Electric Railways - Direct Current

In both cities, however, electrification was preceded by widening in two senses, multiple tracking of the busiest routes, and physical increase of clearances to accommodate wider, higher capacity cars seating five people across (in twos and threes separated by an aisle) where previous cars had accommodated only four.

Both cities' electrifications were conceived before the First World War and planned in depth through and in spite of it, although the war delayed implementation. Both cities used a 1500 V dc supply, fed by overhead catenary, and substantial fleets of converted ex steam stock (particularly Melbourne). Thereafter, the technologies were as divergent as chalk and cheese.

Melbourne ran its first electric trains in 1919. Its electric railway technology was recommended by Charles Merz (an Englishman) and its equipment, especially on the trains, was substantially American from General Electric. The Victorian Railways' engineers devised an ingenious control system based on the 600/750 V dc practice of American 'interurban' railway (a heavy, high speed rural tram car) with four inter-urban type motors (basically of 750 V but insulated for 1500 V) per car in two series pairs. The interurban standard 750 V dc electro mechanical contactor control gear and air compressor were used, ingeniously fed by a 1500/750 V rotary voltage divider. The same rather alarming voltage existed in the inter-car train control lines and series connected roof lamps. This application of off the shelf equipment was innovative, clever and (it is believed) wholly Australian. A quaint feature of Melbourne trains was that like their parent interurbans, they never had batteries and almost until the 1980s, their tail lamps were lit by kerosene. Meanwhile, the cable trams had been switched to battery-powered electric light!

The power system was generated by the railway at the old Newport power house (only recently demolished) and distributed at 25 Hz, often on the over track masts; rotary converter sub-stations were applied on the 'little and often' theory. The trains were timber bodied and in comparison with Sydney's somewhat under-powered until as late as 1972. This led to trouble in the 1980s as the increasing power demands of the trains outstripped the capacity of the distribution system. The trains which had 43 per cent of their axles motored were, however, probably more reliable in respect of electrical equipment than their Sydney contemporaries.

The Sydney system was conceived by Dr. J. J. C. Bradfield on a rather more ambitious scale. The first electric train ran in 1926 and by 1932 the system included as well as the major electrified ex steam suburban lines, a city railway with a circle line (truncated until after the war); a link across the Harbour Bridge; the largest complex of flying junctions (grade separation trackage) in the world at the time; built-in provision for new lines to the Eastern, Western, Southern and Northern coastal suburbs (of which only the first was built) and near complete automatic signalling with power interlockings when many Melbourne lines retained mechanical equipment. Sydney too, generated its power in a railway powerhouse (White Bay) and distributed at 25 Hz, but its electrical loads were higher and it built consistently larger and somewhat wider spaced sub stations.

Australian Academy of Technological Sciences and Engineering