Power take-in (PTI)

Power take-in (PTI) is a mode where an electric machine on the propulsion shaft, often the same machine that runs as a shaft generator, draws electrical power from the ship’s main bus to add torque to the propeller. It boosts propulsion at peak demand, allowing a smaller main engine, and can take over fully for slow-speed or emergency take-home propulsion if the main engine is down. PTI is the converse of PTO, where the shaft machine generates power. In a power-take-off / power-take-in / power-take-home (PTO/PTI/PTH) arrangement, the same motor-generator and frequency converter handle both directions of power flow.