RU2348093C2 - Device for protecting pyrocartridge from false triggering during pulse surges - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: present invention can be used in electrical engineering for protection false triggering of fire extinguishing systems. The device has three protection stages. The first is in form of an aerial fuse with three electrodes, one of which is earthed. The second stage has induction coils and series-connected semiconductor voltage limiters, in form of TVS - bidirectional diodes or varistors or protective thyristors, the common point of which is connected to the earthed electrode of the aerial fuse. The other two electrodes are connected to the induction coils. The third protection stage has a series circuit of a diode and coils of an electromagnetic relay, and is connected to the triggering wires in parallel to the semiconductor voltage limiters. The relay contacts shunted with a resistor can be fitted in any of the triggering wires. When there is fire, trigger voltage and current are applied in opposite direction to the control voltage and current, closing the relay contacts, thus triggering the pyrocartridge.

EFFECT: equalisation of potential between triggering wires and any of the triggering wires and earth, and reduced number of elements of the circuit.

7 cl, 5 dwg

Description

The claimed invention relates to electrical engineering, and in particular to devices for protection against false start of fire extinguishing systems (PT) during atmospheric (natural) surge voltages that occur during lightning discharges and during switching (artificial) overvoltages (switching located near high voltage circuit systems, such as: a short circuit in power lines, turning on / off powerful loads, etc.). The device is intended for installation in low-voltage starting wires between the control-starting device and the squib.

The absence of false starts is the most important condition for the reliability of fire protection systems.

A device is known that can be used in fire extinguishing systems to protect the squib from false triggering during surge surges (see RF certificate No. 34814 for the utility model “Surge protection device”, IPC 7 Н02Н 1/00). The known device has three interconnected stages of protection, the first of which contains a two-electrode spark gap PT1, the electrodes of which are connected to the beginnings of the induction coils L1 and L2 installed in the starting wires, the ends of which are connected to the inputs of the Zener diodes VD1 and VD2 connected in series (coils L1 , L2 and Zener diodes VD1, VD2 are the second stage of protection), and the third stage of protection contains a transistor VT1, two diodes VD3, VD4 (VD2 is wrongly indicated in the drawing) and an electromagnetic relay with shunted resistor Rco nt. K1 contacts installed on the side of the igniter in the starting wire, to which the anodes of the VD3 and VD4 diodes are connected. The known device operates reliably in the event of an overvoltage between the starting wires, but it does not protect the fire extinguishing system igniter from a false start during pulsed overvoltages between at least one of the starting wires and the ground.

Thus, a disadvantage of the known device is reduced protective characteristics.

The known device according to certificate No. 34814 for a utility model is the closest to the claimed device in technical essence and the achieved effect, therefore, it is selected as a prototype.

The objective of the present invention is: to improve the protective characteristics of the device while simplifying the design of the device.

The technical result consists in equalizing voltage potentials between the starting wires and any of the starting wires and ground, as well as in reducing the circuit elements.

This task is achieved by the fact that in the known device for protecting the squib from false triggering during surge voltage connected between the control and starting device and the squib, there is a spark gap, the electrodes of which are connected to the induction coils installed in the starting wires, the ends of the latter are connected to the terminals connected in series with each other another semiconductor voltage limiter, while a diode connected to an electromagnetic relay coil is connected to one of the starting wires shunted by a resistor whose contacts are installed in one of the starting wires from the side of the squib, according to the invention, the arrester is equipped with a third grounded electrode connected to a common point of the semiconductor voltage limiters connected in series, which are bi-directional TVS diodes, or varistors, or lightning protection thyristors, moreover the diode and coil of the electromagnetic relay form a circuit whose ends are connected to the starting wires in parallel with the semiconductor limiters conjugation.

In the inventive device, the function of a three-electrode spark gap can be performed in series by two two-electrode spark gap with a grounded common connection point connected to a common point in series of semiconductor voltage limiters connected to each other.

In the claimed device, the cathode of the diode can be connected to the first end of the coil of the electromagnetic relay, the contacts of which are shunted by the resistor are installed in the starting wire to which the anode of the diode is connected.

