JPS5826253B2 - safety retainer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention prevents excessive electrical energy from flowing into an intrinsically safe circuit installed in an explosion-proof area, and also prevents the inflow of energy that may cause sparks in an explosion-proof area. It relates to a so-called safety barrier.

The safety barrier is interposed between, for example, a general circuit provided in a non-hazardous area and an intrinsically safe circuit provided in an explosion-proof area, and is installed in a non-hazardous area.

Conventional safety barriers include resistance barriers in which a resistor is inserted in series, Zener barriers in which Zener diodes are connected in parallel to prevent voltages exceeding a predetermined voltage value from flowing into an intrinsically safe circuit, and Other relays,
Barriers using transformers and photocouplers are known.

All of these safety keepers require high frequency power, for example 1
It is impossible to propagate radio frequency signals above 0 KHz with low loss.

Furthermore, electrical equipment installed in dangerous locations requires appropriate safety measures in order to prevent explosions and fires caused by the generation of electrical sparks in the event of an abnormality, ie, a short circuit or an open circuit.

One of the safety measures is to limit the energy generated in hazardous areas in the event of an abnormality to a weak energy that does not cause an explosion or fire.

Stabilizers take the above-mentioned safety measures by limiting the electrical energy sent to electrical equipment installed in hazardous locations.

However, since the safety keeper only needs to pass high-frequency energy of radio frequencies, it is necessary to block low-frequency energy containing unnecessary direct current components from the viewpoint of reducing the degree of danger.

Here, the return path of low-frequency energy current including direct current during an abnormality may be the ground, electric conduit, cable shield, or the like.

Therefore, the main object of the present invention is to be able to propagate high-frequency power with low loss, and to eliminate excessive high-frequency energy that may cause a dangerous situation in explosion-proof areas and low-frequency energy including direct current in abnormal situations. It is an object of the present invention to provide a safety keeper that prevents the flow of water into a safety circuit.

FIG. 1 is a longitudinal cross-sectional view of a safety retainer according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view taken from the line T in FIG. 1.

The safety keeper 1 receives high frequency power, for example, 10
A radio frequency signal of KHz or higher is transmitted to an antenna circuit including a coaxial transmission line 3 button and a waveguide 4 in an explosion-proof area.

The transmission line 3 and the waveguide 4 are made of steel and are buried underground.

In order to prevent corrosion, a DC power supply 5 is connected to the waveguide 4 for applying a negative voltage of, for example, -2V with respect to the ground potential.

High frequency power from the transmitting circuit 2 is input to a connector 9 having a pair of primary terminals consisting of an outer conductor 7 held in a metal case 6 of the safety holder 1 and a center conductor 8.

The outer conductor 7 is electrically isolated from the case 6 by an insulator 10, and the center conductor 8 is electrically isolated from the outer conductor 7 by an insulator 11.

The safety retainer 1 has a structure that is almost symmetrical to the left and right in FIG.
The case 6 is divided into four chambers: a first chamber 12 and a second chamber 13 on the primary side A, and a third chamber 14 and a fourth chamber 15 on the secondary side B.

In the first chamber 12, the outer conductor 1 is integral with the outer conductor 7.
An annular electrode 17 is formed at the end of the electrode 6 .

This electrode 17 and a shielding plate 18 forming another electrode
A dielectric 19 is interposed between the capacitor 20 and the capacitor 20.
is formed.

One end of a fuse 21 provided coaxially with the outer conductor 16 is connected to the center conductor 8, and the other end is supported by an insulator 22.

A coil 23 is provided in the second chamber 13 , and one end of the first coil 23 is supported by the insulator 22 and electrically connected to the fuse 21 .

The other end of the coil 23 is connected to the center electrode 25 of the capacitor 24.

FIG. 3 is a front view of the capacitor 24.

The capacitor 24 includes a center electrode 25, another cylindrical electrode 26 integral with the shielding plate 18, and both electrodes 25 and 26.
and a derivative 27 interposed therebetween.

The shape and dimensions of the coil 23 and the second chamber 13 are determined so as to resonate with the frequency of the input high-frequency power, thereby forming a primary resonance circuit.

In order to finely adjust the resonance frequency, a trimmer capacitor 28 such as a screw that can be moved back and forth is provided in the second chamber 13.

