SU1224412A1 - Arrangement for chamber-less checking of electric circuits for spark safety - Google Patents

Description

The invention relates to devices used to measure the intrinsic safety of electrical circuits of automation and remote control systems used in mines that are hazardous to gas or dust, and in explosive rooms of chemical, gas and petroleum industries.

The purpose of the invention; This is an improvement in the accuracy of the evaluation of circuits for spark safety by reproducing changes in current and voltage in the course of a discharge over the entire range of (speeds) two-contact contacts.

Pa drawing shows the functional scheme of the proposed device.

The device consists of 1.2 current sources, two khauchevye elements 3 and f, two operational amplifiers 5 and b, a store of 7 capacitors, a voltage divider 8, a transistor 9, a TOica limiter in the B-16 of resistors 10-13,. the test circuit 14, the multiplier 15, the integrator 16, the analog-digital converter 17, the digital indicators 18 and 19, the counter 20, the coincidence unit 2, the comparator 22, the generator 23. i The p-works the device as follows. .

The switches 3 and-4 are previously open, the voltage at the input of the operational amplifier 5, at the output of the target 8 voltage, and at the output of the operational amplifier 6 is zero. Transistor 9 is open and through its count; The lecturer-emitter junction is flowing the current of the subject 14, almost equal to the short-circuit current.

After switching the keys 3 and 4 to the inputs of the operational amplifiers 5 and 6, currents of current sources 1 and 2 arrive. The flow of current from current source 2 to the input of operational amplifier 5 leads to a linear increase in voltage at its output, and the growth rate is determined by the capacity of the magazine 7 capacitors . This is for example - Up enters the inputs-divider 8 of the voltage and the operational amplifier b. The voltage of the resistor 13, which is proportional to the current of the circuit under test, is applied to the B7 OI input of the voltage divider 8. As a result, at the output of the voltage divider 8, a voltage is generated, increasing in

one

and inversely proportional

50

j o

five

five

0

current ip. At the input of the op-amp b, due to negative feedback through the resistor 11, the currents flowing through the resistors 10 and 12, as well as from the current source 2, sum up the voltage jump U. Thus, a voltage is generated on the collector of transistor 9. voltage corresponding to the arc discharge current-voltage characteristic.

The voltage of the collector of the transistor 9 is fed to one of the inputs of the multiplier 15, to the second input of which voltage is applied from the current measuring resistor 13. The output voltage of the smart-resistor, which is proportional to the discharge power, is fed to the input of the integrator 16 , at the output of which a voltage proportional to the discharge energy appears. This voltage is converted by analog-to-digital converter 17 to a digital code and is indicated by a digital indicator 18,

From the output of the amplifier 15-1, the voltage is applied to the comparator 22, which ensures the noise immunity of the duration meter. When the input signal exceeds the threshold of the comparator operation, a signal appears at its output, which opens a block 21 of the match, which leads to the appearance of pulses from the generator 23 at its output. These pulses go to the input of the digital counter 20 and are indicated by a digital indicator 19. The open time of the coincidence circuit determines the duration of the discharge.

Thus, the device makes it possible to increase the accuracy and reliability of the estimate by reproducing the current-voltage characteristic of the real discharge and measuring the discharge energy by integrating its power, as well as by measuring the energy over the entire range of contact speeds.

To assess the intrinsic safety of electrical circuits, it is sufficient to determine the dependence of the energy emitted from the chain in the discharge, minus the cathode losses from the duration of the discharge and the speed of movement of the contacts B-match it with the corresponding

freezes-1 for flammable energy. The circuit is considered intrinsically safe, if the value of the discharge energy in the entire possible range of contact speeds remains less than the igniting energy.

In the proposed device, obtaining the dependence of the energy introduced from the circuit to the discharge) on the duration of the discharge and the speed of movement of the contacts is provided by connecting to the terminals of the test circuit a nonlinear resistance with a current-voltage characteristic corresponding to the current-voltage characteristic of the arc discharge . This volt-ampere ha

 j

12244124

Characteristics can be described by razheniem

aVt +

V

UK +

 Vt h

where Uj, is the cathode voltage drop; a, b - characteristics coefficients;

V is the contact speed;

Up- voltage on discharge;

ip is the discharge current.

The use of a device allows one to obtain the law of voltage variation Up in the entire possible range of contact speeds, as well as sufficiently accurately measure the duration of the process and the energy applied to the nonlinear resistance.

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R

. Compiler I.Nazarkina Editor M.Kelemesh Tehred G.Gerber Proofreader V.Sinitska.

Order 1900/29 Circulation 436Subscription

VNIIPI USSR State Committee: for inventions and discoveries

113035, Moscow, Zh-35, Raushsk nab. 4/5

. Goproizvodishh about the printing company, Uzhgorod, Projecto st., 4

Claims (1)

DEVICE FOR TUBERLESS EVALUATION OF ELECTRICAL CIRCUITS FOR INTRINSIC SAFETY, comprising a discharge duration meter, a discharge energy meter and current limiters, characterized in that, in order to improve the accuracy of the evaluation of circuits for intrinsic safety, it is equipped with two key elements, two operational current amplifiers, , a voltage divider, a transistor, a capacitance magazine and a multiplier, moreover, the discharge energy meter consists of a series-connected integrator, an analog-to-digital converter the expander and the first digital indicator, and the discharge duration meter consists of a comparator, a coincidence unit, a counter, a second digital indicator and a generator, the output of which is connected to the first input of the coincidence unit, to the second input of which a comparator is connected, the output of the coincidence unit through the counter is connected to the second digital indicator, and the outputs of the current_ sources are connected to the inputs of the key elements, the output of the first of which is connected to the first output of the store of capacities and to the negative input of the first operational amplifier, the positive input of which is connected to the neutral bus power source and the output to the second terminal of a capacitance, to a first input of the voltage divider directly and through a first current limiter to the positive input of the second operational amplifier, _a negative input of which is connected to the neutral bus power source, and the output is to the base of the transistor, the emitter of which is connected to the zero bus of the power source, and the collector is connected to the positive bus of the circuit under test, the negative bus of which is connected to the primary the second terminal of the current limiter and the second input of the voltage divider, the second terminal of the second current limiter is connected to the zero bus of the power supply, the output of the voltage divider through the third current limiter is connected to the positive input of the second operational amplifier and the input of the second key element, which is also connected through the fourth current limiter to the positive bus of the tested circuit, and the multiplier inputs connected to the positive and negative buses of the tested circuit, and you: by the way - to the inputs of the integrator and compar torus. SU,., 1224412 1 1224412