Electric lamp and discharge devices: systems – Three or more wire distribution systems
Patent
1982-02-04
1984-04-03
Dixon, Harold
Electric lamp and discharge devices: systems
Three or more wire distribution systems
315 96, 315256, 315257, 315189, H05B 3700
Patent
active
044410557
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to lighting systems and more particularly to lighting systems employing gaseous discharge lamps.
The present invention may be used for lighting industrial buildings, streets, motor roads, stadiums, mines, etc.
BACKGROUND OF THE INVENTION
The gaseous discharge lamp is a light source in which light is produced by gas ionization brought about by an electric discharge. To initiate the discharge, the electrodes of a gaseous discharge lamp must be supplied with a rather high voltage (from hundreds to thousands of volts) capable of breaking through the gap between the electrodes to initiate ionization and gaseous discharge. Until the discharge occurs, a gaseous discharge lamp has a very high impedance, the current in the lamp being practically absent. After initiation of the discharge, current flows through the lamp and its impedance decreases. To prevent damage to the lamp, the current in the ignited lamp must be limited. It is common practice to use for this purpose a reactor connected in series with the lamp. If the lighting system comprises a plurality of gaseous discharge lamps, then each of them is usually connected to the supply source through a separate reactor. A parallel connection of gaseous discharge lamps through a common reactor cannot be tolerated because the initiation of ionization in one lamp leads to reduction in the lamp voltage and thus prevents the firing of the other lamps.
Known in the art is a lighting system comprising an alternating-current voltage source and gaseous discharge lamps each connected to the voltage source through a reactor (cf. a book by O. G. Bulatov, V. S. Ivanov and D. I. Panfilov "Tiristornye Skhemy Vkljucheniya Vysokointensivnykh Istochnikov Sveta", published by "Energiya", Moscow, 1975, page 39, FIG. 2-20).
The voltage which initiates ionization in a gaseous discharge lamp is several times greater than the voltage to be supplied to the lamp after ignition. Therefore the voltage at the reactor is usually 2 to 2.5 times greater than the voltage drop across the ignited lamp so that the reactor should be designed for a relatively great electric power, with the result that it is relatively great in weight and size. This, in turn, leads to significant power losses in the winding and core of the reactor. Besides, the presence of the reactor brings about deterioration in the power factor and thus necessitates the use of power factor compensating capacitors. As a result, the lighting fixtures have great weight and size.
To prevent the reactor from saturation during operation, its core must be provided with an air gap the presence of which, in case the core is improperly assembled, may cause "humming" of the reactor during operation. Therefore, the necessity to assemble a core with an air gap complicates the making of the reactor and thus increases the cost of the lighting system.
The voltage provided by the supply source may prove to be insufficient to fire a gaseous discharge lamp, especially when high-pressure gaseous discharge lamps are used, e.g. when a high-pressure sodium vapour lamp having an ignition voltage of 1 kilovolt is connected to an alternating-current network of 220 or 380 volts. In such cases it is necessary to have additional starting devices, such as thermal relays having their contacts connected across the lamps to provide upon their opening a sharp increase in the lamp voltage due to the e.m.f. of self-induction induced in the reactor (for low-pressure lamps), or special circuits generating pulses of high voltage sufficient to break through the gap between the electrodes (for high-pressure lamps). The need to employ additional starting devices complicates the lighting system. A similar problem arises when several gaseous discharge lamps are connected in series because the breakdown voltage increases approximately in proportion to the number of series-connected lamps.
The voltage applied to gaseous discharge lamps after ignition must not deviate significantly from the nominal value because even a re
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Balchjunas Povilas I.
Martinaitis Ionas J.
Pilkauskas Alfredas B.
Tulaba Sauljus A.
Dixon Harold
Greenspan Myron
Kaunassky Politekhnichesky Institut
Lilling Bruce E.
Lilling Burton L.
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