RU2570933C2 - Alternating-current spark protection unit - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: alternating-current spark protection unit comprises transformer with magnetic shunt, two bilateral triode switches, two voltage-limiting circuits consisting of in-series suppressor and resistor, which common point is coupled to control electrode of the respective bilateral triode switch; each circuit is connected by its one end to the ground while the other ends and power leads of the triode switches are coupled to the respective outputs of the transformer secondary windings. The common point of suppressor and resistor may be connected to control electrode of the triode switch thorough an element with non-linear volt-ampere characteristic. Primary winding of the transformer may be coupled to source of spark voltage through a fuse. Primary and secondary windings of the transformer may be placed at lateral rods of E-core, which medium rod has a non-magnet gap. Two voltage-limiting circuits with triode switches may be doubled or tripled depending on the required level of intrinsic safety.

EFFECT: increasing spark-proof power.

5 cl, 3 dwg

Description

The invention is intended to power devices located in explosive atmospheres, for example, in mines and mines, including coal, gas and dust hazardous.

It can find application in other industries, such as petrochemistry, explosive industries, underground utilities, tunnels, subways, etc.

The closest analogue (prototype) of the invention is a spark-safe power supply (copyright certificate for invention SU No. 319923 with priority from 1969.07.25), containing a transformer with a magnetic shunt, a rectifier, a stabilizer on a thyristor and a zener diode, a lead-out thyristor and a smoothing filter on the inductor and a capacitor, characterized in that, in order to simplify the circuit and reduce heating losses, the anode of the thyristor of the advanced shutdown, the power circuit of which is shunted by a zener diode, is connected to the throttle inductor ivayuschego filter, and the cathode - to the control electrode of the thyristor regulator.

Mentioned ISKROPESENNY POWER SUPPLY is intended for power supply of direct current devices, which limits the scope of its application, in addition, it is not sufficiently protected from significant input overvoltages.

The technical problem to which this invention is directed is to increase the intrinsically safe power of AC circuits, reduce heat losses on elements in emergency conditions, introduce protection against input overvoltages, and increase noise immunity.

The problem is solved as follows.

The AC spark protection unit contains a transformer with a magnetic shunt, two triacs, two voltage limiting circuits consisting of a suppressor and a resistor connected in series, a common point of which is connected to the control electrode of the corresponding triac, each circuit is connected at one end to ground, the second ends and power leads of the triacs , - with the corresponding terminals of the secondary winding of the transformer.

The common point of the suppressor and resistor can be connected to the control electrode of the triac through an element with a non-linear current-voltage characteristic.

The primary winding of the transformer can be connected to a source of spark hazard voltage through a fuse.

The primary and secondary windings of the transformer can be located on the side rods of the U-shaped core, the middle core of which has a non-magnetic gap.

Two voltage limiting circuits with triacs can be duplicated or tripled depending on the required level of intrinsic safety.

The proposed AC spark protection unit, as well as its variants, provide an optimal choice for specific applications and can work, for example, when transmitting audio signals through wired communication lines.

Figure 1 shows a functional diagram of the proposed block spark protection AC.

The AC spark protection unit contains a transformer T1 with a magnetic shunt, two triacs, 1VS1 (2VS1), two voltage limiting circuits consisting of a suppressor 1VD1 (2VD1) and a resistor 1R1 (2R1) connected in series, the common point of which is connected to the control electrode of the corresponding triac 1VS1 (2VS1), each circuit is connected at one end to the ground, the second ends and power terminals of the triacs 1VS1 (2VS1), - with the corresponding terminals of the secondary winding of the transformer T1.

Two voltage limiting circuits 1VD1, 1R1 (2VD1, 2R1) with triacs 1VS1 (2VS1) can be duplicated or tripled depending on the required level of intrinsic safety.

The primary and secondary windings of the transformer can be located on the side rods of the U-shaped core, the middle core of which has a non-magnetic gap.

The AC spark protection unit may have the options shown in FIG. 2:

The common point of the suppressor 1VD1 (2VD1) and the resistor 1R1 (2R1) can be connected to the control electrode of the triac 1VS1 (2VS1) through an element with a non-linear current-voltage characteristic, for example, a circuit from counter-parallel connected diodes 1VD2, 1VD3 (2VD2, 2VD3).

