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Old 29th Apr 2019, 10:39 am   #56
broadgage
Nonode
 
Join Date: Jan 2010
Location: North Somerset, UK.
Posts: 2,129
Default Re: The lightbulb conspiracy

On strictly economic grounds, there would be a case for use of 120 volt lamps in series pairs on 240 volt supplies.
In practice the complication and risks of mistakes outweigh the advantages.

For lamps of very low power, series operation is still preferred. A 240 volt 3 watt lamp is relatively expensive, is of very low efficiency, and unreliable. Hence the popularity of series connected 20 volt 3 watt lamps for Christmas decorations.

For a supply voltage of much more than about 250 volts, series connection is preferred.
"traction lamps" used to be manufactured, primarily for use in trams. They came in 60 watt and a selection of voltages in the 100 volt to 125 volt range.
Intended use was five lamps in series from the overhead line voltage of about 500 to 560 volts. Traction lamps were either specially manufactured, or specially selected from standard production so as to have accurately matched current ratings.
Also once used on DC electric railways.
The red traction lamp illustrated in an earlier post was probably for the taillight of a tram, run in series with 4 other white lamps of the same rating.
AFAIK these lamps are no longer made. Heritage or vintage trams still in use tend to use standard 60 watt, 110/120 volt lamps, five in series.
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