Northfleet Series Electric Tramway

One the earliest electric tramways was opened at Northfleet in Kent in the Spring of 1889, it pioneered a different method of electric transmission to earlier systems (although had been already tried in the United States). The Northfleet system was a series electric instead of parallel like other tramways. With a parallel electric system the electric current that passes through a motor (or any other electric device like a lamp) does not pass through any other [1]. With a series electric the whole current of the system passes through the devices using it. One advantage of this system was that a much smaller current could be applied as parallel systems needed larger current to counter the dropping off effect the further one got from the generating dynamo.

Information
Built:	1889
Builder:	Falcon Engine & Car Works
Motor:	Elwell & Parker electric motor (200v)
Power:	15 hp (11 kW)

The problem for engineers was how to run multiple motors in series at the same time. The solution was to divide the conductor into segments (in the Northfleet case about six and half metres long [2]) and for the tram to close the circuit as required as it passes over the segments. The Northfleet system used a buried conductor underneath one of the running rails with a slot for an "arrow" which opened the circuit at successive points by opening two "spring jacks". A dynamo on board the tram was used to maintain a steady supply to the motor which otherwise would have been subject to the circuit being opened and closed by other tramcars.

The tramway, which replaced an existing horse drawn tram, was narrow gauge (1067mm). This required special motors to be built for it. The Northfleet tram apparently worked well though was no more than an experiment, though a bold one which attracted a good deal of interest from engineers.

By the end of 1890 the tram had returned to living breathing horse power, though a more conventional electric tram system was started in 1901.

Northfleet tram [3]

Front of tram and detail of the motor, the narrowness of the motor can be seen [3]

Cross section of rail and conductor [1]

[1] "The Northfleet Series Electric Tramway", Nature (May 9 1889) p. 39
[2] Robert J Harley, North Kent Tramways (Middleton Press, 1994) Fig. 60
[3] "The Northfleet Series Electric Tramway - Dynamo and Cars", The Engineer (March 15 1889) p. 219