Study on Resonance Phenomenon Caused by Voltage Fluctuation of Power Supply in JT-60SA EF Coil

For the large research Tokamak JT-60SA, evaluating the withstand voltage between conductors is one of the most critical factors for the coil design. The power supply feeding the coil injects a wide spectrum of frequency components. The transient response and resonance phenomena induce a non-uniform voltage distribution in the coil. The transiently concentrated voltage can cause the insulation breakdown between conductors, and JT-60SA may not be able to operate safely. This study conducted an impulse test to evaluate the withstand voltage between adjacent conductors for an equilibrium field (EF) coil. The actual power supply voltage for the EF coil was measured to investigate the ramp rate (dv/dt) and frequency spectrum. In addition, based on the results of a resonance test of the EF dummy coil, a circuit simulation model for the EF coil was developed to evaluate the effect of the transient response and resonance phenomenon on the voltage in the coil. The results of this study provide fundamental data that can be used to ensure that the EF coil does not cause insulation breakdown.