SU434173A1 - DEVICE FOR SEPARATION OF DIFFERENT AND DIFFERENT ELECTRIC CHAINS - Google Patents

Description

This invention relates to explosion-proof electrical equipment.

The known devices for separating spark-proof and intrinsically safe electrical circuits, containing a two-stage transistor amplifier in a flameproof enclosure, the input stage of which is connected to unsafe sources and the output spark-safe, transfer significant powers to emergency circuits.

The described device does not have this disadvantage due to the fact that it is equipped with diodes and limiting resistors included in the collector circuits of both transistors, and the emitter of the transistor of the first stage through the diode in the forward direction is connected to the emitter of the transistor of the second cascade point of the positive pole of the spark-proof power source and the negative pole of the spark-safe source of bias, the positive pole through the diode in the forward direction and a resistor connected to the base of the second transistor stage, whose collector is via a diode in the reverse direction is connected to the output terminal. The flameproof enclosure is connected through the diode in the forward direction to the emitter of the input stage transistor and through the diode in the opposite direction to the negative pole of the intrinsically safe power source.

The drawing shows a schematic diagram of the described device.

It contains spark-ignition sources 1–2, diodes 3–11, resistors, transistors 18–19, intrinsically safe sources 20–21, terminals 22–25 of intrinsically hazardous circuits, and we are 26–29 intrinsically safe circuits.

The device works as follows.

When a negative signal from an intrinsically safe source 20 is applied through terminal 27 to the base of transistor 19, the latter opens 5 seconds and removes the control signal from the input of transistor 18. Transistor 18 closes and a signal that controls the elements spark-safe appears at the device output (terminal 23) parts of the equipment. 0 In the normal mode, the device eliminates the output of power from spark sources to intrinsically safe circuits, since the oppositely connected diodes 6, 7, 10 and 4.8 completely separate the intrinsically safe circuits, not 5 preventing the signal from the input of the device to the output terminal. 22

Separation of intrinsically safe and spark-safe circuits in emergency modes (polarity reversal of sources, breakdown of transistors, interruption of their 0 circuits, simultaneous short circuit to ground and

flameproof enclosures in intrinsically safe spark-proof circuits, or any combination of these violations) is carried out using faultless diode-resistive circuits. In particular, protection against polarity reversal of sources along with the previously mentioned diodes is performed by diodes 3-5. During the breakdown of transistors 18, 19 and at the break of their emitter and collector circuits, power output from a spark source to the intrinsically safe circuits is also excluded, since in these modes counter-connected diode circuits prevent the passage of current from spark sources to the intrinsically safe circuits. In a number of emergency modes, a spark-proof source supplies insignificant power to an intrinsically safe circuit. In particular, one of these most severe modes occurs during the breakdown of transistor 18 and at the same time the terminals 25, 28 close to ground and the clamp 24 is broken. In this case, a current flows between terminal 28 and the ground, the value of which is determined by the voltage of sources 1, 2 and the resistance value of the resistor 13 (usually several). However, the magnitude of the output voltage in this mode does not exceed the direct voltage drop across diode 11, i.e., the power of this circuit is small.

In other similar emergency modes, in particular when earth loops of terminals 26 and 22, the power supplied by intrinsically safe sources to intrinsically safe circuits is limited by a resistor 15 and a diode 9.

Reducing the power delivered by intrinsically safe circuits to intrinsically safe circuits allows an increase in the number of links between intrinsically safe and intrinsically safe circuits.

Subject invention

A device for separating spark-proof and spark-proof electrical circuits, containing a two-stage transistor amplifier in a flameproof enclosure, the input stage of which is connected to the spark-proof sources, and the output-hazardous circuit, characterized in that, in order to reduce the power delivered by the spark-proof sources to the spark-proof circuits in hazardous sources, the hazardous sources in hazardous circuits are reduced in hazardous sources in hazardous sources. it is equipped with diodes and limiting resistors included in the collector values of both transistors, with the emitter of the first stage transistor A diode in the forward direction is connected to the emitter of the transistor of the second stage, through the diode in the opposite direction connected to a common point, the positive pole of the spark-proof power source and the negative pole of the spark-proof bias source, a positive pole through the diode in the forward direction and a resistor connected to the base of the second transistor cascade, the collector of which through the diode in the opposite direction is connected to the output terminal, while the flameproof enclosure is connected through the diode in the forward direction to the emitter of the input stage transistor and through the diode in the opposite direction - with the negative pole of an intrinsically safe power source.

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