SU1500793A1 - Arrangement for spark-proofing data and power d.c. circuits of current-to-voltage converters - Google Patents

Description

The invention relates to explosion-proof electrical equipment and can be used in information and power supply circuits of direct current converters current-voltage. The purpose of the invention is to increase reliability. The goal is achieved by the fact that in the intrinsically safe circuits of the device, connected to the primary converter 9 and shunt by zener diodes 10, 11, a current limiting resistor 12 and a torus 13 are installed, which simultaneously performs the functions of a current-voltage converter and a current limiter. In this case, the resistor 13 through the information circuit resistor 12 is shunted by the zener diode 10 of one of the protection nodes.

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The invention relates to explosion-proof electrical equipment and can be used in information and supply circuits of direct current-voltage converters.

The purpose of the invention is to increase reliability.

The drawing shows the principal circuit diagram of the device for spark protection.

Device 1 for spark protection contains two identical nodes of protection. Current limiting resistors 2, 3 15

and fuses 4, 5 installed in the intrinsically safe circuits are connected to the power supply 6 and the amplifier 7 of the secondary device 8. In the intrinsically safe circuits of the device, connected 20 to the primary converter 9 and shunt zener diodes 10 and 11, a current limiting resistor 12 is installed, as well as a resistor 13 acting as a current transducer - 25

voltage and current limiter. In this case, the resistor 13 of the power supply through the resistor 4 of the information circuit is shunted by an additional zener diode 10, which is switched on opposite to the power supply of Zener diode 11.

The device works as follows.

In normal operation, the current 35 of the power source 6 flows through a series circuit: the source

6 power supply, resistor 13, primary converter 9, current-limiting resistor 3, fuse 5, 40

power supply 6. When the monitored parameter changes, the resistance of the primary converter 9 changes, and consequently, the current in the circuit under consideration. Change 45 current is converted by resistor 13 into a proportional voltage change, which through resistors 12, 2 and fuse 4 is fed to the input of the amplifier 7 of the secondary device 8.

In emergency mode, when injected into the spark-induced overvoltage circuit from the secondary device 8, the current in the intrinsically safe circuits is limited by resistors 12 and 13, and 55 the voltage - by zener diodes 10 and 11.

In turn, the current through the zener diodes is limited by resistors 2 and 3, and the power released by the last

and zener diodes 10 and 11, - fuses 4 and 5.

Leakage through the Zener diode 11, which acts as a voltage limiter in the supply circuit, does not affect the metrological characteristics of the signal, since the leakage current is summed with the supply current, and not the information signal. Resistors 12, 2 and zener diode 10 of the information circuit also do not affect the reliability of information transmission, since resistors 12 and 2 can be made highly accurate (0.1: 0.05%) and high-resistance, and the response voltage of the Zener diode Yu can be chosen with large stock that allows you to be "far" in its pre-breakdown area, where the magnitude of leakage currents is negligible. In addition, when the resistance of the resistor 13 is broken, the voltage across the information circuit to the intrinsically safe circuit from the damaged amplifier 7 does not exceed the response threshold of the Zener diode 10. Due to the counter-switching of the Zener diode 10 in relation to the Zener diode 11, even when the voltages of the secondary device 8 , the voltage in the intrinsically safe circuit can not be higher than the sum of the direct voltage drop at one of the Zener diodes and the threshold of the other. This increases the reliability and significantly expands the functionality of information devices, as can be increased the length of the connecting lines and capacitors, included in the electrical circuit diagram of the primary converter 9.

Claims (1)

Claim A device for spark protection of information and power supply DC circuits of current-voltage converters containing the first Zener diode, the first, second and third resistors, the first and second fuses, the first terminals of which have the first and second terminals for connecting the first information circuit and the power supply minus . device, the second output of the first fuse is connected to the first output of the first resistor, the first output of the second resistor has a third five 1500793 the terminal for connecting the first spark-safe circuit; the second terminal of the second resistor and the cathode of the first Zener diode have a fourth terminal for connecting the second information circuit and the power supply circuit of the secondary device; the second terminal of the second fuse is connected to the first terminal of the third resistor, the second terminal of which and the anode of the first Zener diodes have a fifth terminal for connecting 6 the second intrinsically safe circuit, due to the fact that, in order to increase reliability, a second Zener diode and a fourth resistor are added to it, the first terminal of which is connected to the third terminal, the second terminal of the fourth resistor is connected to the second terminal of the first u resistor and the anode of the second Zener diode, the cathode of which is connected to the fourth terminal.