Development of a Multilevel Controllable Modular Pulsed Magnetic Field Generator

Abstract

This article presents a multilevel modular pulsed generator for inductive-load driving, featuring commutation-assisted energy recovery and waveform programmability. Each stage comprises a discharge unit and a commutation unit, where the commutation path returns the residual energy of the inductive load to the corresponding storage capacitor, enabling staged energy reutilization. By coordinating the switching sequence among stages, the generator provides programmable control of the coil current, including pulse amplitude and pulsewidth, as well as the multiple levels of the current change rate (d<inline-formula> <tex-math notation="LaTeX">$i$ </tex-math></inline-formula>/d<inline-formula> <tex-math notation="LaTeX">$t$ </tex-math></inline-formula>) along the waveform. A three-stage laboratory prototype is built to validate the proposed topology and control strategy. The effects of switch conduction time and discharge voltage on the energy-recovery performance are experimentally characterized, and the pulse shaping capability is evaluated on an inductive coil load. Results show that, with a conduction time ranging from 25 to <inline-formula> <tex-math notation="LaTeX">$100~\mu $ </tex-math></inline-formula>s, the measured energy-recovery efficiency varies from 45.01% to 82.27%. In addition, limiting the pulse tail duration to within <inline-formula> <tex-math notation="LaTeX">$200~\mu $ </tex-math></inline-formula>s reduces internal losses and improves energy utilization. Staircase pulses with piecewise-programmable d<inline-formula> <tex-math notation="LaTeX">$i$ </tex-math></inline-formula>/d<inline-formula> <tex-math notation="LaTeX">$t$ </tex-math></inline-formula> levels and corresponding voltage features are demonstrated. The results confirm waveform-wide pulse shaping enabled by sequential activation of the circuit modules.