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.
['Toshiyuki Yanamoto', 'Mitsuru Izumi', 'Minoru Yokoyama', 'Katsuya Umemoto']
Electric Propulsion Motor Development for Commercial Ships in Japan