Center electrode 25 of capacitor 24 and electrode IT of capacitor 20 are connected by lead wire 29 .

A coil 30 electromagnetically coupled to the coil 23 is provided in the second chamber 13 .

One terminal of the coil 30 is connected to the case 6.

The other terminal of the coil 30 is connected to the shielding plate 1 via an insulator 31.
8 and provided in the first chamber 12.
connected to the anode of the

A cathode of the diode 32 is connected to the case 6.

FIG. 4 is a sectional view taken along the line ■--■ in FIG. 1.

A shielding plate 33 that partitions the second chamber 13 on the primary side A and the third chamber 14 on the secondary side B is provided with an electromagnetic coupling window 34 that connects the two chambers 13 and 14.

The third chamber 14 is configured symmetrically with the second chamber 13 in FIG.

A coil 35 forming a secondary resonance circuit is provided in the third chamber 14, and a trimmer capacitor 36 and a coil 37 electromagnetically coupled to the coil 35 are also provided.

The secondary resonant circuit resonates at the same frequency as the primary resonant circuit.

The fourth chamber 15 has a structure similar to the first chamber 12 described above.

A shielding plate 38 provided between the third chamber 14 and the fourth chamber 15
A dielectric 40 is interposed between the electrode 39 and the electrode 39, forming a capacitor 41.

The electrode 39 is electrically connected to an outer conductor 42, which is connected to an outer conductor 43.

The outer conductor 42 and the outer conductor 43 include insulators 44 and 45.
A lead wire 46 is provided across the insulators 44 and 45.

One end of the nine-wire wire 46 is connected to one end of the coil 35, and the other end is connected to a center conductor 47 coaxial with the outer conductor 43.

The outer conductor 43 and the center conductor 47 constitute a pair of secondary terminals of the connector 48.

The outer conductor 43 is electrically isolated from the case 6 by the insulator 51.

The other end of the coil 35 is connected to one end of the center electrode 49 of the capacitor 58.

The other end of this center electrode 49 is connected to the electrode 3 via a lead wire 50.
Connected to 9.

The other end of the coil 37, one end of which is connected to the case 6, passes through the shielding plate 38 via the insulator 51 and connects to the diode 52.
connected to.

The center conductor 41 of the connector 48 and the inner conductor 5 of the transmission line 3
Connected to 3.

The end of this internal conductor 53 is connected to an excitation probe 54 provided protruding inside the waveguide 4 .

FIG. 5 shows the characteristics of the diode 32.

The relationship between the voltage V applied between the anode and the cathode as shown in FIG. 51 and the forward current i flowing from the anode to the cathode is shown in FIG. 52.

When the potential difference between the anode and the cathode reaches a forward voltage drop value Vl of, for example, about 0.6 V, the forward current i begins to flow rapidly.

FIG. 6 is an equivalent circuit diagram of the safety barrier 1 shown in FIGS. 1 to 4.

Here, the capacitor 55 is the sum of the capacitance created by the case 6, the shielding plate 18, and the coil 23, and the capacitance of the trimmer capacitor 28.

Further, the capacitor 56 is the sum of the capacitance created by the case 6, the shielding plate 38, and the coil 35, and the capacitance of the trimmer capacitor 36.

The coils 23 , 35 are therefore electromagnetically coupled with the degree of coupling determined by the electromagnetic coupling window 34 .

When the connector 9 consisting of the outer conductor I and the center conductor 8 is given high frequency energy that resonates in the primary and secondary resonant circuits, for example at 10 KHz or higher, the primary side A has a coil 23, a capacitor 20, 24 and capacitor 55
A resonance phenomenon occurs at a resonant frequency that is constant at .

The high frequency energy is thus propagated to the resonant circuit on the secondary side B defined by the coil 35 and the capacitor 41°58.56.

This resonant high frequency energy on the secondary side B is transmitted through the external conductor 43
and a center conductor 47, and normal communication is thus carried out.

Assume that energy dangerous to an explosion-proof area, such as direct current, low frequency power at about the commercial power frequency, and excessive high frequency energy are supplied to the primary side A.

