Electricity: electrical systems and devices – Safety and protection of systems and devices – Transient responsive
Patent
1985-10-03
1987-10-06
Pellinen, A. D.
Electricity: electrical systems and devices
Safety and protection of systems and devices
Transient responsive
361119, 361399, 455301, H02H 322
Patent
active
046987223
DESCRIPTION:
BRIEF SUMMARY
FIELD OF INVENTION
The present invention relates to a transient protection unit of the type intended for connection to signal conductors for protecting equipment connected to the conductors, and more particularly to a unit of the type including primary protection components in the form of gas discharge tubes connected between the conductors and ground, and secondary protection components in the form of filter components and the like connected to the conductors. By "signal conductors" is generally meant telephone and signal lines for different types of information transfer, as well as conductors for operation, alarm and indication functions involving small operational currents and voltages.
BACKGROUND
Transient protection units of the above-indicated kind are intended to suppress dynamic variations in conductors generated by NEMP and LEMP (i.e., electromagnetic pulses arising from nuclear missile explosions or lightening and) also electromagnetic interference (EMI). In the case of pulses arising from nuclear missile explosions, there may be maximum values in the order of magnitude of 50 kilovolts with rise times in the order of magnitude of 5 ns. For effectively leading away as large a part as possible of such a pulse, associated gas discharge tubes should have a very low inductance to ground.
The secondary protection part is intended and dimensioned for catering to the remainder of the original pulse, which does not manage to be led to ground, and which may have an amplitude in the maximum order of magnitude of 1200 volts. It is important for the secondary protection part that there is as good screening outwardly as possible. In some cases, this requirement has been found inconsistent with the requirement for low inductance to ground of the gas discharge tubes.
SUMMARY OF INVENTION
An object of the present invention is to provide a transient protection unit which ensures a very low inductance to ground of gas discharge tubes and a very effective screening of the secondary protection part.
To achieve the above and other objects of the invention there is provided a transient protection apparatus adapted for connection to signal conductors for protecting equipment connected thereto. The apparatus provided in accordance with the invention comprises primary protection components in the form of gas discharge tubes which extend between the conductors and ground. The apparatus furthermore comprises secondary protection components connected to the primary protection components and being in the form of filter components including notably capacitors and inductors. The protection components are mounted on a circuit board which extends through the wall of a cabinet included in the apparatus. The circuit board has a contact surface. The apparatus furthermore includes a conducting bar connected with the aforesaid wall.
According to a further aspect of the invention the circuit board extends through the wall of the cabinet in such a manner that the primary protection components are located outside of the cabinet with the secondary protection components being located inside of the cabinet. The gas discharge tubes which constitute the primary protection components are clamped with the electrodes thereof in such a manner as to be located between the contact surface of the board and the aforementioned conducting bar. The conducting bar is connected with the above-mentioned wall. Also included in the apparatus of the invention are further conductors arranged between the primary and secondary protection components. These further conductors extend in screened relationship inside of the circuit board and through the wall thereby to connect the primary and secondary protection components.
According to yet another aspect of the invention, the secondary components are encapsulated by a middle case. It will be noted in the description which follows hereinbelow that the conducting bars form a portion of the metal case.
The invention and its advantages will next be described in detail with reference to an embodiment illustrated
REFERENCES:
patent: 3917981 (1975-11-01), Kern
patent: 3992652 (1976-11-01), Blaisdell et al.
patent: 4138711 (1979-02-01), Bremenour et al.
patent: 4481559 (1984-11-01), Buck et al.
patent: 4525770 (1985-06-01), Peretta
patent: 4567543 (1986-01-01), Miniet
Gaffin Jeffrey A.
Pellinen A. D.
Telefonaktiebolaget L M Ericsson
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