Magnetic Field Coil Power Supply Using a Flywheel Generator With a Planetary Gear and a Low-Rated Inverter

High-power pulsed magnet systems often require energy storage to reduce the burden on the electrical grid. Flywheel generators are well suited for medium-duration discharges and have been used in fusion experiments. Conventional systems using thyristor rectifiers suffer from output ripple and require bulky transformers, while PWM-based converters produce switching noise and scale poorly at high power levels. To overcome these issues, we previously applied a diode-rectified flywheel generator with a DC–DC converter for the PLATO tokamak. While effective in noise suppression, the direct-coupled configuration led to voltage drop and limited flat-top duration. This study proposes a new flywheel generator architecture that uses a planetary gear mechanism to connect the flywheel and generator shafts. This mechanically enabling constant-speed generator operation despite RPM reduction. Experimental results demonstrate voltage stabilization, reduced electromagnetic noise, and a significant reduction in converter size. These features make the proposed system a promising solution for long-duration, low-noise magnet power supplies in fusion devices.