Further Progress• with Fluorescent Lighting
Page 40
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1 IN our issue dated December 14, 1945. we dealt with the new C.A.V. fluorescent lighting system for passenger vehicles, and since then C.A.V.. Ltd., Acton, London, has made much interesting progress.
The major problem which had to be tackled was that associated with the power supply. In the first,place, it is necessary to convert the 24-volt d.c. supply to, preferably, a.c. at 110 volts, and the essential factors which have to be taken into account are:—(a) the weight of the conversion equipment: (b) dimensions of the vehicle: (c) general simplicity.
Investigations by C.A.V., Ltd_ led to the design and introduction of a high-speed motor inverter, operating on a d.c. input of 24 volts, and giving an Lc. output at 110 volts, 400 cycles. By designing for operation at high
speed, it has been possible to produce a machine weighing only 13 lb., with an a.c. output of 360 watts at 0.8 power factor, which is adequate for a doubledeck bus, installation.
Basically, the inverter is a singlearmature double-wound unit, having a six-pole field systetrr. The d.c. winding on the armature is connected to a mutator in the normal manner, and the a.c. winding to three slip rings. A sixpole field system is common to the to windings, and with an armature speed of 8,000 r.p.m., the desired frequency of 400 cycles per sec, is obtained.
The distribution of_ light with fluorescent tubes, as compared with tungsten lamps, has been the subject of much controversy and investigation. and some of the preliminary results which have been obtained by C.A.V., Ltd., are interesting. The accompanying diagrams show the respective lighting intensities at reading level, for a section of a public service vehicle, and the following points are brought out by reference to them:—
(a) Tungsten lighting gives maximum intensity immediately adjacent to the window, with a steady diminution across the seat.
(13) The fluorescent installation gives maximum intensity near the centre of the seat, and so both passengers are equally favoured.
(c) Gangway illumination is appreciably improved with fluorescent lighting; thus the conductor is assisted in his collection of fares and ticket issuing. This is an advantage that will commend itself to all operators.
It is also of interest to note that the current consumption from the battery was approximately the same for both systems.