Overview
Where electric transmission is used, the engine is usually a single-shaft machine in which one turbine drives both the compressor and the output shaft.
With mechanical transmission, the power turbine must be capable of starting from rest, so a more complex arrangement is necessary. One option is a two-shaft machine, with separate turbines to drive the compressor and the output shaft. Another is to use a separate gas generator, which may be of either rotary or piston type.
Read more about this topic: Gas Turbine Locomotive