Susumu Tadakuma’s innovative high-power converters and motor drives have helped realize the potential of high-speed transportation systems and improved factory processes. Tadakuma overcame the limitations of noncirculating current cycloconverters with a circulating-current control that was less bulky and more cost effective. Allowing precise current control at high speeds, this drive enabled the creation of Japan’s magnetic levitation railway system (MAGLEV). He also developed a new induction-motor traction drive system for Japan’s bullet train that was powered by a pulse-width-modulation rectifier/inverter that incorporated gate turn-off thyristors. This breakthrough replaced the bulky dc motor drives that used traditional thyristors based on delay-angle or firing-angle control. He also created the first industrial commutatorless motor drives that were applied in steel and paper mills and in electric vehicle drives.
An IEEE Life Fellow, Tadakuma is a professor (retired) with Chiba Institute of Technology, Chiba, Japan.