In the claimed device, the anode of the diode can be connected to the first end of the coil of the electromagnetic relay, the contacts of which are shunted by the resistor are installed in the starting wire to which the cathode of the diode is connected.

In the claimed device, the cathode of the diode can be connected to the first end of the coil of the electromagnetic relay, the contacts of which are shunted by the resistor are installed in the starting wire to which the second end of the coil of the electromagnetic relay is connected.

In the claimed device, the anode of the diode can be connected to the first end of the coil of the electromagnetic relay, the contacts of which are shunted by the resistor are installed in the starting wire, to which the second end of the coil of the electromagnetic relay is connected.

In the inventive device, a bi-directional TVS-diode can be composed of two unidirectional TVS-diodes by their on-line serial connection to each other.

Studies on patent and scientific and technical sources indicate that the proposed device for protecting the igniter from false triggering during surge surges is unknown and does not follow explicitly from the studied prior art, and therefore meets the criteria of "novelty" and "inventive step".

The inventive device can be manufactured in an enterprise specializing in the industry engaged in the production of electronic equipment, using standard domestic or imported equipment, well-known technologies and mass-produced by the industry of electrical and semiconductor elements. It can be widely used in all industrial, office and residential premises.

Thus, the claimed device for protecting the squib from false triggering during surge voltage meets the criterion of "industrial applicability".

The proposed set of essential features informs the claimed device of new properties that allow to solve the problem.

The inventive device has three stages of protection: the first one contains a three-electrode spark gap with one grounded electrode (or two two-electrode spark gap with a grounded common point), the second stage contains induction coils and semiconductor voltage limiters connected in series with each other, a common point of which is connected to a grounded electrode arrester. The third stage of protection connected to the second contains a diode, an electromagnetic relay coil, its contacts and a resistor.

In the pyro cartridge integrity control mode, the current in the device flows in accordance with the polarity of the connection through the pyro cartridge (not shown in the diagram) and a resistor. When the control current flows, the first, second and third stages (except for the resistor) are switched off and do not affect the operation of devices (PT) in the control mode. In the normal mode of starting the squib, i.e. in the event of a fire, the starting control device (PT) supplies the starting voltage and current in the opposite direction, opposite to the control one. Then the diode opens and the coil of the electromagnetic relay is energized, as a result of which the relay contacts close and "short-circuit" the resistor. Since the resistor ceases to influence the passage of inrush current and voltage, the inrush voltage is applied to the igniter and it starts up.

In the prototype, if at the input of the protection device, the voltage potential at least on one of the wires turns out to be high relative to the ground (or the housing of the igniter) when pulsed overvoltages occur from atmospheric or switching interference, a spark breakdown between the igniter thread and its housing is possible. By virtue of which, ignition of the pyrotechnic substance occurs and a false start of the squib occurs.

In the claimed protection device, this moment is taken into account due to the presence of a third grounding electrode. In the event of an overvoltage at the input of the protection device, grounding of its input terminals is ensured when the arrester and (or) protective TVS diodes are triggered.

The prototype used zener diodes VD1 and VD2. Usually they are used if it is necessary to regulate the voltage in electronic circuits. However, the zener diodes do not protect the circuit from powerful pulses arising from atmospheric or switching interference, because not designed for operation with significant pulsed loads.

In the inventive device, it was decided to choose such semiconductor voltage limiters, such as bi-directional TVS diodes, or varistors, or lightning protection thyristors. The abbreviation TVS comes from the English term "transient voltage suppressor", which is translated into Russian as a semiconductor voltage limiter, otherwise - "suppressor". Varistors and lightning protection thyristors are bi-directional by industry. TVS diodes can be made both unidirectional and bidirectional. For the claimed circuit, bi-directional TVS diodes are selected. This allows the circuit to be symmetrical and, when pulsed overvoltages of different polarity occur, operate with the same limitation. A comparison of the operating characteristics of bi-directional TVS diodes, or varistors, or lightning protection thyristors with the characteristics of zener diodes, showed that the latter are less reliable if necessary, absorb powerful overvoltage pulses, limit their peaks and prevent them from growing. Zener diodes only stabilize or regulate the voltage in the circuit. In the control operating mode, the bi-directional TVS diodes, varistors or lightning protection thyristors (hereinafter TVS diodes) are “invisible”, i.e. do not affect the operation of the starting device they protect, up to the occurrence of an overvoltage pulse.

