Shaft generators

Shaft generators are becoming an increasingly popular solution for new vessels.
My question is: can a shaft generator operate throughout the entire M/E RPM range?
What are the limitations?

Hello @Oswald.Alving indeed shaft generators are becoming a popular solution and can increase the energy efficiency of ships.
They cannot operate at the entire M/E RPM range, the usually have a lower and upper RPM limit that they can operate and this is defined by the shaft generator maker in collaboration with the Main Engine maker.

The lower RPM limit is typically set to prevent the generator from producing insufficient power. If the propeller shaft speed falls below the minimum RPM limit, the generator may not be able to produce enough power to meet the ship’s electrical demands.
This can result in a loss of power to critical systems, such as navigation or communication equipment, and can potentially compromise the safety of the vessel.

The upper RPM limit is set to prevent the generator from overloading and damaging the system. If the propeller shaft speed exceeds the maximum RPM limit, the generator may produce an excessive amount of power, which can lead to overheating and damage to the generator or other electrical components on the ship.

This is why the shaft generators are usually disengaged when they reach the lower or upper RPM limits and the standby generators must start.