1. When considering direct current, generally coaxial connectors 9
The external conductor 1/I'i is used by grounding.

The ground potential of this external conductor 1 is the capacitor 20°24.
41 and 58, and the internal conductor 53 and excitation probe 54 are at the same potential as the waveguide 4 via the lead wire 50, coil 53, and center conductor 41.

Therefore, even if the excitation probe 54 and the waveguide 4 come into contact, there is no risk of electrical sparks occurring, and therefore, there is no risk of explosion.

Further, the ground potential of the external conductor 7 is set to the capacitor 20°24.
41.58 and interrupted by coil 23.35,
Since the transmission line 3 and the waveguide 4 are prevented from reaching the ground potential via the external conductor 43, the corrosion prevention effect of the DC power supply 5 is achieved.

Furthermore, when using the external conductor 1 without grounding, even if a DC voltage is applied to both conductors of the connector 9 due to an abnormality in the transmitting circuit 2, this voltage will be applied to the transmission line 3 and waveguide 4 in an explosion-proof area. and is not transmitted to the internal conductor 53 and the exciter 54.

When a DC voltage is applied between the outer conductor 7 and the center conductor 8, the fuse 21, the coil 23 and the lead wire 2
For a short circuit consisting of 9, the outer conductor 7 and the center conductor 8
is 11 of zero voltage.

Next, when a comparatively low frequency ground potential such as commercial voltage is supplied to the primary side A, the power is blocked by the high impedance of the capacitors 20, 24, 55 and 41°56.58, and the The potential between coils 23 and 9-
The low impedance of the lead wire 29 causes a short circuit.

If excessive high frequency energy is then supplied to the connector 9, the primary resonant circuit including the coil 23 and the capacitor 24.55 will resonate.

Since the coil 23 and the coil 30 are electromagnetically coupled,
An induced voltage is generated across the coil 300.

When this voltage value is excessive, that is, when excessive high frequency energy is input exceeding the forward voltage drop value v1, the diode 32 becomes conductive as explained in FIG. 5.

Therefore, part of the resonant energy resonating between the coil 23 and the capacitor 20°24.55 is transferred to the coil 30.
Heat is dissipated in a closed loop with the diode 32 and the diode 32.

At the same time, if excessive high frequency energy is applied, the fuse 21 will melt.

The capacitors 41, 56, 58 are arranged so that even if a stray current flows into the transmission line 3 and the waveguide 4, or a potential difference occurs between the excitation probe 54 and the waveguide 4 due to the soil quality, their potentials will be maintained at the primary side A. Furthermore, it prevents an adverse effect on the transmitting circuit 2 as a general circuit.

Note that when excessive high-frequency energy is input to the outer conductor 7 and center conductor 8 of the connector 9, when the diode 32 becomes conductive, the coil 30 receives a harmonic frequency that is an integral multiple of the resonant frequency of the primary side A. may occur.

In this case, since the coil 23 and the coil 30 are electromagnetically coupled, the harmonic power is given to the primary side resonant circuit, but the primary side and secondary side resonant circuits are Therefore, almost no harmonic power is transmitted to the secondary side B.

The same thing can be said about the harmonic power generated in the coil 31.

Since the safety barrier 1 includes two capacitors 20, 24, and 41.58 in series across the primary side A and the secondary side B, the structural conditions of the safety barrier can be satisfied.

Since the external conductor 43 of the secondary side connector 48 has a corrosion protection potential with respect to the earth, the case 6 may be ungrounded to reliably prevent the external conductor 43 from reaching the ground potential.

When case 6 is grounded, another capacitor is connected in series with capacitor 41 and capacitor 58 is connected in series with capacitor 41.
A further capacitor may be connected in series to satisfy the construction requirements of the safety barrier.

The resonant frequency f on the primary side is expressed by the first equation.

The combined capacitance CMl is the capacitor 20.24. %-
and 55 are C20, C24, and C55, and the inductance of the coil 23 is L23, as shown by the second equation.

fl-...(1) With 2π〆, ngo M1 1 1 + C55C24+C20 C55(C24+C20,,,(2) C55+C24+C20 On the secondary side, the capacitance of capacitor 41.56.58 is set as C41, C56, C58. , if the inductance of the coil 35 is L35, then the resonance frequency f2 (=fl) is expressed by the third equation.