During the action of the overvoltage pulse, the TVS-diode limits the voltage surge to a safe value at which the igniter can not be started, while a dangerous current flows through the TVS-diode to the ground, bypassing the protected circuit. In this case, the residual voltage on the TVS diodes creates a very small current through the shunt resistor. Such a current cannot trigger a squib.

In the prototype, the third stage of protection contains diodes VD3, VD4, transistor VT1 and an electromagnetic relay with a coil and contacts. The diode VD3 is designed to open the transistor VT1 at start-up, and the diode VD4 - to protect the transistor when switching the relay coil.

In the claimed protection device, only one diode is used, which is designed to disconnect the relay coil when the control current flows through the device, and when starting current to power the relay coil. This simplifies the design of the device due to the exclusion from the circuit of the transistor VT1 and the diode VD4. In addition, the diode in the inventive device determines the direction of the control current, i.e. connection polarity: when the control current flows, the diode must be “closed”.

The proposed device for protecting the squib from false triggering during surge surges is illustrated by the drawings, which show:

figure 1, 2, 3, 4 - General diagrams with different polarity of the connection to the voltage source and the connection options of the diode, coil and contacts of the electromagnetic relay;

5 is a fragment of a General circuit with two arresters.

To the terminals “+”, “-” of the inventive device for protecting the squib from false start during pulsed overvoltage, a control-starting device (not shown in the drawing) is connected, which supplies either the starting or control voltage and current to the squib in fire and in control squib. The device itself protects the squib from false triggering during overvoltage surges contains a spark gap 1 with three electrodes, one of which is grounded, and the other two are connected to the corresponding starting wires (not shown in the diagram) and inductive coils 2 and 3. Instead of inductive coils in the protection circuit installation of resistors - active resistances is possible. In general, this does not affect the solution of the task. Since in the prototype inductive coils are installed, in the claims they are reflected. The ends of the inductive coils 2, 3 are connected to the terminals of the corresponding semiconductor voltage limiters 4 and 5, which are bi-directional TVS diodes, or varistors, or lightning protection thyristors, connected in series with each other. Their common point is connected to the grounded electrode of the arrester 1. The bi-directional TVS diode can be composed of two unidirectional TVS diodes by their counter-series connection to each other. In parallel to 4 and 5, a circuit containing a diode 6 connected in series with the anode or cathode to the coil of the electromagnetic relay is connected between the starting wires (not indicated in the drawing). In one of the starting wires between the igniter and the semiconductor voltage limiters 4 and 5 connected in series, relay contacts 7 are installed, shunted by a resistor 8 connected to terminals 9, 9 '. Relay contacts 7 can be connected both to the anode and the cathode of diode 6, or to the second end, not connected to diode 6, of relay coil 10.

When overvoltage pulses occur, the current in the circuit of the pyro cartridge protector against false triggering lasts a very short time, during which the electromagnetic relay does not have time to close contacts 7 and thereby short-circuit resistor 8. In this case, after the first and (or) second stage residual energy of the overvoltage pulse is dissipated on the resistor 8.

The choice of one or another “suppressor” depends on the requirements for protective characteristics in terms of power, absorption energy of a voltage pulse, etc.

At the output of the inventive device to the terminals 11, 11 'is connected a squib (not shown in the diagram), which starts up in the normal mode and acts on the cylinder with the extinguishing agent.

The proposed device operates as follows.

1. The operation of the protection device in the control mode of the squib and start in normal mode.

In this mode, the control current flows through the circuit in accordance with the polarity of the connection through the igniter and resistor 8 connected to terminals 9, 9 '. The electromagnetic relay is disconnected. no current flows through diode 6 and coil 10.

