A closer look to conventional hydraulic ship actuator systems and the convenience of shifting to (possibly) all-electric drives

This paper analyzes feasibility and convenience of transition from conventional oleodynamic power drives onboard liner/military ships to all-electric drives (AEDs). Classical hydrostatic transmission drives (HTDs) are cumbersome, heavy, complex, low efficiency systems and need intensive maintenance for oil leakages and filters, but feature high torque/thrust density and reliability. Alternative AEDs feature compactness, high efficiency, modularity, and better electronic control by inverter, but advantages and limits must be evaluated. High torque/redundancy requirements need special designs. Two plant types are analyzed: mooring/anchor capstans and rudder steering gears. Commercial AEDs are considered, besides a new permanent-magnet linear motor under development suitable for rudder/fin direct drive application. HTDs and AEDs are compared on the basis of encumbrance, weight, efficiency, redundancy, maintenance, complexity, modularity, reliability. Advantages of using AEDs are outlined.