FIG. 7 is an electrical circuit diagram of another embodiment of the present invention.
Parts having the same functions as those shown in the figures are given the same reference numerals.

It should be noted that in this embodiment, the coil 30 shown in FIG.
;37 and diode 32;52 are removed.

A safety barrier is installed between the terminal 21a on the primary resonant circuit side of the fuse 21 connected to the center conductor 8 of the connector 9 on the primary side A and the external conductor 7 according to the Factory Electrical Equipment Explosion-proof Guidelines of the Ministry of Labor Safety Research Institute. Due to structural conditions, a plurality of diodes 59 are connected in parallel.

This diode 59 has the characteristics shown in FIG.

When an excessive high frequency voltage exceeding the above-mentioned forward voltage drop value (1) is applied to the outer conductor 1 and the center conductor 8, the diode 59 becomes conductive.

Therefore, the outer conductor 7 and the center conductor 8 are short-circuited, and excessive high frequency energy is not transmitted to the resonant circuit.

If the forward voltage drop value is 1, it is larger than the high frequency signal voltage to be propagated.

Since the fuse 21 is blown by excessive high frequency energy, the diode 59 is prevented from being melted and damaged.

It is pointed out that the present invention can be implemented not only by a high-frequency circuit having the three-dimensional structure described above, but also by a so-called lumped constant circuit element.

As described above, according to the present invention, the primary and secondary resonant circuits that resonate with the radio frequency electric signal to be transmitted are provided, and the two resonant circuits are electromagnetically coupled, so that the radio frequency signal can be transmitted with low loss. be able to.

Generally, in electrical equipment installed in a hazardous location, appropriate safety measures are required in order to prevent explosions and fires due to the generation of electrical sparks when an abnormality occurs, that is, when a circuit is short-circuited or opened.

As one of the safety measures, there is a safety barrier that limits the energy generated in a hazardous area in the event of an abnormality to a weak energy that does not lead to an explosion or fire.

Since the safety keeper only needs to pass high-frequency energy of radio frequencies, it is necessary to block low-frequency energy for the purpose of reducing the danger level of low-frequency energy containing unnecessary direct current components.

The return path for low-frequency energy current during an abnormality is the earth, radio tube, cable shield, etc.

Therefore, in the present invention, by electromagnetically coupling the primary and secondary side resonant circuits, (1) high frequency energy is transmitted from the primary side to the secondary side with low loss, and (2) high frequency energy is transmitted from the primary side to the secondary side. Together with the capacitor, it achieves the effect of blocking low frequency energy including direct current from being transmitted to the next side.

In addition, in the present invention, a coil is provided that is magnetically coupled to the coil constituting the resonant circuit, and the induced electromotive force generated in the magnetically coupled coil is consumed by the diode, so that excessive high-frequency energy is prevented from propagating to the secondary side. This will be prevented.

Furthermore, when a high frequency signal value larger than the forward voltage drop value v1 of multiple diodes provided on the primary side is input, the fuse blows, preventing excessive high temperature energy from propagating to the secondary side. I can escape.

Generally, in the radio frequency domain, when a coil is connected in the middle of transmitting high-frequency signal energy, the coil is placed in a metal case to prevent the radiation of high-frequency energy from the coil to the outside and the inflow of unnecessary high-frequency energy from the outside. You need to cover it with

However, since stray capacitance is created between the coil and the metal case, the transmission efficiency of high frequency energy from the primary side to the secondary side is reduced.

In order to solve this problem, the present invention actively uses stray capacitance for resonance, which provides the excellent advantage of eliminating the negative effects of stray capacitance.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a safety retainer 1 according to an embodiment of the present invention;
2 is a sectional view taken along the line G in FIG. 1, FIG. 3 is a front view of the capacitor 24, FIG. 4 is a sectional view taken along the line ■-■ in FIG.
6 is a diagram showing the characteristics of the diode 32, FIG. 6 is an equivalent circuit diagram of the safety barrier 10, and FIG. 7 is an electric circuit diagram of another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Safety holder, 2... Transmission circuit, 3... Transmission line, 4... Waveguide, 5... DC power supply, 6... Case, 1゜16.42,43 ...Outer conductor, 8,47.
...Center conductor, 9...Connector, 10. it, 22,
31゜44.45.51.57...Insulator, 12...
・1st room, 13...2nd room, 14...3rd room, 15
...4th chamber, 17.26,39...electrode, 18,3
3,38...shielding plate, 19.27.40...dielectric, 20,24°41.55.56.58...capacitor, 21...scold. Use, 23.30.35.37...Coil, 25°49...Center electrode, 28,36...Trimmer capacitor, 29. 46. 50...Lead wire, 32.
52. 59... Diode, 34... Electromagnetic coupling window, 48... Connector, 53... Internal conductor, 54...
...Exciter.

