An air core pulse transformer with a linearly integrated primary capacitor bank to achieve ultrafast charging

Abstract

An air core transformer that linearly integrates a capacitor bank as well as a selfclosing switch into the primary winding (LIP) was designed to achieve ultrafast charging. Limiting stray inductance and maximizing the uncoupled dual resonance of the primary and secondary windings were the primary design criteria. To show this concept, two transformers with an uncoupled resonant frequency of approximately 8 MHz were designed for a low voltage output (several kV) and a high voltage output (>100 kV). The design was simulated in a Multisim discrete circuit model and a CST hybrid model which includes the transformer's 3-D structure as well as discrete circuit components. The discrete output (voltage and current) as well as the distributed parameters (electric field distribution and surface current density distribution) for the transformer were obtained. These designs were validated by experimental results. We show that their respective resonance characteristic and voltage gain are accurately predicted by the simulated values, demonstrating the design procedure is valid for both low voltage and high voltage applications. For the high voltage transformer, it has a voltage gain of 3-4. The maximum output voltage was tested up to 120 kV. A charging pulse with a rise time of less than 100 ns was obtained.