What is the speed of the turbo-alternators?

Turbo-alternators, which are essentially high-speed alternators driven by steam or gas turbines, generally operate at speeds correlating to the standard electrical power frequencies of 50 or 60 Hz. However, the specific speed of a turbo-alternator is largely dependent on the design of both the turbine that drives it and the electrical system it serves.

For a generator operating in a system with a frequency of 50 Hz, the common rotational speeds are 3,000 RPM (Revolutions Per Minute) for a 2-pole generator, and 1,500 RPM for a 4-pole generator. In a 60 Hz electrical system, the speeds typically are 3,600 RPM for 2-pole generators, and 1,800 RPM for 4-pole generators. These speeds allow the alternator to directly produce electricity at the desired frequency without the need for additional conversion.

The choice between using a 2-pole generator or a 4-pole generator (hence the variation in speed) depends on several factors including the physical size and power output of the unit, as well as the specific requirements of the application it is being used for. Turbo-alternators can vary widely in size, from small units producing only a few hundred kilowatts, to large industrial units designed for power generation that produce hundreds of megawatts.