Additionally, experimental electric tram operations powered by small generators had been in intermittent use in Sydney since 1890.
Ultimo Power Station boasted a mixture of equipment, initially consisting of American-made steam engines coupled to dynamoelectric machines (direct current generators).
The original generating plant at Ultimo consisted of four cross-compound, reciprocating steam engines supplied by E. P. Allis & Co. of Milwaukee, Wisconsin, each rated at 1250 horsepower (hp) and running at 100 rpm.
Each steam engine was coupled to a multi-pole, compound-wound dynamo supplied by the General Electric Company (GE) of Schenectady, New York.
Each dynamo (generator) was rated at 849.75 kW (1,139.53 hp) at 550 volts direct current (1545 amperes) and could be overloaded by up to 50 percent to satisfy peak demand.
To cater to the growing demand of the electrified tram network, the engines were frequently run at 1,600 hp (1,200 kW).
Steam was initially supplied by 14 horizontal multi-tubular under-fired (Colonial) fire tube boilers by G. & C. Hoskins, Sydney.
Only twelve boilers were needed to provide sufficient steam for full-capacity power generation, leaving two in reserve.
[1][full citation needed] The George St tram line experienced serious voltage drop problems, especially at the Circular Quay end.
Each alternator was powered by an Allis Reynolds vertical cross compound condensing reciprocating steam engine rated at 2500 hp at 75 rpm.
Steam pressure was 160 pounds per square inch (1,100 kPa) and superheaters gave a final temperature of 466 °F (241 °C).
Provision (foundations) was made for the addition of three more reciprocating steam engine-alternator sets, but this was abandoned in favour of turbo-alternators.
When the DC section was finally closed down in 1920, the remaining horizontal engines were replaced with two more 2.4 MW Dick-Kerr 50 Hz turbo alternators and numbered 3 & 4.
They had a balanced draught system and were fitted with chain grate stokers, and their flue gasses were taken away by two new short steel stacks.
In 1949, their space was taken by a single 18.75 MW unit manufactured by English Electric (Australia), which had been alternator No.4 at White Bay Power Station since 1924.
The 1500 V DC heavy rail electrification commenced operation in 1926 and also initially used high capacity rotary converters.