Complex sentence: A speed increaser stepped up the 40 r/min of the turbine to drive an 1800 r/min generator, with the power output of the machine regulated by pitching the rotor blades.
Split into simpler sentences: A speed increaser stepped up the 40 r/min of the turbine to drive an 1800 r/min generator. The power output of the machine was regulated by pitching the rotor blades.