears at the amplifier output, which ensures that the first thyristor 18 is turned on, while the second thyristor 2 is quenched by the reverse current of the first the capacitor 19. The relay and the indicator 23 are de-energized, the contact group of the relay switches the input terminal to the output terminal and simultaneously de-energizes the second 15 and fourth 21 resistors, which ensures the removal of a high level from the control is the gate electrode of the first thyristor 18 which goes through the fact that the current through the fifth

the resistor 22 is selected less than the holding current.

The device returns to its original state when source voltage is applied to load 3.

Claims (1)

Invention Formula A device for protecting a DC circuit containing a relay coil, one output connected to one pin of a semiconductor switch, the other pin of which is intended to be connected to the negative pole of the power source, another relay coil pin to be connected to the positive pole of the power source, the first resistor the output connected to another output of the relay coil and the disconnecting contact of the relay, the other contact of which is connected to another output of the first resistor, intended to be connected none of the load pins, a current sensor, one pin intended to be connected to another load pin, and another pin connected to another pin of a semiconductor switch, a voltage divider connected between one pin of the first resistor and another pin of the semiconductor switch, an operational amplifier switched on by inputs power parallel to the voltage divider, you 5Ј22b56 the course of which is connected to the inverting input of the operational amplifier, the non-inverting input of which connected to one output of the second resistor, a third resistor, one output connected to the output of the operational amplifier, and a fourth resistor, characterized in that, with In order to increase efficiency, it is equipped with first and second capacitors, a fifth resistor and a first thyristor, the second thyristor is used as a semiconductor switch, 15a, the relay is provided with a closing contact, with another output of the second resistor connected to the closing contact of the relay, the third resistor with another output connected to the control electrode of the first thyristor, the anode of which is connected to one and the other coil of the relay coil, the anode and cathode of the second thyristor serve respectively as one and the other pins of the semiconductor switch, its control electrode is connected to the output of the current sensor, which is intended to be connected to the load The cathode of the first thyristor is connected to the cathode of the second thyristor, and the fourth resistor is connected between the cathodes of the first and second thyristors and the first output of the second resistor, the second capacitor is connected in parallel with the fourth resistor. 20 25 thirty