SU1425353A1 - Arrangement for ensuring spark safety of a.c. electric circuits - Google Patents

Abstract

The invention relates to electrical engineering and m. used to create lighting installations used in explosive atmospheres of enterprises in the mining, petrochemical and gas industries. The goal is to increase the intrinsically safe power and increase reliability. The device contains a source of direct current 1, to which the generator, 2, and the inverter 3, connected by a bridge circuit, are connected. The diagonal of the bridge is on load 4. The triangular voltage of increased frequency from generator 2 is fed to the primary winding 5 of the transformer 6 of the block 7 for providing intrinsically safe power. The latter contains a comparison node on two transistors (T) 8 and 9, transformer b and measuring resistor (P) 10 - current sensor. Sections 11 and 12 of the secondary winding of transformer 6 are connected to bases T 8 and 9 through P 13 and 14. In the comparison node, the triangular voltage unchanged in amplitude and frequency is compared to the bases of T 8 and 9 and the drop from variable load 4 voltage on P 10. The greater the load current of the inverter 3, the greater the voltage drop on P 10 and the shorter the duration of the rectangular voltage pulses on the load 4. 2 Il. 1C (L

Description

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The invention relates to electrical engineering, in particular, to methods and devices for ensuring the intrinsic safety of electrically operated AC circuits, and can be used to create lighting installations operating at increased frequency and having intrinsically safe parameters, 1 | 1 used in explosive atmospheres of mining, petrochemical and industrial enterprises. gas || industry.

I The aim of the invention is to increase the safe power and increase the reliability of operation.

FIG. 1 shows a functional diagram of the device; in fig. 2 - jMbi diagrams for the operation of the device.

The device contains a source of direct current 1, to which the master oscillator 2 is connected and the inverter-shaper 1 of the output signal, which is made according to the bridge circuit E., the diagonal of which includes the load 4. The generator 2 forms a triple voltage of increased frequency arriving at the primary winding 5 of the transformer 6 of the block 7 for providing spark-free power. Block 7 for providing spark-safe power is made of two transistors 8 and 9, a transformer 6, and a measuring resistor-current sensor 10. Two sections 11 and 12 of the secondary winding of the transformer 6 are connected via resistors Il3 and 14 to the bases of transistors 8 and 9. To the collectors of transistors 8 and 9 are connected the primary windings of transformers 15 and 16 of the inverter, the secondary windings of fluorine are connected through resistors to the bain-emitter transitions of the upper transis TJopOB 17 and 18, inverter 3, and the secondary transducers to control the lower transistors Orah 19 and 20 of the inverter 3 are connected by one pin to the common drive 21 of the source 1 constant current, and the second leads are connected through resistors to Lower basics of transistors 19 and 20 of the inverter 3, wherein between the bases and emitters of the transistors of each inverter includes protective diodes.

The device works as follows.

When the supply voltage is supplied from the direct current source 1, the master oscillator 2 begins to form a triangular voltage Ui (Fig. 2) supplied to the primary winding 5 of the transformer 6 of the intrinsically safe power supply unit 7. At the same time, antiphase triangular voltages U2 are generated in sections 11 and 12 of the secondary windings of the transformer 6 and from (Fig. 2), supplied to the bases of transistors 8 and 9. The secondary voltages of the control transformers 15 and 16 form rectangular voltages U4 and Us (Fig. 2), arriving in antiphase at the transistors 17, 19 and 18, 20, respectively, and the voltage Ue is formed at the load (Fig. 2).

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On transistors 8 and 9, a node is made comparing an unchanged amplitude and frequency of a triangular voltage (Ug and Oz, Fig. 2) supplied to the bases of the transistors and the voltage drop Uy (Fig. 2) varying from the load on the measuring resistor-sensor 10 current. The greater the load current of the inverter, the greater the voltage drop across the resistor-sensor 10 current and the smaller the duration of the pulses 0 rectangular voltage U4 and Us, and hence the rectangular voltage pulses Uf, (Fig. 2) on the load 4. The choice of the resistor 10 sets the required pause size t (Fig. 2), sufficient to deionize the plasma so that the pulse energy t (Fig. 2) is insufficient to ignite the explosive mixture at switching discharges.

When the inverter is overloaded, the current in the load is stabilized, since, the higher the load current of the inverter is, the shorter the pulse duration becomes 1 "and the pause length t (Fig. 2) is large, up to the short circuit mode. With an increase in the inverter supply voltage, the energy of the square voltage pulse is stabilized (Fig. 2), since the increase in the amplitude of the pulse is compensated by a decrease in its duration. This provides enhanced intrinsically safe power.

The increased reliability of the device is ensured by the fact that intrinsically safe parameters are preserved in any circuit in the circuit in the load circuit.

The inclusion of the secondary windings of transformers 15 and 16 to control the lower transistors 19 and 20 of the inverter 3 by the conclusions on the ground wire 21 of the direct current source 1, and the second terminals on the bases of the specified transistors ensures reliable closure of the inverters of the inverter during a short circuit 0 in the load.

Claims (1)

Invention Formula An apparatus for ensuring the intrinsic safety of electrical AC circuits, comprising a measuring resistor, a DC source to which the raised frequency master oscillator is connected, and an inverter made according to a bridge circuit, to which a load is connected to the diagonal, with the aim of increasing intrinsically safe power and reliability improvement, it is equipped with an intrinsically safe power supply unit containing a comparison node, made on two transistors, the base of which is through 5 tori are connected to terminals of the transformer secondary winding having a center tapped, connected to a common source wire constant H0 five five 0 The main current of the transformer is connected between the output of the high-frequency master oscillator and the common wire of the DC source, and the collectors of the transistors and the combined outputs of their emitters are connected to the inputs of the inverter . FIG. g