SU1751360A1 - Method of testing electric circuits for spark safety - Google Patents

Abstract

Electrical equipment explosion-proof with a type of explosion protection Intrinsically safe electrical circuit. GOST 22782 5-78. USSR Author's Certificate No. 1137414 Cl. G 01 R 31/02 1985

The essence of the invention is to control the completion of a transient process in a circuit by controlling the absence of current frequency and voltage other than the frequency of the supply voltage, and switching the circuit outside the potentially explosive environment at the end of the transient process, and resetting the circuit explosive environment after a period of time exceeding the ignition time of the gas mixture 2 silt

Description

The invention relates to the mining industry and can be used to assess the intrinsic safety of electrical circuits during their technological switching or emergency breakage and short circuit.

The aim of the invention is to improve the performance of the test.

The essence of the invention is to control the completion of the transient process in the circuit by controlling the absence of the current frequency and voltage, which is different from the frequency of the supply voltage, and the switching of the circuit takes place at the end of the transient process.

Figure 2 presents a basic test circuit for an inductive circuit; figure 2 - the same for the capacitive circuit.

The circuit contains a power source 1, in the communication line with a load 2 of which a spark-forming mechanism 3 and an additional switch 4 are connected, a device 5 generating a signal in the absence of frequencies different from the frequency of a steady-state current or voltage, and a time setting device 6

When testing the active-inductive circuit, the spark-forming mechanism 3 is connected in series with source 4 and load 2 and is shunted by an additional switch 4, and device 5, which generates a signal in the absence of a current frequency different from the frequency of the steady-state current, is connected in series with the load.

During the testing of the active-capacitive circuit, the spark-forming mechanism 3 is connected to an additional switch 4 connected in parallel with the power source 1 and the load 2. Parallel to the load 2, the device 5 is also connected, which generates a signal in the absence of voltage frequencies

r ss

other than voltage frequency in steady state mode.

The tests of the active-inductive circuit are as follows.

In the closed state of the additional switch 4, the device 5 monitors the completion of transients by monitoring the frequency of the current in the circuit. At the completion of transients, device 5 generates a signal arriving at switch 4, which opens its contacts, and device b, which starts timing and turns off transient control. After a predetermined time, not less than the ignition time of the gas mixture, the device b generates a signal, which switch 4 switches to the initial state, switches on the transient control device 5 and returns to the initial state.

Test circuit with active-capacitive load produced as follows.

When the contacts of the additional switch 4 are open, the device 5 monitors the completion of transients by monitoring the voltage frequency in the circuit. Upon completion of the transients, device 5 generates a signal arriving at switch 4, which closes its contacts, and device 6, which starts timing and turns off transient control after the specified time has elapsed, not less than the gas ignition time

The device binds the signal, which switches the switch 4 to the initial state, turns on the transient control device 5 and returns to the initial state, after which the cycle repeats.

Monitoring the completion of transient processes in the circuit and the connection of the spark device to the test circuit immediately after their completion allows simultaneously improving the performance of the circuit test and the reliability of the test results.

Claims (1)

Invention Formula The method of testing electrical circuits for intrinsic safety, based on switching the tested circuit by a spark-forming mechanism placed in an explosive environment, and simultaneously switching this circuit outside the explosive environment, and determining the likelihood of ignition of an explosive environment by the number of explosions, characterized in that test performance, monitor the completion of the transient process in the circuit by monitoring the absence of current frequency and voltage other than the frequency of the supply voltage, and the circuit is switched outside the hazardous environment at the end of the transition process, and the circuit is switched to the initial state outside the hazardous environment after a period of time longer than the gas mixture ignition time Figz