Advanced AC to AC power conversion techniques for naval ship propulsion drives

Recent advances in magnetic materials, cooling and design allow simplification of compact propulsion motor drives for naval ship drives. The paper shows the advantage of direct water cooling with integrated gate commutated thyristor (IGCT) variable speed drives to lower the overall weight as well as the manufacturing cost of these propulsion plants. The drives can be installed as a hybrid electric drive or as an auxiliary propulsion plant connected to the main reduction gear on a surface ship. A trade study shows the advantage of going to a medium voltage (4160 to 7000 Volts AC) on the propulsion machine and power electronic drive when the horsepower ratings exceed 2500 HP. A preferred circuit is an AC Resonant Link with an input total harmonic distortion of 1.5%.