SU1684740A1 - Device for constant checking insulation of d c chains - Google Patents

Abstract

This invention relates to electrical measurements and can be used to monitor direct current circuits. The purpose of the invention is to increase the sensitivity in the symmetric control of the insulation resistance and to enable self-control through the use of two transistor current amplifiers and a double-winding relay. The relay is achieved by the fact that a device containing a transistor 2, a relay 3, resistors 7 ... 10, zener diodes 4, 5, a transistor 1, resistors 6, 11, 12, milliammeter 13, buttons 14, 15, and relay 3 is implemented double winding. 1 il. 9 (L

Description

The invention relates to electrical measurements and can be used to monitor the insulation of direct current circuits, in particular, the protection and control circuits of mine hoisting machines, operational current circuits of electrical substations.

The aim of the invention is to increase sensitivity with symmetric monitoring of the insulation resistance and to enable self-control through the use of two transistor current amplifiers connected in a differential circuit and a two-winding relay.

The drawing shows a diagram of the proposed device.

The device contains a differential current amplifier with two transistors 1. 2. two-winding relay 3, zener diodes 4.5, ballast resistor 6, resistors 7 ... 12, milliammeter 13, buttons 14, 15 and contacts 16 of two-winding relay 3, with the emitters of transistors 1, 2 are connected respectively to the second and first inputs of the device, their collectors through the first and second windings of the two-winding relay 3, respectively, with the first and second terminals of the ballast resistor 6, and

1 base - with the combined pins of resistors 7, 8 and 9, 10, respectively,

the Zener diode 4, the second output of the resistor 7 and the first output of the resistor 11 are connected to the second input of the device, the first input of which is connected to the anode of the Zener diode 5, the second output of the resistor 10 and the first

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the output of the resistor 12, the anode of the Zener A and the cathode of the Zener diode 5 are connected respectively to the first and second terminals of the ballast resistor 6, the second terminals of the resistors 11, 12 are connected to the common bus through buttons 14, 15 respectively, the second terminal of the resistor 9 is connected to the common bus, which The milliammeter 13 is connected to the second output of the resistor 8, the contacts 16 are connected respectively to the first and second outputs of the device.

The device works as follows.

The first and second inputs of the device are connected respectively to the negative and positive levels of the controlled circuit. Through the Zener diodes 4, 5 and the resistor 6 the current flows, creating on the Zener diodes 4, 5 the supply voltage of the collector circuits of transistors 1, 2. The loads of the collector circuits of transistors 1, 2 are windings of a two-winding relay 3. The control current of the base circuits of transistors 1, 2 flows through the emitter-base junction of transistor 1, resistor 8, milliammeter 13, resistor 9 and base-emitter junction of transistor 2. The base current is chosen so that the collector circuits of transistors 1, 2 receive currents equal to half of the maximum collector molecular weight for a given circuit current. Resistors 7, 8 are designed to reduce the dependence on temperature fluctuations. The magnetic fluxes of both windings of the two-winding relay 3 must be directed oppositely, while its contacts 16 are open and the readings of the milliammeter 13 must be at half the scale. When the isolation resistance of the positive bus of the monitored circuit decreases or when the button 14 is pressed, the base current of transistor 1 decreases and the milliammeter 13 shows a lower current, while the base current of transistor 2 increases due to a decrease in resistance between the positive bus of the controlled circuit and the common bus. the current in one of the windings of the two-winding relay 3 decreases and increases in the other, which leads to the operation of the two-winding relay 3 and the closure of its contacts 16 connected across the outputs alarms for alarm and blocking

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povki. By reducing the insulation resistance of the negative bus of the monitored circuit, the device operates similarly with the difference that the base current of transistor 1 increases and that transistor 2 decreases.

Claims (1)

Thus, due to the use of a double-winding relay and the differential switching on of transistor current amplifiers, the sensitivity of the device is increased and symmetric control of the insulation resistance of both buses of the monitored circuit is achieved, as well as the possibility of self-control of the device. Invention Formula A device for continuous monitoring of isolating DC circuits containing a relay, a transistor, four resistors, the base of the transistor being connected via the first and second resistors to a common bus and the first input of the device, the second input of which is connected This is due to the fact that, in order to increase the sensitivity with the symmetrical control of the insulation resistance and enable self-control, two Zener diodes are introduced into it, the second transistor, three resistors, two buttons, a milliammeter, and a relay are double-wound, with the emitters of the first and second transistors respectively connected to the first and second inputs of the device, their collectors through the first and second windings of the two-winding relay and the cathode of the first and the anode of the second Zener diodes, the anode of the first Zener diode and the first output of the sixth resistor are connected to the first input of the device, the cathode of the second Zener diode and the first output of the seventh resistor are connected to the second The second input of the device, the base of the second transistor is connected to the first terminal of the fourth resistor, the second terminal of which is connected via a milliammeter to the common bus, which is connected to the second terminals of the sixth and seventh resistors through the contacts of the first and second buttons, respectively, and the open contacts of the two-winding relay are respectively g the first and second outputs of the device. -tb-. ,