The resistance of the spark gap 1 and TVS diodes 4 and 5 is very large, so they do not affect the value of the control current.

In the case of supplying the starting voltage by the control-starting device, the diode 6 opens, because the starting voltage and current are applied in the direction opposite to the polarity of the device connection. The coil 10 of the electromagnetic relay is energized and closes the contacts 7. In this case, the resistor 8 is shorted and does not affect the passage of the starting current and voltage in the circuit of the device. A current begins to flow along the pyrocartridge filament, causing it to heat up, as a result of which the extinguishing agent balloon starts.

2. The operation of the claimed device in protection mode.

In the event of voltage overloads in the circuit, an overvoltage pulse appears at the “+” and (or) “-” terminals. In the first stage of protection, arrester 1 is activated, equalizing the electric potentials both between the starting wires and between the starting wires and the ground. Inductive coils 2 and 3 act as temporary dampers between the arrester and the second stage of protection to hold the voltage for about 1 μs necessary for the arrester to operate. The second stage of protection, consisting of TVS-diodes 4 and 5, limits the residual voltage in the circuit after triggering of the spark gap 1 within 12-30 V.

So, a standard lightning pulse with a duration of 8/20 μs is extended on TVS diodes by approximately 100 times to a value of 2000 μs, which is equal to 2 ms. This time is not enough for the pulsed current flowing through the third stage of protection, containing diode 6 and an electromagnetic relay with coil 10 and contacts 7, to be able to close the contacts 7 of the electromagnetic relay and short-circuit resistor 8. The residual pulse current after the first and second stages of protection is tripped is dissipated by resistor 8, as well as on diode 6 and coil 10 of the electromagnetic relay, which does not cause a false start of the squib.

The inventive device protects the squib from false triggering during overvoltage surges has a number of advantages compared to the prototype:

- high reliability due to the elimination of false positives;

- simplification of the design by reducing the number of circuit elements.

Claims (7)

1. A device for protecting the igniter from false triggering during surge voltage, connected between the control and starting device and the igniter, containing a spark gap, the electrodes of which are connected to the induction coils installed in the starting wires, the ends of the latter are connected to the terminals of the semiconductor voltage limiters connected in series with each other, this is connected to one of the starting wires a diode connected to the coil of an electromagnetic relay, the contacts of which are shunted by a resistor updated in one of the starting wires on the pyro cartridge side, characterized in that the arrester is equipped with a third grounded electrode connected to a common point of the semiconductor voltage limiters connected in series, which are bi-directional TVS diodes, or varistors, or lightning protection thyristors, the diode and the coil of the electromagnetic relay form a series circuit, the ends of which are connected to the starting wires parallel to the semiconductor voltage limiters. 2. The device according to claim 1, characterized in that the function of the three-electrode spark gap is performed by two two-electrode spark gap connected in series with each other with a grounded connection point connected to a common point of semiconductor voltage limiters connected in series with each other. 3. The device according to claim 1, characterized in that the cathode of the diode is connected to the first end of the coil of the electromagnetic relay, the contacts of which are shunted by the resistor are installed in the starting wire to which the anode of the diode is connected. 4. The device according to claim 1, characterized in that the anode of the diode is connected to the first end of the coil of the electromagnetic relay, the contacts of which are shunted by the resistor are installed in the starting wire to which the cathode of the diode is connected. 5. The device according to claim 1, characterized in that the cathode of the diode is connected to the first end of the coil of the electromagnetic relay, the contacts of which are shunted by the resistor are installed in the starting wire to which the second end of the coil of the electromagnetic relay is connected. 6. The device according to claim 1, characterized in that the anode of the diode is connected to the first end of the coil of the electromagnetic relay, the contacts of which are shunted by the resistor are installed in the starting wire to which the second end of the coil of the electromagnetic relay is connected. 7. The device according to claim 1, characterized in that the bi-directional TVS-diode is composed of two unidirectional TVS-diodes by their opposite serial connection to each other.

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