Inductor devices – Coil forms protective casing
Patent
1989-09-13
1992-06-16
Kozma, Thomas J.
Inductor devices
Coil forms protective casing
324127, 336174, 336176, 336223, H01F 1706, H01F 2730
Patent
active
051227738
DESCRIPTION:
BRIEF SUMMARY
BACKGOUND OF THE INVENTION
The invention concerns a device for injecting an electromagnetic signal into a conductive wire, especially to test its insulation and protection characteristics with regard to electromagnetic disturbances.
The method is already known for injecting into an electroconductive linkage cable between electric or electronic installations or equipment signals simulating lightning or electromagnetic disturbances resulting from a nuclear explosion. For injecting these signals, an openable annular two-piece clamp is used which includes a conductive wire wound onto a ferrite core an connected to a suitable signal generator and which is placed around the cable to be tested.
The results are scarcely satisfactory, as this known device exhibits too high a load impendance, poor efficiency of about 10% (the signal induced in the cable to be tested is weak with respect to the signal supplied by the generator), and the range of useable frequencies is limited.
SUMMARY OF THE INVENTION
The object of the invention is to provided a device for injecting a signal on a conducting wire making it possible to overcome these drawbacks.
The device according to the invention, said device including a two-piece annular clamp intended to be placed around the conductive cable and means for linkage to a signal generator, is characterized in that the clamp includes a thin internal tubular cylindrical conductor encompassed by an intermediate cylinder made of a material with ferromagnetic properties, and a thick external tubular cylindrical conductor, said external and internal conductors being at one extremity connected to the signal generator linkage means and being interconnected at their second extremity.
The device according to the invention exhibits low load impedance and high efficiency, namely of more than 50% and able to reach 80 to 85%. Furthermore, the choice of the section and length of the intermediate cylinder made of, for example, ferrite with ferromagnetic properties makes it possible to determine the low cut-off frequency of the device according to the application in question.
In practice, the pass-band of a device according to the invention is between several kilohertz and about one hundred megahertz.
According to a further characteristic of the invention, the clamp also includes cylinders made of a dielectric material placed between the aforesaid three cylinders, as well as inside the internal cylindrical conductor and outside the external cylindrical conductor.
Advantageously, the cylindrical conductors of the clamp include at their first extremity thick annular edges, said conductors being connected via said edges to the signal generator linkage means.
Thus, the impedance of this linkage means is reduced so that the voltage of the signal supplied by the generator is mainly applied at the extremities of the internal tubular cylindrical conductor of the clamp and not at the extremities of the internal cylindrical conductor/external cylindrical conductor assembly.
According to a further characteristic of the invention, the means linking the signal generator include at least one and preferably two cables with two coaxial conductors, the internal and external conductors of said cables being respectively connected to the internal and external cylindrical conductors of the clamp.
Thus, by feeding the clamp by the coaxial cables in parallel, the impedance of the source feeding the injection clamp is reduced.
According to a futher characteristic of the invention, the device comprses thin detachable conducting cylinders making it possible to adapt the clamp to the diameter of the cable to be tested.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention shall be more readily understood from a reading of the following description given by way of example accompanied by the annexed figures in which:
FIG. 1 is a diagrammatic axial cutaway half-view of the device according to the invention;
FIG. 2 FIG. 2 is a perspective diagrammatic view representing this device partly open.
DESCRIPTION OF THE PREFERRED EMBODIM
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Navy Technical Disclosure Bulletin, vol. 11, No. 3, Mar. 1986, Farber et al "Clamp-on Signal Injector for Underwater Cable".
Patent Abstracts of Japan, vol. 6, No. 211, Oct. 1982 57-117217 Jul. 21, 1982.
Kozma Thomas J.
Prana Recherche et Developpement
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