Defining and achieving rated shaft power in electric propulsion systems at sea trials for new U.S. Navy ships

Abstract

New ship designs are required to validate their performance at sea trials to contractually it meets or exceeds its specified requirements. Two of the most important requirements to be contractually verified for a new ship design are its specified ship speed and rated shaft power of the propulsion system as installed in the ship. However, propulsion systems of new ship designs typically do not achieve their defined rated power at sea trials for various reasons unrelated to the propulsion system itself. The recent revival of electric propulsion systems aboard U.S. Navy ships has necessitated a refinement on how to define and achieve rated shaft power at sea trials because the established approach is based on mechanical propulsion systems rather than electric propulsion systems. This paper addresses the differences between electric and mechanical propulsion systems in defining and realistically achieving rated shaft power at sea trials for new ships. Accordingly, this paper reviews the U.S. Navy policy for establishing rated shaft power at sea trials and examines how these requirements now apply to ships with electric propulsion systems. The paper concludes with proposing an updated method to formally define and realistically achieve rated shaft power at sea trials via either DC or AC electric propulsion systems in full or partial configurations for new U.S. Navy ships.