This paper analyzes a different approach for actuation of shipboard loads such as rudders, stabilizing fins, or other linear drives, which are usually powered by oil-fed actuators. Hydrostatic transmissions are classically used when the highest torques/forces with low speeds are demanded. However, the oil used as force-transmission fluid is troublesome due to environmental issues. Oil production, use, and final disposal is costly and presents environmental risks. Also the maintenance onboard ship is intensive and hazardous for the operators. A full electric solutions is ulteriorly studied in this paper, based on a prototyped linear machine using permanent magnets and inverter feeding. Copper, friction, and iron losses are the main limiting factors in developing the required thrust at low speed, which is, ultimately, the main obstacle to a gear-less or direct-drive full-electric application. This paper shows incremental work on the prototype, through a dedicated circuit model accounting for all the machine losses and providing an affordable model of machine overall efficiency. The model will be used in further works to asses the machine performances in typical onboard service duties.