The primary winding of transformer T1 can be connected to a source of spark hazard voltage through fuse F1.

The transformer T1 with a magnetic shunt has a closed magnetic circuit, which consists of two W-shaped cores. The transformer windings are located on different lateral rods of the core, which facilitates its immunity to short circuit between the windings. The shunting middle rod has a gap formed by reducing the height of the middle rod of one or two U-shaped cores.

This design allows the use of standard W-shaped cores made of soft magnetic ferrites, widely used in radio equipment.

Due to the presence of a gap in the shunting middle core core, the current-voltage characteristic of the transformer (Figure 3) has a steeply falling character. By changing the value of this gap, they achieve that the value of the short-circuit current I2 kz does not exceed the intrinsically safe level acceptable under the conditions.

Suppressors and controlled semiconductor elements - triacs are used as shunt voltage limiters to an intrinsically safe level.

The proposed unit spark protection AC works as follows.

During normal operation of the source, the output voltage is below the suppressor threshold, and the spark protection unit does not affect the operation of the source. At the time of breaking the output circuit, when the load current changes sharply, a voltage jump occurs at the output, which limits the voltage limiting circuit from the zener diode 1VD1, (2VD1) and the resistor 1R1, (2R1), so the voltage at each terminal of the secondary winding of the transformer relative to the ground cannot exceed suppressor threshold. When a more significant current appears through the voltage limiting circuit, a voltage drop across the resistor 1R1, (2R1) leads to the tripping of the triac 1VS1, (2VS1) with the closure of the secondary winding of the transformer with simultaneous complete shunting of the suppressors to avoid excessive heating. The power dissipated on the switched-on triac is negligible, which allows the circuit elements to reliably withstand emergency operation for a long time.

The circuit is restored in each half-cycle when the current through the triac is lower than the holding current. The inclusion in the circuit of the control electrode of the triac element with a non-linear current-voltage characteristic allows you to effectively deal with random trips of the triac from interference and reduce the spread of the triac threshold.

Since an intact transformer with a magnetic shunt (increased magnetic scattering) is used to power the secondary circuit, the short circuit current is limited to an intrinsically safe level.

In case of increasing the supply voltage of the transformer, the current value increases, but in this case, the fuse in the primary circuit is activated.

The use of two voltage limiting circuits symmetrically connected relative to the ground allows in some cases to double the voltage supplied to the load with respect to the permissible voltage for reasons of intrinsic safety. For example, it is required to power the transmitting antenna of the mine warning system, made in accordance with the patent for utility model No. 61949 with a priority of 10.27.2006, operating in the ultra-long wavelength range and representing an electric dipole; one end of each beam is connected to the corresponding terminal of the secondary winding of the transformer, and the second is grounded. Spatially, both beams are spaced and an electrical circuit between them is impossible. It is not excluded, however, damage to the beam of the antenna with a ground fault. In this case, one of the shunt circuits is shorted, and the second will limit the voltage of the secondary winding of the transformer (on the second shorted antenna beam relative to the ground) at an intrinsically safe level.

Claims (5)

1. An AC spark protection unit comprising a transformer with a magnetic shunt, two triacs, two voltage limiting circuits, consisting of a suppressor and a resistor connected in series, a common point of which is connected to the control electrode of the corresponding triac, each circuit is connected at one end to ground, the second ends and power terminals of the triacs - with the corresponding terminals of the secondary winding of the transformer. 2. The AC spark protection unit according to claim 1, the common point of the suppressor and resistor of which is connected to the control electrode of the triac through an element with a non-linear current-voltage characteristic. 3. The AC spark protection unit according to claim 1, the primary winding of the transformer of which is connected to a source of spark hazard voltage through a fuse. 4. The AC spark protection unit according to claim 1, the primary and secondary windings of the transformer of which are located on the side rods of the U-shaped core, the middle core of which has a non-magnetic gap. 5. The AC spark protection unit according to claim 1, two voltage limiting circuits with triacs which are duplicated or tripled depending on the required level of intrinsic safety.

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