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D.C. POWER STATIONS
The energy to run a tramway in the U.K. usually came from coal although by 1920 there were experiments in oil firing. Stations in other countries sometimes used diesel engines to drive the generators.
Typically a coal fired generating station would have a number of boilers generating steam to drive either reciprocating steam engines or, very occasionally, turbines. These would be mechanically coupled to dynamos which generated electricity for the tramway and sometimes for more general industrial and domestic uses.
In practice, the power station was a good deal more complex than this.
The description which follows is of a typical coal fired power station for a small provincial British tramway system, based on the station of the Bath Electric Tramways (BET) at Walcot, Bath.
The floor plan shows the boiler house, generating hall, tram stabling and repair workshops all fitted into a relatively compact site alongside the river (which supplied cooling water).
To ensure utmost reliability when a boiler, engine or dynamo was shut down for maintenance, each of these major items was triplicated. This also allowed equipment to be started and stopped as the load varied, thereby reducing the inefficiency of running large machines for long periods on very low loads.
The three main generators were rated at 200 kW each. In addition, there was a small auxilliary generating set rated at 75 kW for supplying depot lighting and other facilities when the main generators were shut down. There were also two 15 kW boosters (not shown) to overcome the voltage lost in long feeders to distant sections of route.
The repair shops were capable of dealing with almost any problem which arose. Tram motors could be lowered directly from the vehicle through a trap into the workshops below.
In the pages which follow, the components of the power station are dealt with in detail....
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