Realization of High-Stability Flat-Top Pulsed Magnetic Fields by a Bypass Circuit of IGBTs in the Active Region

A high-stability flat-top pulsed magnetic field (FTPMF) is strongly needed for some scientific studies, such as nuclear magnetic resonance and specific heat measurement. This paper presents a new linear flat-top regulation bypass circuit to generate a high-stability FTPMF based on a battery bank power supply. The bypass circuit consists of insulated-gate bipolar transistors (IGBTs) in parallel that operate in the active region and are free of switch ripples. To achieve precise control of the IGBT current, the influence of the Miller effect and the nonlinearity of the IGBT's transfer characteristic are studied in detail. Then, a dual-feedback loop is designed and analyzed. A prototype consisting of a 1000 V/30 kA battery bank and a bypass circuit of 1700 V/3600 A IGBTs is developed. An FTPMF with a field/duration of 23.370 T/100 ms and a stability of 64.2 ppm has been achieved.