Claims (1)

[Claims] 1. A stray capacitance 55 formed by a metal case surrounding the first coil 23 is equivalent to a series circuit formed by connecting one end of the first coil 23 and one end of the first capacitor 24. are arranged in parallel, the other end of the first coil 23 is connected to one primary terminal 8, the connection point between the first coil 23 and the first capacitor 24 is connected to the other primary terminal 7, A second capacitor 20 is connected between the other primary terminal 7 and the other end of the first capacitor 24, and the first coil 23
The coil 3 is connected to a series circuit formed by connecting one end of the second coil 35 and one end of the third capacitor 58, which are electromagnetically coupled to the coil 3.
A stray capacitance 56 formed by a case surrounding the capacitor 5 is equivalently provided in parallel, the other end of the second coil 35 is connected to one secondary terminal 47, and each of the first and third capacitors 24, 58 and The ends of the second coil 35 and the third capacitor 58 are connected to each other, and the connection point between the second coil 35 and the third capacitor 58 is connected to the other secondary terminal 43. A fourth capacitor 41 is connected between the first coil 23 and
, the first capacitor 24, the first stray capacitance 55, and the second
The capacitor 20 constitutes a primary resonance circuit, the second coil 35, the third capacitor 58, the second stray capacitance 56, and the fourth capacitor 41 constitute a secondary resonance circuit, and the primary resonance circuit and , a secondary resonant circuit is a coil 30 or 37 that resonates at the same radio frequency to be propagated, is magnetically coupled to the first or second coil 23.35, and has a voltage across the coil 30 or 37 at a predetermined value. When the coil exceeds 30 or 37
A safety barrier characterized by being provided with a diode 32.52 that consumes induced electromotive force. 2. A stray capacitance 55 formed by a metal case surrounding the first coil 23 is equivalently provided in parallel to a series circuit formed by connecting one end of the first coil 23 and one end of the first capacitor 24, The other end of the first coil 23 is connected to one primary terminal 8, the connection point between the first coil 23 and the first capacitor 24 is connected to the other primary terminal 7, and the other primary terminal 7 is connected to the other end of the first coil 23. and the other end of the first capacitor 24, and the second capacitor 20 is connected between the first coil 23 and the other end of the first capacitor 24.
The coil 3 is connected to a series circuit formed by connecting one end of the second coil 35 and one end of the third capacitor 58, which are electromagnetically coupled to the coil 3.
A stray capacitance 56 formed by a case surrounding the capacitor 5 is equivalently provided in parallel, the other end of the second coil 35 is connected to one secondary terminal 47, and each of the first and third capacitors 24, 58 The ends are connected to each other, the connection point between the second coil 35 and the third capacitor 58 is connected to the other secondary terminal 43, and between the other primary terminal 43 and the other end of the third capacitor 58. A fourth capacitor 41 is connected to the first coil 23,
The first capacitor 24, the first stray capacitance 55, and the second capacitor 20 constitute a primary resonant circuit, and the second coil 35, the third capacitor 58, the second stray capacitance 56, and the fourth capacitor 41 constitute a primary resonant circuit. The primary resonant circuit and the secondary resonant circuit resonate at the same radio frequency and are connected in series between one of the primary terminals 8 and the primary resonant circuit. It is connected between the fuse 21, the connection point between the fuse 21 and the primary resonant circuit, and the other primary terminal 7, and is larger than the high frequency signal voltage to be propagated and smaller than the excessive high frequency voltage to be blocked. A safety barrier comprising a plurality of diodes 59 having a forward voltage drop value v1 and connected in parallel in opposite directions.