Electric Propulsion Motor Development for Commercial Ships in Japan

Three motors that were developed for icebreakers epitomize the history of electric propulsion motor development in Japan. Direct current (dc) motors were developed for Fuji, commissioned in 1965, and Shirase I, commissioned in 1982, and induction motors were developed for Shirase II, commissioned in 2009. Three separate groups in Japan are actively developing superconducting motors for marine propulsion. The Tokyo University of Marine Science and Technology group developed the world´s first axial-gap coreless high-temperature superconducting motor (HTS) with a 100-kW output for a liquid neon thermosiphon cooled superconducting machine over a period from 2004 to 2007. The IHI Corporation group has developed four types of axial-type HTS motors since 2004. Using a cooling system based on liquid nitrogen, they achieved the world´s highest output at 365 kW in 2007. The Kawasaki Heavy Industries group has been developing radial-type HTS motors since 2007. In 2010, the group developed a 1-MW motor that achieved an output of 450 kW. In 2013, the group also developed a 3-MW motor that achieved an output of 3 MW. Furthermore, the group has developed key hardware technologies for a 20-MW motor.