Technology Development for Electric Ship Propulsion

An overview of the current and projected state of the art for marine electric drive systems is presented, together with an assessment of relative development risk. The objectives for pursuing development of electric drive are arrangement flexibility, control-lability, variable reduction ratio, reliability, and provision of ship's service power from the main bus. Several new technologies permit achievement of these objectives without weight, cost, and efficiency penalities. Four technology areas show promise of significantly increasing electric drive power density, including forced gas cooling, direct water cooling, permanent magnet exitation, and superconducting electromagnet excitation. Each of these technologies is examined to display the essential machine characteristics, the areas of technical risk, and the degree of anticipated weight and volume reduction for a typical application. System considerations for propulsion systems utilizing the various types of machine technologies are also discussed.