SU1523923A1 - Method of monitoring spark-quenching capacitive shunts - Google Patents

Abstract

The invention relates to electrical engineering and can be used in the development and monitoring of the effectiveness of spark-arresting capacitive shunts. The purpose of the invention is to increase the reliability of the control. The voltage arising from the opening of the load circuit is measured over a period of time not exceeding the plasma deonization time of the electric discharge, and the load circuit is switched with a frequency and duty cycle corresponding to real devices. The measured voltage is compared with the ignition voltage of the discharge and, if the first is less than the second, the conclusion is made about the effectiveness of the control object, and if vice versa - about its inefficiency. 1 il.

Description

The invention relates to electrical engineering and can be used in enterprises that develop and manufacture intrinsically safe equipment, as well as in state control organizations controlling spark safety.

The aim of the invention is to increase the reliability of monitoring the effectiveness of spark-extinguishing capacitive shunts by repeatedly switching an electrical circuit with a real frequency and duty cycle and measuring the voltage on a shunt capacitor at the time of switching

The drawing shows a diagram of the device that implements the proposed method.

The device contains a power source 1, a capacitor 2, a controlled resistor (transition of the transistor) 3, a load inductance k, a capacitor 5, a master oscillator 6, element 7, a pulse width driver 8 (PDI), a limiting resistor 9, a comparator 10, a trigger 11 , resistor 12, button 13, transistor switches I and 15, LEDs i6 and 17, and power supply 18.

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Moreover, the first output of the first power source 1, shunted by capacitor 2, is connected to the common bus, its second output is connected through the load inductance, shunted by capacitor 5, connected to the forward input of the comparator 10 and through a controlled resistor 3rd common bus output of the master oscillator 6 is connected To the first input element AND 7, the output of which is connected to the input of the FDI 8, whose output through the resistor 9 is connected to the control input of the controlled resistor 3 and to the gate input of the trigger 11, the inverse of the comparator 10 is connected the reference voltage source Ug, and the output of the comparator 10 is connected to the information input of the trigger 11, the initial installation input of which is connected to one of the pins of the button 13 and through the resistor 12 to the common bus, the second output of the button 13 is connected to the positive bus of the power supply 18, with which the anodes of the LEDs 1b and 17 are also connected, the cathodes of which through transistor switches 1 and 15, respectively, are connected to the common bus and to the negative bus of the power supply 18, which controls the input of the transistor switch 1, are connected to the forward output of the trigger 11, nversny whose output is connected to a control input of the transistor switch 15 and a second input of AND gate 7.

The method is implemented as follows.

In the steady state, the transistor 3 is open due to the fact that at its base a positive voltage is maintained and the collector-emitter junction resistance of the open transistor 3 is one ohm.

Through the load inductance k, a current flows, the magnitude of which is determined by the parameters of power supply 1, capacitors 2 and 5 are charged up to the voltage of power supply 1, the voltage at the direct input of comparator 10 relative to the common wire is close to zero,

The output of the comparator 10 is set to log level. ABOUT.

When the circuit is opened (the transistor 3 is locked), two cases are possible: during the time Tr of plasma deionization, the discharge voltage is collector-emitter

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five

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five

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five

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transistor 3 exceeds the ignition voltage U of the arc, and for the time Tp the collector-emitter voltage of transistor 3 does not reach UQ. In the first case, the inefficiency of a capacitive shunt (capacitor 5) is indicated, since these conditions of real switching when the voltage across the contacts (simulated by the transition of the transistor 3) is large and during the time Tr, conditions appear for arc ignition and spark-proof.

In the second case, the efficiency of a capacitive shunt is indicated.

When a trigger pulse from the master oscillator 6 is fed, the FDI 8 generates a pulse at its output, the duration of which is determined by the ratio R and C and is chosen equal to the plasma deionization time Tr.

At the pulse time, the transistor 3 closes, the resistance of its transition to the collector emitter increases to tens of a kilo.

The surge voltage of the self-induction inductance of the load recharges the capacitor 5. The duration and amplitude of the surge depend on the capacitance of the capacitor 5. After Tp (deionization time of the discharge plasma), FDI 8 returns to its original state and its O – 1 drop builds recording the state of output of comparator 10 to trigger 11. If, after the time T has expired, the voltage at the collector of transistor 3 does not have time to reach the value Up (arc firing voltage), the comparator 10 does not go into the Log state. 1 and the trigger 1 O is written to the output of the trigger

Log O. On the forward 11, the log remains. ABOUT.

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and on the inverse

Log 1. At the same time through the open transistor switch 15 (transition emitter-collector) current flows, causing the glow of the LED 17, indicating the efficiency of the capacitive shunt.

If, after the time T has expired, the voltage on the collector of the transistor 3 exceeds the value of Up, the comparator 10 goes to state 1 and the logical unit is written to the trigger 11, the Log appears on the forward output of which. T

and on the inverse - Log. O. Transistor switch 15 closes and transistor switch 14 opens, LED 17 goes out and LED 1b lights up, indicating that the capacitive shunt o Log, O is ineffective at the inverse output of trigger 11, and the next triggering pulses for FDI 8 input. Trigger 11 is reset to the initial state by pressing button 13. When it is pressed, trigger 11 is cleared and a Log is set at its inverse output. 1, allowing the passage of trigger pulses from the master oscillator 6.

When applying trigger pulses of the master oscillator 6 with the frequency and duty cycle of a real switching device, there are cases when the subsequent opening occurs before the completion of the transient processes caused by the previous one.

For example, if the shunting load inductance of the capacitor 5 does not have time to charge before the voltage of the subsequent triggering pulse before the voltage of the power supply 1, in this case, when the transistor 3 is closed, the voltage Ug at the collector-emitter junction can occur immediately, which causes real switching device arcing and sparking violation. The inefficiency of the capacitive shunt in this case is fixed as in the previous one. After time Tp, the positive pulse difference from the FDI 8 output enters into the trigger 11 the state of the comparator 10, corresponding to and "(Log. 1), where and is the collector-emitter voltage of the transistor Up - arc ignition voltage (reference voltage of the comparator 10) , the transistor switch I opens, the 1b LED lights up, indicating the inefficiency of the capacitive shunt,

Thus, in comparison with the known proposed technical solution, by ensuring the voltage control on the shunt capacitor through the plasma deionization time of the discharge, it is possible to increase the reliability of the control of the spark-extinguishing shunts and ensure the intrinsic safety of the devices, eliminating the possibility of using defective means of protection in explosive environments. In addition, the method allows for the prompt selection of optimal parameters of spark protection devices.

Claims (1)

Invention Formula The method of controlling spark-suppressing capacitive shunts, based on the voltage that occurs when switching the load circuit, is different, and in order to increase the reliability of the control, additional resistance is connected in series with the load, which is periodically short-circuited by a time corresponding to the frequency and the duty cycle of the commutation of the load circuit by a real switching device; in each period the voltage is measured at the additional resistance after a period of time not exceeding the deionization time plasma discharge, compare the measured voltage with the ignition voltage of the discharge and, if the first is less than the second, make a conclusion about the effectiveness of the object control, if on the contrary - about its inefficiency. Editor N. Bobkova Compiled by V. Bykov Tehred M. KhodanychKorrektor L. Beskid Order 7033 / Circulation 660 VNIIPI State Committee for Inventions and Discoveries at the State Committee on Science and Technology of the USSR 113035, Moscow, Zh-35, Raushsk nab. 4/5  - - - - - - - - - - - - - - - - - - - - “". "- - -.". - - „-. Production and Publishing Combine Patent, Uzhgorod, st. Gagarin, 101 Subscription